WorldWideScience

Sample records for depositional remanent magnetization

  1. Magnetic fabric and remanent magnetization of pyroclastic surge deposits from Vulcano (Aeolian Islands, Italy)

    Science.gov (United States)

    Zanella, E.; De Astis, G.; Dellino, P.; Lanza, R.; La Volpe, L.

    1999-11-01

    Tufi di Grotte dei Rossi Inferiori are unwelded, fine-grained pyroclastic deposits of hydromagmatic origin emplaced between 21 and 11-8.6 ka at Vulcano (Aeolian Islands, Italy) by deposition through surges spreading laterally from inside the La Fossa caldera. In this study, the deposit's magnetic properties were investigated and interpreted in terms of eruptive and emplacement dynamics. Rock-magnetism data were supplemented by grain size and textural characteristic analyses as well as scanning electron microscope (SEM) investigations. Curie point measurements, isothermal remanent magnetization and microprobe analyses showed that magnetization is carried by low-Ti titanomagnetite. The size of the grains ranges from about 20 to 300 micrometres, their shape from equidimensional to highly elongated. The magnetic fabric is typical of fine-grained pyroclastics. Foliation is well developed and in most sites lineation is directed towards the source area of the La Fossa caldera. The remanent magnetization consists of two components whose blocking temperature spectra partially overlap. The direction of the low-temperature component is close to that of the axial dipole, and consistent with the palaeosecular variation curve for the Aeolian Islands. The high-temperature component is systematically shallowed and close to the direction of the magnetic lineation. The overall results suggest that the high-temperature component was acquired before, and the low-temperature component after, the actual deposition of grains. Immediately after eruption, the grains cooled and moved as free particles in the turbulent cloud during the expansion of the surge flows. Those particles with high blocking temperatures acquired a thermal remanence. They were then deposited and shear at the very base of the flow oriented them and imprinted the rock's fabric and high-temperature magnetization component. Volcanological and magnetic data suggest turbulent transportation and traction deposition of

  2. Remanent magnetism at Mars

    Science.gov (United States)

    Curtis, S. A.; Ness, N. F.

    1988-01-01

    It is shown that a strong case can be made for an intrinsic magnetic field of dynamo origin for Mars earlier in its history. The typical equatorial magnetic field intensity would have been equal to about 0.01-0.1 gauss. The earlier dynamo activity is no longer extant, but a significant remanent magnetic field may exist. A highly non-dipole magnetic field could result from the remanent magnetization of the surface. Remanent magnetization may thus play an important role in the Mars solar wind interactions, in contrast to Venus with its surface temperatures above the Curie point. The anomalous characteristics of Mars'solar wind interaction compared to that of Venus may be explicable on this basis.

  3. Magnetic remanence of hematite-bearing murals

    Science.gov (United States)

    Lanza, R.; Zanella, E.; Saudino, S.

    2009-12-01

    We report on a series of experiments designed to test the ability of hematite-bearing colors to record the direction of the ambient magnetic field. Plasterboards accurately oriented with respect to the Earth's magnetic field were painted with red tempera colors prepared with hematite pigments. Magnetic measurements indicate that the color film retains a remanent magnetization and acquires a well developed magnetic fabric. The remanence direction is close to, yet slightly deviated from the Earth's magnetic field. The deviation is interpreted to result from preferential alignment of the pigment grains parallel to the plasterboard surface and depends on both its orientation with respect to magnetic north and the degree of magnetic anisotropy of the color film, which in turn varies according to the pigment used. Investigation of the magnetic remanence of murals may complement archaeomagnetic information derived from traditional materials such as baked and fired structures.

  4. The magnetic properties of the hollow cylindrical ideal remanence magnet

    DEFF Research Database (Denmark)

    Bjørk, Rasmus

    2016-01-01

    We consider the magnetic properties of the hollow cylindrical ideal remanence magnet. This magnet is the cylindrical permanent magnet that generates a uniform field in the cylinder bore, using the least amount of magnetic energy to do so. The remanence distribution of this magnet is derived...... and the generated field is compared to that of a Halbach cylinder of equal dimensions. The ideal remanence magnet is shown in most cases to generate a significantly lower field than the equivalent Halbach cylinder, although the field is generated with higher efficiency. The most efficient Halbach cylinder is shown...... to generate a field exactly twice as large as the equivalent ideal remanence magnet....

  5. The magnetic properties of the hollow cylindrical ideal remanence magnet

    CERN Document Server

    Bjørk, R

    2016-01-01

    We consider the magnetic properties of the hollow cylindrical ideal remanence magnet. This magnet is the cylindrical permanent magnet that generates a uniform field in the cylinder bore, using the least amount of magnetic energy to do so. The remanence distribution of this magnet is derived and the generated field is compared to that of a Halbach cylinder of equal dimensions. The ideal remanence magnet is shown in most cases to generate a significantly lower field than the equivalent Halbach cylinder, although the field is generated with higher efficiency. The most efficient Halbach cylinder is shown to generate a field exactly twice as large as the equivalent ideal remanence magnet.

  6. Induced remanent magnetization of social insects

    Energy Technology Data Exchange (ETDEWEB)

    Wajnberg, E.; Cernicchiaro, G.; Acosta-Avalos, D.; El-Jaick, L.J.; Esquivel, D.M.S. E-mail: darci@cbpf.br

    2001-05-01

    The induced remanent magnetization (IRM) of honeybees Apis mellifera and ants as Pachycondyla marginata, a migratory species, and Solenopsis sp., a fire ant, was obtained using a SQUID magnetometer from 10 to 300 K. An anomalous sharp change of the remanent magnetization is observed at 67{+-}0.2 K for migratory ants. The IRM at room temperature indicates the presence of at least 10 times lower concentration of magnetic material in the whole fire ant as compared to the migratory ant abdomen (0.22{+-}0.33x10{sup -6} emu/ant, and 2.8{+-}1.2x10{sup -6} emu/abdomen, respectively). Our results in honeybee abdomen (4.6{+-}0.9x10{sup -6} emu/abdomen) agree with other reported values. IRM at room temperature in ants and honeybees indicates the presence of single domain (SD) or aggregates of magnetite nanoparticles. The loss of remanence from 77 to 300 K can be related to the stable-superparamagnetic (SPM) transition of small particles (less than ca. 30 nm). From these values and considering their estimated volumes an upper limit 10{sup 10} SPM and 10{sup 9} SD or aggregate particles are obtained in these insects.

  7. Magnetic remanent states in antiferromagnetically coupled multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kiselev, N.S., E-mail: m.kyselov@ifw-dresden.d [IFW Dresden, Postfach 270116, D-01171 Dresden (Germany); Donetsk Institute for Physics and Technology, 83114 Donetsk (Ukraine); Roessler, U.K.; Bogdanov, A.N. [IFW Dresden, Postfach 270116, D-01171 Dresden (Germany); Hellwig, O. [San Jose Research Center, Hitachi Global Storage Technologies, San Jose, CA 95135 (United States)

    2010-05-15

    In antiferromagnetically coupled multilayers with perpendicular anisotropy unusual multidomain textures can be stabilized due to a close competition between long-range demagnetization fields and short-range interlayer exchange coupling. In particular, the formation and evolution of specific topologically stable planar defects within the antiferromagnetic ground state, i.e. wall-like structures with a ferromagnetic configuration extended over a finite width, explain configurational hysteresis phenomena recently observed in [Co/Pt(Pd)]/Ru and [Co/Pt]/NiO multilayers. Within a phenomenological theory, we have analytically derived the equilibrium sizes of these 'ferroband' defects as functions of the antiferromagnetic exchange, a bias magnetic field, and geometrical parameters of the multilayers. In the magnetic phase diagram, the existence region of the ferrobands mediates between the regions of patterns with sharp antiferromagnetic domain walls and regular arrays of ferromagnetic stripes. The theoretical results are supported by magnetic force microscopy images of the remanent states observed in [Co/Pt]/Ru.

  8. Remanence Properties and Magnetization Reversal Mechanism of Fe Nanowire Arrays

    Institute of Scientific and Technical Information of China (English)

    WANG Jian-Bo; LIU Qing-Fang; XUE De-Sheng; LI Fa-Shen

    2004-01-01

    @@ Remanence properties and magnetization reversal mechanism of Fe nanowire arrays with diameters 16 nm and130nm are studied. Isothermal remanent magnetization curves show that the contribution of irreversible magnetization decreases when the diameter changes from 16nm to 130nm. The remanence coercivities of these nanowires obtained in dc-demagnetization curve are about 2400 Oe and 800 Oe, respectively. The magnetization reversal mechanism is different in these two samples. For the nanowire array with diameter 16nm, both the nucleation and the pinning have effects on magnetization reversal mechanism, and the pinning field (about 2500Oe) is larger than the nucleation field (about 2200 Oe). However, for the nanowire array with diameter 130nm,the magnetization reversal mechanism is dominated by the pinning effect of domain walls.

  9. Influence of remanent magnetization on pitting corrosion in pipeline steel

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J. H. [ESIME Zacatenco, SEPI Electronica Instituto Politecnico Nacional Mexico, D. F. (Mexico); Caleyo, F.; Hallen, J. M. [DIM-ESIQIE, Instituto Politecnico Nacional Mexico D. F. (Mexico); Lopez-Montenegro, A.; Perez-Baruch, E. [Pemex Exploracion y Produccion, Region Sur Villahermosa, Tabasco (Mexico)

    2010-07-01

    Statistical studies performed in Mexico indicate that leakage due to external pitting corrosion is the most likely cause of failure of buried pipelines. When pipelines are inspected with the magnetic flux leakage (MFL) technology, which is routinely used, the magnetization level of every part of the pipeline changes as the MFL tool travels through it. Remanent magnetization stays in the pipeline wall after inspection, at levels that may differ from a point to the next. This paper studies the influence of the magnetic field on pitting corrosion. Experiments were carried out on grade 52 steel under a level of remanent magnetization and other laboratory conditions that imitated the conditions of a pipeline after an MLF inspection. Non-magnetized control samples and magnetized samples were subjected to pitting by immersion in a solution containing chlorine and sulfide ions for seven days, and then inspected with optical microscopy. Results show that the magnetic field in the pipeline wall significantly increases pitting corrosion.

  10. Magnetically Remanent Hydrogels with Colloidal Crosslinkers

    NARCIS (Netherlands)

    van Berkum, S.

    2014-01-01

    Hydrogels are widely used in biomedical applications such as drug delivery and tissue engineering. In this research, the feasibility of a hydrogel with embedded magnetic nanoparticles, also called a ferrogel, for biosensor applications was tested. A pH sensitive poly(acrylic acid) hydrogel was used

  11. Magnetically Remanent Hydrogels with Colloidal Crosslinkers

    NARCIS (Netherlands)

    van Berkum, S.

    2014-01-01

    Hydrogels are widely used in biomedical applications such as drug delivery and tissue engineering. In this research, the feasibility of a hydrogel with embedded magnetic nanoparticles, also called a ferrogel, for biosensor applications was tested. A pH sensitive poly(acrylic acid) hydrogel was used

  12. Optical Writing of Magnetic Properties by Remanent Photostriction.

    Science.gov (United States)

    Iurchuk, V; Schick, D; Bran, J; Colson, D; Forget, A; Halley, D; Koc, A; Reinhardt, M; Kwamen, C; Morley, N A; Bargheer, M; Viret, M; Gumeniuk, R; Schmerber, G; Doudin, B; Kundys, B

    2016-09-02

    We present an optically induced remanent photostriction in BiFeO_{3}, resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO_{3}/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO_{3}. Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.

  13. Optical Writing of Magnetic Properties by Remanent Photostriction

    Science.gov (United States)

    Iurchuk, V.; Schick, D.; Bran, J.; Colson, D.; Forget, A.; Halley, D.; Koc, A.; Reinhardt, M.; Kwamen, C.; Morley, N. A.; Bargheer, M.; Viret, M.; Gumeniuk, R.; Schmerber, G.; Doudin, B.; Kundys, B.

    2016-09-01

    We present an optically induced remanent photostriction in BiFeO3 , resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO3/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO3 . Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.

  14. Remanent and induced contributions of the Earth's magnetization

    Science.gov (United States)

    Vervelidou, Foteini; Lesur, Vincent; Thébault, Erwan; Dyment, Jérôme; Holschneider, Matthias

    2016-04-01

    Inverting the magnetic field of crustal origin for the magnetization distribution that generates it suffers from non-uniqueness. The reason for this is the so-called annihilators, i.e. structures that produce no visible magnetic field outside the sources. Gubbins et al., 2011 uses the complex vector Spherical Harmonics notation in order to separate the Vertical Integrated Magnetization (VIM) distribution into the parts that do and do not contribute to the magnetic field measured in source free regions. We use their formalism and convert a crustal SH model based on the WDMAM into a model for the equivalent magnetization. However, we extend their formalism and assume that the magnetization is confined within a layer of finite thickness. A different thickness is considered for the oceanic crust than for the continental one. It is well known that the large scales of the crustal field are entirely masked by the Earth's main field. Therefore, we complement the WDMAM based magnetization map (SH degrees 16 to 800) with the magnetization map for the large wavelengths (SH degrees 1-15) that was recently derived by Vervelidou and Thébault (2015) from a series of regional statistical analyses of the World Digital Magnetic Anomaly Map. Finally we propose a tentative separation of this magnetization map into induced and remanent contributions on a regional scale. We do so based on the direction of the core magnetic field. We discuss the implications of these results in terms of the tectonic history of the Earth.

  15. Remanence Characteristic of Nanostructure of Hard/Soft Magnetic Multilayered Systems

    Institute of Scientific and Technical Information of China (English)

    HU JingGuo; LIU JiWen; MA YuQiang

    2001-01-01

    The relation between microscopic properties (e.g., layer thickness, easy axis orientation) and the macroscopic magnetic properties such as remanent magnetization of the ferromagnetic multilayer system is investigated based on a simple micromagnet approach. We concentrate on a multilayer design with periodic boundary condition, where alternating soft/hard layers build a nanostructured multilayer. For any easy axis direction in the soft and hard layers a simple explicit expression of remanence of the system has been derived analytically. We lind that the remanence clearly depends on the thickness of the soft magnetic layer and is nearly independent of the thickness of hard magnetic layer.On the other hand, the remanence increases upon reducing the angle enclosed by the saturation magnetization and the easy axis directions of soft magnetic layer. However, it is unsensitive to the easy axis direction of hard magnetic layer,but there exists a maximum remanence for a certain easy axis direction of hard magnetic layer.``

  16. Sedimentation acceleration of remanent iron oxide by magnetic flocculation

    Institute of Scientific and Technical Information of China (English)

    Mathias Stolarski; Christian Eichholz; Benjamin Fuchs; Hermann Nirschl

    2007-01-01

    Sedimentation based processes are widely used in industry to separate particles from a liquid phase. Since the advent of the "Nanoworld"the demand for effective separation technologies has rapidly risen, calling for the development of new separation concepts, one of which lies in hybrid separation using the superposition of a magnetic field for magnetic particles. Possible product portfolio of such separation consists of pigment production, nanomagnetics production for electronics and bio separation. A promising step in that direction is magnetic field enhanced cake filtration, which has by now progressed from batch to continuous operation.In sedimentation processes in a mass force field the settling behaviour of particles strongly depends on physico-chemical properties, concentration and size distribution of the particles. By adjusting the pH, the interparticle forces, in particular the electrostatic repulsion, can be manipulated. For remanent magnetic particles such as magnetite, pre-treatment in a magnetic field could lead to a change of interparticle interactions. By magnetizing the particles apart from van der Waals attraction and electrostatic repulsion, an additional potential is induced, the magnetic attraction, which could easily dominate the other potentials and result in agglomeration in the primary minimum. By sedimentation analysis, a wide spectrum of parameters like pH, magnetic field strength and concentration have been investigated. The results show a strong increase of sedimentation velocity by magnetic flocculation of the raw suspension. This leads to a rise in throughput due to the acceleration of sedimentation kinetics by imparting a non-chemical interaction to the physico-chemical properties in the feed stream of the separation apparatus.

  17. Complex remanent magnetization in the Kızılkaya ignimbrite (central Anatolia): Implication for paleomagnetic directions

    Science.gov (United States)

    Agrò, Alessandro; Zanella, Elena; Le Pennec, Jean-Luc; Temel, Abidin

    2017-04-01

    Pyroclastic flow deposits, known as ash-flow tuffs or ignimbrites, are invaluable materials for paleomagnetic studies, with many applications for geological and tectonic purposes. However, little attention has been paid to evaluating the consistency and reliability of the paleomagnetic data when results are obtained on a single volcanic unit with uneven magnetic mineralogy. In this work we investigate this issue by concentrating on the Kızılkaya ignimbrite, the youngest large-volume unit of the Neogene ignimbrite sequence of the Central Anatolian Volcanic Province in Turkey, bringing evidence of significant magnetic heterogeneities in ignimbrite deposits (magnetic mineralogy, susceptibility, magnetic remanence, coercivity, etc.) and emphasizing the importance of a stratigraphic sampling strategy for this type of volcanic rocks in order to obtain reliable paleomagnetic data. Six sections were sampled at different stratigraphic heights within the devitrified portion of the ignimbrite. Isothermal remanence measurements point to low-Ti titanomagnetite as the main magnetic carrier at all sites; at some sites, the occurrence of oxidized Ti-magnetite and hematite is disclosed. The bulk susceptibility (km) decreases vertically at two out of six sections: its value for the topmost samples is commonly one order of magnitude lower than that of the samples at the base. In most cases, low km values relate to high coercivity of remanence (BCR) values, which range from 25 to > 400 mT, and to low S-ratios (measured at 0.3 T) between 0.28 and 0.99. These data point to the occurrence of oxidized magnetic phases. We therefore consider the km parameter as a reliable proxy to check the ignimbrite oxidation stage and to detect the presence of oxidized Ti-magnetite and hematite within the deposit. The characteristic remanent magnetization is determined after stepwise thermal and AF demagnetization and clearly isolated by principal component analysis at most sites. For these sites, the

  18. Stretched exponential relaxation of viscous remanence and magnetic dating of erratic boulders

    Science.gov (United States)

    Sato, T.; Nakamura, N.; Nagahama, H.; Minoura, K.

    2016-11-01

    Viscous remanence continuously increases with the duration of reorientation of rocks, and the remanence gets partially overprinted in rocks parallel to the Earth's magnetic field. This overprinted viscous remanence is unblocked at a certain temperature that enables the estimation of the time required for the rock to acquire the magnetism, by assuming the exponential law of Néel's single-domain theory. However, previous results of dating the rocks by the exponential law have shown older ages than radiometric or cosmogenic exposure ages. Néel's exponential decay law is applicable to a system whose magnetic grains have an identical relaxation time. However, in real systems, the expected behavior is not usually observed because relaxation times vary for individual grains. Moreover, the variation of viscous remanence with the logarithmic law for a distribution of relaxation times is predicted to be concave downward. Here we found that the stretched exponential law, exp{-(t/τ)1 - n} with 0 ≤ n radiometric age.

  19. The natural remanent magnetizations of the exeter volcanic traps (Permian, Europe)

    NARCIS (Netherlands)

    Zijderveld, J.D.A.

    1967-01-01

    The natural remanent magnetizations of 35 samples from five quarries in the Permian traps from the Exeter region were carefully examined. A considerable number of the samples contained a secondary magnetism, the intensity of which was directly proportional to the susceptibility. This secondary magne

  20. Importance of titanohematite in detrital remanent magnetizations of strata spanning the Cretaceous-Paleogene boundary, Hell Creek region, Montana

    Science.gov (United States)

    Sprain, Courtney J.; Feinberg, Joshua M.; Renne, Paul R.; Jackson, Mike

    2016-03-01

    Intermediate composition titanohematite, Fe2-yTiyO3 with 0.5 ≤ y ≤ 0.7, is seldom the focus of paleomagnetic study and is commonly believed to be rare in nature. While largely overlooked in magnetostratigraphic studies, intermediate titanohematite has been identified as the dominant ferrimagnetic mineral in an array of Late Mesozoic and early Cenozoic Laramide clastic deposits throughout the central United States. Intermediate titanohematite is ferrimagnetic and has similar magnetic properties to titanomagnetite, except its unique self-reversing property. Due to these similarities, and with detrital remanent magnetizations masking its self-reversing nature, intermediate titanohematite is often misidentified in sedimentary deposits. Past studies relied upon nonmagnetic techniques including X-ray diffraction and electron microprobe analysis. While these techniques can identify the presence of intermediate titanohematite, they fail to test whether the mineral is the primary recorder. To facilitate the identification of intermediate titanohematite in sedimentary deposits, we characterize this mineral using low-temperature magnetometry and high-temperature susceptibility experiments, and present a new identification technique based on titanohematite's self-reversing property, for sediments that span the Cretaceous-Paleogene boundary (Hell Creek region, Montana). Results from the self-reversal test indicate that the majority of remanence is held by minerals that become magnetized parallel to an applied field, but that intermediate, self-reversing titanohematite (y = 0.53-0.63) is an important ancillary carrier of remanence. While earlier literature suggests that intermediate titanohematite is rare in nature, reanalysis using specialized rock magnetic techniques may reveal that it is more abundant in the rock record, particularly within depositional basins adjacent to calc-alkaline volcanics, than previously thought.

  1. Experimental modeling of the chemical remanent magnetization and Thellier procedure on titanomagnetite-bearing basalts

    Science.gov (United States)

    Gribov, S. K.; Dolotov, A. V.; Shcherbakov, V. P.

    2017-03-01

    The results of the experimental studies on creating chemical and partial thermal remanent magnetizations (or their combination), which are imparted at the initial stage of the laboratory process of the oxidation of primary magmatic titanomagnetites (Tmts) contained in the rock, are presented. For creating chemical remanent magnetization, the samples of recently erupted Kamchatka basalts were subjected to 200-h annealing in air in the temperature interval from 400 to 500°C under the action of the magnetic field on the order of the Earth's magnetic field. After creation of this magnetization, the laboratory modeling of the Thellier-Coe and Wilson-Burakov paleointensity determination procedures was conducted on these samples. It is shown that when the primary magnetization is chemical, created at the initial stage of oxidation, and the paleointensity determined by these techniques is underestimated by 15-20% relative to its true values.

  2. Remanent Magnetization: Signature of Many-Body Localization in Quantum Antiferromagnets

    Science.gov (United States)

    Ros, V.; Müller, M.

    2017-06-01

    We study the remanent magnetization in antiferromagnetic, many-body localized quantum spin chains, initialized in a fully magnetized state. Its long time limit is an order parameter for the localization transition, which is readily accessible by standard experimental probes in magnets. We analytically calculate its value in the strong-disorder regime exploiting the explicit construction of quasilocal conserved quantities of the localized phase. We discuss analogies in cold atomic systems.

  3. REMANENCE MEASUREMENTS ON INDIVIDUAL MAGNETOTACTIC BACTERIA USING A PULSED MAGNETIC-FIELD

    NARCIS (Netherlands)

    PENNINGA, Ietje; Waard , de Hendrik; MOSKOWITZ, BM; BAZYLINSKI, DA; FRANKEL, RB

    1995-01-01

    We describe pulsed-magnetic-field remanence measurements of individual, killed, undisrupted cells of three different types of magnetotactic bacteria. The measurement technique involved the observation of aligned, individual magnetotactic bacteria with a light microscope as they were subjected to mag

  4. Electron holography on remanent magnetization distribution of melt-spun Nd-Fe-B magnets.

    Science.gov (United States)

    Park, Young-Gil; Shindo, Daisuke

    2004-01-01

    Microstructures and magnetic domain structures of melt-spun Nd-Fe-B permanent magnets were investigated in detail by analytical electron microscopy and electron holography. While the crystal orientation of matrix Nd2Fe14B grains was analyzed by nanobeam electron diffraction, precipitates of a few tens of nanometers at grain boundaries were identified to be alpha-Fe by energy-dispersive X-ray spectroscopy. The detailed magnetization distribution in Nd2Fe14B grains and at their boundaries was visualized by electron holography. Ex situ experimentation with an electromagnet revealed that the domain walls in the demagnetized state and remanent states were pinned at grain boundaries, and Fe precipitates at the grain boundary were situated at the center of the closure domain.

  5. Remanent magnetization of a 'paramagnetic' composition in the ilmenite-hematite solid solution stress

    Science.gov (United States)

    Lawson, C. A.; Nord, G. L., Jr.

    1984-01-01

    In the ilmenite-hematite solid solution series, compositions more ilmenite-rich than Ilm(73)Hem(27) are classically thought to be paramagnetic at room temperature. Ilm(80)Hem(20) samples have nevertheless been synthesized that acquire hard saturation remanent and thermoremanent moments. From analysis of AC demagnetization data, the source of the measured remanence is believed to be a single-domain (SD) like material within the IlM(80)Hem(20) grains themselves. On the basis of transmission electron microscope observations, it is suggested that transformation-induced domain boundaries, which in part are enriched in hematite component relative to the bulk composition of the grains, could act as the magnetic carrier of the SD-like remanence.

  6. Possible magnetic minerals constituents in the Martian crust and microstructures consistent with large remanent magnetizations

    Science.gov (United States)

    Diaz-Michelena, M.; Laughlin, D.; McHenry, M. E.

    2012-04-01

    Please fill in your abstract text. Mars Global Surveyor (MGS) mission has played a unique role in the mapping of the Martian magnetic field. Thanks to the results and later data analysis of this mission it is known that Mars does not have a global bipolar magnetic field but that the crust presents areas of great magnetization. This fact is only compatible with a large concentration of highly magnetic minerals (magnetite) with a pinned monodomain magnetization [1, 2]. The next MetNet precursor mission (MMPM) aims to place a net of meteorological stations on the surface of Mars. In the first of them (est. 2014), among other payloads, the Spanish Institute of Aerospace Technology (INTA) has developed a miniaturized vector magnetometer with the goal of measuring the thermomagnetic response of the Martian soil around the lander. The work presented here discusses possible microstructures for the magnetic minerals in the Martian crust. The results presented will be focused on the titanomagnetites series [3] solid solution with compositions of: x (Fe2TiO4) - (1-x) (Fe3O4) with 0.30 Wasilewski, and P. Cloutier; Global Distribution of Crustal Magnetism Discovered by the Mars Global Surveyor MAG/ER Experiment. Science 284, 790-793, 1999. 2. G. Kletetschka, P. J. Wasilewski, and P. T. Taylor, "Mineralogy of the sources for magnetic anomalies on mars," Meteor. Plan. Sci., vol. 35, pp. 895-899, 2000. 3. O'Reilly, Rock and Mineral Magnetism, Black& Son Limited, Glasgow, 1984. 4. Adam Wise, Maryanna Saenko, Amanda M. Velázquez, David E. Laughlin, Marina Díaz-Michelena and Michael E. McHenry, Phase Evolution in the Fe3O4-Fe2TiO4 Pseudo-binary System and its Implications for Remanent Magnetization in Martian Minerals, IEEE TRANSACTIONS ON MAGNETICS, VOL. 47, NO. 10, OCTOBER 2011 5. R. Sanz, M. F. Cerdán, A. Wise, M. E. McHenry, and M. Díaz-Michelena, Phase Evolution in the Fe3O4-Fe2TiO4 Pseudo-binary System and its Implications for Remanent Magnetization in Martian Minerals

  7. Advanced UXO Discrimination using Magnetometry: Understanding Remanent Magnetization

    Science.gov (United States)

    2009-09-01

    reaches saturation. On removal of the magnetizing field, domains reform and move back towards their initial position. Because of lattice...Applied Physics, 29, 2313-2319. Davidson, D., W., and R. H. Cole, 1951, Dielectric Relaxation in Glycerol , Propylene Glycol, and n- Propanol: The...magnetizing field, domains reform and move back towards their initial position. The magne- tization that remains after the field is removed is called

  8. The Coercivity - Remanence Tradeoff in Nanocrystalline Permanent Magnets

    Science.gov (United States)

    2001-11-01

    exchange length L,. in Nd2Fe14B is extremely small, around 21 A [ 10]. Further reduction in the magnetic exchange length from its base value is realized...addition of as-yet unidentified elements to the Nd2Fe14B base composition that would serve to both lower the melting point of the eutectic liquid phase

  9. Study of pitting corrosion in line-pipe steel under the influence of remanent magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J.H.; Caleyo, F.; Hallen, J.M. [Instituto Politecnico Nacional (IPN), Zacatenco (Mexico)

    2009-07-01

    The influence of remanent magnetization on pitting corrosion in line-pipe steels is studied. Pitting corrosion experiments have been carried out on samples of an API 5L grade 52 steel under a magnetization level of the same order of magnitude of the remanent magnetization in the pipeline wall after in-line inspection based on magnetic flux leakage. The samples were magnetized using rings of the same grade as the investigated steel. Immediately after magnetization, the investigated samples were subjected to pitting by immersing them in a solution containing dissolved Cl{sup -} and SO{sup 2-}{sub 4} and ions. The pitting experiments were conducted during a seven days period. The pit depth distribution and the maximum pit depth in each sample were recorded and used to conduct extreme value analyses of the pitting process in magnetized and non-magnetized control samples. The statistical assessment of the pitting corrosion data collected during this study shows that the magnetic field reduces the average depth of the pit population and also the extreme pit depth values that can be predicted from the maximum values observed in the magnetized samples in comparison with to the non-magnetized control samples. Scanning electron microscopy observations show that the magnetic field alters the pit morphology by increasing the pit mouth opening. (author)

  10. Study of pitting corrosion in line-pipe steel under the influence of remanent magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J.H.; Caleyo, F.; Hallen, J.M. [Instituto Politecnico Nacional (IPN), Zacatenco (Mexico)

    2009-07-01

    The influence of remanent magnetization on pitting corrosion in line-pipe steels is studied. Pitting corrosion experiments have been carried out on samples of an API 5L grade 52 steel under a magnetization level of the same order of magnitude of the remanent magnetization in the pipeline wall after in-line inspection based on magnetic flux leakage. The samples were magnetized using rings of the same grade as the investigated steel. Immediately after magnetization, the investigated samples were subjected to pitting by immersing them in a solution containing dissolved Cl{sup -} and SO{sup 2-}{sub 4} and ions. The pitting experiments were conducted during a seven days period. The pit depth distribution and the maximum pit depth in each sample were recorded and used to conduct extreme value analyses of the pitting process in magnetized and non-magnetized control samples. The statistical assessment of the pitting corrosion data collected during this study shows that the magnetic field reduces the average depth of the pit population and also the extreme pit depth values that can be predicted from the maximum values observed in the magnetized samples in comparison with to the non-magnetized control samples. Scanning electron microscopy observations show that the magnetic field alters the pit morphology by increasing the pit mouth opening. (author)

  11. Anisotropies of anhysteretic remanence and magnetic susceptibility of marly clays from Central Italy

    Directory of Open Access Journals (Sweden)

    L. Sagnotti

    1994-06-01

    Full Text Available Marly clays from an Upper Pliocene unit at Valle Ricca (Rorne were investigated for their Anisotropy of Anhysteretic Remanence (AAR and Anisotropy of Magnetic Susceptibility (AMS. The study of AAR was accomplished for the first time in ltaly, developing a suitable laboratory technique and adapting a standard statistical procedure. The comparison between anhysteretic remanence and magnetic susceptibility anisotropies discriminates the fabric of the ferromagnetic fraction from that of the paramagnetic matrix of the rock. The separation of fabric components was applied to distinguish subsequent geological processes that affected the total rock fabric. The results indicate that the clayey units are particularly suitable for the empirical investigation of fabric to strain relationship in weakly deformed rocks.

  12. The effect of low-temperature hydrothermal alteration on the remanent magnetization of synthetic titanomagnetites - A case for acquisition of chemical remanent magnetization

    Science.gov (United States)

    Kelso, Paul R.; Banerjee, Subir K.; Worm, Horst-Ulrich

    1991-01-01

    Experiments were performed demonstrating that a chemical remanent magnetization (CRM) can be acquired during the aqueous oxidation of synthetic titanomagnetites (TM40:Fe/2.6/Ti/0.4/O4) by the removal of iron, as it does in the oceanic crust basalts. Results showed that the CRM is acquired along the ambient field direction during oxidation, and that there is no coupling of the CRM and the thermoremanent magnetization. The rate of oxidation was found to be pH-dependent, with the amount of CRM acquired varying inversely with the pH of the oxidizing solution. The reaction produced nascent hydrogen gas. Results support the chemical equation for titanomagnetic oxidation proposed by Worm and Banerjee (1984).

  13. Nonvolatile, reversible electric-field controlled switching of remanent magnetization in multifunctional ferromagnetic/ferroelectric hybrids

    Science.gov (United States)

    Brandlmaier, A.; Geprägs, S.; Woltersdorf, G.; Gross, R.; Goennenwein, S. T. B.

    2011-08-01

    In spin-mechanics, the magnetoelastic coupling in ferromagnetic/ferroelectric hybrid devices is exploited in order to realize an electric-voltage control of magnetization orientation. To this end, different voltage-induced elastic strain states are used to generate different magnetization orientations. In our approach, we take advantage of the hysteretic expansion and contraction of a commercial piezoelectric actuator as a function of electrical voltage to deterministically select one of two electro-remanent elastic strain states. We investigate the resulting magnetic response in a nickel thin film/piezoelectric actuator hybrid device at room temperature, using simultaneous magneto-optical Kerr effect and magnetotransport measurements. The magnetic properties of the hybrid can be consistently described in a macrospin model, i.e., in terms of a single magnetic domain. At zero external magnetic field, the magnetization orientation in the two electro-remanent strain states differs by 15°, which corresponds to a magnetoresistance change of 0.5%. These results demonstrate that the spin-mechanics scheme indeed enables a nonvolatile electrically read- and writable memory bit where the information is encoded in a magnetic property.

  14. Anisotropy of remanent and induced magnetization in hematite ore deformed in torsion

    Science.gov (United States)

    Machek, Matěj; Petrovský, Eduard; Roxerová, Zuzana; Kusbach, Vladimír; Siemes, Heinrich

    2016-04-01

    Induced and remanent magnetization measurements, e.g. shape of hysteresis loops, FORC diagrams and decomposition of isothermal remanent magnetization (IRM) acquisition curves, became routine tools in rock-magnetic measurements, interpreted mostly in terms of composition and grain-size distribution of iron oxides. It is assumed that the substances investigate are with respect to these measurements isotropic and single measurement of one sample is sufficient for interpretation. This assumption is valid for powdered samples, but solid rock samples in general behave anisotropically. In our contribution we report on magnetic measurements of hematite ore samples deformed in torsion, which show significant anisotropy of shape of hysteresis loops and IRM acquisition curves; the degree of anisotropy reflecting the degree of deformation. Samples, measured in different directions, showed different shape of hysteresis loop, from regular, which may be interpreted either as randomly oriented multi-domain grains, or with different degree of distortion (wasp-waistedness), reflecting different distribution of contrasting coercivities. Also decomposition of IRM acquisition curves, measured in different direction, yielded different interpretation in terms of relative contributions of components with different coercivities. The increasing strain is reflected in the strength and orientation of microstructure and crystallographic preferred orientation (CPO). The AMS in deformed samples is not controlled by hematite CPO. It is rather dominated by occurrence of magnetite grains along samples edges parallel to shear plane, probably due to the diffusion of Fe ions from iron jacket, even though samples were shielded by a silver (70)/palladium (30) sleeve of 0.5 mm thickness. We interpret this anisotropy as result of deformation, causing preferred orientation of basal planes of hematite. Moreover, the anisotropy is asymmetric. Our results suggest that, at least in deformed rocks containing

  15. Effects of low-temperature oxidation on natural remanent magnetization of Chinese loess

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This study systematically investigates changes in both compositions and grain-sizes of magnetic minerals in the Chinese loess/paleosol samples (Yichuan, China) during thermal demagnetization processes. Between 100 and 200℃, (1) Hc and Hcr significantly decrease while Mrs and Ms remain stable; (2) concentration of the multi-domain (MD) grains increases while that of superparamagnetic (SP) grains decreases; and (3) there exists the abnormal behavior of the thermal demagnetization in the natural remanent magnetization (NRM). In addition, the corresponding changes in all these parameters are gradually muted with the increase of the pedogenesis degree. The results indicate that the observed alteration probably relates to reducing processes caused by the burning of the organic matter in samples. Before the thermal treatment, the MD grains in loess samples had been partially altered in nature by low-temperature oxidization (LTO). This CRM can be sufficiently attenuated or even removed by the reducing process between 100 and 200℃ during the thermal treatment and has no apparent harmful effects on the characteristic remanent magnetization (ChRM) between 300 and 500℃.

  16. Anisotropy of Anhysteretic Remanent Magnetization: A Tool To Estimate Trm Deviations In Volcanic Rocks

    Science.gov (United States)

    Gattacceca, J.; Rochette, P.

    In order to assess the paleomagnetic direction deviations due to anisotropy in volcanic rocks, we studied the anisotropies of magnetic susceptibility (AMS), of anhysteretic remanent magnetization (AARM) and of thermoremanent magnetization (ATRM) of a set of Miocene pyroclastic rocks from Sardinia (Italy). The main magnetic carrier is pseudo-single domain titanomagnetite. AARM and ATRM were determined with a 3-position measurement scheme. The measurements show that there is no general relation between the degrees of AMS and ATRM (as this relation depends on the ti- tanomagnetite grain size spectrum), while the degree of AARM and ATRM are almost identical. Measuring the AMS is thus nearly irrelevant to quantitatively estimate TRM deviations due to anisotropy in volcanic rocks. Instead, measuring the AARM provides a reliable and relatively fast method to correct paleomagnetic direction deviations in volcanic rocks (inclination shallowing due to horizontal planar fabric in most cases). This is confirmed by a case study on a succession of four welded pyroclastic flows : an apparent paleosecular variation pattern is almost entirely explained by the effect of ATRM.

  17. Magnetic anisotropy in rhyolitic ignimbrite, Snake River Plain: Implications for using remanent magnetism of volcanic rocks for correlation, paleomagnetic studies, and geological reconstructions

    Science.gov (United States)

    Finn, David R.; Coe, Robert S.; Kelly, Henry; Branney, Michael; Knott, Thomas; Reichow, Marc

    2015-06-01

    Individual ignimbrite cooling units in southern Idaho display significant variation of magnetic remanence directions and other magnetic properties. This complicates paleomagnetic correlation. The ignimbrites are intensely welded and exhibit mylonite-like flow banding produced by rheomorphic ductile shear during emplacement, prior to cooling below magnetic blocking temperatures. Glassy vitrophyric lithologies commonly have discrepantly shallow remanence directions rotated closer to the orientation of the subhorizontal shear fabric when compared to the microcrystalline center of the same cooling unit. To investigate this problem, we conducted a detailed paleomagnetic and rock magnetic study of a vertical profile through a single ignimbrite cooling unit and its underlying baked soil. The results demonstrate that large anisotropy of thermal remanent magnetization correlates with large (up to 38°) deflections of the stable remanence direction. Anisotropy of magnetic susceptibility revealed no strong anisotropy. A strong lineation and deflection of the remanence declination suggest that rheomorphic shear above magnetic blocking temperatures is the dominant mechanism controlling the formation of the magnetic fabric, with compaction contributing to a lesser extent. Nucleation and growth of anisotropic fine-grained magnetite in volcanic glass at high temperatures after, and perhaps also during, emplacement is indicated by systematic variation of magnetic properties from the quickly chilled ignimbrite base to the interior. These properties include remanence directions, anisotropy, coercivity, susceptibility, strength of natural remanent magnetization, and dominant unblocking temperature. The microcrystalline ignimbrite center has a magnetic direction that is the same as the underlying baked soil and, therefore, is a more reliable recorder of the paleofield direction than the glassy margins of highly welded ignimbrites.

  18. Anisotropy evolution of nanoparticles under annealing: Benefits of isothermal remanent magnetization simulation

    Science.gov (United States)

    Tournus, Florent; Tamion, Alexandre; Hillion, Arnaud; Dupuis, Véronique

    2016-12-01

    Isothermal remanent magnetization (IRM) combined with Direct current demagnetization (DcD) are powerful tools to qualitatively study the interactions (through the Δm parameter) between magnetic particles in a granular media. For magnetic nanoparticles diluted in a matrix, it is possible to reach a regime where Δm is equal to zero, i.e. where interparticle interactions are negligible: one can then infer the intrinsic properties of nanoparticles through measurements on an assembly, which are analyzed by a combined fit procedure (based on the Stoner-Wohlfarth and Néel models). Here we illustrate the benefits of a quantitative analysis of IRM curves, for Co nanoparticles embedded in amorphous carbon (before and after annealing): while a large anisotropy increase may have been deduced from the other measurements, IRM curves provide an improved characterization of the nanomagnets intrinsic properties, revealing that it is in fact not the case. This shows that IRM curves, which only probe the irreversible switching of nanomagnets, are complementary to widely used low field susceptibility curves.

  19. Effects of grain size distribution on remanence and coercivity of Pr2Fe14B nanocrystalline magnet

    Institute of Scientific and Technical Information of China (English)

    He Shu-Li; Zhang Hong-Wei; Rong Chuan-Bing; Chen Ren-Jie; Shen Bao-Gen

    2005-01-01

    The demagnetization curves of Pr2Fe14B nanocrystalline magnets are calculated using micromagnetic finiteelement method. Samples with three different distributions of grain size are simulated. We find that the remanence enhancement does not depend on grain size distribution but on the mean diameter of grains, and the influence of grain size distribution on coercivity is affected by the strength of intergrain exchange coupling.

  20. Fine-tuning the local symmetry to attain record blocking temperature and magnetic remanence in a single-ion magnet.

    Science.gov (United States)

    Ungur, Liviu; Le Roy, Jennifer J; Korobkov, Ilia; Murugesu, Muralee; Chibotaru, Liviu F

    2014-04-22

    Remanence and coercivity are the basic characteristics of permanent magnets. They are also tightly correlated with the existence of long relaxation times of magnetization in a number of molecular complexes, called accordingly single-molecule magnets (SMMs). Up to now, hysteresis loops with large coercive fields have only been observed in polynuclear metal complexes and metal-radical SMMs. On the contrary, mononuclear complexes, called single-ion magnets (SIM), have shown hysteresis loops of butterfly/phonon bottleneck type, with negligible coercivity, and therefore with much shorter relaxation times of magnetization. A mononuclear Er(III) complex is presented with hysteresis loops having large coercive fields, achieving 7000 Oe at T=1.8 K and field variation as slow as 1 h for the entire cycle. The coercivity persists up to about 5 K, while the hysteresis loops persist to 12 K. Our finding shows that SIMs can be as efficient as polynuclear SMMs, thus opening new perspectives for their applications.

  1. Environmental history of Lake Hovsgul from physical interpretation of remanent magnetization endmember analysis

    Science.gov (United States)

    Kosareva, Lina; Fabian, Karl; Shcherbakov, Valera; Nurgaliev, Danis

    2016-04-01

    The environmental history of Lake Hovsgul (Mongolia) is studied based on magnetic measurements of the core KDP-01. The drill hole reached a maximum depth of 53 m, from which sediment cores with a total length of 48 m were recovered. Coring gaps are due to the applied drilling technology. Following the approach by Heslop and Dillon, 2007, we develop the way of decomposition of the total magnetic fraction of a sample into not virtual but real three distinctive mineralogical components. For this, we first apply the end-member non-negative matrix factorization (NMF) modeling for the unmixing magnetic remanence curves. Having these results in hands, we decompose the hysteresis loops, backfield and strong field thermomagnetic curves into the components which now can be interpreted as certain mineralogical fractions. The likely interpretation of the components obtained is as follows. The soft component is represented by a coarse grained magnetite fraction as it typically results from terrigenous influx via fluvial transport. The second component is presented by a sharply defined magnetite grain size fraction in the 30-100 nm range that in lake environments is related to magnetosome chains of magnetotactic bacteria. It apparently covaries with a diamagnetic mineral, most likely carbonate. This indicates a link to organic authigenic fractions and fits to biogenic magnetite from magnetotactic bacteria. The third component also has a very high coercivity around 85 mT and is identified as a mixture of biogenic and abiotic greigite common in suboxic/anoxic sediments. The results of such the combined study are used to infer information on paleoclimatic and paleogeography conditions around the lake Hovsgul's area for the period of the last million years. A correlation between the outbursts of biogenic magnetite and greigite content with warm periods is found. Within some parts of the core the dominance of greigite contribution into magnetic signal is observed which we link to

  2. Advanced methods of identification of the natural remanent magnetization carriers in meta-basites from Oscar II Land, Western Spitsbergen

    Science.gov (United States)

    Burzyński, Mariusz; Michalski, Krzysztof; Nejbert, Krzysztof; Manby, Geoffrey; Domańska-Siuda, Justyna

    2017-04-01

    In this study, several rock-magnetic experiments were applied to gain a better understanding of composition and origin of Natural Remanent Magnetization (NRM) carriers in selected meta-dolerites and meta-volcanics of Oscar II Land (Western Spitsbergen). To rise the resolution of results, analyses were conducted on "Fe-containing" separated grains and they were combined with "whole-rock" mineralogical and rock-magnetic observations. Standard "whole- rock" magnetic studies were performed including: coercivity spectra measurements using Vibrating Sample Magnetometer (VSM), SIRM (saturation isothermal remanent magnetization) measurements, the three component IRM (Isothermal Remanent Magnetisation) procedures (Lowrie 1990). Additionally, the above experiments were supported by examination of the thin sections (optical/SEM/BSE). After that, investigated meta-basites were subjected to separation process during which seven different groups of grains has been distinguished. Six of them revealed shape and parameters of hysteresis loop characteristic for ferromagnetic phases. Separated magnetic phases were again subjected to rock-magnetic (SIRM/Micromag VSM) and mineralogical (optical/SEM/BSE) analyses. The results point to the presence of low coercivity magnetite/maghemite and pyrrhotite in the meta-dolerites while in the meta-volcanics the occurrence of magnetite/maghemite and hematite was recorded. The results indicated that late to post-Caledonian ferromagnetic minerals are dominant in the studied meta-basites. The investigations also confirmed that Caledonian metamorphic remineralization has completely replaced primary magmatic - Proterozoic/Lower Palaeozoic ferromagnetic carriers in the meta-dolerites. The present study was funded by Leading National Research Centre (KNOW) received by the Centre for Polar Studies for the period 2014-2018 and NSC (Polish National Science Centre) grant number 2011/03/D/ST10/05193.

  3. Quantication of magnetic coercivity components by the analysis of acquisition curves of isothermal remanent magnetisation

    NARCIS (Netherlands)

    Kruiver, Pauline P.; Dekkers, M.J.; Heslop, David

    2002-01-01

    A new method of analysing isothermal remanent magnetisation (IRM) acquisition curves based on cumulative log Gaussian analysis [Robertson and France, Phys. Earth Planet. Inter. 82 (1994) 223-234] is proposed. It is based on the curve fitting of the IRM acquisition curve versus the logarithm of the a

  4. Laboratory chemical remanent magnetization in clay and the filtering of magnetic reversals.

    Science.gov (United States)

    Pozzi, J. P.; Cairanne, G.; Aubourg, C.; Moreau, M. G.

    2003-04-01

    In order to study the mechanisms of remagnetization in sediments we heated clay samples at temperature from 220°C to 250°C in a magnetic field controlled in direction and in intensity and in different physico-chemical conditions. 1- heating in argon atmosphere or in open atmosphere. 2- heating in closed titanium cells or in confined atmosphere. The magnetic mineral present in clay before heating is magnetite. In addition to clay minerals, pyrite is also present in noticeable proportion. The results are summarized as follows: In the samples heated in argon atmosphere, the final magnetic phase is a mixture of magnetite and hematite. In the samples heated in closed cells only magnetite is produced. In both cases, the CRM is in the direction of the field and it is proportional to its intensity. When the sense of the field is reversed during heating, the results are different: two opposite components of magnetization are acquired in both cases : they are separable by AF demagnetization when the clay was heated in argon atmosphere, but they remain impossible to separate when the clay was heated in closed cells. We propose that in the first case, two distinct processes of different time constants cooperate: production of magnetite from pyrite and partial oxidation of magnetite in hematite leading to a final product showing an evolution with time. In the second case, magnetite is produced continuously with a similar coercivity spectrum for the beginning to the end of the reaction. As a consequence, the two opposite components of CRM are not separable. This type of remagnetization constitutes a perfect filter against reversals.

  5. Partial anhysteretic remanent magnetization (pARM) of synthetic single- and multi-domain magnetites and its paleoenvironmental significance

    Institute of Scientific and Technical Information of China (English)

    LIU Qingsong; YU Yongjae; PAN Yongxin; ZHU Rixiang; ZHAO Xixi

    2005-01-01

    In order to isolate magnetic signals carried by single-domain (SD) ferrimagnetic (FM) minerals from multi-domain (MD) FM minerals, we developed a few parameters using partial anhysteretic remanent magnetization (pARM). Because MD fraction contains only soft (easy to be demagnetized) coercivity spectrum, pARM(>20 mT) was sensitive in eliminating MD contributions. Ratio of pARM(5 mT, 10 mT)/pARM(0, 5 mT) is useful in quantifying a relative abundance of mass ratio between SD and MD fractions. These new proxies can quickly characterize the details of grain size distribution of magnetic minerals in paleoclimatic and paleomagnetic studies.

  6. Volcanic ash particles as carriers of remanent magnetization in deep-sea sediments from the Kerguelen Plateau

    Science.gov (United States)

    Heider, Franz; Ko¨rner, Ulrike; Bitschene, Peter

    1993-07-01

    Carbonate sediments from the Kerguelen Plateau (ODP Leg 120) of Eocene to Pliocene age were investigated with rock magnetic, petrographic and geochemical methods to determine the carriers of remanent magnetization. Magnetic methods showed that the major magnetic minerals were titanomagnetites slightly larger than single domain particles. Submicrometre to micrometre-size grains of titanomagnetite were identified as inclusions in volcanic glass particles or as crystals in lithic clasts. Volcanic fallout ash particles formed the major fraction of the magnetic extract from each sediment sample. Three groups of volcanic ashes were identified: trachytic ashes, basaltic ashes with sideromelane and tachylite shards, and palagonitic ashes. These three groups could be equally well defined based on their magnetic hysteresis properties and alternating field demagnetization curves. The highest coercivities of all samples were found for the tachylite, due to the submicrometre-size titanomagnetite inclusions in the matrix. Trachytic ashes had intermediate magnetic properties between the single-domain-type tachylites and the palagonitic (altered) basaltic ashes with low coercivities. Samples which contained mixtures of these different volcanic ashes could be distinguished from the three types of ashes based on their magnetic characteristics. There was neither evidence of biogenic magnetofossils in the transmission electron micrographs nor did we find magnetic particles derived from continental Antarctica. The presence of dispersed volcanic fallout ashes between visible ash layers suggests continuous explosive volcanic activity on the Kerguelen Plateau in the South Indian Ocean since the early Eocene. The continuous fallout of volcanic ash from explosive volcanism on the Kerguelen Archipelago is the source of the magnetic particles and thus responsible for the magnetostratigraphy of the nannofossil oozes drilled during Leg 120.

  7. A Systematic Comparison of Anisotropy of Magnetic Susceptibility (AMS) and Anisotropy of Remanence (AARM) fabrics of ignimbrites: Examples from the Gold Point area, Nevada and Jemez Mountains, New Mexico

    Science.gov (United States)

    Kharwat, R.; Geissman, J. W.; Fitter, T.

    2013-12-01

    Anisotropy of magnetic susceptibility (AMS) has been widely used to define petrofabrics in silicic, elevated-temperature pyroclastic deposits (i.e. ignimbrites) and have successfully identified pyroclastic emplacement or transport directions in many cases. Anisotropy of remanence studies, which are more time-consuming, are far less commonly used to evaluate ignimbrite fabrics. As part of a broad study to understand the Neogene history of deformation associated with a transfer system in the western Great Basin paleomagnetic and magnetic fabric data have been collected from ignimbrites that originated from the Timber Mountain Caldera complex, active from 14-11.5 Ma. A subset of this collection, as well as the Quaternary Bandelier Tuff, exposed in the Jemez Mountains, New Mexico, have been studied in order to systematically compare anisotropy of remanence (mainly anhysteretic remanent magnetization, AARM) with AMS data from the same sites. The relationship between AMS and anisotropy of remanence fabrics in these rocks offers insight into which approach provides data that are more indicative of actual emplacement related fabrics and a measure of anisotropy. AARM data can be advantageous when compared to AMS results, as remanence is typically more sensitive to mineral grains with higher degree of anisotropies (i.e. ferro/ferrimagnetic minerals). Here, AMS and AARM are compared for 15 (9-10 samples per site) sites in western Nevada ignimbrites, and several sites in the Bandelier Tuff (in progress), with each chosen to examine the effects of varying degrees of welding and crystal content on the fabrics obtained. The average bulk susceptibility for the Nevada sites is 4.38 x 10-03 (SI volume), indicating that magnetite is the dominant contributor. AMS imbrication fabric data for these sites typically show a northwest transport direction, which is consistent with the source. The Degree of anisotropy for AARM data ranges from 1.04 to 2.24 for Nevada sites. The relationships

  8. Lithospheric Thickness Variations from Gravity and Topography in Areas of High Crustal Remanent Magnetization on Mars

    Science.gov (United States)

    Smrekar, S. E.; Raymond, C. A.

    2001-01-01

    Large regions of intense crustal re- manent magnetization were fortuitously discovered on Mars by the Mars Global Surveyor (MGS) spacecraft. Gravity and topography admittance studies are used to examine lithospheric structure in the areas of intense magnetization. Areas with positively magnetized crust appear to have thinner crust and elastic lithosphere than negatively magnetized crust. Additional information is contained in the original extended abstract.

  9. Remanence magnetic records of the recent 130 000 years from the sediments in Nansha area, South China Sea

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaoqiang; ZHOU Wenjuan; GAO Fanglei; LI Huamei

    2007-01-01

    Two hundred and eighty-one samples, collected from drilling core NS93-5 located in the Nansha area of the South China Sea, were used to study the magnetic character-istics of the sediments in the sea. Detailed rock magnetic results show that the magnetic minerals of the sediments were dominated by ferrimagnetic minerals such as magnetite,and a small contribution of hematite and maghematite also existed. The sediments recorded three negative values of remanence magnetic inclination at the depth: 191-206 cm,232-248 cm, and 292-308 cm. The corresponding ages of these negative values were 65.87-68.7 ka B.P., 73.4-80.8 ka B.P. And 108.4-113.6 ka B.P., respectively, according to stratigraphy of oxygen isotope, 14>C, and the age of a volca-nic ash layer. The negative value during 108.4-113.6 ka B.P.may be the record of a Blake event in the sediments of the Nansha area.

  10. Using thermal remanent magnetisation (TRM) to distinguish block and ash flow and debris flow deposits, and to estimate their emplacement temperature: 1991-1995 lava dome eruption at Mt. Unzen Volcano, Japan

    Science.gov (United States)

    Uehara, D.; Cas, R. A. F.; Folkes, C.; Takarada, S.; Oda, H.; Porreca, M.

    2015-09-01

    The 1991-1995 Mt. Unzen eruption (Kyushu, Japan) produced 13 lava domes, approximately 9400 block and ash pyroclastic flows (BAF) resulting from lava dome collapse events and syn- and post-dome collapse debris flow (DF) events. In the field, it can be very difficult to distinguish from field facies characteristics which deposits are primary hot BAF, cold BAF or rock avalanche, or secondary DF deposits. In this study we use a combination of field observations and thermal remanent magnetisation (TRM) analysis of juvenile, lava dome derived clasts from seven deposits of the 1991-1995 Mt. Unzen eruption in order to distinguish between primary BAF deposits and secondary DF deposits and to determine their emplacement temperature. Four major TRM patterns were identified: (1) Type I: clasts with a single magnetic component oriented parallel to the Earth's magnetic field at time and site of emplacement. This indicates that these deposits were deposited at very high temperature, between the Curie temperature of magnetite (~ 540 °C) and the glass transition temperature of the lava dome (~ 745 °C). These clasts are found in high temperature BAF deposits. (2) Type II: clasts with two magnetic components of magnetisation. The lower temperature magnetic components are parallel to the Earth's magnetic field at time of the Unzen eruption. Temperature estimations for these deposits can range from 80 to 540 °C. We found this paleomagnetic behaviour in moderate temperature BAF or warm DF deposits. (3) Type III: clasts with three magnetic components, with a lower temperature component oriented parallel to the Earth's magnetic field at Unzen. The individual clast temperatures estimated for this kind of deposit are usually less than 300 °C. We interpret this paleomagnetic behaviour as the effect of different thermal events during their emplacement history. There are several interpretations for this paleomagnetic behaviour including remobilisation of moderate temperature BAF, warm DF

  11. Diagenetic alteration of natural Fe-Ti oxides identified by energy dispersive spectroscopy and low-temperature magnetic remanence and hysteresis measurements

    OpenAIRE

    Dillon, Melanie; Franke, Christine

    2008-01-01

    Diagenetic alteration of natural Fe-Ti oxides identified by energy dispersive spectroscopy and low-temperature magnetic remanence and hysteresis measurements GERMANY (Dillon, Melanie) GERMANY Received: 2007-12-20 Revised: 2008-07-24 Accepted: 2008-08-06

  12. Magnetostriction of a sphere: stress development during magnetization and residual stresses due to the remanent field

    Science.gov (United States)

    Reich, Felix A.; Rickert, Wilhelm; Stahn, Oliver; Müller, Wolfgang H.

    2017-03-01

    Based on the principles of rational continuum mechanics and electrodynamics (see Truesdell and Toupin in Handbuch der Physik, Springer, Berlin, 1960 or Kovetz in Electromagnetic theory, Oxford University Press, Oxford, 2000), we present closed-form solutions for the mechanical displacements and stresses of two different magnets. Both magnets are initially of spherical shape. The first (hard) magnet is uniformly magnetized and deforms due to the field induced by the magnetization. In the second problem of a (soft) linear-magnetic sphere, the deformation is caused by an applied external field, giving rise to magnetization. Both problems can be used for modeling parts of general magnetization processes. We will address the similarities between both settings in context with the solutions for the stresses and displacements. In both problems, the volumetric Lorentz force density vanishes. However, a Lorentz surface traction is present. This traction is determined from the magnetic flux density. Since the obtained displacements and stresses are small in magnitude, we may use Hooke's law with a small-strain approximation, resulting in the Lamé- Navier equations of linear elasticity theory. If gravity is neglected and azimuthal symmetry is assumed, these equations can be solved in terms of a series. This has been done by Hiramatsu and Oka (Int J Rock Mech Min Sci Geomech Abstr 3(2):89-90, 1966) before. We make use of their series solution for the displacements and the stresses and expand the Lorentz tractions of the analyzed problems suitably in order to find the expansion coefficients. The resulting algebraic system yields finite numbers of nonvanishing coefficients. Finally, the resulting stresses, displacements, principal strains and the Lorentz tractions are illustrated and discussed.

  13. Magnetostriction of a sphere: stress development during magnetization and residual stresses due to the remanent field

    Science.gov (United States)

    Reich, Felix A.; Rickert, Wilhelm; Stahn, Oliver; Müller, Wolfgang H.

    2016-12-01

    Based on the principles of rational continuum mechanics and electrodynamics (see Truesdell and Toupin in Handbuch der Physik, Springer, Berlin, 1960 or Kovetz in Electromagnetic theory, Oxford University Press, Oxford, 2000), we present closed-form solutions for the mechanical displacements and stresses of two different magnets. Both magnets are initially of spherical shape. The first (hard) magnet is uniformly magnetized and deforms due to the field induced by the magnetization. In the second problem of a (soft) linear-magnetic sphere, the deformation is caused by an applied external field, giving rise to magnetization. Both problems can be used for modeling parts of general magnetization processes. We will address the similarities between both settings in context with the solutions for the stresses and displacements. In both problems, the volumetric uc(Lorentz) force density vanishes. However, a uc(Lorentz) surface traction is present. This traction is determined from the magnetic flux density. Since the obtained displacements and stresses are small in magnitude, we may use uc(Hooke's) law with a small-strain approximation, resulting in the uc(Lamé)-uc(Navier) equations of linear elasticity theory. If gravity is neglected and azimuthal symmetry is assumed, these equations can be solved in terms of a series. This has been done by uc(Hiramatsu) and uc(Oka) (Int J Rock Mech Min Sci Geomech Abstr 3(2):89-90, 1966) before. We make use of their series solution for the displacements and the stresses and expand the uc(Lorentz) tractions of the analyzed problems suitably in order to find the expansion coefficients. The resulting algebraic system yields finite numbers of nonvanishing coefficients. Finally, the resulting stresses, displacements, principal strains and the uc(Lorentz) tractions are illustrated and discussed.

  14. Apparent specific heat of a spin glass ( Au Fe 6 at %) in presence of a remanent magnetization and associated energy and magnetization relaxations

    Science.gov (United States)

    Berton, A.; Chaussy, J.; Odin, J.; Peyrard, J.; Prejean, J. J.; Souletie, J.

    1981-01-01

    We present measurements of the relaxations of the remanent magnetization and of the energy flux on the same samples of Au Fe spin glass (4 at % and 6 at %) at several temperatures below the temperature T G of the susceptibility cusp. The observed relaxations can be expressed in terms of the unique composite variable T ℓnt/τ which implies the existence of thermally activated asymetrical double well potentials. A consequency of this observation is the existence of a time and temperature contribution to the specific heat which is investigated directly and compared with expectation.

  15. Timing of natural remanent magnetization in ferriferous limestones from the Swiss Jura mountains

    Science.gov (United States)

    Gehring, Andreas U.; Heller, Friedrich

    1989-06-01

    Goethite and hematite are the main magnetic phases contained in two ferriferous middle Jurassic beds which are exposed within the Mandach structure, the major tectonic structure of the eastern tabular Jura of northern Switzerland. The iron oxidic phases in a reddish brown sparry limestone known as Spatkalk were formed diagenetically, whereas these phases are weathering products in a stratigraphically slightly younger oolitic bed. The hematite in the oolitic bed was magnetized after the Jura main tectonic event in the Miocene whereas the hematite in the Spatkalk was magnetized before the Miocene. The goethites in the oolitic bed carry a pretectonic and in the Spatkalk a syntectonic magnetization. Physical and chemical data show that the goethite which was resistant to remagnetization contains an Al-substitution of 3.4 mol% resulting in a Néel temperature of 90°C. The remagnetized goethite has an Al-content of 10.7 mol% and a Néel temperature of 70°C. The different goethite properties indicate that the tectonic formation of the Mandach structure occurred under low-temperature conditions below 90°C.

  16. 10Be evidence for delayed acquisition of remanent magnetization in marine sediments: Implication for a new age for the Matuyama-Brunhes boundary

    Science.gov (United States)

    Suganuma, Yusuke; Yokoyama, Yusuke; Yamazaki, Toshitsugu; Kawamura, Kenji; Horng, Chorng-Shern; Matsuzaki, Hiroyuki

    2010-08-01

    Fluxes of the meteoric cosmogenic radionuclide 10Be vary with changes in the incoming cosmic rays modulated by geomagnetic field intensity variations. The variability in the 10Be flux can be used to synchronize ice cores, as well as marine sediments, by comparison with the relative paleointensity variations of the geomagnetic field. However, lock-in of the paleomagnetic signal at some depth below the sediment-water interface in marine sediments through acquisition of a post-depositional remanent magnetization (PDRM) adds uncertainty to synchronization. Despite the long history of such studies, the magnitude of the PDRM lock-in depth remains controversial. In this article, we present clear evidence for a downward offset of the paleointensity minimum relative to the 10Be flux anomaly at the Matuyama-Brunhes (M-B) geomagnetic polarity boundary, which we interpret to result from a ˜ 15 cm PDRM lock in depth. This lock-in depth indicates that up to several tens of thousands years of age offset probably occurs when a paleomagnetic record is used for dating marine sediments, and the age of the M-B boundary should be revised to ca. 10 kyr younger, which is consistent with a younger ice core derived age of 770 ± 6 ka (2 σ). This cosmogenic age tuning strategy will contribute to refining paleomagnetic-based age models for marine sediments and identifying of lead-lag relationships for global abrupt environmental changes.

  17. Physical interpretation of isothermal remanent magnetization end-members: New insights into the environmental history of Lake Hovsgul, Mongolia

    Science.gov (United States)

    Fabian, Karl; Shcherbakov, Valeriy P.; Kosareva, Lina; Nourgaliev, Danis

    2016-11-01

    Acquisition curves of isothermal remanent magnetization for 1057 samples of core KDP-01 from Lake Hovsgul (Mongolia) are decomposed into three end-members using non-negative matrix factorization. The obtained mixing coefficients also decompose hysteresis loops, back-field, and strong-field thermomagnetic curves into their related end-member components. This proves that the end-members represent different mineralogical fractions of the Lake Hovsgul sedimentary environment. The method used for unmixing offers a new possibility to apply rock magnetism in paleoecological and paleoclimatic studies. For Lake Hovsgul, it indicates that a low-coercivity component with a covarying paramagnetic phase represents a coarse-grained magnetite fraction from terrigenous influx probably via fluvial transport. A second component with coercivities close to 50 mT is identified as a magnetite fraction related to magnetosomes of magnetotactic bacteria. The third component has coercivities near 85 mT and is identified as greigite of biotic or abiotic origin common in suboxic/anoxic sediments. Significant positive correlations between variations of intensity of all three mineralogical components along the core are found. A rapid drop in all end-member concentrations by more than one order of magnitude at about 20 m depth testifies to a major change of the environmental or geological conditions of Lake Hovsgul. It possibly is related to the onset of MIS 10 marking the termination of arid climate conditions. Short intervals of high productivity are characterized by an abundance of magnetite magnetosomes and may highlight glacial-interglacial transition intervals. For the rest of the core, greigite magnetization substantially exceeds that of magnetite, indicating a predominantly anoxic environment.

  18. Direct visualization of chemical and thermo-remanent magnetization of pseudo-single-domain magnetite grains and the implications for reliable paleomagentic signal acquisition

    Science.gov (United States)

    Almeida, T.; Muxworthy, A. R.; Kasama, T.; Williams, W.; Kovács, A.; Dunin-Borkowski, R.; Hansen, T. W.

    2015-12-01

    In order to reliably interpret paleomagnetic measurements, the mechanisms of chemical remanent magnetization (CRM) and thermoremanent magnetization (TRM) must be fully understood. Currently, most models of CRM and TRM processes only exist for the smallest, uniformly magnetized grains, termed single domain (SD). However, the magnetic signal from rocks is often dominated by slightly larger grains containing non-uniform magnetization states, termed pseudo-SD (PSD) grains. Magnetite (Fe3O4) is the most magnetic naturally occurring mineral on Earth, carrying the dominant magnetic signature in rocks and providing a critical tool in paleomagnetism. The oxidation of Fe3O4 to other iron oxides, such as maghemite (γ-Fe2O3) and hematite (α-Fe2O3), is of particular interest as it influences the preservation of remanence of the Earth's magnetic field by Fe3O4. Further, TRM in Fe3O4 grains is acquired in the direction of the ambient geomagnetic field as they cool below their Curie temperature (TC) of ~ 580 ˚C. The latest transmission electron microscopy (TEM) techniques like electron holography and environmental TEM (ETEM) allows for the imaging of magnetization in nano-scale minerals during in situ heating under vacuum and controlled atmospheres. In the present study, synthetic Fe3O4 particles in the PSD size range (CRM was visualized using electron holography, in the form of reconstructed magnetic induction maps, where the oxidized grains exhibited a loss of overall remanence and change in remanent direction. The thermomagnetic behavior of Fe3O4 particles in the PSD size range is also investigated using off-axis electron holography. Magnetic induction maps, which are recorded during in situ heating up to above the TC, reveal the PSD nature of several Fe3O4 grains by visualizing their vortex domain states. The vortex states in small Fe3O4 grains (Fig. 1a & b) are shown to rotate or collapse into a single-domain state close to its unblocking temperature (Fig. 1c), rather than

  19. Rock Magnetic and Oxide Microscopy Studies of two South American Iron-Ore Deposits

    Science.gov (United States)

    Alva-Valdivia, L. M.

    2005-05-01

    Microscopy and rock-magnetic studies of the iron oxide-ore and host rocks in the Cristales-Pleito Melon (Chile) and Jacupiranga (Brazil) deposits were carried out to characterize and compare the magnetic mineralogy and the processes that affected the natural remanent magnetization (NRM) during emplacement and evolution of the iron-ore deposits. The microscopy study under reflected light shows that magnetic carriers are mainly magnetites, with minor amounts of ilmenite-hematite minerals. Titanomagnetite, shows trellis texture, which is compatible with high temperature oxy-exsolution processes. Grain sizes range from a few microns to >100 µm, and dominant magnetic state pseudo-single-domain, in agreement with hysteresis measurements. Thermal spectra, continuous susceptibility measurements, and isothermal remanent magnetization (IRM) acquisition suggest a predominance of some spinels (titanomagnetite or titanomaghemite) with low-Ti content as magnetic carriers. These data help to investigate the magnetic domain states and the remanence acquisition processes, and to assess their significance as a source of magnetic anomalies.

  20. Rock-magnetism and ore microscopy of the magnetite-apatite ore deposit from Cerro de Mercado, Mexico

    Science.gov (United States)

    Alva-Valdivia, L. M.; Goguitchaichvili, A.; Urrutia-Fucugauchi, J.; Caballero-Miranda, C.; Vivallo, W.

    2001-03-01

    Rock-magnetic and microscopic studies of the iron ores and associated igneous rocks in the Cerro de Mercado, Mexico, were carried out to determine the magnetic mineralogy and origin of natural remanent magnetization (NRM), related to the thermo-chemical processes due to hydrothermalism. Chemical remanent magnetization (CRM) seems to be present in most of investigated ore and wall rock samples, replacing completely or partially an original thermoremanent magnetization (TRM). Magnetite (or Ti-poor titanomagnetite) and hematite are commonly found in the ores. Although hematite may carry a stable CRM, no secondary components are detected above 580°, which probably attests that oxidation occurred soon enough after the extrusion and cooling of the ore-bearing magma. NRM polarities for most of the studied units are reverse. There is some scatter in the cleaned remanence directions of the ores, which may result from physical movement of the ores during faulting or mining, or from perturbation of the ambient field during remanence acquisition by inhomogeneous internal fields within these strongly magnetic ore deposits. The microscopy study under reflected light shows that the magnetic carriers are mainly titanomagnetite, with significant amounts of ilmenite-hematite minerals, and goethite-limonite resulting from alteration processes. Magmatic titanomagnetites, which are found in igneous rocks, show trellis, sandwich, and composite textures, which are compatible with high temperature (deuteric) oxy-exsolution processes. Hydrothermal alteration in ore deposits is mainly indicated by martitization in oxide minerals. Grain sizes range from a few microns to >100 mm, and possible magnetic state from single to multidomain, in agreement with hysteresis measurements. Thermal spectra, continuous susceptibility measurements, and IRM (isothermal remanent magnetization) acquisition suggest a predominance of spinels as magnetic carriers, most probably titanomagnetites with low

  1. Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles

    Science.gov (United States)

    Xu, S. T.; Ma, Y. Q.; Zheng, G. H.; Dai, Z. X.

    2015-04-01

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23 817 and 15 056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance.

  2. Investigations of the Origin of the Magnetic Remanence in Late Pleistocene Lacustrine Sediments in the Mono Basin, CA

    Science.gov (United States)

    Vasquez, N.; Corley, A. D.

    2015-12-01

    In the Mono Basin, CA, fine sand, silt, and volcanic ash deposited in Pleistocene Lake Russell is exposed on the margin of Mono Lake, and on Paoha Island in the lake. The silt records the Mono Lake Excursion (MLE: Denham and Cox, 1971) and several tens of thousands of years of paleomagnetic secular variation (PSV: Denham and Cox, 1971; Liddicoat, 1976; Lund et al., 1988). The sediment is believed to be an accurate recorder of PSV because the MLE has the same signal at widely separated localities in the basin (Denham, 1974; Liddicoat and Coe, 1979; Liddicoat, 1992) with the exception at wave-cut cliffs on the southeast side of the lake (Coe and Liddicoat, 1994). Magnetite, titanomagnetite, and titanomaghemite are present in the sediment (Denham and Cox, 1971; Liddicoat, 1976; Liddicoat and Coe, 1979), which is glacial flour from the adjacent Sierra Nevada (Lajoie, 1968). X-rays of the sediment and lineation measurements show patterns of normal bedding with layers aligned such that the minimum axes are within 5-10 degrees of normal bedding, with 10 percent foliation and 1 percent lineation (Coe and Liddicoat, 1994). We explore reasons for the difference in part of the PSV record at the wave-cut cliffs beyond the interpretation of Coe and Liddicoat (1994) that paleomagnetic field strength is a controlling factor. Possibilities include the sedimentation rate - at localities on the margin of Mono Lake the rate is about 60 percent less than at the wave-cut cliffs - and lithology of the sediment. At Mill Creek on the northwest side of Mono Lake, the non-magnetic sediment fraction is coarser-grained than at the wave-cut cliffs by a factor of about two, and there is a similar difference in the total inorganic carbon (TIC) percentage by weight for the two localities. (Spokowski et al., 2011) Studies of the sediment at two localities in the basin where the Hilina Pali Excursion (Teanby et al., 2002) might be recorded (Wilson Creek and South Shore Cliffs; Liddicoat and Coe

  3. Hydrothermal alteration and its effects on the magnetic properties of Los Pelambres, a large multistage porphyry copper deposit

    Science.gov (United States)

    Tapia, Joseline; Townley, Brian; Córdova, Loreto; Poblete, Fernando; Arriagada, César

    2016-09-01

    The Los Pelambres porphyry copper deposit is located 190 km north of Santiago, Chile. A paleomagnetic and mineralogical study was conducted at this deposit to determine the effects of hydrothermal alteration on the magnetic properties and minerals of rocks within the deposit when compared to the surrounding country rock. In the Los Pelambres deposit, magnetic properties of rocks are carried by titano-hematite and titano-magnetite solid solution minerals, where the former commonly indicates the exsolution of rutile. Magnetic minerals of intrusive rocks from the greater Los Pelambres region show that magmatic titano-magnetites and magnetites are the main magnetization carriers. The hydrothermal fluid associated with rutile exsolution textures could have played an important role in the mineralization of Cu in this deposit. The paleomagnetic properties in the Los Pelambres deposit can be divided in three main groups: (i) HMRG (high magnetic remanence group), (ii) HMSG (high magnetic susceptibility group), and (iii) LMSG (low magnetic susceptibility/remanence group). In-situ magnetic properties of the HMSG and LMSG are similar to the formations and units present regionally, however HRMG samples clearly differ from the country rocks. The high variability of in-situ magnetic properties presented in the Los Pelambres deposit has also been characteristic of other porphyry copper deposits in Chile (e.g., Chuquicamata and El Teniente). Regarding the field of exploration geophysics and porphyry copper deposits, this study suggests that phyllic, chloritic, and potassic alterations are related to low, intermediate, and high in-situ NRM, respectively, suggesting that geophysical methods must target a noisy magnetic signal depending on the scale of the study. The knowledge and results obtained are especially meaningful because magnetic surveys conducted for exploration do not commonly allow for the detection of ore mineralization.

  4. Magnetic remanence in Yb14-xRExMnSb11 (RE=Tb, Dy, Ho) single crystals

    Science.gov (United States)

    Grebenkemper, Jason H.; Hu, Yufei; Abdusalyamova, M. N.; Makhmudov, F. A.; Kauzlarich, Susan M.

    2016-06-01

    Single crystals of Yb14-xRExMnSb11 (x~0.1, 0.4; RE = Tb, Dy, Ho) have been prepared as a solid solution by Sn flux reactions of the elements. They crystallize in the Ca14AlSb11 structure type in the I41/acd space group. The RE3+preferentially substitutes on the Yb(1) site which is the smallest volume Yb containing polyhedron. In the case of Ho3+, a small amount of Ho3+ also substitutes on the Yb(4) site. The ferromagnetic ordering temperature of Yb14MnSb11 is reduced from 53 K to 41 K as x increases and dependent on the identity of the RE. This is attributed to the reduction in carriers and reduced screening of the Mn2+ local moment. The effective moments, μeff, agree well with the calculated moments assuming the RE substitutes as a trivalent cation. The largest coercive field is observed for RE = Dy (1000 Oe). For the maximum x of Yb14-xRExMnSb11 there are enough carriers for the Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism of magnetic coupling via conduction electrons to still be valid in describing the ferromagnetic ordering.

  5. Deposition of thick Co-rich CoPtP films with high energy product for magnetic microelectromechanical applications

    Energy Technology Data Exchange (ETDEWEB)

    Kulkarni, Santosh [Microsystems Center, Tyndall National Institute, University College Cork, Lee Maltings, Prospect Row, Cork (Ireland); Roy, Saibal, E-mail: saibal.roy@tyndall.i [Microsystems Center, Tyndall National Institute, University College Cork, Lee Maltings, Prospect Row, Cork (Ireland)

    2010-05-15

    We report the development of Co-rich CoPtP films of thicknesses up to 82 mum for use in magnetic MEMS applications. These films have been deposited using a combination of pulse-reverse plating with the addition of stress-relieving additives to the bath. The films were electroplated on sputtered Cu/Ti seed layer on silicon with an optimized thickness of 100/20 nm. The composition, crystalline structure, grain size and magnetic properties of the CoPtP films of varying thickness are compared and analyzed. The 3-mum-thick CoPtP film showed a columnar structure and strong perpendicular anisotropy. This film shows a perpendicular coercivity of 2150 Oe, a remanence of 0.564 T and a maximum energy product of 20 kJ/m{sup 3}. As the thickness of the plated film is increased, there is a gradual decrease in the coercivity and anisotropy. The 82-mum-thick film had a perpendicular coercivity of 1150 Oe and a remanence of 0.35 T. While there is a drop in coercivity and anisotropy, the remanence and maximum energy product remain constant for film thicknesses greater than 13 mum. The reason for the drop in coercivity and the near-constant remanence for thicker CoPtP films is discussed here. The coercivity of the thick Co-rich CoPtP film reported in this work is similar to those reported in the literature; the values of remanence, maximum energy product and saturation magnetization are the highest of all the thick (>50 mum) electroplated films in the literature.

  6. Performance of remanent supermirror benders

    Energy Technology Data Exchange (ETDEWEB)

    Boeni, P.; Clemens, D.; Horisberger, M.; Rubio, D.; Tixier, S. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Hahn, W. [ISIS (United Kingdom)

    1997-09-01

    Polarising supermirrors composed of magnetic and non-magnetic layers have been deposited on thin glass sheets by means of reactive DC-magnetron sputtering. Benders that are composed of such glass have an excellent transmission and can be used for polarising neutrons in zero field. (author) 3 figs., 1 tab., 2 refs.

  7. High coercivity remanence in baked clay materials used in archeomagnetism

    Science.gov (United States)

    McIntosh, Gregg; Kovacheva, Mary; Catanzariti, Gianluca; Donadini, Fabio; Lopez, Maria Luisa Osete

    2011-02-01

    A study of the high coercivity remanence in archeological baked clays has been carried out. More than 150 specimens from 46 sites across Europe have been analyzed, selected on the basis of the presence of a fraction of their natural remanence that was resistant to alternating field demagnetization to 100 mT. The study was based on the stability of isothermal remanence to alternating field and thermal demagnetization and its variation on cooling to liquid nitrogen temperature. Results indicate that the high coercivity remanence may be carried by magnetite, hematite, and in isolated cases partially oxidized magnetite and goethite. In addition, a high coercivity, thermally stable, low unblocking temperature phase has been identified. The unblocking temperatures of both the isothermal remanence and the alternating field resistant natural remanence exhibit similar unblocking temperatures, suggesting that the same phases carry both signals. The high coercivity, low unblocking temperature phase contributes to the natural remanence, sometimes carrying a stable direction and behaving ideally during palaeointensity experiments and sometimes not. An unambiguous mineralogical identification of this phase is lacking, although likely candidates include hemoilmentite, related to clay source lithology, and substituted hematite or magnetic ferri-cristabolite, both possible products of thermal transformation of iron-bearing clays.

  8. Depositional chronology and fabric of Siwalik group sediments in Central Nepal from magnetostratigraphy and magnetic anisotropy

    Science.gov (United States)

    Gautam, Pitambar; Rösler, Wolfgang

    1999-12-01

    Magnetostratigraphic research, undertaken within the past 15 years in the Siwaliks distributed along 400 km of the Sub-Himalaya in central Nepal, has proved that the sediments possess highly reliable hematite-based primary detrital remanent magnetization suitable to determine depositional chronology. In order to bring out the polarity sequences in a common chronological frame, all available data are newly correlated to the latest global magnetic polarity time scale of Cande and Kent (S.C. Cande, D.V. Kent (1995) Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic. Journal of Geophysical Research 100, 6093-6095). Chronological data presented are referred, in relation to the diverse lithological nomenclature, to the formations whose ages are not constrained by isotopic or paleontologic ages. The age of the sections dated by magnetostratigraphy ranges between 14 and <2 Ma. Sediment accumulation rates average to 32-50 cm kyr -1. Rock-magnetic parameters, e.g. initial susceptibility and isothermal remanent magnetization ratios, allow correlation with an accuracy of up to a few hundred meters among several kilometers thick adjacent sections. Anisotropy of magnetic susceptibility (AMS) data reveal a well-defined fabric contributed to by paramagnetic ( k=10 -5 to 3×10 -4 SI) as well as ferromagnetic minerals ( k=3×10 -4 to 10 -2 SI). AMS ellipsoids are mainly oblate along with some prolate ones and the degree of anisotropy is mostly low ( P'<1.2). The magnetic fabric is of pre-folding origin with tilt-corrected sub-vertical magnetic foliation poles. The magnetic lineations do not show parallelism to the expected paleocurrent directions. Rather, sub-parallelism between the clusters of magnetic lineation and the fold axes/bedding strikes/thrust fronts is observed. A superimposed fabric consisting of a sedimentary-compactional and an overprint induced by a mild deformation process is suggested. The latter process was active during

  9. Micromagnetic simulation and the angular dependence of coercivity and remanence for array of polycrystalline nickel nanowires

    Science.gov (United States)

    Fuentes, G. P.; Holanda, J.; Guerra, Y.; Silva, D. B. O.; Farias, B. V. M.; Padrón-Hernández, E.

    2017-02-01

    We present here our experimental results for the preparation and characterization of nanowires of nickel and the analysis of the angular dependence of coercivity and remanence using experimental data and micromagnetic simulation. The fabrication was made by using aluminum oxide membranes as templates and deposited nickel by an electrochemical route. The magnetic measurements showed that coercivity and remanence are dependent of the angle of application of the external magnetic field. Our results are different than that expected for the coherent, vortex and transversal modes of the reversion for the magnetic moments. According to the transmission electron microscopy analysis we can see that our nanowires have not a perfect cylindrical format. That is why we have used the ellipsoids chain model for better understanding the real structure of wires and its relation with the magnetic behavior. In order to generate theoretical results for this configuration we have made micromagnetic simulation using Nmag code. Our numerical results for the realistic distances are in correspondence with the magnetic measurements and we can see that there are contradictions if we assume the transverse reversal mode. Then, we can conclude that structure of nanowires should be taken into account to understand the discrepancies reported in the literature for the reversion mechanism in arrays of nickel nanowires.

  10. Demagnetization treatment of remanent composite microspheres studied by alternating current susceptibility measurements

    NARCIS (Netherlands)

    van Berkum, S.; Erné, B.H.

    2013-01-01

    The magnetic remanence of silica microspheres with a low concentration of embedded cobalt ferrite nanoparticles is studied after demagnetization and remagnetization treatments. When the microspheres are dispersed in a liquid, alternating current (AC) magnetic susceptibility spectra reveal a constant

  11. Perpendicular magnetic anisotropy and magneto-optical Kerr effect of vapor-deposited Co/Pt-layered structures

    Science.gov (United States)

    Zeper, W. B.; Greidanus, F. J. A. M.; Carcia, P. F.; Fincher, C. R.

    1989-06-01

    We prepared by vapor deposition at room temperature thin (500 Å) Co/Pt multilayers or layered structures directly onto glass or Si substrates. They show a preferential magnetization perpendicular to the film plane for Co thicknesses below 12 Å and a 100% perpendicular remanence for Co thicknesses below 4.5 Å. The magnetic anisotropy can be explained by an interface contribution to the anisotropy. We also investigated the magneto-optical (MO) polar Kerr effect of these multilayers. Because of their excellent magnetic properties and their potentially high oxidation and corrosion resistance, these Co/Pt-layered structures are very promising candidates for MO recording. The Kerr rotation θk at λ=820 nm for a 35×(4.0 Å Co+12.7 Å Pt)-layered structure, which has 100% magnetic remanence, is modest (-0.12°), but the reflectivity R is high (70%), which results in a respectable figure of merit Rθ2k. Furthermore, the Kerr effect increases towards shorter wavelengths and thus favors future higher-density recording.

  12. Inverse magnetic fabric in unconsolidated sandy event deposits in Kiritappu Marsh, Hokkaido, Japan

    Science.gov (United States)

    Kon, Shusaku; Nakamura, Norihiro; Nishimura, Yuichi; Goto, Kazuhisa; Sugawara, Daisuke

    2017-03-01

    Anisotropy of magnetic susceptibility (AMS) and anisotropy of anhysteretic remanence magnetization (AARM) were evaluated for samples collected from units of two unconsolidated sandy event layers, presumed to be paleo-tsunami deposits, from Kiritappu Marsh, northeastern Japan. The AARM technique isolates the fabric of fine-grained (titano)magnetite from AMS fabric of all minerals in deposits. Bulk susceptibilities of the older event layer were weaker than those of the younger event layer. Our AMS results show that the principal minimum AMS axes (Kmin) were distributed along the horizontal bedding plane, suggesting the presence of an AMS ;inverse fabric; where magnetic axes are interchanged. Our AARM results indicated the principal maximum AARM axes (kmax) are parallel to the AMS Kmin, whereas the AARM intermediate and minimum axes (kint and kmin) are related to the AMS Kmax and Kint. Moreover, the shape of anisotropy parameters revealed that the AMS is oblate (Kmax ≈ Kint), whereas the AARM is prolate (kint ≈ kmin). We found the presence of single-domain sized titanomagnetites in the mud matrix based on electron microscopy observations. AARM is regarded as a complementary tool to estimate paleocurrent directions using grain fabrics of unconsolidated sediments. However, these lines of evidence confirm that our AMS fabrics showed ;inverse fabric;, providing no information about flow directions at this locality. Although this effect is uncommon in soft sediments, it requires caution to estimate paleocurrent directions using AMS.

  13. Pulsed laser deposition and characterization of Alnico5 magnetic films

    Energy Technology Data Exchange (ETDEWEB)

    Butt, M.Z., E-mail: mzbutt49@yahoo.com [Department of Physics, GC University, Lahore 54000 (Pakistan); Ali, Dilawar [Department of Physics, GC University, Lahore 54000 (Pakistan); Ahmad, Fayyaz [Department of Physics, University of Engineering and Technology, Lahore 54890 (Pakistan); Magnetophotonics Research Laboratory, Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2013-09-01

    Alnico5 films were deposited by pulsed laser deposition on glass substrate at room temperature under a vacuum ∼10{sup −3} Torr in the absence and in the presence of 500 Oe external transverse magnetic field applied on the plasma plume during film deposition. For this purpose, Nd:YAG laser was employed to ablate the Alnico5 target. The ablated material was deposited on glass substrate placed at a distance of 2 cm from the target. The structural and magnetic properties of the film were analyzed by X-ray diffraction, atomic force microscope, and vibrating sample magnetometer. X-ray diffraction patterns showed that the Alnico5 films were amorphous in nature. Atomic force microscopy revealed that the Alnico5 film deposited in absence of external magnetic field has larger root-mean-square roughness value (60.2 nm) than the magnetically deposited film (42.9 nm). Vibrating sample magnetometer measurements showed that the in-plane saturation magnetization of Alnico5 film deposited in the presence of external magnetic field increases by 32% as compared to that for the film deposited in the absence of external magnetic field. However, the out-of-plane saturation magnetization was almost independent of the external magnetic field. In magnetically deposited film, there is in-plane anisotropy parallel to the applied external magnetic field.

  14. Inducing vortex formation in multilayered circular dots using remanent curves

    Science.gov (United States)

    Kim, Dong-Ok; Ryeol Lee, Dong; Choi, Yongseong; Metlushko, Vitali; Park, Jihwey; Kim, Jae-Young; Bong Lee, Ki

    2012-11-01

    We report field manipulation of magnetic vortex states in Co(30 nm)/Cu(3 nm)/Ni80Fe20 (20 nm)-multilayer dot arrays via remanent curve. The element-resolved resonant x-ray magnetic measurements, combined with micromagnetic simulations, show vortex formation in the Co layer but not in the NiFe layer along the major hysteresis loop. Although the two magnetic layers are not directly coupled due to the presence of the Cu interlayer, the NiFe layer is strongly influenced by the dipolar field from uncompensated magnetic poles in the Co layer. Using remanent curves, we demonstrate that the single vortex state can be induced simultaneously in both layers.

  15. FeTi oxide mineralogy and the origin of normal and reverse remanent magnetization in dacitic pumice blocks from Mt. Shasta, California

    Science.gov (United States)

    Lawson, C.A.; Nord, G.L.; Champion, D.E.

    1987-01-01

    Detailed mineralogical analyses and rock magnetic experiments have made it possible to directly identify the FeTi oxide phases responsible for the normal and reverse magnetic components of two dacitic pumice blocks from Mt. Shasta, California. Both samples contain a normal component carried by 100 ??m size multi-domain (MD) titanomagnetite (Usp11-24). One sample also contains a second normal component carried by behavior of the ferrian ilmenite. (1) The disordered boundaries are the higher Curie point phase necessary for the operation of the self-reversal mechanism. (2) The disordered domain boundaries either inhibit the formation of magnetic domain walls or restrict magnetic domain wall movement accounting for the PSD or SD behavior of the ferrian ilmenite. ?? 1987.

  16. FeTi oxide mineralogy and the origin of normal and reverse remanent magnetization in dacitic pumice blocks from Mt. Shasta, California

    Science.gov (United States)

    Lawson, Charles A.; Nord, Gordon L.; Champion, Duane E.

    1987-06-01

    Detailed mineralogical analyses and rock magnetic experiments have made it possible to directly identify the FeTi oxide phases responsible for the normal and reverse magnetic components of two dacitic pumice blocks from Mt. Shasta, California. Both samples contain a normal component carried by 100 μm size multi-domain (MD) titanomagnetite (Usp 11-24). One sample also contains a second normal component carried by behavior of the ferrian ilmenite. (1) The disordered boundaries are the higher Curie point phase necessary for the operation of the self-reversal mechanism. (2) The disordered domain boundaries either inhibit the formation of magnetic domain walls or restrict magnetic domain wall movement accounting for the PSD or SD behavior of the ferrian ilmenite.

  17. Room temperature in-plane 〈100〉 magnetic easy axis for Fe{sub 3}O{sub 4}/SrTiO{sub 3}(001):Nb grown by infrared pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Monti, Matteo; Sanz, Mikel; Oujja, Mohamed; Rebollar, Esther; Castillejo, Marta; Marco, José F.; Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química Física “Rocasolano,” CSIC, Madrid E-28006 (Spain); Pedrosa, Francisco J.; Bollero, Alberto [IMDEA Nanociencia, Instituto Madrileño de Estudios Avanzados en Nanociencia, Madrid E-28049 (Spain); Camarero, Julio; Cuñado, Jose Luis F. [IMDEA Nanociencia, Instituto Madrileño de Estudios Avanzados en Nanociencia, Madrid E-28049 (Spain); Dpto. de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid E-28049 (Spain); Nemes, Norbert M. [Dpto. de Física Aplicada III, Universidad Complutense de Madrid, Madrid E-28040 (Spain); Mompean, Federico J.; Garcia-Hernández, Mar [Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid E-28049 (Spain); Nie, Shu; McCarty, Kevin F. [Sandia National Laboratories, Livermore, California 94550 (United States); N' Diaye, Alpha T.; Chen, Gong; Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2013-12-14

    We examine the magnetic easy-axis directions of stoichiometric magnetite films grown on SrTiO{sub 3}:Nb by infrared pulsed-laser deposition. Spin-polarized low-energy electron microscopy reveals that the individual magnetic domains are magnetized along the in-plane 〈100〉 film directions. Magneto-optical Kerr effect measurements show that the maxima of the remanence and coercivity are also along in-plane 〈100〉 film directions. This easy-axis orientation differs from bulk magnetite and films prepared by other techniques, establishing that the magnetic anisotropy can be tuned by film growth.

  18. Iron in the Fire: Searching for Fire's Magnetic Fingerprint using Controlled Heating Experiments, High-Resolution FORCs, IRM Coercivity Spectra, and Low-Temperature Remanence Experiments

    Science.gov (United States)

    Lippert, P. C.; Reiners, P. W.

    2014-12-01

    Evidence for recent climate-wildfire linkages underscores the need for better understanding of relationships between wildfire and major climate shifts in Earth history, which in turn offers the potential for prognoses for wildfire and human adaptations to it. In particular, what are the links between seasonality and wildfire frequency and severity, and what are the feedbacks between wildfire, landscape evolution, and biogeochemical cycles, particularly the carbon and iron cycles? A key first step in addressing these questions is recovering well-described wildfire records from a variety of paleolandscapes and paleoclimate regimes. Although charcoal and organic biomarkers are commonly used indicators of fire, taphonomic processes and time-consuming analytical preparations often preclude their routine use in some environments and in high-stratigraphic resolution paleowildfire surveying. The phenomenological relationship between fire and magnetic susceptibility can make it a useful surveying tool, but increased magnetic susceptibility in sediments is not unique to fire, and thus limits its diagnostic power. Here we utilize component-specific rock magnetic methods and analytical techniques to identify the rock magnetic fingerprint of wildfire. We use a custom-designed air furnace, a series of iron-free laboratory soils, natural saprolites and soils, and fuels from Arizona Ponderosa pine forests and grasslands to simulate wildfire in a controlled and monitored environment. Soil-ash residues and soil and fuel controls were then characterized using First Order Reversal Curve (FORC) patterns, DC backfield IRM coercivity spectra, low-temperature SIRM demagnetization behavior, and low-temperature cycling of room-temperature SIRM behavior. We will complement these magnetic analyses with high-resolution TEM of magnetic extracts. Here we summarize the systematic changes to sediment magnetism as pyrolitized organic matter is incorporated into artificial and natural soils. These

  19. Magnetic anomalies associated with abundant production of pyrrhotite in a sulfide deposit in the Okinawa Trough, Japan

    Science.gov (United States)

    Honsho, Chie; Yamazaki, Toshitsugu; Ura, Tamaki; Okino, Kyoko; Morozumi, Haruhisa; Ueda, Satoshi

    2016-11-01

    We report here results from a deep-sea magnetic survey using an autonomous underwater vehicle over the Hakurei hydrothermal site, in the middle Okinawa Trough. Magnetic inversion revealed that the Hakurei site is associated with well-defined high-magnetization zones distributed within a broad low-magnetization zone. Results from rock magnetic measurements, performed on sulfide ore samples obtained by drilling, showed that some samples possessed extremely high natural remanent magnetization (NRM) (as much as 6.8-953.0 A/m), although most of the measured samples had much lower NRM. These high-NRM samples were characterized by high Königsberger ratios (101-103), indicating much larger NRM than induced magnetization, and contained pyrrhotite as the only magnetic mineral. This suggests that NRM carried by pyrrhotite is the source of the observed magnetic anomalies. The wide range of NRM intensity was considered to be due to a highly heterogeneous distribution of pyrrhotite, because pyrrhotite was commonly identified in both the high-NRM and low-NRM samples. Pyrrhotite production may have been occasionally drastically increased, with highly magnetic ores formed as a result. Rapid burial of active vents may result in the creation of an extensive reducing environment under the seafloor, which is favorable to pyrrhotite production, and may also prevent oxidation of pyrrhotite by isolating it from seawater. Because the magnetization intensity of sulfide ores was highly variable, it would not be straightforward to estimate the quantity of ore deposits from the magnetic anomalies. Nevertheless, this study demonstrates the usefulness of magnetic surveys in detecting hydrothermal deposits.

  20. Strontium-Doped Lanthanum Manganite Films Prepared by Magnetic Deposition

    DEFF Research Database (Denmark)

    Menon, Mohan; Larsen, Casper; Andersen, Kjeld Bøhm

    2009-01-01

    Deposition of La0.85Sr0.15MnO3 (LSM) films from suspensions using a magnetic field was found to be a cheap and quick technique. Ninety weight percent of the particles present in the suspensions were deposited within the first minute of the deposition, and the thickness of the film varied linearly...

  1. Enhanced methane flux event and sediment dispersal pattern in the Krishna–Godavari offshore basin: Evidences from rock magnetic techniques

    Digital Repository Service at National Institute of Oceanography (India)

    Usapkar, A.; Dewangan, P.; Kocherla, M.; Ramprasad, T.; Mazumdar, A.; Ramana, M.V.

    Detailed rock magnetic measurements such as susceptibility (X), susceptibility of anhysteric remanent magnetization (XARM), saturation isothermal remanent magnetization (SIRM), soft-isothermal remanent magnetization (soft-IRM) and hard...

  2. Paleomagnetic dating of tectonically influenced Plio-Quaternary fan-system deposits from the Apennines (Italy

    Directory of Open Access Journals (Sweden)

    Michele Saroli

    2015-03-01

    Full Text Available The Roveto Valley is a narrow, elongated, NW-trending depression filled with continental Plio-Quaternary deposits that outcrop at different topographic elevations. A morpho-lithostratigraphic succession of the continental deposits has been defined in order to reconstruct the geological Quaternary evolution of the area. These deposits do not contain materials suitable for biostratigraphic dating; therefore, in order to determine their chronology, three different units were sampled for magnetostratigraphic investigations. Paleomagnetic results demonstrated that standard demagnetization techniques are effective in removing secondary remanence components and in isolating the characteristic remanent magnetization, allowing us to determine, for each cycle, whether it was deposited before or after the Brunhes-Matuyama geomagnetic reversal at 781 ka. Preliminary rock magnetic analyses indicated that magnetite is the main magnetic carrier and that hematite, which gives the pink colour to the matrix, is in the superparamagnetic grain-size range and thus does not retain any paleomagnetic remanence.

  3. Demagnetization Treatment of Remanent Composite Microspheres Studied by Alternating Current Susceptibility Measurements

    Directory of Open Access Journals (Sweden)

    Ben H. Erné

    2013-09-01

    Full Text Available The magnetic remanence of silica microspheres with a low concentration of embedded cobalt ferrite nanoparticles is studied after demagnetization and remagnetization treatments. When the microspheres are dispersed in a liquid, alternating current (AC magnetic susceptibility spectra reveal a constant characteristic frequency, corresponding to the rotational diffusion of the microparticles; this depends only on particle size and liquid viscosity, making the particles suitable as a rheological probe and indicating that interactions between the microspheres are weak. On the macroscopic scale, a sample with the dry microparticles is magnetically remanent after treatment in a saturating field, and after a demagnetization treatment, the remanence goes down to zero. The AC susceptibility of a liquid dispersion, however, characterizes the remanence on the scale of the individual microparticles, which does not become zero after demagnetization. The reason is that an individual microparticle contains only a relatively small number of magnetic units, so that even if they can be reoriented magnetically at random, the average vector sum of the nanoparticle dipoles is not negligible on the scale of the microparticle. In contrast, on the macroscopic scale, the demagnetization procedure randomizes the orientations of a macroscopic number of magnetic units, resulting in a remanent magnetization that is negligible compared to the saturation magnetization of the entire sample.

  4. Demagnetization treatment of remanent composite microspheres studied by alternating current susceptibility measurements.

    Science.gov (United States)

    van Berkum, Susanne; Erné, Ben H

    2013-09-04

    The magnetic remanence of silica microspheres with a low concentration of embedded cobalt ferrite nanoparticles is studied after demagnetization and remagnetization treatments. When the microspheres are dispersed in a liquid, alternating current (AC) magnetic susceptibility spectra reveal a constant characteristic frequency, corresponding to the rotational diffusion of the microparticles; this depends only on particle size and liquid viscosity, making the particles suitable as a rheological probe and indicating that interactions between the microspheres are weak. On the macroscopic scale, a sample with the dry microparticles is magnetically remanent after treatment in a saturating field, and after a demagnetization treatment, the remanence goes down to zero. The AC susceptibility of a liquid dispersion, however, characterizes the remanence on the scale of the individual microparticles, which does not become zero after demagnetization. The reason is that an individual microparticle contains only a relatively small number of magnetic units, so that even if they can be reoriented magnetically at random, the average vector sum of the nanoparticle dipoles is not negligible on the scale of the microparticle. In contrast, on the macroscopic scale, the demagnetization procedure randomizes the orientations of a macroscopic number of magnetic units, resulting in a remanent magnetization that is negligible compared to the saturation magnetization of the entire sample.

  5. Tailoring out-of-plane magnetic properties of pulsed laser deposited FePt thin films by changing laser energy fluence

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ying; Tan, T.L.; Tan, K.S.; Lee, P. [NSSE, NIE, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore); Liu, Hai; Yadian, Boluo; Hu, Ge; Huang, Yizhong; Ramanujan, R.V. [School of Material Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Rawat, R.S., E-mail: rajdeep.rawat@nie.edu.sg [NSSE, NIE, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore)

    2014-10-01

    Highlights: • Laser energy fluence (LEF) effect on composition, microstructure and magnetism. • Enhancing out-of-plane magnetic properties by tailoring LEF on target surface. • Higher LEF results in more energetic plasma species causing vacancy defects. • Formation of vacancy defect in FePt thin films leads to improved magnetic properties. • Best out-of-plane magnetic properties are achieved with medium LEF. - Abstract: Magnetic properties of pulsed laser deposited (PLD) FePt thin films are investigated at three different laser energy fluences of 51, 136 and 182 J/cm{sup 2}. Deposition at lower laser energy fluence (51 J/cm{sup 2}) yields softer out-of-plane coercivity (≤0.4 kG), whereas deposition at higher laser energy fluence (136 and 182 J/cm{sup 2}) results in harder out-of-plane coercivity (≥5.0 kG). The improved coercivity is found to be attributed to the formation of vacancy defects in thin films, which is indicated by stress change from tensile to compressive form with increasing laser energy fluence. Maximum out-of-plane saturated magnetization of 615 emu/cm{sup 3} and remanent squareness ratio of 0.88 are achieved for 16 nm thick FePt thin films deposited at moderate laser energy fluence of 136 J/cm{sup 2}, making them suitable for high density perpendicular data storage applications.

  6. Remanent Magnetic Field Modeling of Naval Vessels Based on Integral Method and Tikhonov Regularization Method%基于磁场积分法和Tikhonov正则化的船舶固定磁场重建与分解技术

    Institute of Scientific and Technical Information of China (English)

    周国华; 肖昌汉; 刘大明; 刘胜道

    2012-01-01

    Due to the complexity and unpredictability of the magnetization history of ship ferromagnetic material, the remanent magnetic field modeling of ships is always a technical issue in ship magnetic silencing. A new reconstruction method of the remanent magnetic field of ship was proposed based on an integral method and Tikhonov regularization method. Firstly, the magnetic field below a ship was measured, and the induced magnetic field caused by geomagnetic field at the measuring points was calculated. Then, a remanent magnetic field inverse model was given based on the measured data of magnetic field and the calculated induced magnetic field. Tikhonov regularization method was adopted to solve the above inverse model to eliminate the ill-conditioning influence of the inverse model. A mockup was designed to verify the proposed method. The results show that the calculation accuracy is satisfying and the remanent magnetic field can be reconstructed efficiently by the proposed method.%船舶铁磁材料磁化历史的复杂性及其不可预知性使得船舶固定磁场计算一直是船舶磁隐身中的技术难题.针对船舶固定磁场重建与分解问题,提出了一种基于磁场积分法和Tikhonov正则化方法的铁磁物体固定磁场重建与分解新方法.首先通过测量得到了船舶下方空间若干场点处的磁场值,并以正问题形式计算得到了地磁场作用下船舶在测量场点处的感应磁场值;后基于测量场点处的磁场测量数据和所计算的感应磁场数据,建立船舶固定磁场反演计算模型,并采用Tikhonov正则化方法对反演模型进行求解,以克服反演模型病态性的影响.设计船舶固定磁场的计算实例,结果证明该方法具有较好地计算精度,能够有效实现船舶固定磁场的重建与分解.

  7. Competing magnetic anisotropies in obliquely deposited thin permalloy film

    Energy Technology Data Exchange (ETDEWEB)

    Belyaev, B.A. [Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation); Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, 50/38, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Reshetnev Siberian State Aerospace University, 31, pr. Imeni Gazety “Krasnoyarskii Rabochii”, Krasnoyarsk 660014 (Russian Federation); Izotov, A.V. [Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation); Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, 50/38, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Solovev, P.N., E-mail: platon.solovev@gmail.com [Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation)

    2016-01-15

    Distribution of the magnetic anisotropy in thin film prepared by thermal vacuum oblique deposition of permalloy with small off-normal angle of incident in the presence of an external magnetic field has been studied by ferromagnetic resonance technique. On local area of the sample, a mutual compensation of near orthogonal in-plane uniaxial magnetic anisotropies induced by oblique deposition and by applied magnetic field has been found. Moreover, in addition to the uniaxial (twofold) magnetic anisotropy, fourfold and sixfold magnetic anisotropies have been observed in the sample. To explain the obtained high-order anisotropies, we assumed that the sample has exchange coupled adjacent regions or phases with different parameters of magnetic anisotropy. The results of the micromagnetic analysis of a two-layer model of the sample confirm the hypothesis.

  8. Magnetic properties of Sm-Co thin films grown on MgO(100) deposited from a single alloy target

    Energy Technology Data Exchange (ETDEWEB)

    Verhagen, T. G. A.; Boltje, D. B.; Ruitenbeek, J. M. van; Aarts, J., E-mail: aarts@physics.leidenuniv.nl [Huygens-Kamerlingh Onnes Laboratorium, Universiteit Leiden, P.O. Box 9504, 2300 RA Leiden (Netherlands)

    2014-08-07

    We have grown epitaxial Sm-Co thin films by sputter deposition from a single alloy target with a nominal SmCo{sub 5} composition on Cr(100)-buffered MgO(100) single-crystal substrates. By varying the Ar gas pressure, we can change the composition of the film from a SmCo{sub 5}-like to a Sm{sub 2}Co{sub 7}-like phase. The composition, crystal structure, morphology, and magnetic properties of these films have been determined using Rutherford Backscattering, X-ray diffraction, and magnetization measurements. We find that we can grow films with, at room temperature, coercive fields as high as 3.3 T, but with a remanent magnetization which is lower than can be expected from the texturing. This appears to be due to the Sm content of the films, which is higher than expected from the content of the target, even at the lowest possible sputtering pressures. Moreover, we find relatively large variations of film properties using targets of nominally the same composition. At low temperatures, the coercive fields increase, as expected for these hard magnets, but in the magnetization, we observe a strong background signal from the paramagnetic impurities in the MgO substrates.

  9. Magnetic properties of Sm-Co thin films grown on MgO(100) deposited from a single alloy target

    Science.gov (United States)

    Verhagen, T. G. A.; Boltje, D. B.; van Ruitenbeek, J. M.; Aarts, J.

    2014-08-01

    We have grown epitaxial Sm-Co thin films by sputter deposition from a single alloy target with a nominal SmCo5 composition on Cr(100)-buffered MgO(100) single-crystal substrates. By varying the Ar gas pressure, we can change the composition of the film from a SmCo5-like to a Sm2Co7-like phase. The composition, crystal structure, morphology, and magnetic properties of these films have been determined using Rutherford Backscattering, X-ray diffraction, and magnetization measurements. We find that we can grow films with, at room temperature, coercive fields as high as 3.3 T, but with a remanent magnetization which is lower than can be expected from the texturing. This appears to be due to the Sm content of the films, which is higher than expected from the content of the target, even at the lowest possible sputtering pressures. Moreover, we find relatively large variations of film properties using targets of nominally the same composition. At low temperatures, the coercive fields increase, as expected for these hard magnets, but in the magnetization, we observe a strong background signal from the paramagnetic impurities in the MgO substrates.

  10. Separated CoFe{sub 2}O{sub 4}/CoFe nanoparticles by the SiO{sub x} matrix: revealing the intrinsic origin for the small remanence magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Geng, B. Q.; Ma, Y. Q., E-mail: yqma@ahu.edu.cn; Xu, Y. F.; Xu, S. T.; Sun, X.; Zheng, G. H.; Dai, Z. X. [Anhui University, Anhui Key Laboratory of Information Materials and Devices, School of Physics and Materials Science (China)

    2015-07-15

    In order to clarify the intrinsic reason for the smaller remanence (M{sub r})-to-saturation (M{sub s}) magnetization ratio M{sub r}/M{sub s} than that expected by the Stoner–Wohlfarth model in CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanoparticles in the previous report, we first prepared well-dispersed CoFe{sub 2}O{sub 4} nanoparticles, and then they were diluted in the SiO{sub 2} matrix followed by reduction in H{sub 2} as far as possible to exclude or reduce disadvantageous variables (such as the growth and aggregation of particles and the exchange coupling between soft magnetic particles in the process of reducing) affecting magnetic properties. Such an idea has not been taken into account before to our knowledge. The analyses on the magnetic results indicate that the CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanoparticles herein reported are a pure dipolar system, in which the coercivity (H{sub c}) and M{sub r}/M{sub s} ratio are very sensitive to the anisotropy and the strength of dipolar interaction. These results signify that it is important to maintain the CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanoparticles with higher anisotropy and weaker dipolar interaction for improving M{sub r}/M{sub s} and H{sub c}. This suggestion was further confirmed by our another result wherein an M{sub r}/M{sub s} value of 0.64 was obtained even though no exchange coupling was observed in the CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanoparticles, and further work is in process. Graphical abstract: Numerous efforts have devoted to improve the values of M{sub s} and M{sub r}/M{sub s} by compositing hard CoFe{sub 2}O{sub 4} (CFO) ferrite with soft CoFe{sub 2} (CF) alloy, which unfortunately give the low M{sub r}/M{sub s} value (<0.5) even in presence of the exchange coupling. Key issues involve the preparation of CFO/CF composite. Previously the preparation of CFO/CF undergoes the synthesis of CFO and the subsequent reducing in the H{sub 2} ambient, as shown in Figure (a), while in this work well dispersed CFO

  11. Determining the Anisotropy of Remanence Tensor Using a Conventional Electromagnet: Overcoming the Hematite Problem and Correcting for Inclination Error in Redbeds

    Science.gov (United States)

    Schmidt, P. W.

    2007-12-01

    The origin of the natural remanent magnetization of sediments is often investigated by studying their anisotropy, either of magnetic susceptibility or some form of remanence. An oblate magnitude ellipsoid with a minimum principal axis aligned with the bedding pole is necessary (almost, though not sufficient) evidence for a primary depositional fabric and therefore a primary characteristic remanence. The anisotropy of isothermal remanent magnetization (IRM) can also be used to correct for inclination error (Jackson et al., GJI, 104, 95-103, 1991). While this is straightforward for magnetite bearing sediments, the experimental procedure to determine the anisotropy of remanence for hematite bearing sediments is problematical (Tauxe et al., JGR, 95, 4391-4404, 1990). The problem arises from 'magnetic memory', which for magnetite can be easily erased (reset) by alternating field (AF) demagnetization. The coercivity of hematite is prohibitively high for AF demagnetization and therefore only a fraction of the coercivity spectrum is accessible leaving a significant memory from previous exposures to high magnetic fields. By using a 14 T superconducting magnet Kodama and Dekkers (Stud. Geophys. Geod., 48, 747-766, 2004) have demonstrated that it is possible to derive the full anisotropy tensor for hematite bearing samples by imparting saturation IRMs, which activate almost the whole coercivity spectrum. While this is undoubtedly the ultimate solution to the hematite problem, such machines are not commonly available and are very expensive to operate. An alternative procedure that allows the use of more common and cheaper ~1 T electromagnets that obviates the AF demagnetization stage is to rotate the sample in the field in a manner that erases, or resets, the magnetic history so each IRM is equivalent. Admittedly, not all the coercivity spectrum is accessed, but typically something >50 percent is available compared to perhaps exercise for another axis. The effects of magnetite

  12. Magnetic and structural investigation of magnetic thin films with obliquely deposited underlayers

    CERN Document Server

    Hadley, M J

    2002-01-01

    An in-plane uniaxial magnetic anisotropy has been observed in thin Co films normally deposited onto obliquely sputtered Ta and Pt underlayers. Associated with this anisotropy is an augmented easy axis coercivity. The in-plane easy axis is, in most cases, perpendicular to the incident deposition plane. Microstructural results indicate that grains are well connected along the magnetic easy axis but are separated by long continuous voids along the hard axis, which is ascribed to a geometric shadowing effect due to the oblique incidence deposition of the underlayer. Hence, the magnetic anisotropy mimics the film growth anisotropy. It is therefore believed that the observed magnetic properties are due to magnetostatic shape anisotropy effects. In-plane coercivity and anisotropy field are shown to increase with underlayer deposition angle, underlayer thickness and magnetic layer thickness. The choice of capping layer is also observed to dramatically alter the magnetics, as did the sample temperature. In general, Pt...

  13. Electrospray deposition of isolated chemically synthesized magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Agostini, Pierre; Meffre, Anca; Lacroix, Lise-Marie; Ugnati, Damien [Université de Toulouse (France); INSA, UPS, CNRS, Laboratoire de Physique et Chimie des Nano-objets (LPCNO) (France); Ondarçuhu, Thierry [Centre d’Elaboration de Matériaux et d’Etudes Structurales (CEMES-CNRS) (France); Respaud, Marc; Lassagne, Benjamin, E-mail: lassagne@insa-toulouse.fr [Université de Toulouse (France); INSA, UPS, CNRS, Laboratoire de Physique et Chimie des Nano-objets (LPCNO) (France)

    2016-01-15

    The deposition of isolated magnetic nanoparticles onto a substrate was performed using electrohydrodynamic spraying. Two kinds of nanoparticles were sprayed, 11 nm CoFe carbide nanospheres and 10.5 nm Fe nanocubes. By studying carefully the evolution of the sprayed charged droplets and the mechanism of nanoparticle dispersion in them, we could optimize the nanoparticle concentration within the initial nanoparticle solution (i) to reduce the magnetic interaction and therefore prevent agglomeration and (ii) to obtain in a relatively short period (1 h) a deposit of isolated magnetic nanoparticles with a density of up to 400 nanoparticles per µm{sup 2}. These results open great perspectives for magnetic measurements on single objects using advanced magnetometry techniques as long as spintronics applications based on single chemically synthesized magnetic nanoparticles.

  14. A rock-magnetic study of coral skeletons: A record of African dust deposition in the Caribbean

    Science.gov (United States)

    Nigro, P. M.; Clement, B. M.; Halley, R.; Helmle, K.; Swart, P.; Dodge, R.

    2008-05-01

    Aeolian African dust from the Saharan-Sahel deserts significantly influences the climate and ecology of the Caribbean region. Large summer dust storms produce mass quantities of air-born, clay-rich material (containing significant iron-oxide components), that are transported over the Atlantic Ocean and deposited in the Caribbean. We present here the results of a rock magnetic study of cores of Scleractinian corals, including a Montastraea annularis collected in Culebra, Puerto Rico on July of 1991, a M. faveolata collected off the coast of St. Vincent (Bequia) on November of 2002, and a Siderastrea radians collected off the coast of Cape Verde on July of 2002. Thin slabs (~5mm) were cut from these cores and x-rayed to reveal annual density banding. Small samples centered over each annual high-density band were cut from the slabs. These samples were then subjected to a series of standard rock magnetic experiments, including Anhysteretic Remanent Magnetization (ARM) acquisition and demagnetization, and Isothermal Remanent Magnetization (IRM) acquisition and demagnetization. Records of both ARMs and IRMs reveal coherent signals that vary with coral age. The IRM acquisition curves demonstrate the presence of two carriers of magnetization in most samples; a low-coercivity component consistent with the presence of magnetite or maghemite and a high-coercivity component consistent with the presence of hematite. Unmixing the IRM acquisition curves differentiates the magnetic components and yields a record of high-coercivity input that we interpret as a record of African dust. Preliminary data from the M. annularis core show a link between high and low variability in the high-coercivity component when compared with the historical record of dust flux to the Caribbean and with the Soudano-Sahel Precipitation Index (SSPI) over a time period of fifty years (1941-1990). High variability is displayed from 1941 through 1950 and 1965 through 1990 whereas low variability is displayed

  15. Power deposition in superconducting magnets of the momentum cleaning insertion

    CERN Document Server

    CERN. Geneva; Baishev, I S; Jeanneret, J B; Kourotchkine, I A

    2002-01-01

    This note describes the calculation of power deposition in the superconducting magnets Q6, Q7 and MB8 downstream of the momentum collimators in IR3. To reduce a relatively high power deposition density of 1.8mW/cm^3 in the coils of Q6, we propose to install some fixed shielding collimators upstream of the warm dogleg dipoles D4.

  16. Interactions controlled evolution of complex magnetoresistance in as-deposited Ag{sub 100−x}Co{sub x} nanogranular films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Dinesh; Chaudhary, Sujeet, E-mail: sujeetc@physics.iitd.ac.in; Pandya, Dinesh K.

    2015-11-15

    Evolution of a complex magnetoresistance and dc-magnetization behavior of as-deposited co-sputtered Ag{sub 100−x}Co{sub x} films with the variation of cobalt concentration ‘x’ from 25.2 to 45.1 at% is presented. At 20 K, a transition from normal to complex magnetoresistance behavior, in conjunction with magnetic force microscopy evidence of the existence of a magnetic microstructure resulting in perpendicular magnetic anisotropy (PMA) is observed for x=32.6 cobalt concentration film. The dc-magnetization studies provide additional support to the presence of PMA in film that gets reduced with the increase of cobalt concentration. The complex magnetoresistance (MR) behavior also decreases with the increase of ‘x’. The room temperature MR, coercivity behavior and remanence to saturation magnetization ratio indicate the presence of direct ferromagnetic interactions due to the presence of ferromagnetic particles for x≥32.6 films. The observed complex MR behavior and presence of PMA are interpreted in terms of manifestation of the transition of interparticle magnetic interaction nature from dipolar to direct ferromagnetic. - Highlights: • Complex MR with perpendicular magnetic anisotropy (PMA) is observed. • MFM evidenced the presence of PMA. • Complex MR and PMA decreases with the increase of cobalt concentration. • Observed results are correlated with the nature of magnetic interactions.

  17. Magnetic Phases of Sputter Deposited Thin-Film Erbium

    Science.gov (United States)

    Witt, J. D. S.; Cooper, J. F. K.; Satchell, N.; Kinane, C. J.; Curran, P. J.; Bending, S. J.; Langridge, S.; Heyderman, L. J.; Burnell, G.

    2016-12-01

    We present a detailed structural and magnetic characterization of sputter deposited thin film erbium, determined by x-ray diffraction, transport measurements, magnetometry and neutron diffraction. This provides information on the onset and change of the magnetic state as a function of temperature and applied magnetic field. Many of the features of bulk material are reproduced. Also of interest is the identification of a conical magnetic state which repeats with a wavevector parallel to the c axis τc = 4/17 in units of the reciprocal lattice parameter c*, which is a state not observed in any other thin film or bulk measurements. The data from the various techniques are combined to construct magnetic field, temperature (H, T)–phase diagrams for the 200 nm-thick Er sample that serves as a foundation for future exploitation of this complex magnetic thin film system.

  18. Paleomagnetism of the Red Dog Zn-Pb massive sulfide deposit in northern Alaska

    Science.gov (United States)

    Lewchuk, Michael T.; Leach, D.L.; Kelley, K.D.; Symons, David T. A.

    2004-01-01

    Paleomagnetic methods have isolated two ancient magnetizations in and around the Paleozoic shale-hosted Red Dog ore deposit in northern Alaska. A high-latitude, westerly magnetization carried by magnetite, termed characteristic remanent magnetization A, was found in rocks that have barite and/or substantial quartz replacement of barite. An intermediate- to low-latitude, southerly magnetization (characteristic remanent magnetization B) is carried by pyrrhotite and was found in rocks dominated by galena and sphalerite. The ages the two components are constrained by their relationship with geochemistry, radiometric age dating, and hypotheses for the Mesozoic tectonic history of the Brooks Range. Characteristic remanent magnetization A fails the fold test so it must postdate the end of Brookian orogenesis (??? 150 Ma). It is always found with replacement quartz that has a radiometric date (white mica from a vug, 39Ar/40Ar) of 126 Ma. The paleolatitude for characteristic remanent magnetization B is too shallow to be Mesozoic or younger, regardless of the model for the tectonic origin of northern Alaska, and must predate Brookian orogenesis. Geologic mapping suggests that most of the ore is syngenetic, formed at 330 to 340 Ma, and a radiometric date (Re-Os on pyrite) yields an age of 338 Ma. Since characteristic remanent magnetization B predates deformation, is found in mineralized rocks and is carried by pyrrhotite, it was probably acquired during the mineralizing process as well. The combined radiometric ages and paleomagnetic data sets can be best interpreted by assuming that northern Alaska was part of an accreted terrane that was translated northward by about 30?? into its current location relative to the rest of North America and then rotated counterclockwise by 50?? to 70??. This tectonic interpretation yields plausible magnetization ages for both characteristic remanent magnetization A and B. Geologic evidence, isotopic ages, and paleomagnetic data indicate

  19. Thickness dependence of magnetic properties and giant magneto-impedance effect in amorphous Co73Si12B15 thin films prepared by Dual-Ion beam assisted deposition

    Science.gov (United States)

    Zhang, Yu; Wang, San-sheng; Hu, Teng; He, Tong-fu; Chen, Zi-yu; Yi, Zhong; Meng, Li-Fei

    2017-03-01

    Dual-Ion Beam Assisted Deposition is a suitable method for the preparation of giant magneto-impedance (GMI) materials. In this paper, Co73Si12B15 thin films with different thicknesses were prepared by Dual-Ion Beam Assisted Deposition, and the influences of film thickness on magnetic properties and GMI effect were investigated. It was found that the asymmetric magnetic hysteresis loop in the prepared Co73Si12B15 thin films occurs at ambient temperature, and the shift behavior of hysteresis loop associated with film thickness. With the film thickness increasing, the values of shift field and coercive field and other parameters such as remanence and shift ratio appeared complex variation. At a certain frequency, the large GMI effect is only observed in some films, which have good magnetic properties including low coercivity, low remanence ratio and high shift ratio. The results indicated that the thickness dependence of magnetic properties nonlinearly determined the GMI effect in Co73Si12B15 thin films.

  20. Study of magnetic behavior in hexagonal-YMn{sub 1−x}Fe{sub x}O{sub 3} (x=0 and 0.2) nanoparticles using remanent magnetization curves

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Samta; Singh, Amit Kumar; Srivastava, Saurabh Kumar; Chandra, Ramesh, E-mail: ramesfic@iitr.ac.in

    2016-09-15

    We have studied the magnetic behavior of YMn{sub 1−x}Fe{sub x}O{sub 3} (x=0 and 0.2) nanoparticles synthesized by conventional solid state reaction method. The as-synthesized nanoparticles were found to have hexagonal phase with P6{sub 3cm} space group confirmed by X-Ray diffraction. The particle size was found to be ~70 nm as confirmed by both X-Ray diffraction and Transmission Electron Microscopy. DC magnetization and memory effect measurements imply that the h-YMnO{sub 3} nanoparticles bear a resemblance to super spin-glass state following de Almeida–Thouless like behavior which is being suppressed by Fe-doping. The Fe-doping in YMnO{sub 3} enhances the antiferromagnetic (AFM) transition temperature T{sub N} to ~79 K and induces a new magnetic state due to the surface spins which is realized as diluted antiferromagnet in a field (DAFF) as explored by the thermoremanent and isothermoremanent magnetization measured with different applied magnetic field. - Highlights: • Magnetic behavior of h-YMn{sub 1−x}Fe{sub x}O{sub 3} (x=0 and 0.2) nanoparticles have been studied. • The nanoparticles (~70 nm) were synthesized by solid state reaction method. • Magnetic data reveal spin-glass behavior in YMnO{sub 3} which was suppressed in YMn{sub 0.8}Fe{sub 0.2}O{sub 3}. • The h-YMnO{sub 3} nanoparticles show memory effect and obey de-Almeida Thouless line. • TRM and IRM suggest spin glass nature for YMnO{sub 3}, while the YMn{sub 0.8}Fe{sub 0.2}O{sub 3} resembles DAFF.

  1. Remanence anisotropy effect on the palaeointensity results obtained from various archaeological materials, excluding pottery

    Science.gov (United States)

    Kovacheva, M.; Chauvin, A.; Jordanova, N.; Lanos, P.; Karloukovski, V.

    2009-06-01

    The effect of magnetic anisotropy on the palaeointensity results has been evaluated in different materials, including samples from archaeological structures of various ages, such as baked clay from prehistoric domestic ovens or pottery kilns, burnt soil from ancient fires, and bricks and bricks or tiles used in the kiln's construction. The remanence anisotropy was estimated by the thermoremanent (TRM) anisotropy tensor and isothermal remanence (IRM) tensor methods. The small anisotropy effect (less than 5%) observed in the palaeointensity results of baked clay from the relatively thin prehistoric oven's floors estimated previously through IRM anisotropy was confirmed by TRM anisotropy of this material. The new results demonstrate the possibility of using IRM anisotropy evaluation to correct baked clay palaeointensity data instead of the more difficult to determine TRM anisotropy ellipsoid. This is not always the case for the palaeointensity results from bricks and tiles. The anisotropy correction to palaeointensity results seems negligible for materials other than pottery. It would therefore appear that the palaeointensity determination is more sensitive to the degree of remanence anisotropy P and the angle between the natural remanent magnetization (NRM) vector and the laboratory field direction, than to the angle between the NRM and the maximum axis of the remanence anisotropy ellipsoid (Kmax).

  2. 超导磁体剩余磁场对软磁材料测试的影响%Effect of sup erconducting magnet remanence on the soft magnetic material measurements

    Institute of Scientific and Technical Information of China (English)

    于红云

    2014-01-01

    超导磁体体积小,能够获得强磁场,磁场稳定度、均匀度很高,因此,在磁学测量设备中应用很广泛.美国Quantum Design公司的高精度磁学测量系统采用的就是超导磁体,最高磁场能够达到7 T.由于超导磁体材料本身缺陷的钉扎作用,在磁体退磁后,磁体内部有剩余磁场,有时能够大于30 Oe.由此产生的磁场误差将导致测试的矫顽力、剩磁等数据不准确,甚至导致反向的磁滞回线.设置的磁场初始值不同,剩余磁场的大小也不同;初始磁场越大,剩余磁场越大.这种剩余磁场效应在软磁材料测试过程中表现得尤为明显,产生的测试误差不可忽略,必须进行磁场误差修正才能得到正确的结果.本文阐明了超导磁体产生剩余磁场的原因、影响因素和规律,详述了测试软磁材料可能遇到的问题,并给出解决方法.%The superconducting magnet is used to provide magnetic field in a magnetic property measurement system (SQUID-VSM, Quantum Design), since it can provide high magnetic field up to 7 T. Due to the pinned magnetic flux, there is residual magnetic field as the magnetic field is set to be 0 from high field. There appears an error between the reported filed and the real filed. Sometimes, the residual magnetic field can be more than 30 Oe. It is so large that it may provide incorrect experiment data, such as Hc, Mr and inverted hysteresis loops. The effect of residual magnetic field on the soft magnetic material measurements should not be neglected. The residual magnetic field is dependent on initial magnetic field. The experimental data must be corrected by measuring the standard sample. In the paper we investigate the origin and the regular pattern of the residual magnetic field. The effects on the measurement results and the correction method are presented.

  3. Thermodetrital and crystallodetrital magnetization in an Icelandic hyaloclastite

    Science.gov (United States)

    Goguitchaichvili, Avto; PréVot, Michel; Dautria, Jean-Marie; Bacia, Maria

    1999-12-01

    An Icelandic hyaloclastite, mostly composed of millimetric fragments of basaltic glass, that is fresh at the bottom of the unit but largely palagonitized in the upper part, has been studied by petrologic, mineralogical, and magnetic means, with the aim of determining the nature and characteristics of the natural remanent magnetization (NRM). The NRM was generally found to consist of two components: a thermodetrital remanent magnetization (thermo-DRM) and a crystallodetrital remanent magnetization (crystallo-DRM). Thermo DRM and crystallo-DRM are defined here as the remanences acquired as a result of the deposition of magnetic particles of detrital origin individually carrying either a TRM (thermoremanent magnetization) or a CRM (crystallization remanent magnetization), respectively. Regardless of the chemistry and size and of these particles, Thellier experiments carried out on samples carrying a thermo-DRM provide apparent paleointensities close to the expected geomagnetic paleointensity, which suggests that in the present case the fractional alignment of individual magnetic moments is similar for DRM and TRM. In the upper part of this outcrop, grain growth CRM was acquired by individual grains of magnetite which crystallized as a result of palagonitization of basaltic glass at low temperature (cases, the overall remanence exhibits a large inclination error (˜20°), and the samples have a marked anisotropy of magnetic susceptibility which is typical of sedimentary fabrics. Thus, secondary magnetite probably formed prior to the deposition of particles, and the bulk remanence in the palagonitized layers is a crystallo-DRM rather than a CRM. Throughout the entire stratigraphic thickness, Thellier paleointensity data are of good or excellent quality regardless of the nature of the primary remanence. In agreement with previous theoretical inferences and experimental results the layers carrying a crystallo-DRM provide a much lower (by a factor of 2) apparent

  4. Interactions controlled evolution of complex magnetoresistance in as-deposited Ag100-xCox nanogranular films with perpendicular magnetic anisotropy

    Science.gov (United States)

    Kumar, Dinesh; Chaudhary, Sujeet; Pandya, Dinesh K.

    2015-11-01

    Evolution of a complex magnetoresistance and dc-magnetization behavior of as-deposited co-sputtered Ag100-xCox films with the variation of cobalt concentration 'x' from 25.2 to 45.1 at% is presented. At 20 K, a transition from normal to complex magnetoresistance behavior, in conjunction with magnetic force microscopy evidence of the existence of a magnetic microstructure resulting in perpendicular magnetic anisotropy (PMA) is observed for x=32.6 cobalt concentration film. The dc-magnetization studies provide additional support to the presence of PMA in film that gets reduced with the increase of cobalt concentration. The complex magnetoresistance (MR) behavior also decreases with the increase of 'x'. The room temperature MR, coercivity behavior and remanence to saturation magnetization ratio indicate the presence of direct ferromagnetic interactions due to the presence of ferromagnetic particles for x≥32.6 films. The observed complex MR behavior and presence of PMA are interpreted in terms of manifestation of the transition of interparticle magnetic interaction nature from dipolar to direct ferromagnetic.

  5. Effects of an external magnetic field in pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, T. [Universidad Autonoma de la Ciudad de Mexico (UACM), Prolongacion San Isidro 151, Col. San Lorenzo Tezonco, C.P. 09790, Mexico DF (Mexico)], E-mail: tupacgarcia@yahoo.com; Posada, E. de [CINVESTAV-IPN Unidad Merida, Applied Physics Department, A.P. 73, Cordemex, C.P. 97130 Merida, Yuc. (Mexico); Villagran, M. [CCADET, Universidad Nacional Autonoma de Mexico (UNAM), A.P. 70-186, C.P. 04510, Mexico DF (Mexico); Ll, J.L. Sanchez [Laboratorio de Magnetismo, Facultad de Fisica-IMRE, Universidad de La Habana, La Habana 10400 (Cuba); Bartolo-Perez, P.; Pena, J.L. [CINVESTAV-IPN Unidad Merida, Applied Physics Department, A.P. 73, Cordemex, C.P. 97130 Merida, Yuc. (Mexico)

    2008-12-30

    Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe{sub 12}O{sub 19} target with and without the presence of a nonhomogeneous magnetic field of {mu}{sub 0}H = 0.4 T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd-Fe-B permanent magnet and the substrate was just placed on the magnet surface (Aurora method). An appreciable increment of optical emission due to the presence of the magnetic field was observed, but no film composition change or thickness increment was obtained. It suggests that the increment of the optical emission is due mainly to the electron confinement rather than confinement of ionic species.

  6. Tailoring out-of-plane magnetic properties of pulsed laser deposited FePt thin films by changing laser energy fluence

    Science.gov (United States)

    Wang, Ying; Tan, T. L.; Tan, K. S.; Lee, P.; Liu, Hai; Yadian, Boluo; Hu, Ge; Huang, Yizhong; Ramanujan, R. V.; Rawat, R. S.

    2014-10-01

    Magnetic properties of pulsed laser deposited (PLD) FePt thin films are investigated at three different laser energy fluences of 51, 136 and 182 J/cm2. Deposition at lower laser energy fluence (51 J/cm2) yields softer out-of-plane coercivity (≤0.4 kG), whereas deposition at higher laser energy fluence (136 and 182 J/cm2) results in harder out-of-plane coercivity (≥5.0 kG). The improved coercivity is found to be attributed to the formation of vacancy defects in thin films, which is indicated by stress change from tensile to compressive form with increasing laser energy fluence. Maximum out-of-plane saturated magnetization of 615 emu/cm3 and remanent squareness ratio of 0.88 are achieved for 16 nm thick FePt thin films deposited at moderate laser energy fluence of 136 J/cm2, making them suitable for high density perpendicular data storage applications.

  7. A first paleomagnetic and rock magnetic investigation of calcareous nodules from the Chinese Loess Plateau

    Science.gov (United States)

    Yang, T.; Hyodo, M.; Yang, Z.; Sun, Z.

    2005-01-01

    A detailed paleomagnetic and rock magnetic investigation was carried out on calcareous nodule layers embed-ded in the loess-paleosol sequences near Baoji city, southern Chinese Loess Plateau. The anisotropy of low-field magnetic susceptibility confirms that calcareous nodules retain the primary sedimentary fabric of original de-posits. Rock magnetic properties demonstrate that calcareous nodules have the same mineralogy and grain sizes as loess-paleosol deposits. Characteristic remanent magnetizations of calcareous nodules have directions consis-tent with those of adjacent loess and paleosol deposits. The Punaruu event, previously found from loess deposits in the upper part of loess unit L13 in Weinan, southern Chinese Loess Plateau, is observed at the corresponding stratigraphic level in the calcareous nodule layer. These observations indicate that the calcareous nodule layers preserve primary remanent magnetizations of original deposits before calcification, and that they can contribute to paleomagnetic studies in the Chinese Loess Plateau.

  8. TECHNOLOGY OF ARTIFICIAL DEPOSIT PRESERVATION AT THE KURSK MAGNETIC ANOMALY

    Directory of Open Access Journals (Sweden)

    Maria A. Pashkevich

    2016-09-01

    Full Text Available An evaluation of existing insulation and remediation technologies for solid mineral waste storages is carried out. Results of field observations at one of the largest tailings in Russia are given. A quality of atmospheric air, and surface and ground water are estimated in the impact areas of a magnetic separation waste storage at an iron ore deposit of the Kursk Magnetic Anomaly. An effective method of landfill’s surface insulation using polymeric materials is offered. The technological insulation process by means of a self-propelled screening machine is described. The suggested method will allow preserving an artificial deposit until the time of its rational mining, stopping water and wind erosion from its surface. Environmental conditions in its location area will be improved and pollution of atmosphere, soil, and natural water will be reduced.

  9. Unravelling the magnetic record in marine and continental sediments : climatic versus geomagnetic signals

    NARCIS (Netherlands)

    Kruiver, Pauline Pascal

    2001-01-01

    Magnetic iron oxides and iron sulfides are present as trace constituents in sediments. These magnetic particles can carry a natural remanent magnetisation (NRM). When the sediment consolidates and lithifies after deposition, the direction of the then ambient field is preserved. The amount of

  10. Unravelling the magnetic record in marine and continental sediments : climatic versus geomagnetic signals

    NARCIS (Netherlands)

    Kruiver, Pauline Pascal

    2001-01-01

    Magnetic iron oxides and iron sulfides are present as trace constituents in sediments. These magnetic particles can carry a natural remanent magnetisation (NRM). When the sediment consolidates and lithifies after deposition, the direction of the then ambient field is preserved. The amount of magneti

  11. The Research and Development of the External Magnetic Field Acting on Electro-Deposition Process

    OpenAIRE

    Wu Menghua; Jia Weiping

    2016-01-01

    The research and development status of the electro-deposition technology under the action of external magnetic field are introduced. The basic characteristics and applied manners of external magnetic field in electro-deposition process are summarized. The acting principle of external magnetic field, the effects of magnetic hydrodynamics (MHD) caused by the Lorentz force, and the acting of magnetic force on the metal ions and particles are described. The main actions of external magnetic field...

  12. Low temperature magnetic characterisation of fire ash residues

    Science.gov (United States)

    Peters, C.; Thompson, R.; Harrison, A.; Church, M. J.

    Fire ash is ideally suited to mineral magnetic studies. Both modern (generated by controlled burning experiments) and archaeological ash deposits have been studied, with the aim of identifying and quantifying fuel types used in prehistory. Low temperature magnetic measurements were carried out on the ash samples using an MPMS 2 SQUID magnetometer. The low temperature thermo-remanence cooling curves of the modern ash display differences between fuel sources. Wood and well-humified peat ash display an increase in remanence with cooling probably related to a high superparamagnetic component, consistent with room temperature frequency dependent susceptibilities of over 7%. In comparison fibrous-upper peat and peat turf display an unusual decrease in remanence, possibly due to an isotropic point of grains larger than superparamagnetic in size. The differences have been successfully utilised in unmixing calculations to quantify fuel components within four archaeological deposits from the Northern and Western Isles of Scotland.

  13. Focused electron beam induced deposition of magnetic nanostructures

    Science.gov (United States)

    de Teresa, Jose M.

    2011-03-01

    Nanopatterning strategies of magnetic materials normally rely on standard techniques such as electron-beam lithography using electron-sensitive resists. Focused electron beam induced deposition (FEBID) is currently being investigated as an alternative single-step route to produce functional magnetic nanostructures. Thus, Co-based and Fe-based precursors have been recently investigated for the growth of magnetic nanostructures by FEBID. In the present contribution, I will give an overview of the existing literature on magnetic nanostructures by FEBID and I will focus on the growth of Co nanostructures by FEBID using Co 2 (CO)8 as precursor gas. The Co content in the nanostructures can reach 95%. Magnetotransport experiments indicate that full metallic behaviour is displayed with relatively low residual resistivity and standard anisotropic magnetoresistance (0.8%). The coercive field of nanowires with changing aspect ratio has been determined in nanowires with width down to 150 nm by means of Magneto-optical Kerr Effect and the magnetization reversal has been imaged by means of Magnetic Force Microscopy, Scanning Transmission X-ray Microscopy as well as Lorentz Microscopy experiments. Nano-Hall probes have been grown with remarkable minimum detectable magnetic flux. Noticeably, it has been found that the domain-wall propagation field is lower than the domain-wall nucleation field in L-shaped nanowires, with potential applications in magnetic logic, sensing and storage. The spin polarization of these Co nanodeposits has been determined through Andreev-Reflection experiments in ferromagnetic-superconducting nanocontacts and amounts to 35%. Recent results obtained in Fe-based nanostructures by FEBID using Fe 2 (CO)9 precursor will be also presented. I acknowledge the collaboration in this field with A. Fernandez-Pacheco, R. Cordoba, L. Serrano, S. Sangiao, L.A. Rodriguez, C. Magen, E. Snoeck, L. Morellon, M.R. Ibarra.

  14. Environmental studies in two communes of Santiago de Chile by the analysis of magnetic properties of particulate matter deposited on leaves of roadside trees

    Science.gov (United States)

    Muñoz, David; Aguilar, Bertha; Fuentealba, Raúl; Préndez, Margarita

    2017-03-01

    Emissions from motor vehicles are considered to be one of the main sources of airborne particulate matter in Santiago. International researchers have shown that particulate matter contains metal oxides and magnetic particles, both of which are emitted mainly from vehicles exhaust pipes. On the other hand, trees are effective in reducing such contamination, so that they act as passive collectors of particulate matter. This work presents the results obtained from the first magnetic study of the particulate matter collected in two areas of the city of Santiago de Chile. Magnetic susceptibility and Saturation Isothermic Remanent Magnetization (SIRM) were determined in leaves from abundant urban trees and from urban dust samples. Results indicate that most of the samples contain ferromagnetic minerals with magnetite (Fe3O4) as the main carrier. Values of magnetic susceptibility (SI ×10-6 m3/kg) in the range 0.04-0.24 for leaves and in the range 10-45 for urban dust were determinated. In one of the city areas studied, significant correlation between the particulate matter deposited on leaves of Platanus orientalis and measured traffic flows was obtained. In addition, it was possible to estimate that the species Platanus orientalis and Acer negundo have a better ability to capture particulate matter than the species Robinia pseudoacacia.

  15. Magnetic resonance imaging of iron deposition in neurological disorders.

    Science.gov (United States)

    Brass, Steven D; Chen, Nan-kuei; Mulkern, Robert V; Bakshi, Rohit

    2006-02-01

    Deposition of iron in the brain is proposed to play a role in the pathophysiology of the normal aging process and neurodegenerative diseases. Whereas iron is required for normal neuronal metabolism, excessive levels can contribute to the formation of free radicals, leading to lipid peroxidation and neurotoxicity. Magnetic resonance imaging (MRI) is a powerful tool to detect excessive iron in the brain and longitudinally monitor changes in iron levels. Iron deposition is associated with a reduction in the T2 relaxation time, leading to hypointensity on spin-echo and gradient-echo T2-weighted images. The MRI changes associated with iron deposition have been observed both in normal aging and in various chronic neurological diseases, including multiple sclerosis, Alzheimer disease, and Parkinson disease. Magnetic resonance imaging metrics providing information about iron concentrations include R2, R2', and R2*. The purpose of this review is to discuss the role of iron and its detection by MRI in various neurological disorders. We will review the basic biochemical properties of iron and its influence on MRI signal. We will also summarize the sensitivity and specificity of MRI techniques in detecting iron. The MRI and pathological findings pertaining to brain iron will be reviewed with respect to normal aging and a variety of neurological disorders. Finally, the biochemistry and pathophysiology surrounding iron, oxidative stress, free radicals, and lipid peroxidation in the brain will be discussed, including therapeutic implications. The potential role of iron deposition and its assessment by MRI provides exciting potential applications to the diagnosis, longitudinal monitoring, and therapeutic development for disorders of the brain.

  16. Striped domains of coarse-grained magnetite observed by X-ray photoemission electron microscopy as a source of the high remanence of granites in the Vredefort dome

    Directory of Open Access Journals (Sweden)

    Hiroto eKubo

    2015-06-01

    Full Text Available The characteristics of a coarse-grained high-remanence magnetite obtained from shocked Vredefort granite were investigated by X-ray magnetic circular dichroism (XMCD analysis and X-ray absorption spectroscopy (XAS. The study utilized a spectroscopic photoelectron low-energy electron emission microscope (SPELEEM and was conducted in the SPring-8 large-synchrotron radiation facility. It is generally believed that the strong and stable bulk remanence of Vredefort granites is due to the presence of minerals that have been strongly magnetized by either an impact-generated magnetic field or terrestrial lightning strikes. Although coarse-grained magnetite is traditionally characterized by weak coercivity and remanence, the specimen used in the present study exhibited high coercivity and an intense remanent magnetization. The presence of hematite lamellae observed on the partially oxidized magnetite specimen indicated an array of striped domains, intensifying a remanence and coercivity. We also conducted XAS and XMCD analyses on a natural lodestone permanent magnet produced by lightning strikes; while maghemite was found to be present, no magnetic domain structures were observed. Considering that the nucleation of hematite lamellae on magnetite/maghemite grains is due to high-temperature oxidation, we attribute the intense remanent magnetization and magnetic hardening of Vredefort granites to post-impact hydrothermal activity.

  17. Magnetic properties and magnetization reversal of α-Fe nanowires deposited in alumina film

    Science.gov (United States)

    Peng, Yong; Zhang, Hao-Li; Pan, Shan-Lin; Li, Hu-Lin

    2000-05-01

    Uniform arrays of Fe nanowires were prepared by electrochemical deposition of iron into nanoporous anodic aluminum oxide films. The microstructure and crystal structures of the nanowires were studied by transmission electron microscopy and electron diffraction. It was found that each nanowire looked like a chain of dots and each dot in the chain was supposed to be a single crystal of α-Fe. Each dot was shown to be a single magnetic domain. The magnetic properties of a uniform array of Fe nanowires and the magnetization reversal in a Fe nanowire were investigated by Mössbauer spectroscopy and vibrating sample magnetometry, which demonstrated that the film of Fe nanowires in alumina had superior perpendicular magnetic characteristics. The magnetic studies also revealed that the moments of each single domain dot were oriented along the chain. Experimental results could be interpreted by the reversal model of "chains of spheres" with the symmetric fanning mechanism.

  18. Remanent resistance changes in metal- PrCaMnO-metal sandwich structures

    Energy Technology Data Exchange (ETDEWEB)

    Scherff, Malte; Meyer, Bjoern-Uwe; Scholz, Julius; Hoffmann, Joerg; Jooss, Christian [Institute of Materials Physics, University of Goettingen (Germany)

    2012-07-01

    The non-volatile electric pulse induced resistance change (EPIR) seems to be a rather common feature of oxides sandwiched by electrodes. However, microscopic mechanisms are discussed controversially. We present electrical transport measurements of sputtered Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3} films sandwiched by metallic electrodes with variation of electrode materials, device geometry and PCMO deposition parameters. Cross-plane transport measurements have been performed as function of temperature and magnetic field. Specifically, the transition from dynamic resistance changes due to non-linear transport to remanent switching is analyzed. By analyzing changes of magneto-resistance at low temperatures in different resistance states we aim for separation between interface and film contributions to switching. Comparing switching behavior in symmetric and asymmetric electrode configuration allows for identification of the active, single interface in the switching process and the origin of an observed switching polarity inversion. The influence of excitation field and power on the switching characteristics of different noble metal electrodes is discussed. Samples from macroscopic devices and in situ stimulated sandwich structures were studied in a transmission electron microscope in order to investigate the induced structural, chemical and electronic changes.

  19. SQUID measurements of remanent magnetisation in refillable 3He spin-filter cells (SFC)

    Science.gov (United States)

    Hutanu, V.; Rupp, A.; Sander-Thömmes, T.

    2007-07-01

    A strong influence of external magnetic fields on the relaxation time constant T1 of glass cells serving as reservoirs for polarised 3He, observed for various alkali metal-coated cells made of different glass types, was initially associated with the presence of a large number of ferromagnetic clusters on the glass surface. Later experiments showed the presence of the so-called “ T1 hysteresis” phenomenon with a similar distinctiveness also in uncoated cells made of pure synthetic quartz glass. It suggests that the origin of such a relaxation is a macroscopic magnetisation in the bulk of the cell. We present the results of a multi-SQUID system investigation on magnetised and non-magnetised quartz glass cells, Cs coated as well as bare wall, to be used as neutron spin filters at HMI Berlin. The presence of a macroscopic remanent magnetic moment in the cells after their exposition to external magnetic fields has been experimentally shown. More than 80% of the remanent magnetic moment of the magnetised cells was found to be concentrated in the region of the glass valves. SQUID measurements reveal the existence of some remanent magnetisation in all valve parts and also in the vacuum grease, but most magnetic are the plastic parts and the O-ring. Different valve and sealing types have been compared in order to find the less magnetisable one.

  20. SQUID measurements of remanent magnetisation in refillable {sup 3}He spin-filter cells (SFC)

    Energy Technology Data Exchange (ETDEWEB)

    Hutanu, V. [Hahn-Meitner-Institut Berlin, Department SF2, Glienicker Str. 100, D-14109 Berlin (Germany)]. E-mail: vladimir.hutanu@frm2.tum.de; Rupp, A. [Hahn-Meitner-Institut Berlin, Department SF2, Glienicker Str. 100, D-14109 Berlin (Germany); Sander-Thoemmes, T. [Physikalisch-Technische Bundesanstalt, Abbestr. 10-12, D-10587 Berlin (Germany)

    2007-07-15

    A strong influence of external magnetic fields on the relaxation time constant T {sub 1} of glass cells serving as reservoirs for polarised {sup 3}He, observed for various alkali metal-coated cells made of different glass types, was initially associated with the presence of a large number of ferromagnetic clusters on the glass surface. Later experiments showed the presence of the so-called 'T {sub 1} hysteresis' phenomenon with a similar distinctiveness also in uncoated cells made of pure synthetic quartz glass. It suggests that the origin of such a relaxation is a macroscopic magnetisation in the bulk of the cell. We present the results of a multi-SQUID system investigation on magnetised and non-magnetised quartz glass cells, Cs coated as well as bare wall, to be used as neutron spin filters at HMI Berlin. The presence of a macroscopic remanent magnetic moment in the cells after their exposition to external magnetic fields has been experimentally shown. More than 80% of the remanent magnetic moment of the magnetised cells was found to be concentrated in the region of the glass valves. SQUID measurements reveal the existence of some remanent magnetisation in all valve parts and also in the vacuum grease, but most magnetic are the plastic parts and the O-ring. Different valve and sealing types have been compared in order to find the less magnetisable one.

  1. Can a primary remanence be retrieved from partially remagnetized Eocence volcanic rocks in the Nanmulin Basin (southern Tibet) to date the India-Asia collision?

    National Research Council Canada - National Science Library

    Huang, Wentao; Dupont-Nivet, Guillaume; Lippert, Peter C; van Hinsbergen, Douwe J J; Dekkers, Mark J; Guo, Zhaojie; Walip, Ross; Li, Xiaochun; Zhang, Xiaoran; Liu, Dongdong; Kapp, Paul

    2015-01-01

    ...). New zircon U-Pb dates indicate an age of ~52Ma. Negative fold tests, however, demonstrate that the isolated characteristic remanent magnetizations, with notably varying inclinations, are not primary...

  2. Microstructural evolution and magnetic properties in Fe{sub 50}Pd{sub 50} sputtered thin films submitted to post-deposition annealing

    Energy Technology Data Exchange (ETDEWEB)

    Tiberto, P., E-mail: paola.tiberto@inrim.it [INRIM, Electromagnetism Division, Strada delle Cacce 91, 10135 Torino (Italy); Barrera, G. [INRIM, Electromagnetism Division, Strada delle Cacce 91, 10135 Torino (Italy); Chemistry Dept., Università di Torino, Via Pietro Giuria 9, 10125 Torino (Italy); Celegato, F.; Coisson, M.; Olivetti, E.S.; Vinai, F. [INRIM, Electromagnetism Division, Strada delle Cacce 91, 10135 Torino (Italy)

    2014-12-05

    Graphical abstract: MFM images acquired at magnetisation remanence in the perpendicular configuration of selected annealed Fe{sub 50}Pd{sub 50} thin films: (a) T{sub a} = 575 °C; (b) T{sub a} = 590 °C; (c) T{sub a} = 600 °C and (d) T{sub a} = 625 °C. - Highlights: • Fe{sub 50}Pd{sub 50} films have been grown by sputtering on Si substrate. • Transformation from the A1 disordered to the tetragonal L1{sub 0} phase induced by thermal treatments. • Microstructure connected with magnetic properties to optimize features for applications. - Abstract: Fe{sub 50}Pd{sub 50} thin films (t = 50 nm) have been deposited on Si substrates covered with a native oxide layer by sputtering technique. As-prepared films consist of a disordered Fe–Pd A1 phase, being deposited without heating the substrate. The order–disorder transformation towards the L1{sub 0}-ordered tetragonal phase has been induced by post deposition annealing in vacuum (annealing temperature ranging in the interval T{sub a} = 550–625 °C for 1200 s). Samples microstructure has been studied by means of X-ray diffraction, SEM and AFM microscopy. Room-temperature hysteresis loops have been measured by AGFM (Alternating Gradient Field Magnetometer) in parallel and perpendicular configuration. All produced systems have been observed to display tunable microstructure and, consequently, various magnetic properties. To study the magnetic properties evolution with annealing temperature, magnetic domain patterns have been measured by MFM. In particular, the domain-period dependence on the magnetocrystalline anisotropy constant has been analyzed.

  3. Thermochemical remanence in single-domain particle assemblages can lead to paleointensity overestimates

    Science.gov (United States)

    Fabian, K.

    2009-04-01

    Single-domain (SD) particle ensembles are the best studied systems in rock magnetism. Yet, even for this simple system, a complete theoretical treatment of the acquisition of thermochemical remanent magnetization (TCRM) is missing. Based on the SD theory of chemical-remanent magnetization (CRM), it is generally taken for granted that TCRM acquisition is less efficient than acquisition of a thermoremanent magnetization (TRM), and that consequently the paleofield intensity is inevitably underestimated when a TCRM is interpreted as a TRM. Here it is shown that this conclusion holds only when a continuous chemical change (e.g. grain growth) takes place during remanence blocking. In cases where an initial TRM, at a later time and at lower temperature, is modified by chemical processes, the final TCRM can result in considerable paleofield overestimation when interpreted as a TRM. This is demonstrated for two different scenarios. First, partial grain dissolution after TRM acquisition and second, low-temperature oxidation. These mechanisms are not unlikely to occur in nature, and numerical experiments indicate that both would lead to perfectly straight Arai plots, which make such SD TCRMs indistinguishable from true TRMs in the Thellier experiment.

  4. Rock magnetic properties of a soil developed on an alluvial deposit at Buttermilk Creek, Texas, USA

    National Research Council Canada - National Science Library

    Anna K. Lindquist; Joshua M. Feinberg; Michael R. Waters

    2011-01-01

      The evolution of magnetization within a floodplain soil begins with initial deposition of magnetic particles during sedimentation and continues via subsequent alteration and growth of iron-bearing...

  5. The Research and Development of the External Magnetic Field Acting on Electro-Deposition Process

    Directory of Open Access Journals (Sweden)

    Wu Menghua

    2016-01-01

    Full Text Available The research and development status of the electro-deposition technology under the action of external magnetic field are introduced. The basic characteristics and applied manners of external magnetic field in electro-deposition process are summarized. The acting principle of external magnetic field, the effects of magnetic hydrodynamics (MHD caused by the Lorentz force, and the acting of magnetic force on the metal ions and particles are described. The main actions of external magnetic field include MHD effect, magnetizing force, affecting the physical and chemical properties of the bath, affecting the disperse ability and coverage capacity of bath, affecting the mass transfer process of electro-deposition, affecting the chemical reaction process and current distribution of electrode surface. Some examples of electro-depositing single metal coatings, alloy coatings and composite coatings under action of magnetic field are explained. During the electro-depositing process, the external magnetic field has different degrees of impact on solution properties, mass transfer, charge transfer, content of composited nanoparticles, crystal growth and crystal orientation etc. The specific impact of magnetic field during the electro-depositing is also classified and summarized. The problems that existed in electro-deposition process while applying magnetic field and the next development trend were summarized.

  6. Quantitative Inspection of Remanence of Broken Wire Rope Based on Compressed Sensing

    Science.gov (United States)

    Zhang, Juwei; Tan, Xiaojiang

    2016-01-01

    Most traditional strong magnetic inspection equipment has disadvantages such as big excitation devices, high weight, low detection precision, and inconvenient operation. This paper presents the design of a giant magneto-resistance (GMR) sensor array collection system. The remanence signal is collected to acquire two-dimensional magnetic flux leakage (MFL) data on the surface of wire ropes. Through the use of compressed sensing wavelet filtering (CSWF), the image expression of wire ropes MFL on the surface was obtained. Then this was taken as the input of the designed back propagation (BP) neural network to extract three kinds of MFL image geometry features and seven invariant moments of defect images. Good results were obtained. The experimental results show that nondestructive inspection through the use of remanence has higher accuracy and reliability compared with traditional inspection devices, along with smaller volume, lighter weight and higher precision. PMID:27571077

  7. Quantitative Inspection of Remanence of Broken Wire Rope Based on Compressed Sensing

    Directory of Open Access Journals (Sweden)

    Juwei Zhang

    2016-08-01

    Full Text Available Most traditional strong magnetic inspection equipment has disadvantages such as big excitation devices, high weight, low detection precision, and inconvenient operation. This paper presents the design of a giant magneto-resistance (GMR sensor array collection system. The remanence signal is collected to acquire two-dimensional magnetic flux leakage (MFL data on the surface of wire ropes. Through the use of compressed sensing wavelet filtering (CSWF, the image expression of wire ropes MFL on the surface was obtained. Then this was taken as the input of the designed back propagation (BP neural network to extract three kinds of MFL image geometry features and seven invariant moments of defect images. Good results were obtained. The experimental results show that nondestructive inspection through the use of remanence has higher accuracy and reliability compared with traditional inspection devices, along with smaller volume, lighter weight and higher precision.

  8. A Criterion for the Complete Deposition of Magnetic Beads on the Walls of Microchannels.

    Science.gov (United States)

    Pallares, Jordi

    2016-01-01

    This paper analyzes numerical simulations of the trajectories of magnetic beads in a microchannel, with a nearby permanent cubical magnet, under different flow and magnetic conditions. Analytically derived local fluid velocities and local magnetic forces have been used to track the particles. A centered position and a lateral position of the magnet above the microchannel are considered. The computed fractions of deposited particles on the walls are compared successfully with a new theoretically derived criterion that imposes a relation between the sizes of the magnet and the microchannel and the particle Stokes and Alfvén numbers to obtain the complete deposition of the flowing particles on the wall. In the cases in which all the particles, initially distributed uniformly across the section of the microchannel, are deposited on the walls, the simulations predict the accumulation of the major part of particles on the wall closest to the magnet and near the first half of the streamwise length of the magnet.

  9. Untangling inconsistent magnetic polarity records through an integrated rock magnetic analysis: A case study on Neogene sections in East Timor

    NARCIS (Netherlands)

    Aben, F.M.; Dekkers, M.J.; Bakker, R.R.; van Hinsbergen, D.J.J.; Zachariasse, W.J.; Tate, G.W.; McQuarrie, N.; Harris, R.; Duffy, B.

    2014-01-01

    Inconsistent polarity patterns in sediments are a common problem in magnetostratigraphic and paleomagnetic research. Multiple magnetic mineral generations result in such remanence "haystacks." Here we test whether end-member modeling of isothermal remanent magnetization acquisition curves as a basis

  10. Approach to fabricating Co nanowire arrays with perpendicular anisotropy: Application of a magnetic field during deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ge, Shihui; Li, Chao; Ma, Xiao; Li, Wei; Xi, Li; Li, C. X.

    2001-07-01

    Cobalt (Co) nanowire arrays were electrodeposited into the pores of polycarbonate membranes. A magnetic field parallel or perpendicular to the membrane plane was applied during deposition to control the wire growth. X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer were employed to investigate the structure as well as the magnetic properties of the nanowire arrays. The results show that the magnetic field applied during deposition strongly influences the growth of Co nanowires, inducing variations in their crystalline structure and magnetic properties. The sample deposited with the field perpendicular to the membrane plane exhibits a perpendicular magnetic anisotropy with greatly enhanced coercivity and squareness as a result of the preferred growth of Co grains with the c axis perpendicular to the film plane. In contrast, the deposition in a parallel magnetic field forces Co grains to grow with the c axis parallel to the film plane, resulting in in-plane anisotropy. {copyright} 2001 American Institute of Physics.

  11. Practical considerations: making measurements of susceptibility, remanence and Q in the field

    Science.gov (United States)

    Schmidt, Phillip W.; Lackie, Mark A.

    2014-05-01

    Here we consider how measurements of magnetic susceptibility, magnetic remanence and Königsberger ratios (Q) can be made in the field. A basic refresher is given on how induced magnetisation differs from remanent magnetisation and what distinguishes multidomain from single domain behaviour of magnetite particles. The approximation of an infinite half-space, which is the usual assumption for using most handheld susceptibility meters, is experimentally investigated and it is found that a block 100 × 100 × 60 mm is the minimum requirement for the meters tested here. The susceptibilities of chips of a dacite, an andesite and a spilite (altered basalt) are also experimentally investigated for a range of chip sizes from a few mm down to 200 μm. The relationship is quite flat until very small grain sizes are reached where the susceptibility either decreases or increases, which is interpreted as an indication of the grain-size fraction where the magnetite resides. Making susceptibility measurements on bags of rock chips is investigated and guidelines given. The temperature of susceptibility meters is also found to be a factor and five meters have been tested for temperatures from 0°C to 50°C, the stated operating range of most meters. Finally Breiner's method to separate induced magnetisation from remanent magnetisation using a field magnetometer is discussed. A new fluxgate based pendulum instrument to allow a more controlled implementation of Breiner's method is also described.

  12. UHV plasma jet system for deposition of magnetic nitride nanocomposite films with GHz applications

    Energy Technology Data Exchange (ETDEWEB)

    Fendrych, F; Lancok, A [Institute of Physics, Academy of Sciences, Na Slovance 2, CZ-18221 Prague 8 (Czech Republic); Repa, P; Peksa, L; Gronych, T; Vejpravova, J P [Faculty of Math and Physics, Charles University in Prague, V Holesovickach 2, CZ-18000 Prague 8 (Czech Republic); Hedbavny, P [VAKUUM PRAHA, V Holesovickach 2, CZ-18000 Prague 8 (Czech Republic); Schaefer, R [Leibniz Institute IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Seemann, K M [Forschungszentrum Karlsruhe, Eggenstein, D-76021 Karlsruhe (Germany)], E-mail: fendrych@fzu.cz

    2008-03-15

    A method of preparation of extremely pure magnetic thin films, especially magnetic nitride nanocomposites for GHz aplications was searched. The plasma-jet method was chosen for its advantages at magnetic materials deposition. Sources of impurities deteriorating the quality of the films were analysed. Based on the assumption that the achievable purity is limited mainly by the conditions at the deposition, an experimental UHV apparatus with the plasma-jet was designed. A number of magnetic thin films from various materials including nitride nanocomposite films was prepared already in this apparatus at UHV conditions. Their magnetic properties are far better than those of the films prepared in a high vacuum apparatus.

  13. Effect of Respective Additions of Ga, Zr and Combined Additions of Co, Ga, Zr on Magnetic Properties of Remanence-enhanced Nd8.4Fe87.1B4.5 Alloy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The effect ora partial substitution of Zr; Ga; Co and Ga; Co, Ga and Zr; respectively, for Fe on the structure and magnetic properties of Nd8.4Fe87.1B4.5 alloy prepared by mechanical alloying has been studied in detail. It has been shown that, intrinsic coercivityμ0Hc and maximum magnetic energy product (BH)max increase for only Zr or Ga-containing samples, which is mainly due to the refinement of soft grains. The combined addition of Co and Ga is less effective for improving μ0Hc and (BH)max than the respective addition of Co or Ga, which may be due to the formation of CsCl-type CoGa. μ0Hc and (BH)max for combined Co, Ga, Zr-added alloy are higher than those for the combined Co, Ga-added alloy but lower than those for only Zr-containing alloy.

  14. Particles deposition induced by the magnetic field in the coronary bypass graft model

    Energy Technology Data Exchange (ETDEWEB)

    Bernad, Sandor I., E-mail: sandor.bernad@upt.ro [Centre of Advanced Research in Engineering Sciences, Romanian Academy, Timisoara Branch, 300223 Timisoara (Romania); Totorean, Alin F. [Department of Mechanical Machines, Equipment and Transportation, Politehnica University of Timisoara, RO-300222 Timisoara (Romania); Vekas, Ladislau, E-mail: vekas.ladislau@gmail.com [Centre of Advanced Research in Engineering Sciences, Romanian Academy, Timisoara Branch, 300223 Timisoara (Romania)

    2016-03-01

    Bypass graft failures is a complex process starting with intimal hyperplasia development which involve many hemodynamic and biological factors. This work presents experimental results regarding the possibility to use magnetic drug delivery to prevent the development of the intimal hyperplasia using a simplified but intuitive model. The primary goal is to understand the magnetic particle deposition in the anastomosis region of the bypass graft taking into account the complex flow field created in this area which involves recirculation region, flow mixing and presence of particles with high residence time. The three-dimensional geometry model was used to simulate the motion and accumulation of the particles under the magnetic field influence in anastomotic region of the coronary bypass graft. The flow patterns are evaluated both numerically and experimentally and show a good correlation in term of flow parameters like vortex length and flow stagnation point positions. Particle depositions are strongly dependent on the magnet position and consequently of the magnetic field intensity and field gradient. Increased magnetic field controlled by the magnet position induces increased particle depositions in the bypass graft anastomosis. The result shows that particle depositions depend on the bypass graft angle, and the deposition shape and particle accumulation respectively, depend by the flow pattern in the anastomosis region. - Highlights: • Particularity of the particle targeting in the bypass graft anastomosis. • Hemodynamic characteristics influence about the particle deposition. • Particle accumulation induces changes of the flow field in the graft anastomosis. • Bypass graft geometries influence the particle deposition.

  15. Deposition pressure and rate effects on the microstructure and magnetic properties of sputtered tape media

    Energy Technology Data Exchange (ETDEWEB)

    Han Jixiong, E-mail: jhan@imation.co [Imation Corp., 1 Imation Place, 304-1A, Oakdale, MN 55128 (United States); Hintz, Mike [Medtronic Energy and Component Center, 6800 Shingle Creek Parkway, Brooklyn Center, MN 55430 (United States); Sexton, Joseph; Skorjanec, Joseph; Lundstrom, Garry [Imation Corp., 1 Imation Place, 304-1A, Oakdale, MN 55128 (United States)

    2010-02-01

    Sputtered magnetic tape media were prepared by DC magnetron sputtering on polyimide substrates at different deposition conditions. The structure, texture and magnetic properties of the sputtered films were systematically studied using transmission electron microscopy, X-ray diffraction and alternating gradient magnetometer. The microstructure of sputtered media is greatly influenced by the deposition conditions, such as deposition pressure and rate. High sputtering pressure and slow deposition rate produced high coercivity and low delta M films. The sputtered tape media have the desired grain segregation structure which is essential for low-noise media fabrication. X-ray diffraction analysis revealed that the stress of film is closely related to the deposition pressure. The stress of the film stack can be tuned for specific applications and good magnetic properties can be obtained under optimized deposition condition.

  16. Magnetic properties related to hydrothermal alteration processes at the Escondida porphyry copper deposit, northern Chile

    Science.gov (United States)

    Riveros, K.; Veloso, E.; Campos, E.; Menzies, A.; Véliz, W.

    2014-08-01

    Fluid-rock interaction related to the circulation of hydrothermal fluids can strongly modify the physicochemical properties of wall rocks in porphyry Cu deposits. These processes can also produce compositional and textural changes in ferromagnetic minerals, which can be quantified using magnetic methods. In the Escondida porphyry Cu deposit of northern Chile, each hydrothermally altered lithology is characterized by a discrete assemblage of Fe-Ti oxide minerals. These minerals have distinctive bulk magnetic susceptibility ( K bulk), temperature-dependent magnetic susceptibility, and magnetic hysteresis parameters. Selectively altered rocks (i.e., potassic and chloritic alteration types) exhibit the highest K bulk values (>3.93 × 10-3 SI units), and their hysteresis parameters indicate multidomain magnetic mineral behavior. This suggests that these rocks are composed of the coarsest magnetic grain sizes within the deposit. Optical analyses and susceptibility-temperature curves confirm that the magnetic signals in selectively altered rocks are mainly carried by secondary magnetite. In contrast, pervasively altered rocks (i.e., quartz-sericite and argillic alteration types) exhibit low K bulk values (hydrothermal alteration processes, Fe-Ti oxide minerals, and magnetic properties of the wall rock in the Escondida deposit. These magnetic methods can be considered a sensitive and efficient petrophysical tool for the identification and semi-quantification of alteration assemblages, and facilitating the recognition and mapping of discrete hydrothermal zones during exploration and operation of porphyry Cu deposits.

  17. Magnetic properties of Ni-Fe nanowire arrays: effect of template material and deposition conditions

    Energy Technology Data Exchange (ETDEWEB)

    Singleton, John [Los Alamos National Laboratory; Aravamudhan, Shyan [U OF SOUTH FL; Goddard, Paul A [U OF OXFORD; Bhansali, Shekhar [U OF SOUTH FL

    2008-01-01

    The objective of this work is to study the magnetic properties of arrays of Ni-Fe nanowires electrodeposited in different template materials such as porous silicon, polycarbonate and alumina. Magnetic properties were studied as a function of template material, applied magnetic field (parallel and perpendicular) during deposition, wire length, as well as magnetic field orientation during measurement. The results show that application of magnetic field during deposition strongly influences the c-axis preferred orientation growth of Ni-Fe nanowires. The samples with magnetic field perpendicular to template plane during deposition exhibits strong perpendicular anisotropy with greatly enhanced coercivity and squareness ratio, particularly in Ni-Fe nanowires deposited in polycarbonate templates. In case of polycarbonate template, as magnetic field during deposition increases, both coercivity and squareness ratio also increase. The wire length dependence was also measured for polycarbonate templates. As wire length increases, coercivity and squarness ratio decrease, but saturation field increases. Such magnetic behavior (dependence on template material, magnetic field, wire length) can be qualitatively explained by preferential growth phenomena, dipolar interactions among nanowires, and perpendicular shape anisotropy in individual nanowires.

  18. Laboratory Deposition Apparatus to Study the Effects of Wax Deposition on Pipe Magnetic Field Leakage Signals

    Directory of Open Access Journals (Sweden)

    Karim Mohd Fauzi Abd

    2014-07-01

    Full Text Available Accurate technique for wax deposition detection and severity measurement on cold pipe wall is important for pipeline cleaning program. Usually these techniques are validated by conventional techniques on laboratory scale wax deposition flow loop. However conventional techniques inherent limitations and it is difficult to reproduce a predetermine wax deposit profile and hardness at designated location in flow loop. An alternative wax deposition system which integrates modified pour casting method and cold finger method is presented. This system is suitable to reproduce high volume of medium hard wax deposit in pipe with better control of wax deposit profile and hardness.

  19. Remanence Preservation In Burnt Silos During Pre-christian Age Fire In A Galician Castro (nw Spain)

    Science.gov (United States)

    Mohamed, K.; Rey, D.; Méndez, G.; Evans, M. E.

    Archaeomagnetic studies are usually based on measurements made on pottery or buildings that have achieved high temperatures because the results obtained are com- monly of better quality. In this study three burnt grain silos from the recently disap- peared Castro de As Laias located in Ourense (NW Spain) have provided a successful date of a pre-Christian fire. AF and thermal demagnetization were carried out to iso- late the characteristic component of magnetization. Hysteresis and IRM acquisition experiments were carried out to characterise the magnetic minerals responsible of the remanence Additionally, XRD analyses and observations under the SEM were also performed to support the magnetic data. The characteristic remanent magnetization (ChRM) has shown that two of the three studied silos burnt at the same time. Radio- carbon dating on charcoal gives an age of 181+/-61. These results also contribute to a better definition of a Secular Variation Curve (SVC) for the early Christian Age in Iberia.

  20. Remanent spin injection and spin relaxation in quantum dot light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Soldat, Henning; Li, Mingyuan; Gerhardt, Nils C.; Hofmann, Martin R. [Lehrstuhl fuer Photonik und Terahertztechnologie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Ludwig, Arne; Wieck, Andreas D.; Reuter, Dirk [Lehrstuhl fuer Angewandte Festkoerperphysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Stromberg, Frank; Keune, Werner; Wende, Heiko [Fakultaet fuer Physik, Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, D-47048 Duisburg (Germany)

    2011-07-01

    The study of spin-controlled optoelectronic devices has been a field of intensive research over the past few years. We investigate spin injection in remanence into InAs quantum dot (QD) light emitting diodes (LEDs). Our samples are spin LEDs with a Fe/Tb injector with out-of-plane remanent magnetization and a MgO tunnel barrier at the ferromagnetic metal/semiconductor interface to overcome the conductivity mismatch. The active region is an ensemble of InAs QDs. Intrinsic GaAs layers of variable thickness have been implemented between this active region and the spin injector to investigate the influence of transport path length on spin polarization. We have measured the circular polarization of the LED emission in remanence. By investigating the different injection path lengths for the samples we have determined the spin diffusion length in undoped GaAs along with the spin polarization at the injector interface. Additionally, the spin injection efficiency at the MgO tunnel barrier has been investigated.

  1. Magnetic domain observation of FeCo thin films fabricated by alternate monoatomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ohtsuki, T., E-mail: ohtsuki@spring8.or.jp; Kotsugi, M.; Ohkochi, T. [Japan Synchrotron Radiation Research Institute (JASRI), 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Kojima, T.; Mizuguchi, M.; Takanashi, K. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2014-01-28

    FeCo thin films are fabricated by alternate monoatomic layer deposition method on a Cu{sub 3}Au buffer layer, which in-plane lattice constant is very close to the predicted value to obtain a large magnetic anisotropy constant. The variation of the in-plane lattice constant during the deposition process is investigated by reflection high-energy electron diffraction. The magnetic domain images are also observed by a photoelectron emission microscope in order to microscopically understand the magnetic structure. As a result, element-specific magnetic domain images show that Fe and Co magnetic moments align parallel. A series of images obtained with various azimuth reveal that the FeCo thin films show fourfold in-plane magnetic anisotropy along 〈110〉 direction, and that the magnetic domain structure is composed only of 90∘ wall.

  2. Particles deposition induced by the magnetic field in the coronary bypass graft model

    Science.gov (United States)

    Bernad, Sandor I.; Totorean, Alin F.; Vekas, Ladislau

    2016-03-01

    Bypass graft failures is a complex process starting with intimal hyperplasia development which involve many hemodynamic and biological factors. This work presents experimental results regarding the possibility to use magnetic drug delivery to prevent the development of the intimal hyperplasia using a simplified but intuitive model. The primary goal is to understand the magnetic particle deposition in the anastomosis region of the bypass graft taking into account the complex flow field created in this area which involves recirculation region, flow mixing and presence of particles with high residence time. The three-dimensional geometry model was used to simulate the motion and accumulation of the particles under the magnetic field influence in anastomotic region of the coronary bypass graft. The flow patterns are evaluated both numerically and experimentally and show a good correlation in term of flow parameters like vortex length and flow stagnation point positions. Particle depositions are strongly dependent on the magnet position and consequently of the magnetic field intensity and field gradient. Increased magnetic field controlled by the magnet position induces increased particle depositions in the bypass graft anastomosis. The result shows that particle depositions depend on the bypass graft angle, and the deposition shape and particle accumulation respectively, depend by the flow pattern in the anastomosis region.

  3. Structural and Magnetic Properties of Mn doped ZnO Thin Film Deposited by Pulsed Laser Deposition

    KAUST Repository

    Baras, Abdulaziz

    2011-07-01

    Diluted magnetic oxide (DMO) research is a growing field of interdisciplinary study like spintronic devices and medical imaging. A definite agreement among researchers concerning the origin of ferromagnetism in DMO has yet to be reached. This thesis presents a study on the structural and magnetic properties of DMO thin films. It attempts to contribute to the understanding of ferromagnetism (FM) origin in DMO. Pure ZnO and Mn doped ZnO thin films have been deposited by pulsed laser deposition (PLD) using different deposition conditions. This was conducted in order to correlate the change between structural and magnetic properties. Structural properties of the films were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The superconducting quantum interference device (SQUID) was used to investigate the magnetic properties of these films. The structural characterizations showed that the quality of pure ZnO and Mn doped ZnO films increased as oxygen pressure (PO) increased during deposition. All samples were insulators. In Mn doped films, Mn concentration decreased as PO increased. The Mn doped ZnO samples were deposited at 600˚C and oxygen pressure from 50-500mTorr. All Mn doped films displayed room temperature ferromagnetism (RTFM). However, at 5 K a superparamagnetic (SPM) behavior was observed in these samples. This result was accounted for by the supposition that there were secondary phase(s) causing the superparamagnetic behavior. Our findings hope to strengthen existing research on DMO origins and suggest that secondary phases are the core components that suppress the ferromagnetism. Although RTFM and SPM at low temperature has been observed in other systems (e.g., Co doped ZnO), we are the first to report this behavior in Mn doped ZnO. Future research might extend the characterization and exploration of ferromagnetism in this system.

  4. Effects of a high magnetic field on structure evolution and properties of the molecular beam vapor deposited Fe{sub 60}Ni{sub 40} nanoparticles thin films

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Yongze [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Wang, Qiang, E-mail: wangq@mail.neu.edu.cn [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Li, Guojian; Du, Jiaojiao [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Wang, Xiaoguang [Huaxun Vacuum Technology Limited Company, Shenyang 110168 (China); He, Jicheng [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China)

    2014-12-15

    The Fe{sub 60}Ni{sub 40} (in atomic %) nanoparticles (NPs) thin films with 90 nm thickness were prepared on 25 and 400 °C quartz substrates by using the molecular beam vapor deposition (MBVD) method under a 6 T high magnetic field (HMF). The effects of a HMF on the structure evolution and properties of Fe–Ni thin films were studied by using X-ray diffraction, atomic force microscopy, transmission electron microscopy, vibrating sample magnetometer and four-point probe method. The results show that the crystallinity of thin films is enhanced by a 6 T HMF, and a 6 T HMF changes phase composition of thin films on 25 °C substrate. It is found that the nanoparticle size decreases; the nanoparticle size distribution becomes narrow, and the root mean square (rms) roughness of thin films decreases under a 6 T HMF relative to that without HMF. These lead to the decrease of coercive force, and the increase of in-plane remanence ratio under a 6 T HMF.

  5. Saw-toothed pattern of relative paleointensity records and cumulative viscous remanence

    Science.gov (United States)

    Kok, Yvo S.; Tauxe, Lisa

    1996-01-01

    Several studies of relative paleointensity data derived from marine sediments spanning the last 4 Myr display an asymmetrical "saw-toothed" pattern. Polarity reversals of the geomagnetic field are associated with low points in paleofield intensity, preceded by a long-term progressive decay of the field and followed by a rapid post-transitional recovery [1-3]. Since similar behavior is observed in far-flung sites whose rock magnetic records are different, it is argued that the world-wide "saw-toothing" represents geomagnetic field behavior[3]. We present an alternative explanation, calling on the effect of "hard" viscous remanence.

  6. Cu Films Deposited by Unbalanced Magnetron Sputtering Enhanced by ICP and External Magnetic Field Confinement

    Institute of Scientific and Technical Information of China (English)

    QI Xuelian; REN Chunsheng; MA Tengcai; WANG Younian

    2008-01-01

    Metallic copper(Cu) films were deposited on a Si (100) substrate by unbalanced magnetron sputtering enhanced by radio-frequency plasma and external magnetic field confine-ment. The morphology and structure of the films were examined by scanning electron microscopy (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD). The surface average rough-ness of the deposited Cu films was characterized by AFM data and resistivity was measured by a four-point probe. The results show that the Cu films deposited with radio-frequency discharge enhanced ionization and external magnetic field confinement have a smooth surface, low surface roughness and low resistivity. The reasons may be that the radio-frequency discharge and external magnetic field enhance the plasma density, which further improves the ion bombardment effect under the same bias voltage conditions. Ion bombardment can obviously influence the growth features and characteristics of the deposited Cu films.

  7. Study of magnetism in Ni-Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

    Science.gov (United States)

    Kishore, G. V. K.; Kumar, Anish; Chakraborty, Gopa; Albert, S. K.; Rao, B. Purna Chandra; Bhaduri, A. K.; Jayakumar, T.

    2015-07-01

    Nickel base Ni-Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni-Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr-C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co-Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni-Cr alloy deposits on stainless steel.

  8. Study of Magnetism in Colmonoy-6 (AWS NiCr-C) Deposit on 316LN Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Gopa, E-mail: gopa_mjs@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India); Ramasubbu, V., E-mail: vrsubbu@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India); Albert, S.K., E-mail: shaju@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India); Bhaduri, A.K., E-mail: bhaduri@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India); Murugesan, S., E-mail: smurug@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India); Raj, Baldev, E-mail: dir@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India)

    2010-06-15

    Considerable difference in melting points between the austenitic stainless steel (SS) substrate and Ni-base Colmonoy (AWS NiCr) hardfacing alloys results in significant dilution of the hardface deposit from the substrate. In the present study, it is found that the dilution also affects the magnetic property of the deposit. Although both austenitic SS and the undiluted Ni-base hardfacing alloy deposit are non-magnetic, the deposit diluted by austenitic SS becomes magnetic. Magnetism at different dilution levels of the deposit is measured using Magnegage and Feritscope, and the results correlated with the dilution of the deposit that is estimated from its Fe and Ni contents using SEM-EDS analysis. A good correlation between dilution and magnetic property could be obtained. As dilution also affects the hardness of the deposit, it was also possible to correlate the magnetic property of the deposit with its hardness. These findings have potential application in using magnetic measurement as a non-destructive method for estimating the hardness and/or dilution of the deposit on actual components not amenable for in-situ hardness measurements. The possible origin of magnetism in the deposit layers has been examined. The small variations in the lattice parameters of the deposit with dilution (composition) could be well correlated with variation in magnetic property.

  9. Investigation of the magnetization reversal mechanism of electrolessly deposited Co-B nanotubes

    Science.gov (United States)

    Richardson, David; Kingston, Samuel; Rhen, Fernando M. F.

    2016-05-01

    Co-B nanotubes were prepared via an electroless deposition method. The morphology, magnetic properties and the magnetization reversal mechanism of the nanotubes were investigated. Deposition was carried out in porous polycarbonate membranes leading to the formation of Co-B nanotubes with an average external diameter of 400 nm and lengths up to 6 μm. Electroless deposition resulted in the formation of alloys with composition Co70B30 and a specific magnetization of 65.6 J T-1kg-1, which is about 40 % of that of pure Co (161 J T-1kg-1). The transversal and vortex modes were identified as the mechanisms responsible for magnetization reversal in the nanotubes. A crossover between the two modes is observed at low angles and the results are in line with current models for switching mechanisms of nanotubes.

  10. Investigation of the magnetization reversal mechanism of electrolessly deposited Co-B nanotubes

    Directory of Open Access Journals (Sweden)

    David Richardson

    2016-05-01

    Full Text Available Co-B nanotubes were prepared via an electroless deposition method. The morphology, magnetic properties and the magnetization reversal mechanism of the nanotubes were investigated. Deposition was carried out in porous polycarbonate membranes leading to the formation of Co-B nanotubes with an average external diameter of 400 nm and lengths up to 6 μm. Electroless deposition resulted in the formation of alloys with composition Co70B30 and a specific magnetization of 65.6 J T−1kg−1, which is about 40 % of that of pure Co (161 J T−1kg−1. The transversal and vortex modes were identified as the mechanisms responsible for magnetization reversal in the nanotubes. A crossover between the two modes is observed at low angles and the results are in line with current models for switching mechanisms of nanotubes.

  11. Quench Limit Model and Measurements for Steady State Heat Deposits in LHC Magnets

    CERN Document Server

    Bocian, D; Siemko, A

    2009-01-01

    A quench, transition of a conductor from the superconducting to the normal conducting state, occurs irreversibly in accelerator magnets if one of the three parameters: temperature, magnetic field or current density, exceeds its critical value. The protons lost from the beam and impacting on the vacuum chamber, create a secondary particle shower that deposes its energy in the magnet coil. Energy deposited in the superconductor by these particles can provoke quenches that can be detrimental for the accelerator operation. A network model is developed to study the thermodynamic behavior of the LHC magnets. The results of the heat flow simulation in the main dipole and quadrupole LHC magnets calculated by means of the network model were validated with measurements performed at superfluid helium temperatures in the CERN magnet test facility. A steady state heat flow was introduced in the magnet coil by using a dedicated internal heating apparatus (IHA) installed inside the magnet cold bore. The value of the heat so...

  12. Generating the optimal magnetic field for magnetic refrigeration

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Insinga, Andrea Roberto; Smith, Anders

    2016-01-01

    remanence distribution for any desired magnetic field. The method is based on the reciprocity theorem, which through the use of virtual magnets can be used to calculate the optimal remanence distribution. Furthermore, we present a method for segmenting a given magnet design that always results...

  13. Linking speleothem and soil magnetism in the Pau d'Alho cave (central South America)

    Science.gov (United States)

    Jaqueto, Plinio; Trindade, Ricardo I. F.; Hartmann, Gelvam A.; Novello, Valdir F.; Cruz, Francisco W.; Karmann, Ivo; Strauss, Becky E.; Feinberg, Joshua M.

    2016-10-01

    Mineral magnetism of Pau d'Alho cave sediments, soils outside the cave, and in the stalagmite #6 (ALHO6) in Midwest Brazil is presented. This high growth-rate speleothem ( 168 mm/ka) encompasses the past 1355 years. Oxygen and carbon isotope data from the same stalagmite allow for a direct comparison of the magnetic signal with changes in paleoprecipitation and soil dynamics at the surface. Magnetic experiments include isothermal remanent magnetization, anhysteretic remanent magnetization, hysteresis loops, first-order reversal curves, and low-temperature superconducting quantum interference device magnetometry. The main magnetic remanence carriers in ALHO6 are magnetite and goethite, with a nearly constant relative proportion. Remanent coercivities of magnetite in all our samples are within 14-17 mT for an average grain-size of 1-2 µm, in the range of pedogenic magnetite, thus suggesting the detrital grains deposited in the stalagmite were produced in the soil above the cave. Magnetic remanence variations follow δ13C and δ18O data, suggesting a climatic control on the input of magnetic minerals into the Pau d'Alho cave system. The concentration of magnetic minerals in the stalagmite is governed by soil erosion above the cave, which by its turn is controlled by soil erosion and vegetation cover. Dry periods are associated with less stable soils and result in higher mineral fluxes carried into karst systems. Conversely, wetter periods are associated with soils topped by denser vegetation that retains micrometer-scale pedogenic minerals and thus reduces detrital fluxes into the cave.

  14. Magnetic properties of ilmenite-hematite single crystals from the Ecstall pluton near Prince Rupert, British Columbia

    DEFF Research Database (Denmark)

    Brownlee, Sarah J.; Feinberg, Joshua M.; Kasama, Takeshi

    2011-01-01

    and hematite, the primary paleomagnetic recorder in the Ecstall pluton. Measurements of hysteresis properties, low-temperature remanence, and room temperature isothermal remanent magnetization acquisition and observations from magnetic force microscopy and off-axis electron holography indicate that samples...

  15. Magnetically extracted microstructural development along the length of Co nanowire arrays: The interplay between deposition frequency and magnetic coercivity

    Science.gov (United States)

    Montazer, A. H.; Ramazani, A.; Almasi Kashi, M.

    2016-09-01

    Providing practical implications for developing the design and optimizing the performance of hard magnets based on nanowires (NWs) requires an in-depth understanding of the processes in fabrication and magnetic parameters. Here, an electrochemical deposition technique with different frequencies is used to fabricate 50 nm diameter Co NW arrays into the nanopores of anodic aluminum oxide templates. The resulting NWs with dendrites at the base are subsequently exposed to a chemical etching with which to prepare cylindrical Co NWs with an aspect ratio of 200. In this way, the coercivity at room temperature increases up to 20% for different deposition frequencies, indicating the occurrence of a magnetic hardening along the NW length. Decreasing the length of the cylindrical NWs in ascending order whilst also using a successive magnetometry, the deposition frequency is found to be an important parameter in further enhancing the initial coercivity up to 65% in the length range of 10 to 3 μm. The first-order reversal curve diagrams evaluated along the NW length evidence the elimination of a soft magnetic phase and the formation of harder magnetic domains when reducing the length. Alternatively, X-ray diffraction patterns show improvements in the crystallinity along the [002] direction, pertaining to the alignment of the hexagonal close-packed c-axis of cobalt and long axis of NWs when reducing the length. These results may address the growing need for the creative design and low cost fabrication of rare-earth-free permanent magnets with high coercivity and availability.

  16. A Criterion for the Complete Deposition of Magnetic Beads on the Walls of Microchannels.

    Directory of Open Access Journals (Sweden)

    Jordi Pallares

    Full Text Available This paper analyzes numerical simulations of the trajectories of magnetic beads in a microchannel, with a nearby permanent cubical magnet, under different flow and magnetic conditions. Analytically derived local fluid velocities and local magnetic forces have been used to track the particles. A centered position and a lateral position of the magnet above the microchannel are considered. The computed fractions of deposited particles on the walls are compared successfully with a new theoretically derived criterion that imposes a relation between the sizes of the magnet and the microchannel and the particle Stokes and Alfvén numbers to obtain the complete deposition of the flowing particles on the wall. In the cases in which all the particles, initially distributed uniformly across the section of the microchannel, are deposited on the walls, the simulations predict the accumulation of the major part of particles on the wall closest to the magnet and near the first half of the streamwise length of the magnet.

  17. Substrate dependent structural and magnetic properties of pulsed laser deposited Fe3O4 thin films.

    Science.gov (United States)

    Goyal, Rajendra N; Kaur, Davinder; Pandey, Ashish K

    2010-12-01

    Nanocrystalline iron oxide thin films have been deposited on various substrates such as quartz, MgO(100), and Si(100) by pulsed laser deposition technique using excimer KrF laser (248 nm). The orientations, crystallite size and lattice parameters were studied using X-ray diffraction. The XRD results show that the films deposited on MgO and Si substrates are highly oriented and show only (400) and (311) reflections respectively. On the other hand, the orientation of the films deposited on quarts substrate changed from (311) to (400) with an increase in the substrate temperature from 400 degrees C to 600 degrees C, indicating thereby that the film growth direction is highly affected with nature of substrate and substrate temperature. The surface morphology of the deposited films was studied using Atomic Force Microscopy (AFM) and spherical ball like regular features of nanometer size grains were obtained. The magnetic properties were studied by Superconducting Quantum Interference Device (SQUID) magnetometer in the magnetic field +/- 6 Tesla. The magnetic field dependent magnetization (M-H) curves of all the Fe3O4 thin films measured at 5 K and 300 K show the ferrimagnetic nature. The electrochemical sensing of dopamine studied for these films shows that the film deposited on MgO substrate can be used as a sensing electrode.

  18. The Physical and Magnetic Properties of Electrodeposited Co-Fe Nanocoating with Different Deposition Times

    Directory of Open Access Journals (Sweden)

    Koay Mei Hyie

    2013-01-01

    Full Text Available Using the electrodeposition process, cobalt-iron (Co-Fe nanocrystalline coatings were successfully synthesized onto stainless steel in deposition times of 30, 60, and 90 minutes. The temperature used throughout the process was 50°C in an acidic environment of pH 3. By changing the deposition time, physical properties such as phase and crystallographic structure, surface morphology, grain size, microhardness, and magnetic properties of Co-Fe coatings were examined. FESEM micrographs showed that the grain sizes of the coatings were in the range from 57.9 nm to 70.2 nm. Dendrite and irregular shapes were found in the microstructure of Co-Fe nanocoating. The Co-Fe nanocrystalline coating prepared in a deposition time of 90 minutes achieved the highest microhardness of 339 HVN. The magnetic properties associated with Co-Fe nanocoating at longer deposition times show greater coercivity, Hc, and saturation magnetization, Ms, values of 56.43 Oe and 70.45 eμ/g, respectively. The M-H curves for all the Co-Fe coatings exhibited soft ferromagnetic behaviour with narrow hysteresis loops. It was found that increasing the deposition time also improved the microhardness and magnetic properties of Co-Fe nanocoating, which is much needed for long-life high-coercivity magnetic strip card applications.

  19. Structural and magnetic properties of magnetoelectric oxide heterostructures deposited by molecular beam epitaxy

    Science.gov (United States)

    Sterbinsky, George Evan

    There is considerable interest in incorporating magnetic materials into electronic devices to achieve new functions such as nonvolatile memories. Electric field control of magnetism is of much interest for new low power electronic devices because it eliminates the need to apply magnetic fields. One approach to achieving electrical control of magnetism is to exploit magnetoelastic effects in composites of ferromagnetic and ferroelectric materials. Application of an electric field to the composite will induce a strain through the piezo-electric effect, and the strain will alter the magnetization of the ferromagnetic constituent through the magnetoelastic effect. In this work, we examine the relationships between growth, strain, and magnetic properties of epitaxial ferrimagnetic Fe3O4 (magnetite) and ferroelectric BaTiO3 thin film heterostructures. We find that altering the strain state of a magnetite layer deposited on a BaTiO3 substrate has a profound effect on its magnetization. Here, we demonstrate the interaction between strain and magnetization is mediated by magnetic anisotropy and the magnetic domains structure of the films. Epitaxial magnetite films were deposited on MgO, BaTiO3, and SrTiO3 substrates by molecular beam epitaxy between temperatures of 573 and 723 K. Examination of the morphologies of Fe3O 4 films indicates that island growth is favored. Films exhibit in-plane magnetic isotropy and reduced saturation magnetizations with respect to the bulk material, as demonstrated by superconducting quantum interference device magnetometry. Magnetic hysteresis measurements suggest that these differences originate from antiphase boundary defects within the films. The strain in magnetite films deposited on BaTiO3 single crystal substrates was measured by x-ray diffraction. Measurements reveal a dependence of magnetization (M) on strain (epsilon) with discontinuities in magnetization versus temperature curves resulting from changes in the domain structure of the

  20. Atomic Layer Deposition Al2O3 Thin Films in Magnetized Radio Frequency Plasma Source

    Science.gov (United States)

    Li, Xingcun; Chen, Qiang; Sang, Lijun; Yang, Lizhen; Liu, Zhongwei; Wang, Zhenduo

    Self-limiting deposition of aluminum oxide (Al2O3) thin films were accomplished by the plasma-enhanced chemical vapor deposition using trimethyl aluminum (TMA) and O2 as precursor and oxidant, respectively, where argon was kept flowing in whole deposition process as discharge and purge gas. In here we present a novel plasma source for the atomic layer deposition technology, magnetized radio frequency (RF) plasma. Difference from the commercial RF source, magnetic coils were amounted above the RF electrode, and the influence of the magnetic field strength on the deposition rate and morphology are investigated in detail. It concludes that a more than 3 Å/ purging cycle deposition rate and the good quality of ALD Al2O3 were achieved in this plasma source even without extra heating. The ultra-thin films were characterized by including Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectric spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The high deposition rates obtained at ambient temperatures were analyzed after in-situ the diagnostic of plasmas by Langmuir probe.

  1. Structural and magnetic properties of Gd/Fe multilayers grown by pulsed laser deposition

    DEFF Research Database (Denmark)

    Kant, K. Mohan; Bahl, Christian Robert Haffenden; Pryds, Nini;

    This work investigates structural and magnetic properties of Gd/Fe multilayered thin films grown by pulsed laser deposition onto Si (001) substrates at room temperature. The Fe layer thickness is varied from 70 to 150 nm and its effect on structural and magnetic properties of Gd/Fe multilayers has...... been explored. The samples have a 10 nm Ag capping layer to prevent oxidation during the processing. Two magnetization saturation plateaus were observed in the magnetization vs field isotherm at 290 K, in parallel configuration and these plateau values correspond to that of MFe and MFe + MGd....

  2. Non-collinear magnetism induced by frustration in transition-metal nanostructures deposited on surfaces.

    Science.gov (United States)

    Lounis, S

    2014-07-01

    How does magnetism behave when the physical dimension is reduced to the size of nanostructures? The multiplicity of magnetic states in these systems can be very rich, in that their properties depend on the atomic species, the cluster size, shape and symmetry or choice of the substrate. Small variations of the cluster parameters may change the properties dramatically. Research in this field has gained much by the many novel experimental methods and techniques exhibiting atomic resolution. Here we review the ab-initio approach, focusing on recent calculations on magnetic frustration and occurrence of non-collinear magnetism in antiferromagnetic nanostructures deposited on surfaces.

  3. Fe:O:C grown by focused-electron-beam-induced deposition: magnetic and electric properties

    Energy Technology Data Exchange (ETDEWEB)

    Lavrijsen, R; Schoenaker, F J; Ellis, T H; Barcones, B; Kohlhepp, J T; Swagten, H J M; Koopmans, B [Department of Applied Physics, Center for NanoMaterials and COBRA Research Institute, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Cordoba, R; Ibarra, M R [Instituto de Nanociencia de Aragon, Universidad de Zaragoza, E-50009 Zaragoza (Spain); De Teresa, J M; Magen, C [Departamento de Fisica de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza (Spain); Trompenaars, P; Mulders, J J L, E-mail: r.lavrijsen@tue.nl, E-mail: deteresa@unizar.es [FEI Electron Optics, Achtseweg Noord 5, 5651 GG Eindhoven (Netherlands)

    2011-01-14

    We systematically study the effect of oxygen content on the magneto-transport and microstructure of Fe:O:C nanowires deposited by focused-electron-beam-induced (FEBID) deposition. The Fe/O ratio can be varied with an Fe content varying between {approx} 50 and 80 at.% with overall low C content ({approx}16 {+-} 3 at.%) by adding H{sub 2}O during the deposition while keeping the beam parameters constant as measured by energy dispersive x-ray (EDX) spectroscopy. The room-temperature magnetic properties for deposits with an Fe content of 66-71 at.% are investigated using the magneto-optical Kerr effect (MOKE) and electric magneto-transport measurements. The nanostructure of the deposits is investigated through cross-sectional high-resolution transmission electron microscopy (HRTEM) imaging, allowing us to link the observed magneto-resistance and resistivity to the transport mechanism in the deposits. These results demonstrate that functional magnetic nanostructures can be created, paving the way for new magnetic or even spintronics devices.

  4. Manipulating magnetic anisotropies of Co/MgO(001) ultrathin films via oblique deposition

    Science.gov (United States)

    Sheraz Ahmad, Syed; He, Wei; Tang, Jin; Zhang, Yong Sheng; Hu, Bo; Ye, Jun; Gul, Qeemat; Zhang, Xiang-Qun; Cheng, Zhao-Hua

    2016-09-01

    We present a systematic investigation of magnetic anisotropy induced by oblique deposition of Co thin films on MgO (001) substrates by molecular beam epitaxy at different deposition angles, i.e., 0°, 30°, 45°, 60°, and 75° with respect to the surface normal. Low energy electron diffraction (LEED), surface magneto-optical Kerr effect (SMOKE), and anisotropic magnetoresistance (AMR) setups were employed to investigate the magnetic properties of cobalt films. The values of in-plane uniaxial magnetic anisotropy (UMA) constant Ku and four-fold magnetocrystalline anisotropy constant K1 were derived from magnetic torque curves on the base of AMR results. It was found that the value of Ku increases with increasing deposition angle with respect to the surface normal, while the value of K1 remains almost constant for all the samples. Furthermore, by using MOKE results, the Ku values of the films deposited obliquely were also derived from the magnetization curves along hard axis. The results of AMR method were then compared with that of hard axis fitting method (coherent rotation) and found that both methods have almost identical values of UMA constant for each sample. Project supported by the Chinese Academy of Sciences-The World Academy of Sciences (CAS-TWAS) Fellowship Program, the National Basic Research Program of China (Grant Nos. 2015CB921403 and 2012CB933102), and the National Natural Science Foundation of China (Grant Nos. 51427801, 11374350, and 11274361).

  5. Quench Limit Calculation for Steady State Heat Deposits in LHC Inner Triplet Magnets

    CERN Document Server

    Cerutti, F; Esposito, L S; Siemko, A; Bocian, D

    2012-01-01

    In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. A Network Model is used to simulate the thermodynamic behavior of the superconducting magnets. In previous papers the validations of network model with measurements performed in the CERN and Fermilab magnet test facilities were presented. This model was subsequently used for thermal analysis of the current LHC inner triplet quadrupole magnets for beam energy of 3.5 TeV and 7.0 TeV. The detailed study of helium cooling channels efficiency for energy deposits simulated with FLUKA was performed. The expected LHC inner triplet magnets quench limit is presented.

  6. Structural and magnetic properties of Gd/Fe multilayers grown by pulsed laser deposition

    DEFF Research Database (Denmark)

    Kant, K. Mohan; Bahl, Christian Robert Haffenden; Pryds, Nini

    2010-01-01

    This work investigates the structural and the magnetic properties of Gd/Fe multilayered thin films grown by pulsed laser deposition onto Si (001) substrates at room temperature. he Fe layer thickness is varied from 70 to 150 nm and its effect on the structural and magnetic properties of Fe....../Gd/Fe sandwich multilayers has been explored. Gd films were found to change from amorphous to polycrystalline at a critical thickness of 20 nm....

  7. Spontaneous magnetization of aluminum nanowires deposited on the NaCl(100) surface

    OpenAIRE

    Ayuela, A.; Räbiger, H.; Puska, M. J.; Nieminen, R. M.

    2001-01-01

    We investigate electronic structures of Al quantum wires, both unsupported and supported on the (100) NaCl surface, using the density-functional theory. We confirm that unsupported nanowires, constrained to be linear, show magnetization when elongated beyond the equilibrium length. Allowing ions to relax, the wires deform to zig-zag structures with lower magnetization but no dimerization occurs. When an Al wire is deposited on the NaCl surface, a zig-zag geometry emerges again. The magnetizat...

  8. The effect of magnetic field on electrochemically deposited calcium phosphate/collagen coatings.

    Science.gov (United States)

    Zhao, Xueni; He, Jianpeng; Zhang, Jing; Wang, Xudong; Wang, Wanying

    2014-01-01

    Nanostructured calcium phosphate/collagen (CaP/COL) coatings were deposited on the carbon/carbon (C/C) composites through electrochemical deposition (ECD) under magnetic field. The effect of magnetic fields with different orientations on the morphology and composition was investigated. Both the morphology and composition of the coatings could be altered by superimposed magnetic field. Under zero magnetic field and magnetic field, three-dimensional network structure consisting of collagen fibers and CaP were formed on the C/C substrate. The applied magnetic field in the electric field helped to form nanostructured and plate-like CaP on collagen fibers. For the ECD under magnetic field, the Ca/P molar ratio of the coatings was lower than the one under B=0. This may be contributed to the decreased electrical resistance or the increased electrical conductivity of electrolyte solutions under magnetic field. The nanosized CaP/COL coatings exhibited the similar morphology to the human bone and could present excellent cell bioactivity and osteoblast functions.

  9. Corrosion product deposits on boiling-water reactor cladding: Experimental and theoretical investigation of magnetic properties

    Science.gov (United States)

    Orlov, A.; Degueldre, C.; Wiese, H.; Ledergerber, G.; Valizadeh, S.

    2011-09-01

    Recent Eddy current investigations on the cladding of nuclear fuel pins have shown that the apparent oxide layers are falsified due to unexpected magnetic properties of corrosion product deposits. Analyses by Scanning Electron Microscopy (SEM) or Electron Probe Micro Analysis (EPMA) demonstrated that the deposit layer consists of complex 3-d element oxides (Ni, Mn, Fe) along with Zn, since the reactor operates with a Zn addition procedure to reduce buildup of radiation fields on the recirculation system surfaces. The oxides crystallise in ferritic spinel structures. These spinels are well-known for their magnetic behaviour. Since non-magnetic zinc ferrite (ZnFe 2O 4) may become magnetic when doped with even small amounts of Ni and/or Mn, their occurrence in the deposit layer has been analyzed. The magnetic permeability of zinc ferrite, trevorite and jacobsite and their solid solutions are estimated by magnetic moment additivity. From the void history examination, the low elevation sample (810 mm) did not face significant boiling during the irradiation cycles suggesting growth of (Mn0.092+Zn0.752+Fe0.293+)[(Fe1.713+Mn0.032+Ni0.132+)O] crystals with theoretical value of the magnetic permeability for the averaged heterogeneous CRUD layer of 9.5 ± 3. Meanwhile, (Mn0.162+Zn0.552+Fe0.293+)[(Fe1.713+Mn0.042+Ni0.252+)O] crystallizes at the mid elevation (1810 mm) with theoretical magnetic permeability for the CRUD layer of 4.2 ± 1.5 at the investigated azimuthal location. These theoretical data are compared with the magnetic permeability of the corrosion product deposited layers gained from reactor pool side Eddy current (EC) analyses (9.0 ± 1.0 for low and 3.5 ± 1.0 for high elevation). The calculated thicknesses and magnetic permeability values of the deposition layers (estimated by MAGNACROX multifrequency EC method) match together with these estimated using an "ion magnetic moment additivity" model.

  10. Orientation of hyperfine magnetic fields of {alpha}-iron films produced by laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yasuike, Mamoru, E-mail: yyasu@rs.kagu.tus.ac.jp; Usui, Ryo; Yamada, Yasuhiro [Tokyo University of Science (Japan); Kobayashi, Yoshio [RIKEN (Japan)

    2012-03-15

    Iron films were produced by pulsed laser deposition (PLD) of iron in Ar gas and Moessbauer spectra of these films were obtained at room temperature. The orientation of the hyperfine magnetic field was found to vary depending on the pressure of the Ar gas. Iron films produced at low Ar pressures exhibited magnetic fields parallel to the substrate surface. The magnetic field became increasingly perpendicular to the substrate with increasing Ar pressure. Collisions with Ar gas molecules reduced the translational energies of laser-evaporated iron atoms and thus the orientation of crystals formed on the substrate varied depending on the Ar pressure.

  11. Magnetic property and recording performance of chemical deposition CoP thin films

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The thickness of CoP thin films prepared by wet chemical deposition is of crucial importance on magnetic property and recording perform-ance. The coercivity of CoP films decreased with increasing film thickness. The coercivity was 45.37 kA m 1 at the thickness of 300 nm, and decreased to 21.65 kA m 1 at 5.7 μm. Recording performance tests indicate that, for drums with the same size, different recorded magnetic pole density have different thickness requirements. For 40 mm diameter magnetic drum, the optimal ...

  12. Structure, growth and magnetic property of hard magnetic CoPtP nanowires synthesized by electrochemical deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ramulu, T.S.; Venu, R.; Anandakumar, S.; Rani, V. Sudha [Department of Materials Science and Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Yoon, S.S. [Department of Physics, Andong National University, Andong 760-749 (Korea, Republic of); Kim, C.G., E-mail: cgkim@cnu.ac.kr [Department of Materials Science and Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

    2012-06-30

    This paper reports the electrochemical synthesis and characterization of one dimensional hard magnetic CoPtP nanowires. Three electrode potentiostatic electrochemical technique was used to deposit nanowires into a nanoporous track-etched polycarbonate membrane with a nominal pore diameter 50 nm and thickness around 6-9 {mu}m. The room temperature electrolyte used for the deposition of nanowires consists of 60 g/lt CoSO{sub 4}7H{sub 2}O, 4.1 g/lt H{sub 2}PtCl{sub 6}, 4.5 g/lt NaHPO{sub 2} and 25 g/lt B(OH){sub 3}. The structural morphology was observed by scanning electron microscope and transmission electron microscope. The magnetic property of the nanowires was measured by vibrating sample magnetometer before removing the template. The coercive fields were measured to be 143 kA m{sup -1} and 103 kA m{sup -1} for parallel (H{sub Parallel-To }) and perpendicular to the nanowire axis, respectively. The higher coercivity value for H{sub Parallel-To} indicating nanowires' easy magnetization direction lies along the nanowires' axis. The average composition of the CoPtP nanowires was determined by electron dispersive spectroscopy and the crystallinity was measured by X-ray diffractometer. - Highlights: Black-Right-Pointing-Pointer CoPtP hard magnetic nanowires are synthesized by electrochemical deposition. Black-Right-Pointing-Pointer The synthesized magnetic nanowires are an average of 6 {mu}m in length. Black-Right-Pointing-Pointer Coercivity of nanowires is 143 kA m{sup -1} when the field is parallel to nanowire axis. Black-Right-Pointing-Pointer The magnetization direction of the nanowires lies along the nanowire's axis.

  13. A high power impulse magnetron sputtering model to explain high deposition rate magnetic field configurations

    Science.gov (United States)

    Raman, Priya; Weberski, Justin; Cheng, Matthew; Shchelkanov, Ivan; Ruzic, David N.

    2016-10-01

    High Power Impulse Magnetron Sputtering (HiPIMS) is one of the recent developments in the field of magnetron sputtering technology that is capable of producing high performance, high quality thin films. Commercial implementation of HiPIMS technology has been a huge challenge due to its lower deposition rates compared to direct current Magnetron Sputtering. The cylindrically symmetric "TriPack" magnet pack for a 10 cm sputter magnetron that was developed at the Center for Plasma Material Interactions was able to produce higher deposition rates in HiPIMS compared to conventional pack HiPIMS for the same average power. The "TriPack" magnet pack in HiPIMS produces superior substrate uniformity without the need of substrate rotation in addition to producing higher metal ion fraction to the substrate when compared to the conventional pack HiPIMS [Raman et al., Surf. Coat. Technol. 293, 10 (2016)]. The films that are deposited using the "TriPack" magnet pack have much smaller grains compared to conventional pack DC and HiPIMS films. In this paper, the reasons behind the observed increase in HiPIMS deposition rates from the TriPack magnet pack along with a modified particle flux model is discussed.

  14. Structural and magnetic studies of thin Fe57 films formed by ion beam assisted deposition

    Science.gov (United States)

    Lyadov, N. M.; Bazarov, V. V.; Vagizov, F. G.; Vakhitov, I. R.; Dulov, E. N.; Kashapov, R. N.; Noskov, A. I.; Khaibullin, R. I.; Shustov, V. A.; Faizrakhmanov, I. A.

    2016-08-01

    Thin Fe57 films with the thickness of 120 nm have been prepared on glass substrates by using the ion-beam-assisted deposition technique. X-ray diffraction, electron microdiffraction and Mössbauer spectroscopy studies have shown that as-deposited films are in a stressful nanostructured state containing the nanoscaled inclusions of α-phase iron with the size of ∼10 nm. Room temperature in-plane and out-of-plane magnetization measurements confirmed the presence of the magnetic α-phase in the iron film and indicated the strong effect of residual stresses on magnetic properties of the film as well. Subsequent thermal annealing of iron films in vacuum at the temperature of 450 °C stimulates the growth of α-phase Fe crystallites with the size of up to 20 nm. However, electron microdiffraction and Mössbauer spectroscopic data have shown the partial oxidation and carbonization of the iron film during annealing. The stress disappeared after annealing of the film. The magnetic behaviour of the annealed samples was characterized by the magnetic hysteresis loop with the coercive field of ∼10 mT and the saturation magnetization decreased slightly in comparison with the α-phase Fe magnetization due to small oxidation of the film.

  15. Magnetic field effects on the energy deposition spectra of MV photon radiation.

    Science.gov (United States)

    Kirkby, C; Stanescu, T; Fallone, B G

    2009-01-21

    Several groups worldwide have proposed various concepts for improving megavoltage (MV) radiotherapy that involve irradiating patients in the presence of a magnetic field-either for image guidance in the case of hybrid radiotherapy-MRI machines or for purposes of introducing tighter control over dose distributions. The presence of a magnetic field alters the trajectory of charged particles between interactions with the medium and thus has the potential to alter energy deposition patterns within a sub-cellular target volume. In this work, we use the MC radiation transport code PENELOPE with appropriate algorithms invoked to incorporate magnetic field deflections to investigate electron energy fluence in the presence of a uniform magnetic field and the energy deposition spectra within a 10 microm water sphere as a function of magnetic field strength. The simulations suggest only very minor changes to the electron fluence even for extremely strong magnetic fields. Further, calculations of the dose-averaged lineal energy indicate that a magnetic field strength of at least 70 T is required before beam quality will change by more than 2%.

  16. Permanent magnet microstructures using dry-pressed magnetic powders

    Science.gov (United States)

    Oniku, Ololade D.; Bowers, Benjamin J.; Shetye, Sheetal B.; Wang, Naigang; Arnold, David P.

    2013-07-01

    This paper presents microfabrication methods and performance analysis of bonded powder permanent magnets targeting dimensions ranging from 10 µm to greater than 1 mm. For the structural definition and pattern transfer, a doctor blade technique is used to dry press magnetic powders into pre-etched cavities in a silicon substrate. The powders are secured in the cavities by one of the three methods: capping with a polyimide layer, thermal reflow of intermixed wax-binder particles, or conformal coating with a vapor-deposited parylene-C film. A systematic study of micromagnets fabricated using these methods is conducted using three different types of magnetic powders: 50 µm Nd-Fe-B, 5 µm Nd-Fe-B and 1 µm barium ferrite powder. The isotropic magnets are shown to exhibit intrinsic coercivities (Hci) as high as 720 kA m-1, remanences (Br) up to 0.5 T and maximum energy products (BHmax) up to 30 kJ m-3, depending on the magnetic powder used. Process compatibility experiments demonstrate the potential for the magnets to withstand typical microfabrication chemical exposure and thermal cycles, thereby facilitating their integration into more complex process flows. The remanences are also characterized at elevated temperatures to determine thermal sensitivities and maximum operating temperature ranges.

  17. Atomic layer deposition of cobalt carbide films and their magnetic properties using propanol as a reducing agent

    Science.gov (United States)

    Sarr, Mouhamadou; Bahlawane, Naoufal; Arl, Didier; Dossot, Manuel; McRae, Edward; Lenoble, Damien

    2016-08-01

    The investigation of highly conformal thin films using Atomic Layer Deposition (ALD) is driven by a variety of applications in modern technologies. In particular, the emergence of 3D memory device architectures requires conformal materials with tuneable magnetic properties. Here, nanocomposites of carbon, cobalt and cobalt carbide are deposited by ALD using cobalt acetylacetonate with propanol as a reducing agent. Films were grown by varying the ALD deposition parameters including deposition temperature and propanol exposure time. The morphology, the chemical composition and the crystalline structure of the cobalt carbide film were investigated. Vibrating Sample Magnetometer (VSM) measurements revealed magnetic hysteresis loops with a coercivity reaching 500 Oe and a maximal saturation magnetization of 0.9 T with a grain size less than 15 nm. Magnetic properties are shown to be tuneable by adjusting the deposition parameters that significantly affect the microstructure and the composition of the deposited films.

  18. Magnetic and optical properties of the nickel thin film deposited by GLAD technique

    Directory of Open Access Journals (Sweden)

    Potočnik Jelena M.

    2014-01-01

    Full Text Available In this work, nickel thin film was deposited on glass sample using Glancing Angle Deposition (GLAD technique, to a thickness of 1 μm. Glass sample was positioned 15 degrees with respect to the nickel vapor flux. The nickel thin film was characterized by Atomic Force Microscopy (AFM, Magneto- Optical Kerr effect Microscopy and Spectroscopic Ellipsometry. According to an AFM cross-section imaging, it was found that the nickel thin film has a columnar structure. The values of the coercively, obtained from the magnetic hysteresis loops, were analyzed as a function of the sample rotation in the magnetic field. It was found that the direction of magnetization easy axis lies toward the structure growth. Optical properties of the nickel thin film were studied at the wavelength of 455 nm. From the shape of the refractive index and the extinction coefficient diagrams could be concluded that the nickel thin film has an optical anisotropy.

  19. Magnetic field effects on copper metal deposition from copper sulfate aqueous solution.

    Science.gov (United States)

    Udagawa, Chikako; Maeda, Aya; Katsuki, Akio; Maki, Syou; Morimoto, Shotaro; Tanimoto, Yoshifumi

    2014-05-01

    Effects of a magnetic field (≤0.5 T) on electroless copper metal deposition from the reaction of a copper sulfate aqueous solution and a zinc thin plate were examined in this study. In a zero field, a smooth copper thin film grew steadily on the plate. In a 0.38 T field, a smooth copper thin film deposited on a zinc plate within about 1 min. Then, it peeled off repeatedly from the plate. The yield of consumed copper ions increased about 2.1 times compared with that in a zero field. Mechanism of this magnetic field effect was discussed in terms of Lorentz force- and magnetic force-induced convection and local volta cell formation.

  20. EFFECT OF ELECTROLESS DEPOSITION CONDITIONS ON THE STRUCTURES AND THE MAGNETIC PERFORMANCES OF THE Co-Fe-P ALLOY

    Institute of Scientific and Technical Information of China (English)

    S.L. Wang; F.Q. Zeng

    2006-01-01

    Electroless Co-Fe-P alloys were deposited from an alkaline bath, containing boric acid as a buffer agent and sodium citrate as a complexing agent. As a result, with the increase of pH of the bath, the iron content of the deposit increased, whereas the cobalt and phosphorus contents decreased. The structure of the deposit was investigated using X-ray diffraction (XRD) and transmission electron microscope (TEM). The deposit consisted of hexahedron phase Co, cubic phase Fe-Co, and amorphous phase (crystalline). The magnetic performances of the deposit were studied using vibrating sample magnetometer (VSM). The more the content of Fe and the less the content of P (the content of Co being less), the better the magnetic performances of the deposit. The Co-Fe-P deposit was suitable for use as soft magnetic material.

  1. Epitaxial growth of magnetic ZnCuO thin films by pulsed laser deposition

    Science.gov (United States)

    Kim, Dong Hun; Kim, Tae Cheol; Lee, Seung Han; Jung, Hyun Kyu; Jeong, Jaeeun; Han, Seung Ho

    2017-02-01

    The crystal structure and magnetic properties of epitaxial ZnO thin films doped with 5 at% Cu on SrTiO3 (001) and (111) substrates were investigated. In the case of films deposited in oxygen, unique crystallographic growth directions on different substrates were observed, while a metallic phase was detected in films grown under vacuum. The Cu-doped ZnO thin films deposited on the SrTiO3 (111) substrates, with hexagonal structures, showed a single epitaxial relationship with the substrates, whereas those deposited on the SrTiO3 (001) substrates showed a double epitaxial growth mode. The epitaxial ZnCuO thin films deposited on the SrTiO3 (111) substrates under high vacuum exhibited a ferromagnetic signal at room temperature.

  2. Electrical and magnetic properties of ZnNiO thin films deposited by pulse laser deposition

    Institute of Scientific and Technical Information of China (English)

    Jie JIANG; Xue-tao WANG; Li-ping ZHU; Li-qiang ZHANG; Zhi-guo YANG; Zhi-zhen YE

    2011-01-01

    ZnNiO thin films with different contents of Ni (0-10 at.%) were fabricated on quartz and Si (100) substrates bY pulsed laser deposition (PLD).We measured the samples by X-ray diffraction (XRD),field-emission scanning electron microscope (FE-SEM),X-ray photoelectron spectroscopy (XPS),ultraviolet-visible spectrometer (UV-VIS),and Hall testing.When the Ni contents were below 3 at.%,partial Zn2+ ions were replaced by the Ni2+ ions without forming any other phases,which enhanced the conductivity of the film.When the Ni contents were above 3 at.%,Ni ions were at the interstitial sites,and Ni-related clusters and defects were able to emerge in the films,resulting in a worsening of electrical and optical properties.A ferromagnetic hysteresis with a coercive force of approximately 30 Oe was observed in the ZnNiO film with a Ni content of 3 at.% at room temperature.

  3. Effect of Magnetic Field on the Deposition of Transparent Diamond-Like Carbon ( DLC ) Films by RF-PCVD

    Institute of Scientific and Technical Information of China (English)

    HOU Hui-jun; ZhU Xia-gao; LIN Song-sheng; YUAN Zhen-hai; DAI Da-huang

    2004-01-01

    In order to deposit transparent and hard DLC films, magnetic field was introduced to enhance the plasma density of radiofrequency plasma chemical vapor deposition (RF-PCVD). In this paper, the configuration and computation of external magnetic field B are introduced. The restriction effect of magnetic field B on the charged particles and the effect of magnetic field B on the primary parameters-nonindependent power Pf and self-bias Uz were also studied. The mechanism of how magnetic field B affects self-bias Uz was analyzed.

  4. Plasma immersion ion implantation and deposition of DLC coating for modification of orthodontic magnets

    Energy Technology Data Exchange (ETDEWEB)

    Wongsarat, W. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Sarapirom, S. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); National Metal and Materials Technology Center, 114 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani, Bangkok 12120 (Thailand); Aukkaravittayapun, S. [National Metal and Materials Technology Center, 114 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani, Bangkok 12120 (Thailand); Jotikasthira, D. [Department of Odontology-Oral Pathology, Faculty of Dentistry, Chiang Mai University, Chiang Mai 50200 (Thailand); Boonyawan, D. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Yu, L.D., E-mail: yuld@fnrf.science.cmu.ac.th [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand)

    2012-02-01

    This study was aimed to use the plasma immersion ion implantation and deposition (PIII-D) technique to form diamond-like carbon (DLC) thin films on orthodontic magnets to solve the corrosion problem. To search for the optimal material modification effect, PIII-D conditions including gases, processing time, and pulsing mode were varied. The formation of DLC films was confirmed and characterized with Raman spectra. The intensity of the remnant magnetic field of the magnets and the hardness, adhesion and thickness of the thin films were then measured. A corrosion test was carried out using clinic dental fluid. Improved benefits including a satisfying hardness, adhesion, remnant magnetic strength and corrosion resistance of the DLC coating could be achieved by using a higher interrupting time ratio and shorter processing time.

  5. Investigation of magnetic properties for oblique deposited granular films by magnetic field annealing

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Bangmin [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Ge Shihui, E-mail: gesh@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Zuo Huaping; Xiao Yuhua; Wang Guowei; Zhang Li [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2010-08-15

    A series of (Fe{sub 57}Co{sub 24}Ni{sub 4}Nb{sub 2}B{sub 13}){sub x}-(SiO{sub 2}){sub 1-x} nano-granular thin films were fabricated by magnetron sputtering with different oblique incidence angle {theta} and excellent soft magnetic properties are achieved. Based on the results of magnetic field anneal at different temperature T{sub a}, it is evidenced that orientation of atomic pairs contributes to the annealing treatment, and could manipulate magnetic anisotropy. The damping coefficient {alpha} decreases with increasing angle {theta} and this is ascribed to the anisotropy dissipation.

  6. Influence of resonant magnetic perturbations on transient heat load deposition and fast ion losses

    Energy Technology Data Exchange (ETDEWEB)

    Rack, Michael Thomas

    2014-07-11

    Thermonuclear fusion is the energy conversion process which keeps the sun shining. For the last six decades, researchers have been investigating the physics involved in order to enable the usage of this energy supply on Earth. The most promising candidates for fusion power plants are based on magnetic confinement of plasma to provide the ideal conditions for efficient thermonuclear fusion in well controlled surroundings. One important aspect is the control of instabilities that occur in the edge region of the plasma and lead to an ejection of huge amounts of energy. Magnetic perturbation fields which are resonant in the plasma edge are found to modify the plasma favourably and reduce the impact of these instabilities. This dissertation focuses on the effects of resonant magnetic perturbation fields on the ejected energy as well as on the drawbacks of these perturbation fields. The transient energy ejection which is triggered by the instabilities causes extreme heat loads on the wall components in fusion devices. Therefore, it is crucial to understand how resonant magnetic perturbation fields affect the heat load deposition. Furthermore, the impact of resonant magnetic perturbation fields on the confinement of fast ions is an important aspect as fast ions are still required to be well confined in order to avoid additional wall loads and increase the fusion efficiency. Recent upgrades on the Joint European Torus allow for a detailed study of the heat load deposition profiles caused by transient events. Throughout this work, the new features are used for the study of the modifications of the transient heat load depositions that occur if resonant magnetic perturbation fields are applied. This leads to a further understanding of the processes involved during the plasma edge instabilities. Additionally, an alternative method using lower hybrid waves for applying resonant magnetic perturbations is investigated. Furthermore, a new diagnostic, capable of detecting fast ion

  7. Synthesis of magnetic tunnel junctions with full in situ atomic layer and chemical vapor deposition processes

    Energy Technology Data Exchange (ETDEWEB)

    Mantovan, R., E-mail: roberto.mantovan@mdm.imm.cnr.it [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (Italy); Vangelista, S.; Kutrzeba-Kotowska, B.; Cocco, S.; Lamperti, A.; Tallarida, G. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Mameli, D. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (Italy); Dipartimento di Scienze Chimiche, Universita di Cagliari, Cittadella Universitaria, 09042 Monserrato, Cagliari (Italy); Fanciulli, M. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (Italy); Dipartimento di Scienza dei Materiali, Universita degli studi Milano-Bicocca, Via R Cozzi 53, 20125 Milano (Italy)

    2012-05-01

    Magnetic tunnel junctions, i.e. the combination of two ferromagnetic electrodes separated by an ultrathin tunnel oxide barrier, are core elements in a large variety of spin-based devices. We report on the use of combined chemical vapor and atomic layer deposition processes for the synthesis of magnetic tunnel junctions with no vacuum break. Structural, chemical and morphological characterizations of selected ferromagnetic and oxide layers are reported, together with the evidence of tunnel magnetoresistance effect in patterned Fe/MgO/Co junctions.

  8. High-purity cobalt thin films with perpendicular magnetic anisotropy prepared by chemical vapor deposition

    Science.gov (United States)

    Ootera, Yasuaki; Shimada, Takuya; Kado, Masaki; Quinsat, Michael; Morise, Hirofumi; Nakamura, Shiho; Kondo, Tsuyoshi

    2015-11-01

    A study of the chemical vapor deposition (CVD) of high-purity cobalt thin films is described. The Co layer prepared by a thermal CVD technique with a Pt/Ta underlayer and a Pt cap layer shows a saturation magnetization (Ms) of ∼1.8 T and perpendicular magnetic anisotropy (PMA) with an anisotropy energy (Ku) of ∼105 J/m3. The cobalt thickness dependence of Ku reveals that the interfacial anisotropy at the Pt/Co interface is most likely the origin of the obtained PMA.

  9. Multipolarity remanences in lower oceanic crustal gabbros recovered by drilling at Hess Deep (Integrated Ocean Drilling Program Expedition 345)

    Science.gov (United States)

    Morris, Antony; Horst, Andrew; Friedman, Sarah; Nozaka, Toshio

    2015-04-01

    A long-term goal of the scientific ocean drilling community is to understand the processes by which the ocean crust is constructed through magmatism, deformation, metamorphism and hydrothermal cooling. Insights into the magnetic properties of the lower crust have come from drilling at oceanic core complexes and in tectonic windows. At the Hess Deep Rift, propagation of the Cocos-Nazca Ridge into young, fast-spreading East Pacific Rise crust exposes a dismembered, but nearly complete lower crustal section. Here, IODP Expedition 345 (Site U1415) recovered primitive plutonic lithologies including gabbro, troctolitic gabbro and olivine gabbronorite. These rocks exhibit cumulate textures similar to those found in layered basic intrusions and some ophiolite complexes. Metamorphism is dominated by background greenschist facies alteration associated with cataclastic deformation that likely results from Cocos-Nazca rifting. Some intervals display complex, multiple remanence components within individual samples. A high temperature component unblocks above 500°-520°C and an intermediate temperature component of nearly antipodal direction unblocks between 425°-450°C and 500°-520°C. In addition, a few samples display a third component that unblocks between 100-350°C that is nearly parallel to the highest temperature component. These multiple, nearly antipodal components suggest that remanence was acquired in different geomagnetic chrons, and represent the first multipolarity remanences seen in Pacific lower oceanic crust. Similar remanence structures, however, have been reported in lower crustal gabbros recovered from slow-spreading rate crust along the Mid-Atlantic Ridge, and have been interpreted to reflect protracted accretion or protracted cooling. In contrast, at Hess Deep unblocking temperatures appear consistent with temperatures inferred for successive phases of alteration, suggesting an alteration history spanning at least two polarity chrons.

  10. Surface Passivation of ZrO2 Artificial Dentures by Magnetized Coaxial Plasma deposition

    Science.gov (United States)

    Arai, Soya; Kurumi, Satoshi; Matsuda, Ken-Ichi; Suzuki, Kaoru; Hara, Katsuya; Kato, Tatsuya; Asai, Tomohiko; Hirose, Hideharu; Masutani, Shigeyuki; Nihon University Team

    2015-09-01

    Recent growth and fabrication technologies for functional materials have been greatly contributed to drastic development of oral surgery field. Zirconia based ceramics is expected to utilize artificial dentures because these ceramics have good biocompatibility, high hardness and aesthetic attractively. However, to apply these ceramics to artificial dentures, this denture is removed from a dental plate because of weakly bond. For improving this problem, synthesis an Al passivation-layer on the ceramics for bonding with these dental items is suitable. In order to deposit the passivation layer, we focused on a magnetized coaxial plasma deposition (MCPD). The greatest characteristic of MCPD is that high-melting point metal can be deposited on various substrates. Additionally, adhesion force between substrate and films deposited by the MCPD is superior to it of general deposition methods. In this study, we have reported on the growth techniques of Al films on ZrO2 for contributing to oral surgery by the MCPD. Surface of deposited films shows there were some droplets and thickness of it is about 200 nm. Thickness is increased to 500 nm with increasing applied voltage.

  11. Damage layer study of the overcoat deposited on the top magnetic layer of hard disks

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, R.H. [Department of Photonics and Communication Engineering, Asia University, Taichung 41354, Taiwan (China); Chao, T.M. [Department of Applied Geomatics, Chien-Hsin University, JungLi 32097, Taiwan (China); Tan, A.H., E-mail: ahtan@uch.edu.tw [Department of Mechanical Engineering, Chien-Hsin University, JungLi 32097, Taiwan (China)

    2014-02-15

    This paper presents the effect of nanoscale damage layer on magnetic results obtained from the optimization of media overcoat deposition parameters on the top magnetic layer on magnetic hard disks. We have investigated the effects of interface interaction between the overcoat deposition parameters on the top magnetic layer on the media by using a plasma enhanced chemical vapor deposition (PECVD) on next generation hard disks. The goal is to achieve a reduced damage layer, lower head media spacing (HMS) and a higher spectrum of signal to noise ratio (SpSNR) optimized by using Taguchi experimental design with a four-factor three-level (L9) orthogonal array. An analysis of variance (ANOVA) was carried out to interpret the measured coercivity (Hc), HMS and SpSNR. It was found that source gas type is the most significant factor with a percentage contribution effect of 59.8% on HMS and 51.7% on SpSNR. The bias voltage is the second most significant factor with its percentage contribution being 24.2% on HMS and 31.0% on SpSNR. Overall, the optimum SpSNR was obtained using a C{sub 2}H{sub 2} source gas, −100 V bias voltage, 50 V anode voltage and 20 sccm gas flow rate, respectively. - Highlights: • Taguchi method and analysis of variance (ANOVA) are used in this study. • The optimal DLC deposition parameters are C{sub 2}H{sub 2} source gas, −100 V bias voltage, 50 V anode voltage and 20 sccm gas flow rate. • Compared with current design, optimum design can achieve a 0.56 nm lower HMS, a 0.51 dB higher SpSNR and better wear resistance. • The source gas type is the most significant factor with a percentage contribution effect of 59.8% on HMS and 51.7% on SpSNR.

  12. Assessment of Rock Magnetic Parameters for Fly Ash Pollution Screening in Topsoil of the Deccan Trap Basalt Area, India

    Science.gov (United States)

    Blaha, U.; Basavaiah, N.; Das, P. K.; Deenadayalan, K.

    2012-04-01

    Rock magnetic parameters of highly magnetic topsoil of the Deccan Trap basalt area are evaluated for their suitability for efficient environmental magnetic pollution screening. Parameters, such as magnetic susceptibility (χ), frequency dependence of magnetic susceptibility (κ fd%), anhysteretic remanent magnetization (ARM), saturation isothermal remanent magnetization (SIRM), soft isothermal remanent magnetization (Soft IRM), as well as thermo-magnetic analysis (κ-T) are compared and assessed for best depiction of topsoil contamination due to ash deposition around the Nashik thermal power station (NTPS). Fifty-five topsoil samples, collected along north-south and west-east stretching transects of 24 km length, are the basis for evaluation of the specific ash distribution pattern around the plant and its adjacent ash pond. Similar decline of the magnetic signals with increasing distance from the point source is observed in the concentration dependent magnetic parameters and can be modeled. The magnetic grain size parameters instead reveal increasing trends with increasing distance. Verwey-transition and Hopkinson peak obtained from κ-T analyses demonstrate to be important parameters to prove fly ash accumulation in soils of basaltic origin. The importance of magnetic parameters for indirect tracing of pollutants, such as heavy metals, is shown by Pb, Zn and Cu data, revealing similar distribution pattern as obtained from the concentration dependent magnetic parameters. Confirmation of the presence of a very high amount of ash particles in the vicinity of the NTPS and a low number of particles in more distant areas is provided by scanning electron microscopy (SEM) on quantitatively extracted magnetic particles at 5.5 km and 11.9 km distance in eastern direction. The investigation demonstrates that the majority of the rock magnetic parameters has the potential to be successfully applied in environmental magnetic studies in areas with high magnetic background

  13. Magnetic properties dependence on the coupled effects of magnetic fields on the microstructure of as-deposited and post-annealed Co/Ni bilayer thin films

    Energy Technology Data Exchange (ETDEWEB)

    Franczak, Agnieszka [LISM, Universite de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France); Department of Materials Science, Katholieke Universiteit Leuven, 3001 Leuven (Belgium); Levesque, Alexandra, E-mail: alexandra.levesque@univ-reims.fr [LISM, Universite de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France); Coïsson, Marco [Electromagnetism Division, Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Li, Donggang [LISM, Universite de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France); Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, 110004 Shenyang (China); Barrera, Gabriele [Electromagnetism Division, Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Università di Torino, Dipartimento di Chimica, 10125 Torino (Italy); Celegato, Federica [Electromagnetism Division, Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Wang, Qiang [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, 110004 Shenyang (China); Tiberto, Paola [Electromagnetism Division, Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Chopart, Jean-Paul [LISM, Universite de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France)

    2014-12-15

    Magnetic films and multilayers are the focus of much attention motivated mainly by their wide range of applications, such as magnetic data storage devices and sensors. The magnetic multilayer structures are normally prepared through physical means of deposition, as molecular beam epitaxy (MBE) or sputtering. However, there are already examples of materials produced by electrochemical routes, which share with the other deposition techniques a high sensitivity of magnetic and transport properties of the samples on their crystallographic and chemical structure. In addition, electrochemical deposition allows growing structures with high aspect ratio, which are not possible to obtain by MBE deposition followed by lithographic processes. The present work investigates the Co/Ni bilayered nanocrystalline films produced through the temperature-elevated electrochemical deposition, and modified by annealing carried out also under an external magnetic field. The results indicate an increase of the coercive field of deposited Co/Ni bilayers, when the electrodeposition process was conducted under magnetic field of 1 T. The annealing processing caused further remarkable increase of the coercive field of as-prepared bilayers that has been preserved under magnetic annealing conditions. The magnetic properties are discussed in terms of samples microstructure. In as-prepared samples the in-plane magnetization was observed, while high temperature treatment, causing microstructural changes in the film, resulted also in appearance of a small component of magnetization oriented perpendicularly to the films’ plane that could have been observed by MFM analysis. The induced perpendicular magnetization component in the post-annealed samples was a result of the magnetic field applied in the perpendicular direction to the samples’ surface during annealing treatment. - Highlights: • Co deposits were obtained at high electrolyte temperature under applied B-field. • The

  14. Optimization of exchange bias in Co/CoO magnetic nanocaps by tuning deposition parameters

    Science.gov (United States)

    Sharma, A.; Tripathi, J.; Ugochukwu, K. C.; Tripathi, S.

    2017-03-01

    In the present work, we report exchange bias tuning by varying thin film deposition parameters such as synthesis method and underlying layer patterning. The patterned substrates for this study were prepared by self-assembly of polystyrene (PS) latex spheres ( 530 nm) on Si (100) substrate. The desired magnetic nanocaps composed of CoO/Co bilayer film on these patterned substrates were prepared by molecular beam epitaxy technique under ultra-high vacuum conditions. For this, a Co layer of 10 nm thickness was deposited on the substrates and then oxidized in-situ to form CoO/Co/PS in-situ oxidized film or ex-situ in ambiance which also gives CoO/Co/PS naturally oxidized film. Simultaneously, reference thin films of Co ( 10 nm) were also prepared on plane Si substrate and similar oxidation treatments were performed on them respectively. The magnetic properties studied using SQUID technique revealed higher exchange bias ( 1736 Oe) in the in-situ oxidized Co/PS film as compared to that in naturally oxidized Co/PS film ( 1544 Oe) and also compared to the reference film. The observed variations in the magnetic properties are explained in terms of surface patterning induced structural changes of the deposited films and different oxidation methods.

  15. On the magnetic properties of iron nanostructures fabricated via focused electron beam induced deposition and autocatalytic growth processes

    Science.gov (United States)

    Tu, F.; Drost, M.; Vollnhals, F.; Späth, A.; Carrasco, E.; Fink, R. H.; Marbach, H.

    2016-09-01

    We employ Electron beam induced deposition (EBID) in combination with autocatalytic growth (AG) processes to fabricate magnetic nanostructures with controllable shapes and thicknesses. Following this route, different Fe deposits were prepared on silicon nitride membranes under ultra-high vacuum conditions and studied by scanning electron microscopy (SEM) and scanning transmission x-ray microspectroscopy (STXM). The originally deposited Fe nanostructures are composed of pure iron, especially when fabricated via autocatalytic growth processes. Quantitative near-edge x-ray absorption fine structure (NEXAFS) spectroscopy was employed to derive information on the thickness dependent composition. X-ray magnetic circular dichroism (XMCD) in STXM was used to derive the magnetic properties of the EBID prepared structures. STXM and XMCD analysis evinces the existence of a thin iron oxide layer at the deposit-vacuum interface, which is formed during exposure to ambient conditions. We were able to extract magnetic hysteresis loops for individual deposits from XMCD micrographs with varying external magnetic field. Within the investigated thickness range (2-16 nm), the magnetic coercivity, as evaluated from the width of the hysteresis loops, increases with deposit thickness and reaches a maximum value of ˜160 Oe at around 10 nm. In summary, we present a viable technique to fabricate ferromagnetic nanostructures in a controllable way and gain detailed insight into their chemical and magnetic properties.

  16. Insights into deposition and deformation of intra-caldera ignimbrites, central Nevada

    Science.gov (United States)

    MacDonald, William D.; Palmer, H. Currie; Deino, Alan L.; Shen, Po-Yu

    2012-11-01

    Magnetic studies, together with structural and 40Ar/39Ar age analyses, were used to investigate the development and deformation of ignimbrites of the Caetano Tuff formation in central-north Nevada. Magnetic susceptibility, susceptibility anisotropy (AMS) and magnetic remanence approaches were used to decipher events accompanying emplacement and subsequent deformation of that tuff, for both intracaldera tuffs and outflow deposits. 40Ar/39Ar ages, both those presented here and previously published ages, indicate about 33.8 Ma for the age of Caetano ignimbrites, approximately at the Eocene/Oligocene boundary. Although extensive faulting associated with regional extension of the Great Basin region has dissected these deposits, the thickness of the intra-caldera ignimbrites has been estimated at 3.5 km or more. Thermal modeling for cooling of a caldera filling of 3.5 km thickness indicates acquisition of remanent magnetization can persist up to 25 ka, sufficient to average secular variation. This contrasts with rapid cooling and remanence acquisition in outflow ignimbrites typically only tens of meters thick. A 750 m thick reference section was selected for more detailed study about 10 km to the west of the type area. This reference section, fault-bounded at both base and top, represents the upper part of the formation. Its lower member includes the uppermost 250 m of the lower massive resistant unit of ignimbrites, a middle member of 375 m of well stratified pyroclastic deposits, vitrophyres and sediments, and an upper member of about 125 m of recessive ignimbrite and thin-bedded clastic and pyroclastic deposits. Structural and magnetic remanence measurements suggest 13° eastward tilting of the caldera floor occurred early during deposition of the middle member. Flow directions inferred from AMS Kmax axes in the middle member diverge about 45° relative to those in the underlying member and suggest a change in vent source accompanying the deposition of the middle

  17. Beta Beams for Neutrino Production Heat Deposition from Decaying Ions in Superconducting Magnets

    CERN Document Server

    Wildner, Elena; Cerutti, F

    2008-01-01

    This report describes studies of energy deposition in superconducting magnets from secondary ions in the "beta beam" decay ring as described in the base-line scenario of the EURISOL Beta Beam Design Study. The lattice structure proposed in the Design Study has absorber elements inserted between the superconducting magnets to protect the magnet coils. We describe an efficient and small model made to carry out the study. The specially developed options in the beam code "ACCSIM" to track largely off-momentum particles has permitted to extract the necessary information to interface the transport and interaction code "FLUKA" with the aim to calculate the heat deposition in the magnets and the absorbers. The two beta emitters 18Ne10+ and 6He2+ used for neutrino and anti-neutrino production and their daughter ions have been tracked. The absorber system proposed in the Design Study is efficient to intercept the ions decayed in the arc straight sections as foreseen, however, the continuous decay in the dipoles induce ...

  18. Beta Beams for neutrino production: Heat deposition from decaying ions in superconducting magnets

    CERN Document Server

    Wildner, Elena; Cerutti, Francesco

    This note describes studies of energy deposition in superconducting magnets from secondary ions in the “beta beam” decay ring as described in the base-line scenario of the EURISOL Beta Beam Design Study. The lattice structure proposed in the Design Study has absorber elements inserted between the superconducting magnets to protect the magnet coils. We describe an efficient and small model made to carry out the study. The specially developed options in the beam code “ACCSIM” to track largely off-momentum particles has permitted to extract the necessary information to interface the transport and interaction code “FLUKA” with the aim to calculate the heat deposition in the magnets and the absorbers. The two beta emitters 18Ne10+ and 6He2+ used for neutrino and anti-neutrino production and their daughter ions have been tracked. The absorber system proposed in the Design Study is efficient to intercept the ions decayed in the arc straight sections as foreseen, however, the continuous decay in the dipol...

  19. Electron holography study of remanence states in exchange-biased MnPd/Fe bilayers grown epitaxially on MgO(001).

    Science.gov (United States)

    Jeong, Jong Seok; Akase, Zentaro; Shindo, Daisuke; Zhan, Qing-Feng; Krishnan, Kannan M

    2011-01-01

    We investigated magnetic remanence states of epitaxially grown, exchange-biased MnPd/Fe bilayers by electron holography emphasizing the crystallographic orientations of the layers. Thin-foil transmission electron microscopy (TEM) specimens were carefully prepared along both hard and easy axes of the Fe layer. The ex situ magnetization-reversal process was carried out using the TEM specimens, and magnetic flux densities of the ultra-thin Fe layers were evaluated at different remanence states. We show that a spin configuration in the TEM specimens is determined by the competition between an exchange coupling at the MnPd/Fe bilayer interface, shape anisotropy of TEM specimens and intrinsic magnetocrystalline anisotropy of Fe.

  20. Effective magnetic anisotropy manipulation by oblique deposition in magnetostatically coupled Co nanostrip arrays

    Science.gov (United States)

    Kozlov, A. G.; Stebliy, M. E.; Ognev, A. V.; Samardak, A. S.; Davydenko, A. V.; Chebotkevich, L. A.

    2017-01-01

    We report on an experimental investigation of magnetic properties and domain structure of single nanostrips and their magnetostatically coupled arrays possessing the shape anisotropy and anisotropy induced by oblique deposition, which are oriented at different angles to each other. The orientation of the effective anisotropy and the value of coercive force of nanostrip arrays depends on the angle between directions of the induced anisotropies. Micromagnetic simulations, performed to determine possible spin configurations especially within domain walls, support the experimentally observed magnetic domain structure. An influence of dipole-dipole interaction between magnetostatically coupled nanostrips on the domain structure and coercive force of arrays are discussed. We demonstrate the experimental validation of an early-proposed theoretical model for determination of the effective magnetic anisotropy through the combination of induced anisotropies.

  1. Magnetic and cytotoxic properties of hot-filament chemical vapour deposited diamond

    Energy Technology Data Exchange (ETDEWEB)

    Zanin, Hudson, E-mail: hudsonzanin@gmail.com [Faculdade de Engenharia Eletrica e Computacao, Departamento de Semicondutores, Instrumentos e Fotonica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N.400, CEP 13 083-852 Campinas, Sao Paulo (Brazil); Peterlevitz, Alfredo Carlos; Ceragioli, Helder Jose [Faculdade de Engenharia Eletrica e Computacao, Departamento de Semicondutores, Instrumentos e Fotonica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N.400, CEP 13 083-852 Campinas, Sao Paulo (Brazil); Rodrigues, Ana Amelia; Belangero, William Dias [Laboratorio de Biomateriais em Ortopedia, Faculdade de Ciencias Medicas, Universidade Estadual de Campinas, Rua Cinco de Junho 350 CEP 13083970, Campinas, Sao Paulo (Brazil); Baranauskas, Vitor [Faculdade de Engenharia Eletrica e Computacao, Departamento de Semicondutores, Instrumentos e Fotonica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N.400, CEP 13 083-852 Campinas, Sao Paulo (Brazil)

    2012-12-01

    Microcrystalline (MCD) and nanocrystalline (NCD) magnetic diamond samples were produced by hot-filament chemical vapour deposition (HFCVD) on AISI 316 substrates. Energy Dispersive X-ray Spectroscopy (EDS) measurements indicated the presence of Fe, Cr and Ni in the MCD and NCD samples, and all samples showed similar magnetisation properties. Cell viability tests were realised using Vero cells, a type of fibroblastic cell line. Polystyrene was used as a negative control for toxicity (NCT). The cells were cultured under standard cell culture conditions. The proliferation indicated that these magnetic diamond samples were not cytotoxic. - Highlights: Black-Right-Pointing-Pointer Polycrystalline diamonds doped with Fe, Cr and Ni acquire ferromagnetic properties. Black-Right-Pointing-Pointer CVD diamonds have been prepared with magnetic and semiconductor properties. Black-Right-Pointing-Pointer Micro/nanocrystalline diamonds show good cell viability with fibroblast proliferation.

  2. How to obtain a magnetic hard-soft architecture by pulsed laser deposition.

    Science.gov (United States)

    Fix, T; Trassin, M; Hassan, R Sayed; Schmerber, G; Viart, N; Mény, C; Colis, S; Dinia, A

    2007-12-12

    In spin valve type systems, one ferromagnetic electrode must be magnetically hard to act as a reference layer while the other electrode must be magnetically soft to act as a sensor or storage layer. This magnetic hard-soft architecture can usually be obtained by four different methods: the use of two ferromagnets with different coercive fields (here CoFe(2) and Ni(80)Fe(20)), the use of an underlayer enhancing the coercive field of one of the two ferromagnets (here Ta and Ru), the use of a ferromagnet coupled to a ferrimagnet or antiferromagnet (here NiO/CoFe(2) and CoFe(2)O(4)/CoFe(2)), or the use of an artificial antiferromagnet (here CoFe(2)/Ru/CoFe(2)). We show that at least the first and the third methods seem to work with pulsed laser deposition in the thermodynamic conditions used.

  3. Structure, morphology, and magnetic properties of Fe nanoparticles deposited onto single-crystalline surfaces

    Directory of Open Access Journals (Sweden)

    Armin Kleibert

    2011-01-01

    Full Text Available Background: Magnetic nanostructures and nanoparticles often show novel magnetic phenomena not known from the respective bulk materials. In the past, several methods to prepare such structures have been developed – ranging from wet chemistry-based to physical-based methods such as self-organization or cluster growth. The preparation method has a significant influence on the resulting properties of the generated nanostructures. Taking chemical approaches, this influence may arise from the chemical environment, reaction kinetics and the preparation route. Taking physical approaches, the thermodynamics and the kinetics of the growth mode or – when depositing preformed clusters/nanoparticles on a surface – the landing kinetics and subsequent relaxation processes have a strong impact and thus need to be considered when attempting to control magnetic and structural properties of supported clusters or nanoparticles.Results: In this contribution we focus on mass-filtered Fe nanoparticles in a size range from 4 nm to 10 nm that are generated in a cluster source and subsequently deposited onto two single crystalline substrates: fcc Ni(111/W(110 and bcc W(110. We use a combined approach of X-ray magnetic circular dichroism (XMCD, reflection high energy electron diffraction (RHEED and scanning tunneling microscopy (STM to shed light on the complex and size-dependent relation between magnetic properties, crystallographic structure, orientation and morphology. In particular XMCD reveals that Fe particles on Ni(111/W(110 have a significantly lower (higher magnetic spin (orbital moment compared to bulk iron. The reduced spin moments are attributed to the random particle orientation being confirmed by RHEED together with a competition of magnetic exchange energy at the interface and magnetic anisotropy energy in the particles. The RHEED data also show that the Fe particles on W(110 – despite of the large lattice mismatch between iron and tungsten – are

  4. 3D fibre deposition and stereolithography techniques for the design of multifunctional nanocomposite magnetic scaffolds.

    Science.gov (United States)

    De Santis, Roberto; D'Amora, Ugo; Russo, Teresa; Ronca, Alfredo; Gloria, Antonio; Ambrosio, Luigi

    2015-10-01

    Magnetic nanocomposite scaffolds based on poly(ε-caprolactone) and poly(ethylene glycol) were fabricated by 3D fibre deposition modelling (FDM) and stereolithography techniques. In addition, hybrid coaxial and bilayer magnetic scaffolds were produced by combining such techniques. The aim of the current research was to analyse some structural and functional features of 3D magnetic scaffolds obtained by the 3D fibre deposition technique and by stereolithography as well as features of multimaterial scaffolds in the form of coaxial and bilayer structures obtained by the proper integration of such methods. The compressive mechanical behaviour of these scaffolds was investigated in a wet environment at 37 °C, and the morphological features were analysed through scanning electron microscopy (SEM) and X-ray micro-computed tomography. The capability of a magnetic scaffold to absorb magnetic nanoparticles (MNPs) in water solution was also assessed. confocal laser scanning microscopy was used to assess the in vitro biological behaviour of human mesenchymal stem cells (hMSCs) seeded on 3D structures. Results showed that a wide range of mechanical properties, covering those spanning hard and soft tissues, can be obtained by 3D FDM and stereolithography techniques. 3D virtual reconstruction and SEM showed the precision with which the scaffolds were fabricated, and a good-quality interface between poly(ε-caprolactone) and poly(ethylene glycol) based scaffolds was observed for bilayer and coaxial scaffolds. Magnetised scaffolds are capable of absorbing water solution of MNPs, and a preliminary information on cell adhesion and spreading of hMSCs was obtained without the application of an external magnetic field.

  5. Characterization of 2004 Indian Ocean tsunami induced deposits along the Chennai coast using magnetic and geochemical techniques

    Digital Repository Service at National Institute of Oceanography (India)

    Veerasingam, S.; Venkatachalapathy, R.

    measurements, as a proxy tool to identify tsunami induced deposits in the core sediments from the Chennai coast, India Down core profiles of mass specific magnetic susceptibility (x variable), x variable ARM and SIRM are similar in all sediment cores...

  6. Parametric Study of Heat Deposition from Collision Debris into the Insertion Superconducting Magnets for the LHC Luminosity Upgrade

    CERN Document Server

    Hoa, C; Cerutti, F; Koutchouk, Jean-Pierre; Sterbini, G; Wildner, E

    2007-01-01

    With a new geometry in a higher luminosity environment, the power deposition in the superconducting magnets becomes a critical aspect to analyze and to integrate in the insertion design. In this paper, we quantify the power deposited in magnets insertion at variable positions from the interaction point (IP). A fine characterization of the debris due to the proton-proton collisions at 7 TeV, shows that the energetic particles in the very forward direction give rise to non intuitive dependences of the impacting energy on the magnet front face and inner surface. The power deposition does not vary significantly with the distance to the interaction point, because of counterbalancing effects of different contributions to power deposition. We have found out that peak power density in the magnet insertion does not vary significantly with or without the Target Absorber Secondaries (TAS) protection.

  7. Effect of deposition technique of Ni on the perpendicular magnetic anisotropy in Co/Ni multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Akbulut, S., E-mail: sakbulut@gtu.edu.tr [Gebze Technical University, Physics Department, Istanbul Cad, PK 41400 Gebze/Kocaeli (Turkey); Akbulut, A. [Gebze Technical University, Physics Department, Istanbul Cad, PK 41400 Gebze/Kocaeli (Turkey); Özdemir, M. [Marmara University, Physics Department, Göztepe, Istanbul (Turkey); Yildiz, F., E-mail: fyildiz@gtu.edu.tr [Gebze Technical University, Physics Department, Istanbul Cad, PK 41400 Gebze/Kocaeli (Turkey)

    2015-09-15

    The perpendicular magnetic anisotropy (PMA) of Si/Pt 3.5/(Co 0.3/Ni 0.6){sub n} /Co 0.3/ Pt 3 (all thicknesses are nm) multilayers were investigated for two different sample sets by using ferromagnetic resonance (FMR) and magnetooptic Kerr effect (MOKE) techniques. In the first sample set all layers (buffer, cap, Co and Ni) were grown by magnetron sputtering technique while in the second sample set Ni sub-layers were grown by molecular beam epitaxy (MBE) at high vacuum. Apart from deposition technique of Ni, all other parameters like thicknesses and growth rates of each layers are same for both sample sets. Multilayers in these two sample sets display PMA in the as grown state until a certain value of bilayer repetition (n) and the strength of PMA decreases with increasing n. Magnetic easy axis's of the multilayered samples switched from film normal to the film plane when n is 9 and 5 for the first and second sample sets, respectively. The reason for that, PMA was decreased due to increasing roughness with increasing n. This was confirmed by X Ray Reflectivity (XRR) measurements for both sample sets. Moreover, in the first sample set coercive field values are smaller than the second sample set, which means magnetic anisotropy is lower than the latter one. This stronger PMA is arising due to existence of stronger Pt (111) and Co/Ni (111) textures in the second sample set. - Highlights: • Effect of deposition techniques for Ni sub-layers on magnetic properties in [Co/Ni]{sub n} multilayered films was studied. • Ni sub-layers were deposited by two different techniques, molecular beam epitaxy (MBE) and magnetron sputtering. • Spin reorientation thickness and magnitude of the anisotropy are strongly depending on growing techniques.

  8. Electrodeposition of magnetic thin films of cobalt on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Munford, M.L.; Seligman, L.; Sartorelli, M.L.; Voltolini, E.; Martins, L.F.O.; Schwarzacher, W.; Pasa, A.A. E-mail: pasa@fisica.ufsc.br

    2001-05-01

    To understand the electrodeposition of Co on Si, sulphate electrolytes containing two different Co ion concentrations were tested. Thin films with uniform thickness, ranging from 10 to 700 nm, low surface roughness, compact and metallic appearance were obtained for Co concentrations of 26 and 104 mM, respectively. Transverse MOKE measurements showed in-plane magnetization with the magnitude of the coercive field being dependent on the thickness of the deposited layers. VSM measurements with the applied field perpendicular to the surface allowed the observation of an out-of-plane remanent magnetization. These properties are of considerable interest for technological applications.

  9. Enhancement of in-plane uniaxial magnetic anisotropy for patterned nanoparticle films fabricated by electric field-assisted deposition

    Science.gov (United States)

    Ou, Xiulong; He, Jun; Xia, Zhenjun; An, Jing; Hao, Jiazheng; He, Shuli; Zhao, Dongliang

    2017-08-01

    The patterned FeNi nanoparticle films with strip width 60 μm were prepared by electric field-assisted deposition technique. Application of electric field drove the accelerating deposition of the condensed nanoparticles, promoting the formation of the films with high stacking density. Besides the excellent soft magnetic characteristics, the samples showed an obvious enhancement of in-plane uniaxial magnetic anisotropy when they were annealed in vacuum environment at proper temperatures. The increase of in-plane uniaxial magnetic anisotropy, which is due to the release of stress with increasing temperature, is also confirmed by scanning microwave permeability spectra in GHz range. The experimental results imply that optimization of in-plane uniaxial magnetic anisotropy is particularly attractive for the application of electric field deposited soft magnetic nanoparticle films in the high-temperature processing electromagnetic devices.

  10. Cobalt-based magnetic nanostructures grown by focused-electron-beam-induced deposition

    Energy Technology Data Exchange (ETDEWEB)

    Begun, Evgeniya; Schwenk, Johannes; Porrati, Fabrizio; Huth, Michael [Physikalisches Institut, Goethe-Universitaet, D-60438 Frankfurt am Main (Germany)

    2011-07-01

    The fabrication of magnetic nanostructures by means of the direct-writing technique focused-electron-beam-induced deposition (FEBID) is an alternative to more conventional lithographic methods. We have grown magnetic cobalt structures by FEBID using the precursor dicobaltoctacarbonyl Co{sub 2}(CO){sub 8}. The obtained structures have a large metal content of about 85 at.% as compared to other metal-based deposits grown by the same technique, such as tungsten-based structures with 34 at.% maximum tungsten content and platin-based structures with about 24 at.% maximum platin content. We present a growth strategy for cobalt structures with tunable metal content. In particular, we show the influence of different combinations of electron-beam energy and current, the dwell time and the refresh time on the deposit composition, which was determined by energy-dispersive X-ray spectroscopy (EDX) at 5 keV. First results of magnetotransport measurements on these cobalt-based structures are presented.

  11. Growth-induced magnetic anisotropy and clustering in vapor-deposited Co-Pt alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, A.L.; Rooney, P.W.; Tran, M.Q.; Hellman, F. [Department of Physics, University of California--San Diego, La Jolla, California 92093 (United States); Ring, K.M.; Kavanagh, K.L. [Department of Electrical and Computer Engineering, University of California--San Diego, La Jolla, California 92093 (United States); Rellinghaus, B.; Weller, D. [IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States)

    1999-11-01

    Polycrystalline and epitaxial (100)-, (110)-, and (111)-oriented CoPt{sub 3} and Co{sub 0.35}Pt{sub 0.65} films were deposited at various growth rates and over a range of growth temperatures from {minus}50 to 800&hthinsp;{degree}C. Films grown at moderate temperatures (200{endash}400&hthinsp;{degree}C) exhibit remarkable growth-induced properties: perpendicular magnetic anisotropy and large coercivity, as well as enhanced Curie temperature and low-temperature saturation magnetization. Magnetic measurements indicate significant Co clustering in these epitaxial fcc films. These properties are independent of crystallographic orientation, increase with increasing growth temperature, and vanish with annealing. We propose that the correlation between magnetic inhomogeneity, magnetic anisotropy, and enhanced moment is explained by clustering of Co into thin platelets in a Pt-rich lattice. This clustering occurs at the growth surface and is trapped into the growing film by low bulk atomic mobility. {copyright} {ital 1999} {ital The American Physical Society}

  12. Energy Deposition in Magnetic Cloud and High Speed Stream Driven Storms

    Science.gov (United States)

    Mitchell, E. J.; Turner, N. E.

    2004-12-01

    The solar wind couples a large amount of energy into the magnetosphere-ionosphere system; this energy is released in the form of geomagnetic storms. While the precise mechanism for this coupling and release is yet unclear, it is well established that different solar wind conditions create different responses within the magnetosphere-ionosphere system. We are examining the impact of high speed stream-driven and magnetic cloud-driven storms on the global redistribution of energy throughout the magnetosphere-ionosphere system. Data are used from ACE, WIND, and ground magnetometers. We estimate the energy input and output for multiple geomagnetic storms spanning from1995 to 1998. The comparison of storms reveals high speed stream-driven storms deposit less energy per second, but over longer durations. The comparison further reveals magnetic cloud-driven storms have deeper Dst* depressions but with shorter durations. Our results suggest magnetic cloud-driven storms with similar input parameters as high speed stream-driven storms produce an overall lower energy deposition.

  13. Magnetic and magneto-optical properties of Co-P films prepared by chemical deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chzhan, A.V., E-mail: avchz@mail.ru [Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036 (Russian Federation); Siberian Federal University, Krasnoyarsk 660041 (Russian Federation); Patrin, G.S. [Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036 (Russian Federation); Siberian Federal University, Krasnoyarsk 660041 (Russian Federation); Kiparisov, S.Ya.; Seredkin, V.A.; Burkova, L.V.; Velikanov, D.A. [Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036 (Russian Federation)

    2011-10-15

    Features in the formation of chemically deposited polycrystalline Co-P films with thicknesses of a few nanometers are established by analyzing film surface morphology and variation in the film magnetization. It is shown that in the thickness range below 30 nm the polar Kerr effect value {theta}{sub K} changes nonmonotonically and depends on a wavelength of the incident light. For the films thicker than 30 nm, this value depends weakly on both the thickness and the wavelength. These features in the {theta}{sub K} behavior are attributed to the Faraday effect, which is revealed at small thicknesses upon light reflection from the lower surface of a magnetic layer. It is found that the Faraday effect in the Co-P films exceeds that in the Co films by a factor of more than two. This effect is assumed to be caused by the presence of a Pd underlayer in the samples under study. - Highlights: > Chemically deposited Co-P films are investigated. > Features of the polar Kerr effect in these films with thickness from 1 to 50 nm are considered. > It is shown that the Faraday rotation angle in the Co-P films exceeds that in the Co films by a factor of two. > Hysteresis loops and magnetization values are presented.

  14. Magnetic and noble metallic nanoparticles deposited on silica spheres via silanization.

    Science.gov (United States)

    Zhang, Feifei; Shi, Ruixia; Yang, Ping

    2014-07-01

    A sol-gel technique has been developed to deposit various nanoparticles (NPs) on silica spheres. The silanization of the silica spheres using 3-mercaptopropyltrimethoxysilane (MPS) with mercapto groups (-SH) plays an important role for the deposition. After being functionalized by MPS, the deposition of magnetic and noble metallic NPs was performed by the reduction of Au3+ and Ag+ ions in-situ using sodium borohydride (NaBH4) or the co-precipitation reaction of Fe2+/Fe3+ ions and ammonia (NH3 H2O) at low reactant concentrations at room temperature. The transmission electron microscope (TEM) observation of samples exhibited the homogeneous deposition of Ag, Au, and Fe3O4 NPs on the silica spheres, in which the average size of Au and Ag NPs is 5 nm in diameter while the ones of Fe3O4 NPs is about 10 nm. In the case of without the silanization of silica spheres, the nucleation and growth of the NPs in solutions occur instead of the homogenous deposition. The results demonstrates that MPS containing the -SH metal-chelating functionality, can grow a layer in an ethanol solution on the silica spheres, thus improving the performance of the silica surface by grafting -SH groups. These hybrids offer a high absorption capacity for metal ions, all kinds of NPs can be deposited on the surface by co-precipitation channel on the basis of such property. The results presented hear may open up a novel and simple approach for the preparation of composite NPs.

  15. Magnetic mineralogy of the Hongqiling Cu-Ni sulphide deposit:Implications for ore genesis

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Pyrrhotite is one of the common ore minerals in Cu-Ni sulphide deposits, but only monoclinic pyrrhotite is ferromagnetic at room temperature. X-ray and EPA analyses reveal that most pyrrhotite forming sideronitic texture in the Hongqiling Cu-Ni sulphide deposit is monoclinic, but that in the massive ore is a mixture of monoclinic and hexagonal pyrrhotites. Differential thermal and magneticthermogravimetric analyses of massive ore indicate a magnetic transition and heat absorption at 323℃, suggesting that this temperature is the thermomagnetic and phase transition point of pyrrhotite. For massive pyrrhotite ores heated at 400℃ for 30 h and then quenched by cool water, the monoclinic pyrrhotite (mpo) transforms completely into the hexagonal pyrrhotite (hpo). However, all the pyrrhotites resulting from slow cooling of the sample in air are mpo. These results indicate that transformation between hpo and mpo depends upon the cooling rate. Therefore, massive ores in this deposit might have been formed via rapid cooling of ore melts. On the other hand, it is significant to study the effect of the ratio of the magnetite in total ores on the genesis of magmatic Cu-Ni suphide deposits.

  16. Preliminary magnetostratigraphy and environmental magnetism of the Lower Cretaceous from the Italian Dolomites

    Science.gov (United States)

    Savian, J. F.; Jovane, L.; Florindo, F.; Lukeneder, A.

    2011-12-01

    The Lower Cretaceous (~146 to 100 Ma) represents an enigmatic time interval for paleoclimatic, paleogeography and paleomagnetic evolution of the Earth's history. The climatic changes include global oceanic anoxic events (OAEs), biotic changes, global excursions of carbon and strontium isotopes, rises in eustatic sea level and paleotemperature. Paleoceanography was marked by a rapid rate of ocean spreading in the Atlantic. The opening of the Atlantic Ocean was wide enough to allow significant circulation of masses of waters across the equator. This period is furthermore important for the oceanographic events occurring at the base of the Aptian (Selli Level). This period also present one of the most intriguing geomagnetic events: the long normal Cretaceous superchron, lasted for almost 40 million years. We study here the lower Cretaceous deposits of the Puez section in the Dolomites (northern Italy) which represents a continuous section during this period. The samples collected represent marine sedimentary materials of the Biancone and Puez formations. The Puez section consists essentially of green-grey to red limestones and calcareous marls. We present preliminary results of integrated magnetostratigraphic analysis, including a detailed lithostratigraphy and environmental magnetism. We recognize magnetic behavior that are relative to normal polarity (the normal Cretaceous superchron), with a short reverse interval that might represent the M-1r event. We also recognize a series of normal and reverse polarities (below the normal Cretaceous superchron) which can be referred to the magnetozones M1/M5. The environmental magnetic data consists of magnetic susceptibility (χ), natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) at 900 mT and backfield isothermal remanent magnetization (BIRM) at 100 mT and 300 mT. Derived parameters, such as S-ratio (S300=BIRM300/IRM900) and hard isothermal remanent

  17. PULSED LASER DEPOSITION OF MAGNETIC MULTILAYERS FOR THE GRANT ENTITLED LASER PROCESSING OF ADVANCED MAGNETIC MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    Monica Sorescu

    2003-10-11

    Nanostructured magnetite/T multilayers, with T = Ni, Co, Cr, have been prepared by pulsed laser deposition. The thickness of individual magnetite and metal layers takes values in the range of 5-40 nm with a total multilayer thickness of 100-120 nm. X-ray diffraction has been used to study the phase characteristics as a function of thermal treatment up to 550 C. Small amounts of maghemite and hematite were identified together with prevailing magnetite phase after treatments at different temperatures. The mean grain size of magnetite phase increases with temperature from 12 nm at room temperature to 54 nm at 550 C. The thermal behavior of magnetite in multilayers in comparison with powder magnetite is discussed. These findings were published in peer-reviewed conference proceedings after presentation at an international materials conference.

  18. Atomic layer deposition of cobalt carbide films and their magnetic properties using propanol as a reducing agent

    Energy Technology Data Exchange (ETDEWEB)

    Sarr, Mouhamadou, E-mail: sarrtapha44@yahoo.fr [Luxembourg Instituteof Science and Technology, 41, rue du Brill, L-4422 Belvaux (Luxembourg); Bahlawane, Naoufal; Arl, Didier [Luxembourg Instituteof Science and Technology, 41, rue du Brill, L-4422 Belvaux (Luxembourg); Dossot, Manuel [Laboratory of Physical Chemistry and Microbiology for the Environment, UMR 7564 CNRS-Université de Lorraine, 405 rue de Vandoeuvre, 54601 Villers-lès-Nancy (France); McRae, Edward [Institut Jean Lamour, UMR 7198CNRS-Université de Lorraine, FST, BP 70239, 54506 Vandoeuvre-lès-Nancy (France); Lenoble, Damien, E-mail: damien.lenoble@list.lu [Luxembourg Instituteof Science and Technology, 41, rue du Brill, L-4422 Belvaux (Luxembourg)

    2016-08-30

    Highlights: • Conformal carbon-Co-carbide thin films. • Chemically growth carbone-Co-carbide composite. • Tuneable magnetic properties. - Abstract: The investigation of highly conformal thin films using Atomic Layer Deposition (ALD) is driven by a variety of applications in modern technologies. In particular, the emergence of 3D memory device architectures requires conformal materials with tuneable magnetic properties. Here, nanocomposites of carbon, cobalt and cobalt carbide are deposited by ALD using cobalt acetylacetonate with propanol as a reducing agent. Films were grown by varying the ALD deposition parameters including deposition temperature and propanol exposure time. The morphology, the chemical composition and the crystalline structure of the cobalt carbide film were investigated. Vibrating Sample Magnetometer (VSM) measurements revealed magnetic hysteresis loops with a coercivity reaching 500 Oe and a maximal saturation magnetization of 0.9 T with a grain size less than 15 nm. Magnetic properties are shown to be tuneable by adjusting the deposition parameters that significantly affect the microstructure and the composition of the deposited films.

  19. Temperature-dependent magnetic properties of Ni nanotubes synthesized by atomic layer deposition

    Science.gov (United States)

    Pereira, Alejandro; Palma, Juan L.; Denardin, Juliano C.; Escrig, Juan

    2016-08-01

    Highly-ordered and conformal Ni nanotube arrays were prepared by combining atomic layer deposition (ALD) in a porous alumina matrix with a subsequent thermal reduction process. In order to obtain NiO tubes, one ALD NiCp2/O3 cycle was repeated 2000 times. After the ALD process, the sample is reduced from NiO to metallic Ni under hydrogen atmosphere. Their magnetic properties such as coercivity and squareness have been determined in a vibrating sample magnetometer in the temperature range from 5-300 K for applied magnetic fields parallel and perpendicular to the nanotube axis. Ni nanotubes synthesized by ALD provide a promising opportunity for potential applications in spintronics, data storage and bio-applications.

  20. Effect of the interplanetary magnetic field orientation and intensity in the mass and energy deposition on the Hermean surface

    CERN Document Server

    Varela, J; Moncuquet, M

    2016-01-01

    The aim of the present study is to simulate the interaction between the solar wind and the Hermean magnetosphere. We use the MHD code PLUTO in spherical coordinates with an axisymmetric multipolar expansion of the Hermean magnetic field, to perform a set of simulations with different interplanetary magnetic field orientations and intensities. We fix the hydrodynamic parameters of the solar wind to study the distortions driven by the interplanetary magnetic field in the topology of the Hermean magnetosphere, leading to variations of the mass and energy deposition distributions, the integrated mass deposition, the oval aperture, the area covered by open magnetic field lines and the regions of efficient particle sputtering on the planet surface. The simulations show a correlation between the reconnection regions and the local maxima of plasma inflow and energy deposition on the planet surface.

  1. Effect of adatom deposition on surface magnetism and exchange coupling parameter in (0001) SmCo{sub 5} slabs

    Energy Technology Data Exchange (ETDEWEB)

    Selva Chandrasekaran, S.; Murugan, P., E-mail: murugan@cecri.res.in [CSIR Central Electrochemical Research Institute, Karaikudi 630 003 (India); Saravanan, P.; Kamat, S. V. [Defence Metallurgical Research Laboratory, Hyderabad 500 058 (India)

    2015-04-07

    First principles calculations are performed on 3d-transition metal atom deposited (0001) surface of SmCo{sub 5} to understand the magnetic properties and the improvement of Curie temperature (T{sub c}). Various atomic sites are examined to identify the energetically feasible adsorption of adatom and it is found that the void site of Co-rich (0001) SmCo{sub 5} surface is the most favourable one to deposit. The surface magnetic moments of various adatom deposited SmCo{sub 5} surfaces are larger than the clean surface except for Cu and Zn. Eventually, the surface exchange coupling of clean and adatom deposited surface is found to increase for Mn, Fe, Co, Ni, and Cu deposited surfaces and this improvement results in the increase in T{sub c} of SmCo{sub 5} slab.

  2. Nanostructure and magnetic properties of magnesium ferrite thin films deposited on glass substrate by spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Arabi, H., E-mail: arabi-h@um.ac.ir [Magnetism and Superconducting Research Laboratory, Department of Physics, Faculty of Science, University of Birjand, Birjand (Iran, Islamic Republic of); Department of Physics, Faculty of Science, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Khalili Moghadam, N. [Magnetism and Superconducting Research Laboratory, Department of Physics, Faculty of Science, University of Birjand, Birjand (Iran, Islamic Republic of)

    2013-06-15

    The spinel MgFe{sub 2}O{sub 4} thin films were prepared on the glass substrates at T{sub S}=400 °C by the spray pyrolysis deposition method. Structural and magnetic properties of the calcinated thin films at different temperatures were also investigated. By changing the calcination temperature from 400 to 600 °C, the crystallite size increased from 10 to 15 nm and the crystallinity of the films improved slightly. Thickness of the films calcinated at 400 and 600 °C were 0.648 and 1.473 μm respectively. However, the surface morphology of the films did not change considerably. Magnetic measurements, when the applied magnetic field was in parallel and perpendicular directions, showed the isotropic magnetic nature of the prepared films and their magnetic properties increased with the increment of calcination temperature. The H{sub c} value of thin films calcinated at 400 °C was about 168 Oe. - Highlights: ► Thin films of MgFe{sub 2}O{sub 4} are prepared via spray pyrolysis. ► All of the MgFe{sub 2}O{sub 4} films have nanostructure and the special magnetic properties. ► The surface morphology of films in different calcination temperatures is similar. ► The H{sub c} values of our films are independent of the applied field direction. ► The M{sub s} values in the plan and perpendicular directions are not the same.

  3. Microbially assisted recording of the Earth's magnetic field in sediment.

    Science.gov (United States)

    Zhao, Xiangyu; Egli, Ramon; Gilder, Stuart A; Müller, Sebastian

    2016-02-11

    Sediments continuously record variations of the Earth's magnetic field and thus provide an important archive for studying the geodynamo. The recording process occurs as magnetic grains partially align with the geomagnetic field during and after sediment deposition, generating a depositional remanent magnetization (DRM) or post-DRM (PDRM). (P)DRM acquisition mechanisms have been investigated for over 50 years, yet many aspects remain unclear. A key issue concerns the controversial role of bioturbation, that is, the mechanical disturbance of sediment by benthic organisms, during PDRM acquisition. A recent theory on bioturbation-driven PDRM appears to solve many inconsistencies between laboratory experiments and palaeomagnetic records, yet it lacks experimental proof. Here we fill this gap by documenting the important role of bioturbation-induced rotational diffusion for (P)DRM acquisition, including the control exerted on the recorded inclination and intensity, as determined by the equilibrium between aligning and perturbing torques acting on magnetic particles.

  4. Electroless deposition of Ni on template of halloysite and its magnetic property

    Institute of Scientific and Technical Information of China (English)

    FU Yu-bin; ZHANG Li-de; ZHENG Ji-yong

    2004-01-01

    Halloysite template, a ceramic substrate, is of a hollow cylindric structure, on which the fine Pd nanoparticles are uniformly formed by the reduction of palldate chloride to initiate electroless deposition. The electroless deposition of Ni is catalyzed by the Pd particles, which results in a uniform layer of Ni-P alloy on halloysite. The alloy is of a nanocrystalline structure, of which the average diameter is about 6 nm. After being heat-treated at 400 ℃, it contains both Ni and Ni12P5 crystal, meanwhile, the Ni crystal gets larger with an average size of 51.9 nm.The content of phosphorous in the Ni layer has a great influence on crystal structure. The metallized halloysite has a higher inherent coercive force, and a much lower saturation magnetization in its as-plated state, while after heattreatment, the inherent coercive force decreases drastically. These magnetic properties have great relationship with the superparamagnetism of Ni nanocrystalline and the stress anisotropy in Ni layer.

  5. Geology, Geochemistry and Ground Magnetic Survey on Kalateh Naser Iron Ore Deposit, Khorasan Jonoubi Province

    Directory of Open Access Journals (Sweden)

    Saeed Saadat

    2017-02-01

    Full Text Available Introduction Ground magnetometer surveys is one of the oldest geophysical exploration methods used in identifying iron reserves. The correct interpretation of ground magnetic surveys, along with geological and geochemical data will not only reduce costs but also to indicate the location, depth and dimensions of the hidden reserves of iron (Robinson and Coruh, 2005; Calagari, 1992. Kalateh Naser prospecting area is located at 33° 19َ to 33° 19ََ 42" latitude and 60° 0' to 60° 9َ 35" longitude in the western side of the central Ahangaran mountain range, eastern Iran (Fig.1. Based on primary field evidences, limited outcrops of magnetite mineralization were observed and upon conducting ground magnetic survey, evidence for large Iron ore deposits were detected (Saadat, 2014. This paper presents the geological and geochemical studies and the results of magnetic measurements in the area of interest and its applicability in exploration of other potential Iron deposits in the neighboring areas. Materials and methods To better understand the geological units of the area, samples were taken and thin sections were studied. Geochemical studies were conducted through XRF and ICP-Ms and wet chemistry analysis. The ground magnetic survey was designed to take measurements from grids of 20 meter apart lines and 10 meter apart points along the north-south trend. 2000 points were measured during a 6-day field work by expert geophysicists. Records were made by Canadian manufactured product Magnetometer Proton GSM19T (Fig. 2. Properties of Proton Magnetometer using in magnetic survey in Kalateh Naser prospecting area is shown in Table 1. Total magnetic intensity map, reduced to pole magnetic map, analytic single map, first vertical derivative map and upward continuation map have been prepared for this area. Results The most significant rock units in the area are cretaceous carbonate rocks (Fig. 3. The unit turns to shale and thin bedded limestone in the

  6. Stress analysis, structure and magnetic properties of sputter deposited Ni-Mn-Ga ferromagnetic shape memory thin films

    Science.gov (United States)

    Annadurai, A.; Manivel Raja, M.; Prabahar, K.; Kumar, Atul; Kannan, M. D.; Jayakumar, S.

    2011-11-01

    The residual stress instituted in Ni-Mn-Ga thin films during deposition is a key parameter influencing their shape memory applications by affecting its structural and magnetic properties. A series of Ni-Mn-Ga thin films were prepared by dc magnetron sputtering on Si(1 0 0) and glass substrates at four different sputtering powers of 25, 45, 75 and 100 W for systematic investigation of the residual stress and its effect on structure and magnetic properties. The residual stresses in thin films were characterized by a laser scanning technique. The as-deposited films were annealed at 600 °C for 1 h in vacuum for structural and magnetic ordering. The compressive stresses observed in as-deposited films transformed into tensile stresses upon annealing. The annealed films were found to be crystalline and possess mixed phases of both austenite and martensite, exhibiting good soft magnetic properties. It was found that the increase of sputtering power induced coarsening in thin films. Typical saturation magnetization and coercivity values were found to be 330 emu/cm 3 and 215 Oe, respectively. The films deposited at 75 and 100 W display both structural and magnetic transitions above room temperature.

  7. Power Deposition in LHC Magnets Due to Bound-Free Pair Production in the Experimental Insertions

    CERN Document Server

    Bahamonde Castro, Cristina; Besana, Maria Ilaria; Brodzinski, Krzysztof; Bruce, Roderik; Cerutti, Francesco; Jowett, John; Lechner, Anton; Mertens, Tom; Parma, Vittorio; Redaelli, Stefano; Schaumann, Michaela; Shetty, Nikhil Vittal; Skordis, Eleftherios; Steele, Genevieve; van Weelderen, Rob

    2016-01-01

    The peak luminosity achieved during Pb-Pb collisions in the LHC in 2015 (3x1027cm⁻²s^{−1}) well exceeded the design luminosity and is anticipated to increase by another factor 2 after the next Long Shutdown (2019- 2020). A significant fraction of the power dissipated in ultra-peripheral Pb-Pb collisions is carried by ions from bound-free pair production, which are lost in the dispersion suppressors adjacent to the experimental insertions. At higher luminosities, these ions risk to quench superconducting magnets and might limit their operation due to the dynamic heat load that needs to be evacuated by the cryogenic system. In this paper, we estimate the power deposition in superconducting coils and the magnet cold mass and we quantify the achievable reduction by deviating losses to less sensitive locations or by installing collimators at strategic positions. The second option is considered for the dispersion suppressor next to the ALICE insertion, where a selective displacement of losses to a magnet-free ...

  8. How to obtain a magnetic hard-soft architecture by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Fix, T; Trassin, M; Hassan, R Sayed; Schmerber, G; Viart, N; Meny, C; Colis, S; Dinia, A [Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), Unite Mixte de Recherche 7504 du Centre National de la Recherche Scientifique (CNRS), Universite Louis Pasteur-Ecole Europeenne de Chimie, Polymeres et Materiaux de Strasbourg - ULP-ECPM, 23 rue du Loess, BP43 F-67034 Strasbourg (France)

    2007-12-12

    In spin valve type systems, one ferromagnetic electrode must be magnetically hard to act as a reference layer while the other electrode must be magnetically soft to act as a sensor or storage layer. This magnetic hard-soft architecture can usually be obtained by four different methods: the use of two ferromagnets with different coercive fields (here CoFe{sub 2} and Ni{sub 80}Fe{sub 20}), the use of an underlayer enhancing the coercive field of one of the two ferromagnets (here Ta and Ru), the use of a ferromagnet coupled to a ferrimagnet or antiferromagnet (here NiO/CoFe{sub 2} and CoFe{sub 2}O{sub 4}/CoFe{sub 2}), or the use of an artificial antiferromagnet (here CoFe{sub 2}/Ru/CoFe{sub 2}). We show that at least the first and the third methods seem to work with pulsed laser deposition in the thermodynamic conditions used.

  9. Structural and magnetic properties of pulsed laser deposited Fe–SiC thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mukesh [Nanoscience Laboratory, Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee, UK 247 667 (India); Chandra, Ramesh, E-mail: ramesfic@iitr.ac.in [Nanoscience Laboratory, Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee, UK 247 667 (India); Goyat, Manjeet S. [University of Petroleum & Energy Studies, Dehradun, Uttarakhand 248007 (India); Mishra, Raghwesh; Tiwari, Rajesh K.; Saxena, A.K. [Applied Chemistry Division, Defence Materials & Stores Research & Development Establishment (DMSRDE), GT Road, Kanpur, UP 208013 (India)

    2015-03-31

    Structural and magnetic properties of Fe–SiC thin films have been studied. The Fe–SiC thin films were fabricated by pulsed laser deposition on Si (100) substrate and isochronally annealed at 1073 K and 1273 K in argon atmosphere for 2.5 h. The crystalline ordering of SiC into β-SiC phase and growths of other phases like Fe{sub 3}Si, SiO{sub 2} and FeSiO{sub 3} during annealing were investigated by X-ray diffraction and X-ray photoelectron spectroscopy measurements. The morphology of thin films was changed from voided structure to dense pyramidal-like structure due to annealing. A continuous decrease in the saturation magnetization and non-monotonic change in coercivity of Fe–SiC thin films were observed with increase in annealing temperature. - Highlights: • Structural and magnetic properties of Fe–SiC thin films have been studied. • Crystalline ordering of SiC into β-SiC phase was obtained at T ≥ 800 °C. • Annealed Fe–SiC thin films show ferromagnetic hysteresis at room temperature. • Coercivity was found to be dependent on the annealing temperature.

  10. The effects of a magnetic field on the morphologies of nickel and copper deposits: the concept of “effective overpotential”

    Directory of Open Access Journals (Sweden)

    NEBOJSA D. NIKOLIC

    2007-08-01

    Full Text Available The morphologies of nickel and copper deposits obtained without applied magnetic fields, and with both parallel and perpendicular applied magnetic fields were examined by the scanning electron microscopy (SEM technique. Changes in the morphologies of the metals caused by the effect of the magnetic fields are explained by the concept of “effective overpotential”. The morphologies of the nickel and copper deposits obtained under parallelly oriented magnetic fields were similar to those obtained at some lower cathodic potentials without an applied magnetic field. The magnetic field with a perpendicular orientation to the electrode surface increased the dispersity of the nickel and copper deposits. Nickel and copper deposits obtained under this orientation of the magnetic field were similar to those obtained at some higher cathodic potentials without an applied magnetic field.

  11. Modelling of isothermal remanence magnetisation curves for an assembly of macrospins

    Energy Technology Data Exchange (ETDEWEB)

    Tournus, F., E-mail: florent.tournus@univ-lyon1.fr

    2015-02-01

    We present a robust and efficient framework to compute isothermal remanent magnetisation (IRM) curves for magnetic nanoparticle assemblies. The assembly is modelled by independent, randomly oriented, uniaxial macrospins and we use a Néel model to take into account the thermal relaxation. A simple analytic expression is established for a single size, in a sudden switching approximation, and is compared to more evolved models. We show that for realistic samples (necessarily presenting a size dispersion) the simple model is very satisfactory. With this framework, it is then possible to reliably simulate IRM curves, which can be compared to experimental measurements and used in a best fit procedure. We also examine the influence of several parameters on the IRM curves and we discuss the link between the irreversible susceptibility and the switching field distribution. - Highlights: • A framework to compute IRM curves for nanoparticle assemblies is presented. • A simple analytic expression (for a single size) is compared to more evolved models. • The simple expression can reliably simulate IRM curves for realistic samples. • Irreversible susceptibility and the influence of several parameters is discussed.

  12. Brain iron deposition in essential tremor: a quantitative 3-Tesla magnetic resonance imaging study.

    Science.gov (United States)

    Novellino, Fabiana; Cherubini, Andrea; Chiriaco, Carmelina; Morelli, Maurizio; Salsone, Maria; Arabia, Gennarina; Quattrone, Aldo

    2013-02-01

    Studies have demonstrated brain iron deposition in neurodegenerative disease and in normal aging. Data on this topic are lacking in essential tremor (ET). The aim of our study was to investigate brain iron content in patients with ET, using quantitative magnetic resonance imaging (MRI) T2*-relaxometry. We enrolled 24 patients with ET and 25 age-matched healthy controls. Subjects were examined using a 3T MRI scanner. The protocol included conventional MRI sequences and quantitative T2*-relaxometry. Whole-brain voxel-based analyses showed significant differences in T2* values in bilateral globus pallidus, substantia nigra, and in right dentate nucleus (P motor systems outside of the cerebellum/cerebellar pathway and, more specifically, of the globus pallidus. Copyright © 2012 Movement Disorders Society.

  13. Structural and Electrical Properties of Heteroepitaxial Magnetic Oxide Junction Diode Fabricated by Pulsed Laser Deposition

    Science.gov (United States)

    Li, M. K.; Wong, K. H.

    2010-11-01

    Heteroepitaxial junctions formed by p-type strontium doped lanthanum manganite and n-type cobalt doped titanium dioxide were fabricated on LaAlO3 (100) substrates by pulsed laser deposition. The La0.7Sr0.3MnO3 (LSMO) layers were grown at 650° C and under 150 mTorr ambient oxygen pressure. They showed room temperature ferromagnetism and metallic-like electrical conduction with a resistivity of 0.015 ohm cm at 300 K. The CoxTi1-xO2[x = 0.05 and 0.1] (CTO), which, at anatase phase, was reported as a wide-band-gap dilute magnetic semiconductor, was deposited on the LSMO film surface at 600° C with an ambient oxygen pressure of 20 mTorr. The as-grown CTO films exhibited pure anatase crystalline phase and semiconductor-like conduction. Under optimized fabrication conditions the CTO/LSMO junction revealed a heteroepitaxial relationship of (004)CTO‖‖(001)LSMO‖‖(001)LAO. Electrical characterization of these p-n junctions yielded excellent rectifying characteristics with a current rectifying ratio over 1000 at room temperature. The electrical transport across these diodes was dominated by diffusion current at low current (low bias voltage) regime and by recombination current at high current (high bias voltage) regime. Our results have demonstrated an all-oxide spintronic junction diode with good transport property. The simultaneous of electrical and magnetic modulation in a diode junction is therefore potentially realizable.

  14. Tunable finite-sized chains to control magnetic relaxation

    Science.gov (United States)

    Ekstrand, Paul D.; Javier, Daniel J.; Gredig, Thomas

    2017-01-01

    The magnetic dynamics of low-dimensional iron ion chains have been studied with regards to the tunable finite-sized chain length using iron phthalocyanine thin films. The deposition temperature varies the diffusion length during thin-film growth by limiting the average crystal size in the range from 40 to 110 nm . Using a method common for single chain magnets, the magnetic relaxation time for each chain length is determined from temporal remanence data and fit to a stretched exponential form in the temperature range below 5 K , the onset for magnetic hysteresis. A temperature-independent master curve is generated by scaling the remanence by its relaxation time to fit the energy barrier for spin reversal, and the single spin-relaxation time. The energy barrier of 95 K is found to be independent of the chain length. In contrast, the single spin-relaxation time increases with longer chains from under 1 ps to 800 ps. We show that thin films provide the nanoarchitecture to control magnetic relaxation and a testbed to study finite-size effects in low-dimensional magnetic systems.

  15. Magnetic petrofabric of igneous rocks: Lessons from pyroclastic density current deposits and obsidians

    Science.gov (United States)

    Cañón-Tapia, E.; Mendoza-Borunda, R.

    2014-12-01

    Measurement of the anisotropy of magnetic susceptibility (AMS) of igneous rocks can provide clues concerning their mechanism of formation and in particular are very helpful as flow direction indicators. Unlike other igneous rocks, however, pyroclastic density current deposits (PDCDs) present a challenge in the interpretation of AMS measurements due to the complexity of their mechanism of emplacement. In this paper we review the most common assumptions made in the interpretation of the AMS of PDCD, taking advantage of key lessons obtained from obsidians. Despite the complexities on the mechanism of formation of PDCDs, it is shown that a key element for the fruitful interpretation of AMS is to give proper attention to the various components likely to be involved in controlling their general petrofabric. The anisotropies of ferromagnetic crystals (whether as free phases or embedded within clasts or shards), and those of paramagnetic minerals (mainly ferrosilicates) need to be taken into consideration when interpreting the AMS measurements of PDCDs. Variations of the deposition regime both as a function of position and of time also need to be considered on the interpretations. Nevertheless, if a suitable sampling strategy is adopted, the potential of the AMS method as a petrofabric indicator is maximized.

  16. Enhanced detection of gametocytes by magnetic deposition microscopy predicts higher potential for Plasmodium falciparum transmission

    Directory of Open Access Journals (Sweden)

    Zborowski Maciej

    2008-04-01

    Full Text Available Abstract Background Aggregated haemozoin crystals within malaria-infected erythrocytes confer susceptibility of parasitized cells to a magnetic field. Here the utility of this method for diagnosis of human malaria is evaluated in a malaria-endemic region of Papua New Guinea (PNG. Methods and findings Individuals with Plasmodium falciparum malaria symptoms (n = 55 provided samples for conventional blood smear (CBS and magnetic deposition microscopy (MDM diagnosis. Standard Giemsa staining and light microscopy was performed to evaluate all preparations. Plasmodium falciparum parasitaemia observed on MDM slides was consistently higher than parasitaemia observed by (CBS for ring (CBS = 2.6 vs. MDM = 3.4%; t-test P-value = 0.13, trophozoite (CBS = 0.5 vs. MDM = 1.6%; t-test P-value = 0.01, schizont (CBS = 0.003 vs. MDM = 0.1%; t-test P-value = 0.08 and gametocyte (CBS = 0.001 vs. MDM = 0.4%; t-test P-value = 0.0002 parasitaemias. Gametocyte prevalence determined by CBS compared to MDM increased from 7.3% to 45%, respectively. Conclusion MDM increased detection sensitivity of P. falciparum-infected, haemozoin-containing erythrocytes from infected humans while maintaining detection of ring-stage parasites. Gametocyte prevalence five-fold higher than observed by CBS suggests higher malaria transmission potential in PNG endemic sites compared to previous estimates.

  17. 3D Geological Model of Nihe ore deposit Constrained by Gravity and Magnetic Modeling

    Science.gov (United States)

    Qi, Guang; Yan, Jiayong; Lv, Qingtan; Zhao, Jinhua

    2016-04-01

    We present a case study on using integrated geologic model in mineral exploration at depth. Nihe ore deposit in Anhui Province, is deep hidden ore deposit which was discovered in recent years, this finding is the major driving force of deep mineral exploration work in Luzong. Building 3D elaborate geological model has the important significance for prospecting to deep or surround in this area, and can help us better understand the metallogenic law and ore-controlling regularity. A 3D geological model, extending a depth from +200m to -1500m in Nihe ore deposit, has been compiled from surface geological map, cross-section, borehole logs and amounts of geological inference. And then the 3D geological models have been given physical property parameter for calculating the potential field. Modelling the potential response is proposed as means of evaluating the viability of the 3D geological models, and the evidence of making small changes to the uncertain parts of the original 3D geological models. It is expected that the final models not only reproduce supplied prior geological knowledge, but also explain the observed geophysical data. The workflow used to develop the 3D geologic model in this study includes the three major steps, as follows: (1) Determine the basic information of Model: Defining the 3D limits of the model area, the basic geological and structural unit, and the tectonic contact relations and the sedimentary sequences between these units. (2) 3D model construction: Firstly, a series of 2D geological cross sections over the model area are built by using all kinds of prior information, including surface geology, borehole data, seismic sections, and local geologists' knowledge and intuition. Lastly, we put these sections into a 3D environment according to their profile locations to build a 3D model by using geostatistics method. (3) 3D gravity and magnetic modeling: we calculate the potential field responses of the 3D model, and compare the predicted and

  18. Short and Long Term Environmental Trends Observed in the Magnetism of Cave Deposits

    Science.gov (United States)

    Feinberg, Joshua

    2016-04-01

    Caves are deep time archives of environmental conditions at the surface. Traditional paleoclimate proxies, such as oxygen and carbon isotopic ratios, are preserved within actively growing carbonate speleothems and can be constrained in time using high-resolution 230Th geochronology. While these isotopic speleothem proxies have revolutionized paleoclimate studies, here we discuss a promising new development in speleothem studies: the use of magnetic measurements to constrain changes in the flux of Fe-bearing minerals (their composition, concentration, and magnetic grain size distribution) within the context of environmental change. Fe-bearing minerals can occur within speleothems due to a variety of transportation and nucleation & growth mechanisms. Drip waters carry trace concentrations of Fe-bearing minerals from overlying soils and dissolved and eroded bedrock. Flood waters that temporarily fill a cave passage will leave behind thin films of silt- and clay-sized sediment, some of which contain Fe-bearing minerals. Some minerals, such as goethite, are thought to nucleate and grow in pore spaces in the overlying rock and can become deposited via dripwater onto actively growing stalagmites. Alternatively, changes in the Eh and pH conditions of groundwater as it equilibrates with the open air environment of a cave may cause dissolved Fe to nucleate and grow goethite directly on the surface of carbonate speleothems. Thus, while the incorporation of Fe-bearing minerals into speleothems is primarily a function of surface environmental conditions, including precipitation patterns, mean annual temperature, and pedogenic productivity, secondary processes within a cave environment can also contribute to Fe-minerals in speleothems. Here we present some promising examples of how the magnetic properties of Fe-bearing minerals preserved within speleothems can provide environmental information on short (e.g., decadal) and long (e.g., millennial) timescales that is independent

  19. Magnetic volcanos in gadolinium Langmuir-Blodgett films

    DEFF Research Database (Denmark)

    Tishin, A.M.; Snigirev, O.V.; Khomutov, G.B.

    2001-01-01

    -plane and out-of-plane pre-magnetization in a field of 1.4 T at 300 K. Randomly placed “magnetic volcanos” with a remanent magnetic moment of the order of 10−13 A m2 was observed. A decay of the remanent magnetization with a characteristic time of about 120 h was observed. It is suggested that the magnetic...

  20. Effect of Cu buffer layer on magnetic anisotropy of cobalt thin films deposited on MgO(001 substrate

    Directory of Open Access Journals (Sweden)

    Syed Sheraz Ahmad

    2016-11-01

    Full Text Available Cobalt thin films with 5 nm thickness were prepared on single-crystal MgO (001 substrates with different thickness Cu buffer (0 nm, 5 nm, 10 nm, 20 nm. The structure, magnetic properties and transport behaviors were investigated by employing low-energy-electron-diffraction (LEED, magneto-optical Kerr effect (MOKE and anisotropic magnetoresistance (AMR. By comparing the magnetic properties of the sample as-deposited (without Cu buffer layer one with those having the buffer Cu, we found that the magnetic anisotropy was extremely affected by the Cu buffer layer. The magnetic anisotropy of the as-deposited, without buffer layer, sample shows the uniaxial magnetic anisotropy (UMA. We found that the symmetry of the magnetic anisotropy is changed from UMA to four-fold when the thickness of the Cu buffer layer reaches to 20 nm. Meanwhile, the coercivity increased from 49 Oe (without buffer layer to 300 Oe (with 20 nm Cu buffer, in the easy axis direction, as the thickness of the buffer layer increases. Moreover, the magnitudes of various magnetic anisotropy constants were determined from torque curves on the basis of AMR results. These results support the phenomenon shown in the MOKE.

  1. Effect of Cu buffer layer on magnetic anisotropy of cobalt thin films deposited on MgO(001) substrate

    Science.gov (United States)

    Ahmad, Syed Sheraz; He, Wei; Zhang, Yong-Sheng; Tang, Jin; Gul, Qeemat; Zhang, Xiang-Qun; Cheng, Zhao-Hua

    2016-11-01

    Cobalt thin films with 5 nm thickness were prepared on single-crystal MgO (001) substrates with different thickness Cu buffer (0 nm, 5 nm, 10 nm, 20 nm). The structure, magnetic properties and transport behaviors were investigated by employing low-energy-electron-diffraction (LEED), magneto-optical Kerr effect (MOKE) and anisotropic magnetoresistance (AMR). By comparing the magnetic properties of the sample as-deposited (without Cu buffer layer) one with those having the buffer Cu, we found that the magnetic anisotropy was extremely affected by the Cu buffer layer. The magnetic anisotropy of the as-deposited, without buffer layer, sample shows the uniaxial magnetic anisotropy (UMA). We found that the symmetry of the magnetic anisotropy is changed from UMA to four-fold when the thickness of the Cu buffer layer reaches to 20 nm. Meanwhile, the coercivity increased from 49 Oe (without buffer layer) to 300 Oe (with 20 nm Cu buffer), in the easy axis direction, as the thickness of the buffer layer increases. Moreover, the magnitudes of various magnetic anisotropy constants were determined from torque curves on the basis of AMR results. These results support the phenomenon shown in the MOKE.

  2. Magnetic interactions in exchange-coupled yet unbiased IrMn/NiCu bilayers

    Science.gov (United States)

    Cichelero, R.; Harres, A.; Sossmeier, K. D.; Schmidt, J. E.; Geshev, J.

    2013-10-01

    This paper reports experimental and model magnetization results obtained on exchange-coupled ferromagnet/antiferromagnet (FM/AF) bilayers that show zero net bias. The coercivity of the films, either irradiated with He or implanted with Ge ions at 40 keV, varies significantly with the fluence used. We employed the remanence plots technique in order to estimate the nature of the interactions present and check if there exists a correlation between their type and the coercivity variations. The analysis of the remanence plots through numerical simulations based on the Landau-Lifshitz-Gilbert equation demonstrated that outcomes of interactions within the FM layer could be distinguished from those coming from coupling at the FM/AF interface and that demagnetizing interaction effects could be achieved without the presence of dipolar interactions. Our findings indicate that such experiments could give selective information on modifications caused by a post-deposition treatment in each layer of the film.

  3. Magnetic fabric, welding texture and strain fabric in the Nuraxi Tuff, Sardinia, Italy

    Science.gov (United States)

    Pioli, L.; Lanza, R.; Ort, M.; Rosi, M.

    2008-09-01

    Anisotropy of magnetic susceptibility (AMS) has been used to interpret flow directions in ignimbrites, but no study has demonstrated that the AMS fabric corresponds to the flow fabric. In this paper, we show that the AMS and strain fabric coincide in a high-grade ignimbrite, the Nuraxi Tuff, a Miocene rhyolitic ignimbrite displaying a wide variability of rheomorphic features and a well-defined magnetic fabric. Natural remanent magnetization (NRM) data indicate that the magnetization of the tuff is homogeneous and was acquired at high temperatures by Ti-magnetite crystals. Comparison between the magnetic fabric and the deformation features along a representative section shows that AMS and anisotropy of isothermal remanent magnetization (AIRM) fabric are coaxial with and reproduce the shape of the strain ellipsoid. Magnetic tests and scanning electron microscopy observations indicate that the fabric is due to trails of micrometer-size, pseudo-single domain, magnetically interacting magnetite crystals. Microlites formed along discontinuities such as shard rims and vesicle walls mimicking the petrofabric of the tuff. The fabric was thus acquired after deposition, before late rheomorphic processes, and accurately mimics homogeneous deformation features of the shards during welding processes and mass flow.

  4. Large remanent polarization in multiferroic NdFeO3-PbTiO3 thin film

    Science.gov (United States)

    Zhao, Hanqing; Peng, Xin; Zhang, Linxing; Chen, Jun; Yan, Wensheng; Xing, Xianran

    2013-08-01

    The single phase 0.1NdFeO3-0.9PbTiO3 thin film was fabricated on Pt(111)/Ti/SiO2/Si substrate by a sol-gel route. High energy synchrotron radiation glancing incidence X-ray diffraction and conventional X-ray diffraction were employed to determine the phase structure and crystal orientation. Large remanent polarization (2Pr ≈ 85 μC cm-2) was obtained by ferroelectric hysteresis loop and positive up negative down measurements. The oxidation state of Fe element in the film was investigated by X-ray photoelectron spectroscopy and X-ray absorption spectra methods. The results showed the coexistence of Fe2+ and Fe3+ ions with existence of oxygen vacancies. Weak magnetism (˜11 emu/cc) and obvious magnetoelectric coupling were observed in this multiferroic film.

  5. ANNULUS CLOSURE TECHNOLOGY DEVELOPMENT INSPECTION/SALT DEPOSIT CLEANING MAGNETIC WALL CRAWLER

    Energy Technology Data Exchange (ETDEWEB)

    Minichan, R; Russell Eibling, R; James Elder, J; Kevin Kane, K; Daniel Krementz, D; Rodney Vandekamp, R; Nicholas Vrettos, N

    2008-06-01

    The Liquid Waste Technology Development organization is investigating technologies to support closure of radioactive waste tanks at the Savannah River Site (SRS). Tank closure includes removal of the wastes that have propagated to the tank annulus. Although amounts and types of residual waste materials in the annuli of SRS tanks vary, simple salt deposits are predominant on tanks with known leak sites. This task focused on developing and demonstrating a technology to inspect and spot clean salt deposits from the outer primary tank wall located in the annulus of an SRS Type I tank. The Robotics, Remote and Specialty Equipment (RRSE) and Materials Science and Technology (MS&T) Sections of the Savannah River National Laboratory (SRNL) collaborated to modify and equip a Force Institute magnetic wall crawler with the tools necessary to demonstrate the inspection and spot cleaning in a mock-up of a Type I tank annulus. A remote control camera arm and cleaning head were developed, fabricated and mounted on the crawler. The crawler was then tested and demonstrated on a salt simulant also developed in this task. The demonstration showed that the camera is capable of being deployed in all specified locations and provided the views needed for the planned inspection. It also showed that the salt simulant readily dissolves with water. The crawler features two different techniques for delivering water to dissolve the salt deposits. Both water spay nozzles were able to dissolve the simulated salt, one is more controllable and the other delivers a larger water volume. The cleaning head also includes a rotary brush to mechanically remove the simulated salt nodules in the event insoluble material is encountered. The rotary brush proved to be effective in removing the salt nodules, although some fine tuning may be required to achieve the best results. This report describes the design process for developing technology to add features to a commercial wall crawler and the results of the

  6. Assessment of heavy metal pollution from a Fe-smelting plant in urban river sediments using environmental magnetic and geochemical methods.

    Science.gov (United States)

    Zhang, Chunxia; Qiao, Qingqing; Piper, John D A; Huang, Baochun

    2011-10-01

    Environmental magnetic proxies provide a rapid means of assessing the degree of industrial heavy metal pollution in soils and sediments. To test the efficiency of magnetic methods for detecting contaminates from a Fe-smelting plant in Loudi City, Hunan Province (China) we investigated river sediments from Lianshui River. Both magnetic and non-magnetic (microscopic, chemical and statistical) methods were used to characterize these sediments. Anthropogenic heavy metals coexist with coarse-grained magnetic spherules. It can be demonstrated that the Pollution Load Index of industrial heavy metals (Fe, V, Cr, Mo, Zn, Pb, Cd, Cu) and the logarithm of saturation isothermal remanent magnetization, a proxy for magnetic concentration, are significantly correlated. The distribution heavy metal pollution in the Lianshui River is controlled by surface water transport and deposition. Our findings demonstrate that magnetic methods have a useful and practical application for detecting and mapping pollution in and around modern industrial cities. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Structural, optical and magnetic properties of pulsed laser deposited Co-doped ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Karzazi, O., E-mail: ouiame_karzazi@hotmail.fr [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); LPS, Physics Department, Faculty of Sciences, BP 1796, Fes (Morocco); Sekhar, K.C. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); El Amiri, A. [LPTA, Université Hassan II-Casablanca, Faculté des Sciences, B.P. 5366, Maârif (Morocco); Hlil, E.K. [Institut Néel, CNRS, Université J. Fourier, BP 166, 38042 Grenoble (France); Conde, O. [Departamento de Física, Faculdade de Ciências, Universidade de Lisboa and CeFEMA, Campo Grande, 1749-016 Lisboa (Portugal); Levichev, S. [Research Institute for Chemistry, Nizhni Novgorod State University, 603950 Nizhni Novgorod (Russian Federation); Agostinho Moreira, J. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto (Portugal); Chahboun, A. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); FST Tanger, Physics Department, BP 416, Tangier (Morocco); Almeida, A. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto (Portugal); Gomes, M.J.M. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

    2015-12-01

    Zn{sub 1−x}Co{sub x}O films with different Co concentrations (with x=0.00, 0.10, 0.15, and 0.30) were grown by pulsed laser deposition (PLD) technique. The structural and optical properties of the films were investigated by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and photoluminescence (PL). The magnetic properties were measured by conventional magnetometry using a SQUID and simulated by ab-initio calculations using Korring–Khon–Rostoker (KKR) method combined with coherent potential approximation (CPA). The effect of Co-doping on the GIXRD and Raman peaks positions, shape and intensity is discussed. PL studies demonstrate that Co-doping induces a decrease of the bandgap energy and quenching of the UV emission. They also suggest the presence of Zn interstitials when x≥0.15. The 10% Co-doped ZnO film shows ferromagnetism at 390 K with a spontaneous magnetic moment ≈4×10{sup −5} emu and coercive field ≈0.17 kOe. The origin of ferromagnetism is explained based on the calculations using KKR method. - Highlights: • Zn{sub 1−x}Co{sub x}O films (x=0.00, 0.10, 0.15, and 0.30) were grown by (PLD) technique. • Zn{sub 0.9}Co{sub 0.1}O film shows ferromagnetism above room temperature. • The origin of ferromagnetism behavior is attributed to the p-d hybridization. • Co-doping induces a decrease of the bandgap energy of the films.

  8. Deposition and Magnetic Properties of Fe3O4/Fe/Fe3O4Tri-layer Films

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Fe3O4/Fe/Fe3O4 (MIM) tri-layer films (200 nm/12~93 nm/200 nm) were prepared on Si(100) by DC-magnetron reactive-sputtering followed by air- or vacuum-annealing at 280~400℃ for 1.5 h, respectively. Magnetic properties and phases under different sandwich and annealing conditions were studied. In MIM structure, the incorporation of the interlayer iron does increase the magnetization measured under 8 kOe (M8K), but reduce coercivity (Hc). The Hc of as deposited films decreases from 354 Oe to 74 Oe; while M8K increases from 254 to 392 emu/cc. By annealing in air, the whole MIM tri-layer film becomes γ-Fe2Oa, Hc is about 550 Oe and M8K is around 250 emu/cc. The coercivity mechanism of as-deposited and annealed MIM tri layer films belongs to domain-wall pinning type. δM plots show that when the interlayer Fe thickness is 12 nm, the Fe and Fe3O4 layers are decoupled in the as-deposited and annealed states; while it is coupled in the as deposited state when the Fe thickness increases to 23 nm. Vacuum annealing of the MIM films leads to increase in both coercivity and magnetization, and to enhance the exchange coupling between layers.

  9. Channeling and resonant backscattering investigations of Co doped diluted magnetic oxide films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kulkarni, V.N. E-mail: vnk@iitk.ac.in; vnk@squid.umd.edu; Shinde, S.R.; Zhao, Y.G.; Choudhary, R.J.; Ogale, S.B.; Greene, R.L.; Venkatesan, T

    2004-06-01

    We present the results of ion channeling and 3.045 MeV He{sup +} oxygen resonant backscattering along with the results of magnetic and electric characterization experiments performed on thin films of Co doped TiO{sub 2} and La{sub 0.5}Sr{sub 0.5}TiO{sub 3} oxides deposited on (0 0 1) LaAlO{sub 3} substrates using the pulsed laser deposition technique. These films exhibit Curie temperature well above 300 K and hence offer potential use for spintronic devices. In the case of Co doped TiO{sub 2} films the magnetic data have been understood in the light of channeling results, which showed non-substitutionality of Co atoms for the films deposited at 700 deg. C, and their incorporation in the matrix by either annealing at a higher temperature of 875 deg. C or deposition at this temperature. In the case of the Co doped La{sub 0.5}Sr{sub 0.5}TiO{sub 3}, the resistivity data for the films deposited at different oxygen pressures correlate well with the oxygen contents of the films obtained by resonant backscattering.

  10. Steady State Heat Deposits Modeling in the Nb3Sn Quadrupole Magnets for the Upgrade of the LHC Inner Triplet

    CERN Document Server

    Bocian, D; Barzi, E; Bossert, R; Caspi, S; Chlachidze, G; Dietderich, D; Feher, S; Felice, H; Ferracin, P; Hafalia, R; Kashikhin, V V; Lamm, M; Sabbi, G L; Turrioni, D; Wanderer, P; Zlobin, A V

    2012-01-01

    In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. In previous papers, a Network Model has been used to study the thermodynamic behavior of magnet coils and to calculate the quench levels in the LHC magnets for expected beam loss profiles. This model was subsequently used for thermal analysis and design optimization of Nb3Sn quadrupole magnets, which LARP (US LHC Accelerator Research Program) is developing for possible use in the LHC luminosity upgrade. For these new magnets, the heat transport efficiency from the coil to the helium bath needs to be determined and optimized. In this paper the study of helium cooling channels and the heat evacuation scheme are presented and discussed.

  11. Steady State Heat Deposits Modeling in the Nb3Sn Quadrupole Magnets for the Upgrade of the LHC Inner Triplet

    Energy Technology Data Exchange (ETDEWEB)

    Bocian, D.; Ambrosio, G.; Felice, H.; Barzi, E.; Bossert, R.; Caspi, S.; Chlachidze, G.; Dietderich, D.; Feher, S.; Ferracin, P.; Hafalia, R.; /Fermilab /Lawrence Berkeley Lab /Brookhaven

    2011-09-01

    In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. In previous papers, a Network Model has been used to study the thermodynamic behavior of magnet coils and to calculate the quench levels in the LHC magnets for expected beam loss profiles. This model was subsequently used for thermal analysis and design optimization of Nb{sub 3}Sn quadrupole magnets, which LARP (US LHC Accelerator Research Program) is developing for possible use in the LHC luminosity upgrade. For these new magnets, the heat transport efficiency from the coil to the helium bath needs to be determined and optimized. In this paper the study of helium cooling channels and the heat evacuation scheme are presented and discussed.

  12. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, N. S., E-mail: nsokolov@fl.ioffe.ru; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V. [Ioffe Physical-Technical Institute of Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Maksimova, K. Yu.; Grunin, A. I. [Immanuel Kant Baltic Federal University, Kaliningrad 236041 (Russian Federation); Tabuchi, M. [Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603 (Japan)

    2016-01-14

    Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y{sub 3}Fe{sub 5}O{sub 12} (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.

  13. Results of the studies on energy deposition in IR6 superconducting magnets from continuous beam loss on the TCDQ system

    CERN Document Server

    Bracco, C; Presland, A; Redaelli, S; Sarchiapone, L; Weiler, T

    2007-01-01

    A single sided mobile graphite diluter block TCDQ, in combination with a two-sided secondary collimator TCS and an iron shield TCDQM, will be installed in front of the superconducting quadrupole Q4 magnets in IR6, in order to protect it and other downstream LHC machine elements from destruction in the event of a beam dump that is not synchronised with the abort gap. The TCDQ will be positioned close to the beam, and will intercept the particles from the secondary halo during low beam lifetime. Previous studies (1-4) have shown that the energy deposited in the Q4 magnet coils can be close to or above the quench limit. In this note the results of the latest FLUKA energy deposition simulations for Beam 2 are described, including an upgrade possibility for the TCDQ system with an additional shielding device. The results are discussed in the context of the expected performance levels for the different phases of LHC operation.

  14. Stress induced magnetic anisotropy of CoFe2O4 thin films using pulsed laser deposition

    NARCIS (Netherlands)

    Pham Duc Thang, P.D.T.; Rijnders, Augustinus J.H.M.; Blank, David H.A.

    2007-01-01

    Cobalt ferrite (CoFe2O4) thin films (E70 nm) were epitaxially grown on TiO2-terminated (0 0 1) SrTiO3 substrates by pulsed laser deposition (PLD). Films with very smooth surface, which follow the terrace of the substrate, were obtained at temperatures below 600 1C. The magnetic properties of CoFe2O4

  15. Structure and Magnetic Properties of Ni Nanowires Array Fabricated by Direct Current Electro-deposition in Anodic Alumina Membrane

    Institute of Scientific and Technical Information of China (English)

    HUANG Xinmin; ZHU Hong; XU Jinxia

    2005-01-01

    Ordered nanostructure arrays of Ni-Al2O3 were synthesized by direct current electro-deposition in anodic alumina membranes (AAM). The investigation with an electron microscope,an X-ray diffractmeter and a vibration sample magnetometer indicates that the Ni nanowires, growing in the pores of AAM with about 45nm in diameter, are monocrystalline and have a definite preferred crystallizing orientation. The magnetic behavior of the arrays and their mechanism were discussed.

  16. Silanization of Ag-deposited magnetite particles: an efficient route to fabricate magnetic nanoparticle-based Raman barcode materials.

    Science.gov (United States)

    Kim, Kwan; Choi, Jeong-Yong; Lee, Hyang Bong; Shin, Kuan Soo

    2010-07-01

    Silica-coated Ag nanostructures usable as magnetic nanoparticle-based Raman barcode materials were developed. Initially, 283 nm sized spherical magnetite particles composed of 13 nm sized superparamagnetic Fe(3)O(4) nanoparticles were synthesized, and silver deposition was conducted using butylamine as the reductant of AgNO(3) in ethanol. The Ag-deposited Fe(3)O(4) (Fe(3)O(4)@Ag) particles are found to be efficient surface-enhanced Raman scattering (SERS) substrates with the enhancement factor at 632.8 nm excitation to be about 3 x 10(6). After SERS markers such as benzenethiol, 4-mercaptotoluene, 4-aminobenzenethiol, and 4-nitrobenzenethiol were adsorbed onto the silver surface, poly(allylamine hydrochloride) (PAH) was coated onto them using the layer-by-layer deposition method such that a subsequent base-catalyzed silanization could readily form a 60 nm thick silica shell around the PAH layer by a biomimetic process. The cross-linked silica shells effectively prevented the SERS-marker molecules from being liberated from the surface of the Fe(3)O(4)@Ag particles. Although the gram magnetization decreased nearly to one-half of the initial value because of coating with silver and silica, the remaining magnetization was nonetheless strong enough for the silica-coated Fe(3)O(4)@Ag particles to be used as barcode materials operating via SERS.

  17. Preparation and magnetic properties of Co-P thin films

    Institute of Scientific and Technical Information of China (English)

    Haicheng Wang; Zhongmei Du; Lijin Wang; Guanghua Yu; Fengwu Zhu

    2008-01-01

    Magnetic Co-P thin films were prepared by eleetroless deposition. The experiment results show that the film thickness has a significant influence on the coercivity. While the film thickness varied from 300 nm to 5 μm, the coercivity dropped sharply from 45.36 to 22.28 kA/m. As the film thickness increased further, the coercivity varied slowly. When the thickness of the film was 300 nm, the deposited film could realize the coercivity as high as 45.36 kA/m, and the remanent magnetization as high as 800 kA/m .The Co-P films were deposited on the surface of magnetic drums of encoders, whose diameter was 40 mm, and then 512 magnetic poles were recorded, meaning that the magnetizing pitch was 0.245 mm. The testing results indicate that the output signals are perfect, the output waveforms are steady and the pulses account is integral. Compared with the γ-Fe2O3 coating, the Co-P thin film is suitable to be the magnetic recording media for the high resolution magnetic rotary encoder.

  18. Magnetic pyrite cinder as an efficient heterogeneous ozonation catalyst and synergetic effect of deposited Ce.

    Science.gov (United States)

    Wu, Deli; Liu, Ying; He, Hongping; Zhang, Yalei

    2016-07-01

    Heterogeneous catalytic ozonation was emerged to be a promising alternative in the mineralization of various persistent organic pollutants in recent decades. Magnetic pyrite cinder (PyC), which was employed as the catalyst in our investigation, was further deposited by Ce (Ce-PyC) to enhance its catalytic activity in the degradation of aqueous reactive black 5 (RB5). The results showed that additional 17.39%, 42.12% mineralization efficiency was obtained by O3/PyC, O3/Ce-PyC, respectively, in the degradation of RB5 compared to that of O3 alone under identical experimental condition. The reaction mechanism involved the enhanced mineralization of aqueous RB5 at the catalyst-solution interface via hydroxyl radicals produced by the reaction between O3 and catalyst surface. Besides surface hydroxyl, surface Ce(Ⅲ) was crucial for Ce-PyC in the enhanced generation of hydroxyl radicals. More surprisingly, it was found that both PyC and Ce-PyC could exert quite stable catalytic activity in a wide pH range from 3 to 10, which was supposed to be combined with inherently comprised various metal oxide, such as Fe2O3, Fe3O4, MnO2 and CuO. Ozone utilization evaluation demonstrated that PyC and Ce-PyC facilitated effective ozone decomposition, as ozone utilization efficiency (mgTOC/mgO3) of O3/PyC and O3/Ce-PyC increased 64.0%, 155.0%, respectively, compared to that of O3 alone. This investigation provided an effective alternative in the resource utilization of PyC, which was traditionally characterized as a waste material.

  19. Magnetic effects of hydrothermal alteration in porphyry copper and iron-oxide copper-gold systems: A review

    Science.gov (United States)

    Clark, David A.

    2014-06-01

    Magnetic anomaly patterns can be used as a tool for mapping lithology, metamorphic zones and hydrothermal alteration systems, as well as identifying structures that may control passage of magmas or hydrothermal fluids associated with mineralisation. Reliable geological interpretation of mineralised systems requires an understanding of the magmatic, metamorphic and hydrothermal processes that create, alter and destroy magnetic minerals in rocks. Predictive magnetic exploration models for porphyry copper and iron oxide copper-gold (IOCG) deposits can be derived from standard geological models by integrating magnetic petrological principles with petrophysical data, deposit descriptions, and modelling of observed magnetic signatures of these deposits. Even within a particular geological province, the magnetic signatures of similar deposits may differ substantially, due to differences in the local geological setting. Searching for “look-alike” signatures of a known deposit is likely to be unrewarding unless pertinent geological factors are taken into account. These factors include the tectonic setting and magma type, composition and disposition of host rocks, depth of emplacement and post-emplacement erosion level, depth of burial beneath younger cover, post-emplacement faulting and tilting, remanence effects contingent on ages of intrusion and alteration, and metamorphism. Because the effects of these factors on magnetic signatures are reasonably well understood, theoretical magnetic signatures appropriate for the local geological environment can qualitatively guide exploration and make semiquantitative predictions of anomaly amplitudes and patterns. The predictive models also allow detectability of deposit signatures to be assessed, for example when deposits are buried beneath a considerable thickness of nonmagnetic overburden, are covered by highly magnetic heterogeneous volcanic rocks, or there is a strong regional magnetic gradient. This paper reviews the

  20. Magnetic and structural characteristics of multiferroic Fe3O4/(Bi3.25Nd0.65Eu0.10)Ti3O12 composite thin films deposited by metalorganic chemical vapor deposition

    Science.gov (United States)

    Kobune, Masafumi; Furotani, Ryosuke; Fujita, Satoshi; Kikuchi, Kazuki; Kikuchi, Takeyuki; Fujisawa, Hironori; Shimizu, Masaru; Fukumuro, Naoki

    2016-10-01

    Ferromagnetic magnetite (Fe3O4) thin films for magnetoelectric multiferroic applications were deposited on (200) (Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT)/(101) Nb:TiO2 substrates by metalorganic chemical vapor deposition (MOCVD) using an iron(III) tris(2,2,6,6-tetramethyl-3,5-heptanedionato) precursor as the iron source. The BNEuT film utilized as a ferroelectric template material was in the form of freestanding nanoplates with narrow spaces between them. The effects of deposition conditions such as the deposition time and substrate temperature on the magnetic and structural characteristics of the Fe3O4/BNEuT composite films were investigated. All the films consisted of mostly single-phase Fe3O4 with a cubic inverse-spinel structure. When deposition was carried out at temperatures of 400-420 °C, the filling rates of particles introduced into the narrow spaces between the BNEuT nanoplates exhibited high values of 76-89% including the amorphous phase. This suggested that the deposition in this temperature range made progress according to the growth mechanism of MOCVD in the surface reaction rate determining state. Room-temperature magnetic moment-magnetic field curves for Fe3O4 thin films deposited at 400-500 °C for 60 min exhibited narrow rectangular hysteresis loops, indicating typical soft magnetic characteristics.

  1. Magnetization reversal in epitaxial exchange-biased IrMn/FeGa bilayers with anisotropy geometries controlled by oblique deposition

    Science.gov (United States)

    Zhang, Yao; Zhan, Qingfeng; Zuo, Zhenghu; Yang, Huali; Zhang, Xiaoshan; Dai, Guohong; Liu, Yiwei; Yu, Ying; Wang, Jun; Wang, Baomin; Li, Run-Wei

    2015-05-01

    We fabricated epitaxial exchange biased (EB) IrMn/FeGa bilayers by oblique deposition and systematically investigated their magnetization reversal. Two different configurations with the uniaxial magnetic anisotropy Ku parallel and perpendicular to the unidirectional anisotropy Ke b were obtained by controlling the orientation of the incident FeGa beam during deposition. A large ratio of Ku/Ke b was obtained by obliquely depositing the FeGa layer to achieve a large Ku while reducing the IrMn thickness to obtain a small Ke b. Besides the previously reported square loops, conventional asymmetrically shaped loops, and one-sided and two-sided two-step loops, unusual asymmetrically shaped loops with a three-step magnetic transition for the descending branch and a two-step transition for the ascending branch and biased three-step loops were observed at various field orientations in the films of both IrMn (tIrMn=1.5 to 20 nm)/FeGa (10 nm) with Ku⊥ Ke b and IrMn (tIrMn≤2 nm)/FeGa (10 nm) with Ku|| Ke b . Considering the geometries of anisotropies, a model based on domain wall nucleation and propagation was employed to quantitatively describe the angular dependent behaviors of IrMn/FeGa bilayers. The biased three-step magnetic switching was predicted to take place when | Ku|> ɛ90°+Ke b , where ɛ90° is the 90° domain wall nucleation energy, and the EB leads to the appearance of the unusual asymmetrically shaped hysteresis loops.

  2. Pulsed laser deposition of permanent magnetic Nd2Fe14B thin films

    NARCIS (Netherlands)

    Geurtsen, A.J.M.; Kools, J.C.S.; Wit, L.; Lodder, J.C.

    1996-01-01

    Pulsed Laser Deposition (PLD) is applied to deposit thin (thickness typically 100 nm) films of Nd2Fe14B. It is shown that films can be grown which have the desired composition and phase. Nd2Fe14B grows with the c-axis along the film normal on 110 Al2O3 single crystal substrates covered with a Ta lay

  3. A comparison of the magnetic properties of Ni and Co nanowires deposited in different templates and on different substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yalçın, O., E-mail: o.yalcin@nigde.edu.tr [Department of Physics, Niğde University, 51240 Niğde (Turkey); Kartopu, G. [Centre for Solar Energy Research (CSER), Glyndŵr University, OpTIC, St. Asaph Business Park, St. Asaph, LL17 0JD (United Kingdom); Çetin, H. [Department of Physics, Bozok University, 6600 Yozgat (Turkey); Demiray, A.S.; Kazan, S. [Department of Physics, Gebze Institute of Technology, 41400 Gebze, Kocaeli (Turkey)

    2015-01-01

    Nickel (Ni) and cobalt (Co) nanowire arrays (NWs) grown by electrodeposition in porous nano-templates are studied by the ferromagnetic resonance (FMR) technique at room temperature (RT) by comparing the effects of template type (alumina and polycarbonate) and the deposition substrate (i.e., metallic back contact). The line-width and resonance field of the FMR spectra strongly depends on the orientation of the applied field direction. A model is developed to analyze the spectra in order to extract the magnetic parameters such as g-values, spin–spin relaxation times (T{sub 2}) and uniaxial anisotropy parameters. The experimental FMR spectra and their resonance field values were fitted using the imaginary part of magnetic susceptibility and a dispersion relation of magnetization, including the Bloch–Bloembergen type damping term. The easy axes of magnetization for all Ni and Co NWs were found to be perpendicular to the wire-axis. Surface spin modes have been observed only when pure Au was used as substrate. A discussion will be provided to explain the observed differences in terms of the anisotropic behavior and magnetic parameters of the NWs for different substrates and growth templates.

  4. Paleomagnetic age and tectonic constraints on the genesis of the giant Jinding Zn-Pb deposit, Yunnan, China

    Science.gov (United States)

    Yalikun, Yaxiaer; Xue, Chunji; Symons, D. T. A.

    2017-04-01

    The Jinding Zn-Pb deposit is located in the Lanping-Simao basin, Yunnan, China. Paleomagnetic results are reported from the Beichang, Jiayashan, and Nanchang mineralization zones that are hosted in the Lower Cretaceous Jinxing and Upper Paleocene Yunlong Formations. The timing of formation of the Zn-Pb mineralization has not been previously defined but is geologically constrained to be younger than Upper Paleocene. Paleomagnetic analyses of 645 specimens from 42 sites using mostly thermal and then alternating field step demagnetization isolated a stable characteristic remanent magnetization (ChRM) for 29 mineralized sites. Step demagnetization and rock magnetic analyses of Zn and Pb concentrates and tailings show that the main remanence carriers are pyrrhotite and magnetite or low Ti titanomagnetite inclusions in sphalerite and galena. Randomly oriented ChRM directions for 18 clast specimens collected from site 40 provide a conglomerate test that shows that the clasts have not been remagnetized by a metamorphic event. A paleomagnetic fold test on the mineralized specimens is negative, showing that the mineralization is epigenetic because its ChRM substantially postdates the major thrust folding event that formed the dome structure of the Jinding deposit. Using extensive regional geologic and paleomagnetic data from other studies with the Jinding paleomagnetic data yields a mean age of 23 ± 3 Ma for the mineralization.

  5. Assessment of heavy metal pollution from a Fe-smelting plant in urban river sediments using environmental magnetic and geochemical methods

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Chunxia, E-mail: cxzhang@mail.iggcas.ac.cn [State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, No. 19 Bei Tucheng Xilu, Chaoyang Dist., Beijing 100029 (China); Qiao Qingqing [State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, No. 19 Bei Tucheng Xilu, Chaoyang Dist., Beijing 100029 (China); Piper, John D.A. [Geomagnetism Laboratory, Department of Earth and Ocean Science, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Huang, Baochun [State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, No. 19 Bei Tucheng Xilu, Chaoyang Dist., Beijing 100029 (China)

    2011-10-15

    Environmental magnetic proxies provide a rapid means of assessing the degree of industrial heavy metal pollution in soils and sediments. To test the efficiency of magnetic methods for detecting contaminates from a Fe-smelting plant in Loudi City, Hunan Province (China) we investigated river sediments from Lianshui River. Both magnetic and non-magnetic (microscopic, chemical and statistical) methods were used to characterize these sediments. Anthropogenic heavy metals coexist with coarse-grained magnetic spherules. It can be demonstrated that the Pollution Load Index of industrial heavy metals (Fe, V, Cr, Mo, Zn, Pb, Cd, Cu) and the logarithm of saturation isothermal remanent magnetization, a proxy for magnetic concentration, are significantly correlated. The distribution heavy metal pollution in the Lianshui River is controlled by surface water transport and deposition. Our findings demonstrate that magnetic methods have a useful and practical application for detecting and mapping pollution in and around modern industrial cities. - Highlights: > Assessment of heavy metal (HM) pollution in river sediment using magnetic and chemical methods. > HMs from an Fe-smelting plant coexist with coarse-grained magnetic spherules. > A linear correlation between the Pollution Load Index (PLI) of industrial HMs and a magnetic concentration parameter is demonstrated. > The distribution of HM pollution in river sediments is controlled by surface water flow and deposition. - Heavy metal (HM) contamination of river sediments from industrial input by surface water transport and deposition can be detected by using magnetic methods providing a convenient assessment of HM pollution in industrialized cities.

  6. Magnetic polarity stratigraphy of "Mexican Solnhofen" Tlayua Formation, Tepexi de Rodriguez, State of Puebla, Mexico

    Science.gov (United States)

    Urrutia Fucugauchi, J.; Zhao, X.; Girdler, S.; Coe, R.; Gogichaishvili, A.; Benammi, M.; Alvarado-Ortega, J.; Urrutia-Fucugauchi, J.

    2005-05-01

    The Tlayua Formation is the richest Cretaceous fossiliferous locality in Mexico. Research in the quarry has yielded thousands of fossil fish associated with other vertebrate remains. From a vertical section, a total of 95 paleomagnetic specimens from 31 horizons were measured to determine the paleomagnetic signal. Limestones are weakly magnetized and exhibit in general two component magnetizations. The magnetic properties and characteristic remanence are dominated by soft and hard coercivity magnetic minerals, most of which probably formed early in the depositional and diagenetic history. Rock-magnetic properties and a positive reversal test suggest that remanence is primary. The section displays both reverse and normal polarities with mean directions: D = 344.9°, I = 32.4°, k= 21, a95= 4.2°; and D = 149.4°, I = -36.6°, k= 17, a95= 8.7°. Comparison with the North America reference curve, indicates tectonic stability of the region since the Cretaceous. Correlation of these polarity zones with the geomagnetic polarity time scale provides a time framework for the discrepancy of the previous biochronological studies. Based on biostratigraphic age assignments using ammonites, the polarity magnetozone sequence correlates with C34n.1n-C34n.2n chrons, with an age of 100 to 105 Ma for the Tlayua Formation.

  7. Granulometric and magnetic properties of deposited particles in the Beijing subway and the implications for air quality management.

    Science.gov (United States)

    Cui, Guipeng; Zhou, Liping; Dearing, John

    2016-10-15

    The subway system is an important traffic facility in Beijing and its internal air quality is an environmental issue that could potentially affect millions of people every day. Due to the intrinsic nature of rail abrasion in subway tunnels, iron-containing particles can be generated and become suspended in the subway environment. While some studies (e.g. Li et al., 2006) have monitored the in-train levels of PM2.5 (particlesparticles in the Beijing subway system. Here we report results of a study on the granulometric and magnetic properties of deposited particle samples collected at different localities of the Beijing subway system. Our results show that the subway samples are characterized by the presence of fine particles. Volume proportions of 6.1±1.3% for particlesparticlesmagnetic signal, which is approximately two orders of magnitude higher than that in naturally deposited particles collected in Beijing. Fine grained ferromagnetic and ferrimagnetic minerals (e.g. iron and magnetite, respectively) are identified from mineral magnetic measurements and scanning electric microscopy. The samples collected from the Beijing stations with platform screen doors are found to be magnetically stronger and finer than those without them, suggesting that platform screen doors have failed to block the fine iron-containing particles released from the rail tunnel. Given the potential health consequences of fine suspended iron-containing particles, our results have important implications for air quality management in the Beijing subway system.

  8. Electrochemical cell for in situ electrodeposition of magnetic thin films in a superconducting quantum interference device magnetometer.

    Science.gov (United States)

    Topolovec, Stefan; Krenn, Heinz; Würschum, Roland

    2015-06-01

    An electrochemical cell is designed and applied for in situ electrodeposition of magnetic thin films in a commercial SQUID magnetometer system. The cell is constructed in such a way that any parasitic contribution of the cell and of the substrate for electrodeposition to the magnetic moment of the deposited film is reduced to a minimum. A remanent minor contribution is readily taken into account by a proper analysis of the detected signal. Thus, a precise determination of the absolute magnetic moment of the electrodeposited magnetic film during its growth and dissolution is achieved. The feasibility of the cell design is demonstrated by performing Co electrodeposition using cyclic voltammetry. For an average Co film thickness of (35.6 ± 3.0) atomic layers, a magnetic moment per Co atom of (1.75 ± 0.11) μ(B) was estimated, in good agreement with the literature bulk value.

  9. Magnetic properties of BaM /Pd-Pt double-layered thin film deposited at various substrate temperatures

    Science.gov (United States)

    Nahar Shams, Nazmun; Liu, Xiaoxi; Matsumoto, Mitsunori; Morisako, Akimitsu

    2005-05-01

    Crystallographic and magnetic properties of barium ferrite (BaM) thin films deposited onto Pt, Pd, and an alloy of Pd-Pt underlayers by sputtering at different substrate temperatures (Ts) from 400to600°C have been studied. It is found that the coercivity values in the perpendicular direction (Hcperp) of the BaM /Pd-Pt films are higher than those of the BaM films deposited on Pd and Pt underlayers. C-axis orientation of BaM /Pd-Pt film can be achieved at very low Ts of 450°C with a Hcperp of 2.1kOe for 30-nm BaM.

  10. Magnetic mineralogy of the Mercurian lithosphere

    Science.gov (United States)

    Strauss, B. E.; Feinberg, J. M.; Johnson, C. L.

    2016-11-01

    Mercury and Earth are the only inner solar system planets with active, internally generated dynamo magnetic fields. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission recently detected magnetic fields on Mercury that are consistent with lithospheric magnetization. We investigate the physical and chemical environment of Mercury's lithosphere, past and present, to establish the conditions under which magnetization may have been acquired and modified. Three factors are particularly crucial to the determination of crustal composition and iron mineralogy: redox conditions in the planet's crust and mantle, the iron content of the lithosphere, and, for any remanent magnetization, the temperature profile of the lithosphere and its evolution over time. We explore potential mechanisms for remanence acquisition and alteration on Mercury, whose surface environment is both hot and highly reducing. The long-term thermal history of Mercury's crust plays an important role in the longevity of any remanent crustal magnetization, which may be subject to remagnetization through thermal, viscous, and shock mechanisms. This thermal and compositional framework is used both to constrain plausible candidate minerals that could carry magnetic remanence on Mercury and to evaluate their capacity to acquire and retain sufficient magnetization to be detectable from satellite orbit. We propose that iron metal and its alloys are likely to be the dominant contributors to induced and remanent magnetization in Mercury's lithosphere, with additional contributions from iron silicides, sulfides, and carbides.

  11. Lodestone: Nature's own permanent magnet

    Science.gov (United States)

    Wasilewski, P.

    1976-01-01

    Magnetic hysteresis and microstructural details are presented which explain why the class of magnetic iron ores defined as proto-lodestones, can behave as permanent magnets, i.e. lodestones. Certain of these proto-lodestones which are not permanent magnets can be made into permanent magnets by charging in a field greater than 1000 oersted. This fact, other experimental observations, and field evidence from antiquity and the middle ages, which seems to indicate that lodestones are found as localized patches within massive ore bodies, suggests that lightning might be responsible for the charging of lodestones. The large remanent magnetization, high values of coercive force, and good time stability for the remanent magnetization are all characteristics of proto-lodestone iron ores which behave magnetically as fine scale ( 10 micrometer) intergrowths when subjected to magnetic hysteresis analysis. The magnetic results are easily understood by analysis of the complex proto lodestone microstructural patterns observable at the micrometer scale and less.

  12. Functionalization and Area-Selective Deposition of Magnetic Carbon-Coated Iron Nanoparticles from Solution

    Directory of Open Access Journals (Sweden)

    Erika Widenkvist

    2011-01-01

    Full Text Available A route to area-selective deposition of carbon-coated iron nanoparticles, involving chemical modification of the surface of the particles, is described. Partial oxidative etching of the coating introduces carboxylic groups, which then are esterified. The functionalized particles can be selectively deposited on the Si areas of Si/SiO2 substrates by a simple dipping procedure. Nanoparticles and nanoassemblies have been analyzed using SEM, TEM, and XPS.

  13. Theoretical Investigation of Influence of Mechanical Stress on Magnetic Properties of Ferromagnetic/Antiferromagnetic Bilayers Deposited on Flexible Substrates

    Institute of Scientific and Technical Information of China (English)

    Yu-Hao Bai; Xia Wang; Lin-Ping Mu; Xiao-Hong Xu

    2016-01-01

    Effect of mechanical stress on magnetic properties of an exchange-biased ferromagnetic/antiferromagnetic bilayer deposited on a flexible substrate is investigated.The hysteresis loops with different magnitudes and orientations of the stress can be classified into three types.The corresponding physical conditions for each type of the loop are deduced based on the principle of minimal energy.The equation of the critical stress is derived,which can judge whether the loops show hysteresis or not.Numerical calculations suggest that except for the magnitude of the mechanical stress,the relative orientation of the stress is also an important factor to tune the exchange bias effect.

  14. Static and high frequency magnetic properties of FeGa thin films deposited on convex flexible substrates

    Science.gov (United States)

    Yu, Ying; Zhan, Qingfeng; Wei, Jinwu; Wang, Jianbo; Dai, Guohong; Zuo, Zhenghu; Zhang, Xiaoshan; Liu, Yiwei; Yang, Huali; Zhang, Yao; Xie, Shuhong; Wang, Baomin; Li, Run-Wei

    2015-04-01

    Magnetostrictive FeGa thin films were deposited on the bowed flexible polyethylene terephthalate (PET) substrates, which were fixed on the convex mold. A compressive stress was induced in FeGa films when the PET substrates were shaped from convex to flat. Due to the effect of magnetostriction, FeGa films exhibit an obvious in-plane uniaxial magnetic anisotropy which could be enhanced by increasing the applied pre-strains on the substrates during growth. Consequently, the ferromagnetic resonance frequency of the films was significantly increased, but the corresponding initial permeability was decreased. Moreover, the films with pre-strains less than 0.78% exhibit a working bandwidth of microwave absorption about 2 GHz. Our investigations demonstrated a convenient method via the pre-strained substrates to tune the high frequency properties of magnetic thin films which could be applied in flexible microwave devices.

  15. Static and high frequency magnetic properties of FeGa thin films deposited on convex flexible substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ying [Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105 (China); Zhan, Qingfeng, E-mail: zhanqf@nimte.ac.cn, E-mail: runweili@nimte.ac.cn; Dai, Guohong; Zuo, Zhenghu; Zhang, Xiaoshan; Liu, Yiwei; Yang, Huali; Zhang, Yao; Wang, Baomin; Li, Run-Wei, E-mail: zhanqf@nimte.ac.cn, E-mail: runweili@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Wei, Jinwu; Wang, Jianbo [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Xie, Shuhong [Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105 (China)

    2015-04-20

    Magnetostrictive FeGa thin films were deposited on the bowed flexible polyethylene terephthalate (PET) substrates, which were fixed on the convex mold. A compressive stress was induced in FeGa films when the PET substrates were shaped from convex to flat. Due to the effect of magnetostriction, FeGa films exhibit an obvious in-plane uniaxial magnetic anisotropy which could be enhanced by increasing the applied pre-strains on the substrates during growth. Consequently, the ferromagnetic resonance frequency of the films was significantly increased, but the corresponding initial permeability was decreased. Moreover, the films with pre-strains less than 0.78% exhibit a working bandwidth of microwave absorption about 2 GHz. Our investigations demonstrated a convenient method via the pre-strained substrates to tune the high frequency properties of magnetic thin films which could be applied in flexible microwave devices.

  16. Structural and magnetic properties of epitaxial delafossite CuFeO{sub 2} thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Toyanath; Senty, Tess R.; Trappen, Robbyn; Zhou, Jinling; Borisov, Pavel; Holcomb, Mikel B.; Bristow, Alan D.; Lederman, David [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315 (United States); Chen, Song; Song, Xueyan [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6070 (United States); Ferrari, Piero; Cabrera, Alejandro L. [Pontificia Universidad Catolica, Instituto de Física, Santiago (Chile)

    2015-01-07

    Growth of pure phase delafossite CuFeO{sub 2} thin films on Al{sub 2}O{sub 3} (00.1) substrates by pulsed laser deposition was systematically investigated as a function of growth temperature and oxygen pressure. X-ray diffraction, transmission electron microscopy, Raman scattering, and x-ray absorption spectroscopy confirmed the existence of the delafossite phase. Infrared reflectivity spectra determined a band edge at 1.15 eV, in agreement with the bulk delafossite data. Magnetization measurements on CuFeO{sub 2} films demonstrated a phase transition at T{sub C} ≈ 15 ± 1 K, which agrees with the first antiferromagnetic transition at 14 K in the bulk CuFeO{sub 2}. Low temperature magnetic phase is best described by commensurate, weak ferromagnetic spin ordering along the c-axis.

  17. Deposition temperature mediated tunable tilt angle magnetization in Co-Pt/Ni81Fe19 exchange springs

    Science.gov (United States)

    Saravanan, P.; Hsu, Jen-Hwa; Tsai, C. L.; Lee, C.-M.

    2015-05-01

    In this study, we investigate the effect of deposition temperature of Co-Pt fixed layer, Td,CoPt (150, 250 and 350 °C) on the tilt angle magnetization (θM) of Ni81Fe19-layer grown at room temperature (RT) and at different thicknesses (tNiFe=0, 1.0, 2.5 and 4.0 nm) in Co-Pt(Td,CoPt)/NiFe(tNiFe) exchange springs. The magnetic studies demonstrated a strong perpendicular magnetic anisotropy (PMA) for the equi-compositional ordered Co-Pt layer grown on glass substrate using the film sequence: Ta(20 nm)/Pt(20 nm)/CoPt(5 nm), regardless of Td,CoPt. The PMA can be retained with the addition of a 4-nm NiFe layer on the top when Td,CoPt≥250 °C. In contrast, relatively a thin layer of Ni-Fe (2.5 nm) can destroy the perpendicular exchange-spring behavior if the Co-Pt layer is deposited at RT. Using 3-D micromagnetic simulation, the interfacial exchange coupling strength (Aij) between the Co-Pt and NiFe-layers was estimated and the Aij value is found to increase rapidly when Td,CoPt is increased from RT to 300 °C. Besides, the magnetization tilted angle (θM) of NiFe can be easily tuned from completely out-of-plane to almost 60° when tNiFe=4.0 nm. Through this study, it is demonstrated that the θM of NiFe-layer can be tuned by not only altering the tNiFe; but also by varying the Td,CoPt.

  18. Deposition temperature mediated tunable tilt angle magnetization in Co–Pt/Ni{sub 81}Fe{sub 19} exchange springs

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, P. [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); Hsu, Jen-Hwa, E-mail: jhhsu@phys.ntu.edu.tw [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Tsai, C.L. [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Lee, C.-M. [Graduate School of Materials Science, National Yunlin University of Science and Technology, Douliou 64002, Taiwan (China)

    2015-05-01

    In this study, we investigate the effect of deposition temperature of Co–Pt fixed layer, T{sub d,CoPt} (150, 250 and 350 °C) on the tilt angle magnetization (θ{sub M}) of Ni{sub 81}Fe{sub 19}-layer grown at room temperature (RT) and at different thicknesses (t{sub NiFe}=0, 1.0, 2.5 and 4.0 nm) in Co–Pt(T{sub d,CoPt})/NiFe(t{sub NiFe}) exchange springs. The magnetic studies demonstrated a strong perpendicular magnetic anisotropy (PMA) for the equi-compositional ordered Co–Pt layer grown on glass substrate using the film sequence: Ta(20 nm)/Pt(20 nm)/CoPt(5 nm), regardless of T{sub d,CoPt}. The PMA can be retained with the addition of a 4-nm NiFe layer on the top when T{sub d,CoPt}≥250 °C. In contrast, relatively a thin layer of Ni–Fe (2.5 nm) can destroy the perpendicular exchange-spring behavior if the Co–Pt layer is deposited at RT. Using 3-D micromagnetic simulation, the interfacial exchange coupling strength (A{sub ij}) between the Co–Pt and NiFe-layers was estimated and the A{sub ij} value is found to increase rapidly when T{sub d,CoPt} is increased from RT to 300 °C. Besides, the magnetization tilted angle (θ{sub M}) of NiFe can be easily tuned from completely out-of-plane to almost 60° when t{sub NiFe}=4.0 nm. Through this study, it is demonstrated that the θ{sub M} of NiFe-layer can be tuned by not only altering the t{sub NiFe}; but also by varying the T{sub d,CoPt}. - Highlights: • Equi-compositional ordered 5-nm thick Co–Pt with strong PMA was grown on glass. • The ordered Co–Pt and Ni{sub 81}Fe{sub 19} layers were utilized for OOP and IP-anisotropies. • Tunable tilt angle magnetization was investigated by varying T{sub d,CoPt}. • Using micromagnetic simulation, interfacial exchange coupling strength was deduced. • Deposition temperature mediated θ{sub M} in Co–Pt/NiFe provides a new scope for STO.

  19. The role of hematite ilmenite solid solution in the production of magnetic anomalies in ground- and satellite-based data

    Science.gov (United States)

    Kletetschka, Gunther; Wasilewski, Peter J.; Taylor, Patrick T.

    2002-03-01

    Remanent magnetization (RM) of rocks with hematite-ilmenite solid solution (HISS) minerals, at all crustal levels, may be an important contribution to magnetic anomalies measured by ground and satellite altitude surveys. The possibility that lower thermal gradient relatively deep in the crust can result in exsolution of HISS compositions with strong remanent magnetizations (RM) was studied for two bulk compositions within the HISS system. Samples from granulite-terrane around Wilson Lake, Labrador, Canada contains titanohematite with exsolved ferrian ilmenite lamellae. Other samples from the anorthosite-terrane of Allard Lake, Quebec, Canada contain ferrian ilmenite with exsolved titanohematite lamellae. In both cases, the final exsolved titanohematite has similar Ti content and carries dominant magnetic remanence with REM (=NRM/SIRM, where NRM is the natural remanent magnetization and SIRM is the saturation isothermal remanent magnetization) that is comparable to the Ti-free end member. The RM was acquired prior to exsolution and the ilmeno-hematite-rich rock possesses thermal remanent magnetization (TRM), whereas rocks with hemo-ilmenite possess chemical remanent magnetization (CRM). In both cases, we found fairly large homogeneous grains with low demagnetizing energy that acquired intense RM. The magnetism of the ilmeno-hematite solid solution phases is not significantly perturbed by the continuous reaction: ilmeno-hematite≧titanohematite solid solution. Hence, the occurrence of HISS in rocks that cooled slowly in a low intensity magnetic field will have an intense magnetic signature characterized by a large REM.

  20. Microstructures and magnetic properties of L1{sub 0} FePt films deposited on NaCl-type films

    Energy Technology Data Exchange (ETDEWEB)

    Sun, T.H., E-mail: s9931829@m99.nthu.edu.tw [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, S.C.; Su, W.H. [Department of Materials Engineering and Center for Thin Film Technologies and Applications, Ming Chi University of Technology, Taipei 24301, Taiwan (China); Chen, J.R. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2013-10-01

    A single-layered FePt film of 30 nm thickness with perpendicular magnetic anisotropy is achieved by depositing the film onto a heated Si(100) substrate at 620 °C. Its perpendicular coercivity (Hc{sub ⊥}), saturation magnetization (M{sub s}) and perpendicular squareness (S{sub ⊥}) are as high as 1113 kA/m, 0.594 Wb/m{sup 2} and 0.96, respectively. The perpendicular magnetic anisotropy degrades when a 5-nm NiO film is introduced under this single-layered film. Upon further increasing the thickness of the NiO film to 10 nm, the Hc{sub ⊥} of the single-layered film decreases greatly to around 330 kA/m. Compared to a NiO underlayer, the Hc{sub ⊥} of the FePt film remains above 1000 kA/m when a 10-nm MgO underlayer is introduced. Furthermore, when the thickness of the MgO underlayer is decreased to 5 nm, the perpendicular magnetic anisotropy of the single-layered FePt film is further enhanced. Its Hc{sub ⊥} stays high at 1081 kA/m; however, S{sub ⊥} increases significantly to 1. - Highlights: ► A thin MgO underlayer enhances the perpendicular magnetic anisotropy of FePt film. ► A NiO underlayer degrades the perpendicular magnetic anisotropy of the film. ► Ni atoms diffuse from NiO underlayer into FePt layer forming NiFe compounds.

  1. Structural and magnetic characterization of FePt films deposited onto SiO{sub 2} spherical particle arrays

    Energy Technology Data Exchange (ETDEWEB)

    Brombacher, Christoph; Makarov, Denys; Schatz, Guenter; Albrecht, Manfred [University of Konstanz, Department of Physics, D-78457 Konstanz (Germany); Maret, Mireille; Liscio, Fabiola [Laboratoire de Thermodynamique et Physico-Chimie Metallurgiques, ENSEEG, Saint Martin d' Heres (France)

    2007-07-01

    The growth of FePt films at 450 C on a Pt/Cr buffer layer deposited onto SiO{sub 2} spherical particle arrays and for comparison on flat thermally oxidized Si(001) substrates has been studied. The structural properties of the FePt films, such as the orientation and size of the crystalline grains and the degree of L1{sub 0}-type chemical ordering, were investigated by in-situ RHEED and ex-situ XRD. Magnetic characterization was performed by MFM, polar MOKE and SQUID. Increasing the Cr buffer underlayer thickness favors the formation of the FePt chemically ordered L1{sub 0} phase. An out-of-plane coercivity of the FePt alloy about 4 kOe was thus obtained for a Cr thickness of 50 nm. While the continuous films on oxidized Si(001) substrates show magnetic domain patterns with domain sizes in the range of 50-100 nm, multi-domain states are observed for the FePt alloy grown on the particle arrays. The influence of the Cr underlayer thickness and Pt buffer layer on the magnetic properties of FePt are discussed for various particle arrays and compared to micromagnetic simulations, providing a description of magnetization reversal.

  2. Magnetic anisotropy and high-frequency property of flexible FeCoTa films obliquely deposited on a wrinkled topography.

    Science.gov (United States)

    Li, Jincai; Zhan, Qingfeng; Zhang, Shuanglan; Wei, Jinwu; Wang, Jianbo; Pan, Minjie; Xie, Yali; Yang, Huali; Zhou, Zheng; Xie, Shuhong; Wang, Baomin; Li, Run-Wei

    2017-06-06

    We investigated the magnetic anisotropy and the high-frequency property of flexible Fe60Co26Ta14 (FeCoTa) thin films obtained by oblique sputtering onto a wrinkled surface. The sinuously wrinkled topography is produced by growing Ta layer on a pre-strained polydimethylsiloxane (PDMS) membrane. Due to the enhanced effect of shadowing, the oblique deposition of FeCoTa layer gives rise to a shift of wrinkle peak towards the incident atomic flux. With increasing the PDMS pre-strain or increasing the oblique sputtering angle, both the uniaxial magnetic anisotropy and the ferromagnetic resonance frequency of FeCoTa films are enhanced, but the initial permeability decreases. The magnetization reversal mechanism of wrinkled FeCoTa films can be interpreted by a two-phase model composed of both coherent rotation and domain wall nucleation. With the enhancement of uniaxial magnetic anisotropy, the domain wall nucleation becomes pronounced in FeCoTa films.

  3. Surface chemistry of group 11 atomic layer deposition precursors on silica using solid-state nuclear magnetic resonance spectroscopy

    Science.gov (United States)

    Pallister, Peter J.; Barry, Seán T.

    2017-02-01

    The use of chemical vapour deposition (CVD) and atomic layer deposition (ALD) as thin film deposition techniques has had a major impact on a number of fields. The deposition of pure, uniform, conformal thin films requires very specific vapour-solid reactivity that is largely unknown for the majority of ALD and CVD precursors. This work examines the initial chemisorption of several thin film vapour deposition precursors on high surface area silica (HSAS) using 13C, 31P, and quantitative 29Si nuclear magnetic resonance spectroscopy (NMR). Two copper metal precursors, 1,3-diisopropyl-imidazolin-2-ylidene copper (I) hexamethyldisilazide (1) and 1,3-diethyl-imidazolin-2-ylidene copper(I) hexamethyldisilazide (2), and one gold metal precursor, trimethylphosphine gold(III) trimethyl (3), are examined. Compounds 1 and 2 were found to chemisorb at the hydroxyl surface-reactive sites to form a ||-O-Cu-NHC surface species and fully methylated silicon (||-SiMe3, due to reactivity of the hexamethyldisilazane (HMDS) ligand on the precursor) at 150 °C and 250 °C. From quantitative 29Si solid-state NMR (SS-NMR) spectroscopy measurements, it was found that HMDS preferentially reacts at geminal disilanol surface sites while the copper surface species preferentially chemisorbed to lone silanol surface species. Additionally, the overall coverage was strongly dependent on temperature, with higher overall coverage of 1 at higher temperature but lower overall coverage of 2 at higher temperature. The chemisorption of 3 was found to produce a number of interesting surface species on HSAS. Gold(III) trimethylphosphine, reduced gold phosphine, methylated phosphoxides, and graphitic carbon were all observed as surface species. The overall coverage of 3 on HSAS was only about 10% at 100 °C and, like the copper compounds, had a preference for lone silanol surface reactive sites. The overall coverage and chemisorbed surface species have implications to the overall growth rate and purity of

  4. Structures and magnetic properties of Fe-Si-O films RF-sputtered in a high magnetic field

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We have investigated the effects of high magnetic fields on the microstructures and magnetic properties of Fe-Si-O films deposited by RF sputtering. Three typical sample appearances,hole-in-center,phase-separation and hybridization were obtained for the Fe-Si-O films prepared in the oxygen-argon flow ratio VO2/Vtotal<1.0%,magnetic field Bappl≤1.0 T regime,indicating that not only the dis-tribution of plasma but also the angular distribution of sput-tered atoms are influenced by a high magnetic field. In the oxygen-argon flow ratio VO2/Vtotal>2.0%,magnetic field Bappl≥2.0 T regime,strong (110) orientation of Fe3O4 grains and larger remanence and coercivity measured in the direction normal to the film plane appeared in the Fe-Si-O films. This result indicates that the high magnetic fields not only orient the Fe-Si-O film but also induce remarkable perpendicular magnetic anisotropy during the deposition.

  5. Electroplated thick-film cobalt platinum permanent magnets

    Science.gov (United States)

    Oniku, Ololade D.; Qi, Bin; Arnold, David P.

    2016-10-01

    The material and magnetic properties of multi-micron-thick (up to 6 μm) L10 CoPt magnetic films electroplated onto silicon substrates are investigated as candidate materials for integration in silicon-based microsystems. The influence of various process conditions on the structure and magnetic properties of electroplated CoPt thick-films is studied in order to better understand the complex process/structure/property relationships associated with the electroplated films. Process variables studied here include different seed layers, electroplating current densities (ranging from 25-200 mA/cm2), deposition times (up to 60 min), and post-deposition annealing times and temperatures. Analyses include film morphology, film thickness, composition, surface roughness, grain size, phase volume fractions, and L10 ordering parameter. Key correlations are found relating process and structure variations to the extrinsic magnetic properties (remanence, coercivity, squareness, and energy product). Strong hard magnetic properties (Br ~0.8 T, Hci ~800 kA/m, squareness close to 0.9, and BHmax of 100 kJ/m3) are obtained for films deposited on Si/TiN/Ti/Cu at current densities of 100 mA/cm2, pH of 7, and subsequently annealed at 675 °C for 30 min.

  6. On the temporal variation of leaf magnetic parameters: seasonal accumulation of leaf-deposited and leaf-encapsulated particles of a roadside tree crown.

    Science.gov (United States)

    Hofman, Jelle; Wuyts, Karen; Van Wittenberghe, Shari; Samson, Roeland

    2014-09-15

    Understanding the accumulation behaviour of atmospheric particles inside tree leaves is of great importance for the interpretation of biomagnetic monitoring results. In this study, we evaluated the temporal variation of the saturation isothermal remanent magnetisation (SIRM) of leaves of a roadside urban Platanus × acerifolia Willd. tree in Antwerp, Belgium. We hereby examined the seasonal development of the total leaf SIRM signal as well as the leaf-encapsulated fraction of the deposited dust, by washing the leaves before biomagnetic analysis. On average 38% of the leaf SIRM signal was exhibited by the leaf-encapsulated particles. Significant correlations were found between the SIRM and the cumulative daily average atmospheric PM10 and PM2.5 measurements. Moreover, a steady increase of the SIRM throughout the in-leaf season was observed endorsing the applicability of biomagnetic monitoring as a proxy for the time-integrated PM exposure of urban tree leaves. Strongest correlations were obtained for the SIRM of the leaf-encapsulated particles which confirms the dynamic nature of the leaf surface-accumulated particles.

  7. Debris reduction for copper and diamond-like carbon thin films produced by magnetically guided pulsed laser deposition

    CERN Document Server

    Tsui, Y Y; Vick, D; Fedosejevs, R

    2002-01-01

    The effectiveness of debris reduction using magnetically guided pulsed laser deposition (MGPLD) is reported here. KrF laser pulses (248 nm) of 100 mJ energy were focused to intensities of 6x10 sup 9 W/cm sup 2 onto the surface of a copper or a carbon source target and a magnetic field of 0.3 T as used to steer the plasma around a curved arc of 0.5 m length to the deposition substrate. Debris counts were compared for films produced by the MGPLD and conventional PLD (nonguided) techniques. A significant reduction in particulates of size greater than 0.1 mu m was achieved using MGPLD. For the copper films, particulate count was reduced from 150 000 particles/cm sup 2 /nm to 50 particulates/cm sup 2 /nm and for diamond-like carbon thin films particulate count was reduced from 25 000 particles/cm sup 2 /nm to 1200 particles/cm sup 2 /nm.

  8. The application of magnetic self-filter to optimization of AIN film growth process during the impulse plasma deposition synthesis

    Directory of Open Access Journals (Sweden)

    Chodun Rafal

    2016-03-01

    Full Text Available This work presents the very first results of the application of plasma magnetic filtering achieved by a coil coupled with an electrical circuit of a coaxial accelerator during the synthesis of A1N thin films by use of Impulse Plasma Deposition method (IPD. The uniqueness of this technical solution lies in the fact that the filter is not supplied, controlled and synchronized from any external device. Our solution uses the energy from the electrical circuit of plasma accelerator. The plasma state was described on the basis of OES studies. Estimation of the effects of plasma filtering on the film quality was carried out on the basis of characterization of structure morphology (SEM, phase and chemical composition (vibrational spectroscopy. Our work has shown that the use of the developed magnetic self-filter improved the structure of the AlN coatings synthesized under the condition of impulse plasma, especially by the minimization of the tendency to deposit metallic aluminum droplets and columnar growth.

  9. Dependence of Magnetic Properties of Co/Pt Multilayers on Deposition Temperature of Pt Buffer Layers

    Science.gov (United States)

    Shiomi, Shigeru; Nishimura, Tomotaka; Kobayashi, Tadashi; Masuda, Morio

    1993-04-01

    A 15-nm-thick Pt buffer layer was deposited on a glass slide at temperature Ts(Ptbuf) ranging from 30 to 300°C by e-gun evaporation. Following the cooling in vacuum to ambient temperature, Co and Pt layers have been alternately deposited on it. Very large perpendicular anisotropy and coercivity have been obtained at Ts(Ptbuf) higher than 200°C. The (111) preferred orientation of the Co/Pt multilayer as well as the Pt buffer layer became more pronounced with elevating Ts(Ptbuf), to which the enhancement of perpendicular anisotropy with elevating Ts(Ptbuf) might be ascribable.

  10. Single-domain chemical, thermochemical and thermal remanences in a basaltic rock

    CERN Document Server

    Draeger, U; Poidras, T; Riisager, J; Draeger, Ulrike; Pr\\'{e}vot, Michel; Poidras, Thierry; Riisager, Janna

    2005-01-01

    Tiny basaltic samples containing finely grained titanomagnetite with Curie temperature less than 100 C were heated in air in weak field (25 to 100microT) at temperatures between 400 and 560 C for times as long as 32 hours. Oxyexsolution of titanomagnetite resulted in the crystallization of interacting single domain particles with Curie point close to 540 C and the concomitant development of one of two types chemical remanence, depending upon thermal treatment: isothermal chemical remanence (CRM) or thermochemical remanence (TCRM), the latter acquired under the combined effects of chemical change and temperature decrease. CRM and TCRM acquired under various conditions were subjected to Thellier-type experiments. The CRM/TRM ratio is found to be less than one and increases rapidly with acquisition temperature (0.35 at 400 C, 0.65 at 450 C, and 0.90 at 500 C). Thus, very large underestimate of geomagnetic field paleostrength can occur when a natural CRM is not recognized as such and is believed to be a natural T...

  11. Naturally Produced Co/CoO Nanocrystalline Magnetic Multilayers: Structure and Inverted Hysteresis.

    Science.gov (United States)

    Santarossa, Francesca; Pappas, Spiridon D; Delimitis, Andreas; Sousanis, Andreas; Poulopoulos, Panagiotis

    2016-05-01

    Cobalt-based multilayers with excellent sequencing are grown via radiofrequency magnetron sputtering with the use of one Co target and natural oxidation. The Co layers are continuous, fully textured {111} and have the face centered cubic structure. At the end of deposition of each Co layer air is let to flow into the vacuum chamber via a fine (leak) valve. The top of Co is oxidized. The oxidized layers consist of cubic CoO crystallites. Near the film surface hexagonal Co(OH)2 is also detected. Magneto-optical Kerr effect hysteresis loops show in-plane magnetized films. The magnetic saturation field in the out-of-plane measurements is large exceeding 12 kOe. This observation supports indirectly the fact that Co is face centered cubic; if it was c-axis textured hexagonal the magnetocrystalline anisotropy would be large resulting in smaller values of the saturation field. As the Co-layer thickness decreases the in-plane loops show reduced remanence, slow approach to magnetic saturation and the out-of-plane loops show inverted hysteresis and/or crossing loop features with sizeable remanence. The effects are discussed with respect to the enhanced orbital magnetic moment of Co and the antiferromagnetic coupling between Co spins at the Co/CoO interface.

  12. Most critical collimator-mask-magnet sequence in the SPS-to-LHC transfer lines: energy deposition study.

    CERN Document Server

    Marzo, Matteo; Lechner, Anton; Vlachoudis, Vasilis

    2017-01-01

    This technical note refers to a study on the relation between the impact conditions of the SPS 450GeV proton beam and the energy deposited downstream the Target Collimator Dump In- jection Long (TCDIL) collimators [1], in the SPS-to-LHC transfer lines TI2 and TI8. Such an analysis is relevant in order to simulate the worst scenario of failure, in case the beam impacts on the TCDIL collimator’s jaw, in the frame of the LHC Injectors Upgrade (LIU), in view of the High Luminosity LHC (HL-LHC) phase. Previous studies already showed the dependency of the energy deposited in the downstream masks on the collimators-masks distance [2]. In absence of a (realistic) impact parameter, we perform now a study to select the most pessimistic one, trying to understand the origin of the various components responsible for the energy deposition on the downstream mask and magnet. The set up of the Monte Carlo FLUKA [3] [4] simulations and the most relevant results will be presented in this document. A sensitivity analysis was a...

  13. Optimally segmented permanent magnet structures

    DEFF Research Database (Denmark)

    Insinga, Andrea Roberto; Bjørk, Rasmus; Smith, Anders

    2016-01-01

    We present an optimization approach which can be employed to calculate the globally optimal segmentation of a two-dimensional magnetic system into uniformly magnetized pieces. For each segment the algorithm calculates the optimal shape and the optimal direction of the remanent flux density vector...

  14. Engineering and Scaling the Spontaneous Magnetization Reversal of Faraday Induced Magnetic Relaxation in Nano-Sized Amorphous Ni Coated on Crystalline Au

    Directory of Open Access Journals (Sweden)

    Wen-Hsien Li

    2016-05-01

    Full Text Available We report on the generation of large inverse remanent magnetizations in nano-sized core/shell structure of Au/Ni by turning off the applied magnetic field. The remanent magnetization is very sensitive to the field reduction rate as well as to the thermal and field processes before the switching off of the magnetic field. Spontaneous reversal in direction and increase in magnitude of the remanent magnetization in subsequent relaxations over time were found. All of the various types of temporal relaxation curves of the remanent magnetizations are successfully scaled by a stretched exponential decay profile, characterized by two pairs of relaxation times and dynamic exponents. The relaxation time is used to describe the reduction rate, while the dynamic exponent describes the dynamical slowing down of the relaxation through time evolution. The key to these effects is to have the induced eddy current running beneath the amorphous Ni shells through Faraday induction.

  15. Efeito do campo magnético na precipitação de parafinas Magnetic field effect on paraffin deposition

    Directory of Open Access Journals (Sweden)

    Nelson de Oliveira Rocha

    1998-02-01

    Full Text Available In the oil industry, the paraffination phenomenon is a major problem during oil production, displacement and treatment. Paraffin deposition in subsea flowlines, surface equipment, production string or even in the reservoir, can cause significant and increasing oil losses. To minimize paraffin precipitation, the application of magnetic field in the petroleum path has been suggested based on empiric studies. In this study, we assembled a labscale magnetic conditioner to determine the influence of magnetic field on the physical-chemical properties of two fluids : oil and a paraffin mixture. We observed that magnetic field reduce sample aparent viscosity due to crystal morphology alteration.

  16. Magnetic and gravity gradiometry framework for Mesoproterozoic iron oxide-apatite and iron oxide-copper-gold deposits, southeast Missouri, USA

    Science.gov (United States)

    McCafferty, Anne E.; Phillips, Jeffrey; Driscoll, Rhonda L.

    2016-01-01

    High-resolution airborne magnetic and gravity gradiometry data provide the geophysical framework for evaluating the exploration potential of hidden iron oxide deposits in Mesoproterozoic basement rocks of southeast Missouri. The data are used to calculate mineral prospectivity for iron oxide-apatite (IOA) ± rare earth element (REE) and iron oxide-copper-gold (IOCG) deposits. Results delineate the geophysical footprints of all known iron oxide deposits and reveal several previously unrecognized prospective areas. The airborne data are also inverted to three-dimensional density and magnetic susceptibility models over four concealed deposits at Pea Ridge (IOA ± REE), Boss (IOCG), Kratz Spring (IOA), and Bourbon (IOCG). The Pea Ridge susceptibility model shows a magnetic source that is vertically extensive and traceable to a depth of greater than 2 km. A smaller density source, located within the shallow Precambrian basement, is partly coincident with the magnetic source at Pea Ridge. In contrast, the Boss models show a large (625-m-wide), vertically extensive, and coincident dense and magnetic stock with shallower adjacent lobes that extend more than 2,600 m across the shallow Precambrian paleosurface. The Kratz Spring deposit appears to be a smaller volume of iron oxides and is characterized by lower density and less magnetic rock compared to the other iron deposits. A prospective area identified south of the Kratz Spring deposit shows the largest volume of coincident dense and nonmagnetic rock in the subsurface, and is interpreted as prospective for a hematite-dominant lithology that extends from the top of the Precambrian to depths exceeding 2 km. The Bourbon deposit displays a large bowl-shaped volume of coincident high density and high-magnetic susceptibility rock, and a geometry that suggests the iron mineralization is vertically restricted to the upper parts of the Precambrian basement. In order to underpin the evaluation of the prospectivity and three

  17. Mössbauer and Magnetic Properties of Coherently Mixed Magnetite-Cobalt Ferrite Grown by Infrared Pulsed-Laser Deposition

    Directory of Open Access Journals (Sweden)

    Juan de la Figuera

    2015-12-01

    Full Text Available We have studied the magnetic properties and the composition of cobalt ferrite single crystal films on SrTiO3 : Nb grown by infrared pulsed-laser deposition. Mössbauer spectra have been recorded from both the target used to grow the films and the films themselves. The Mössbauer spectra of the target taken at low temperatures show a strong dependence of the recoil free fraction of the octahedral sites with temperature. The films composition, with a coexistence of Co-enriched cobalt ferrite and magnetite, has been estimated assuming a similar ratio of the recoil free fractions of the films. X-ray absorption and x-ray magnetic circular dichroism measurements confirm the valence composition of the film and show ferromagnetic Fe-Co coupling in the films with a coercive field around 0.5 T at room temperature. The combination of these characterization techniques allows establishing the coherent structural and magnetic properties of this biphase system.

  18. Rock magnetic investigation of loess deposits in the Eastern Qingling Mountains (central China) and its implications for the environment of early humans

    Science.gov (United States)

    Wang, Xiaoyong; Lu, Huayu; Zhang, Weiguo; Hu, Pengxiang; Zhang, Hongyan; Han, Zhiyong; Wang, Shejiang; Li, Baoguo

    2016-11-01

    The Luonan Basin, located in the transitional zone between temperate and subtropical China, is an important locality for human evolution during the early to middle Pleistocene. The loess deposits in the Luonan Basin contain numerous in situ lithic artefacts; the deposits also constitute suitable material for dating the artefacts and are potentially useful for reconstructing the climatic fluctuations which is important for studying the adaptation and occupation of the area by early humans. We carried out a combined rock magnetic and geochemical investigation of a loess sequence from the Liuwan Palaeolithic site in the Luonan Basin. The results indicate a mixture of magnetic minerals, including magnetite/maghemite and hematite/goethite. Magnetic susceptibility was used as a palaeoclimate proxy on the Chinese Loess Plateau; however, its application to the Luonan Basin may be problematic because the provenance of the loess parent material, as well as the depositional environment, differs from that of the Chinese Loess Plateau. We found that rock magnetic parameters related to the grain size of magnetic minerals, such as SIRM/χ and χARM/SIRM, are better palaeoclimatic indicators than magnetic susceptibility. Overall, the magnetic results, together with the results of bulk grain-size and chemical index of alteration, indicate that the interglacial environment of early humans in Luonan Basin was warmer and more humid than the coeval environment of the Chinese Loess Plateau.

  19. High Yield Magnetic Nanoparticles Filled Multiwalled Carbon Nanotubes Using Pulsed Laser Deposition

    Science.gov (United States)

    2008-12-01

    plane magnetizations is the sharing produced by the demagnetizing field in the perpendicular direction. 1. INTRODUCTION Since its discovery in the...because of its large anisotropy and magnetostriction . The filling was carried out in high vacuum (2×10-7 Torr) where the polycrystalline CoFe2O4 was

  20. Analysis of the magnetic corrosion product deposits on a boiling water reactor cladding

    Energy Technology Data Exchange (ETDEWEB)

    Orlov, Andrey [Paul Scherrer Institut, Villigen (Switzerland); Degueldre, Claude, E-mail: claude.degueldre@psi.ch [Paul Scherrer Institut, Villigen (Switzerland); Kaufmann, Wilfried [Kernkraftwerk Leibstadt, Leibstadt (Switzerland)

    2013-01-15

    The buildup of corrosion product deposits (CRUD) on the fuel cladding of the boiling water reactor (BWR) before and after zinc injection has been investigated by applying local experimental analytical techniques. Under the BWR water chemistry conditions, Zn addition together with the presence of Ni and Mn induce the formation of (Zn,Ni,Mn)[Fe{sub 2}O{sub 4}] spinel solid solutions. X-ray absorption spectroscopy (XAS) revealed inversion ratios of cation distribution in spinels deposited from the solid solution. Based on this information, a two-site ferrite spinel solid solution model is proposed. Electron probe microanalysis (EPMA) and extended X-ray absorption fine structure (EXAFS) findings suggest the zinc-rich ferrite spinels formation on BWR fuel cladding mainly at lower pin. - Graphical Abstract: Analysis of spinels in corrosion product deposits on boiling water reactor fuel rod. Combining EPMA and XAFS results: schematic representation of the ferrite spinels in terms of the end members and their extent of inversion. Note that the ferrites are represented as a surface between the normal (upper plane, M[Fe{sub 2}]O{sub 4}) and the inverse (lower plane, Fe[MFe]O{sub 4}). Actual compositions red Black-Small-Square for the specimen at low elevation (810 mm), blue Black-Small-Square for the specimen at mid elevation (1800 mm). The results have an impact on the properties of the CRUD material. Highlights: Black-Right-Pointing-Pointer Buildup of corrosion product deposits on fuel claddings of a boiling water reactor (BWR) are investigated. Black-Right-Pointing-Pointer Under BWR water conditions, Zn addition with Ni and Mn induced formation of (Zn,Ni,Mn)[Fe{sub 2}O{sub 4}]. Black-Right-Pointing-Pointer X-Ray Adsorption Spectroscopy (XAS) revealed inversion of cations in spinel solid solutions. Black-Right-Pointing-Pointer Zinc-rich ferrite spinels are formed on BWR fuel cladding mainly at lower pin elevations.

  1. Electric and Magnetic Properties of Sputter Deposited BiFeO3 Films

    Directory of Open Access Journals (Sweden)

    N. Siadou

    2013-01-01

    Full Text Available Polycrystalline BiFeO3 films have been magnetron sputter deposited at room temperature and subsequently heat-treated ex situ at temperatures between 400 and 700°C. The deposition was done in pure Ar atmosphere, as the use of oxygen-argon mixture was found to lead to nonstoichiometric films due to resputtering effects. At a target-to-substrate distance d=2′′ the BiFeO3 structure can be obtained in larger range process gas pressures (2–7 mTorr but the films do not show a specific texture. At d=6′′ codeposition from BiFeO3 and Bi2O3 has been used. Films sputtered at low rate tend to grow with the (001 texture of the pseudo-cubic BiFeO3 structure. As the film structure does not depend on epitaxy similar results are obtained on different substrates. A result of the volatility of Bi, Bi rich oxide phases occur after heat treatment at high temperatures. A Bi2SiO5 impurity phase forms on the substrate side, and does not affect the properties of the main phase. Despite the deposition on amorphous silicon oxide substrate weak ferromagnetism phenomena and displaced loops have been observed at low temperatures showing that their origin is not strain. Ba, La, Ca, and Sr doping suppress the formation of impurity phases and leakage currents.

  2. Abnormal effect of substrate temperature on perpendicular magnetic anisotropy in sputter-deposited NdFeCo films on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Liuniu, E-mail: lntong@ahut.edu.cn [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Ma-An-Shan, 243002 Anhui (China); Deng, Peng [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Ma-An-Shan, 243002 Anhui (China); He, Xian-Mei [School of Mathematics and Physics, Anhui University of Technology, Ma-An-Shan, 243002 Anhui (China); Li, Tingting [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Ma-An-Shan, 243002 Anhui (China)

    2014-07-01

    The effect of substrate temperature on the perpendicular magnetic anisotropy (PMA) in sputtered NdFeCo films on Si(111) has been studied. A strong PMA is observed in the NdFeCo films deposited at 310 °C, while the room temperature (RT) deposited films show an in-plane dominated anisotropy. The microstructure reveals a stratified microstructure along film thickness due to diffusion occurring at Si(111)/NdFeCo interface of the films deposited at 310 °C. Nd{sub 2}(FeCo){sub 17} nano-crystals and Nd{sub 2}(FeCo){sub 14}Si{sub 3} and/or Nd{sub 6}(FeCo){sub 13}Si intermetallic compounds in nano-size appear in the films deposited at 310 °C, while the RT deposited NdFeCo films are in amorphous state. Annealing at 300 °C results in atomic relaxation and thus ordering of the stripe domains. The distinguishing dependence of the micro/magnetic structure and magnetic characteristics of the NdFeCo films on substrate temperature and annealing temperature is presented. It is concluded that the strong PMA is mainly from the magnetoelastic anisotropy caused by the induced interfacial stress due to the opposite thermal expansion behavior between the NdFeCo layer and Si-doped interfacial layer. - Highlights: • NdFeCo films were deposited on Si substrate at 25 and 310 °C, respectively. • The films deposited at 310 °C show a large perpendicular magnetic anisotropy (PMA). • The films deposited at 25 °C have an in-plane dominated anisotropy. • The PMA is mainly from the magnetoelastic anisotropy induced by interfacial stress.

  3. Temperature stability and microstructure of ultra-high intrinsic coercivity Nd-Fe-B magnets

    Institute of Scientific and Technical Information of China (English)

    HU Zhihua; CHENG Xinghua; ZHU Minggang; LI Wei; LIAN Fazeng

    2008-01-01

    The variations of intrinsic coercivity and remanence of sintered Nd-Fe-B magnets with ultra-high intrinsic coercivity were investigated.The results showed that the intrinsic coercivity and remanence declined simultaneously with increasing temperature,but the squareness of the magnets has hardly been changed.The temperature coefficients of remanence (α) and coercivity (β) for the magnets were calculated by two different methods,and the variations of the temperature coefficients and the microstructure of sintered Nd-Fe-B magnets were analyzed.The temperature coefficients of remanence (α) and coercivity (β) for the sintered magnets are very small,and the existence of free microstructure is necessary to obtain sintered Nd-Fe-B magnets with ultra-high intrinsic coercivity.

  4. Soft magnetic properties and high frequency characteristics of FeM (M = B, Hf, Zr) and pure Fe films fabricated by oblique deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chengcheng; Zhang, Chao; Wang, Fenglong; Zhao, Zhong; Jiang, Changjun; Xue, Desheng [Lanzhou University, Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou (China); Lanzhou University, Key Laboratory of Special Function Materials and Structure Design of Ministry of Education, Lanzhou (China)

    2015-09-15

    To improve the high-frequency properties of Fe-based thin films, doped and pure Fe thin films were obliquely deposited on Si (100) substrate by RF-magnetron sputtering. Vibrating sample magnetometer (VSM) measurements show obvious in-plane uniaxial magnetic anisotropy in both doped and pure Fe thin films, and enhancement effects of doping on Soft magnetic properties were also observed. Microwave permeability measurements indicate that the resonance frequency and permeability of pure Fe films are much larger than those of doped Fe thin films. Damping factors of Fe thin films deposited at different oblique angles were further investigated. (orig.)

  5. Globally Optimal Segmentation of Permanent-Magnet Systems

    DEFF Research Database (Denmark)

    Insinga, Andrea Roberto; Bjørk, Rasmus; Smith, Anders

    2016-01-01

    Permanent-magnet systems are widely used for generation of magnetic fields with specific properties. The reciprocity theorem, an energy-equivalence principle in magnetostatics, can be employed to calculate the optimal remanent flux density of the permanent-magnet system, given any objective...... functional that is linear in the magnetic field. This approach, however, yields a continuously varying remanent flux density, while in practical applications, magnetic assemblies are realized by combining uniformly magnetized segments. The problem of determining the optimal shape of each of these segments...

  6. Single molecule magnets on a gold surface: in situ electrospray deposition, x-ray absorption and photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Saywell, Alex; Britton, Andrew J; Beton, Peter H; O' Shea, James N [School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD (United Kingdom); Taleb, Nassiba; Del Carmen Gimenez-Lopez, Maria; Champness, Neil R, E-mail: james.oshea@nottingham.ac.uk [School of Chemistry, University of Nottingham, Nottingham, NG7 2RD (United Kingdom)

    2011-02-18

    Single molecule magnets based on the dodecamanganese (III, IV) cluster with two different types of ligand (acetate and benzoate) have been studied on the Au(111) surface. Due to the non-volatile and fragile nature of the molecules, we have used ultra-high vacuum electrospray deposition to produce a series of surface coverages from a fraction of a monolayer to multilayer films in both cases. Synchrotron radiation based electron spectroscopy has been used to study the adsorption of the molecules on the Au(111) surface and the effect that this has on the oxidation states of the manganese atoms in the core. In both cases, reduction of the core is observed due to the interaction with the surface, to essentially the same extent despite substantial differences in the size and nature of the ligand shell.

  7. Magnetic properties of permalloy films with different thicknesses deposited onto obliquely sputtered Cu underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaoyu; Sun, Xiaojun; Wang, Jianbo; Liu, Qingfang, E-mail: liuqf@lzu.edu.cn

    2015-03-01

    In this work, the influence of obliquely sputtered Cu underlayer of 10 nm on the magnetic properties of normally sputtered Permalloy thin films with different thicknesses from 10 nm to 150 nm has been investigated. It has been found that the samples with the Permalloy layer thickness ranging from 10 nm to 70 nm exhibit a good in-plane uniaxial magnetic anisotropy, and the increase of the film thickness leads to a decrease of the anisotropy field and the natural resonance frequency. The critical Permalloy layer thickness for stripe domain initiation of these films is about 80 nm, which is thinner than that of obliquely sputtered Permalloy thin films without an underlayer. The characteristic shapes of hysteresis loops which can be called ''transcritical'' are observed above the critical thickness. The condition and mechanism of appearing stripe domain structure were discussed and it has been found that the frequency response of permeability of the anisotropic films shows the characteristics of multi-peak resonance. - Highlights: • Py films were fabricated on obliquely sputtered Cu underlayers by RF magnetron sputtering. • Effects of Py layer thickness on anisotropy, ferromagnetic resonance frequency have been studied. • Samples with Py layer (<70 nm) show a good in-plane uniaxial magnetic anisotropy. • Samples with Py layer (>80 nm) show stripe domains and multi-peaks in permeability spectra.

  8. An approach for estimating the magnetization direction of magnetic anomalies

    Science.gov (United States)

    Li, Jinpeng; Zhang, Yingtang; Yin, Gang; Fan, Hongbo; Li, Zhining

    2017-02-01

    An approach for estimating the magnetization direction of magnetic anomalies in the presence of remanent magnetization through correlation between normalized source strength (NSS) and reduced-to-the-pole (RTP) is proposed. The observation region was divided into several calculation areas and the RTP field was transformed using different assumed values of the magnetization directions. Following this, the cross-correlation between NSS and RTP field was calculated, and it was found that the correct magnetization direction was that corresponding to the maximum cross-correlation value. The approach was tested on both simulated and real magnetic data. The results showed that the approach was effective in a variety of situations and considerably reduced the effect of remanent magnetization. Thus, the method using NSS and RTP is more effective compared to other methods such as using the total magnitude anomaly and RTP.

  9. Perpendicular magnetic anisotropy in Co{sub 3}Pt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, Christian; Makarov, Denys; Brombacher, Christoph; Neupert, Katja; Kehr, Mirko; Hoyer, Walter; Albrecht, Manfred [Chemnitz University of Technology (Germany). Institute of Physics

    2010-07-01

    Binary alloys of M{sub x}Pt{sub 1-x} (M=Fe and Co) prepared as thin films tend to show a strong perpendicular magnetic anisotropy (PMA), making them good candidates for magnetic recording media or sensoric devices. The magnetic response of M{sub x}Pt{sub 1-x} films can be strongly modified by the degree of composition, film thickness, deposition temperature, and nature of substrate. Thus, chemically disordered CoPt alloys with (111) texture exhibit an unexpected PMA related to an anisotropic short-range order (SRO) effect. Here we present an investigation of structural and magnetic properties of Co{sub 3}Pt alloy films in the thickness range from 5 to 20 nm. The magnetic layers were deposited using magnetron co-sputtering on thermally oxidized Si(100) wafers. Interestingly, even when deposited at room temperature, these films reveal the presence of a strong PMA (K{sub U} = 0.6 MJ/m{sup 3}) with a full remanence in the out-of-plane direction. Furthermore, owing to the high Co content, the alloy has a rather high value of saturation magnetization of about 0.8 T. To access the structural properties of the alloy, a X-ray diffraction study was carried out. However, no superstructure peaks which might be attributed to a chemical long range order have been observed indicating that SRO is the origin for the PMA.

  10. Dependence of ferroelectric and magnetic properties on measuring temperatures for polycrystalline BiFeO(3) films.

    Science.gov (United States)

    Naganuma, H; Inoue, Y; Okamura, S

    2008-05-01

    A multiferroic BiFeO(3) film was fabricated on a Pt/Ti/SiO(3)/Si(100) substrate by a chemical solution deposition (CSD) method, and this was followed by postdeposition annealing at 923 K for 10 min in air. X-ray diffraction analysis indicated the formation of the polycrystalline single phase of the BiFeO(3) film. A high remanent polarization of 89 microC/cm(2) was observed at 90 K together with a relatively low electric coercive field of 0.32 MV/cm, although the ferroelectric hysteresis loops could not be observed at room temperature due to a high leakage current density. The temperature dependence of the ferroelectric hysteresis loops indicated that these hysteresis loops lose their shape above 165 K, and the nominal remanent polarization drastically increased due to the leakage current. Magnetic measurements indicated that the saturation magnetization was less than 1 emu/cm(3) at room temperature and increased to approximately 2 emu/cm(3) at 100 K, although the spontaneous magnetization could not appear. The magnetization curves of polycrystalline BiFeO3 film were nonlinear at both temperatures, which is different with BiFeO3 single crystal.

  11. Regional Crustal Structures and Their Relationship to the Distribution of Ore Deposits in the Western United States, Based on Magnetic and Gravity Data

    Science.gov (United States)

    Hildenbrand, T.G.; Berger, B.; Jachens, R.C.; Ludington, S.

    2000-01-01

    Upgraded gravity and magnetic databases and associated filtered-anomaly maps of western United States define regional crustal fractures or faults that may have guided the emplacement of plutonic rocks and large metallic ore deposits. Fractures, igneous intrusions, and hydrothermal circulation tend to be localized along boundaries of crustal blocks, with geophysical expressions that are enhanced here by wavelength filtering. In particular, we explore the utility of regional gravity and magnetic data to aid in understanding the distribution of large Mesozoic and Cenozoic ore deposits, primarily epithermal and porphyry precious and base metal deposits and sediment-hosted gold deposits in the western United States cordillera. On the broadest scale, most ore deposits lie within areas characterized by low magnetic properties. The Mesozoic Mother Lodge gold belt displays characteristic geophysical signatures (regional gravity high, regional low-to-moderate background magnetic field anomaly, and long curvilinear magnetic highs) that might serve as an exploration guide. Geophysical lineaments characterize the Idaho-Montana porphyry belt and the La Caridad-Mineral Park belt (from northern Mexico to western Arizona) and thus indicate a deep-seated control for these mineral belts. Large metal accumulations represented by the giant Bingham porphyry copper and the Butte polymetallic vein and porphyry copper systems lie at intersections of several geophysical lineaments. At a more local scale, geophysical data define deep-rooted faults and magmatic zones that correspond to patterns of epithermal precious metal deposits in western and northern Nevada. Of particular interest is an interpreted dense crustal block with a shape that resembles the elliptical deposit pattern partly formed by the Carlin trend and the Battle Mountain-Eureka mineral belt. We support previous studies, which on a local scale, conclude that structural elements work together to localize mineral deposits within

  12. The enigma of lunar magnetism

    Science.gov (United States)

    Hood, L. L.

    1981-01-01

    Current understandings of the nature and probable origin of lunar magnetism are surveyed. Results of examinations of returned lunar samples are discussed which reveal the main carrier of the observed natural remanent magnetization to be iron, occasionally alloyed with nickel and cobalt, but do not distinguish between thermoremanent and shock remanent origins, and surface magnetometer data is presented, which indicates small-scale magnetic fields with a wide range of field intensities implying localized, near-surface sources. A detailed examination is presented of orbital magnetometer and charged particle data concerning the geologic nature and origin of magnetic anomaly sources and the directional properties of the magnetization, which exhibit a random distribution except for a depletion in the north-south direction. A lunar magnetization survey with global coverage provided by a polar orbiting satellite is suggested as a means of placing stronger constraints on the origin of lunar crustal magnetization.

  13. Microstructure and Magnetic Properties of NdFeB Films through Nd Surface Diffusion Process

    Directory of Open Access Journals (Sweden)

    Wenfeng Liu

    2017-01-01

    Full Text Available Ta/Nd/NdFeB/Nd/Ta films were deposited by magnetron sputtering on Si (100 substrates and subsequently annealed for 30 min at 923 K in vacuum. It was found that the microstructure and magnetic properties of Ta/Nd/NdFeB/Nd/Ta films strongly depend on the NdFeB layer thickness. With NdFeB layer thickness increasing, both the grain size and the strain firstly reduce and then increase. When NdFeB layer thickness is 750 nm, the strain reaches the minimum value. Meanwhile, both the in-plane and perpendicular coercivities firstly drastically increase and then slowly decrease with NdFeB layer thickness increasing. The highest in-plane and perpendicular coercivities can be obtained at NdFeB layer thickness of 750 nm, which are 21.2 kOe and 19.5 kOe, respectively. In addition, the high remanence ratio (remanent magnetization/saturation magnetization of 0.87 can also be achieved in Ta/Nd/NdFeB (750 nm/Nd/Ta film.

  14. Design of Remanence Contactor and Its Energy Saving Control Module%剩磁接触器及其节能控制模块的设计

    Institute of Scientific and Technical Information of China (English)

    韩光熙

    2014-01-01

    针对剩磁接触器设计了节能控制模块,同时探讨了将普通接触器经磁系统改造成剩磁接触器的问题。详细阐述了剩磁接触器各个工作阶段,节能控制模块的工作原理,并具体分析了普通接触器磁系统改造中钢材的选择。%This article explained how the remanence contactor works with the support of its control module. Then it expounded the operational principle of the control module during different working time periods.Lastly the article suggests how to select the materials of magnetic system.

  15. Control of the magnetic properties of LaMnO3 epitaxial thin films grown by Pulsed Laser Deposition

    Science.gov (United States)

    Martinez, Benjamin; Roqueta, Jaume; Pomar, Alberto; Balcells, Lluis; Frontera, Carlos; Konstantinovic, Zorica; Sandiumenge, Felip; Santiso, Jose; Advanced materials characterization Team; Thin films growth Team

    2015-03-01

    LaMnO3 (LMO), the parent compound of colossal magnetoresistance based manganites has gained renewed attention as a building block in heterostructures with unexpected properties. In its bulk phase, stoichiometric LMO is an A-type antiferromagnetic (AFM) insulator (TN = 140K) with orthorhombic structure that easily accommodate an oxygen excess by generating cationic (La or Mn) vacancies. As a result, a fraction of Mn 3+ changes to Mn 4+ leading to a double-exchange mediated ferromagnetic (FM) behavior. In thin films the AFM phase has been elusive up to now and thin films with FM ordering are usually reported. In this work, we have systematically studied the growth process of LaMnO3 thin films by pulsed laser deposition on SrTiO3 (001) substrates under different oxygen partial pressures (PO2) . A close correlation between the structure (explored by XRD) and the magnetic properties (SQUID measurements) of the films with PO2 has been identified. At high PO2 FM behavior is observed. In contrast, at very low PO2, the results obtained for unit cell volume (close to stoichiometric bulk values) and magnetic moment (0.2 μB/Mn) strongly indicate antiferromagnetic ordering. We acknowledge financial support from the Spanish MINECO (MAT2012-33207).

  16. Anomalous magnetic Properties of an iron film System deposited on fracture surfaces of α-Al2O3 ceramics

    Institute of Scientific and Technical Information of China (English)

    Jiao Zhi-Wei; Chen Miao-Gen; Jiang Wei-Di; Feng Chun-Mu; Ye Gao-Xiang

    2008-01-01

    An iron film percolation system is fabricated by vapour-phase deposition on fracture surfaces of α-Al2O3 ceramics.The zero-field-cooled(ZFC)and field-cooled(FC)magnetization measurement reveals that the magnetic phase of the film samples evolve from a high-temperature ferromagnetic state to a low-temperature spin-glass-fike state.which is also demonstrated by the temperature-dependent ac susceptibility of the iron films.The temperature dependence of the exchange bias field He of the iron film exhibits a minimum peak around the temperature T=5 K,which is independent of the magnitude of the cooling field Hcf.However,for T>10 K,(1)He is always negative when Hcf=2 kOe and(2) for Hcf=20kOe(1Oe≈80A/m),He changes from negative to positive values as T increases.Our experimental results show that the anomalous hysteresis properties mainly result from the oxide surfaces of the films with spin-glass-like phase.

  17. Epitaxial wurtzite-MgZnO barrier based magnetic tunnel junctions deposited on a metallic ferromagnetic electrode

    Energy Technology Data Exchange (ETDEWEB)

    Belmoubarik, M., E-mail: bmm-dhr@ecei.tohoku.ac.jp; Al-Mahdawi, M.; Sato, H.; Nozaki, T.; Sahashi, M. [Department of Electronic Engineering, Tohoku University, Sendai 890-8579 (Japan)

    2015-06-22

    An epitaxial wurtzite (WZ) Mg{sub 0.23}Zn{sub 0.77}O barrier based magnetic tunnel junction (MTJ), with electrode-barrier structure of Co{sub 0.30}Pt{sub 0.70} (111)/Mg{sub 0.23}Zn{sub 0.77}O (0001)/Co (0001), was fabricated. The good crystallinity and tunneling properties were experimentally confirmed. Electrical and magnetic investigations demonstrated its high resistance-area product of 1.05 MΩ μm{sup 2}, a maximum tunneling magneto-resistance (TMR) of 35.5%, and the existence of localized states within the tunneling barrier producing TMR rapid decrease and oscillation when increasing the applied bias voltage. The TMR value almost vanished at 200 K, which was attributed to the induced moment and strong spin-orbit coupling in Pt atoms at the Co{sub 0.30}Pt{sub 0.70}/Mg{sub 0.23}Zn{sub 0.77}O interface. Owing to the ferroelectric behavior in WZ-MgZnO materials, the fabrication of WZ-MgZnO barrier based MTJs deposited on a metallic ferromagnetic electrode will open routes for electrically controllable non-volatile devices that are compatible with CMOS technology.

  18. Sub-nanometer atomic layer deposition for spintronics in magnetic tunnel junctions based on graphene spin-filtering membranes.

    Science.gov (United States)

    Martin, Marie-Blandine; Dlubak, Bruno; Weatherup, Robert S; Yang, Heejun; Deranlot, Cyrile; Bouzehouane, Karim; Petroff, Frédéric; Anane, Abdelmadjid; Hofmann, Stephan; Robertson, John; Fert, Albert; Seneor, Pierre

    2014-08-26

    We report on the successful integration of low-cost, conformal, and versatile atomic layer deposited (ALD) dielectric in Ni–Al2O3–Co magnetic tunnel junctions (MTJs) where the Ni is coated with a spin-filtering graphene membrane. The ALD tunnel barriers, as thin as 0.6 nm, are grown layer-by-layer in a simple, low-vacuum, ozone-based process, which yields high-quality electron-transport barriers as revealed by tunneling characterization. Even under these relaxed conditions, including air exposure of the interfaces, a significant tunnel magnetoresistance is measured highlighting the robustness of the process. The spin-filtering effect of graphene is enhanced, leading to an almost fully inversed spin polarization for the Ni electrode of −42%. This unlocks the potential of ALD for spintronics with conformal, layer-by-layer control of tunnel barriers in magnetic tunnel junctions toward low-cost fabrication and down-scaling of tunnel resistances.

  19. Bismuth iron oxide thin films using atomic layer deposition of alternating bismuth oxide and iron oxide layers

    Energy Technology Data Exchange (ETDEWEB)

    Puttaswamy, Manjunath; Vehkamäki, Marko [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Kukli, Kaupo, E-mail: kaupo.kukli@helsinki.fi [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); University of Tartu, Institute of Physics, W. Ostwald 1, EE-50411 Tartu (Estonia); Dimri, Mukesh Chandra [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Kemell, Marianna; Hatanpää, Timo; Heikkilä, Mikko J. [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Mizohata, Kenichiro [University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 Helsinki (Finland); Stern, Raivo [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Ritala, Mikko; Leskelä, Markku [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland)

    2016-07-29

    Bismuth iron oxide films with varying contributions from Fe{sub 2}O{sub 3} or Bi{sub 2}O{sub 3} were prepared using atomic layer deposition. Bismuth (III) 2,3-dimethyl-2-butoxide, was used as the bismuth source, iron(III) tert-butoxide as the iron source and water vapor as the oxygen source. The films were deposited as stacks of alternate Bi{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} layers. Films grown at 140 °C to the thickness of 200–220 nm were amorphous, but crystallized upon post-deposition annealing at 500 °C in nitrogen. Annealing of films with intermittent bismuth and iron oxide layers grown to different thicknesses influenced their surface morphology, crystal structure, composition, electrical and magnetic properties. Implications of multiferroic performance were recognized in the films with the remanent charge polarization varying from 1 to 5 μC/cm{sup 2} and magnetic coercivity varying from a few up to 8000 A/m. - Highlights: • Bismuth iron oxide thin films were grown by atomic layer deposition at 140 °C. • The major phase formed in the films upon annealing at 500 °C was BiFeO{sub 3}. • BiFeO{sub 3} films and films containing excess Bi favored electrical charge polarization. • Slight excess of iron oxide enhanced saturative magnetization behavior.

  20. Dating of the Reocin MVT Deposit, Spain, by Paleomagnetism

    Science.gov (United States)

    Symons, D. T.; Lewchuk, M. T.; Kawasaki, K.; Velasco, F.; Leach, D. L.

    2009-05-01

    Located in the Basque-Cantabrian basin of northernmost Spain, the Reocin mine exploited one of the worldfs largest known Mississippi Valley-type (MVT) deposits (˜62 Mt at 8.7% Zn and 1.0% Pb) for >100 years. The sphalerite-galena and ferroan dolomite mineralization is in a karst system in 116±1 Ma Urgonian carbonates along the southeastern limb of the Santillana syncline that was formed by late Oligocene and mid Miocene pulses of the Pyrenean Orogeny. Paleomagnetic results from 22 sites (274 specimens) in ore-grade and marginal mineralization isolated a post-folding mid Miocene characteristic remanence (ChRM) direction. Mineral magnetics tests on mineralization, Zn concentrate and tailings show that the ChRM is carried both in sphalerite and ferroan dolomite by pyrrhotite mainly with minor magnetite. We suggest that the deposit was formed in the mid Miocene by fluids flowing from the Pyrenean highlands, ˜50 km SSW of Reocin, that scavenged the metals enroute to Reocin from the Paleozoic basement and/or Mesozoic clastic sediments below the deposit that were derived from the basement.

  1. Additive Manufacturing of Near-net Shaped Permanent Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Paranthaman, M Parans [ORNL

    2016-07-26

    The technical objective of this technical collaboration phase I proposal is to fabricate near net-shaped permanent magnets using alloy powders utilizing direct metal deposition technologies at the ORNL MDF. Direct Manufacturing using the POM laser system was used to consolidate Nd2Fe14B (NdFeB) magnet powders into near net-shape parts efficiently and with virtually no wasted material as part of the feasibility study. We fabricated builds based on spherical NdFeB magnet particles. The results show that despite the ability to fabricate highly reactive materials in the laser deposition process, the magnetic coercivity and remanence of the NdFeB hard magnets is significantly reduced. X-ray powder diffraction in conjunction with electron microscopy showed that the material experienced a primary Nd2Fe17Bx solidification due to the undercooling effect (>60K). Consequently the presence of alpha iron phase resulted in deterioration of the build properties. Further optimization of the processing parameters is needed to maintain the Nd2Fe14B phase during fabrication.

  2. Co nanoparticles induced resistive switching and magnetism for the electrochemically deposited polypyrrole composite films.

    Science.gov (United States)

    Xu, Zedong; Gao, Min; Yu, Lina; Lu, Liying; Xu, Xiaoguang; Jiang, Yong

    2014-10-22

    The resistive switching behavior of Co-nanoparticle-dispersed polypyrrole (PPy) composite films is studied. A novel design method for resistive random access memory (ReRAM) is proposed. The conducting polymer films with metal nanocrystal (NC)-dispersed carbon chains induce the spontaneous oxidization of the conducting polymer at the surface. The resistive switching behavior is achieved by an electric field controlling the oxygen ion mobility between the metal electrode and the conducting polymer film to realize the mutual transition between intrinsic conduction (low resistive state) and oxidized layer conduction (high resistive state). Furthermore, the formation process of intrinsic conductive paths can be effectively controlled in the conducting polymer ReRAM using metal NCs in films because the inner metal NCs induce electric field lines converging around them and the intensity of the electric field at the tip of NCs can greatly exceed that of the other region. Metal NCs can also bring new characteristics for ReRAM, such as magnetism by dispersing magnetic metal NCs in polymer, to obtain multifunctional electronic devices or meet some special purpose in future applications. Our works will enrich the application fields of the electromagnetic PPy composite films and present a novel material for ReRAM devices.

  3. Structure and magnetic properties of columnar Fe-N thin films deposited by direct current magnetron sputtering

    Institute of Scientific and Technical Information of China (English)

    JIA Hui; WANG Xin; PANG Shao-ping; ZHENG Wei-tao; LONG Bei-hong; LI Bo

    2009-01-01

    Columnar Fe-N thin films with thickness ranging from 30 to 150 nm were deposited by direct current magnetron sputtering using an Ar/N2 gas mixture (V(N2)/V(N2+Ar)=5%) on corning glass substrates. The structure, surface morphology and magnetic properties were investigated using X-ray diffractometry(XRD), scanning electron microscopy, atomic force microscopy, transmission electron microscopy(TEM) and superconducting quantum interference magnetometry. XRD investigation shows that Fe-N films exhibit amorphous-like structures; however, TEM measurements indicate the synthesis of mixture phases of α-Fe+ζ-Fe2N+ε-Fe3N in these films. The magnetic anisotropy and coercivity of Fe-N thin films exhibit strong dependence on the film growth behavior and surface morphology. With increasing the height of Fe-N films with column structures, the coercivity increases from 7.96 kA/m to 22.28 kA/m in the direction parallel to the film surface. In perpendicular direction the coercivity only increases slightly from 39.79 kA/m to 43.77 kA/m. However, the values of anisotropy field increase from 0.79×106 to 1.44×106 A/m, which is mainly attributed to the shape anisotropy of elongated columns due to the fact that the difference of magneto-crystalline anisotropy among these Fe-N films is small. The saturation magnetizations of Fe-N films vary with increasing film thickness from 23.5 to 85.1 A-m2/kg.

  4. Magnetic biomonitoring of roadside pollution in the restricted Midagahara area of Mt. Tateyama, Toyama, Japan.

    Science.gov (United States)

    Kawasaki, Kazuo; Horikawa, Keiji; Sakai, Hideo

    2017-03-07

    Magnetic biomonitoring techniques and in situ topsoil magnetic susceptibility measurements have been shown to be rapid, cost-effective, and useful methods for investigating roadside pollution. However, combustible vegetation in samples makes it very difficult to use them in high-temperature magnetic experiments although the thermal alteration of spontaneous magnetization is a fundamental magnetic property and can be used to identify reliably the magnetic minerals. Here, we report the first magnetic biomonitoring results of dust deposited on plant leaves along the Tateyama-Kurobe Alpine route at the highly protected Midagahara wetland areas of Mt. Tateyama in Toyama, Japan. In-field magnetic susceptibility from 15 sites (161 points) shows higher susceptibilities near the roadside. Dust deposited on the leaves of Sasa kurilensis, or dwarf bamboo, has been wiped off at 12 sites (64 samples) with a commercial ethanol wipe sheet or silica wool damped in ethanol and subjected to rock magnetic analyses. Thermomagnetic remanence curves and low-temperature behaviors for samples collected near the roadside using silica wool show clearly that the main magnetic mineral in the dust is partially oxidized magnetite. Further, detailed rock magnetic analyses and elemental analyses of leaves in the study area indicate that (a) the magnetic mineralogy on leaves' surface is consistent throughout the study area and (b) higher saturation isothermal remanent magnetization intensities as well as higher concentrations of Pb, Fe, Cr, and Y are observed near the roadside, i.e., the closer to the roadside, the more anthropogenic materials, including partially oxidized magnetite, are present. Also, microscopic observations show the lack of spherical grains, indicating that dust on the roadside leaves is derived from passing vehicle rather than industrial process. Both rock magnetic and geochemical results show that S. kurilensis would be an excellent candidate for investigating air pollution

  5. Electric-field induced strain modulation of magnetization in Fe-Ga/Pb(Mg{sub 1/3}Nb{sub 2/3})-PbTiO{sub 3} magnetoelectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yue, E-mail: yuezhang@vt.edu; Wang, Zhiguang; Wang, Yaojin; Luo, Chengtao; Li, Jiefang; Viehland, Dwight [Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2014-02-28

    Magnetostrictive Fe-Ga thin layers were deposited on 〈110〉-oriented Pb(Mg{sub 1/3}Nb{sub 2/3})-30%PbTiO{sub 3} (PMN-30%PT) substrates by pulsed laser deposition. The as-prepared heterostructures showed columnar arrays aligned in the out-of-plane direction. Transmission electron microscopy revealed nanocrystalline regions within the columnar arrays of the Fe-Ga film. The heterostructure exhibited a strong converse magnetoelectric coupling effect of up to 4.55 × 10{sup −7} s m{sup −1}, as well as an electric field tunability of the in-plane magnetic anisotropy. Furthermore, the remanent magnetization states of the Fe-Ga films can be reversibly and irreversibly changed by external electric fields, suggesting a promising and robust application in magnetic random access memories and spintronics.

  6. Identification and characterization of tsunami deposits off southeast coast of India from the 2004 Indian Ocean tsunami: Rock magnetic and geochemical approach.

    Digital Repository Service at National Institute of Oceanography (India)

    Veerasingam, S.; Venkatachalapathy, R.; Basavaiah, N.; Ramkumar, T.; Venkatramanan, S.; Deenadayalan, K.

    , mineralogical, geochemical and rock-magnetic investigations showed that the tsunami deposit is featured by relative enrichment in sand, quartz, feldspar, carbonate, SiO2, TiO2, K2O and CaO and by a depletion in clay and iron...

  7. Food intake and fuel deposition in a migratory bird is affected by multiple as well as single-step changes in the magnetic field.

    Science.gov (United States)

    Henshaw, Ian; Fransson, Thord; Jakobsson, Sven; Lind, Johan; Vallin, Adrian; Kullberg, Cecilia

    2008-03-01

    Recent studies have shown that migratory thrush nightingales (Luscinia luscinia) experimentally treated with multiple changes of the magnetic field simulating a journey to their target stopover area in northern Egypt, increased fuel deposition as expected in preparation to cross the Sahara desert. To investigate the significance of food intake on the body mass changes observed, in the work described here we analysed food intake of the nightingales under study in those earlier experiments. Furthermore, to study whether a single change in the magnetic field directly to northern Egypt is sufficient to provide information for fuelling decisions, we performed a new experiment, exposing thrush nightingales trapped in Sweden, directly to a magnetic field of northern Egypt. Our results show that an experimentally induced magnetic field of northern Egypt, close to the barrier crossing, triggers the same response in fuel deposition as experiments with multiple changes of the magnetic field simulating a migratory journey from Sweden to Egypt, suggesting that migratory birds do not require successive changes in field parameters to incorporate magnetic information into their migratory program. Furthermore, irrespective of experimental set up (single or multiple changes of the magnetic field parameters) increase in food intake seems to be the major reason for the observed increase in fuelling rate compared with control birds, suggesting that geomagnetic information might trigger hormonal changes in migratory birds enabling appropriate fuelling behaviour during migration.

  8. Unusually large magnetic anisotropy in electrochemically deposited Co-rich Co-Pt films.

    Science.gov (United States)

    Sirtori, V; Cavallotti, P L; Rognoni, R; Xu, X; Zangari, G; Fratesi, G; Trioni, M I; Bernasconi, M

    2011-06-01

    Co-rich Co-Pt films grown by electrodeposition from an amino-nitrite/citrate/glycine electrolyte onto Au(111) substrates apparently grow with a hexagonal structure, with its c-axis directed perpendicular to the surface. The films exhibit a perpendicular magnetic anisotropy (MCA) of the same order of magnitude as the shape anisotropy. Experimental estimates of the MCA result in a higher anisotropy than that reported for bulk materials of the same composition, but similar to values measured in films grown by vacuum methods at relatively high temperature, which partly consist of a high anisotropy, metastable orthorhombic Pmm2 phase. Comparison of valence band X-ray photoelectron spectroscopy measurements on electrodeposited films with density functional theory simulations of the electronic structure of the various reported Co(3)Pt structures support the notion that the films may consist of a mixture of the hexagonal and the Pmm2 structure.

  9. Identification and characterization of tsunami deposits off southeast coast of India from the 2004 Indian Ocean tsunami: Rock magnetic and geochemical approach

    Science.gov (United States)

    Veerasingam, S.; Venkatachalapathy, R.; Basavaiah, N.; Ramkumar, T.; Venkatramanan, S.; Deenadayalan, K.

    2014-06-01

    The December 2004 Indian Ocean Tsunami (IOT) had a major impact on the geomorphology and sedimentology of the east coast of India. Estimation of the magnitude of the tsunami from its deposits is a challenging topic to be developed in studies on tsunami hazard assessment. Two core sediments (C1 and C2) from Nagapattinam, southeast coast of India were subjected to textural, mineral, geochemical and rock-magnetic measurements. In both cores, three zones (zone I, II and III) have been distinguished based on mineralogical, geochemical and magnetic data. Zone II is featured by peculiar rock-magnetic, textural, mineralogical and geochemical signatures in both sediment cores that we interpret to correspond to the 2004 IOT deposit. Textural, mineralogical, geochemical and rock-magnetic investigations showed that the tsunami deposit is featured by relative enrichment in sand, quartz, feldspar, carbonate, SiO 2, TiO 2, K 2O and CaO and by a depletion in clay and iron oxides. These results point to a dilution of reworked ferromagnetic particles into a huge volume of paramagnetic materials, similar to what has been described in other nearshore tsunami deposits (Font et al. 2010). Correlation analysis elucidated the relationships among the textural, mineral, geochemical and magnetic parameters, and suggests that most of the quartz-rich coarse sediments have been transported offshore by the tsunami wave. These results agreed well with the previously published numerical model of tsunami induced sediment transport off southeast coast of India and can be used for future comparative studies on tsunami deposits.

  10. Magnetic fields and uniformity of radio frequency power deposition in low-frequency inductively coupled plasmas with crossed internal oscillating currents

    DEFF Research Database (Denmark)

    Tsakadze, Erekle; Ostrikov, K.N.; Tsakadze, Z.L.

    2004-01-01

    and equidistant copper litz wires in quartz enclosures and generates three magnetic (H-z, H-r, and H-phi) and two electric (E-phi and E-r) field components at the fundamental frequency. The measurements have been performed in rarefied and dense plasmas generated in the electrostatic (E) and electromagnetic (H......) discharge modes using two miniature magnetic probes. It is shown that the radial uniformity and depth of the rf power deposition can be improved as compared with conventional sources of inductively coupled plasmas with external flat spiral ("pancake") antennas. Relatively deeper rf power deposition...... in the plasma source results in more uniform profiles of the optical emission intensity, which indicates on the improvement of the plasma uniformity over large chamber volumes. The results of the numerical modeling of the radial magnetic field profiles are found in a reasonable agreement with the experimental...

  11. Interactive 3D forward modeling of total field surface and three-component borehole magnetic data for the Daye iron-ore deposit (Central China)

    Science.gov (United States)

    Yang, Yushan; Li, Yuanyuan; Liu, Tianyou; Zhan, Yinglin; Feng, Jie

    2011-10-01

    The ground magnetic response of deep ore bodies in the Daye iron-ore deposit is relatively weak, and sometimes concealed by the strong magnetic background of shallower sources. Apart from the low-quality ground magnetic data, another critical problem for reconstructing the deep skarn-type ore bodies is developing a versatile inversion scheme that can simultaneously resolve 3D sources with arbitrary shapes. In this case, we resort to interactive 3D forward modeling solution with the joint use of two data sets-total field surface and three-component borehole magnetic data. Joint inversion of the two data sets is expected to help resolve the ambiguity associated with either data set and greatly reduces the nonuniqueness of the magnetic inversion. Such nonuniqueness is especially severe when a 3-D distribution of magnetic susceptibility, instead of a simple body, is sought from the inversion. In this paper, we calculate the magnetic field on the surface and in the borehole caused by 3D arbitrarily-shaped bodies with the triple integral method. The complex 3D magnetic sources having arbitrary shapes are constructed with cross-sections, termination points and facets in our visualization technology. We specify, interactively and in a user-friendly environment, the outline of the sources in terms of geometric elements and their magnetic parameters. The method automatically fits the observations within a prescribed precision. If dissatisfied, the user can redefine the model parameters and proceed to a new inversion. The method's ability to interpret a complicated 3D geologic environment is demonstrated on synthetic models and real data profiles in the Daye iron-ore deposit in central China. The interactive forward modeling results in all tests demonstrate a good correlation of estimated magnetic sources with corresponding known geologic features.

  12. 3D Inversion of Magnetic Data through Wavelet based Regularization Method

    Directory of Open Access Journals (Sweden)

    Maysam Abedi

    2015-06-01

    Full Text Available This study deals with the 3D recovering of magnetic susceptibility model by incorporating the sparsity-based constraints in the inversion algorithm. For this purpose, the area under prospect was divided into a large number of rectangular prisms in a mesh with unknown susceptibilities. Tikhonov cost functions with two sparsity functions were used to recover the smooth parts as well as the sharp boundaries of model parameters. A pre-selected basis namely wavelet can recover the region of smooth behaviour of susceptibility distribution while Haar or finite-difference (FD domains yield a solution with rough boundaries. Therefore, a regularizer function which can benefit from the advantages of both wavelets and Haar/FD operators in representation of the 3D magnetic susceptibility distributionwas chosen as a candidate for modeling magnetic anomalies. The optimum wavelet and parameter β which controls the weight of the two sparsifying operators were also considered. The algorithm assumed that there was no remanent magnetization and observed that magnetometry data represent only induced magnetization effect. The proposed approach is applied to a noise-corrupted synthetic data in order to demonstrate its suitability for 3D inversion of magnetic data. On obtaining satisfactory results, a case study pertaining to the ground based measurement of magnetic anomaly over a porphyry-Cu deposit located in Kerman providence of Iran. Now Chun deposit was presented to be 3D inverted. The low susceptibility in the constructed model coincides with the known location of copper ore mineralization.

  13. The annealing temperature dependences of microstructures and magnetic properties in electro-chemical deposited CoNiFe thin films

    Science.gov (United States)

    Suharyadi, Edi; Riyanto, Agus; Abraha, Kamsul

    2016-04-01

    CoNiFe thin films with various compositions had been successfully fabricated using electro-chemical deposition method. The crystal structure of Co65Ni15Fe20, Co62Ni15Fe23, and Co55Ni15Fe30 thin films was fcc, bcc-fcc mix, and bcc, respectively. The difference crystal structure results the difference in magnetic properties. The saturation magnetic flux density (Bs) of Co65Ni15Fe20, Co62Ni15Fe23, and Co55Ni15Fe30 thin films was 1.89 T, 1.93 T, and 2.05 T, respectively. An optimal annealing temperature was determined for controlling the microstructure and magnetic properties of CoNiFe thin films. Depending on annealing temperature, the ratio of bcc and fcc structure varied without changing the film composition. By annealing at temperature of T ≥ 350°C, the intensity ratio of X-ray diffraction peaks for bcc(110) to fcc(111) increased. The increase of phase ratio of bcc(110) to fcc(111) caused the increase of Bs, from 1.89 T to 1.95 T. Coercivity (Hc) also increased after annealing, from 2.6 Oe to 18.6 Oe for fcc phase thin films, from 2.0 Oe to 12.0 Oe for fcc-bcc mix phase thin films, and 7.8 Oe to 8 Oe for bcc phase thin films. The changing crystal structures during annealing process indicated that the thermal treatment at high temperature cause the changing crystallinity and atomic displacement. The TEM bright-field images with corresponding selected-area electron diffraction (SAED) patterns showed that there are strongly effects of thermal annealing on the size of fcc and bcc phase crystalline grain as described by size of individual spot and discontinuous rings. The size of crystalline grains increased by thermal annealing. The evolution of bcc and fcc structures of CoNiFe during annealing is though to be responsible for the change of magnetic properties.

  14. Magnetic and Electric Properties of Amorphous Co40Fe40B20 Thin Films

    Directory of Open Access Journals (Sweden)

    Yuan-Tsung Chen

    2012-01-01

    Full Text Available C40Fe40B20 was deposited on a glass substrate to a thickness (tf of between 100 Å and 500 Å. X-ray diffraction patterns (XRD indicate that C40Fe40B20 films are in an amorphous state. The plane-view microstructures and grain size distributions of CoFeB thin films are observed under a high-resolution transmission electron microscope (HRTEM. The thicker CoFeB films have larger grain size distribution than thinner CoFeB films. The saturation magnetization (Ms exhibits a size effect, meaning that Ms increases as tf increases. The magnetic remanence magnetization (Mr of CoFeB thin films are sensitive to thinner CoFeB films, and the refined grain size of thinner CoFeB films can induce ferromagnetic stronger spin exchange-coupling behavior than thicker CoFeB films, resulting in higher remanence. The highest magnetic squareness ratio (Mr/Ms of the CoFeB films occurs at thickness of 100 Å, suggesting the 100 Å of the as-deposited CoFeB film is suitable for magnetic memory application. These results also demonstrate that coercivity (Hc is increased by an increase in the width of the distribution of grain sizes. The electrical resistivity (ρ of such a film is typically higher than normally exceeding 100 μΩ cm, revealing that the amorphous phase dominates. These results are consistent with the XRD results.

  15. Microstructure and magnetic properties of FePt/MgO multilayers deposited by RF magnetron sputtering

    Institute of Scientific and Technical Information of China (English)

    Xiaoli Li; Fang Wang; Fengxian Jiang; Xiaohong Xu; Haishun Wu

    2008-01-01

    FePt (50 rim) and [FePt(a nm)/MgO(b nm)]5/glass (a=1, 2, 3; b=1, 2, 3)films Were prepared by radio frequency (RF) magnetron sputtering technique, and then were annealed at 600℃ for 30 min. The effect of MgO layer thickness on the structures and magnetic properties of the FePt/MgO multilayers was investigated. The coercivities and inter-grain interactions of the FePt/MgO films were decreased, yet the degree of (001) texturing drastically increased with the increase in MgO layer thickness when the FePt layer thickness was fixed. Thus, the FePt/MgO films with appropriate coercivities, high perpendicular anisotropy, and weak inter- grain interactions were obtained by controlling the MgO layer thickness. Overall, these results indicate that the FePt/MgO nanos- tructured films are promising candidates for future high-density perpendicular recording media. C 2008 University of Science and Technology Beijing. All fights reserved.

  16. Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer

    Directory of Open Access Journals (Sweden)

    Chun Dong

    2011-01-01

    Full Text Available Abstract A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe and high magnetization (900–1,000 emu/cm3 characteristic of L10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

  17. Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer.

    Science.gov (United States)

    Kim, Hyunsu; Noh, Jin-Seo; Roh, Jong Wook; Chun, Dong Won; Kim, Sungman; Jung, Sang Hyun; Kang, Ho Kwan; Jeong, Won Yong; Lee, Wooyoung

    2011-12-01

    A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe) and high magnetization (900-1,000 emu/cm(3)) characteristic of L 10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

  18. In situ7Li and 133Cs nuclear magnetic resonance investigations on the role of Cs+ additive in lithium-metal deposition process

    Science.gov (United States)

    Hu, Jian Zhi; Zhao, Zhenchao; Hu, Mary Y.; Feng, Ju; Deng, Xuchu; Chen, Xilin; Xu, Wu; Liu, Jun; Zhang, Ji-Guang

    2016-02-01

    Cesium ion (Cs+) has been reported to be an effective electrolyte additive to suppress Li dendrite growth which prevents the application of lithium (Li) metal as an anode for rechargeable Li batteries. In this work, we investigated the effect of Cs+ additive on Li depositions using quantitative in situ7Li and 133Cs nuclear magnetic resonance (NMR) with planar symmetric Li cells. It's found that the addition of Cs+ can significantly enhance both the formation of well aligned Li nanorods and reversibility of the Li electrode. In situ133Cs NMR directly confirms that Cs+ migrates to Li electrode to form a positively charged electrostatic shield during the charging process. Much more electrochemical "active" Li was found in Li films deposited with Cs+ additive, while more electrochemical "dead" and thicker Li rods were identified in Li films deposited without Cs+. Combining the in situ and the previous ex-situ results, a Li deposition model has been proposed to explain these observations.

  19. Magnetic record associated with tree ring density: Possible climate proxy

    Directory of Open Access Journals (Sweden)

    Pruner Petr

    2007-03-01

    Full Text Available Abstract A magnetic signature of tree rings was tested as a potential paleo-climatic indicator. We examined wood from sequoia tree, located in Mountain Home State Forest, California, whose tree ring record spans over the period 600 – 1700 A.D. We measured low and high-field magnetic susceptibility, the natural remanent magnetization (NRM, saturation isothermal remanent magnetization (SIRM, and stability against thermal and alternating field (AF demagnetization. Magnetic investigation of the 200 mm long sequoia material suggests that magnetic efficiency of natural remanence may be a sensitive paleoclimate indicator because it is substantially higher (in average >1% during the Medieval Warm Epoch (700–1300 A.D. than during the Little Ice Age (1300–1850 A.D. where it is

  20. Seismic, magnetic, and geotechnical properties of a landslide and clinker deposits, Powder River basin, Wyoming and Montana

    Science.gov (United States)

    Miller, C.H.

    1979-01-01

    Exploitation of vast coal and other resources in the Powder River Basin has caused recent, rapid increases in population and in commercial and residential development and has prompted land utilization studies. Two aspects of land utilization were studied for this report: (1) the seismic and geotechnical properties of a landslide and (2) the seismic, magnetic, and geotechnical properties of clinker deposits. (1) The landslide seismic survey revealed two layers in the slide area. The upper (low-velocity) layer is a relatively weak mantle of colluvium and unconsolidated and weathered bedrock that ranges in thickness from 3.0 to 7.5 m and has an average seismic velocity of about 390 m/s. It overlies high-velocity, relatively strong sedimentary bedrock that has velocities greater than about 1330 m/s. The low-velocity layer is also present at the other eight seismic refraction sites in the basin; a similar layer has also been reported in the Soviet Union in a landslide area over similar bedrock. The buried contact of the low- and high-velocity layers is relatively smooth and is nearly parallel with the restored topographic surface. There is no indication that any of the high-velocity layer (bedrock) has been displaced or removed. The seismic data also show that the shear modulus of the low-velocity layer is only about one-tenth that of the high-velocity layer and the shear strength (at failure) is only about one-thirtieth. Much of the slide failure is clearly in the shear mode, and failure is, therefore, concluded to be confined to the low-velocity layer. The major immediate factor contributing to landslide failure is apparently the addition of moisture to the low-velocity layer. The study implies that the low-velocity layer can be defined over some of the basin by seismic surveys and that they can help predict or delineate potential slides. Preventative actions that could then be taken include avoidance, dewatering, prevention of saturation, buttressing the toe, and

  1. Convenient synthesis of magnetically recyclable Fe{sub 3}O{sub 4}@C@CdS photocatalysts by depositing CdS nanocrystals on carbonized ferrocene

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dan [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Xie, Jianjian [Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Zhang, Yong; Qiao, Ru [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Li, Sheng [Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Li, Zhengquan, E-mail: zqli@zjnu.edu.cn [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China)

    2015-10-15

    Development of magnetic visible-light-driven photocatalysts is desirable to the practical application of photocatalyts for collection and recycling use. Here we present a facile approach to synthesize Fe{sub 3}O{sub 4}@C@CdS magnetic photocatalysts which can avoid multi-step preparation process. Through one-step solvothermal carbonization of ferrocene, the produced carbon-coated Fe{sub 3}O{sub 4} clusters can serve as both magnetic cores and deposition substrates for in situ generating crystalline CdS nanocrystals on them by rapid microwave irradiation. The prepared Fe{sub 3}O{sub 4}@C@CdS nanoparticles exhibit a uniform core–shell structure and display good photocatalytic activity and recyclability in the degradation of organic dyes. These magnetic photocatalysts may find potential application in wastewater treatment for the future environment remedy. - Highlights: • A rapid strategy is presented to obtain multifunctional core–shell nanostructures. • Magnetic visible-light-driven Fe{sub 3}O{sub 4}@C@CdS nanophotocatalysts are synthesized. • Carbonized ferrocene can provide both magnetic cores and good deposition substrate. • Photocatalytic and recyclable properties of Fe{sub 3}O{sub 4}@C@CdS nanoparticles are explored.

  2. Verification of antiferromagnetic exchange coupling at room temperature using polar magneto-optic Kerr effect in thin EuS/Co multilayers with perpendicular magnetic anisotropy

    Science.gov (United States)

    Goschew, A.; Scott, M.; Fumagalli, P.

    2016-08-01

    We report on magneto-optic Kerr measurements in polar geometry carried out on a series of thin Co/EuS multilayers on suitable Co/Pd-multilayer substrates. Thin Co/EuS multilayers of a few nanometers individual layer thickness usually have their magnetization in plane. Co/Pd multilayers introduce a perpendicular magnetic anisotropy in the Co/EuS layers deposited on top, thus making it possible to measure magneto-optic signals in the polar geometry in remanence in order to study exchange coupling. Magneto-optic Kerr-effect spectra and hysteresis loops were recorded in the visible and ultraviolet photon-energy range at room temperature. The EuS contribution to the magneto-optic signal is extracted at 4.1 eV by combining hysteresis loops measured at different photon energies with polar magneto-optic Kerr-effect spectra recorded in remanence and in an applied magnetic field of 2.2 T. The extracted EuS signal shows clear signs of antiferromagnetic coupling of the Eu magnetic moments to the Co layers. This implies that the ordering temperature of at least a fraction of the EuS layers is above room temperature proving that magneto-optic Kerr-effect spectroscopy can be used here as a quasi-element-specific method.

  3. Identification and characterization of tsunami deposits off southeast coast of India from the 2004 Indian Ocean tsunami: Rock magnetic and geochemical approach

    Indian Academy of Sciences (India)

    S Veerasingam; R Venkatachalapathy; N Basavaiah; T Ramkumar; S Venkatramanan; K Deenadayalan

    2014-06-01

    The December 2004 Indian Ocean Tsunami (IOT) had a major impact on the geomorphology and sedimentology of the east coast of India. Estimation of the magnitude of the tsunami from its deposits is a challenging topic to be developed in studies on tsunami hazard assessment. Two core sediments (C1 and C2) from Nagapattinam, southeast coast of India were subjected to textural, mineral, geochemical and rock-magnetic measurements. In both cores, three zones (zone I, II and III) have been distinguished based on mineralogical, geochemical and magnetic data. Zone II is featured by peculiar rockmagnetic, textural, mineralogical and geochemical signatures in both sediment cores that we interpret to correspond to the 2004 IOT deposit. Textural, mineralogical, geochemical and rock-magnetic investigations showed that the tsunami deposit is featured by relative enrichment in sand, quartz, feldspar, carbonate, SiO2, TiO2, K2O and CaO and by a depletion in clay and iron oxides. These results point to a dilution of reworked ferromagnetic particles into a huge volume of paramagnetic materials, similar to what has been described in other nearshore tsunami deposits (Font et al. 2010). Correlation analysis elucidated the relationships among the textural, mineral, geochemical and magnetic parameters, and suggests that most of the quartz-rich coarse sediments have been transported offshore by the tsunami wave. These results agreed well with the previously published numerical model of tsunami induced sediment transport off southeast coast of India and can be used for future comparative studies on tsunami deposits.

  4. Giant magnetoimpedance effect of multilayered structure(F/SiO2)3/Ag/(SiO2/F)3 films deposited in a longitudinal magnetic field

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The soft magnetic properties and giant magnetoimpedance(GMI) effect of the multilayered structure(F/SiO2)3/Ag/(SiO2/F)3(F≡Fe71.5Cu1Cr2.5V4Si12B9) films,which were prepared by radio frequency sputtering without and with a longitudinal magnetic field of about 72 kA/m,are studied.The results show that the GMI effect almost cannot be detected in the samples deposited without field,whereas,a longitudinal magnetic field applied during deposition process obviously optimizes the soft magnetic properties of the films,and noticeable GMI effect is obtained.The maximum values of the longitudinal and transverse GMI ratios are 45% and 44% at the frequency of 6.81 MHz,respectively.In addition,the dependence of magnetoimpedance ratio,magnetoresistance ratio,magnetoreactance ratio and effective permeability ratio on the frequency has been investigated.We found that the GMI spectrum curves in the longitudinal and transverse cases almost overlap for the field-deposited sample.The GMI effect is mainly a giant magnetoinductive effect at low frequencies.When f >9 MHz,magnetoreactance ratio changes to a negative,i.e.,the property of reactance changes from inductive to capacitive.

  5. A comparative structural and magnetic study of Fe100-xPdx(x=15, 20 and 36) thin films deposited on Si (100) and glass substrates

    Science.gov (United States)

    Bahamida, S.; Fnidiki, A.; Laggoun, A.; Guittoum, A.

    2015-10-01

    Various structural and magnetic characterization techniques have been used to investigate Fe100-xPdx (x=15, 20 and 36) thin films deposited onto silicon and glass substrates, by thermal evaporation technique. X-ray diffraction analysis shows the presence of supersaturated solid solution with bcc structure for Pd concentrations of 15% and 20%. However, for 36% of Pd, in addition to the supersaturated α-FePd (bcc) phase, another disordered FePd3 phase with fcc structure is present. At 20 at% Pd, the magnetic characterization shows a saturation of the bcc (α-FePd) phase and the appearance of the fcc phase. The correlation between the structure and magnetic properties allows us to compare the two substrates effects on deposited thin films. As results, the measurements indicate that the grain size D, the thin film thickness and the d(110) spacing significantly affect the magnetic coercivity HC. The Fe-Pd alloys deposited on a monocrystalline Si (100) and glass substrate show that the coercivity HC is given by the random anisotropy model.

  6. The effect of growth surface morphology on the crystal structure and magnetic property of L1{sub 0} order PtFe layers deposited by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Ding Wanyu, E-mail: dwysd_2000@163.com [Graduate School of Saitama Institute of Technology, Fukaya, Saitama 369-0293 (Japan) and School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028 (China); Ishiguro, Satoshi; Ogatsu, Ryo [Graduate School of Saitama Institute of Technology, Fukaya, Saitama 369-0293 (Japan); Ju, Dongying, E-mail: dyju@sit.ac.jp [Graduate School of Saitama Institute of Technology, Fukaya, Saitama 369-0293 (Japan)

    2012-08-01

    The Fe/Pt/Fe/Pt layers (Pt/Fe multilayer) were deposited on general glass substrate at room temperature by magnetron sputtering technique. Varying the deposition and post-annealing treatment parameters, the PtFe alloy (PtFe) layer with different crystal structures and magnetic properties were obtained at the interface between Fe and Pt layer. The characterization by X-ray diffraction (XRD) showed that the as-deposited Pt/Fe multilayer only contained pure Fe and Pt with body-centered and face-centered cubic structures, respectively. As-deposited Pt layer displayed (2 0 0) preferred orientation, and the columnar grains structure could be observed by the scanning electron microscopy. The PtFe layers with L1{sub 0} face-centered cubic structure could be formed at the interface between Pt and Fe layers by post-annealing the multilayers at 500 Degree-Sign C. In case of Pt/Fe multilayer deposited on smooth substrate, the larger columnar grains in Pt layer resulted in L1{sub 0} PtFe layers without any preferred orientation. While in case of Pt/Fe multilayer deposited on the rough substrate, the thinner columnar grains in Pt layer could induce L1{sub 0} PtFe layers with (2 0 0) preferred orientation. In this case, the vibrating sample magnetometer results indicated that, the magnetic coercivity in plane and out-of-plane model could reach 3.72 and 2.32 kOe, respectively. Based on above results, the L1{sub 0} structure Pt/Fe multilayer with satisfied magnetic properties could be prepared at low temperature by our simple route.

  7. The effect of Cr substitution on the structural, electronic and magnetic properties of pulsed laser deposited NiFe2O4 thin films

    Science.gov (United States)

    Panwar, Kalpana; Tiwari, Shailja; Bapna, Komal; Heda, N. L.; Choudhary, R. J.; Phase, D. M.; Ahuja, B. L.

    2017-01-01

    We have studied the structural, electronic and magnetic properties of pulsed laser deposited thin films of Ni1-xCrxFe2O4 (x=0.02 and 0.05) on Si (111) and Si (100) substrates. The films reveal single phase, polycrystalline structure with larger grain size on Si (111) substrate than that on Si (100) substrate. Contrary to the expected inverse spinel structure, x-ray photoemission (XPS) studies reveal the mixed spinel structure. XPS results suggest that Ni and Fe ions exist in 2+ and 3+ states, respectively, and they exist in tetrahedral as well as octahedral sites. The deviation from the inverse spinel leads to modified magnetic properties. It is observed that saturation magnetization drastically drops compared to the expected saturation value for inverse spinel structure. Strain in the films and lattice distortion produced by the Cr doping also appear to influence the magnetic properties.

  8. Mineral magnetism of dusty olivine

    DEFF Research Database (Denmark)

    Lappe, Sophie-Charlotte L. L.; Church, Nathan S.; Kasama, Takeshi

    2011-01-01

    The magnetic properties of olivine-hosted Fe-Ni particles have been studied to assess the potential of "dusty olivine" to retain a pre-accretionary remanence in chondritic meteorites. Both body-centered (bcc) and face-centered cubic (fcc) Fe-Ni phases were formed by reduction of a terrestrial...... SD particles using electron holography is presented. Combining the volume information with constraints on coercivity, we calculate the thermal relaxation characteristics of the particles and demonstrate that the high-coercivity component of remanance would remain stable for 4.6 Ga, even...

  9. Rock magnetic properties of Nihewan sediments at Xujiayao

    Institute of Scientific and Technical Information of China (English)

    WANG; Xisheng(王喜生); Lφvlie; Reidar; SU; Pu(苏朴)

    2002-01-01

    Rock magnetic measurements of Nihewan sediments from Xujiayao section demonstrate that magnetite, hematite and maghemite are dominant remanent magnetization carriers. Monitoring the variations of magnetic susceptibility(MS) and saturating isothermal remanent magnetization(SIRM) at low temperature are the attractive ways of detecting the presence of magnetite, maghemitization and superparamagnetic grain sizes. Low-temperature MS investigations suggest that susceptibility enhancement for Xujiayao samples is mainly due to the remarkable presence of SD/MD magnetite to some degree though some magnetite grains have been partially oxidized at some depths. It is tentatively concluded that both SD/MD magnetite and hematite are of detrital origin and carry a characteristic remanent magnetization(ChRM), whereas maghemite can be attributed to be chemical origin, overprinting a reversed polarity component of Matuyama age.

  10. Magnetic Properties of Cobalt-coated Silicon Steels Prepared by Electrodeposition

    Directory of Open Access Journals (Sweden)

    Somkane PIROMRAK

    2007-01-01

    Full Text Available Magnetic properties of silicon steels (1.26 % silicon coated by cobalt of varying thickness were studied. Cobalt ranging from 11 to 68 µm in thickness was deposited on silicon steel substrates (0.5 mm thick, 0.4 mm wide and 55.0 mm long cut from sheets of recycled transformer cores. By electrodeposition in CoSO4 electrolyte with 90 mA applied current at pH 1.86, the deposition rate was 1.11 µm/min. Although deposition of cobalt increased saturation induction of silicon steels, it also increased hysteresis loss signified by wider hysteresis loops with larger remanent induction and coercive field. Since the magnetoimpedance (MI is related to the magnetic softness of materials, the MI ratio decreased with increasing thickness of the cobalt layer. Although the cobalt coating did not enhance the MI ratio of silicon steels, it expanded the peak of frequency-dependent MI curves. Therefore, the frequency range with large MI ratio in silicon steels can be extended by the deposition of a cobalt layer. From microscopic images, grains and magnetic domains of the silicon steel were of the order of 10 µm whereas smaller domain size was observed in the cobalt layer.

  11. 日本海南部48ka以来的环境磁学记录及其反映的千年尺度环境变化%MILLENNIAL ENVIRONMENTAL AND POST-DEPOSITIONAL CHANGES OF THE LAST 48ka RECORDED BY ENVIRONMENTAL MAGNETIC PARAMETERS IN SOUTHERN JAPAN SEA

    Institute of Scientific and Technical Information of China (English)

    葛淑兰; 刘建兴; 石学法; 刘焱光; 王昆山; 闫仕娟; 杨刚; 邹建军

    2012-01-01

    ,tephra-chronology and characteristic dark layer TL2 reported previously, the " paleointensities" normalized by magnetic susceptibility, anhysteretic remanence and saturated remanence seem to correlate with intensity curve of core ODP 983 in North Atlantic and the inclination also agrees well with other cores in Japan Sea and the Pacific Ocean. On the new detailed paleointensity-assisted age, magnetic input in last glacial (36 ~ 15kaB. P. ) is largest in concentration, finest in size and softest in coercivity for the last 48ka. Rock magnetic parameters reveal signals of early diagenesis stronger in the last 7ka and weaker in 48 ~ 7kaB. P. Because of the un-continuity of the core below 4. 5m ( ca. 20kaB. P. ) due to drying,the response of rock magnetic to millennial events is uncertain before 20kaB. P.,but the deglacial transition is very peculiar in our results. Magnetic minerals which are coarse in size,less in amount and low in low-coercivity proportion deposited. At the same time,Ti varies accordingly with rock magnetic parameters,reflecting changes of terrigenous input and/or dynamic winnowing. Stronger bottom current with varying directions revealed by anisotropy of magnetic susceptibility, increased sand and silt content indicate turbulent and oxygenated conditions at the sea floor,which is totally different with the stratified ocean in the last glacial maximum. The rock magnetic evolution in core KCES therefore has the potential to record changes of terrigenous input, bottom current and post-depositional modification which could correspond with the well known millennial events.

  12. Tests on Application of Soil Magnetic and Integrated Gamma Ray TLD and TC Methods to the Exploration of Sandstone-Type Uranium Deposits

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper introduces the test results of the soil magnetic survey and the integrated gamma-ray TLD and TC methods for sandstone-type uranium exploration and describes the prospecting mechanism. The tests have proved that these approaches have yielded good results on classifying the sedimentary facies, defining the redox transitional zones and reflecting deep mineralization information. They may probably become new methods on searching for sandstone-type uranium deposits.

  13. High critical current density under magnetic fields in as-grown MgB{sub 2} thin films deposited by molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Haruta, M [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Fujiyoshi, T [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Kihara, S [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Sueyoshi, T [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Miyahara, K [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Harada, Y [Iwate Industry Promotion Centre, Iioka-shinden 3-35-2, Morioka, Iwate 020-0852 (Japan); Yoshizawa, M [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka, Iwate 020-8551 (Japan); Takahashi, T [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka, Iwate 020-8551 (Japan); Iriuda, H [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka, Iwate 020-8551 (Japan); Oba, T [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka, Iwate 020-8551 (Japan); Awaji, S [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Watanabe, K [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Miyagawa, R [Kumamoto Industrial Research Institute, 3-11-38 Higashi-machi, Kumamoto 862-0901 (Japan)

    2007-01-15

    As-grown MgB{sub 2} thin films were prepared by a MBE method under the conditions of low temperature, low deposition rate and high vacuum for applications in electric devices. The MgB{sub 2} thin films deposited on MgO and Ti buffered ZnO substrates have considerably higher J{sub c} under magnetic fields among MgB{sub 2} thin films reported before. The value of J{sub c} for the MgB{sub 2} thin film deposited on Ti buffered ZnO has been 5.8 x 10{sup 5} A cm{sup -2} at 10 K, 5 T in the magnetic field applied parallel to the c axis. In the angular dependence of J{sub c}, the peak of J{sub c} attributable to c-axis-correlated pinning centres has been observed when the magnetic field was applied parallel to the c axis. (rapid communication)

  14. Quantification of Magnetic Components in Sediments with Applications in Paleoenvironmental Studies

    Science.gov (United States)

    Lascu, Ioan

    years. Our results reveal several episodes of reduced precipitation, during which less sediment is mobilized from the catchment by overland flow and runoff. The most prominent episode occurred at the end of the Little Ice Age, indicating that this time period was not only cold but might have been drier than previously thought. The spatial control on sediment-magnetic properties was established via a survey of the magnetic properties of surface sediments from several Minnesota lakes. The magnetic properties are controlled by the competing fluxes of detrital and biogenic particles, according to location in the basin, while the position of the oxic-anoxic interface controls whether biogenic magnetite is formed in the sediment or in the water column, with implications in the preservation of intact versus collapsed bacterial chains. The thesis concludes with an incursion into the magnetic properties of chemical sediments from caves, or speleothems. The magnetic recordings preserved in calcite speleothems hold enormous potential for paleomagnetic and paleoenvironmental reconstructions. Speleothems lock in magnetization instantly, are not affected by post-depositional effects, and can be dated with high precision. The natural remanence in speleothems is carried mainly by magnetite, and the main remanence acquisition mechanism is depositional, through physical alignment of detrital magnetic grains parallel to the Earth's magnetic field. Future speleothem magnetism studies should benefit from increasingly sensitive magnetometers, operating at high spatial resolution, that are able to resolve short-term geomagnetic variability, and characterize events such as geomagnetic excursions at an unprecedented scale.

  15. A Preliminary Study on Paleomagnetism and Rock Magnetism of Eclogite from the Maobei Area

    Institute of Scientific and Technical Information of China (English)

    Meng Xiaohong; Yu Qinfan; GuoYouzhao; Zhou Yaoxiu

    2007-01-01

    A preliminary study of paleomagnetism and rock magnetism has been done on 55 eclogite samples collected from the Chinese Continental Scientific Drilling (CCSD) site at the Maobei (毛北) area,Donghai (东海) County, Jiangsu (江苏) Province. Also the isothermal remanence, hysteresis loop, magnetic fabric, thermal susceptibility were measured, and analyses were made by electron-probe and scanning electric microscope on some samples synchronously. The result indicates that there are two groups of stable remanence, the normal and reversed magnetization. The remanence orientations are: D=94.3°, I=-29.1° and D=273.7°, I=15.4°, respectively. The magnetization intensity and the density of the samples which carry the normal magnetization are very different from those bearing reversed magnetization. The magnetic anisotropy is weak, and the minimum axis is hardly determined. The isothermal remanence and the hysteresis loop show that the magnetic carriers of the eclogite are likely SD (single domain) and PSD(pseudo-single domain) magnetite. According to the magnetic property, the cause of formation of magnetic carriers, the mechanism of the remanence, and the significance for the tectonics are discussed.

  16. Magnetic dipole moment of a spherical shell with TRM acquired in a field of internal origin. [Thermoremanent Magnetization implications for lunar magnetic field

    Science.gov (United States)

    Srnka, L. J.

    1976-01-01

    The acquisition of thermoremanent magnetization (TRM) by a cooling spherical shell is studied for internal magnetizing dipole fields, using Runcorn's (1975) theorems on magnetostatics. If the shell cools progressively inward, inner regions acquire TRM in a net field composed of the dipole source term plus a uniform field due to the outer magnetized layers. In this case, the global dipole moment and external remanent field are nonzero when the whole shell has cooled below the Curie point and the source dipole has disappeared. The remanent field outside the shell is found to depend on the thickness, radii, and cooling rate of the shell, as well as the coefficient of TRM and the intensity of the magnetizing field. Some implications for the moon's remanent dipole moment are discussed.

  17. Magnetic force microscopy and simulation studies on Co$_{50}$Fe$_{50}$ elliptical nanomagnets

    Indian Academy of Sciences (India)

    N V S S SESHAGIRI RAO; V SATYA NARAYANA MURTHY; Y J V S RAMAKRISHNA SHARMA

    2016-06-01

    We studied the magnetization reversal mechanism of single-layered Co50Fe50 nanomagnets by measuring the magnetization reversal and using the micromagnetic simulations. The magnetization reversal strongly depends on the thickness of the nanomagnets. In the remanent state, the magnetic force microscopy studies and the simulation data showed the formation of single and vortex states depending on the thickness of nanomagnets.

  18. Rock magnetic and other geophysical signatures of relative sea level change in the Middle Cambrian Wheeler Formation, Drum Mountains, West-Central Utah

    Science.gov (United States)

    Halgedahl, S. L.; Jarrard, R. D.

    2011-12-01

    The Wheeler Formation of West-Central Utah is a succession of mixed carbonate-siliciclastic rocks deposited during the Middle Cambrian along a passive continental margin of Laurentia (western margin, in today's coordinates). The depositional setting was a gentle ramp, bounded by a normal fault on the south. The present study focuses on the Wheeler Formation in the Drum Mountains, Utah, which is thought to have recorded Middle Cambrian sea level changes and which is known to yield exceptionally-preserved fossils with soft parts, similar to the famed Burgess shale. An integrated approach has been used here to investigate the following: (1) high-resolution changes in water depth (sea level changes?) with stratigraphic position; (2) where exceptionally preserved fossils are most likely to occur; and (3) mineralogical indicators of sea level change, such as magnetic susceptibility and other rock magnetic properties. Rocks consist of limestones, argillaceous limestones, and finely-bedded mudstones (shales). Methods used here are: measurements of magnetic susceptibility, natural remanent magnetization, and viscous remanent magnetization; hysteresis loops; spectral gamma ray; coulometry to determine calcite content; X-ray diffraction; and field mapping. In these rocks, mineralogical analyses indicate primarily a 2-component system of calcite and terrigenous minerals, mainly illite. Magnetic susceptibility, gamma ray, and coulometry results strongly indicate that magnetic susceptibility stems primarily from the paramagnetic clay component, namely, illite. Thus, both magnetic susceptibility and gamma ray increase linearly with decreasing calcite content throughout the section studied. Deep-water shales yield very high values of gamma ray and magnetic susceptibility; by contrast, carbonates with low gamma ray and low magnetic susceptibilities were deposited in relatively shallow water. These results lead to the following conclusions: (1) changes in relative water depth have

  19. Effect of annealing time on structural and magnetic properties of laser ablated oriented Fe3O4 thin films deposited on Si(100)

    Indian Academy of Sciences (India)

    Shahid M Ramay; Saadat A Siddiqi; M Sabieh Anwar; C Y Park; S-C Shin

    2012-08-01

    We have fabricated ∼143nm Fe3O4 thin films on Si(100) substrates at 450°C and then annealed them at the same temperature for 30, 60 and 90 min under a vacuum of 10-6 torr with pulsed laser deposition. We studied the effects on the structural and magnetic properties of Fe3O4 thin films. The films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). XRD studies showed pure single phase spinel cubic structure of Fe3O4 with a preferential [111] orientation, independent of substrate orientation at 90 min annealing. Higher magnetization was obtained up to 60 min annealing due to Fe phase but at 90 min, we obtained reduced magnetization of 335 emu/cc. This is attributed to the formation of antiphase boundaries between substrate and film.

  20. Magnetic properties of magnetic liquids with iron-oxide particles - the influence of anisotropy and interactions

    DEFF Research Database (Denmark)

    Johansson, C.; Hanson, M.; Pedersen, Michael Stanley

    1997-01-01

    Magnetic liquids containing iron-oxide particles were investigated by magnetization and Mossbauer measurements. The particles were shown to be maghemite with a spontanious saturation magentization Ms = 320 kA m-1 at 200 K and a normalized high-field susceptibility x/M0 = 5.1x10-6 mkA-1, practical......-field-cooled magnetization and isothermal remanence decay, is influenced by interactions and strongly dependent on the applied magnetic field....

  1. Influence of voltage variation on structure and magnetic properties of Co1- x Sn x ( X = 0.3-0.7) nanowire alloys in alumina by electrochemical deposition

    Science.gov (United States)

    Ahmad, Naeem; khan, Suleman; Arman liaqat, M.; Awais, Muhammad; Shah, Saqlain A.; Ahmed, Ishfaq; Jabeen, Nyla; Majid, Abdul; Iqbal, Javed

    2017-01-01

    The Co1- X Sn X ( X = 0.3-0.7) alloy nanowires with high density and uniform size were prepared by alternating current (AC) electrodeposition into anodized aluminum oxide templates using different AC potential from 9 to 17 V. The diameter and length of CoSn nanowires is found to be 170 nm and 1 µm, respectively, using SEM images. The formation of CoSn nanowires has been confirmed by using EDX analysis. The XRD data of all samples demonstrate the hexagonal structure of CoSn nanowires and other phase is also observed. The grain size of nanowires increases with the increase in potentials observed from the slight shift in diffraction angle toward higher values. The hysteresis curves of CoSn nanowires measured using vibrating sample magnetometer show isotropic and ferromagnetic behavior due to presence of diffuse magnetic moments and cobalt contents, respectively. When AC potential increases gradually in equal intervals, the deposition of magnetic ions decreases than that of non-magnetic ions as a result coercivity ( H C) and saturation magnetization ( M S) decreases. The substitution of more magnetic ions into CoSn alloy nanowires is found due to the increase in potential after the critical voltage (11-13 V) causing disintegration of magnetic domains, formation of defect clusters and nanostructure islands enhancing the density sites of domain walls. The increase in coercivity ( Hc) and saturation magnetization ( Ms) is attributed to the formation of pinning sites that obstruct the motion of domain walls due to the increase in number density of magnetic grain boundaries and phase boundaries.

  2. Influence of anisotropy of magnetic susceptibility (AMS) on paleomagnetic sampling in volcanic glasses: a case study on rheomorphic ignimbrites of the Yellowstone hotspot-track, southern Idaho

    Science.gov (United States)

    Finn, D.; Coe, R. S.; Murphy, J.; Bodiford, S.; Kelly, H.; Foster, S.; Spinardi, F.; Reichow, M. K.; Knott, T.; Branney, M. J.

    2012-12-01

    anisotropy is likely formed during initial compaction and/or shearing during emplacement, the plane of easy magnetic susceptibility is near the depositional surface. This typically results in an artificial shallowing of remanent directions by up to 40 degrees. This observation is common to several ignimbrites. To better observe this effect, we have sampled four vertical profiles through one cooling-unit in locations ~100 km apart. Two profiles include a baked soil, on which the ignimbrite was deposited. Results show that the underlying baked soil and central lithoidal regions match well and accurately record the paleomagnetic field, whereas the upper and lower vitrophyres are both intensely anisotropic and record discrepant remanent magnetic directions. These observations may help guide future paleomagnetic work in other volcanic provinces with silicic, highly welded ignimbrites and lavas.

  3. Advanced Magnetic Metrology Instrumentation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The extraordinary progress in magnetic peripheral storage systems has been fueled by the ad vancements in heads (MR, GMR, spin valves) and in very high coercivity, Iow remanence thickness product (Mrt) media. These advancements are imposing new performance require ments on the magnetometers (VSMs) used to characterize these materials. At the same time, they have introduced a new paradigm for in-process (nondestructive, robotic) magnetic metrol ogy tools to assure the stringent product uniformity requirements. In this paper, we discuss the recent advancements in magnetometry for characterizing state-of-the-art media and heads, as well as other magnetic materials.

  4. Mineral magnetism to probe into the nature of palaeomagnetic signals of subtropical red soil sequences in southern China

    Science.gov (United States)

    Liu, Caicai; Deng, Chenglong; Liu, Qingsong; Zheng, Longting; Wang, Wei; Xu, Xinming; Huang, Sheng; Yuan, Baoyin

    2010-06-01

    Magnetic polarity stratigraphy has proved to be useful in dating of both marine and terrestrial sedimentary sequences over the world. However, the reliability of magnetostratigraphic results of red soil sequences in subtropical southern China has been found to be variable in different regions. To probe into the capabilities of recording magnetic polarity stratigraphy in the red soils, three red soil sequences have been selected for detailed mineral magnetic, petrographic and/or palaeomagnetic analyses. These include the Xuancheng and Qiliting sequences, which are located in the lower reaches of the Yangtze River and the Damei sequence in the Bose Basin near the Tropic of Cancer. Palaeomagnetic results indicate that the Xuancheng sequence has recorded the Brunhes Chron and the late Matuyama Chron, including a short interval probably representing the Santa Rosa geomagnetic event. The Xuancheng and Qiliting sequences have faithfully recorded the palaeogeomagnetic field behaviour while the Damei sequence has failed. Detailed mineral magnetic and petrographic measurements suggest that four magnetic minerals (magnetite, maghemite, haematite and goethite) are contained in the three studied sequences, but the characteristic remanent magnetization (ChRM) carriers are different. For the Xuancheng and Qiliting samples, the ChRM carriers are magnetite and haematite, which are all of detrital origin. However, the ChRMs of Damei samples are carried by pedogenic haematite with an unblocking temperature (TB) of about 630-640 °C, which has overprinted the primary remanence of the Damei red soil deposits. This pedogenic haematite is mainly produced by chemical weathering, which is commonly intensified by the climate of high temperature and rainfall. It further suggests that climatic conditions have a great effect on the nature of palaeomagnetic signals of the red soil sequences. In addition, the red pigment components in the red soils may be used to indicate the degree of

  5. Investigation of Ni@CoO core-shell nanoparticle films synthesized by sequential layer deposition

    Science.gov (United States)

    Spadaro, M. C.; Luches, P.; Benedetti, F.; Valeri, S.; Turchini, S.; Bertoni, G.; Ferretti, A. M.; Capetti, E.; Ponti, A.; D'Addato, S.

    2017-02-01

    Films of Ni@CoO core-shell nanoparticles (NP Ni core size d ≈ 11 nm) have been grown on Si/SiOx and lacey carbon supports, by a sequential layer deposition method: a first layer of CoO was evaporated on the substrate, followed by the deposition of a layer of pre-formed, mass-selected Ni NPs, and finally an overlayer of CoO was added. The Ni NPs were formed by a magnetron gas aggregation source, and mass selected with a quadrupole mass filter. The morphology of the films was investigated with Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. The Ni NP cores have a shape compatible with McKay icosahedron, caused by multitwinning occurring during their growth in the source, and the Ni NP layer shows the typical random paving growth mode. After the deposition of the CoO overlayer, CoO islands are observed, gradually extending and tending to merge with each other, with the formation of shells that enclose the Ni NP cores. In situ X-ray Photoelectron Spectroscopy showed that a few Ni atomic layers localized at the core-shell interface are oxidized, hinting at the possibility of creating an intermediate NiO shell between Ni and CoO, depending on the deposition conditions. Finally, X-ray Magnetic Circular Dichroism at the Ni L2,3 absorption edge showed the presence of magnetization at room temperature even at remanence, revealing the possibility of magnetic stabilization of the NP film.

  6. STUDY ON DEPOSITION OF MAGNETIC FILMS USING ARC ION PLATING%电弧离子镀沉积磁性薄膜的研究

    Institute of Scientific and Technical Information of China (English)

    常正凯; 肖金泉; 陈育秋; 刘山川; 宫骏; 孙超

    2012-01-01

    Arc ion plating (AIP) has been widely used for depositing various kinds of coatings due to the excellent characteristics of high deposition rate, convenient parameter control, high degree of ionization in the target material, good coating-substrate adhesion, flexibility of target arrangements and merits of producing coatings with high packing density. Magnetic films, with a few micrometers or less, could be utilized in the electronics industry, such as magnetic recording, magnetic microelectrome-chanical systems, magneto optical modulator, and so on. In AIP process, due to magnetic shielding and self-induced magnetic field, arc spot on the surface of the magnetic target moved outside all the time, and the erosion of the magnetic target could not be stable. In this study, arc spot outside moving and unstable erosion of the magnetic target in arc ion plating have been investigated. The distribution of the magnetic field of the nonmagnetic target and the magnetic target under an additional magnetic field was simulated by the finite element method (FEM). The effect of magnetic field on the arc spot movement was researched. With the physical mechanism of the arc spot discharge, the feasibility on the solution of the application problem of the magnetic target has been discussed by the program of the composited structure target, which were composed of magnetic target materials and target shell of low saturation vapor pressure metal, target shell of insulating ceramics, or target shell of soft magnetic metal. The results showed that all these solutions could solve the problem of arc spot outside moving efficiently. In the study, the transition temperature is (136.6±23.0) ℃ in the solutions of the target shell of low saturation vapor pressure metal or insulating ceramics, during which the arc striking frequently transformed to the controlled movement of arc spot.%研究了电弧离子镀磁性靶材使用过程中发生“跑弧”并导致靶材无法稳定刻蚀的问

  7. Dating of Mesoproterozoic metamorphism in the Mount Isa and George Fisher Zn-Pb-Cu-Ag deposits, Australia, by paleomagnetism

    Science.gov (United States)

    Kawasaki, K.; Symons, D. T.

    2010-12-01

    The Mount Isa Zn-Pb-Cu-Ag and George Fisher Zn-Pb-Ag black-shale-hosted deposits in Queensland, Australia, are in carbonaceous and dolomitic shales of the ~1655 Ma Urquhart Formation of the Mount Isa Group that exhibit greenschist facies metamorphism. Both deposits give lead model ages of ~1655 Ma. Ar-Ar biotite and Re-Os ages for the Mount Isa copper ore are 1523±3 and 1372±4 Ma, respectively. Excluding modern hematite, paleomagnetic and rock magnetic analyses of 333 specimens (28 sites) isolate a stable characteristic remanent magnetization (ChRM) in single- and pseudosingle-domain pyrrhotite for the Zn-Pb-Ag ore specimens and in pyrrhotite and/or titanomagnetite for the Cu ore. A negative paleomagnetic fold test shows that the ChRM postdates D3 deformation of the ~1595 to 1500 Ma Isan orogeny, yielding a Mesoproterozoic paleopole at ~1505 Ma on the northern Australian apparent polar wander path. The ~1505 Ma age is similar to the ~1523 Ma Ar-Ar age and it provides a minimum age for ore genesis of both deposits, as well as the age for peak greenschist metamorphism during the Isan orogeny in the surrounding Mount Isa inlier.

  8. In-plane electric field controlled perpendicular magnetic anisotropy in an FePt/[Pb(Mg1/3Nb2/3)O3]0.7-(PbTiO3)0.3 heterostructure

    Science.gov (United States)

    Guo, Qi; Xu, Xiaoguang; Feng, Julong; Liu, Pengfei; Wu, Yong; Ma, Li; Zhou, Shiming; Miao, Jun; Jiang, Yong

    2016-06-01

    We report the in-plane electric field controlled perpendicular magnetic anisotropy of L10-FePt films deposited on polarized [Pb(Mg1/3Nb2/3)O3]0.7-(PbTiO3)0.3 single crystal substrates. The out-of-plane coercivity (H c⊥) of FePt films exhibits a regular response to the in-plane electric field applied on substrates. The experimental change of H c⊥ is approximately 21.3% with the electric field varying from -10 to 10 kV/cm. The magnetization direction can be controlled by switching the electric field. The remanence of FePt films can also be manipulated by the electric field, so that a “W”-shaped sawtooth magnetic signal can be generated by a sawtooth electric field.

  9. Magnetic Properties of Ni Nanoparticles and Ni(C) Nanocapsules

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Structure and magnetic properties of Ni nanoparticles and Ni(C) nanocapsules were studied. The carbon atoms hardly affect the lattice of Ni to form Ni-C solid solution or nickel carbides. The large thermal irreversibility in zerofield-cooled and zero-field magnetization curves indicates magnetic blocking with a wide energy barrier. Saturation magnetization, remanent magnetization and coercivity of Ni(C) nanocapsules decrease with increasing temperature.

  10. Magnetism and the history of the moon

    Science.gov (United States)

    Strangway, D. W.; Gose, W. A.; Pearce, G. W.; Carnes, J. G.

    1973-01-01

    All lunar samples measured to date contain a weak but stable remanent magnetization of lunar origin. The magnetization is carried by metallic iron and is considered to be caused by cooling from above the Curie point in the presence of a magnetic field. Although at present the moon does not have a global field, the remanent magnetization of the rock samples and the presence of magnetic anomalies, both on the near and far side of the moon, imply that the moon experienced a magnetic field during some portion of its history. The field could have been generated in a liquid iron core sustaining a self-exciting dynamo, but there are some basic thermal and geochemical objections that need to be resolved.

  11. Magnetic Properties and Kinetics Parameters of Electroless Magnetic Loss CoFeB Films

    Institute of Scientific and Technical Information of China (English)

    LIU Chang-hui; HE Hua-hui; SHEN Xiang; LI Hai-hua

    2008-01-01

    Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent. The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate, pH of the plating bath, plating temperature and the metallic ratio. The estimated regression coefficient b0-b3 confidence interval, residual error r and confidence interval rint were confirmed by a computer program. The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range. At 2 GHz, the μ′, μ″ of the electroless CoFeB films were 304 and 76.6, respectively, as the concentration of reducer is 1 g/L. Magnetic hysteresis loop of the deposited CoFeB films show a remanence close to the saturation magnetization and coercivity of about 55.7-127.4 A/m. The loops along the hard axis display low anisotropic field Hk of 2 388-3 582 A/m.

  12. The physical principles of rock magnetism

    CERN Document Server

    Stacey, Frank

    1974-01-01

    Developments in Solid Earth Geophysics 5: The Physical Principles of Rock Magnetism explores the physical principles of rock magnetism, with emphasis on the properties of finely divided magnetic materials. It discusses the origin and stability of rock magnetizations, the role of remanent magnetism in interpreting magnetic surveys, magnetic anisotropy as an indicator of rock fabric, and the relationship between piezomagnetic changes and seismic activity. Organized into 13 chapters, this volume discusses the properties of solids, magnetite and hematite grains, and rocks with magnetite grains

  13. LDRD Final Report - Investigations of the impact of the process integration of deposited magnetic films for magnetic memory technologies on radiation-hardened CMOS devices and circuits - LDRD Project (FY99)

    Energy Technology Data Exchange (ETDEWEB)

    MYERS,DAVID R.; JESSING,JEFFREY R.; SPAHN,OLGA B.; SHANEYFELT,MARTY R.

    2000-01-01

    This project represented a coordinated LLNL-SNL collaboration to investigate the feasibility of developing radiation-hardened magnetic non-volatile memories using giant magnetoresistance (GMR) materials. The intent of this limited-duration study was to investigate whether giant magnetoresistance (GMR) materials similar to those used for magnetic tunnel junctions (MTJs) were process compatible with functioning CMOS circuits. Sandia's work on this project demonstrated that deposition of GMR materials did not affect the operation nor the radiation hardness of Sandia's rad-hard CMOS technology, nor did the integration of GMR materials and exposure to ionizing radiation affect the magnetic properties of the GMR films. Thus, following deposition of GMR films on rad-hard integrated circuits, both the circuits and the films survived ionizing radiation levels consistent with DOE mission requirements. Furthermore, Sandia developed techniques to pattern deposited GMR films without degrading the completed integrated circuits upon which they were deposited. The present feasibility study demonstrated all the necessary processing elements to allow fabrication of the non-volatile memory elements onto an existing CMOS chip, and even allow the use of embedded (on-chip) non-volatile memories for system-on-a-chip applications, even in demanding radiation environments. However, funding agencies DTRA, AIM, and DARPA did not have any funds available to support the required follow-on technology development projects that would have been required to develop functioning prototype circuits, nor were such funds available from LDRD nor from other DOE program funds.

  14. Preparation and characterization of YBa{sub 2}Cu{sub 3}O{sub 7-x} thick films deposited on silver substrates by the electrophoretic deposition technique for magnetic screening applications

    Energy Technology Data Exchange (ETDEWEB)

    Grenci, G [Politecnico di Torino, Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, 10129 Turin (Italy); Denis, S [SUPRATECS group, Department of Electrical Engineering and Computer Science (B28), University of Liege, Sart-Tilman, 4000 Liege (Belgium); Dusoulier, L [CISS Department, Royal Military Academy, Brussels (Belgium); Pavese, F [CNR, Istituto di Metrologia ' G Colonnetti' , Turin (Italy); Penazzi, N [Politecnico di Torino, Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, 10129 Turin (Italy)

    2006-04-15

    The production of magnetic shields using high-temperature superconductors (HTS) is not straightforward, as these materials are brittle ceramics. In this paper, we report the results of investigations concerning the use of the electrophoretic deposition (EPD) technique to produce magnetic shields of various shapes and with large surface areas, in the form of a thick coating of HTS on a metallic substrate. For the first time, we report shielding characterization of samples prepared by the EPD technique. The most important problems concern the choice of the process parameters and the heat treatment of the coating, in order to obtain a dense and well-connected polycrystalline system. We have used the HTS compound YBa{sub 2}Cu{sub 3}O{sub 7-x} as the coating material and silver as the substrate. An optimized heat treatment, in an atmosphere with poor oxygen content, was chosen following experimental investigations. Different samples were produced in the form of slabs for chemical, structural and electrical characterization. A cylindrical sample was prepared for magnetic shielding measurements at 77 K. With an applied magnetic field parallel to its axis, the cylinder presents a high level of shielding (>80 dB) at low frequencies, for applied inductions lower than 0.1 mT. If the applied induction is higher than 0.25 mT, the magnetic field inside the cylinder strongly increases. This value is close to the field of penetration given by Bean's model, taking a critical current density of 500 A cm{sup -2} measured by the four-probe technique on similar samples.

  15. Static and dynamic magnetic properties of densely packed magnetic nanowire arrays

    DEFF Research Database (Denmark)

    Dmytriiev, O.; Al-Jarah, U.A.S.; Gangmei, P.

    2013-01-01

    and a continuous ferromagnetic thin film. In particular, the competition between anisotropies associated with the shape of the individual nanowires and that of the array as a whole has been studied. Measured and simulated hysteresis loops are largely anhysteretic with zero remanence, and the micromagnetic...... configuration is such that the net magnetization vanishes in directions orthogonal to the applied field. Simulations of the remanent state reveal antiferromagnetic alignment of the magnetization in adjacent nanowires and the formation of vortex flux closure structures at the ends of each nanowire...... and simulation. The resonant frequencies are initially found to decrease as the applied field is increased from remanence. This is the result of a change of mode profile within the plane of the array from nonuniform to uniform as the ground state evolves with increasing applied field. Quantitative differences...

  16. A northwest Atlantic environmental magnetic perspective on the Oligocene - Miocene Transition

    Science.gov (United States)

    van Peer, Tim; Xuan, Chuang; Lippert, Peter; Wilson, Paul; Liebrand, Diederik

    2016-04-01

    The Oligocene - Miocene Transition (OMT) is characterised by a long-term carbon isotope shift and a transient +1‰ oxygen-isotope excursion, the 'Mi1-event'. The Mi1-event has been attributed to transient global cooling and ice sheet expansion on Antarctica, but the boreal component of this major climatic event is poorly understood. The nannofossil oozes recovered at Site U1406 during IODP (Integrated Ocean Drilling Program) Expedition 342 (Paleogene Newfoundland Sediment Drifts) provide an unprecedented opportunity to study the Mi1-event, as these contourite drifts were deposited at 2-6 cm/kyr and are ideally located at the Newfoundland Ridge (northwest Atlantic) below the Deep Western Boundary Current (DWBC). To better understand the combined effects of global cooling, ice sheet formation and global circulation, we generated an environmental magnetic record to study the origin, transportation, deposition and possible diagenesis of magnetic minerals. We carried out continuous high-resolution (1-cm intervals) palaeomagnetic and environmental magnetic analyses across the OMT and present the first continuous environmental magnetic record across Mi1 from a Northern Hemisphere perspective. The geomagnetic polarity stratigraphy interpreted from shore-based u-channel measurements clearly reveals the three C6Cn subchrons spanning the duration of the Mi1-event, and provide a first-order age model for the studied sediment sequence at Site U1406. Rock magnetic experiments conducted at low (down to 20K) and high (up to 700°C) temperatures for selected bulk sediment and magnetic extract samples show the Verwey transition at ~120K, and magnetic components with blocking temperatures at ~250°C and ~580°C. Analysis of isothermal remanent magnetisation (IRM) acquisition curves also indicates the existence of two magnetic components with mean coercivity of ~50 mT and ~400 mT. These observations are consistent with the presence of a fine-grained stoichiometric magnetite component

  17. Localized magnetic fields in arbitrary directions using patterned nanomagnets

    DEFF Research Database (Denmark)

    McNeil, Robert P G; Schneble, Jeff; Kataoka, Masaya

    2010-01-01

    Control of the local magnetic fields desirable for spintronics and quantum information technology is not well developed. Existing methods produce either moderately small local fields or one held orientation. We present designs of patterned magnetic elements that produce remanent fields of 50 m...

  18. Magnetic relaxation behaviour in Pr2NiSi3

    Science.gov (United States)

    Pakhira, Santanu; Mazumdar, Chandan; Ranganathan, R.

    2016-05-01

    Time dependent isothemal remanent magnetizatin (IRM) behaviour for polycrystalline compound Pr2NiSi3 have been studied below its characteristic temperature. The compound undergoes slow magnetic relaxation with time. Along with competing interaction, non-magnetic atom disorder plays an important role in formation of non-equilibrium glassy like ground state for this compound.

  19. Magnetic properties of surficial sediments in Lake Ogawara on the Pacific coast of northeastern Japan: spatial variability and correlation with brackish water stratification

    Science.gov (United States)

    Hayashida, Akira; Nakano, Ryoma; Nagashima, Aya; Seto, Koji; Yamada, Kazuyoshi; Yonenobu, Hitoshi

    2015-10-01

    To examine limnological conditions in Lake Ogawara on the Pacific coast of northwestern Japan, we investigated the magnetic properties of dredged bottom sediment originally collected from the lake in the summer of 2011. We used non-destructive methods to measure the low-field magnetic susceptibility shortly after sampling, and anhysteretic remanent magnetization (ARM) was assessed in 2012 and 2015. The ARM acquisition and demagnetization curves from littoral sites showed several patterns that reflect the provenance of the sediments. At water depths below 10 m, the magnetic susceptibility and ARM of greenish black mud with high organic content decreased considerably with the increase in water depth, but ARM increased slightly at water depths greater than 16 m. We also found that the magnetic concentrations of mud samples were reduced markedly during a period of storage for about 3 years. We attributed these reductions to diagenetic loss of magnetic minerals, which had been enhanced at deeper sites. It is possible that the ARM carriers in deeper areas were derived from authigenic formation of iron sulfide or from deposition of suspended matter in the hypolimnion water. We propose that the magnetic properties of surficial sediments are controlled by limnological stratification of the brackish lake water, thus possibly providing an analog for down-core variations of magnetic parameters associated with the modification of magnetic minerals during reductive diagenesis.

  20. Remanent cell traction force in renal vascular smooth muscle cells induced by integrin-mediated mechanotransduction.

    Science.gov (United States)

    Balasubramanian, Lavanya; Lo, Chun-Min; Sham, James S K; Yip, Kay-Pong

    2013-02-15

    It was previously demonstrated in isolated renal vascular smooth muscle cells (VSMCs) that integrin-mediated mechanotransduction triggers intracellular Ca(2+) mobilization, which is the hallmark of myogenic response in VSMCs. To test directly whether integrin-mediated mechanotransduction results in the myogenic response-like behavior in renal VSMCs, cell traction force microscopy was used to monitor cell traction force when the cells were pulled with fibronectin-coated or low density lipoprotein (LDL)-coated paramagnetic beads. LDL-coated beads were used as a control for nonintegrin-mediated mechanotransduction. Pulling with LDL-coated beads increased the cell traction force by 61 ± 12% (9 cells), which returned to the prepull level after the pulling process was terminated. Pulling with noncoated beads had a minimal increase in the cell traction force (12 ± 9%, 8 cells). Pulling with fibronectin-coated beads increased the cell traction force by 56 ± 20% (7 cells). However, the cell traction force was still elevated by 23 ± 14% after the pulling process was terminated. This behavior is analogous to the changes of vascular resistance in pressure-induced myogenic response, in which vascular resistance remains elevated after myogenic constriction. Fibronectin is a native ligand for α(5)β(1)-integrins in VSMCs. Similar remanent cell traction force was found when cells were pulled with beads coated with β(1)-integrin antibody (Ha2/5). Activation of β(1)-integrin with soluble antibody also triggered variations of cell traction force and Ca(2+) mobilization, which were abolished by the Src inhibitor. In conclusion, mechanical force transduced by α(5)β(1)-integrins triggered a myogenic response-like behavior in isolated renal VSMCs.

  1. The magnetic signature of ultramafic-hosted hydrothermal systems (Invited)

    Science.gov (United States)

    Szitkar, F.; Dyment, J.; Honsho, C.; Horen, H.; Fouquet, Y.

    2013-12-01

    While the magnetic response of basalt-hosted hydrothermal sites is well known, that of ultramafic-hosted hydrothermal sites (UMHS) remains poorly documented. Here we present the magnetic signature of three of the six UMHS investigated to date on the Mid-Atlantic Ridge, i.e. sites Rainbow, Ashadze (1 and 2), and Logachev. Two magnetic signatures are observed. Sites Rainbow and Ashadze 1 are both characterized by a positive reduced-to-the-pole magnetic anomaly, i.e. a positive magnetization contrast. Conversely, sites Ashadze 2 and Logachev do not exhibit any clear magnetic signature. Rock-magnetic measurements on samples from site Rainbow reveal a strong magnetization (~30 A/m adding induced and remanent contributions) borne by sulfide-impregnated serpentinites; the magnetic carrier being magnetite. This observation can be explained by three (non exclusive) processes: (1) higher temperature serpentinization at the site resulting in the formation of more abundant / more strongly magnetized magnetite; (2) the reducing hydrothermal fluid protecting magnetite at the site from the oxidation which otherwise affects magnetite in contact with seawater; and (3) the formation of primary (hydrothermal) magnetite. We apply a new inversion method developed by Honsho et al. (2012) to the high-resolution magnetic anomalies acquired 10 m above seafloor at sites Rainbow and Ashadze 1. This method uses the Akaike Bayesian Information Criterion (ABIC) and takes full advantage of the near-seafloor measurements, avoiding the upward-continuation (i.e. loss of resolution) of other inversion schemes. This inversion reveals a difference in the intensity of equivalent magnetization obtained assuming a 100 m thick magnetic layer, ~30 A/m at site Rainbow and only 8A/m at site Ashadze, suggesting a thinner or less magnetized source for the latter. Hydrothermal sites at Ashadze 2 and Logachev are much smaller (of the order of 10 m) than the previous ones (several 100 m). These sites, known as

  2. Influence of oxygen pressure on critical current density and magnetic flux pinning structures in YBa2Cu3O7-x fabricated by chemical solution deposition

    Institute of Scientific and Technical Information of China (English)

    Ding Fa-Zhu; Gu Hong-Wei; Zhang Teng; Dai Shao-Tao; Xiao Li-Ye

    2011-01-01

    This paper studies the effect of oxygen partial pressure on the fabrication of YBa2Cu3O7-x films on (00/) LaAlO3 substrates by metalorganic deposition using trifluoroacetates (TFA-MOD). As the oxygen partial pressure increases to 1500 Pa, a great increase in the superconducting properties is observed at high magnetic fields parallel to the YBCO c axis. The cross-sectional transmission electron microscope images show that a high density of stacking faults in the size range of 10-15 nm may act as flux pinning centres to enhance the critical current density of the YBCO films

  3. Magnetic domain structures and stray fields of individual elongated magnetite grains revealed by magnetic force microscopy (MFM)

    DEFF Research Database (Denmark)

    Frandsen, Cathrine; Stipp, S. L. S.; McEnroe, S. A.

    2004-01-01

    In order to clarify the relationship between microscopic and macroscopic magnetic features of a rock, we applied magnetic force microscopy (MFM) as a local probe on a sample with an intense natural remanent magnetisation, a norite from Heskestad, Norway. We studied in detail seven magnetite (Fe3O4...

  4. Spectral time-domain induced polarization and magnetic surveying – an efficient tool for characterization of solid waste deposits in developing countries

    DEFF Research Database (Denmark)

    Wemegah, David Dotse; Fiandaca, Gianluca; Auken, Esben

    Time-domain induced polarization (IP) and magnetic data were acquired to map and characterize the decommissioned, un-engineered, municipal solid waste deposit site of the Kwame Nkrumah University of Science and Technology (KNUST), located in the Kumasi Metropolis of Ghana. Thirteen induced...... of the soil and the groundwater system, which is the main potable water supply for the Secondary School, the University Teaching Hospital and the Veterinary School, situated within the catchment area of the site. Full-decay 2-D time-domain IP inversions in terms of Cole-Cole parameters were used...... for interpreting the polarization data. The chargeability, resistivity, and the normalized chargeability distributions, together with the magnetic results, aided in a full characterization of the site geology, the waste and the associated pollution plume. In particular, clear contrasts in resistivity...

  5. Nanozeolite-LTL with Gd(III) deposited in the large and Eu(III) in the small cavities as a magnetic resonance optical imaging probe.

    Science.gov (United States)

    Mayer, Florian; Zhang, Wuyuan; Brichart, Thomas; Tillement, Olivier; Bonnet, Célia S; Tóth, Éva; Peters, Joop A; Djanashvili, Kristina

    2014-03-17

    The immense structural diversity of more than 200 known zeolites is the basis for the wide variety of applications of these fascinating materials ranging from catalysis and molecular filtration to agricultural uses. Despite this versatility, the potential of zeolites in medical imaging has not yet been much exploited. In this work a novel strategy is presented to selectively deposit different ions into distinct framework locations of zeolite-LTL (Linde type L) and it is demonstrated that the carefully ion-exchanged Gd/Eu-containing nanocrystals acquire exceptional magnetic properties in combination with enhanced luminescence. This smart exploitation of the framework structure yields the highest relaxivity density (13.7 s(-1)  L g(-1) at 60 MHz and 25 °C) reported so far for alumosilicates, rendering these materials promising candidates for the design of dual magnetic resonance/optical imaging probes, as demonstrated in preliminary phantom studies.

  6. Thickness-modulated tungsten–carbon superconducting nanostructures grown by focused ion beam induced deposition for vortex pinning up to high magnetic fields

    Directory of Open Access Journals (Sweden)

    Ismael García Serrano

    2016-11-01

    Full Text Available We report efficient vortex pinning in thickness-modulated tungsten–carbon-based (W–C nanostructures grown by focused ion beam induced deposition (FIBID. By using FIBID, W–C superconducting films have been created with thickness modulation properties exhibiting periodicity from 60 to 140 nm, leading to a strong pinning potential for the vortex lattice. This produces local minima in the resistivity up to high magnetic fields (2.2 T in a broad temperature range due to commensurability effects between the pinning potential and the vortex lattice. The results show that the combination of single-step FIBID fabrication of superconducting nanostructures with built-in artificial pinning landscapes and the small intrinsic random pinning potential of this material produces strong periodic pinning potentials, maximizing the opportunities for the investigation of fundamental aspects in vortex science under changing external stimuli (e.g., temperature, magnetic field, electrical current.

  7. Discharge regime of non-ambipolarity with a self-induced steady-state magnetic field in plasma sources with localized radio-frequency power deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shivarova, A., E-mail: ashiva@phys.uni-sofia.bg; Lishev, St.; Todorov, D.; Paunska, Ts. [Faculty of Physics, Sofia University, BG-1164 Sofia (Bulgaria)

    2015-10-15

    Involving the idea for the Biermann effect known from space physics as well as recent discussions on non-ambipolarity of the electron and ion fluxes in low-pressure discharges, the study builds the discharge pattern in a source with localized RF power deposition outside the region of high electron density. A vortex dc current flowing in an RF discharge and a steady-state magnetic field induced by this current govern the discharge behavior. Owing to a shift in the positions of the electron-density and plasma-potential maxima, the dc current is driven with the purpose of keeping the conservativity of the dc field in the discharge. The results present the spatial structure of a discharge in a regime of non-ambipolarity of the electron and ion fluxes, including its modifications by the magnetic field.

  8. Magnetic and electrical characterization of nickel-rich NiFe thin films synthesized by atomic layer deposition and subsequent thermal reduction

    Science.gov (United States)

    Espejo, A. P.; Zierold, R.; Gooth, J.; Dendooven, J.; Detavernier, C.; Escrig, J.; Nielsch, K.

    2016-08-01

    Nickel-rich NiFe thin films (Ni92Fe8, Ni89Fe11 and Ni83Fe17) were prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. In order to obtain Ni x Fe1-x O y films, one ALD supercycle was performed according to the following sequence: m NiCp2/O3, with m = 1, 2 or 3, followed by one FeCp2/O3 cycle. The supercycle was repeated n times. The thermal reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. The metallic nickel iron alloy thin films were investigated and characterized with respect to crystallinity, morphology, resistivity, and magnetism. As proof-of-concept magnetic properties of an array of Ni83Fe17, close to the perfect Permalloy stoichiometry, nanotubes and an isolated tube were investigated.

  9. Facile synthesis and magnetic study of Ni@polyamide 66 coaxial nanotube arrays

    Science.gov (United States)

    Li, Xiaoru; Yang, Chao; Han, Ping; Zhao, Qingpei; Song, Guojun

    2016-12-01

    Ni@polyamide 66 (PA66) core/shell coaxial double-layer nanotube arrays have been prepared in the nanopores of anodic aluminum oxide templates (AAO). The shell of PA66 nanotubes were formed first and then served as templates to deposit Ni nanotubes used as the core. The morphology, structures of the obtained arrays were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The formation of this unique coaxial nanotube structure was confirmed by SEM and TEM images and X-ray diffraction (XRD). We further explored the magnetic properties of the obtained coaxial nanotube arrays with vibrating sample magnetometer (VSM) and found that Ni@PA66 coaxial nanotubes exhibited higher remanence ratio than that of Ni nanotubes. These Ni@PA66 coaxial nanotubes are promising to be used as templates to fill in other materials.

  10. Magnetic properties related to thermal treatment of pyrite

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air atmospheres. In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ~20 and ~30 mT, respectively. Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ~1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→ pyrrhotite→magnetite→hematite. These results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

  11. Magnetic properties related to thermal treatment of pyrite

    Institute of Scientific and Technical Information of China (English)

    WANG Lei; PAN YongXin; LI JinHua; QIN HuaFeng

    2008-01-01

    Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air atmospheres. In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ~20 and ~30 mT, respectively.Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ~1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→pyrrhotite→magnetite→hematite. These results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

  12. Tunable magnetism on the lateral mesoscale by post-processing of Co/Pt heterostructures

    Directory of Open Access Journals (Sweden)

    Oleksandr V. Dobrovolskiy

    2015-04-01

    Full Text Available Controlling magnetic properties on the nanometer-scale is essential for basic research in micro-magnetism and spin-dependent transport, as well as for various applications such as magnetic recording, imaging and sensing. This has been accomplished to a very high degree by means of layered heterostructures in the vertical dimension. Here we present a complementary approach that allows for a controlled tuning of the magnetic properties of Co/Pt heterostructures on the lateral mesoscale. By means of in situ post-processing of Pt- and Co-based nano-stripes prepared by focused electron beam induced deposition (FEBID we are able to locally tune their coercive field and remanent magnetization. Whereas single Co-FEBID nano-stripes show no hysteresis, we find hard-magnetic behavior for post-processed Co/Pt nano-stripes with coercive fields up to 850 Oe. We attribute the observed effects to the locally controlled formation of the CoPt L10 phase, whose presence has been revealed by transmission electron microscopy.

  13. Electrochemical deposition of diluted magnetic semiconductor ZnMnSe{sub 2} on reduced graphene oxide/polyimide substrate and its properties

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Lingpu; Yu, Shengjiao; Jiang, Yimin; Wang, Chunming, E-mail: wangcm@lzu.edu.cn

    2014-10-01

    Highlights: • The flexible reduced graphene/polyimide conductive substrate was made. • The ZnMnSe{sub 2} semiconductor has special porous structure. • The ZnMnSe{sub 2} has remarkable photoelectric property, the potential difference is 0.27 V. • The semiconductor ZnMnSe{sub 2} has magnetism, and the M{sub s} is 1.53 emu cm{sup −3}. - Abstract: Diluted magnetic semiconductor ZnMnSe{sub 2} has been synthesized on reduced graphene oxide/polyimide (rGO/PI) substrate by a simple electrochemical method. The structure, surface morphology, magnetism and photoelectric property of ZnMnSe{sub 2} were examined. For comparison, ZnSe and MnSe were also prepared by electrochemical deposition. Porous structure of ZnMnSe{sub 2} was obtained, and the porous structure was consisted of nanosheets. The atomic ratio of Zn, Mn and Se was measured to be 1:1:2 by X-ray photoelectron spectra and energy-dispersive X-ray spectroscopy. The high resolution transmission electron microscopy and X-ray Powder Diffraction pattern confirmed the preferred crystal growth orientation was the (1 1 1) direction. The absorption spectrum provided a band gap of 2.4 eV. Open-circuit potential measurement indicated that ZnMnSe{sub 2} composite film was a good p-type semiconductor material. The photoelectrical phenomena of ZnSe, MnSe and ZnMnSe{sub 2} were observed, and the optoelectronic property of ZnMnSe{sub 2} was the best, the potential difference was 0.27 V. Besides, the ZnMnSe{sub 2} composite film had prominent magnetism, and it was ferromagnetism material. These results indicated that rGO/PI–ZnMnSe{sub 2} composite film by electrochemical deposition was a promising ferromagnetism semiconductor.

  14. Magnetic domain structure and magnetization reversal in submicron-scale Co dots

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, A., LLNL

    1998-02-17

    We present a magnetic force microscopy (MFM) analysis of arrays of submicron-scale Co dots fabricated by interference lithography. The dots are thin (180-300 A) and are elliptical in shape. MFM of these structures reveals that they relax into highly ordered remanent states whose symmetry and configuration are governed by their shape anisotropy. In particular, when the dots are saturated along the easy-axis, a uniformly magnetized state persists at remanence. However, when the dots are saturated in hard-axis, they relax into a single-vortex state in which the circulation can have either sign. Both remanent states are characterized by smoothly varying magnetization patterns and a high degree of uniformity across the array. We attribute the ordered behavior of these structures to the film microstructure, which allows the shape anisotropy to dominate over magnetocrystalline anisotropy. By imaging a series of minor-loop remanent states, we show that magnetization reversal in these structures occurs via the nucleation and annihilation of a single vortex. Magnetic hysteresis loop measurements are consistent with these observations and provide additional details. Furthermore, we present the results of micromagnetic simulations, which are in excellent agreement with both the MFM images and the hysteresis loop measurements.

  15. Structural, optical and magnetic properties of Mn doped ZnO thin films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Aravind, Arun, E-mail: aruncusat@gmail.com [Nanophotonic and Optoelectronic Devices Laboratory, Department of Physics, Cochin University of Science and Technology, Kochi 682 022, Kerala (India); Jayaraj, M.K., E-mail: mkj@cusat.ac.in [Nanophotonic and Optoelectronic Devices Laboratory, Department of Physics, Cochin University of Science and Technology, Kochi 682 022, Kerala (India); Kumar, Mukesh; Chandra, Ramesh [Nano Science Laboratory, Institute Instrumentation Centre, IIT Roorkee, Roorkee 247 667, Uttarakhand (India)

    2012-08-01

    Highlights: Black-Right-Pointing-Pointer Defect induced Raman active modes in Mn doped ZnO thin films. Black-Right-Pointing-Pointer Room temperature ferromagnetism. Black-Right-Pointing-Pointer Morphological variations of ZnO thin films with Mn doping. Black-Right-Pointing-Pointer Variation of refractive index of ZnO thin films with Mn doping. - Abstract: Zn{sub 1-x}Mn{sub x}O thin films were grown by pulsed laser deposition. The phase purity and the structure were confirmed by X-ray diffraction studies. The films have a transmittance more than 80% in the visible region. The refractive index of Zn{sub 0.90}Mn{sub 0.10}O films is found to be 1.77 at 550 nm. The presence of non-polar E{sub 2}{sup high} and E{sub 2}{sup low} Raman modes in thin films indicates that 'Mn' doping does not change the wurtzite structure of ZnO. Apart from the normal modes of ZnO the Zn{sub 1-x}Mn{sub x}O ceramic targets show two additional modes at 332 cm{sup -1} (I{sub 1}) and 524 cm{sup -1} (I{sub 2}). The broad Raman peaks (340-600 cm{sup -1}) observed Zn{sub 0.90}Mn{sub 0.10}O thin films can be deconvoluted into five peaks, denoted as P{sub 1}-P{sub 5}. The possible origins of Raman peaks in Zn{sub 1-x}Mn{sub x}O films are the structural disorder and morphological change caused by the Mn dopant. The B{sub 1}{sup low}, {sup 2}B{sub 1}{sup low}, B{sub 1}{sup high} and A{sub 1}{sup LO} modes as well as the surface phonon mode have been observed in heavily Mn-doped ZnO films. Zn{sub 0.98}Mn{sub 0.02}O thin film shows room temperature ferromagnetism. The saturation magnetic moment of the Zn{sub 0.98}Mn{sub 0.02}O thin film is 0.42{mu}{sub B}/Mn atom. The undoped ZnO film prepared under the same condition shows diamagnetic nature. At higher doping concentrations the formation of Mn clusters suppress the room temperature ferromagnetism in Zn{sub 1-x}Mn{sub x}O thin films and shows paramagnetism. XPS confirms the incorporation of Mn{sup 2+} into the ZnO lattice.

  16. Gamma spectrometric and magnetic interpretation of Cabaçal copper deposit in Mato Grosso (Brazil): Implications for hydrothermal fluids remobilization

    Science.gov (United States)

    Ribeiro, Vanessa Biondo; Mantovani, Marta Silvia Maria

    2016-12-01

    The Cabaçal Au-Zn-Cu Deposit, Mato Grosso, Brazil, was explored between 1987 and 1991, when 869,279 tons of ore rich in Au and Cu have been extracted. The hydrothermal alteration in the Cabaçal mine suggests a volcanogenic genetic model in which hydrothermal centers generated sericitization, chloritization and silicification alterations at different stages. The hydrothermal alteration affects the radioelements in different ways, generating a characteristic gamma spectrometric signature for the affected area. The eTh/K ratio map evidenced that the hydrothermalized area extends beyond south limits of the Cabaçal gabbro dykes formation, which host Cabaçal and Santa Helena mines. Magnetic data over the region show the same behavior for this formation, indicating that the magnetic source extends in subsurface. This behavior was recovered by the 3D model inverted for the region, which recovered a positive apparent magnetic contrast associated with this body, with an increasing deepness to south. It is possible that the south subsurface portion of the magnetic source may contain economic concentrations of Au remobilized by hydrothermal fluids. However, to confirm this hypothesis it is necessary to develop geochemical and borehole analysis of the area.

  17. Magnetic crustal thickness in Greenland from CHAMP and Ørsted data

    DEFF Research Database (Denmark)

    Maule, Cathrine Fox; Purucker, Michael E.; Olsen, Nils

    2005-01-01

    and observatory data. After correcting for the remanent magnetization, we determine the vertically integrated magnetization of the crust. Making some simplifying assumptions about the susceptibility, the thickness of the magnetic crust is determined by iteratively improving an initial crustal thickness model...

  18. Effects of magnetic field heat treatment on Sm–Co/α-Fe nanocomposite permanent magnetic materials prepared by high energy ball milling

    Energy Technology Data Exchange (ETDEWEB)

    Su, Yanfeng [Faculty of Science, Ningbo University, Ningbo 315211 (China); Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Su, Hao [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhu, Yuejin [Faculty of Science, Ningbo University, Ningbo 315211 (China); Wang, Fang [School of Materials Science and Engineering, NingBo University of Technology, Ningbo, Zhe Jiang Province (China); Du, Juan; Xia, Weixing; Yan, Aru; Liu, J. Ping [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhang, Jian, E-mail: zhangj@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2015-10-25

    Effects of magnetic field heat treatment on the structure and magnetic properties of Sm–Co/α-Fe nanocomposite permanent magnetic materials fabricated by high energy ball milling are investigated in the present work. After a magnetic field heat treatment below 700 °C on as-milled amorphous Sm–Co/α-Fe samples, the nanocomposite magnets with strong hard and soft magnetic interaction, showing a hysteresis loop of single phase characteristic, are obtained. The coercivity increases with the increase of annealing temperature. The coercivity, remanence and remanence ratio of the Sm–Co/Fe nanocomposite magnets are all enhanced after a heat treatment at a magnetic field as compared with those of nanocomposite magnets heat treated without a magnetic field. X ray diffraction analysis shows that the diffusion between the Sm–Co hard and α-Fe soft phases is suppressed by the magnetic field applied during the heat treatment process, leading to the inhibition of the grain growth of nanocrystal Sm–Co and α-Fe phases, and a finer nanostructure is obtained. Thus, a higher coercivity, remanence and remanence ratio are realized in Sm–Co/α-Fe nanocomposite magnets after the magnetic field heat treatment. Magnetic field heat treatment also makes the direction of c axis of Sm–Co hard grains along the heat treatment magnetic field direction, leading to an enhancement of magnetic anisotropy of the Sm–Co/Fe nanocomposite magnets. - Highlights: • Effects of magnetic field heat treatment on SmCo{sub 5}/Fe magnets were investigated. • Magnetic properties are improved obviously after magnetic field heat treatment. • The reasons for the improvement of magnetic properties were discussed. • The results are significant for fabrication of anisotropic nanocomposite magnets.

  19. Visualized effect of oxidation on magnetic recording fidelity in pseudo-single-domain magnetite particles

    DEFF Research Database (Denmark)

    Almeida, Trevor P.; Kasama, Takeshi; Muxworthy, Adrian R.

    2014-01-01

    fidelity of Fe3O4 particles is greatly diminished over time by progressive oxidation to less magnetic iron oxides, such as maghemite (γ-Fe2O3), with consequent alteration of remanent magnetization potentially having important geological significance. Here we use the complementary techniques...... of environmental transmission electron microscopy and off-axis electron holography to induce and visualize the effects of oxidation on the magnetization of individual nanoscale Fe3O4 particles as they transform towards γ-Fe2O3. Magnetic induction maps demonstrate a change in both strength and direction of remanent...

  20. Rock magnetic properties and palaeomagnetic results of sediments from a stone implement layer in the Bose Basin, Guangxi

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Directional samples were taken to study rock magnetism and palaeomagnetic records from the Dong- sheng profile, which is 5 m thick and on the northwest edge of the Bose Basin. Mineralogy and rock magnetism of typical samples indicate that coarse granular titanomagnetite, and fine-grained hematite, superparamagnetic maghemite formed by pedogenesis are in the sediment, which has undergone many transformative processes during different stages of pedogenesis. Parallel samples were taken for thermal demagnetization (TH) (0 to 680℃) and alternating field (AF) demagnetization (0 to 80 mT) respectively. Experimental results of these two kinds of demagnetization illustrate that there are two or more magnetic components in the samples. Intensity of NRM decreases by almost 60% to 90% rapidly when the temperature ranges from 100℃ to 350℃, with a steady magnetic component. It is impossible to analyze the magnetic components at high temperature because those fluctuate widely when the temperature is higher than 400℃. Steady magnetic components from 100℃ to 350℃ indicate that the remanence was mainly carried by fine-grained hematite formed by pedogenesis, reflecting a change in the geomagnetic field while the magnetite was being oxidized into hematite by chemical weathering after deposition. The formative age of the sediments cannot be obtained by magnetic methods in this profile.

  1. Rock magnetic properties and palaeomagnetic results of sediments from a stone implement layer in the Bose Basin, Guangxi

    Institute of Scientific and Technical Information of China (English)

    YANG XiaoQiang; ZHU ZhaoYu; ZHANG YiNan; LI HuaMei; ZHOU WenJuan; YANG Jie

    2008-01-01

    Directional samples were taken to study rock magnetism and palaeomagnetic records from the Dongsheng profile, which is 5 m thick and on the northwest edge of the Bose Basin. Mineralogy and rock magnetism of typical samples indicate that coarse granular titanomagnetite, and fine-grained hematite,superparamagnetic maghemite formed by pedogenesis are in the sediment, which has undergone many transformative processes during different stages of pedogenesis. Parallel samples were taken for thermal demagnetization (TH) (0 to 680℃) and alternating field (AF) demagnetization (0 to 80 mT)respectively. Experimental results of these two kinds of demagnetization illustrate that there are two or more magnetic components in the samples. Intensity of NRM decreases by almost 60% to 90% rapidly when the temperature ranges from 100℃ to 350℃, with a steady magnetic component. It is impossible to analyze the magnetic components at high temperature because those fluctuate widely when the temperature is higher than 400℃. Steady magnetic components from 100℃ to 350℃ indicate that the remanence was mainly carried by fine-grained hematite formed by pedogenesis, reflecting a change in the geomagnetic field while the magnetite was being oxidized into hematite by chemical weathering after deposition. The formative age of the sediments cannot be obtained by magnetic methods in this profile.

  2. Magnetic studies on Shergotty and other SNC meteorites

    Science.gov (United States)

    Cisowski, S. M.

    1986-01-01

    The results of a study of basic magnetic properties of meteorites within the SNC group, including the four known shergottites and two nakhlites, are presented. An estimate is made of the strength of the magnetic field which produced the remanent magnetization of the Shergotty meteorite, for the purpose of constraining the choices for the parent body of these SNC meteorites. Remanence measurements in several subsamples of Shergotty and Zagami meteorites reveal a large variation in intensity that does not seem to be related to the abundance of remanence carriers. The other meteorites carry only weak remanence, suggesting weak magnetizing fields as the source of their magnetic signal. A paleointensity experiment on a weakly magnetized subsample of Shergotty revealed a low temperature component of magnetization acquired in a field of 2000 gammas, and a high temperature component reflecting a paleofield strength of between 250 and 1000 gammas. The weak field environment that these meteorites seem to reflect is consistent with either a Martian or asteroidal origin, but inconsistent with a terrestrial origin.

  3. Effect of ethylene glycol on the orientation and magnetic properties of barium ferrite thin films derived by chemical solution deposition

    KAUST Repository

    Meng, Siqin

    2014-03-01

    Tb-doped BiFeO3 multiferroics nanoparticles fabricated via micro-emulsion route were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The fully characterized TbxBi1-xFeO3 nanoparticles were then subjected to magnetic behavior evaluation for various technological applications. The thermogravimetric analysis (TGA) conducted in the range 25-1000 degrees C predicted the temperature (similar to 960 degrees C) for phase formation. XRD estimated the crystallite size 30-47 nm, while the particles size estimated by SEM was found (80-120 nm). The XRD data confirmed the rhombohedral (space group R3c) phase with average cell volume 182.66 angstrom(3) (for BiFeO3). Various other physical parameters like bulk density, X-ray density and porosity were also determined from the XRD data and found in agreement with theoretical predictions. The magnetic studies showed that as Bi3+ was substituted by Tb3+, all magnetic parameters were altered. The maximum saturation magnetization (M-s) (0.6691 emug(-1)) was exhibited by Tb0.02Bi0.98FeO3 while the Tb0.00Bi1.00Fe1.00O3 showed the maximum (549 Oe) coercivity. The evaluated magnetic behavior categorized these materials as soft magnetic materials that may be useful for fabricating advanced technological applications. (C) 2013 Elsevier B.V. All rights reserved.

  4. Direct liquid phase deposition fabrication of waxberry-like magnetic Fe{sub 3}O{sub 4}@TiO{sub 2} core-shell microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jian, E-mail: zhengjian@swust.edu.cn [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Wu, You; Zhang, Quanping; Li, Yintao [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Wang, Chengyang [Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching (Germany); Zhou, Yuanlin, E-mail: zhouyuanlin@swust.edu.cn [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China)

    2016-09-15

    Magnetic Fe{sub 3}O{sub 4}@TiO{sub 2} core-shell microspheres are ideally applied in several specific fields due to their unique properties. A facile liquid phase deposition route for the fabrication of Fe{sub 3}O{sub 4}@TiO{sub 2} core-shell microspheres was developed. The core-shell structure was obtained by direct deposition of TiO{sub 2} on the surface of Fe{sub 3}O{sub 4} microspheres. The prepared products were characterized by using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The waxberry-like microspheres were nearly spherical with diameters of about 500 nm and average shell thickness of 80 nm. The shell layer was composed of smaller primary TiO{sub 2} nanoparticles with sizes from 10 to 20 nm. A possible growth mechanism of the core-shell structure was proposed. The photo-catalytic decomposition of methylene blue and the recycling of prepared core-shell microspheres were also investigated. - Highlights: • Waxberry-like core-shell Fe3O4@TiO2 microspheres were fabricated by facile LPD route. • They have considerable saturation magnetization and small coercivity. • They can be used as recyclable photocatalyst for removal of dyestuff in aqueous solution. • The growth mechanism of the core-shell structure was proposed.

  5. Controlled co-deposition of FePt nanoparticles embedded in MgO: a detailed investigation of structure and electronic and magnetic properties

    Science.gov (United States)

    D'Addato, S.; Grillo, V.; di Bona, A.; Luches, P.; Frabboni, S.; Valeri, S.; Lupo, P.; Casoli, F.; Albertini, F.

    2013-12-01

    Films of FePt nanoparticles (NPs) embedded in MgO were obtained by controlled co-deposition of FePt NPs pre-formed by a gas aggregation source and of Mg evaporated in an oxygen atmosphere. Assemblies of core-shell FePt@MgO NPs and films of FePt NPs embedded in MgO matrix could be obtained by varying FePt and Mg deposition rates. Transmission electron microscopy (TEM) and high resolution-TEM revealed the core-shell structure of the NPs, with an FePt core (of average diameter = 4.75 nm) presenting a multitwinned icosahedral structure, and MgO partially in crystalline form. The functional effect of the MgO shell in shielding the FePt core from external oxidation was shown with XPS. Upon controlled annealing, a transition from A1 to L10 ordering could be obtained, with structural and morphological re-arrangement. The magnetic hysteresis loops obtained from alternating gradient field magnetometry at room temperature show a ‘wasp-waist’ shape, with small values of coercive field (Hc = 300-1400 Oe), decreasing at increasing amounts of co-deposited MgO.

  6. Controlled co-deposition of FePt nanoparticles embedded in MgO: a detailed investigation of structure and electronic and magnetic properties.

    Science.gov (United States)

    D'Addato, S; Grillo, V; di Bona, A; Luches, P; Frabboni, S; Valeri, S; Lupo, P; Casoli, F; Albertini, F

    2013-12-13

    Films of FePt nanoparticles (NPs) embedded in MgO were obtained by controlled co-deposition of FePt NPs pre-formed by a gas aggregation source and of Mg evaporated in an oxygen atmosphere. Assemblies of core-shell FePt@MgO NPs and films of FePt NPs embedded in MgO matrix could be obtained by varying FePt and Mg deposition rates. Transmission electron microscopy (TEM) and high resolution-TEM revealed the core-shell structure of the NPs, with an FePt core (of average diameter (d) = 4.75 nm) presenting a multitwinned icosahedral structure, and MgO partially in crystalline form. The functional effect of the MgO shell in shielding the FePt core from external oxidation was shown with XPS. Upon controlled annealing, a transition from A1 to L10 ordering could be obtained, with structural and morphological re-arrangement. The magnetic hysteresis loops obtained from alternating gradient field magnetometry at room temperature show a 'wasp-waist' shape, with small values of coercive field (Hc = 300-1400 Oe), decreasing at increasing amounts of co-deposited MgO.

  7. Superhard carbon deposited by pulsed high-current arc as protective nanocoating for magnetic hard disks; Superharter Kohlenstoff abgeschieden mit gepulstem Hochstrombogen als Nanoschutzschicht fuer Magnetspeicherplatten

    Energy Technology Data Exchange (ETDEWEB)

    Neuhaeuser, M.; Hilgers, H. [IBM Mainz (Germany). Abt. 4627; Witke, T. [Infenion Dresden (Germany). Bereich PVD; Siemroth, P. [Fraunhofer-Institut fuer Werkstoffphysik und Schichttechnologie (IWS), Dresden (Germany)

    2001-08-01

    Superhard amorphous carbon films (ta-C) deposited by pulsed high-current arc (HCA) possess a good perspective to be used as future ultrathin protective coatings for magnetic hard disks. The ta-C coatings meet all demands concerning the mechanical, chemical and tribological properties required for corrosion and wear protective coatings with thicknesses of 2-3 nm. From the current point of view the deposition technique also qualifies for an industrial mass production. Consequently there is a very good prospect that in near future the high-current arc technique will be the method of choice for carbon deposition in industrial hard disk drive production. (orig.) [German] Superharte amorphe Kohlenstoffschichten (ta-C), die mit gepulstem Hochstrombogen (high-current arc, HCA) abgeschieden werden, besitzen ein hohes Potential als zukuenftige ultraduenne Schutzschichten fuer Magnetspeicherplatten. Die ta-C-Schichten erfuellen alle wesentlichen Anforderungen, die in mechanischer, chemischer und tribologischer Hinsicht an 2-3 nm dicke Verschleiss- und Korrosionsschutzschichten gestellt werden. Auch die Beschichtungstechnik ist aus jetziger Sicht fuer die Massenproduktion geeignet. Damit bestehen sehr gute Aussichten, dass in naher Zukunft die Hochstrombogenverdampfung die Methode der Wahl fuer die Kohlenstoffabscheidung in der industriellen Festplattenproduktion darstellt. (orig.)

  8. Magnetic signature of river sediments drained into the southern and eastern part of the South China Sea (Malay Peninsula, Sumatra, Borneo, Luzon and Taiwan)

    Science.gov (United States)

    Kissel, Catherine; Liu, Zhifei; Li, Jinhua; Wandres, Camille

    2017-01-01

    Magnetic properties of 22 river samples collected in the Malay Peninsula, Sumatra, Borneo, Luzon and Taiwan have been investigated in order to magnetically characterize the sediments drained and deposited into the South China Sea. The geological formations as well as the present climatic conditions are different from one region to another. Laboratory analyses include low-field magnetic susceptibility, anhysteretic (ARM) and isothermal (IRM) remanent magnetizations acquisition and decay, back-field acquisition, thermal demagnetization of three-axes IRM, hysteresis cycles and low-temperature magnetic measurements. The magnetic properties indicate that the sediments are a mixture of hematite, magnetite and pyrrhotite in different proportions depending on the region. Combined with results previously reported for the three main Asian rivers (Pearl, Red and Mekong rivers), the new data indicate that, in general, hematite-rich sediments are delivered to the southern basin of the South China Sea while the northern basin is fed with magnetite and pyrrhotite-rich sediments. In addition to this general picture, some variability is observed at smaller geographic scales. Indeed, the magnetic assemblages are closely related to the geology of the various catchments while clay minerals, previously reported for the same samples, are more representative of the climatic conditions under which the parent rocks have evolved within each catchment. The magnetic fraction, now well characterized in the main river sediments drained into the South China Sea, can be used as a tracer for changes in precipitation on land and in oceanic water mass transport and exchange.

  9. Designing a magnet for magnetic refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Bjoerk, R.

    2010-03-15

    This thesis investigates the design and optimization of a permanent magnet assembly for use in a magnetic refrigeration device. The heart of magnetic refrigeration is the adiabatic temperature change in the magnetocaloric material which is caused by the magnetic field. In order to design an ideal magnet assembly the magnetocaloric materials and the refrigeration process itself and their properties and performance as a function of magnetic field are investigated. For the magnetocaloric materials it is the magnetization, specific heat capacity and adiabatic temperature that are investigated as functions of the magnetic field. Following this the process utilized by a magnetic refrigerator to provide cooling is investigated using a publicly available one dimensional numerical model. This process is called active magnetic regeneration (AMR). The aim is to determine the performance of the AMR as a function of the magnetic field in order to learn the properties of the optimal magnet assembly. The performance of the AMR as a function of the synchronization and width of the magnetic field with respect to the AMR cycle, the ramp rate and maximum value of the magnetic field are investigated. Other published magnet designs used in magnetic refrigeration devices are also evaluated, using a figure of merit based on the properties of the investigated magnetocaloric materials, to learn the properties of the best magnet designs to date. Following this investigation the Halbach cylinder, which is a hollow permanent magnet cylinder with a rotating remanent flux density, is investigated in detail as it forms the basis of many magnet designs used in magnetic refrigeration. Here the optimal dimensions of a Halbach cylinder, as well as analytical calculations of the magnetic field for a Halbach cylinder of infinite length, are presented. Once it has been determined which properties are desirable for a magnet used in magnetic refrigeration the design of a new magnet is described. This is

  10. Microstructure and magnetic properties of very thin CoCr films deposited on different underlayers by RF-sputtering

    NARCIS (Netherlands)

    Pan, G.; Mapps, D.J.; Akhter, M.A.; Lodder, J.C.; Berge, ten P.; Wong, H.Y.; Chapmann, J.N.

    1992-01-01

    Very thin CoCr films deposited on different underlayers on glass disk substrates were studied by the magneto-optic Kerr effect, VSM, torque magnetometry and TEM selected area diffraction. Square or near square perpendicular loops were obtained from Co/Ti, CoCr/Au, CoCr/Al, CoCr/C and CoCr/Si films.

  11. Magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion, Rogaland, southern Norway: Mineral sources and geological significance

    Science.gov (United States)

    Biedermann, Andrea R.; Heidelbach, Florian; Jackson, Mike; Bilardello, Dario; McEnroe, Suzanne A.

    2016-10-01

    Magnetic anisotropy can provide important information about mineral fabrics, and thus magmatic processes, particularly when it is known how multiple mineral species contribute to the anisotropy. It may also affect the direction of induced or remanent magnetization, with important consequences for paleomagnetic studies or the interpretation of magnetic anomalies. Here, we aim at describing the magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion and identifying their carriers. Anisotropies of magnetic susceptibility and remanence were measured on samples covering different geographic locations and stratigraphic units within the Bjerkreim Sokndal Layered Intrusion. The intrusion is characterized by magmatic layering and has a synform structure, with strong foliation on the limbs. Detailed comparison between magnetic and mineral fabric shows that they are not necessarily coaxial, but the minimum susceptibility, and minimum anhysteretic remanence are generally normal to the foliation or the magmatic layering. The minimum susceptibility and anhysteretic remanence are associated with pyroxene (100) axes, and the maximum susceptibility and anhysteretic remanence are sub-parallel to the pyroxene [001] axes in layers MCU IVc and MCU IVe for which electron backscatter data are available. However, the paramagnetic anisotropy of pyroxene is too weak to explain the observed anisotropy. We propose that the magnetic anisotropy of magnetite-free specimens is carried by hemo-ilmenite exsolutions within pyroxene, in addition to pyroxene itself. When present, multi-domain magnetite dominates both the anisotropy of magnetic susceptibility and anhysteretic remanence, due to shape-preferred orientation and distribution anisotropy. The orientation of the magnetic fabric appears independent of carrier, due to their common deformation history, but the degree of anisotropy is stronger for magnetite-bearing specimens. The results of this study will facilitate future structural

  12. Influences of urban fabric on pyroclastic density currents at Pompeii (Italy): 2. Temperature of the deposits and hazard implications

    Science.gov (United States)

    Zanella, E.; Gurioli, L.; Pareschi, M. T.; Lanza, R.

    2007-05-01

    During the A.D. 79 eruption of Vesuvius, Italy, the Roman town of Pompeii was covered by 2.5 m of pyroclastic fall pumice and then partially destroyed by pyroclastic density currents (PDCs). Thermal remanent magnetization measurements performed on the lithic and roof tile fragments embedded in the PDC deposits allow us to quantify the variations in the temperature (Tdep) of the deposits within and around Pompeii. These results reveal that the presence of buildings strongly influenced the deposition temperature of the erupted products. The first two currents, which entered Pompeii at a temperature around 300-360°C, show drastic decreases in the Tdep, with minima of 100-140°C, found in the deposits within the town. We interpret these decreases in temperature as being the result of localized interactions between the PDCs and the city structures, which were only able to affect the lower part of the currents. Down flow of Pompeii, the lowermost portion of the PDCs regained its original physical characteristics, emplacing hot deposits once more. The final, dilute PDCs entered a town that was already partially destroyed by the previous currents. These PDCs left thin ash deposits, which mantled the previous ones. The lack of interaction with the urban fabric is indicated by their uniform temperature everywhere. However, the relatively high temperature of the deposits, between 140 and 300°C, indicates that even these distal, thin ash layers, capped by their accretionary lapilli bed, were associated with PDCs that were still hot enough to cause problems for unsheltered people.

  13. Dependence of magnetic properties, texture and residual stresses on the deposition parameters of CoFe - single and multi - layers

    Energy Technology Data Exchange (ETDEWEB)

    Dieter, S.; Wanderka, N. [Hahn-Meitner-Inst. Berlin, Berlin (Germany); Pyzalla, A.; Reimers, W. [Hahn-Meitner-Inst. Berlin, Berlin (Germany); TU Berlin, Inst. fuer Werkstoffwissenschaften und -technologien, Berlin (Germany); Seemann, K. [Forschungszentrum Karlsruhe, Inst. fuer Materialforschung I (Germany)

    2002-07-01

    For electronic devices thin magnetic single and multi - layers, with a thickness below 2 {mu}m are increasingly used. The magnetic properties of the thin magnetic layers depend on their chemical composition, layer thickness, homogeneity and roughness as well as on the texture and the residual stress state. Layer thickness, homogeneity, roughness, texture and residual stress state essentially are determined by the process parameters of the manufacturing process. Here the dependence of the layer characteristics and their texture and residual stress state on the process parameters sputter power and argon partial pressure is investigated using transmission electron microscopy and diffraction methods and relations between texture and residual stress values of the layers and coercivity are shown. (orig.)

  14. MAGNET

    CERN Multimedia

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  15. Effect of zinc doping on the structural and magnetic properties of nickel ferrite thin films fabricated by pulsed laser deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Raghavender, A.T., E-mail: raghavi9@gmail.com [Nanomagnetism Laboratory, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Hoa Hong, Nguyen, E-mail: nguyenhong@snu.ac.kr [Nanomagnetism Laboratory, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Chikoidze, Ekaterina; Dumont, Yves [Laboratoire GeMAC, UMR 8635 CNRS—Université de Versailles, 45 Avenue des Etats-Unis, 78035 Versailles Cedex (France); Kurisu, Makio [Department of Physics, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan)

    2015-03-15

    Zinc, as known as non-magnetic element, has been doped into nickel ferrite under thin film form to modify its structural and magnetic properties. Laser ablated Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (0.0≤x≤0.5) thin films grown on R-cut Al{sub 2}O{sub 3} (0001) substrates using pulsed laser deposition (PLD) technique are single phase with (l l l) orientation, and they are strongly room temperature ferromagnetic. Compared to other Ni–Zn ferrite thin films we observed the enhancement in coercivity H{sub c}. Higher H{sub c} thin films can be used as potential candidates for modern miniaturization of electronic devices. - Highlights: • Laser ablated ferrite thin films. • Enhanced structural and magnetic properties of Ni–Zn ferrite thin films. • Ni–Zn Ferrite films are strongly room temperature ferromagnetic. • Higher coercivity in fabricated films.

  16. Influence of the shape and surface oxidation in the magnetization reversal of thin iron nanowires grown by focused electron beam induced deposition

    Directory of Open Access Journals (Sweden)

    Luis A. Rodríguez

    2015-06-01

    Full Text Available Iron nanostructures grown by focused electron beam induced deposition (FEBID are promising for applications in magnetic sensing, storage and logic. Such applications require a precise design and determination of the coercive field (HC, which depends on the shape of the nanostructure. In the present work, we have used the Fe2(CO9 precursor to grow iron nanowires by FEBID in the thickness range from 10 to 45 nm and width range from 50 to 500 nm. These nanowires exhibit an Fe content between 80 and 85%, thus giving a high ferromagnetic signal. Magneto-optical Kerr characterization indicates that HC decreases for increasing thickness and width, providing a route to control the magnetization reversal field through the modification of the nanowire dimensions. Transmission electron microscopy experiments indicate that these wires have a bell-type shape with a surface oxide layer of about 5 nm. Such features are decisive in the actual value of HC as micromagnetic simulations demonstrate. These results will help to make appropriate designs of magnetic nanowires grown by FEBID.

  17. Magnetic anisotropy and magnetization reversal of ultrathin iron films with in-plane magnetization on Si(111) substrates

    Institute of Scientific and Technical Information of China (English)

    Liu Hao-Liang; He Wei; Du Hai-Feng; Fang Ya-Peng; Wu Qiong; Zhang Xiang-Qun; Yang Hai-Tao; Cheng Zhao-Hua

    2012-01-01

    The magnetic anisotropy and magnetization reversal of single crystal Fe films with thickness of 45 monolayer (ML) grown on Si(111) have been investigated by ferromagnetic resonance (FMR) and vibrating sample magnetometer (VSM).Owing to the significant modification of the energy surface in remanent state by slight misorientation from (111) plane and a uniaxial magnetic anisotropy,the azimuthal angular dependence of in-plane resonance field shows a six-fold symmetry with a weak uniaxial contribution,while the remanence of hysteresis loops displays a two-fold one.The competition between the first and second magnctocrystalline anisotropies may result in the switching of in-plane easy axis of the system.Combining the FMR and VSM measurements,the magnetization reversal mechanism has also been determined.

  18. Accounting for crustal magnetization in models of the core magnetic field

    Science.gov (United States)

    Jackson, Andrew

    1990-01-01

    The problem of determining the magnetic field originating in the earth's core in the presence of remanent and induced magnetization is considered. The effect of remanent magnetization in the crust on satellite measurements of the core magnetic field is investigated. The crust as a zero-mean stationary Gaussian random process is modelled using an idea proposed by Parker (1988). It is shown that the matrix of second-order statistics is proportional to the Gram matrix, which depends only on the inner-products of the appropriate Green's functions, and that at a typical satellite altitude of 400 km the data are correlated out to an angular separation of approximately 15 deg. Accurate and efficient means of calculating the matrix elements are given. It is shown that the variance of measurements of the radial component of a magnetic field due to the crust is expected to be approximately twice that in horizontal components.

  19. Absence of morphotropic phase boundary effects in BiFeO3-PbTiO3 thin films grown via a chemical multilayer deposition method

    Science.gov (United States)

    Gupta, Shashaank; Bhattacharjee, Shuvrajyoti; Pandey, Dhananjai; Bansal, Vipul; Bhargava, Suresh K.; Peng, Ju Lin; Garg, Ashish

    2011-07-01

    We report an unusual behavior observed in (BiFeO3)1- x -(PbTiO3) x (BF- xPT) thin films prepared using a multilayer chemical solution deposition method. Films of different compositions were grown by depositing several bilayers of BF and PT precursors of varying BF and PT layer thicknesses followed by heat treatment in air. X-ray diffraction showed that samples of all compositions show mixing of two compounds resulting in a single-phase mixture, also confirmed by transmission electron microscopy. In contrast to bulk compositions, samples show a monoclinic (MA-type) structure suggesting disappearance of the morphotropic phase boundary (MPB) at x=0.30 as observed in the bulk. This is accompanied by the lack of any enhancement of the remanent polarization at the MPB, as shown by the ferroelectric measurements. Magnetic measurements showed an increase in the magnetization of the samples with increasing BF content. Significant magnetization in the samples indicates melting of spin spirals in the BF- xPT films, arising from a random distribution of iron atoms. Absence of Fe2+ ions was corroborated by X-ray photoelectron spectroscopy measurements. The results illustrate that thin film processing methodology significantly changes the structural evolution, in contrast to predictions from the equilibrium phase diagram, besides modifying the functional characteristics of the BP- xPT system dramatically.

  20. Enhancement of magnetic domain topologies in Co/Pt thin films by fine tuning the magnetic field path throughout the hysteresis loop

    Energy Technology Data Exchange (ETDEWEB)

    Westover, Andrew S. [Physics Department, Brigham Young University, Provo, UT 84602 (United States); Chesnel, Karine, E-mail: kchesnel@byu.edu [Physics Department, Brigham Young University, Provo, UT 84602 (United States); Hatch, Kelsey; Salter, Philip [Physics Department, Brigham Young University, Provo, UT 84602 (United States); Hellwig, Olav [HGST a Western Digital Company, San Jose, CA 95135 (United States)

    2016-02-01

    We have studied the influence of magnetic history on the topology of perpendicular magnetic domains in a thin ferromagnetic film made of [Co(8 Å)/Pt(7 Å)]{sub 50} multilayers. More specifically, we have followed the morphological changes in the domain pattern when applying a magnetic field perpendicular to the layer, throughout minor and major magnetization loops, and in the resulting remanent state. We carried out this study by using MFM microscopy with an in-situ magnetic field. We find that the morphology of the magnetic domain pattern is greatly influenced by the magnetic history of the material and that some features, such as the degree of bubbliness (i.e., the extent of bubble domain formation) and density of isolated domains can be enhanced by fine tuning the magnetic field path within the major hysteresis loop towards different remanent states. In particular, we see how hysteresis is correlated to irreversible changes in the domain morphology. More interestingly, we find that the magnetic domain morphology at remanence can be changed from an interconnected labyrinthine stripe state to a state of many separated bubble domains by fine tuning the magnitude of the field previously applied to the material. These results agree well with other findings, such as the magnetic reversal behavior and magnetic memory effects in Co/Pt multilayers, and provide opportunities for potential technological applications. - Highlights: • Morphology of magnetic domains in Co/Pt thin films changes with magnetic history. • Domain morphology evolves from a maze to a bubble pattern when field approaches H{sub p}. • Domain morphology at remanence depends on magnitude H{sub m} of previously applied field. • A topological maze-to-bubble phase transition occurs at remanence when H{sub m} is near H{sup ⁎}. • Density of oppositely aligned domains peaks up when H{sub m} is near H{sup ⁎}.

  1. Analysis of magnetic anomalies in relation to Placer deposits and basement configuration off Mirya bay, Central West coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.

    amplitude long wavelength anomalies (250-350 nT, 240-420 m) extending 3 km west of a line joining Mirya head with the Bhagavati Port and (2) low amplitude short wavelength anomalies (100-120 nT, 200-300 m) located to the east in Mirya Bay. Magnetic modelling...

  2. Electronic and magnetic properties of H-terminated graphene nanoribbons deposited on the topological insulator Sb2Te3

    Science.gov (United States)

    Zhang, Wei; Hajiheidari, Farideh; Li, Yan; Mazzarello, Riccardo

    2016-07-01

    Magnetism in zigzag graphene nanoribbons (GNRs) has received enormous attention recently, due to the one-dimensional nature of this phenomenon, as well as its potential applications in the field of spintronics. In this work, we present a density functional theory (DFT) investigation of H-passivated GNRs on the (111) surface of the topological insulator Sb2Te3. We show that the chemical interaction between the GNR and the substrate is weak. As a result, the GNR-surface distance is large, of the order of 3.4 Angstrom, doping effects are almost negligible, and the mean-field magnetic properties of the GNR are preserved. Nevertheless, the presence of the substrate affects significantly the magnitude of the exchange coupling constants between the edges. Although our DFT calculations do not properly describe quantum fluctuations that destabilize the edge magnetism in free-standing GNRs, they provide important information about the stabilizing mechanisms which originate from the substrate-induced spin orbit coupling and the decoherence effects due to the surface states of Sb2Te3. We argue that, owing to these mechanisms, Sb2Te3 may be a suitable substrate to investigate experimentally the transition from “quantum” to “classical” magnetism in GNRs.

  3. Tunable magnetic nanowires for biomedical and harsh environment applications

    KAUST Repository

    Ivanov, Yurii P.

    2016-04-13

    We have synthesized nanowires with an iron core and an iron oxide (magnetite) shell by a facile low-cost fabrication process. The magnetic properties of the nanowires can be tuned by changing shell thicknesses to yield remarkable new properties and multi-functionality. A multi-domain state at remanence can be obtained, which is an attractive feature for biomedical applications, where a low remanence is desirable. The nanowires can also be encoded with different remanence values. Notably, the oxidation process of single-crystal iron nanowires halts at a shell thickness of 10 nm. The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations. This property renders these core-shell nanowires attractive materials for application to harsh environments. A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires.

  4. Effect of HD Process on Microstructure and Hard Magnetic Properties of NdFeAlB Magnet

    Institute of Scientific and Technical Information of China (English)

    姜忠良; 陈秀云; 陈晓东; 石大立; 杨昌平; 朱静

    2002-01-01

    The effect of Hydrogen Decrepitation (HD) process on the magnetic properties and microstructure of sintered NdFeAlB magnet (HD magnet) was investigated. The results show that the coercivity of HD magnet is higher than that of traditional ball milling (BM) magnet, while the remanence and the maximum energy product of HD magnet are lower. Microstructure analysis shows that some fine un-sintered powders are distributed at the grain boundaries of HD magnet. X-ray diffraction (XRD) analysis reveals that the degree of easy axis alignment of HD magnet is lower. Some ideas to improve the current HD process were proposed.

  5. Magnetic Nanocapsules

    Institute of Scientific and Technical Information of China (English)

    Zhidong ZHANG

    2007-01-01

    A brief review on recent advances in the area of the magnetic nanocapsules is given. The most applicable nanoencapsulation procedures are introduced, which include: (1) physical techniques such as arc-discharge,evaporating, etc.; (2) chemical techniques such as chemical vapor deposition, solid-state reactions, etc. The structure and magnetic properties of various nanocapsules with different core/shell structures are studied in details, for possibly applications in magnetic recording, magnetic refrigerator, magnetic fluids, superconductors and medicine.

  6. Correcting and coating thin walled X-ray Optics via a combination of controlled film deposition and magnetic smart materials

    Science.gov (United States)

    Ulmer, Melville

    The project goal is to demonstrate that thin walled (price. Since the desired surface area for the next generation X-ray telescope is >10x that of Chandra, the >10x requirement is then for >200 m^2 of surface area with a surface finish of better than 0.5 nm. Therefore, replication of some sort is called for. Because no replication technology has been shown to achieve ≤1" angular resolution, post fabrication figure corrections are likely going to be necessary. Some have proposed to do this in orbit and others prelaunch including us. Our prelaunch approach is to apply in-plane stresses to the thin walled mirror shells via a magnetic field. The field will be held in by some magnetically hard material such as NiCo. By use of a so called magnetic smart material (MSM) such as Terfenol-D, we already shown that strong enough stresses can be generated. Preliminary work has also shown that the magnetic field can be held in well enough to apply the figure correcting stresses pre-launch. What we call "set-it and forget-it." However, what is unique about our approach is that at the cost of complexity and some areal coverage, our concept will also accommodate in-orbit adjustments. Furthermore, to the best of our knowledge ours is one of two known stress modification processes that are bi-axial. Our plan is first to validate set-it and forget-it first on cantilevers and then to expand this to working on 5 cm x 5 cm pieces. We will work both with NiCo and glass or Si coated with Terfenol-D. Except for the NiCo, substrates we will also coat the samples with NiCo in order to have a film that will hold in the magnetic field. As part of the coating process, we will control the stress of the film by varying the voltage bias while coating. The bias stress control can be used to apply films with minimal stress such as Terfenol-D and X-ray reflecting coatings such as Ir. Ir is a highly desirable coating for soft X-ray astronomy mirrors that can have significant built in stress unless

  7. The Role of Magnetic Vortex Formation in Chains of Spherical FeNi Nanoparticles: A Micromagnetics Study

    DEFF Research Database (Denmark)

    Barpandal, Prabeer; Scheinfein, Michael R.; Kasama, Takeshi

    2009-01-01

    Magnetic remanent states and magnetization reversal mechanisms in linear chains of three closely-spaced Fe1-xNix nanoparticles are studied using micromagnetic simulations, for particle sizes of between 10 and 150 nm. The role of the formation and switching of magnetic vortices in the particles...

  8. Magnetic susceptibility and its relationship with paleoenvironments, diagenesis and remagnetization: examples from the Devonian carbonates of Belgium

    NARCIS (Netherlands)

    Da Silva, A.-C.; Dekkers, M.J.; Mabille, C.; Boulvain, F.

    2012-01-01

    To better understand the origin of the initial magnetic susceptibility (χin) signal in carbonate sequences, a rock magnetic investigation that includes analysis of acquisition curves of the isothermal remanent magnetization (IRM) and hysteresis parameters, was undertaken on Devonian carbonates from

  9. Magnetic iron-nickel sulphides in the Pliocene and Pleistocene marine marls from the Vrica section (Calabria, Italy)

    NARCIS (Netherlands)

    Velzen, A.J. van; Dekkers, M.J.; Zijderveld, J.D.A.

    1993-01-01

    The rock magnetic properties of the late Pliocene and early Pleistocene open-marine marls from the Vrica section in Calabria (Italy) point to magnetic sulphide as the main magnetic mineral and remanence carrier. The maximum blocking temperatures, however, are between 340 and 360°C, which is too high

  10. Interpretation of low-temperature data part 4: The low-temperature magnetic transition of monoclinic pyrrhotite

    NARCIS (Netherlands)

    Rochette, P.; Fillion, G.; Dekkers, M.J.

    2011-01-01

    Use of low temperature (LT) magnetic transitions to identify magnetic minerals that carry a remanence – either natural or laboratory-induced – at room temperature, is a classic tool in rock magnetism (e.g. Nagata et al., 1964; Kosterov, 2007). This particularly applies to magnetite (Verwey transitio

  11. Experiments, modeling and simulation of the magnetic behavior of inhomogeneously coated nickel/aluminum hybrid foams

    Energy Technology Data Exchange (ETDEWEB)

    Jung, A., E-mail: anne.jung@mx.uni-saarland.de [Universität des Saarlandes, Institute of Applied Mechanics, Campus A4 2, 66123 Saarbrücken (Germany); Klis, D., E-mail: d.klis@lte.uni-saarland.de [Universität des Saarlandes, Laboratory for Electromagnetic Theory, Campus C6 3, 66123 Saarbrücken (Germany); Goldschmidt, F., E-mail: f.goldschmidt@mx.uni-saarland.de [Universität des Saarlandes, Institute of Applied Mechanics, Campus A4 2, 66123 Saarbrücken (Germany)

    2015-03-15

    Open-cell metal foams are used as lightweight construction elements, energy absorbers or as support for catalytic coatings. Coating of open-cell metal foams is not only used for catalytic applications, but it leads also to tremendous increase in stiffness and energy absorption capacity. A non-line of sight coating technique for complex 3D structures is electrodeposition. Unfortunately, due to the 3D porosity and the related problems in mass transport limitation during the deposition, it is not possible to produce homogeneously coated foams. In the present contribution, we present a semi-non-destructive technique applicable to determine the coating thickness distribution of magnetic coatings by measuring the remanent magnetic field of coated foams. In order to have a closer look at the mass transport mechanism, a numerical model was developed to predict the field scans for different coating thickness distributions in the foams. For long deposition times the deposition reaches a steady state whereas a Helmholtz equation is sufficient to predict the coating thickness distribution. The applied current density could be identified as the main influencing parameter. Based on the developed model, it is possible to improve the electrodeposition process and hence the homogeneity in the coating thickness of coated metal foams. This leads to enhanced mechanical properties of the hybrid foams and contributes to better and resource-efficient energy absorbers and lightweight materials. - Highlights: • Production of hybrid foams by electrodeposition of nickel on open-cell metal foams. • Magnetic field scans for visualization of spatial coating thickness distribution. • Modeling of magnetic fields of inhomogeneously coated hybrid foams. • Investigation of mass transport limitation during coating by a Helmholtz equation. • Increasing coating homogeneity by use of low current densities and deposition rates.

  12. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  13. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  14. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  15. Magnetism of nakhlites and chassignites

    Science.gov (United States)

    Cisowski, S. M.

    1985-01-01

    Hysteresis measurements on three shergottite and two nakhlite meteorites indicate single domain grain size behavior for the highly shocked Shergotty, Zagami, and EETA 79001 meteorites, with more multidomain-like behavior for the unshocked Nakhla and Governador Valadares meteorites. High viscosity and initial susceptibility for Antarctic shergottite ALHA 7705 indicate the presence of superparamagnetic grains in this specimen. Thermomagnetic analysis indicate Shergotty and Zagami as the least initially oxidized, while EETA 79001 appears to be the most oxidized. Cooling of the meteorite samples from high temperature in air results in a substantial increase in magnetization due to the production of magnetite through oxidation exsolution of titanomagnetite. However, vacuum heating substantially suppresses this process, and in the case of EETA 79001 and Nakhla, results in a rehomogenization of the titanomagnetite grains. Remanence measurements on several subsamples of Shergotty and Zagami meteorites reveal a large variation in intensity that does not seem related to the abundance of remanence carriers. The other meteorites carry only weak remanence, suggesting weak magnetizing fields as the source of their magnetic signal. The meteorites' weak field environment is consistent with Martian or asteroidal body origin but inconsistent with terrestrial origin.

  16. Electric field control of magnetic anisotropy in a Co/Pt bilayer deposited on a high-κ SrTiO3

    Science.gov (United States)

    Nakazawa, S.; Obinata, A.; Chiba, D.; Ueno, K.

    2017-02-01

    The perpendicular magnetic anisotropy (PMA) of a Co (0.5 nm)/Pt (2.4 nm) bilayer film was electrostatically tuned using a high-κ dielectric, SrTiO3, with a back-gating configuration. The Co film was directly deposited onto a SrTiO3 (001) substrate and capped by a Pt layer. The coercivity was enhanced (reduced) by applying a positive (negative) gate bias. The efficiency of the PMA energy modulation by the electric field was determined to be 1300-23 100 fJ/V m, which is 1-3 orders of magnitude higher than the efficiencies obtained in previous studies. The superior efficiency of this system is most likely attributable to the large dielectric constant of the SrTiO3 gate insulator and could be evidence that the PMA energy modulation is induced by charge accumulation.

  17. A solid-state nuclear magnetic resonance study of post-plasma reactions in organosilicone microwave plasma-enhanced chemical vapor deposition (PECVD) coatings.

    Science.gov (United States)

    Hall, Colin J; Ponnusamy, Thirunavukkarasu; Murphy, Peter J; Lindberg, Mats; Antzutkin, Oleg N; Griesser, Hans J

    2014-06-11

    Plasma-polymerized organosilicone coatings can be used to impart abrasion resistance and barrier properties to plastic substrates such as polycarbonate. Coating rates suitable for industrial-scale deposition, up to 100 nm/s, can be achieved through the use of microwave plasma-enhanced chemical vapor deposition (PECVD), with optimal process vapors such as tetramethyldisiloxane (TMDSO) and oxygen. However, it has been found that under certain deposition conditions, such coatings are subject to post-plasma changes; crazing or cracking can occur anytime from days to months after deposition. To understand the cause of the crazing and its dependence on processing plasma parameters, the effects of post-plasma reactions on the chemical bonding structure of coatings deposited with varying TMDSO-to-O2 ratios was studied with (29)Si and (13)C solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) using both single-pulse and cross-polarization techniques. The coatings showed complex chemical compositions significantly altered from the parent monomer. (29)Si MAS NMR spectra revealed four main groups of resonance lines, which correspond to four siloxane moieties (i.e., mono (M), di (D), tri (T), and quaternary (Q)) and how they are bound to oxygen. Quantitative measurements showed that the ratio of TMDSO to oxygen could shift the chemical structure of the coating from 39% to 55% in Q-type bonds and from 28% to 16% for D-type bonds. Post-plasma reactions were found to produce changes in relative intensities of (29)Si resonance lines. The NMR data were complemented by Fourier transform infrared (FTIR) spectroscopy. Together, these techniques have shown that the bonding environment of Si is drastically altered by varying the TMDSO-to-O2 ratio during PECVD, and that post-plasma reactions increase the cross-link density of the silicon-oxygen network. It appears that Si-H and Si-OH chemical groups are the most susceptible to post-plasma reactions. Coatings produced at a

  18. Nanocrystalline magnetic materials obtained by flash annealing

    Directory of Open Access Journals (Sweden)

    R.K. Murakami

    1999-04-01

    Full Text Available The aim of the present work was to produce enhanced-remanence nanocrystalline magnetic material by crystallizing amorphous or partially amorphous Pr4.5Fe77B18.5 alloys by the flash annealing process, also known as the dc-Joule heating process, and to determine the optimal conditions for obtaining good magnetic coupling between the magnetic phases present in this material. Ribbons of Pr4.5Fe77B18.5 were produced by melt spinning and then annealed for 10-30 s at temperatures 500 - 640 °C by passing current through the sample to develop the enhanced-remanence nanocrystalline magnetic material. These materials were studied by X-ray diffraction, differential thermal analysis and magnetic measurements. Coercivity increases of up to 15% were systematically observed in relation to furnace-annealed material. Two different samples were carefully examined: (i a sample annealed at 600 °C which showed the highest coercive field Hc and remanence ratio Mr/Ms and (ii a sample annealed at 520 °C which showed phase separation in the second quadrant demagnetization curve. Our results are in agreement with other studies which show that flash annealing improves the magnetic properties of some amorphous ferromagnetic ribbons.

  19. Contribution of Anisotropy of Magnetic Susceptibility (AMS) to reconstruct flooding characteristics of a 4220 BP tsunami from a thick unconsolidated structureless deposit (Banda Aceh, Sumatra)

    Science.gov (United States)

    Wassmer, Patrick; Gomez, Christopher; Iskandasyah, T. Yan W. M.; Lavigne, Franck; Sartohadi, Junun

    2015-07-01

    One of the main concerns of deciphering tsunami sedimentary records along seashore is to link the emplaced layers with marine high energy events. Based on a combination of morphologic features, sedimentary figures, grain size characteristics, fossils content, microfossils assemblages, geochemical elements, heavy minerals presence; it is, in principle, possible to relate the sedimentary record to a tsunami event. However, experience shows that sometimes, in reason of a lack of any visible sedimentary features, it is hard to decide between a storm and a tsunami origin. To solve this issue, the authors have used the Anisotropy of Magnetic Susceptibility (AMS) to evidence the sediment fabric. The validity of the method for reconstructing flow direction has been proved when applied on sediments in the aftermath of a tsunami event, for which the behaviour was well documented (2004 IOT). We present herein an application of this method for a 56 cm thick paleo-deposit dated 4220 BP laying under the soil covered by the 2004 IOT, SE of Banda Aceh, North Sumatra. We analysed this homogenous deposit, lacking of any visible structure, using methods of classic sedimentology to confirm the occurrence of a high energy event. We then applied AMS technique that allowed the reconstruction of flow characteristics during sediment emplacement. We show that all the sequence was emplaced by uprush phases and that the local topography played a role on the re-orientation of a part of the uprush flow, creating strong reverse current. This particular behaviour was reported by eyewitnesses during the 2004 IOT event.

  20. Saw-toothed pattern of sedimentary paleointensity records explained by cumulative viscous remanence

    NARCIS (Netherlands)

    Kok, Yvo S.; Tauxe, Lisa

    2001-01-01

    The relative paleointensity of the earth's magnetic field from ODP Site 851 has been characterized by progressive decay w x towards polarity reversals, followed by sharp recovery of pre-reversal values 1 . We resampled the Gilbert-Gaub reversal boundary of this deep-sea core, and show that during de

  1. Magnet properties of Mn{sub 70}Ga{sub 30} prepared by cold rolling and magnetic field annealing

    Energy Technology Data Exchange (ETDEWEB)

    Ener, Semih, E-mail: ener@fm.tu-darmstadt.de [Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Skokov, Konstantin P. [Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Karpenkov, Dmitriy Yu. [Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Faculty of Physics, Tver State University, 170100 Tver (Russian Federation); Immanuel Kant Baltic Federal University, 236041 Kaliningrad (Russian Federation); Kuz' min, Michael D. [Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Gutfleisch, Oliver [Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Fraunhofer IWKS, Project Group for Material Cycles and Resource Strategy, 63457 Hanau (Germany)

    2015-05-15

    The remanence and coercivity of arc melted Mn{sub 70}Ga{sub 30} can be substantially improved by cold rolling. For best performance the rolled material should be annealed at T=730 K in the presence of a magnetic field of 1 T. The so-obtained magnet has a remanence of 0.239 T and a coercivity of 1.24 T at room temperature. The underlying reason for the high coercivity and remanence is the increase of the content of a metastable ferrimagnetic D0{sub 22} phase at the expense of the normally stable anti-ferromagnetic D0{sub 19}. Magnetic field significantly increases the nucleation rate of the ferromagnetic D0{sub 22} phase that leads to grain size refinement and as a consequence of improving remanence and coercive field. - Highlights: • Alternative synthesis method for D0{sub 22} phase formation in Mn–Ga is developed. • Effect of cold rolling and annealing on magnetic properties of Mn{sub 70}Ga{sub 30} is examined. • Small magnetic fields are sufficient to accelerate nucleation of the D0{sub 22} phase.

  2. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...

  3. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...

  4. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  5. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...

  6. Tests for orbital influences on the geomagnetic field, and Quarternary magnetic records from North Atlantic and Arctic deep-sea sediments

    Science.gov (United States)

    Xuan, Chuang

    paleomagnetic data and facilitates the calculation of paleomagnetic directions and RPI proxies. This new software incorporates new methods of analysis, particularly in the generation of RPI proxies. U-channel NRM measurements at Integrated Ocean Drilling Program (IODP) Site U1304 yield continuous high resolution paleomagnetic records for the last ˜1.5 Ma. Sediments from IODP Site U1304 clearly recorded the Brunhes/Matuyama boundary, the Jaramillo subchron, and the Cobb Mountain subchron, as well as the Kamikatsura excursion and the Gardar excursion. Age model for the site is established by correlating IODP Site U1304 RPI record to the PISO-1500 RPI stack using automated dynamic programming method with limited number of tie points. No significant orbital periods were detected in RPI record from the site. Various evidences indicate that the episodic deposits of laminated diatom ooze throughout the IODP Site U1304 sediments, appear to dilute the magnetic concentrations of the sediments with elevated sedimentation rates, but do not debilitate the reliability of the acquired paleomagnetic direction and intensity data. Rock magnetic experiments carried out under various temperature ranges, along with scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS) observations as well as X-ray diffraction (XRD) analyses, on bulk Arctic deep-sea sediments and magnetic extracts from seven cores collected by the Healy-Oden Trans-Arctic Expedition 2005 (HOTRAX05), indicate that (titano)magnetite and titanomaghemite are the magnetic remanence carriers. It appears that the titanomaghemite carries a chemical remanent magnetization (CRM) that is partially self-reversed relative to the detrital remanent magnetization (DRM) carried by the host titanomagnetite, causing the apparent magnetic 'excursions' in the Arctic deep-sea sediment records. The partial self-reversal could have been accomplished by ionic ordering during oxidation, thereby changing the balance of the magnetic

  7. Paleomagnetism of the Mississippi Valley-type Zn-Pb deposits of the Silesian-Cracow area, Poland

    Science.gov (United States)

    Symons, David T. A.; Sangster, D.F.; Leach, D.L.

    1996-01-01

    Paleomagnetic analysis of zinc-lead ore and host rocks from 35 sites in three mines and several quarries was completed using alternating field and thermal step demagnetization and saturation isothermal remanent magnetization methods. Paleomagnetic conglomerate, breccia and fold tests were used to test for remanence stability. Most limestone and dolostone sites of the Middle Triassic Muschelkalk Formation carry a dual-polarity primary or diagenetic Middle to Upper Triassic remanence. Late dolomite and Mississippi Valley-type (MVT) mineralization from 14 sites carry a dual-polarity Tertiary magnetization that is shown to be post-brecciation and syndeformational by the paleomagnetic tests. This age supports gravity-driven fluid flow models for ore genesis that are associated with the Alpine orogeny.

  8. Self-induced steady-state magnetic field in the negative ion sources with localized rf power deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shivarova, A.; Todorov, D., E-mail: dimitar-tdrv@phys.uni-sofia-bg; Lishev, St. [Faculty of Physics, Sofia University, BG-1164 Sofia (Bulgaria)

    2016-02-15

    The study is in the scope of a recent activity on modeling of SPIDER (Source for Production of Ions of Deuterium Extracted from RF plasma) which is under development regarding the neutral beam injection heating system of ITER. The regime of non-ambipolarity in the source, established before, is completed here by introducing in the model the steady state magnetic field, self-induced in the discharge due to the dc current flowing in it. Strong changes in the discharge structure are reported.

  9. MAGNETS

    Science.gov (United States)

    Hofacker, H.B.

    1958-09-23

    This patent relates to nmgnets used in a calutron and more particularly to means fur clamping an assembly of magnet coils and coil spacers into tightly assembled relation in a fluid-tight vessel. The magnet comprises windings made up of an assembly of alternate pan-cake type coils and spacers disposed in a fluid-tight vessel. At one end of the tank a plurality of clamping strips are held firmly against the assembly by adjustable bolts extending through the adjacent wall. The foregoing arrangement permits taking up any looseness which may develop in the assembly of coils and spacers.

  10. Photocatalytic and magnetic behaviors of BiFeO{sub 3} thin films deposited on different substrates

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hao-Min; Wang, Huan-Chun; Shen, Yang; Lin, Yuan-Hua, E-mail: linyh@tsinghua.edu.cn; Nan, Ce-Wen [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2014-11-07

    Single phase polycrystalline BiFeO{sub 3} thin films were grown on three different substrates via chemical solution deposition. Our results indicate that the band gap of as-prepared BiFeO{sub 3} films can be tuned (2.02–2.67 eV) by the grain size effects caused by the substrates. These BiFeO{sub 3} films show good photocatalytic properties by the degradation of Congo red solution under visible-light irradiation (λ{sub  }> 400 nm). Additionally, weak ferromagnetic behaviors can be observed at room temperature in all the films, which should be correlated to the destruction of the incommensurate cycloid spin structure of BiFeO{sub 3} phase and the coexistence of Fe{sup 3+} and Fe{sup 2+} as confirmed by X-ray photoelectron spectroscopy.

  11. Magnetic Properties of fe Deposited on W(110) Surface: Effects of O Contamination and O2 Adsorption

    Science.gov (United States)

    Malonda-Boungou, B. R.; Okana-Lomanga, A. L.; Moussounda, P. S.; M'Passi-Mabiala, B.; Demangeat, C.

    2017-06-01

    We have investigated the adsorption sites and the electronic structure correlated with the magnetic properties of ultrathin Fe films on W(110) system using spin-polarized calculations within the density-functional approach with generalized gradient approximation by the pseudopotential plane-wave code. For one Fe monolayer (ML) on W(110) system the Fe atoms prefer to bind on the bridge adsorption sites of the W(110) surface, with an inward relaxation of -12.68%. The top and diagonal bridge sites investigated are energetically less favorable. We have shown that intermixing between Fe and W is unlikely: the surface ordered Fe-W alloy is unstable against the 1-ML Fe on W(110). While the control of oxygen element is known to be an important key to a perfect growth of Fe on W(110), its possible contamination is checked. Performing spin polarized calculations with the optimized geometry, the induced magnetic moments on W subsurface are obtained: the W atoms are always antiferromagnetically coupled to the Fe atoms, one exception being the case of the antiferromagnetic Fe surface where, due to frustration, the induced polarization on the W atoms is zero. The bridge site is the lower adsorption energy one for O2 molecular bonding perpendicular to the surface. In the case of O2 bonding parallel and oblique to the surface, it is always dissociated into two O atoms on Fe/W(110) surface through geometry optimization, for all considered sites.

  12. Assemblies of magnetite nanoparticles extracted from magnetotactic bacteria: A magnetic study

    Science.gov (United States)

    Huízar-Félix, A. M.; Muñoz, D.; Orue, I.; Magén, C.; Ibarra, A.; Barandiarán, J. M.; Muela, A.; Fdez-Gubieda, M. L.

    2016-02-01

    Self-assembly has emerged as a suitable technique for tuning the properties of nanoparticles. In this work, we report the self-assembly of magnetosomes assisted by an external magnetic field. The magnetosomes are magnetite nanoparticles biomineralized by magnetotactic bacteria Magnetospirillum gryphiswaldense. These nanoparticles present truncated cubo-octahedral morphology with a mean diameter of ≈36 nm and are surrounded by a lipid bilayer membrane with a thickness ≈2-4 nm. The use of the appropriate preparation conditions, such as initial colloidal concentration and magnetic fields applied during deposition allowed us to obtain very reproducible self-assembled 2D patterns. Homogeneous ensembles of magnetosomes onto silicon and carbon surfaces are composed of elongated structures in the form of wide chains that cover a large area of the substrates. Transmission electron microscopy image and off-axis electron holography showed the map of the stray magnetic fields produced by these assemblies. The induced magnetic anisotropy was analyzed by measuring the hysteresis loops of the assemblies at different angles in a magneto-optical Kerr effect magnetometer. The evolution of the coercive field and remanence verified the presence of well-defined patterns. The experimental results were analyzed on the based of a biaxial model.

  13. Geochemical normalization of magnetic susceptibility - a simple tool for distinction the sediment provenance and post-depositional processes in floodplain sediments

    Science.gov (United States)

    Famera, Martin; Matys Grygar, Tomas; Elznicova, Jitka

    2017-04-01

    Magnetic susceptibility is highly appreciated in sedimentary and environmental geology. It may also reflect provenance of the sediment and post-depositional changes therein, including soil-forming processes. We studied the applicability of Fe-normalization of mass-specific magnetic susceptibility (MS) and Ti-normalization of Fe concentrations in description of fluvial sediments from five different catchments. We dealt with two catchments with some "mafic" source rocks (Fe-rich rocks) and three almost purely "felsic" catchments (source rocks with dominant quartz and feldspars). The fine-grained floodplain sediments (from clayey silts to fine sands) were obtained by drill coring and analysed for Fe and Ti concentrations using X-ray fluorescence spectroscopy (EDXRF) and MS using kappabridge. To correct MS for the sedimentological grain-size effects and possible magnetic enrichment, we used background functions constructed in the same way like for heavy metals. The representative profiles downward the floodplain sediments demonstrate the following MS stratigraphy: (1) 15-50 cm thick top stratum A, usually with MS and heavy metal enrichment, (2) underlying stratum B with stable values of MS, MS/Fe and Fe/Ti and (3) the lowermost stratum C with variable Fe concentrations and MS and high-chroma reductimorphic features due to micro-accumulations of Fe and Mn oxides in discoloured matrix, or grey colour due to permanently removed Fe(III) oxide pigment. The boundary between strata B and C can be at a depth of several decimetres to more than 1 metre depending on the thickness of floodplain fines, site-specific river incision and water table fluctuation. For the construction of MS background functions we used Fe concentrations as an independent variable (a predictor). It allows for calculation of MS of sediments as it would not be affected by post-depositional changes and pollution. Pristine MS is than predicted for any sample using formula MS_PRISTINE = const·cFe + const

  14. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....

  15. Experimental evidence for lamellar magnetism in hemo-ilmenite by polarized neutron scattering

    DEFF Research Database (Denmark)

    Brok, Erik; Sales, Morten; Lefmann, Kim

    2014-01-01

    lamellae (approximate to 3 μm m thick) of canted antiferromagnetic hematite (FeTiO3-bearing α-Fe2O3) and the mutual exsolutions of the same phases on the micron to nanometer scale. The origin of stable natural remanent magnetization (NRM) in this system has been proposed to be uncompensated magnetic...

  16. Magnetic relaxation behaviour in Pr{sub 2}NiSi{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Pakhira, Santanu, E-mail: santanupakhira20006@gmail.com; Mazumdar, Chandan; Ranganathan, R. [Condensed Matter Physics Division, Saha Institute Of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064 (India)

    2016-05-06

    Time dependent isothemal remanent magnetizatin (IRM) behaviour for polycrystalline compound Pr{sub 2}NiSi{sub 3} have been studied below its characteristic temperature. The compound undergoes slow magnetic relaxation with time. Along with competing interaction, non-magnetic atom disorder plays an important role in formation of non-equilibrium glassy like ground state for this compound.

  17. Synthesis and characterization of Fe3O4@Ag core-shell: structural, morphological, and magnetic properties

    Directory of Open Access Journals (Sweden)

    Mahdi Ghazanfari

    2014-12-01

    Full Text Available This paper is a report on the synthesis of the Fe3O4@Ag core-shell with high saturation magnetization of magnetite nanoparticles as the core, by using polyol route and silver shell by chemical reduction. X-ray diffraction (XRD and Fourier transform infrared spectroscopy analyses confirmed that the particles so produced were monophase. The magnetic properties of the product were investigated by using a vibrating sample magnetometer. Magnetic saturation of magnetite was 91 emu/g that around about bulk magnetization. This high saturation magnetization can be attributed to the thin dead layer. By using polyethylene glycol as a surfactant to separate and restrict the growth of the particles, magnetostatic interactions are in good agreement with the remanence ratio analysis. Morphology and the average size of the particles were determined with field emission scanning electron microscope (FESEM. Spherical aggregates of Fe3O4 (size around 73 nm are composed of a small primary particle size of about 16 nm. Silver deposition was done using butylamine as the reductant of AgNO3 in ethanol with different ratio. The silver layers were estimated using statistical histogram images of FESEM. Silver-coated iron oxide nanohybrids have been used in a broad range of applications, including chemical and biological sensing, due to the broad absorption in the optical region associated with localized surface plasmon resonance.

  18. Effects of thickness and annealing condition on magnetic properties and thermal stabilities of Ta/Nd/NdFeB/Nd/Ta sandwiched films

    Science.gov (United States)

    Liu, Wen-Feng; Zhang, Min-Gang; Zhang, Ke-Wei; Zhang, Hai-Jie; Xu, Xiao-Hong; Chai, Yue-Sheng

    2016-11-01

    Ta/Nd/NdFeB/Nd/Ta sandwiched films are deposited by magnetron sputtering on Si (100) substrates, and subsequently annealed in vacuum at different temperatures for different time. It is found that both the thickness of NdFeB and Nd layer and the annealing condition can affect the magnetic properties of Ta/Nd/NdFeB/Nd/Ta films. Interestingly, the thickness and annealing temperature show the relevant behaviors that can affect the magnetic properties of the film. The high coercivity of 24.1 kOe (1 Oe = 79.5775 A/m) and remanence ratio (remanent magnetization/saturation magnetization) of 0.94 can be obtained in a Ta/Nd(250 nm)/NdFeB(600 nm)/Nd(250 nm)/Ta film annealed for 3 min at 1023 K. In addition, the thermal stability of the film is also linked to the thickness of NdFeB and Nd layer and the annealing temperature as well. The excellent thermal stability can be achieved in a Ta/Nd(250 nm)/NdFeB(600 nm)/Nd(250 nm)/Ta film annealed at 1023 K. Program supported by the National Natural Science Foundation of China (Grant No. 51305290), the Higher Education Technical Innovation Project of Shanxi Province, China (Grant No. 2013133), the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals of Shanxi Province, China (Grant No. 2015003), and the Program for the Key Team of Scientific and Technological Innovation of Shanxi Province, China (Grant No. 2013131009).

  19. Effect of Ni content on the structural, morphological and magnetic properties of spray deposited Ni–Zn ferrite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kumbhar, S.S.; Mahadik, M.A.; Mohite, V.S.; Hunge, Y.M.; Rajpure, K.Y.; Bhosale, C.H., E-mail: chbhosale@gmail.com

    2015-07-15

    Graphical abstract: The Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} (where x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) thin films were prepared by spray pyrolysis technique onto the quartz substrates. The composition x = 0.4 shows the formation of the compact grain structure and highest saturation magnetization of 143 emu/cm{sup 3}. - Highlights: • Synthesis of nanocrystalline Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} thin films. • Influence of Ni substitution on physicochemical properties. • Electrical conductivity arises mainly from the grain boundary. • The highest saturation magnetization is 143 emu/cm{sup 3} for x = 0.4. - Abstract: The Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} thin films have been prepared using a simple spray pyrolysis technique. The X-ray diffraction studies reveal that, the films are polycrystalline with spinel structure. The lattice parameters vary in the range of 8.35–8.48 Å with composition (x) obeying Vegard’s rule. SEM and AFM studies show that the surface of the films exhibit a smooth, compact and a pin hole free morphology. Raman spectra indicate first order Raman active modes; A{sub 1g} (λ = 334 cm{sup −1}); E{sub g} (λ = 148 cm{sup −1}) and T{sub 2g} (λ = 699) of the Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4}. The investigation on dielectric constant, dielectric loss tangent and ac conductivity was carried out in the frequency range 20 Hz–1 MHz at room temperature. The linear nature of the AC conductivity shows small polaron type of hopping mechanism. The saturation magnetization increases up to x = 0.4 (143 emu/cm{sup 3}), which decreases for higher x.

  20. Structural and magnetic characterization of Fe{sub 0.3}Ti{sub 0.7}O{sub 2-} {sub {delta}} films obtained by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Torres, Claudia E. [Dpto. de Fisica-IFLP, Fac. C. Exactas, UNLP. C.C. 67, 1900 La Plata (Argentina)]. E-mail: torres@fisica.unlp.edu.ar; Duhalde, Stella [Depto. de Fisica, Fac. Ingenieria, UBA, Paseo Colon 850, 1063 Buenos Aires (Argentina); Fabiana Cabrera, A. [Dpto. de Fisica-IFLP, Fac. C. Exactas, UNLP. C.C. 67, 1900 La Plata (Argentina); Sanchez, Francisco H. [Dpto. de Fisica-IFLP, Fac. C. Exactas, UNLP. C.C. 67, 1900 La Plata (Argentina); Chilliote, Claudio [Fac. Ciencias Exactas y Naturales, UBA, Ciudad Universitaria, Buenos Aires (Argentina); Florencia Vignolo, M. [Depto. de Fisica, Fac. Ingenieria, UBA, Paseo Colon 850, 1063 Buenos Aires (Argentina)

    2006-10-01

    We present a study of crystalline structure, local environment around the magnetic atoms and magnetic behaviour of Fe{sub 0.3}Ti{sub 0.7}O{sub 2-} {sub {delta}} films, produced by Pulsed Laser Deposition, as a function of oxygen pressure and substrate temperature. Dark films were obtained by deposition at low O{sub 2} pressure (between 2x10{sup -3} and 10{sup -2} Pa). These films are ferromagnetic with coercivities around 0.03-0.04 T. Fe atoms are found to be predominantly metallic Fe. Transparent films were obtained when deposition was performed at high O{sub 2} pressure (between 4 and 20 Pa). Fe atoms are mainly in +3 valence state. These films have a component magnetically ordered probably corresponding to {alpha}-Fe(Ti){sub 2}O{sub 3} and a paramagnetic one attributed to Fe substituted anatase. After a thermal treatment Fe changes to +2 valence state and {alpha}-Fe(Ti){sub 2}O{sub 3} orders in the ilmenite phase increasing ten times the saturation magnetization of the magnetically ordered (hysteretic) component.

  1. 3D inversion of magnetic and electrical resistivity-induced polarization data for an epithermal Au-Ag and underlying porphyry deposit: A case study from British Columbia, Canada

    Science.gov (United States)

    Abbassi, B.; Huebert, J.; Liu, L.; Lee, B.; Cheng, L.; Richards, J. P.; Unsworth, M. J.; Oldenburg, D.

    2013-12-01

    The Newton property is an epithermal Au-Ag deposit containing precious metals in association with disseminated sulfide minerals such as pyrite. This type of deposit often shows variable geological patterns, so it is important to find fast and cost-efficient methods for their exploration. Aeromagnetic surveys and ground electrical resistivity-induced polarization methods were applied over the Newton property. From preliminary 3D inversion of ZTEM and aeromagnetic data, and joint 3D inversion of electrical resistivity-induced polarization data, we show that low-resistivity and high-chargeability regions are signatures of disseminated sulfide mineralization. Potassic alteration, characterized by hydrothermal biotite (now mostly chloritized) and magnetite is also present locally, and may be related to underlying porphyry-type mineralization. This type of alteration can be identified from its magnetic signature, but the occurrence of other magnetic formations in the deposit area made interpretations of magnetic data difficult. We show that filtering geological noises related to background magnetic anomalies is an essential step in focusing on potassic alteration zones. We used electrical resistivity and induced polarization chargeability models to remove the signals of barren magnetic zones to focus on the susceptibilities pertaining to deep potassic alterations. In order to test the credibility of these interpretations, extensive petrophysical measurements (magnetic susceptibility, electrical resistivity, and gamma ray spectra) were collected on drill-core samples. We show that potassic alteration can also be characterized accurately from high levels of potassium to thorium ratio (K/Th) in gamma ray spectrometric measurements, and that this correlation is stronger than the magnetic signal (likely because hydrothermal magnetite is variable in abundance). Therefore, we focused on magnetic susceptibility values correlated with high K/Th ratios in order to reduce the

  2. Na+ deposition in the fibrotic skin of systemic sclerosis patients detected by 23Na-magnetic resonance imaging.

    Science.gov (United States)

    Kopp, Christoph; Beyer, Christian; Linz, Peter; Dahlmann, Anke; Hammon, Matthias; Jantsch, Jonathan; Neubert, Patrick; Rosenhauer, Daniela; Müller, Dominik N; Cavallaro, Alexander; Eckardt, Kai-Uwe; Schett, Georg; Luft, Friedrich C; Uder, Michael; Distler, Jörg H W; Titze, Jens

    2017-04-01

    Skin fibrosis is the predominant feature of SSc and arises from excessive extracellular matrix deposition. Glycosaminoglycans are macromolecules of the extracellular matrix, which facilitate Na + accumulation in the skin. We used 23 Na-MRI to quantify Na + in skin. We hypothesized that skin Na + might accumulate in SSc and might be a biomarker for skin fibrosis. In this observational case-control study, skin Na + was determined by 23 Na-MRI using a Na + volume coil in 12 patients with diffuse cutaneous SSc and in 21 control subjects. We assessed skin fibrosis by the modified Rodnan skin score prior to 23 Na-MRI and on follow-up 12 months later. 23 Na-MRI demonstrated increased Na + in the fibrotic skin of SSc patients compared with skin from controls [mean ( s . d .): 27.2 (5.6) vs 21.4 (5.3) mmol/l, P skin [26.2 (4.8) vs 19.2 (3.4) mmol/l, P skin Na + amount was correlated with changes in follow-up modified Rodnan skin score (R 2 = 0.68). 23 Na-MRI detected increased Na + in the fibrotic SSc skin; high Na + content was associated with progressive skin disease. Our findings provide the first evidence that 23 Na-MRI might be a promising tool to assess skin Na + and thereby predict progression of skin fibrosis in SSc.

  3. Structure and magnetic properties of Co–CeO{sub 2} thin films deposited by PLD on Al{sub 2}O{sub 3} (0 0 0 1) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Song, Y.Q., E-mail: yuanqiangsong@gmail.com [State Key Laboratory of Electronic Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Mu, C.H.; Huo, W.R.; Liu, A.F.; Zhang, B.; Xiang, Y. [State Key Laboratory of Electronic Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2013-03-15

    Co–CeO{sub 2} films with the stoichiometry of Co{sub 0.03}Ce{sub 0.97}CeO{sub 2−δ} were deposited by pulsed laser deposition (PLD) method on Al{sub 2}O{sub 3} (0 0 0 1) substrate, the structural, magnetic, and magneto-optical properties were investigated. The films show a ceria single phase with (1 1 1) preferred orientation. Magnetic measurements confirm the ferromagnetism at room temperature, which is anisotropic with an out-of-plane magnetization easy axis. Magneto-optical measurements exhibit a giant Faraday rotation of 4800 deg/cm in the direction perpendicular to the film plane.

  4. Mineral magnetic characteristics of the late Quaternary coastal red sands of Bheemuni, East Coast (India)

    Science.gov (United States)

    Srivastava, Priyeshu; Sangode, S. J.; Parmar, Nikita; Meshram, D. C.; Jadhav, Priyanka; Singhvi, A. K.

    2016-11-01

    The voluminous red sand deposits of Bheemuni in the east coast of India provide record of coastal land-sea interaction during the late Quaternary climatic and eustatic oscillations. Limited information on the origin and depositional environments of these red sands and their chronology is available. We studied two inland to coast cross profiles from Bheemuni red sand deposits using mineral magnetism, color characteristics and Citrate-bicarbonate-dithionite (CBD) extractable pedogenic iron oxides over 23 horizons along with optically stimulated luminescence (OSL) chronology at 6 horizons. The oldest exposed bed had an optical age of 48.9 ± 1.7 ka. Differential ages between the two parallel sections (SOS = 48.9 ± 1.7 to 12.1 ± 0.3 ka and IMD = 29.3 ± 3.5 ka) suggest laterally shifting fluvial sedimentation. Both the profiles show significant amount of antiferromagnetic oxide (hematite) along with ferrimagnetic (magnetite/maghemite) mineral composition. The granulometric (/domain-) sensitive parameters (χFD, χARM, SIRM/χLF and χARM/χLF) indicate variable concentration of superparamagnetic (SP) and single domain (SD) particles between the two profiles. The higher frequency dependent and pedogenic magnetic susceptibilities (χFD and χpedo) in the younger (IMD) profile suggest enhanced pedogenesis under a warm-wet climate post 29.3 ka and also during Holocene. A combination of hard isothermal remanent magnetization (HIRM) and redness rating (RR) index indicates distinct but variable concentration of a) crystalline and b) poorly crystalline (pigmentary) hematites in both the profiles. We consider that the former (#a) is derived from hinterland red soils and possibly due to post-depositional diagenesis, and the latter (#b) precipitated from the dissolved iron under fluvial regime imparting the unique red coloration to Bheemuni sands. Partial to complete alteration of ferromagnesian minerals due to pedogenesis in hinterlands under warm-wet climate was therefore the

  5. Magnetic Dating of Ancient Residential Areas of Teotihuacan

    Science.gov (United States)

    Sanchez, F.; Rodriguez, M.; Soler-Arechalde, A. M.; Goguitchaishvili, A.; Urrutia-Fucugauchi, J.; Manzanilla, L.

    2005-05-01

    In total of 143 archeological samples were obtained from the Xalla site and 40 samples from Teopancazco, both belonging to Teotihuacan culture. Five contructive stages are recognized at Xalla. The samples consist mainly burned stuccos dated as 550 AD by C14 systematics and other unburned specimens (containing fine grained scoria) spending time interval between 100 AD and 350 AD. Vectorial composition of natural remanent magnetization were investigated using stepwise alternating field treatment. Mainly univectorial components were obtained for the majority of samples showing well clustered remanence directions. The possible dates are retrieved using a new paleosecular variation reference curve (Hueda et. Al., 2004).

  6. Developing bulk exchange spring magnets

    Energy Technology Data Exchange (ETDEWEB)

    Mccall, Scott K.; Kuntz, Joshua D.

    2017-06-27

    A method of making a bulk exchange spring magnet by providing a magnetically soft material, providing a hard magnetic material, and producing a composite of said magnetically soft material and said hard magnetic material to make the bulk exchange spring magnet. The step of producing a composite of magnetically soft material and hard magnetic material is accomplished by electrophoretic deposition of the magnetically soft material and the hard magnetic material to make the bulk exchange spring magnet.

  7. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...

  8. MAGNET

    CERN Multimedia

    B. Curé

    MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...

  9. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...

  10. MAGNET

    CERN Multimedia

    Benoit Curé.

    The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...

  11. Facile synthesis and magnetic study of Ni@polyamide 66 coaxial nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaoru, E-mail: lixiaoruqdu@126.com; Yang, Chao; Han, Ping; Zhao, Qingpei; Song, Guojun, E-mail: songguojunqdu@126.com

    2016-12-01

    Ni@polyamide 66 (PA66) core/shell coaxial double-layer nanotube arrays have been prepared in the nanopores of anodic aluminum oxide templates (AAO). The shell of PA66 nanotubes were formed first and then served as templates to deposit Ni nanotubes used as the core. The morphology, structures of the obtained arrays were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The formation of this unique coaxial nanotube structure was confirmed by SEM and TEM images and X-ray diffraction (XRD). We further explored the magnetic properties of the obtained coaxial nanotube arrays with vibrating sample magnetometer (VSM) and found that Ni@PA66 coaxial nanotubes exhibited higher remanence ratio than that of Ni nanotubes. These Ni@PA66 coaxial nanotubes are promising to be used as templates to fill in other materials. - Highlights: • Ni@PA66 coaxial nanotubes are prepared successfully with PA66 nanotubes obtained first and then Ni nanotubes were deposited in PA66 nanotubes. • The magnetic property of Ni@PA66 coaxial nanotubes is better than that of Ni nanotubes. • Ni@PA66 coaxial nanotubes can be used as templates to fill in other materials.

  12. Origin of Phosphorite Nodules of Lebedinsky Iron Deposit in Kursk Magnetic Anomaly (KMA) of the Russian Platform

    Institute of Scientific and Technical Information of China (English)

    Tourba Kamaye; Phillip Romanovitch

    2005-01-01

    Phosphorite has become increasingly important as the raw material for phosphatic fertilizer. Phosphorite nodules are widespread in the Kursk complex deposit (Russian platform). Genesis of these nodules has long been a matter of debate, and this has hampered understanding of the mechanism and controls in the formation of the nodules. In this paper, we report the petrographical, mineralogical, and geochemical data of the Lebedinsky phosphorite nodules. Petrographic study reveals complex phosphatic cement resulting in the replacement of apatite minerals around quartz grains. The main mineral composition consists of quartz, phosphate minerals (apatite, francolite mainly), feldspar, iron hydroxides and carbonate minerals. These results, when combined with available data, are used to address the origin of the phosphorite nodules. The nodules are characterized by the universal presence of biogenic and chemical signatures which is phosphorus crown around crystal grains. The structure of the nodules is massive. Their texture is depicted by basaltic cement and concretion, which consists mainly of apatite and its varieties, with general formula: Ca10 (PO4, CO3) 6(F,OH,Cl). Variation of mineralogy appears dependent on geological setting. Microscopic observations of biogenic fossils in Lebedinsky phosphorite favor a chemical and biogenic origin of phosphorites. Weathering has been suggested to be capable of liberating as much as 20 %-35 % P2O5 from sedimentary rocks. Previous investigations demonstrate that weathering of the Proterozoic substratum was the main cause in the formation of Fe, Mo, Mn,