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Sample records for high coercivity magnetic

  1. Magnetic hydrogel with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Sözeri, H., E-mail: huseyin.sozeri@tubitak.gov.tr [TUBITAK-UME, National Metrology Institute, PO Box 54, 41470 Gebze-Kocaeli (Turkey); Alveroğlu, E. [Department of Physics, Istanbul Technical University, 34469 Maslak-Istanbul (Turkey); Kurtan, U.; Şenel, M.; Baykal, A. [Department of Chemistry, Fatih University, 34500 B. Cekmece-Istanbul, (Turkey)

    2013-08-01

    Highlights: • Polyacrylamide (PAAm) hydrogels containing magnetic BaFe{sub 12}O{sub 19} nanoparticles have been prepared. • Magnetization measurements reveal that hydrogels have hard magnetic properties with high coercivity. • Magnetic nanoparticles makes the gel more homogeneous and do not diffuse out of the gel during water intake. • These gels are useful in applications as wastewater treatment once gels are magnetized before its usage. - Abstract: This study investigates the synthesis and characterization of polyacrylamide (PAAm) hydrogels containing magnetic BaFe{sub 12}O{sub 19} nanoparticles. Structural, electrical, and magnetic characterization of the gels have been performed with X-ray powder diffractometry, scanning electron microscopy, DC conductivity, magnetization and fluorescence spectroscopy techniques. The preparation and characterization of polyacrylamide (PAAm) hydrogels that contain 5 and 10 mg BaFe{sub 12}O{sub 19} (16 and 21 nm diameter) nanoparticles are described herein. It is seen from the fluorescence spectra that, nanoparticles surrounded to pyranine molecules so that some of pyranine molecules could not bound to the polymer strands. Electrical measurements show that presence of nanoparticles make the gel more homogeneous. Magnetization measurements reveal that hydrogels have hard magnetic properties with quite high coercivity of 4.2 kOe, which does not change with swelling. This feature makes these gels useful in applications as wastewater treatment if they are magnetized before use.

  2. τ-MnAl with high coercivity and saturation magnetization

    Directory of Open Access Journals (Sweden)

    J. Z. Wei

    2014-12-01

    Full Text Available In this paper, high purity τ-Mn54Al46 and Mn54−xAl46Cxalloys were successfully prepared using conventional arc-melting, melt-spinning, and heat treatment process. The magnetic and the structural properties were examined using x-ray diffraction (XRD, powder neutron diffraction and magnetic measurements. A room temperature saturation magnetization of 650.5 kAm-1, coercivity of 0.5 T, and a maximum energy product of (BHmax = 24.7 kJm-3 were achieved for the pure Mn54Al46 powders without carbon doping. The carbon substituted Mn54−xAl46Cx, however, reveals a lower Curie temperature but similar saturation magnetization as compared to the carbon-free sample. The electronic structure of MnAl shows that the Mn atom possesses a magnetic moment of 2.454 μB which results from strong hybridization between Mn-Al and Mn-Mn. We also investigated the volume and c/a ratio dependence of the magnetic moments of Mn and Al. The results indicate that an increase in the intra-atomic exchange splitting due to the cell volume expansion, leads to a large magnetic moment for the Mn atom. The Mn magnetic moment can reach a value of 2.9 μB at a volume expansion rate of ΔV/V ≈ 20%.

  3. Perspectives for high-performance permanent magnets: applications, coercivity, and new materials

    Science.gov (United States)

    Hirosawa, Satoshi; Nishino, Masamichi; Miyashita, Seiji

    2017-03-01

    High-performance permanent magnets are indispensable in the production of high-efficiency motors and generators and ultimately for sustaining the green earth. The central issue of modern permanent magnetism is to realize high coercivity near and above room temperature on marginally hard magnetic materials without relying upon the critical elements such as heavy rare earths by means of nanostructure engineering. Recent investigations based on advanced nanostructure analysis and large-scale first principles calculations have led to significant paradigm shifts in the understandings of coercivity mechanism in Nd-Fe-B permanent magnets, which includes the discovery of the ferromagnetism of the thin (2 nm) intergranular phase surrounding the Nd2Fe14B grains, the occurrence of negative (in-plane) magnetocrystalline anisotropy of Nd ions and some Fe atoms at the interface which degrades coercivity, and visualization of the stochastic behaviors of magnetization in the magnetization reversal process at high temperatures. A major change may occur also in the motor topologies, which is currently overwhelmed by the magnetic flux weakening interior permanent magnet motor type, to other types with variable flux permanent magnet type in some applications to open up a niche for new permanent magnet materials. Keynote talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8-12 November 2016, Ha Long City, Vietnam.

  4. High coercivity in rare-earth lean nanocomposite magnets by grain boundary infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Madugundo, Rajasekhar, E-mail: mraja@udel.edu [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Salazar-Jaramillo, Daniel [BCMaterials, Bizkaia Science and Technology Park, E-48160 Derio (Spain); Manuel Barandiaran, Jose [BCMaterials, Bizkaia Science and Technology Park, E-48160 Derio (Spain); Department of Electricity & Electronics, University of the Basque Country (UPV/EHU), E-48080 Bilbao (Spain); Hadjipanayis, George C., E-mail: hadji@udel.edu [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

    2016-02-15

    A significant enhancement in coercivity was achieved by grain boundary modification through low temperature infiltration of Pr{sub 75}(Cu{sub 0.25}Co{sub 0.75}){sub 25} eutectic alloy in rare-earth lean (Pr/Nd)–Fe–B/α-Fe nanocomposite magnets. The infiltration procedure was carried out on ribbons and hot-deformed magnets at 600–650 °C for different time durations. In Nd{sub 2}Fe{sub 14}B/α-Fe ribbons, the coercivity increased from 5.3 to 23.8 kOe on infiltration for 4 h. The Pr{sub 2}Fe{sub 14}B/α-Fe hot-deformed magnet shows an increase in coercivity from 5.4 to 22 kOe on infiltration for 6 h. The increase in the coercivity comes at the expense of remnant magnetization. X-ray diffraction studies confirm the presence of both the hard Nd{sub 2}Fe{sub 14}B and soft α-Fe phases. A decrease in the soft α-Fe phase content was observed after infiltration. - Highlights: • Enhancement in coercivity was achieved by grain boundary modification. • Coercivity increased from 5.3 to 23.8 kOe in Nd{sub 2}Fe{sub 14}B/α-Fe on infiltration. • Pr{sub 2}Fe{sub 14}B/α-Fe deformed magnet shows an increase in coercivity from 5.4 to 22 kOe. • The increase in the coercivity comes at the expense of remnant magnetization. • A decrease in the soft α-Fe phase content was observed after infiltration.

  5. High-coercivity magnetism in nanostructures with strong easy-plane anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, Balamurugan, E-mail: bbalasubramanian2@unl.edu, E-mail: dsellmyer@unl.edu; Manchanda, Priyanka; Skomski, Ralph; Mukherjee, Pinaki; Das, Bhaskar; Sellmyer, David J., E-mail: bbalasubramanian2@unl.edu, E-mail: dsellmyer@unl.edu [Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States); Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Valloppilly, Shah R. [Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States); Hadjipanayis, George C. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

    2016-04-11

    We report the fabrication of a rare-earth-free permanent-magnet material Co{sub 3}Si in the form of nanoparticles and investigate its magnetic properties by experiments and density-functional theory (DFT). The DFT calculations show that bulk Co{sub 3}Si has an easy-plane anisotropy with a high K{sub 1} ≈ −64 Merg/cm{sup 3} (−6.4 MJ/m{sup 3}) and magnetic polarization of 9.2 kG (0.92 T). In spite of having a negative anisotropy that generally leads to negligibly low coercivities in bulk crystals, Co{sub 3}Si nanoparticles exhibit high coercivities (17.4 kOe at 10 K and 4.3 kOe at 300 K). This result is a consequence of the unique nanostructure made possible by an effective easy-axis alignment in the cluster-deposition method and explained using micromagnetic analysis as a nanoscale phenomenon involving quantum-mechanical exchange interactions.

  6. Synthesis of high-coercivity non-stoichiometric cobalt ferrite nanocrystals: Structural and magnetic characterization

    Energy Technology Data Exchange (ETDEWEB)

    Cedeno-Mattei, Y., E-mail: yarilyn.cedeno@upr.edu [Department of Chemistry, University of Puerto Rico - Mayagueez Campus, Mayagueez, 00681 (Puerto Rico); Perales-Perez, O. [Department of Chemistry, University of Puerto Rico - Mayagueez Campus, Mayagueez, 00681 (Puerto Rico); Department of Engineering Science and Materials, University of Puerto Rico - Mayagueez Campus, Mayagueez, 00681 (Puerto Rico); Uwakweh, O.N.C. [Department of Engineering Science and Materials, University of Puerto Rico - Mayagueez Campus, Mayagueez, 00681 (Puerto Rico)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Non-stoichiometric cobalt ferrite and the composition-dependence of their magnetic properties. Black-Right-Pointing-Pointer 78% of the total Fe present in starting solutions was incorporated into the ferrite. Black-Right-Pointing-Pointer Flow-rate controlled synthesis promoted crystal growth and changes in cation distribution. Black-Right-Pointing-Pointer High coercivity was attained due to surface anisotropy, cation distribution, and crystal size. - Abstract: The magnetic properties in nanoscale ferrite materials are strongly dependent on the crystal size, morphology, and cation distribution in the lattice. The present work addressed the synthesis of Co-substituted ferrite nanocrystals were attempted at various staring Fe:Co mole ratios (3:1, 2:1, 1.7:1, and 1.4:1) and the corresponding structural and magnetic properties determined. The synthesis of the ferrite powders was carried out by the conventional and modified coprecipitation method. The later consists of contacting the metal ions solution with hydroxide ions at controlled flow-rates to promote the heterogeneous nucleation, where earlier produced ferrite nuclei will act as seeds, and hence crystal growth. The actual Fe:Co mole ratios in the as-synthesized samples were determined by energy dispersive X-ray spectroscopy (EDS). Obtained nanocrystals were also characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and Moessbauer spectroscopy techniques. Cobalt ferrite nanocrystals ranging between 11 and 19 nm exhibited coercivity values between 114 and 4412 Oe. The variation in coercivity values of cobalt ferrite nanocrystals with different compositions was mainly attributed to the remarkably enlargement of crystal size under flow-rate controlled synthesis conditions, and the particular distribution of cations between A- and B-sites in addition to surface anisotropy contribution.

  7. Mechanochemical synthesis of high coercivity Nd2(Fe,Co)14B magnetic particles.

    Science.gov (United States)

    Zhong, Y; Chaudhary, V; Tan, X; Parmar, H; Ramanujan, R V

    2017-12-07

    With increasing demand for magnets in energy conversion systems, the quest for the development and understanding of novel processing routes to produce permanent magnets has become urgent. We report a novel mechanochemical process for the synthesis of Nd 2 (Fe,Co) 14 B magnetic particles with a high coercivity of 12.4 kOe. This process involves the reduction of neodymium oxide, iron oxide, cobalt oxide and boron anhydride in the presence of a calcium reducing agent and a CaO diluent. The formation mechanism of Nd 2 (Fe,Co) 14 B changed with increasing CaO content, and the average crystal size of the Nd 2 (Fe,Co) 14 B particles also increased, resulting in an increase in the coercivity values. The reaction mechanism during milling was revealed through a study of the phase transformations as a function of milling time. It was found that unlike self-propagating reactions, this reduction reaction during milling requires continuous input of mechanical energy to reach a steady state.

  8. Thermal effect on magnetic parameters of high-coercivity cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Chagas, E. F., E-mail: efchagas@fisica.ufmt.br; Ponce, A. S.; Prado, R. J.; Silva, G. M. [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá-MT (Brazil); Bettini, J. [Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970 Campinas (Brazil); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Rua Xavier Sigaud 150 Urca. Rio de Janeiro (Brazil)

    2014-07-21

    We prepared very high-coercivity cobalt ferrite nanoparticles synthesized by a combustion method and using short-time high-energy mechanical milling to increase strain and the structural defects density. The coercivity (H{sub C}) of the milled sample reached 3.75 kOe—a value almost five times higher than that obtained for the non-milled material (0.76 kOe). To investigate the effect of the temperature on the magnetic behavior of the milled sample, we performed a thermal treatment on the milled sample at 300, 400, and 600 °C for 30 and 180 min. We analyzed the changes in the magnetic behavior of the nanoparticles due to the thermal treatment using the hysteresis curves, Williamson-Hall analysis, and transmission electron microscopy. The thermal treatment at 600 °C causes decreases in the microstructural strain and density of structural defects resulting in a significant decrease in H{sub C}. Furthermore, this thermal treatment increases the size of the nanoparticles and, as a consequence, there is a substantial increase in the saturation magnetization (M{sub S}). The H{sub C} of the samples treated at 600 °C for 30 and 180 min were 2.24 and 1.93 kOe, respectively, and the M{sub S} of these same samples increased from 57 emu/g to 66 and 70 emu/g, respectively. The H{sub C} and the M{sub S} are less affected by the thermal treatment at 300 and 400 °C.

  9. High coercivity in Fe-Nb-B-Dy bulk nanocrystalline magnets

    Energy Technology Data Exchange (ETDEWEB)

    Ziolkowski, Grzegorz; Chrobak, Artur; Klimontko, Joanna [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007, Katowice (Poland); Chrobak, Dariusz; Rak, Jan [Institute of Materials Science, University of Silesia, 75 Pulku Piechoty 1, 41-500, Chorzow (Poland); Zivotsky, Ondrej; Hendrych, Ales [Department of Physics, VSB-TU Ostrava, Ostrava (Czech Republic)

    2016-11-15

    The paper refers to structural and magnetic properties of the (Fe{sub 80}Nb{sub 6}B{sub 14}){sub 1-x}Dy{sub x} (x = 0.08, 0.10, 0.12, 0.16) bulk nanocrystalline alloys prepared by making use of the vacuum suction casting technique. The samples are in a form of rods with different diameters d = 1.5, 1, and 0.5 mm. The phase structure was investigated by XRD technique and reveals an occurrence of magnetically hard Dy{sub 2}Fe{sub 14}B as well as other relatively soft Dy-Fe, Fe-B, and Fe phases dependently on the Dy content. The alloys show hard magnetic properties with high coercive field up to 5.5 T (for x = 0.12 and d = 0.5 mm). The observed magnetic hardening effect with the increase of cooling rate (decrease of sample diameter d) can be attributed to a formation of ultra-hard magnetic objects as well as increasing role of low dimensional microstructure. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Crystallization and atomic diffusion behavior of high coercive Ta/Nd-Fe-B/Ta-based permanent magnetic thin film

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Na; Zhang, Xiao; You, Caiyin; Fu, Huarui [Xi' an University of Technology, School of Materials Science and Engineering, Xi' an (China); Shen, Qianlong [Logistics University of People' s Armed Police Force, Tianjin (China)

    2017-06-15

    A high coercivity of about 20.4 kOe was obtained through post-annealing the sputtered Ta/Nd-Fe-B/Ta-based permanent magnetic thin films. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses were performed to investigate the crystallization and atomic diffusion behaviors during post-annealing. The results show that the buffer and capping Ta layers prefered to intermix with Fe and B atoms, and Nd tends to be combined with O atoms. The preferred atomic combination caused the appearance of the soft magnetic phase of Fe-Ta-B, resulting in a kink of the second quadratic magnetic hysteresis loop. The preferred atomic diffusion and phase formation of the thin films were well explained in terms of the formation enthalpy of the various compounds. (orig.)

  11. Anisotropy and Microstructure of High Coercivity Rare Earth Iron Permanent Magnets, List of Papers Published

    Science.gov (United States)

    1989-01-01

    H. J. Duschow, D. B. do Idooli, 8. Slnuerma, IL J. Radwanski and J. J. M. Franse, J. Mooa. Moen.. Meter.. 5Z (1985) 211. 16 M. Sagawa. Y. Matsuura...Physics of Magnetic Materias, Sczyrk-Bi, Poland, 1986. 9 S. Sinnemna, R. J. Radwanski , J. J. M. Franse, D. B. De Mooiq and K. H. J. Buschow, ion and

  12. High coercivity in nanostructured Co-ferrite thin films

    Indian Academy of Sciences (India)

    ... and possesses perpendicular anisotropy. Our study has also shown that the high coercivity is related with a large residual strain, which may induce an additional magnetic anisotropy (stress anisotropy) and at the same time serve as pinning centres, which can restrict the domain wall movement and therefore, increase the ...

  13. Performance of Halbach magnet arrays with finite coercivity

    DEFF Research Database (Denmark)

    Insinga, Andrea Roberto; Bahl, C.R.H.; Bjørk, Rasmus

    2016-01-01

    of the magnetic material and the fact that the coercivity is not infinite will limit the attainable field. The presented method is able to predict when and where demagnetization will occur, and these predictions are compared with the analytical solution for the case of infinite coercivity. However, the approach...... presented here also allows quantification of the decrease in flux density and homogeneity for a partially demagnetized magnet. Moreover, the problem of how to realize a Halbach cylinder geometry using a mix of materials with different coercivities without altering the overall performance is addressed. Being...

  14. Anomalous behaviour of magnetic coercivity in graphene oxide and reduced graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Bagani, K.; Bhattacharya, A.; Kaur, J.; Rai Chowdhury, A.; Ghosh, B.; Banerjee, S., E-mail: sangam.banerjee@saha.ac.in [Saha Institute of Nuclear Physics, Surface Physics Division, 1/AF Bidhannagar, Kolkata 700064 (India); Sardar, M. [Material Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2014-01-14

    In this report, we present the temperature dependence of the magnetic coercivity of graphene oxide (GO) and reduced graphene oxide (RGO). We observe an anomalous decrease in coercivity of GO and RGO with decreasing temperature. The observation could be understood by invoking the inherent presence of wrinkles on graphene oxide due to presence of oxygen containing groups. Scanning electron microscopic image reveals high wrinkles in GO than RGO. We observe higher coercivity in RGO than in GO. At room temperature, we observe antiferromagnetic and ferromagnetic behaviours in GO and RGO, respectively. Whereas, at low temperatures (below T = 60–70 K), both materials show paramagnetic behaviour.

  15. Nanocomposite of CeO.sub.2./sub. and high-coercivity magnetic carrier with large specific surface area

    Czech Academy of Sciences Publication Activity Database

    Řezníčková Mantlíková, Alice; Plocek, Jiří; Pacáková, Barbara; Kubíčková, Simona; Vik, Ondřej; Nižňanský, D.; Šlouf, Miroslav; Vejpravová, Jana

    2016-01-01

    Roč. 2016, Nov (2016), s. 1-13, č. článku 7091241. ISSN 1687-4110 R&D Projects: GA ČR(CZ) GA15-01953S; GA MŠk(CZ) LO1507 Institutional support: RVO:68378271 ; RVO:61388980 ; RVO:61389013 Keywords : cobalt ferrite * cerium oxide * nanoparticles * catalysis Subject RIV: BM - Solid Matter Physics ; Magnetism; CD - Macromolecular Chemistry (UMCH-V); CA - Inorganic Chemistry (UACH-T) Impact factor: 1.871, year: 2016

  16. Investigation of energy losses in low-coercivity resin-bonded magnets in alternating magnetic fields

    Science.gov (United States)

    Milov, E. V.; Sipin, I. A.; Milov, V. N.; Andreenko, A. S.; Balan, I. A.

    2017-01-01

    Energy losses during alternating remagnetization of low-coercitivity resin-bonded magnets and commercially produced electrical steels were studied experimentally. The studies were conducted on several samples of resin-bonded magnets with different manufacturing technologies and samples of electrical steel sheets of various thicknesses. The static and dynamic magnetic properties of the samples were measured on a vibration magnetometer and a specially designed apparatus, respectively. It was found that the studied samples of bonded magnets have a relatively high level of hysteresis losses associated with high coercivity, which reaches a value of 4-5 Oe. At the same time, the remagnetization losses due to the Foucault currents in the bonded magnets are considerably lower than in electrical steels. The measurement results show that bonded magnets at high frequencies of remagnetization, especially in high-rpm motors, can be competitive in comparison with electrical steels.

  17. Formation and characterization of magnetic barium ferrite hollow fibers with low coercivity via co-electrospun

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gui-fang, E-mail: guifang777@163.com; Zhang, Zi-dong, E-mail: 1986zzd@163.com; Dang, Feng, E-mail: dangfeng@sdu.edu.cn; Cheng, Chuan-bing, E-mail: 807033063@qq.com; Hou, Chuan-xin, E-mail: 710313782@qq.com; Liu, Si-da, E-mail: superliustar@hotmail.com

    2016-08-15

    BaFe{sub 12}O{sub 19} fibers and hollow fibers were successfully prepared by electrospun and co-electrospun. A very interesting result appeared in this study that hollow fibers made by co-electrospun showed low coercivity values of a few hundred oersteds, compared with the coercivity values of more than thousand oersteds for the fibers made by electrospun. So the hollow fibers with high saturation magnetization (M{sub s}) and while comparatively low coercivity (H{sub c}) exhibited strong magnetism and basically showed soft character. And this character for hollow fibers will lead to increase of the permeability for the samples which is favorable for impedance matching in microwave absorption. So these hollow fibers are promised to have use in a number of applications, such as switching and sensing applications, electromagnetic materials, microwave absorber. - Highlights: • BaFe{sub 12}O{sub 19} fibers were prepared via electrospinning successfully. • The coercivity has a value of a few hundred oersteds for the hollow fibers made by coaxial electrospun. • BaFe{sub 12}O{sub 19} with high saturation magnetization and low coercivity shows great potential in microwave absorbing application.

  18. High coercivity in nanostructured Co-ferrite thin films

    Indian Academy of Sciences (India)

    Abstract. Three methods including sol–gel, rf sputtering and pulsed laser deposition (PLD) have been used for the fabrication of high coercivity Co-ferrite thin films with a nanocrystalline structure. The PLD method is demonstrated to be a possible tool to achieve Co-ferrite films with high coercivity and small grain size at.

  19. Factors affecting coercivity in rare-earth based advanced permanent magnet materials

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, L.H. [Brookhaven National Lab., Upton, NY (United States); Sellers, C.H. [Lockheed Idaho Technologies Co., Idaho Falls, ID (United States); Panchanathan, V. [Magnequench International, Inc., Anderson, IN (United States)

    1997-02-01

    The relationships that link microstructural properties of advanced permanent magnet materials with magnetic properties such as the coercivity are often difficult to quantify, especially in materials with nano-scale structures. Recent work on RE{sub 2}Fe{sub 14}B-based powders fabricated with rapid-solidification techniques such as inert gas atomization (IGA) and melt-spinning provide insight into the nanostructural features which affect the acquisition and stability of coercivity. In all cases the coercivity is found to be a function of both the scale of the constituent microstructure and of the presence and distribution of minor phases.

  20. Anamolous reduction of magnetic coercivity of graphene oxide and reduced graphene oxide upon cooling

    OpenAIRE

    Bagani, K.; Bhattacharya, A; Kaur, J.; Chowdhury, A. Rai; Ghosh, B.; Sardar, M.; Banerjee, S.

    2013-01-01

    In this report we present the temperature evolution of magnetic coercivity of graphene oxide (GO) and reduced graphene oxide (RGO). We report an anamolous decrease in coercivity of GO and RGO with decreasing temperature. We could explain this anamolous behavior invoking the inherent presence of ripple in graphene. We observe antiferromagnetic and ferromagnetic behavior at room temperature for GO and RGO respectively, but at low temperatures both shows paramagnetic behavior.

  1. Coercivity enhancement of (Nd,Ce)-Fe-B sintered magnets by doping Nd-Fe additives

    Science.gov (United States)

    Chen, K.; Guo, S.; Fan, X. D.; Ding, G. F.; Di, J. H.; Chen, R. J.; Lee, D.; Yan, A. R.

    2017-02-01

    The effect of Nd-Fe additives on magnetic properties and microstructure in (Nd,Ce)-Fe-B sintered magnet has been investigated. By doping 3wt% Nd-Fe additives, the coercivity of the magnet increases from 10.56kOe to 12.69kOe with slight remanence decrease. Microstructure observation reveals that the volume fraction of the grain boundary phase increases accompanying with the thickening of the thin grain boundary between the adjacent grains. The RE6Fe13Cu phase which has low melting temperature develops at the triple junction position and the out shell of the matrix grains get magnetically hardened with 3wt% Nd-Fe additives. The results of the dynamic magnetic domains between the original magnet and processed magnet elucidate that the formation of reversed magnetic domains are more difficult for the processed magnet which is the direct evidence to clarify the coercivity enhancement.

  2. Coercivity enhancement of (Nd,Ce-Fe-B sintered magnets by doping Nd-Fe additives

    Directory of Open Access Journals (Sweden)

    K. Chen

    2017-02-01

    Full Text Available The effect of Nd-Fe additives on magnetic properties and microstructure in (Nd,Ce-Fe-B sintered magnet has been investigated. By doping 3wt% Nd-Fe additives, the coercivity of the magnet increases from 10.56kOe to 12.69kOe with slight remanence decrease. Microstructure observation reveals that the volume fraction of the grain boundary phase increases accompanying with the thickening of the thin grain boundary between the adjacent grains. The RE6Fe13Cu phase which has low melting temperature develops at the triple junction position and the out shell of the matrix grains get magnetically hardened with 3wt% Nd-Fe additives. The results of the dynamic magnetic domains between the original magnet and processed magnet elucidate that the formation of reversed magnetic domains are more difficult for the processed magnet which is the direct evidence to clarify the coercivity enhancement.

  3. Interdiffusion Processes in High-Coercivity RF-Sputtered Alnico Thin Films on Si Substrates

    Science.gov (United States)

    Mohseni, F.; Baghizadeh, A.; Lourenço, A. A. C. S.; Pereira, M. J.; Amaral, V. S.; Vieira, J. M.; Amaral, J. S.

    2017-08-01

    Alnico V thin film samples with the thickness of 100 nm were prepared by radio-frequency sputtering on Si substrates with and without a SiO2 layer. Heat treatment of the as-deposited thin films in above ambient pressure in an Ar atmosphere at a temperature range of 600-900°C, followed by quenching and/or slow cooling, leads to higher coercivity values compared to bulk Alnico magnets. Annealing at 800°C followed by quenching results in the highest coercivity reported here of 1.8 kOe. The formation of several triangular-shaped features along the interface between the substrate and the film were observed. A high-resolution transmission electron microscope analysis showed these to be formed via interdiffusion of Fe, Co and Ni atoms into the Si substrate. These features show a large difference in lattice parameters compared with the magnetically soft bulk Fe-Co-Si alloys, and a heterogeneous or layered magnetic ion distribution inside these features could be the origin of the high coercivity observed in the heat-treated films.

  4. Application of a novel flash-milling procedure for coercivity development in nanocrystalline MnAl permanent magnet powders

    Science.gov (United States)

    Rial, J.; Villanueva, M.; Céspedes, E.; López, N.; Camarero, J.; Marshall, L. G.; Lewis, L. H.; Bollero, A.

    2017-03-01

    This study shows the possibility of dramatically tuning microstructure and magnetic properties of gas-atomized Mn54Al46 particles by milling for an unprecedented duration of 30 s. This flash-milling procedure avoids the high temperatures typically achieved in lengthy conventional ball milling experiments, and is efficient to reduce the crystallite size to the nanometer scale, induce microstructural strain and ease phase transformations. This leads to the creation of the τ-MnAl phase providing magnetization, and the β-Mn phase operating in the mechanism for coercivity development. Post-annealing at 355 °C for 10 min results in a coercivity about three times larger than that of the annealed starting material, and thus reduces the optimum processing temperature in 75 °C by comparison with that needed for the latter to achieve the best combination of magnetic properties. A maximum obtained coercivity exceeding 5 kOe compares to the highest values reported to date for isotropic MnAl powders attained after milling for times above 20 h. This high coercivity is of additional relevance for further consideration of this material as a hard magnetic phase in the preparation of nanocomposite permanent magnets. The combination of the cost-efficient synthesis technique (gas-atomization) and novel processing route (flash-milling) for the production of low-cost isotropic nanocrystalline MnAl powders, opens new paths to the possible mass production of these materials as an alternative to permanent magnets containing critical raw materials.

  5. Coercivity in SmCo hard magnetic films for MEMS applications

    Energy Technology Data Exchange (ETDEWEB)

    Pina, E. [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain)]. E-mail: epina@renfe.es; Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid-CSIC, c/ Sor Juana Ines de la Cruz s/n, 28049 Madrid (Spain); Garcia, M.A. [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain); Cebollada, F. [Departamento de Fisica Aplicada a las Telecomunicaciones, EUITT-UPM, Crtra. De Valencia km 7, 28031 Madrid (Spain); Hoyos, A. de [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain); Romero, J.J. [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain); Hernando, A. [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain); Unidad asociada ICMM-IMA. P.O. Box 155, 28230 Las Rozas Madrid (Spain); Gonzalez, J.M. [Unidad asociada ICMM-IMA. P.O. Box 155, 28230 Las Rozas Madrid (Spain)

    2005-04-15

    In this work we have investigated the thermal dependence of coercivity in 1.5 {mu}m thick SmCo{sub 5} films fabricated by sputtering technique. Samples were deposited onto Si substrates kept at different temperatures. Samples grown below 450 deg. C are amorphous, present low coercivity and require further crystallization processes in order to obtain the 1:5 SmCo hard phase. Samples grown at 450 deg. C are nanocrystalline in the as-deposited state and exhibit high room temperature in-plane coercivity. Correlation between the thermal dependence of coercivity and the nanostructure has been analyzed in the frame of the so-called micromagnetic model.

  6. Hard magnetic properties and coercivity mechanism of melt-spun Misch Metal-Fe-B alloy

    Energy Technology Data Exchange (ETDEWEB)

    Quan, Ningtao; Luo, Yang, E-mail: eluoyang@foxmail.com; Yan, Wenlong; Yuan, Chao; Yu, Dunbo; Sun, Liang; Lu, Shuo; Li, Hongwei; Zhang, Hongbin

    2017-09-01

    Highlights: • Melt-spun MM{sub 13}Fe{sub 81}B{sub 6} alloy shows that the distributions of the La, Ce, Pr, Nd, Fe and B elements is uniformly distributed, and the grain size is in the range of 30–40 nm, it can be seen that Pr-rich and La-rich phases concentrated on grain boundaries, which resulted in the coercivity augment with the increase of MMFe{sub 2} content, and the grain size is around 40–50 nm in MM{sub 16}Fe{sub 78}B{sub 6}. • There is a significant formation of MMFe{sub 2} with abundant Pr and La, and a small amount of Ce and Nd enriched at the interfacial region in MM{sub 16}Fe{sub 78}B{sub 6}, thus an inhomogeneous region was formed. It is considered that the inhomogeneous region is effective in increasing the coercivity. • The optimum-quenched MM{sub 13}Fe{sub 81}B{sub 6} alloy have been shown to exhibit a coercive force of 6.9 kOe and an energy product of 8.5 MGOe, which is superior to anisotropic ferrite magnets of 4.5 MGOe. - Abstract: Magnetic and structural properties of Misch Metal (MM)-Fe-B alloys, were examined in the melt-spun ribbons. Melt-spun MM-Fe-B samples were prepared at the surface velocities of 18–30 m/s. Crystalline structure and their room-temperature magnetization characteristics were analyzed, and the optimum surface velocity of 20 m/s and nominal composition of MM{sub 13}Fe{sub 81}B{sub 6} were obtained. Microstructural analyses indicate that the grain size is approximately 30–50 nm in the alloys with the optimum characteristics. In the MM{sub 16}Fe{sub 78}B{sub 6} alloys, Pr-rich and La-rich phases concentrated on grain boundaries, which resulted in the coercivity augment with the increase of MMFe{sub 2} content. Dependence of coercivity on applied magnetic field suggested that the mechanism of coercivity in moderate MM-content samples was inhomogeneous domain wall pinning type. The melt-spun ribbons in the optimum condition exhibit a coercive force of 6.9 kOe and an energy product of 8.5 MGOe, which can be used as

  7. Observation of high coercive fields in chemically synthesized coated Fe-Pt nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Dalavi, Shankar B.; Panda, Rabi N., E-mail: rnp@goa.bits-pilani.ac.in

    2017-04-15

    Nanocrystalline Fe-Pt alloys have been synthesized via chemical reduction route using various capping agents; such as: oleic acid/oleylamine (route-1) and oleic acid/CTAB (route-2). We could able to synthesize Fe50Pt and Fe54Pt alloys via route 1 and 2, respectively. As-prepared Fe-Pt alloys crystallize in disordered fcc phase with crystallite sizes of 2.3 nm and 6 nm for route-1 and route-2, respectively. Disordered Fe-Pt alloys were transformed to ordered fct phase after annealing at 600 °C. SEM studies confirm the spherical shape morphologies of annealed Fe-Pt nanoparticles with SEM particle sizes of 24.4 nm and 21.2 nm for route-1 and route-2, respectively. TEM study confirms the presence of 4.6 nm particles for annealed Fe50Pt alloys with several agglomerating clusters of bigger size and appropriately agrees well with the XRD study. Room temperature magnetization studies of as-prepared Fe-Pt alloys (fcc) show ferromagnetism with negligible coercivities. Average magnetic moments per particle for as-prepared Fe-Pt alloys were estimated to be 753 μ{sub B} and 814 μ{sub B}, for route 1 and 2, respectively. Ordered fct Fe-Pt alloys show high values of coercivities of 10,000 Oe and 10,792 Oe for route-1 and route-2, respectively. Observed magnetic properties of the fct Fe-Pt alloys nps were interpreted with the basis of order parameters, size, surface, and composition effects. - Highlights: • Synthesis of capped nanocrystalline Fe-Pt alloys via chemical routes. • Ordered fct phase were obtained at 600 °C. • Microstructural studies were carried out using SEM and TEM. • Investigation on evolution of magnetic properties from fcc to fct state. • Maximum values of coercivities up to 10,792 Oe were observed.

  8. Investigating Size- and Temperature-Dependent Coercivity and Saturation Magnetization in PEG Coated Fe3O4 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Chiranjib Nayek

    2017-05-01

    Full Text Available Polyethylene glycol (PEG coated magnetic Fe3O4 nanoparticles with diameters of 12 nm, 15 nm, and 16 nm were synthesized by the usual co-precipitation method. The structure and morphology of the samples were characterized using X-ray diffraction (XRD and high resolution transmission electron microscopy (HRTEM. The ac magnetic susceptibility measurements were carried out using a vibrating sample magnetometer (VSM. The dc magnetic measurements were carried out using a commercial Quantum Design superconducting quantum interference device (SQUID. The XRD patterns indicated the sole existence of the inverse cubic spinel phase of Fe3O4 in all the samples. The histograms extracted from the TEM images show narrow size distributions with average sizes that are very similar to those obtained from the XRD images using the Scherrer’s formula. The temperature dependence of both coercivity and saturation magnetization, which were determined from the magnetic hysteresis loops, were found to have considerable deviations from the Bloch’s and Kneller’s laws. The size-dependent coercivity and saturation magnetization were found to be non-monotonic at nearly all temperatures. These results are discussed and attributed mainly to the finite size effects in addition to the existence of inter-particle interactions and of spin-glass structures that resulted from frozen canted surface spins at low temperatures.

  9. Coercivity enhancement in hot deformed Nd2Fe14B-type magnets by doping low-melting RCu alloys (R = Nd, Dy, Nd + Dy)

    Science.gov (United States)

    Lee, Y. I.; Huang, G. Y.; Shih, C. W.; Chang, W. C.; Chang, H. W.; You, J. S.

    2017-10-01

    Magnetic properties of the anisotropic NdFeB magnets prepared by hot pressing followed by die-upsetting NdFeB MQU-F powders doped with low-melting RCu alloy powders were explored, where RCu stands for Nd70Cu30, Dy70Cu30 and (Nd0.5Dy0.5)70Cu30, respectively. In addition, the post-annealing at 600 °C was employed to modify the microstructures and the magnetic properties of the hot deformed magnets. It is found that doping RCu alloy powders is effective in enhancing the coercivity of the hot deformed NdFeB magnets from 15.1 kOe to 16.3-19.5 kOe. For Nd70Cu30-doped magnets, the increment of coercivity is only 1.2 kOe. Meanwhile, Dy70Cu30-doped and (Nd0.5Dy0.5)70Cu30-doped magnets show an almost identical enhancement of coercivity of about 4.4 kOe. Importantly, the latter magnet shows a beneficial effect of reducing the usage of Dy from 1.6 wt% to 0.8 wt%. TEM analysis shows that nonmagnetic Nd, Dy and Cu appear at grain boundary and isolate the magnetic grains, leading to an enhancement of coercivity. Doping lower melting point Dy-lean (Nd0.5Dy0.5)70Cu30 powders into commercial MQU-F powders for making high coercivity hot deformed NdFeB magnets might be a potential and economic way for mass production.

  10. In-plane magnetic anisotropy and coercive field dependence upon thickness of CoFeB

    Energy Technology Data Exchange (ETDEWEB)

    Kipgen, Lalminthang; Fulara, Himanshu; Raju, M. [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Chaudhary, Sujeet, E-mail: sujeetc@physics.iitd.ac.in [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

    2012-09-15

    The structural and magnetic properties of as-grown 5-50 nm thin ion-beam sputter deposited transition metal-metalloid Co{sub 20}Fe{sub 60}B{sub 20} (CFB) films are reported in this communication. A broad peak observed at 2{theta}{approx}45 Degree-Sign in the glancing angle X-ray diffraction pattern revealed the formation of very fine nano-sized grains embedded in majority amorphous CFB matrix. Although no magnetic field is applied during deposition, the longitudinal magneto-optic Kerr effect measurements performed at 300 K in these as-grown films clearly established the presence of in-plane uniaxial magnetic anisotropy (K{sub u}). It is argued that this observed anisotropy is strain-induced. This is supported by the observed dependence of direction of K{sub u} on the angle between applied magnetic field and crystallographic orientation of the underlying Si(100) substrate, and increase in the coercivity with the increase of the film thickness. - Highlights: Black-Right-Pointing-Pointer We study the ion-beam sputter deposited CoFeB film by MOKE and GAXRD. Black-Right-Pointing-Pointer A nanocrystalline structure is observed in the GAXRD pattern. Black-Right-Pointing-Pointer Coercivity increases with increase in film thickness. Black-Right-Pointing-Pointer In-plane magnetic anisotropy is observed. Black-Right-Pointing-Pointer The dominant contribution to magnetic anisotropy is strain induced magnetic anisotropy.

  11. Coercivity Distributions of Soft-Magnetic Components and Their Occurrence in Sediments ANS Sedimentary Rocks

    Science.gov (United States)

    Egli, R.; Spassov, S.; Heller, F.

    2003-12-01

    The analysis of magnetization curves with model functions is a valuable tool for identifying magnetic mineral sources in sediments and sedimentary rocks. The method is limited by two main factors: the ability of the model function in reproducing appropriately the magnetic properties of an individual component, and its extreme sensitivity to measurement errors. Both factors influence the number of components, which are needed to fit a magnetization curve within the measurement error. Recent investigations on the shape of coercivity distributions (Heslop, 2003; Egli 2003) support the use of model functions introduced by Egli (2003). Extremely detailed measurements of alternating field (AF) demagnetisation curves of isothermal (IRM) and anhysteretic (ARM) remanent magnetizations have been performed on a wide variety of sediments and sedimentary rocks including sediments from rivers, lakes and oceans, recent soils, paleosols, loesses, red clays, limestones and also on atmospheric dusts, urban pollution and magnetotactic bacteria. The component analysis allowed the identification of several magnetic components with specific properties, which reflect different magnetic mineral sources: extracellular, bacterial and pedogenic magnetite, lithogenic minerals transported by water or in air, and magnetic minerals associated to anthropogenic pollution sources. Each magnetic component is described by nine parameters: four for the shape of the IRM, four for the shape of the ARM coercivity distribution, and one for the ratio of the ARM to the IRM. By comparing similar components occurring in different samples, empirical relations can be established between different parameters, which reflect fundamental physical processes that control the shape of coercivity distributions. As a consequence, only four parameters, so-called magnetic fingerprints, are necessary to characterise a magnetic component. The effect of environmental changes on the magnetic properties of specific magnetic

  12. Enhanced coercivity in Co-doped α-Fe2O3 cubic nanocrystal assemblies prepared via a magnetic field-assisted hydrothermal synthesis

    Directory of Open Access Journals (Sweden)

    Kinjal Gandha

    2017-05-01

    Full Text Available Ferromagnetic Co-doped α-Fe2O3 cubic shaped nanocrystal assemblies (NAs with a high coercivity of 5.5 kOe have been synthesized via a magnetic field (2 kOe assisted hydrothermal process. The X-ray diffraction pattern and Raman spectra of α-Fe2O3 and Co-doped α-Fe2O3 NAs confirms the formation of single-phase α-Fe2O3 with a rhombohedral crystal structure. Electron microscopy analysis depict that the Co-doped α-Fe2O3 NAs synthesized under the influence of the magnetic field are consist of aggregated nanocrystals (∼30 nm and of average assembly size 2 μm. In contrast to the NAs synthesized with no magnetic field, the average NAs size and coercivity of the Co-doped α-Fe2O3 NAs prepared with magnetic field is increased by 1 μm and 1.4 kOe, respectively. The enhanced coercivity could be related to the well-known spin–orbit coupling strength of Co2+ cations and the redistribution of the cations. The size increment indicates that the small ferromagnetic nanocrystals assemble into cubic NAs with increased size in the magnetic field that also lead to the enhanced coercivity.

  13. Enhanced coercivity in Co-doped α-Fe2O3 cubic nanocrystal assemblies prepared via a magnetic field-assisted hydrothermal synthesis

    Science.gov (United States)

    Gandha, Kinjal; Mohapatra, Jeotikanta; Poudyal, Narayan; Elkins, Kevin; Liu, J. Ping

    2017-05-01

    Ferromagnetic Co-doped α-Fe2O3 cubic shaped nanocrystal assemblies (NAs) with a high coercivity of 5.5 kOe have been synthesized via a magnetic field (2 kOe) assisted hydrothermal process. The X-ray diffraction pattern and Raman spectra of α-Fe2O3 and Co-doped α-Fe2O3 NAs confirms the formation of single-phase α-Fe2O3 with a rhombohedral crystal structure. Electron microscopy analysis depict that the Co-doped α-Fe2O3 NAs synthesized under the influence of the magnetic field are consist of aggregated nanocrystals (˜30 nm) and of average assembly size 2 μm. In contrast to the NAs synthesized with no magnetic field, the average NAs size and coercivity of the Co-doped α-Fe2O3 NAs prepared with magnetic field is increased by 1 μm and 1.4 kOe, respectively. The enhanced coercivity could be related to the well-known spin-orbit coupling strength of Co2+ cations and the redistribution of the cations. The size increment indicates that the small ferromagnetic nanocrystals assemble into cubic NAs with increased size in the magnetic field that also lead to the enhanced coercivity.

  14. MAX UnMix: Introducing a new web application for unmixing magnetic coercivity distributions

    Science.gov (United States)

    Feinberg, J. M.; Maxbauer, D.; Fox, D. L.

    2016-12-01

    Magnetic minerals are present in a wide variety of natural systems and are often indicative of the natural or anthropogenic processes that led to their deposition, formation, or transformation. Unmixing the contribution of magnetic components to bulk field-dependent magnetization curves has become increasingly common in environmental and rock magnetic studies and has enhanced our ability to fingerprint the magnetic signatures of magnetic minerals with distinct compositions, grain sizes, and origins. A variety of programs have been developed over the past two decades to allow researchers to deconvolve field-dependent magnetization curves for these purposes, however many of these programs are either outdated or have obstacles that inhibit the programs usability. MAX UnMix is a new web application (available online at http://www.irm.umn.edu/maxunmix) built using the `shiny' package for R-studio that can be used to process coercivity distributions derived from magnetization curves (acquisition, demagnetization, or backfield data) via an online user-interface. Here, we use example datasets from lake sediments and paleosols to present details of the MAX UnMix model and the programs functionality. MAX UnMix is designed to be accessible, user friendly, and should serve as a useful resource for future research.

  15. Synthesis and characterization of CoFe{sub 2}O{sub 4} nanoparticles with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Gandha, Kinjal; Elkins, Kevin; Poudyal, Narayan; Ping Liu, J., E-mail: pliu@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, Texas 76019 (United States)

    2015-05-07

    Single crystalline CoFe{sub 2}O{sub 4} nanoparticles with high coercivity were prepared via a one-step hydrothermal method. The shape and size of the nanocrystals (in the range of 20–100 nm) can be controlled by varying synthesis parameters such as the concentration of NaOH and CTAB. X-ray diffraction and Raman spectra analysis confirmed that all the as-synthesized nanoparticles have a face centered cubic spinel crystal structure. HRTEM observation of particles shows interlayer spacing 0.48 nm of (111) lattice planes. A coercive force up to 5.0 kOe and saturation magnetization of 73 emu/g was achieved at room temperature for the 40 nm CoFe{sub 2}O{sub 4} nanoparticles.

  16. Structural, magnetic characterization (dependencies of coercivity and loss with the frequency) of magnetic cores based in Finemet

    Science.gov (United States)

    Osinalde, M.; Infante, P.; Domínguez, L.; Blanco, J. M.; del Val, J. J.; Chizhik, A.; González, J.

    2017-12-01

    We report changes of coercivity, induced magnetic anisotropy, magneto-optical domain structure and frequency dependencies of coercivity and energy loss (up to 10 MHz) associated with the structural modifications produced by thermal treatments under applied magnetic field (field annealing) in toroidal wound cores of Fe73.5Cu1Nb3Si15.5B7 amorphous alloy. The thermal treatment (535 °C, 1 h) leads to the typical nanocrystalline structure of α-Fe(Si) nanograins (60-65% relative volume, 10-20 nm average grain size embedded in a residual amorphous matrix, while the magnetic field with the possibility to be applied in two directions to the toroidal core axis, that is in transverse (which is equivalent to the transverse direction of the ribbon) or longitudinal (equivalent to the longitudinal direction of the ribbon), develops a macroscopic uniaxial magnetic anisotropy in the transverse (around 245 J/m3) or longitudinal (around 85 J/m3) direction of the ribbon, respectively. It is remarkable the quasi-unhysteretic character of the cores with these two kinds of field annealing as comparing with that of the as-quenched one. Magneto-optical study by Kerr-effect of the ribbons provides useful information on the domain structure of the surface in agreement with the direction and intensity of the induced magnetic anisotropy. This induced uniaxial magnetic anisotropy plays a very important role on the Hc(f) and EL(f) curves, (f: frequency), being drastic the presence and direction of the induced magnetic anisotropy. In addition, these frequency dependencies show a significant change at the frequency around 100 Hz.

  17. Variation of coercivity with Ce content in (Pr,Nd,Ce2Fe14B sintered magnets

    Directory of Open Access Journals (Sweden)

    Xue-feng Zhang

    2017-05-01

    Full Text Available The variation of coercivity with Ce content was investigated in (Pr,Nd15-xCexFe77B8 (x=0∼10 sintered magnets. The coercivity of magnets largely decreases from 10.22 to 5.4 kOe with increasing x from 0 to 2. The coercivity rises to 7.68 kOe when x=3 and then decreases again with further increasing Ce content. However, both the magnetocrystalline anisotropy and Curie temperature decrease monotonically with increasing Ce content. EDS composition analysis shows that the Ce concentration in the Re2Fe14B main phase is higher than that in the nominal composition when x≤3, but becomes lower when x>3. These results indicate that Ce tends to be expelled from the main phase and segregates at or near the grain boundary regions if Pr-Nd is excessively substituted by Ce. The change of relative solubility of Ce in Re2Fe14B would lead to the change of distributions of Ce and Pr-Nd elements, and thus result in the change of anisotropy at the grain outer layer, contributing to the abnormal behavior of coercivity. These studied results are also expected to provide a guideline for optimizing the composition design of resource-saving permanent magnets.

  18. Neem leaves mediated preparation of NiO nanoparticles and its magnetization, coercivity and antibacterial analysis

    Science.gov (United States)

    Helan, V.; Prince, J. Joseph; Al-Dhabi, Naif Abdullah; Arasu, Mariadhas Valan; Ayeshamariam, A.; Madhumitha, G.; Roopan, Selvaraj Mohana; Jayachandran, M.

    Nickel oxides nanoparticles (NiO NPs) were synthesized by biosynthesis method with the help of phytoconstituents present in the neem leaf. Further the synthesized NiO NPs were subjected for structural, optical, morphological and magnetic properties. The XRD patterns clearly infer the presence of polycrystalline nature of samples (0 1 0), (0 1 1) and (0 1 2) with hexagonal crystal phase. Morphological studies using Transmission Electron Microscope (TEM) reveals that the biosynthesized NiO NPs were in shape of oblong with 12 nm in size. Elemental analysis (EDAX) confirms the quantity of Ni is present at 51% and remaining O as 49% as well as the mass magnetization values of 61 emu/g are also recorded for NiO NPs and its coercivity values in the range of 0.2-0.4 of nanoparticles respectively. Finally the NiO NPs was studied for bacterial activity against Staphylococcus aureus (MTCC 1430) and followed by Escherichia coli (MTCC 739) by agar diffusion assay.

  19. Reversal mechanisms and interactions in magnetic systems: coercivity versus switching field and thermally assisted demagnetization

    Directory of Open Access Journals (Sweden)

    Cebollada, F.

    2005-06-01

    Full Text Available In this paper we present a comparative analysis of the magnetic interactions and reversal mechanisms of two different systems: NdFeB-type alloys with grain sizes in the single domain range and Fe-SiO2 nanocomposites with Fe concentrations above and below the percolation threshold. We evidence that the use of the coercivity as the main parameter to analyse them might be misleading due to the convolution of both reversible and irreversible magnetization variations. We show that the switching field and thermally assisted demagnetization allow a better understanding of these mechanisms since they involve just irreversible magnetization changes. Specifically, the experimental analysis of the coercivity adquisition process for the NdFeB-type system suggests that the magnetization reversal is nucleated at the spin misalignments present due to intergranular exchange interactions. On the other hand, the study of the magnetic viscosity and of the isothermal remanent magnetization (IRM and direct field demagnetization (DCD remanence curves indicates that the dipolar interactions are responsible for the propagation of the switching started at individual particles.

    En este artículo presentamos un análisis comparativo de la influencia de la microestructura a través de las interacciones magnéticas en los mecanismos de inversión de la magnetización en dos sistemas diferentes: aleaciones tipo NdFeB con tamaños de grano en el rango de monodominio y nanocompuestos de Fe-SiO2 con concentraciones de Fe tanto por encima como por debajo del umbral de percolación. Ponemos de manifiesto que el uso del campo coercitivo como parámetro de análisis puede llevar a equívocos debido a la coexistencia de variaciones reversibles e irreversibles de la magnetización. También mostramos que el campo de conmutación y la desimanación térmicamente asistida permiten una mejor comprensión de dichos mecanismos ya que reflejan exclusivamente cambios irreversibles de

  20. 52.7 kOe high coercivity in Sm(Co0.9Cu0.14.8 melt-spun ribbons

    Directory of Open Access Journals (Sweden)

    Suresh Koppoju

    2015-07-01

    Full Text Available Fine grained Cu substituted melt-spun Sm(Co0.9Cu0.14.8 ribbons prepared with a wheel speed of 50 m/s exhibit a high coercivity of 52.7 kOe. Detailed magnetic studies like I and II quadrant magnetization-demagnetization characteristics, minor-loop measurement with increasing field and recoil behaviour have been carried out in combination with TEM studies. Fine spots of size ∼3 nm having different crystallographic orientations within the grains have been observed, and the high coercivity of the sample is attributed to complex domain wall interactions with the fine grain (∼55 nm microstructure containing nanoscale heterogeneities.

  1. Coercivity enhancement in (Ce,Nd)-Fe-B sintered magnets prepared by adding NdH{sub x} powders

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Le-le [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); School of Science, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Li, Zhu-bai, E-mail: lzbgj@163.com [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Ma, Qiang; Li, Yong-feng; Zhao, Qian [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); School of Science, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Zhang, Xue-feng, E-mail: xuefeng056@163.com [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); School of Science, Inner Mongolia University of Science and Technology, Baotou 014010 (China)

    2017-08-01

    (Ce,Nd)-Fe-B sintered magnets were prepared by the addition of NdH{sub x} powders in Ce{sub 9}Nd{sub 4.5}Fe{sub 80}B{sub 6.5} powders. The coercivity is rather low in Ce{sub 9}Nd{sub 4.5}Fe{sub 80}B{sub 6.5} magnets, and Ce element prefers to distribute at the outer-layer of main phase (Ce,Nd){sub 2}Fe{sub 14}B. The investigation of scanning electron microscope shows that the addition of NdH{sub x} powders leads to the increase of Nd content at grain outer-layer of main phase owing to the element diffusion. Magnetization reversal undergoes the nucleation of reversed domain wall at grain outer-later, and the addition of NdH{sub x} powders leads to the increase in the nucleation field of reversed domain, giving rise to the significant improvement of coercivity. The larger amount addition of NdH{sub x} powders leads to the increase in the amount of intergranular phase, resulting in the decreases of the remanence, the squareness of demagnetization curve and the maximum energy product.

  2. Coercivity enhancement in (Ce,Nd)-Fe-B sintered magnets prepared by adding NdHx powders

    Science.gov (United States)

    Zhang, Le-le; Li, Zhu-bai; Ma, Qiang; Li, Yong-feng; Zhao, Qian; Zhang, Xue-feng

    2017-08-01

    (Ce,Nd)-Fe-B sintered magnets were prepared by the addition of NdHx powders in Ce9Nd4.5Fe80B6.5 powders. The coercivity is rather low in Ce9Nd4.5Fe80B6.5 magnets, and Ce element prefers to distribute at the outer-layer of main phase (Ce,Nd)2Fe14B. The investigation of scanning electron microscope shows that the addition of NdHx powders leads to the increase of Nd content at grain outer-layer of main phase owing to the element diffusion. Magnetization reversal undergoes the nucleation of reversed domain wall at grain outer-later, and the addition of NdHx powders leads to the increase in the nucleation field of reversed domain, giving rise to the significant improvement of coercivity. The larger amount addition of NdHx powders leads to the increase in the amount of intergranular phase, resulting in the decreases of the remanence, the squareness of demagnetization curve and the maximum energy product.

  3. Design and fabrication of sintered Nd-Fe-B magnets with a low temperature coefficient of intrinsic coercivity

    Directory of Open Access Journals (Sweden)

    Cui X.G.

    2009-01-01

    Full Text Available To decrease the temperature coefficients of sintered Nd-Fe-B magnets, the influencing factors on temperature coefficients, especially the reversible temperature coefficient β of intrinsic coercivity Hcj, were analyzed. The results showed that the absolute value of β decreased with increasing Hcj and also the ratio of microstructure parameter c to Neff, indicating that the increase of magnetocrystalline anisotropy field HA and c/Neff can effectively decrease the absolute value of β. On the basis of this analysis, a sintered Nd-Fe-B magnet with a low temperature coefficient of Hcj was fabricated through composition design, and the value of β was only -0.385%/ºC in the temperature interval of 20-150ºC.

  4. Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film

    Science.gov (United States)

    Shirsath, Sagar E.; Liu, Xiaoxi; Yasukawa, Yukiko; Li, Sean; Morisako, Akimitsu

    2016-01-01

    Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate. PMID:27435010

  5. Fourfold magnetic anisotropy, coercivity and magnetization reversal of Co/V bilayers grown on MgO(0 0 1)

    Energy Technology Data Exchange (ETDEWEB)

    Calleja, J F [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Muro, M GarcIa del [Departament de Fisica Fonamental and Institut de Nanociencia i Nanotecnologia IN2UB de la Universitat de Barcelona, MartIi Franques, 1, E-08028 Barcelona (Spain); Presa, B [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Matarranz, R [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Corrales, J A [Departmento de Informatica, Universidad de Oviedo, Edificio Departamental 1, Campus de Viesques s/n, 33204 Gijon (Spain); Labarta, A [Departament de Fisica Fonamental and Institut de Nanociencia i Nanotecnologia IN2UB de la Universitat de Barcelona, MartIi Franques, 1, E-08028 Barcelona (Spain); Contreras, M C [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain)

    2007-11-21

    Magnetic anisotropy and magnetization reversal of Al/Co/V/MgO(0 0 1) thin films have been investigated. The films were fabricated by magnetron sputtering. The roles of both Co and V layers thicknesses have been studied. Magnetic characterization has been carried out by transverse susceptibility (TS) measurements and hysteresis loops. Cobalt is grown in the hcp structure on V with the c axis parallel to the film plane. Two types of hcp Co crystal are grown with the c axes perpendicular to each other. This structure gives rise to a fourfold magnetic anisotropy. When the V layer thickness is below 40 A a superimposed uniaxial anisotropy develops, the effect of which is a depression in the TS, in agreement with theoretical calculations. This uniaxial anisotropy is induced by the substrate and due to a discontinuous growth of the V layer. For hcp Co grown on V, the magnetic anisotropy rapidly increases with Co layer thickness. In this case, unexpected shifted hysteresis loops along the hard axes were observed when the films were not saturated. This has been explained by taking into account the magnetization reversal along the hard axis: it proceeds via magnetization rotation of some portions of the film at high fields, and by domain wall motion of the rest of the film at lower field values.

  6. Reply to "Comment on 'Performance of Halbach magnet with finite coercivity'"

    DEFF Research Database (Denmark)

    Insinga, Andrea Roberto; Bahl, Christian; Bjørk, Rasmus

    2017-01-01

    differential equation for the magnetic vector potential, derived from the Maxwell equations, incorporates all shape effects. On the other hand, the local constitutive relations express a point-wise link between, e.g., magnetic field and magnetic flux density, and are as such independent of geometry. We confirm...

  7. Synthesis, morphology and microstructure of pomegranate-like hematite ({alpha}-Fe{sub 2}O{sub 3}) superstructure with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Tadic, Marin, E-mail: marint@vinca.rs [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Citakovic, Nada [Military Academy, Generala Pavla Jurisica Sturma 33, University of Belgrade, 11000 Belgrade (Serbia); Panjan, Matjaz [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Stanojevic, Boban [Vinca Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, University of Belgrade (Serbia); Markovic, Dragana [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Jovanovic, Dorde [Center for Solid State Physics and New Materials, Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Spasojevic, Vojislav [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia)

    2012-12-05

    Highlights: Black-Right-Pointing-Pointer We found superior magnetic properties of the hematite ({alpha}-Fe{sub 2}O{sub 3}). Black-Right-Pointing-Pointer TEM and HRTEM images show a pomegranate-like superstructure. Black-Right-Pointing-Pointer Magnetic measurements display high coercivity H{sub C} = 4350 Oe at the room temperature. - Abstract: We found novel and superior magnetic properties of the hematite ({alpha}-Fe{sub 2}O{sub 3}) that originate from an internal microstructure of particles and strong inter-particle interactions between nanocrystal sub-units. The hematite particles were synthesized by thermal decomposition of iron (III) nitrate without any template or surfactant. The purity, size, crystallinity, morphology, microstructure and magnetic features of the as-prepared particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and SQUID magnetometry. An XRD study reveals a pure phase of {alpha}-Fe{sub 2}O{sub 3} whereas TEM shows {alpha}-Fe{sub 2}O{sub 3} spheres with a diameter of about 150 nm. RS also shows high quality and purity of the sample. Moreover, TEM and HRTEM images show a pomegranate-like superstructure and evidence that the spherical particles are composed of individual well-crystallized nanoparticle sub-units (self-assembled nanoparticles) with a size of about 20 nm. Magnetic measurements display hysteretic behavior at the room temperature with remanent magnetization M{sub r} = 0.731 emu/g, saturation magnetization M{sub S} = 6.83 emu/g and coercivity H{sub C} = 4350 Oe, as well as the Morin transition at T{sub M} = 261 K. These results and comparison with those in the literature reveal that the sample has extremely high coercivity. The magnetic properties of the sample are discussed in relation to morphology, internal microstructure, surface

  8. COERCIVITY AND VECTOR MAGNETIZATION ANALYSIS OF OBSIDIAN SAMPLES FROM THE TRANS-MEXICAN VOLCANIC BELT (Coercitividad y análisis de magnetización vectorial de muestras de obsidianas de la faja volcánica transmexicana

    Directory of Open Access Journals (Sweden)

    Jaime Urrutia-Fucugauchi

    2017-09-01

    Full Text Available This note presents initial results of a paleomagnetic study of obsidian from twenty localities in the eastern, central and western sectors of the Trans-Mexican volcanic belt in central Mexico. We focus on the coercivity and vector composition of the remanent magnetization, which are critical for paleodirectional and paleointensity studies. Alternating field demagnetization shows that obsidians carry single and two-component magnetizations residing in low- and high-coercivity magnetic minerals, with discrete and overlapping coercivity spectra. Magnetic minerals are likely iron-titanium oxides with fine-grain sizes characterized by pseudo-single domain states. ESPAÑOL: Se presentan los resultados preliminares del estudio de obsidianas de veinte localidades en los sectores este, central y oeste de la faja volcánica transmexicana. Los análisis se concentran en la coercitividad y la composición vectorial de la magnetización remanente, que son propiedades claves para evaluar los registros de direcciones e intensidades. La desmagnetización por campos alternos revela la presencia de magnetizaciones de una y dos componentes, que residen en minerales con baja y alta coercitividad con espectros que traslapan y discretos. Los minerales magnéticos son óxidos de hierro-titanio con grano fino y estados de dominio seudosencillo.

  9. Coercive diplomacy

    DEFF Research Database (Denmark)

    Jakobsen, Peter Viggo

    2016-01-01

    Coercive diplomacy (CD) involves the use of military threats and/or limited force in support of diplomatic negotiations relying on persuasion, rewards and assurances. This combination of coercion (sticks) and diplomacy (carrots) is as old as the practice of diplomacy, and it is typically employed...... when actors want to resolve war-threatening crises and conflicts without resorting to full-scale war. This chapter analyses the establishment of CD as a field of study during the Cold War and shows how the theory and practice of CD has evolved in response to the strategic challenges of the day. Four...... and conflicts short of full-scale war when the conditions are right. However, it is equally clear that our understanding of these conditions remains wanting in several respects. More research and scholarly attention are needed if we want to realize more of the potential for peaceful conflict resolution...

  10. Dynamic coercivity of Mo-doped FINEMETs

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Srimoy; Mandal, Kalyan; Sakar, Debashis [S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Cremaschi, Victoria J. [Lab. de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires-CONICET, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Member of CONICET (Argentina); Silveyra, Josefina M., E-mail: jsilveyra@fi.uba.a [Lab. de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires-CONICET, Paseo Colon 850, C1063ACV Buenos Aires (Argentina)

    2011-05-01

    The structure and the dc magnetic behavior of FINEMET-type alloys doped with molybdenum have been recently reported. Most commercial applications of these materials are, however, not at dc but at high magnetizing frequencies. Therefore, we report a study of the frequency dependence of coercivity, H{sub c}(f), in amorphous and nanocrystalline ribbons of composition Fe{sub 73.5}Si{sub 13.5}Nb{sub 3-x}Mo{sub x}B{sub 9}Cu{sub 1} (x=0, 1.5 and 3) in the frequency range from 0.5 to 1.3 kHz. The nature of H{sub c}(f) measurements revealed the influence of eddy currents in the magnetization of samples. The frequency dependence of coercivity did not vary with the molybdenum content in the amorphous samples. All the alloys exhibited a systematic improvement in the coercivity after nanocrystallization and it was found that this improvement was better as more Nb was replaced by Mo.

  11. Production of high-coercivity materials based on BaFe12O19 by crystallization of plasma-sputtered powders

    Science.gov (United States)

    Lepeshev, A. A.; Karpov, I. V.; Uschakov, A. V.

    2017-11-01

    Ferrite powders BaFe12O19 were studied in the present work after plasma heating and rapid quenching in differentenvironment: in air, in water and on the copper disk. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), vibration magnetometry (VSM) and Mossbauer spectroscopy (NGR) showed that the powder produced after quenching on the copper disk was in amorphous-crystalline state. The correlation between the annealing temperature and the value of magnetic parameters (coercive field and saturation magnetization) was established. Annealing at 1200 K for 2 h increases the coercive force up to 6.3 kOe. The processes of crystallization from the amorphous phase, that improve the magnetic properties of barium ferrite, are discussed. Highlights We studied the barium ferrite powdersafter plasma heating and rapid quenching. We studied the processes of crystallization from the amorphous phase. We studied theprocesses ofthermal annealing for the barium ferrite.

  12. Spin spring behavior in exchange coupled soft and high-coercivity hard ferromagnets.

    Energy Technology Data Exchange (ETDEWEB)

    Shull, R. D.; Shapiro, A. J.; Gornakov, V. S.; Nikitenko, V. I.; Jiang, J. S.; Kaper, H.; Leaf, G.; Bader, S. D.

    2000-11-01

    The magnetization reversal processes in an epitaxial Fe/Sm{sub 2}Co{sub 7} structure were investigated using the magneto-optical indicator film technique. The dependence of the magnitude and the orientation of the structure average magnetization have been studied on both cycling and rotating the external magnetic field. It was discovered that the magnetization reversal of the soft ferromagnet can proceed by formation of not only one-dimensional, but also two-dimensional, exchange spin springs. Experimental data is compared with a theoretical estimation of the rotational hysteresis loop for a spin system containing a one-dimensional exchange spring.

  13. Giant magnetic coercivity in YNi{sub 4}B-type SmNi{sub 3}TB (T=Mn–Cu) solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Jinlei; Yan, Chang [Research Center for Solid State Physics and Materials, School of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009 (China); Yapaskurt, V.O. [Department of Petrology, Geological Faculty Moscow State University, Leninskie Gory, Moscow 119992 (Russian Federation); Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation)

    2016-12-01

    The effects of transition metal substitution for Ni on the magnetic properties of the YNi{sub 4}B-type SmNi{sub 4}B via SmNi{sub 3}TB (T=Mn, Fe, Co, Cu) solid solutions have been investigated. SmNi{sub 4}B, SmNi{sub 3}MnB, SmNi{sub 3}FeB, SmNi{sub 3}CoB and SmNi{sub 3}CuB show ferromagnetic ordering at 40 K, 210 K, 322 K, 90 K and 57 K and field sensitive metamagnetic-like transitions at 15 K, 100 K, 185 K, 55 K and 15 K in a magnetic field of 10 kOe, respectively. The magnetocaloric effects of SmNi{sub 3}TB (T=Mn–Cu) were calculated in terms of isothermal magnetic entropy change (ΔS{sub m}). The magnetic entropy ΔS{sub m} reaches value of –0.94 J/kg K at 40 K for SmNi{sub 4}B, –1.5 J/kg K at 205 K for SmNi{sub 3}MnB, –0.54 J/kg K at 320 K for SmNi{sub 3}FeB, –0.49 J/kg K at 90 K for SmNi{sub 3}CoB and –0.54 J/kg K at 60 K for SmNi{sub 3}CuB in field change of 0–50 kOe around the Curie temperature. They show positive ΔS{sub m} of +0.71 J/kg K at ~10 K for SmNi{sub 4}B, +1.69 J/kg K at 30 K for SmNi{sub 3}MnB, +0.89 J/kg K at 110 K for SmNi{sub 3}FeB, +1.08 J/kg K at 25 K for SmNi{sub 3}CoB and +1.12 J/kg K at 10 K for SmNi{sub 3}CuB in field change of 0–50 kOe around the low temperature metamagnetic-like transition. Below the field induced transition temperature (change of magnetic structure), SmNi{sub 3}TB (T=Mn–Cu) exhibits giant magnetic coercivity of 74 kOe at 5 K for SmNi{sub 4}B, 69 kOe at 20 K (90 kOe at 10 K) for SmNi{sub 3}MnB, 77 kOe at 60 K for SmNi{sub 3}FeB, 88 kOe at 20 K for SmNi{sub 3}CoB and 52 kOe at 5 K for SmNi{sub 3}CuB. - Highlights: • YNi{sub 4}B-type SmNi{sub 3}{Mn, Fe, Co, Ni, Cu}B exhibit the Curie points at 39–322 K. • SmNi{sub 3}{Mn, Fe, Co, Ni, Cu}B show field induced transition at 15–185 K. • SmNi{sub 3}MnB shows huge magnetic hysteresis with coercive field of 69 kOe at 20 K. • SmNi{sub 3}FeB shows huge magnetic hysteresis with coercive field of 77 kOe at 60 K. • SmNi{sub 3}CoB shows giant coercive

  14. Synthesis of core-shell hematite (α-Fe2O3) nanoplates: Quantitative analysis of the particle structure and shape, high coercivity and low cytotoxicity

    Science.gov (United States)

    Tadic, Marin; Kopanja, Lazar; Panjan, Matjaz; Kralj, Slavko; Nikodinovic-Runic, Jasmina; Stojanovic, Zoran

    2017-05-01

    Hematite core-shell nanoparticles with plate-like morphology were synthesized using a one-step hydrothermal synthesis. An XRPD analysis indicates that the sample consist of single-phase α-Fe2O3 nanoparticles. SEM and TEM measurements show that the hematite sample is composed of uniform core-shell nanoplates with 10-20 nm thickness, 80-100 nm landscape dimensions (aspect ratio ∼5) and 3-4 nm thickness of the surface shells. We used computational methods for the quantitative analysis of the core-shell particle structure and circularity shape descriptor for the quantitative shape analysis of the nanoparticles from TEM micrographs. The calculated results indicated that a percentage of the shell area in the nanoparticle area (share [%]) is significant. The determined values of circularity in the perpendicular and oblique perspective clearly show shape anisotropy of the nanoplates. The magnetic properties revealed the ferromagnetic-like properties at room temperature with high coercivity HC = 2340 Oe, pointing to the shape and surface effects. These results signify core-shell hematite nanoparticles' for practical applications in magnetic devices. The synthesized hematite plate-like nanoparticles exhibit low cytotoxicity levels on the human lung fibroblasts (MRC5) cell line demonstrating the safe use of these nanoparticles for biomedical applications.

  15. Rethinking Coercive Control.

    Science.gov (United States)

    Stark, Evan

    2009-12-01

    The critical appraisals of Coercive Control focus largely on what my analysis implies for intervention, a matter to which the book devotes only limited space. In this reply, I reiterate core concepts in the book and acknowledge that much more work is needed to translate the realities of coercive control into practical legal and advocacy strategies. I review how coercive control differs from partner assaults and so why it merits a distinct response; the extent to which coercive control targets gender identity; the wisdom of complementing the focus on violence with an emphasis on male domination, sexual inequality and personal liberty; what this implies for shelters and the law; why sexual inequality differentiates coercive control from female partner abuse of men; how sexual equality can be both cause and antidote for coercive control; why I think an affirmative concept of freedom is essential to grasp the human rights violations inflicted by coercive control; and what it means to "story" coercive control by integrating women into the larger liberty narrative on which our national identity rests.

  16. COERCIVE POWER AND CONCESSION MAKING IN BILATERAL NEGOTIATION

    NARCIS (Netherlands)

    De Dreu, C.K.W.

    1995-01-01

    This experiment examined the effects of negotiators' and opponents' coercive capability on level of demand and on communication of threats and promises. Applying conflict spiral and deterrence perspectives inspired contrasting predictions, Subjects were given high, moderate, or low coercive power

  17. Directed magnetic field induced assembly of high magnetic moment cobalt nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, A.K. [Nanyang Technological University, School of Materials Science and Engineering, 639798 (Singapore); Technical University of Denmark, Fuel Cells and Solid State Chemistry Division, Risoe National Laboratory, Roskilde (Denmark); Madhavi, S.; Ramanujan, R.V. [Nanyang Technological University, School of Materials Science and Engineering, 639798 (Singapore)

    2010-03-15

    A directed magnetic field induced assembly technique was employed to align two phase (h.c.p.+f.c.c.) cobalt nanoparticles in a mechanically robust long wire morphology. Co nanoparticles with an average size of 4.3 nm and saturation magnetization comparable to bulk cobalt were synthesized by borohydride reduction followed by size selection and magnetic field induced assembly. The coercivity of these nanowires was higher than their nanoparticle counterpart due to shape anisotropy. The experimental coercivity values of the nanowires were lower than the predictions of the coherent rotation, fanning and curling models of coercivity due to the preponderance of superparamagnetic particles with zero coercivity. (orig.)

  18. Qualitative insight and quantitative analysis of the effect of temperature on the coercivity of a magnetic system

    Directory of Open Access Journals (Sweden)

    Mariia Moskalenko

    2016-02-01

    Full Text Available The temperature dependence of the response of a magnetic system to an applied field can be understood qualitatively by considering variations in the energy surface characterizing the system and estimated quantitatively with rate theory. In the system analysed here, Fe/Sm-Co spring magnet, the width of the hysteresis loop is reduced to a half when temperature is raised from 25 K to 300 K. This narrowing can be explained and reproduced quantitatively without invoking temperature dependence of model parameters as has typically been done in previous data analysis. The applied magnetic field lowers the energy barrier for reorientation of the magnetization but thermal activation brings the system over the barrier. A 2-dimensional representation of the energy surface is developed and used to gain insight into the transition mechanism and to demonstrate how the applied field alters the transition path. Our results show the importance of explicitly including the effect of thermal activation when interpreting experiments involving the manipulation of magnetic systems at finite temperature.

  19. Magnetic domain propagation in Pt/Co/Pt micro wires with engineered coercivity gradients along and across the wire

    Energy Technology Data Exchange (ETDEWEB)

    Jarosz, A., E-mail: arctgh@ifmpan.poznan.pl [Institute of Molecular Physics, Polish Academy of Sciences, ul. M. Smoluchowskiego 17, 60-179 Poznań (Poland); Gaul, A. [Department of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Str. 40, D-34132 Kassel (Germany); Urbaniak, M. [Institute of Molecular Physics, Polish Academy of Sciences, ul. M. Smoluchowskiego 17, 60-179 Poznań (Poland); Ehresmann, A. [Department of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Str. 40, D-34132 Kassel (Germany); Stobiecki, F. [Institute of Molecular Physics, Polish Academy of Sciences, ul. M. Smoluchowskiego 17, 60-179 Poznań (Poland)

    2017-08-01

    Highlights: • Electron lithography and ion bombardment were used to modify the Co/Pt micro-wires. • Two-dimensional perpendicular magnetic anisotropy gradient was engineered. • Engineered anisotropy gradient allowed to control domain wall positions in the wires. • Simulations confirm the influence of defects on a remanent state of the wires. - Abstract: Pt(15 nm)/[Co(0.6 nm)/Pt(1.5 nm)]{sub 4} multilayers with perpendicular magnetic anisotropy were patterned into several-micrometer wide wires by electron-beam lithography. Bombarding the wires with He{sup +} ions with a fluence gradient along the wire results in a spatial gradient of switching fields that allows a controllable positioning of domain walls. The influence of the reduced anisotropy near the wire edges causes a remanent state in which the reversal close to the long edges precedes that in the middle of the wires. Experiments using Kerr microscopy prove this effect and micromagnetic simulations corroborate that a decrease of the anisotropy at the edges is responsible for the effect.

  20. Coercivity and microstructure of Mn-Ni-N sintered alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, S.; Hattori, T.; Tezuka, N. [Department of Materials Science, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai 980-8579 (Japan); Isogai, K.; Matsumoto, H.; Yoshida, S. [NEC TOKIN Corporation, Sendai, Miyagi 982-8510 (Japan)

    2007-12-15

    This paper describes the relationship between magnetic properties and microstructure in Mn-Ni-N sintered alloys. The Mn-Ni-N alloy heat-treated at 1200 C for 3 h and then jacket-quenched in a nitrogen atmosphere, exhibits a high coercivity of 352 kAm{sup -1}. The EDX analysis reveals that the sample jacket-quenched and then annealed in nitrogen, consists of two phases with different Ni content forming a lamellar structure. From TEM observations, the jacket-quenched sample contains many stacking faults and twins with nano-meter size. Therefore, it is considered that they play a role as pinning sites of domain wall motion and high coercivity observed with the quenched sample is caused by the domain wall pinning mechanism. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Highly magnetic Co nanoparticles fabricated by X-ray radiolysis

    Science.gov (United States)

    Clifford, Dustin M.; Castano, Carlos E.; Rojas, Jessika V.

    2018-03-01

    Advanced routes for the synthesis of nanomaterials, such as ferromagnetic nanoparticles, are being explored that are easy to perform using cost-effective and non-toxic precursors. Radiolytic syntheses based on the use of X-rays as ionizing radiation are promising towards this effort. X-rays were used to produce highly magnetic cobalt nanoparticles (NPs), stable in air up to 200 °C, from the radiolysis of water. Crystal structure analysis by XRD indicates a mixture of Cofcc, 63%, and Cohcp, 37%, phases. Magnetic analysis by VSM gave a saturation magnetization (Ms) 136 emu/g at 1 T and coercivity (Hc) = 325 Oe when the reaction solution was purged with N2 while an air-purged treatment resulted in Co NPs having 102 emu/g with a coercivity (Hc) 270 Oe. Overall, the reduction of Co2+ occurred in an aqueous reaction environment without addition of chemical reductants resulting in Co NPs with size distribution from 20 to 140 nm. This clean approach at ambient temperature produced highly magnetic Co NPs that may be used for switching devices (i.e. reed switches) or as additives for alloys that require high Curie points.

  2. Tuning coercive force by adjusting electric potential in solution processed Co/Pt(111) and the mechanism involved

    Science.gov (United States)

    Chang, Cheng-Hsun-Tony; Kuo, Wei-Hsu; Chang, Yu-Chieh; Tsay, Jyh-Shen; Yau, Shueh-Lin

    2017-03-01

    A combination of a solution process and the control of the electric potential for magnetism represents a new approach to operating spintronic devices with a highly controlled efficiency and lower power consumption with reduced production cost. As a paradigmatic example, we investigated Co/Pt(111) in the Bloch-wall regime. The depression in coercive force was detected by applying a negative electric potential in an electrolytic solution. The reversible control of coercive force by varying the electric potential within few hundred millivolts is demonstrated. By changing the electric potential in ferromagnetic layers with smaller thicknesses, the efficiency for controlling the tunable coercive force becomes higher. Assuming that the pinning domains are independent of the applied electric potential, an electric potential tuning-magnetic anisotropy energy model was derived and provided insights into our knowledge of the relation between the electric potential tuning coercive force and the thickness of the ferromagnetic layer. Based on the fact that the coercive force can be tuned by changing the electric potential using a solution process, we developed a novel concept of electric-potential-tuned magnetic recording, resulting in a stable recording media with a high degree of writing ability.

  3. Tuning coercive force by adjusting electric potential in solution processed Co/Pt(111) and the mechanism involved.

    Science.gov (United States)

    Chang, Cheng-Hsun-Tony; Kuo, Wei-Hsu; Chang, Yu-Chieh; Tsay, Jyh-Shen; Yau, Shueh-Lin

    2017-03-03

    A combination of a solution process and the control of the electric potential for magnetism represents a new approach to operating spintronic devices with a highly controlled efficiency and lower power consumption with reduced production cost. As a paradigmatic example, we investigated Co/Pt(111) in the Bloch-wall regime. The depression in coercive force was detected by applying a negative electric potential in an electrolytic solution. The reversible control of coercive force by varying the electric potential within few hundred millivolts is demonstrated. By changing the electric potential in ferromagnetic layers with smaller thicknesses, the efficiency for controlling the tunable coercive force becomes higher. Assuming that the pinning domains are independent of the applied electric potential, an electric potential tuning-magnetic anisotropy energy model was derived and provided insights into our knowledge of the relation between the electric potential tuning coercive force and the thickness of the ferromagnetic layer. Based on the fact that the coercive force can be tuned by changing the electric potential using a solution process, we developed a novel concept of electric-potential-tuned magnetic recording, resulting in a stable recording media with a high degree of writing ability.

  4. Electric-field assisted switching of magnetization in perpendicularly magnetized (Ga,Mn)As films at high temperatures

    Science.gov (United States)

    Wang, Hailong; Ma, Jialin; Yu, Xueze; Yu, Zhifeng; Zhao, Jianhua

    2017-01-01

    The electric-field effects on the magnetism in perpendicularly magnetized (Ga,Mn)As films at high temperatures have been investigated. An electric-field as high as 0.6 V nm-1 is applied by utilizing a solid-state dielectric Al2O3 film as a gate insulator. The coercive field, saturation magnetization and magnetic anisotropy have been clearly changed by the gate electric-field, which are detected via the anomalous Hall effect. In terms of the Curie temperature, a variation of about 3 K is observed as determined by the temperature derivative of the sheet resistance. In addition, electrical switching of the magnetization assisted by a fixed external magnetic field at 120 K is demonstrated, employing the gate-controlled coercive field. The above experimental results have been attributed to the gate voltage modulation of the hole density in (Ga,Mn)As films, since the ferromagnetism in (Ga,Mn)As is carrier-mediated. The limited modulation magnitude of magnetism is found to result from the strong charge screening effect introduced by the high hole concentration up to 1.10  ×  1021 cm-3, while the variation of the hole density is only about 1.16  ×  1020 cm-3.

  5. Makeup and uses of a basic magnet laboratory for characterizing high-temperature permanent magnets

    Science.gov (United States)

    Niedra, Janis M.; Schwarze, Gene E.

    1991-01-01

    A set of instrumentation for making basic magnetic measurements was assembled in order to characterize high intrinsic coercivity, rare earth permanent magnets with respect to short term demagnetization resistance and long term aging at temperatures up to 300 C. The major specialized components of this set consist of a 13 T peak field, capacitor discharge pulse magnetizer; a 10 in. pole size, variable gap electromagnet; a temperature controlled oven equipped with iron cobalt pole piece extensions and a removable paddle that carries the magnetization and field sensing coils; associated electronic integrators; and sensor standards for field intensity H and magnetic moment M calibration. A 1 cm cubic magnet sample, carried by the paddle, fits snugly between the pole piece extensions within the electrically heated aluminum oven, where fields up to 3.2 T can be applied by the electromagnet at temperatures up to 300 C. A sample set of demagnetization data for the high energy Sm2Co17 type of magnet is given for temperatures up to 300 C. These data are reduced to the temperature dependence of the M-H knee field and of the field for a given magnetic induction swing, and they are interpreted to show the limits of safe operation.

  6. Annealing induced low coercivity, nanocrystalline Co–Fe–Si thin films exhibiting inverse cosine angular variation

    Energy Technology Data Exchange (ETDEWEB)

    Hysen, T., E-mail: hysenthomas@gmail.com [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India); Al-Harthi, Salim; Al-Omari, I.A. [Department of Physics, Sultan Qaboos University, PC 123, Muscat, Sultanate of Oman (Oman); Geetha, P.; Lisha, R. [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India); Ramanujan, R.V. [School of Materials Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Sakthikumar, D. [Graduate School of Interdisciplinary New Science, Toyo University, Kawagoe, Saitama (Japan); Anantharaman, M.R., E-mail: mra@cusat.ac.in [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India)

    2013-09-15

    Co–Fe–Si based films exhibit high magnetic moments and are highly sought after for applications like soft under layers in perpendicular recording media to magneto-electro-mechanical sensor applications. In this work the effect of annealing on structural, morphological and magnetic properties of Co–Fe–Si thin films was investigated. Compositional analysis using X-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a native oxide surface layer consisting of oxides of Co, Fe and Si on the surface. The morphology of the as deposited films shows mound like structures conforming to the Volmer–Weber growth model. Nanocrystallisation of amorphous films upon annealing was observed by glancing angle X-ray diffraction and transmission electron microscopy. The evolution of magnetic properties with annealing is explained using the Herzer model. Vibrating sample magnetometry measurements carried out at various angles from 0° to 90° to the applied magnetic field were employed to study the angular variation of coercivity. The angular variation fits the modified Kondorsky model. Interestingly, the coercivity evolution with annealing deduced from magneto-optical Kerr effect studies indicates a reverse trend compared to magetisation observed in the bulk. This can be attributed to a domain wall pinning at native oxide layer on the surface of thin films. The evolution of surface magnetic properties is correlated with morphology evolution probed using atomic force microscopy. The morphology as well as the presence of the native oxide layer dictates the surface magnetic properties and this is corroborated by the apparent difference in the bulk and surface magnetic properties. - Highlights: • The relation between grain size and magnetic properties in Co–Fe–Si thin films obeys the Herzer model. • Angular variation of coercivity is found to obey the Kondorsky model. • The MOKE measurements provide further evidence for domain wall pinning.

  7. Discriminating Coercive from Sadomasochistic Sexuality.

    Science.gov (United States)

    Martin, Shannon M; Smith, Felix; Quirk, Stuart W

    2016-07-01

    Sadomasochistic (SM) sexual interest is reported by a wide range of individuals. Within the sex offender literature, the presence of SM interest is often viewed as a herald of criminal sexual behavior; however, research indicates that SM interests are not predictive of coercive sexual behavior. In the current study, we measured a range of sexual fantasies and behaviors, and then applied cluster analyses to determine (1) if individuals endorsed elevated SM interests also endorsed coercive fantasies and, (2) to explore cluster membership correlates using measures of sensation seeking, externalizing and antisocial behaviors, attitudes toward rape, and empathic capacity. A total of 550 participants were recruited through a variety of on-line discussion areas. A four cluster solution best fit the data with distinct clusters observed for those endorsing SM behaviors and those reporting coercive sexual behavior. Additional analyses revealed greater endorsement of victim blaming attitudes and lower empathic concern among members of the coercive sexual behavior cluster. Elevated sensation seeking and externalizing behaviors were reported by members of clusters marked by SM and coercive sexual behavior. Results provide further support for the differentiation between SM and coercive sexual behaviors as representative of individuals with divergent attitudes, traits, and behaviors.

  8. Coercive power and concession making in bilateral negotiation

    NARCIS (Netherlands)

    de Dreu, C.K.W.

    1995-01-01

    Examined the effects of negotiators' and opponents' coercive capability on level of demand and on communication of threats and promises in an experiment involving 170 undergraduates. Applying conflict spiral and deterrence perspectives inspired contrasting predictions. Ss were given high, moderate,

  9. Anisotropic bulk SmCo7 nanocrystalline magnets with high energy product

    Directory of Open Access Journals (Sweden)

    Wenpeng Song

    2017-11-01

    Full Text Available Realizing grain alignment along easy magnetization axis in bulk SmCo7 nanocrystalline materials is crucial for their development as high-performance high-temperature magnets, yet it remains challenging. Here, we report the fabrication of anisotropic bulk SmCo7 nanocrystalline magnets with a small grain size of ∼20 nm and a (00l texture using high-pressure thermal compression starting from partially amorphous precursors. The synthesized magnet exhibits a high energy product of 18.4 MGOe, 40% larger than the reported highest value (13 MGOe for bulk nanostructured SmCo7 magnets, and outperforms its anisotropic coarse-grained counterpart. Moreover, our magnet shows a low coercivity temperature coefficient of β = −0.19%/°C. These findings make an important step toward the fabrication of oriented bulk nanostructures for practical applications.

  10. High temperature superconductor accelerator magnets

    OpenAIRE

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet is ...

  11. High Temperature Superconductor Accelerator Magnets

    OpenAIRE

    Van Nugteren, Jeroen; ten Kate, Herman; de Rijk, Gijs; Dhalle, Marc

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding $20T$. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet ...

  12. Organic-and molecule-based magnets

    Indian Academy of Sciences (India)

    The discovery of organic- and molecule-based magnets has led to design and synthesis of several families with magnetic ordering temperatures as high as ∼ 125° C. Examples of soft and hard magnets with coercivities as high as 27 kOe have also been reported. Examples from our laboratory of organic-based magnets ...

  13. High performance soft magnetic materials

    CERN Document Server

    2017-01-01

    This book provides comprehensive coverage of the current state-of-the-art in soft magnetic materials and related applications, with particular focus on amorphous and nanocrystalline magnetic wires and ribbons and sensor applications. Expert chapters cover preparation, processing, tuning of magnetic properties, modeling, and applications. Cost-effective soft magnetic materials are required in a range of industrial sectors, such as magnetic sensors and actuators, microelectronics, cell phones, security, automobiles, medicine, health monitoring, aerospace, informatics, and electrical engineering. This book presents both fundamentals and applications to enable academic and industry researchers to pursue further developments of these key materials. This highly interdisciplinary volume represents essential reading for researchers in materials science, magnetism, electrodynamics, and modeling who are interested in working with soft magnets. Covers magnetic microwires, sensor applications, amorphous and nanocrystalli...

  14. Magnetization Process of High Anisotropy CoPt Nanosized Dots

    NARCIS (Netherlands)

    Kikuchi, Nobuaki; Murillo Vallejo, R.; Lodder, J.C.; Mitsuzuka, K.; Shimatsu, T.; Shimatsu, T.

    2005-01-01

    Dot arrays with diameter ranging from 80 to 245 nm are made of Co80Pt20 films with large perpendicular anisotropy. Magnetic properties are investigated by detecting the anomalous Hall effect. The all arrays show angular dependence of remanent coercivity similar to coherent rotation. The result shows

  15. Magnetic recording with acoustic waves

    Energy Technology Data Exchange (ETDEWEB)

    Li, Weiyang; Buford, Benjamin; Jander, Albrecht; Dhagat, Pallavi, E-mail: dhagat@eecs.oregonstate.edu

    2014-09-01

    We demonstrate acoustically assisted magnetic recording (AAMR), a new paradigm in magnetic data storage. In this concept, otherwise unwriteable high-coercivity media, requisite for thermally stable high-density data storage, are made amenable to recording by lowering their coercivity via strain induced by surface acoustic waves. The basic principles of AAMR are proven using galfenol, a low-coercivity magnetostrictive material, as the recording medium. It is shown that the writing field needed to record data in the presence of acoustic strain is lower than the coercivity of the unstrained galfenol film. Further, it is demonstrated that interference between acoustic waves can be tailored to selectively address a bit on the recording medium.

  16. High Magnetic Fields in Chemistry

    Science.gov (United States)

    Steiner, U. E.; Gilch, P.

    Recent applications of large ( 1 T - 30 T) magnetic fields in modern chemical research are reviewed. Magnetic field effects of chemical relevance appear on the levels of quantum mechanics, thermodynamics, and oscopic forces. Quantum mechanical magnetic field effects are governed by the Zeeman interaction and are borne out as static and dynamic effects in spectroscopy and in chemical kinetics. Magnetic circular dichroism (MCD) spectroscopy and magnetic fluorescence quenching in the gas phase serve to illustrate the former, while radical pair spin chemistry is representative of the latter. The principles of the radical pair mechanism are outlined and high-field applications are illustrated in some detail for photo-induced electron transfer reactions of some transition metal complexes. Thermodynamic effects concern the magnetization of chemical samples, which is the focus of magnetochemistry or — more modern — molecular magnetism, and the equilibrium of chemical reactions. Representative examples of both aspects are described. Finally, the exploitation of orientational forces caused by the magnetic anisotropy of larger particles (from omolecules to micro-crystals) is exemplified. Crystal growth in a magnetic field may hold a potential for achieving better control of the quality of protein crystals for structural analysis.

  17. High temperature superconductor accelerator magnets

    NARCIS (Netherlands)

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and

  18. Variable substrate temperature deposition of CoFeB film on Ta for manipulating the perpendicular coercive forces

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmanan, Saravanan; Rao, Subha Krishna [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India); Muthuvel, Manivel Raja [Defence Metallurgical Research Laboratory (DMRL), Hyderabad 500058 (India); Chandrasekaran, Gopalakrishnan [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India); Therese, Helen Annal, E-mail: helen.a@ktr.srmuniv.ac.in [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India)

    2017-08-01

    Highlights: • Ta/CoFeB(50 nm)/Ta thin films were deposited at various substrate temperatures (T{sub s}). • CoFeB films deposited at T{sub s} such as RT, 450 °C, 475 °C and 500 °C exhibited perpendicular coercivity. • CoFeB deposited at 475 °C displayed a higher coercivity of 315 Oe and a low M{sub s} of 169 emu/cc. • The enhanced crystallization of CoFeB at the Ta/CoFeB interface results in higher H{sub c} (⟂). - Abstract: Magnetization of Ta/CoFeB/Ta trilayer films with thick layer of CoFeB deposited under different substrate temperatures (T{sub s}) via ultra-high vacuum DC sputtering technique has been measured with the applied magnetic field parallel and perpendicular to the plane of the film respectively to study the perpendicular coercive forces of the film. The samples were further analyzed for its structural, topological, morphological, and electrical transport properties. The core chemical states for the elements present in the CoFeB thin film were analyzed by XPS studies. Magnetization studies reveal the existence of perpendicular coercive forces in CoFeB films deposited only at certain temperatures such as RT, 450 °C, 475 °C and 500 °C. CoFeB film deposited at 475 °C exhibited a maximum coercivity of 315 Oe and a very low saturation magnetization (M{sub s}) of 169 emu/cc in perpendicular direction. This pronounced effect in perpendicular coercive forces observed for CoFeB475 could be attributed to the effect of temperature in enhancing the crystallization of the film at the Ta/CoFeB interfaces. However at temperatures higher than 475 °C the destruction of the Ta/CoFeB interface due to intermixing of Ta and CoFeB results in the disappearance of magnetic anisotropy.

  19. Microstructure and magnetic properties of nano-sized Ba-Al ferrite particles by high energy ball milling.

    Science.gov (United States)

    Kim, Bo Sik; Chang, Si Young

    2012-02-01

    The magnetic nano-structured Ba-Al ferrite powders were prepared by high energy ball milling under the conditions of various rotation rates and milling times. The micro structure was characterized by SEM, XRD and TEM, and the magnetic properties were obtained by VSM. As the rotation rate and milling time increased, the size of nano-sized particles gradually decreased. The high energy ball milling for 5 h without relation to the rotation rate drastically reduced the coercivity as a consequence of the formation of nano-sized particle with the amorphous structure. However, the coercivity gradually decreased with increasing the milling time, resulting from the decrease of particle size with maintaining the crystal structure.

  20. Is a diagnostic category for paraphilic coercive disorder defensible?

    Science.gov (United States)

    Knight, Raymond A

    2010-04-01

    There is a proposal to establish a paraphilic coercive disorder as a new paraphilia in the DSM-V. The empirical data do not, however, support the hypothesis that a distinct syndrome exists that comprises males who are sexually aroused by the coercive elements of rape per se. Purported evidence for this syndrome has centered on the results of phallometric studies. Higher plethysmographic responses of rapists to coercive rape scenarios may, however, be better explained by the failure of coercive elements to inhibit arousal to sexual aspects of the stimuli rather than by arousal specifically to the coercive elements. In addition, sexual fantasies about forcing sex and about struggling victims are highly correlated with sadistic fantasies and have not been shown to identify a syndrome that can be discriminated from sadism. Finally, taxometric evidence strongly supports the hypothesis that the underlying components of rape are distributed as dimensions and do not constitute a separate taxon. Consequently, the criteria purported to categorize rapists into the proposed syndrome would have to be arbitrarily determined. Not only does there seem to be little empirical justification for the creation of this new syndrome, the inclusion of this disorder among the paraphilias would have serious potential for misuse. It would imply endorsement of Paraphilia, NOS, nonconsent, which is currently inappropriately employed in civil commitment proceedings to justify commitment.

  1. The modified procedures in coercivity scaling*

    Directory of Open Access Journals (Sweden)

    Najgebauer Mariusz

    2015-09-01

    Full Text Available The paper presents a scaling approach to the analysis of coercivity. The Widom-based procedure of coercivity scaling has been tested for non-oriented electrical steel. Due to insufficient results, the scaling procedure was improved relating to the method proposed by Van den Bossche. The modified procedure of coercivity scaling gave better results, in comparison to the original approach. The influence of particular parameters and a range of measurement data used in the estimations on the final effect of the coercivity scaling were discussed.

  2. Self propagating high temperature synthesis of metal oxides. Reactions in external magnetic fields

    CERN Document Server

    Aguas, M D

    2001-01-01

    The preparation of metal oxides by Self-Propagating High-Temperature Synthesis is reported. The reactions are started with a point source of ignition; typically a hot wire. A synthesis wave is observed moving out from the point source and reactions terminate in seconds. Products obtained can be classified into ferrites (magnetic applications) and stannates (gas sensing applications). Ferrites were synthesised under variable external magnetic fields. The synthesis wave is hotter in the presence of an external magnetic field for hard ferrite synthesis. For spinel ferrites the opposite was observed. Materials synthesised in the field show differences in their bulk magnetic properties (coercivity and saturation magnetisation), structures and microstructures. Combustion reactions in large fields revealed changes in unit cell volume (shrinkage was observed for hard ferrites while expansion was observed for spinel ferrites). SHS synthesised hard ferrites show two distinct components; one has large grain structure co...

  3. High Temperature Superconductor Accelerator Magnets

    CERN Document Server

    AUTHOR|(CDS)2079328; de Rijk, Gijs; Dhalle, Marc

    2016-11-10

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding $20T$. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet is based on ReBCO coated conductor, which is assembled into a $10kA$ class Roebel cable. A new and optimized Aligned Block layout is used, which takes advantage of the anisotropy of the conductor. This is achieved by providing local alignment of the Roebel cable in the coil windings with the magnetic field lines. A new Network Model capable of analyzing transient electro-magnetic and thermal phenomena in coated conductor cables and coils is developed. This model is necessary to solve critical issues in coated conductor ac...

  4. Effect of Co content on structure and magnetic behaviors of high induction Fe-based amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Rajat K., E-mail: rajat@nmlindia.org; Panda, Ashis K.; Mitra, Amitava

    2016-11-15

    The replacement of Fe with Co is investigated in the (Fe{sub 1−x}Co{sub x}){sub 79}Si{sub 8.5}B{sub 8.5}Nb{sub 3}Cu{sub 1} (x=0, 0.05, 0.2, 0.35, 0.5) amorphous alloys. The alloys are synthesized in the forms of ribbons by single roller melt spinning technique, and the structural and magnetic properties of annealed ribbons are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), B–H curve tracer, respectively. All as-cast alloys are structurally amorphous, however, their magnetic properties are varying with Co addition. The Co addition within 5–20 at% results in moderate thermal stability, saturation induction, Curie temperature and lowest coercivity, while 35 at% Co causes highest saturation induction, coercivity, Curie temperature and lowest thermal stability. On devitrification, the magnetic properties change with the generation of α-FeCo nanocrystallites and (FeCo){sub 23}B{sub 6}, Fe{sub 2}B phases during primary and secondary crystallization stages, respectively. A small amount Co is advantageous for maintaining finer nanocrystallites in amorphous matrix even after annealing at 600 °C, leading to high saturation magnetization (>1.5 T) and low coercivity (~35 A/m). The improved magnetic properties at elevated temperatures indicate these alloys have a potential for high frequency transformer core applications. - Highlights: • The structural and magnetic behaviors of Fe based amorphous alloys have been investigated with the effect of Co content. • The Co has no adverse effect on amorphization of alloys. • A small amount Co causes the superior improvement of magnetic properties at elevated temperatures. • Therefore, it is important not only for academic research but also for industrial applied research.

  5. Self propagating high temperature synthesis of ferrites in magnetic fields

    CERN Document Server

    Affleck, L

    2002-01-01

    Self propagating high temperature synthesis (SHS) reactions have been performed on mixtures of BaO sub 2 , Fe and Fe sub 2 O sub 3 to form barium ferrite, BaFe sub 1 sub 2 O sub 1 sub 9. Reactions were conducted in zero field and in an applied magnetic field of 1.1 T with the aim of exploring the influence of the field. The temperature and velocity of the reactions were measured and the products, both post-SHS and post-annealing, were characterised by techniques including X-ray diffraction, Moessbauer spectroscopy, vibrating sample magnetometry and electron microprobe analysis. The applied magnetic field was found to lead to hotter and faster reactions, a greater degree of conversion of the reactants, a needle-like microstructure in the post-SHS product, and a reduced coercive field (approx 20-30 %) in the annealed product, compared to zero field. Sodium perchlorate was used as an internal oxidising agent, and found to produce similar effects. Correlations were observed between the temperature reached in the ...

  6. Synthesis of high saturation magnetic iron oxide nanomaterials via low temperature hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Bhavani, P.; Rajababu, C.H. [Department of Materials Science & Nanotechnology, Yogivemana University, Vemanapuram 516003, Kadapa (India); Arif, M.D. [Environmental Magnetism Laboratory, Indian Institute of Geomagnetism (IIG), Navi Mumbai 410218, Mumbai (India); Reddy, I. Venkata Subba [Department of Physics, Gitam University, Hyderabad Campus, Rudraram, Medak 502329 (India); Reddy, N. Ramamanohar, E-mail: manoharphd@gmail.com [Department of Materials Science & Nanotechnology, Yogivemana University, Vemanapuram 516003, Kadapa (India)

    2017-03-15

    Iron oxide nanoparticles (IONPs) were synthesized through a simple low temperature hydrothermal approach to obtain with high saturation magnetization properties. Two series of iron precursors (sulfates and chlorides) were used in synthesis process by varying the reaction temperature at a constant pH. The X-ray diffraction pattern indicates the inverse spinel structure of the synthesized IONPs. The Field emission scanning electron microscopy and high resolution transmission electron microscopy studies revealed that the particles prepared using iron sulfate were consisting a mixer of spherical (16–40 nm) and rod (diameter ~20–25 nm, length <100 nm) morphologies that synthesized at 130 °C, while the IONPs synthesized by iron chlorides are found to be well distributed spherical shapes with size range 5–20 nm. On other hand, the IONPs synthesized at reaction temperature of 190 °C has spherical (16–46 nm) morphology in both series. The band gap values of IONPs were calculated from the obtained optical absorption spectra of the samples. The IONPs synthesized using iron sulfate at temperature of 130 °C exhibited high saturation magnetization (M{sub S}) of 103.017 emu/g and low remanant magnetization (M{sub r}) of 0.22 emu/g with coercivity (H{sub c}) of 70.9 Oe{sub ,} which may be attributed to the smaller magnetic domains (d{sub m}) and dead magnetic layer thickness (t). - Highlights: • Comparison of iron oxide materials prepared with Fe{sup +2}/Fe{sup +3} sulfates and chlorides at different temperatures. • We prepared super-paramagnetic and soft ferromagnetic magnetite nanoparticles. • We report higher saturation magnetization with lower coercivity.

  7. Size Induced Structural and Magnetic Properties of Nanostructured ...

    African Journals Online (AJOL)

    Cobalt ferrite (CoFe2O4), a well-known hard magnetic material high frequency applications and high-density recording media. Due to their good chemical and thermal stability, high permeability, high electrical resistivity, high saturation magnetization and coercivity etc. they found wide technological applications.

  8. Coercivity enhancement in boron-enriched stoichiometric REFeB melt-spun alloys

    Energy Technology Data Exchange (ETDEWEB)

    Betancourt, I. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, 04510 Mexico, D.F. (Mexico)], E-mail: israelb@correo.unam.mx; Cruz-Arcos, G. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, 04510 Mexico, D.F. (Mexico); Schrefl, T.; Davies, H.A. [Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2008-10-15

    Considerable enhancement of magnetic properties was attained in initially stoichiometric nanophase RE{sub 12}Fe{sub 82}B{sub 6} melt-spun alloys (RE = Nd, Nd + Pr) by means of an excess B content (10 at%) and additions of Zr and Co (2% and 7%, respectively). The intrinsic coercivity exhibited a marked improvement (with respect to the stoichiometric 6 at% B alloy), within the range 50-65%, with a maximum of 1161 {+-} 14 kA m{sup -1} for the B-rich and Zr-containing alloy, together with an excellent combination of remanence and energy density values of 0.90 {+-} 0.01 T and 137 {+-} 4 kJ m{sup -3}, respectively. Further Co addition led to a Curie temperature increase, while preserving high coercivity (1176 {+-} 31 kA m{sup -1}) and useful energy densities (119 {+-} 4 kJ m{sup -3}). Results were interpreted on the basis of alloy microstructural features and on variations of the intrinsic magnetic properties, supported by micromagnetic calculations.

  9. Microstructure and magnetic properties of mechanically alloyed FeSiBAlNi (Nb) high entropy alloys

    Science.gov (United States)

    Wang, Jian; Zheng, Zhou; Xu, Jing; Wang, Yan

    2014-04-01

    In this paper, the effects of milling duration and composition on the microstructure and magnetic properties of equi-atomic FeSiBAlNi and FeSiBAlNiNb high entropy alloys during mechanical alloying have been investigated using X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy and alternating gradient magnetometry. The amorphous high entropy alloys have been successfully fabricated using the mechanical alloying method. The results show that the Nb addition prolongs the milling time for the formation of the fully FeSiBAlNi amorphous phase and decreases the glass forming ability. However, FeSiBAlNiNb amorphous high entropy alloy has the higher thermal stability and heat resisting properties. Moreover, the as-milled FeSiBAlNi(Nb) powders are soft-magnetic materials indicated by their low coercivity. The saturation magnetization of the as-milled FeSiBAlNi(Nb) powders decreases with prolonging of the milling time and shows the lowest value when the amorphous high entropy alloys are formed. It suggests that the as-milled products with solid solution phases show the better soft-magnetic properties than those with fully amorphous phases. The Nb addition does not improve the soft-magnetic properties of the FeSiBAlNi high entropy alloys. Rather, both amorphous high entropy alloys have similar soft-magnetic properties after a long milling time.

  10. Effect of high magnetic field on magnetic properties of oxidized ZnO:Co film prepared with different growth models

    Directory of Open Access Journals (Sweden)

    Shiying Liu

    2017-11-01

    Full Text Available Growth models and high magnetic field (HMF are employed to affect diluted magnetic performance of Co-doped ZnO (ZnO:Co films which oxidize Co-Zn evaporated films at 300 °C for 120 min in open air. Nanograined boundaries and dense structure obtained in the co-deposition films are helpful to present a better diluted magnetic performance. Two phases of Zn and ZnO coexist in the films at a low oxidation temperature. Both the bilayer Co/Zn film and the application of HMF during the oxidation process offer an easy way to increase oxygen vacancies, which are inconducive to improve the ferromagnetism. The co-deposition 0 T film has the best diluted magnetic performance compared with the bilayer 0 T film. To be specific, saturation magnetization MS of the co-deposition 0 T film (100.1 emu/cm3 increases by 190%, squareness S increases from 0.31 to 0.75 and coercivity HC increases from 34.6 Oe to 183.5 Oe. With the application of HMF, the MS of the co-deposition films decreases by 44% to approximately 55.8 emu/cm3 and the HC increases to 118.4 Oe.

  11. Coercive Tactics and Web Advertising Performance

    National Research Council Canada - National Science Library

    Jiwon Lee; Inwon Kang; Joseph Stanfield

    2017-01-01

    By questioning contemporary coercive or intrusive web advertising activities, this study sheds light on the recent conditions of web advertising by focusing on a comprehensive process that leads to web ad performance...

  12. High-frequency magnetic components

    CERN Document Server

    Kazimierczuk, Marian K

    2013-01-01

    A unique text on the theory and design fundaments of inductors and transformers, updated with more coverage on the optimization of magnetic devices and many new design examples The first edition is popular among a very broad audience of readers in different areas of engineering and science. This book covers the theory and design techniques of the major types of high-frequency power inductors and transformers for a variety of applications, including switching-mode power supplies (SMPS) and resonant dc-to-ac power inverters and dc-to-dc power converters. It describes eddy-current phenomena (su

  13. Studies on dielectric, optical, magnetic, magnetic domain structure, and resistance switching characteristics of highly c-axis oriented NZFO thin films

    Science.gov (United States)

    Pradhan, Dhiren K.; Kumari, Shalini; Li, Linglong; Vasudevan, Rama K.; Das, Proloy T.; Puli, Venkata S.; Pradhan, Dillip K.; Kumar, Ashok; Misra, Pankaj; Pradhan, A. K.; Kalinin, Sergei V.; Katiyar, Ram S.

    2017-07-01

    With the rapid development of new device miniaturization technology, there is invigorated interest in magnetic nanostructures for potential application in novel multifunctional devices. In continuation to our search for a suitable magnetic material having Curie temperature (Tc) well above room temperature for multifunctional applications, we have studied the dielectric, optical, magnetic, and resistance switching characteristics of Ni0.65Zn0.35Fe2O4 (NZFO) thin films. The observation of only (004) reflection in the X-ray diffraction patterns confirms the c-axis orientation and high quality growth of NZFO thin films. The presence of mixed valences of Fe2+/Fe3+ cations is probed by X-ray photon spectroscopy, which supports the cationic ordering-mediated large dielectric response. Our investigations reveal NZFO to be an indirect band gap material (˜1.8 eV) with a direct gap at ˜2.55 eV. These nanostructures exhibit high saturation magnetization and a low coercive field with a ferrimagnetic-paramagnetic phase transition of ˜713 K. Magnetic force microscopy studies revealed the stripe-like domain structure of the investigated thin films. In addition, these thin films exhibit reliable and repeatable unipolar resistive switching characteristics. The observed high dielectric permittivity with low loss tangent, large magnetization with soft magnetic behavior, striped magnetic domain structure and reliable resistance switching in NZFO thin films above room temperature suggest potential application in memory, spintronics, and multifunctional devices.

  14. Fabrication of highly dense isotropic Nd-Fe-B bonded magnets via extrusion-based additive manufacturing

    OpenAIRE

    Li, Ling; Jones, Kodey; Sales, Brian; Pries, Jason L.; I. C. Nlebedim; Jin, Ke; Bei, Hongbin; Post, Brian; Kesler, Michael; Rios, Orlando; Kunc, Vlastimil; Fredette, Robert; Ormerod, John; Williams, Aaron; Lograsso, Thomas A.

    2017-01-01

    Isotropic bonded magnets with a high loading fraction of 70 vol.% Nd-Fe-B are fabricated via an extrusion-based additive manufacturing, or 3D printing system that enables rapid production of large parts for the first time. The density of the printed magnet is 5.15 g/cm3. The room temperature magnetic properties are: intrinsic coercivity Hci = 8.9 kOe (708.2 kA/m), remanence Br = 5.8 kG (0.58 Tesla), and energy product (BH)max = 7.3 MGOe (58.1 kJ/m3). The as-printed magnets are then coated wit...

  15. Processing of MnBi bulk magnets with enhanced energy product

    Directory of Open Access Journals (Sweden)

    Narayan Poudyal

    2016-05-01

    Full Text Available We report magnetic properties and microstructure of high energy-product MnBi bulk magnets fabricated by low-temperature ball-milling and warm compaction technique. A maximum energy product (BHmax of 8.4 MGOe and a coercivity of 6.2 kOe were obtained in the bulk MnBi magnet at room temperature. Magnetic characterization at elevated temperatures showed an increase in coercivity to 16.2 kOe while (BHmax value decreased to 6.8 MGOe at 400 K. Microstructure characterization revealed that the bulk magnets consist of oriented uniform nanoscale grains with average size about 50 nm.

  16. Analysis of thermal demagnetization behavior of Nd–Fe–B sintered magnets using magnetic domain observation

    Directory of Open Access Journals (Sweden)

    Masaaki Takezawa

    2016-05-01

    Full Text Available We used magnetic domain observation to statistically observe the thermal demagnetization behavior of Nd–Fe–B sintered magnets at elevated temperatures up to 150 °C. Simultaneous magnetization reversal in a hundred adjacent grains occurred at 90 °C because of the magnetic interaction among the grains beyond grain boundaries in the Dysprosium (Dy-free low-coercivity magnet. Conversely, simultaneous magnetization reversal in a hundred grains did not occur in the Dy-added high-coercivity magnets, and the demagnetizing ratio steadily increased with temperature. Furthermore, the addition of Dy induced high thermal stability by eliminating the simultaneous thermal demagnetization, which was caused by the magnetic interaction among the grains.

  17. Variation in use of coercive measures in psychiatric hospitals.

    Science.gov (United States)

    Lay, B; Nordt, C; Rössler, W

    2011-05-01

    The use of coercive measures in psychiatry is still poorly understood. Most empirical research has been limited to compulsory admission and to risk factors on an individual patient level. This study addresses three coercive measures and the role of predictive factors at both patient and institutional levels. Using the central psychiatric register that covers all psychiatric hospitals in Canton Zurich (1.3 million people), Switzerland, we traced all inpatients in 2007 aged 18-70 (n = 9698). We used GEE models to analyse variation in rates between psychiatric hospitals. Overall, we found quotas of 24.8% involuntary admissions, 6.4% seclusion/restraint and 4.2% coerced medication. Results suggest that the kind and severity of mental illness are the most important risk factors for being subjected to any form of coercion. Variation across the six psychiatric hospitals was high, even after accounting for risk factors on the patient level suggesting that centre effects are an important source of variability. However, effects of the hospital characteristics 'size of the hospital', 'length of inpatient stay', and 'work load of the nursing staff' were only weak ('bed occupancy rate' was not statistically significant). The significant variation in use of coercive measures across psychiatric hospitals needs further study. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

  18. High Temperature Magnetic Properties of Indirect Exchange Spring FePt/M(Cu,C/Fe Trilayer Thin Films

    Directory of Open Access Journals (Sweden)

    Anabil Gayen

    2013-01-01

    Full Text Available We report the investigation of temperature dependent magnetic properties of FePt and FePt(30/M(Cu,C/Fe(5 trilayer thin films prepared by using magnetron sputtering technique at ambient temperature and postannealed at different temperatures. L10 ordering, hard magnetic properties, and thermal stability of FePt films are improved with increasing postannealing temperature. In FePt/M/Fe trilayer, the formation of interlayer exchange coupling between magnetic layers depends on interlayer materials and interface morphology. In FePt/C/Fe trilayer, when the C interlayer thickness was about 0.5 nm, a strong interlayer exchange coupling between hard and soft layers was achieved, and saturation magnetization was enhanced considerably after using interlayer exchange coupling with Fe. In addition, incoherent magnetization reversal process observed in FePt/Fe films changes into coherent switching process in FePt/C/Fe films giving rise to a single hysteresis loop. High temperature magnetic studies up to 573 K reveal that the effective reduction in the coercivity decreases largely from 34 Oe/K for FePt/Fe film to 13 Oe/K for FePt/C(0.5/Fe film demonstrating that the interlayer exchange coupling seems to be a promising approach to improve the stability of hard magnetic properties at high temperatures, which is suitable for high-performance magnets and thermally assisted magnetic recording media.

  19. One-step solution combustion synthesis of pure Ni nanopowders with enhanced coercivity: The fuel effect

    Science.gov (United States)

    Khort, Alexander; Podbolotov, Kirill; Serrano-García, Raquel; Gun'ko, Yurii K.

    2017-09-01

    In this paper, we report a new modified one-step combustion synthesis technique for production of Ni metal nanoparticles. The main unique feature of our approach is the use of microwave assisted foam preparation. Also, the effect of different types of fuels (urea, citric acid, glycine and hexamethylenetetramine) on the combustion process and characteristics of resultant solid products were investigated. It is observed that the combination of microwave assisted foam preparation and using of hexamethylenetetramine as a fuel allows producing pure ferromagnetic Ni metal nanoparticles with enhanced coercivity (78 Oe) and high value of saturation magnetization (52 emu/g) by one-step solution combustion synthesis under normal air atmosphere without any post-reduction processing.

  20. High magnetic fields science and technology

    CERN Document Server

    Miura, Noboru

    2003-01-01

    This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological syst

  1. Quench in high temperature superconductor magnets

    CERN Document Server

    Schwartz, J.

    2013-01-01

    High field superconducting magnets using high temperature superconductors are being developed for high energy physics, nuclear magnetic resonance and energy storage applications. Although the conductor technology has progressed to the point where such large magnets can be readily envisioned, quench protection remains a key challenge. It is well-established that quench propagation in HTS magnets is very slow and this brings new challenges that must be addressed. In this paper, these challenges are discussed and potential solutions, driven by new technologies such as optical fiber based sensors and thermally conducting electrical insulators, are reviewed.

  2. Endmember analysis of isothermal and high-temperature magnetization data from ODP 910C, Yermak Plateau, NW Svalbard

    Science.gov (United States)

    Fabian, Karl; Knies, Jochen; Kosareva, Lina; Nurgaliev, Danis

    2017-04-01

    Room temperature magnetic initial curves, upper hysteresis curves, acquisition curves of induced remanent magnetization (IRM), and backfield (BF) curves have been measured between -1.5 T and 1.5 T for more than 430 samples from Ocean Drilling Program (ODP) Hole 910C. The core was drilled in 556.4 m water depth on the southern Yermak Plateau (80°15.896'N, 6°35.430'E), NW Svalbard. In total, 507.4 m of sediments were cored, and average recovery was 57%, with 80% between 170 and 504.7 meter below seafloor (mbsf). For this study, the borehole was re-sampled between 150 mbsf and 504.7 mbsf for environmental magnetic, inorganic geochemical, and sedimentological analyses (443 samples). The lithology is mainly silty-clay with some enrichments of fine sands in the lower section (below 400 mbsf). For all samples, a Curie express balance was used to obtain the temperature dependence of induced magnetization in air at a heating rate of 100 °C/min up to a maximum temperature of 800 °C. The hysteresis curves were used to infer classical hysteresis parameters like saturation remanence (Mrs), saturation magnetization (Ms), remanence coercivity (Hcr) or coercivity (Hc). In addition several other parameters, like hysteresis energy, high-field slope or saturation field have been determined and help to characterize the down-core variation of the magnetic fractions. Acquisition curves of isothermal remanent magnetization are decomposed into endmembers using non-negative matrix factorization. The obtained mixing coefficients decompose hysteresis loops, back-field, thermomagnetic curves, geochemistry, and sedimentological parameters into their related endmember components. Down-core variation of the endmembers enables reconstruction of sediment transport processes and in-situ formation of magnetic mineral phases.

  3. 'Going to The Hague' as Coercive Leverage

    DEFF Research Database (Denmark)

    Schack, Marc

    2017-01-01

    (ICC) as leverage. This was the first time in history that an international actor used a possible recourse to the Court in such an explicitly coercive manner. Hence, this case enables us to conduct some preliminary analyses of this strategy’s effectiveness. Specifically, Palestine tried first to stop...

  4. Highly Efficient Freestyle Magnetic Nanoswimmer.

    Science.gov (United States)

    Li, Tianlong; Li, Jinxing; Morozov, Konstantin I; Wu, Zhiguang; Xu, Tailin; Rozen, Isaac; Leshansky, Alexander M; Li, Longqiu; Wang, Joseph

    2017-08-09

    The unique swimming strategies of natural microorganisms have inspired recent development of magnetic micro/nanorobots powered by artificial helical or flexible flagella. However, as artificial nanoswimmers with unique geometries are being developed, it is critical to explore new potential modes for kinetic optimization. For example, the freestyle stroke is the most efficient of the competitive swimming strokes for humans. Here we report a new type of magnetic nanorobot, a symmetric multilinked two-arm nanoswimmer, capable of efficient "freestyle" swimming at low Reynolds numbers. Excellent agreement between the experimental observations and theoretical predictions indicates that the powerful "freestyle" propulsion of the two-arm nanorobot is attributed to synchronized oscillatory deformations of the nanorobot under the combined action of magnetic field and viscous forces. It is demonstrated for the first time that the nonplanar propulsion gait due to the cooperative "freestyle" stroke of the two magnetic arms can be powered by a plane oscillatory magnetic field. These two-arm nanorobots are capable of a powerful propulsion up to 12 body lengths per second, along with on-demand speed regulation and remote navigation. Furthermore, the nonplanar propulsion gait powered by the consecutive swinging of the achiral magnetic arms is more efficient than that of common chiral nanohelical swimmers. This new swimming mechanism and its attractive performance opens new possibilities in designing remotely actuated nanorobots for biomedical operation at the nanoscale.

  5. Synchrotron Applications of High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF.

  6. Effect of high-energy ball milling time on structural and magnetic properties of nanocrystalline cobalt ferrite powders

    Energy Technology Data Exchange (ETDEWEB)

    Cedeño-Mattei, Yarilyn, E-mail: yarilyn.cedeno@upr.edu [Department of Chemistry, University of Puerto Rico—Mayagüez Campus, Mayagüez, PR 00681 (Puerto Rico); Perales-Pérez, Oscar [Department of Chemistry, University of Puerto Rico—Mayagüez Campus, Mayagüez, PR 00681 (Puerto Rico); Department of Engineering Science and Materials, University of Puerto Rico—Mayagüez Campus, Mayagüez, PR 00681 (Puerto Rico); Uwakweh, Oswald N.C. [Department of Engineering Science and Materials, University of Puerto Rico—Mayagüez Campus, Mayagüez, PR 00681 (Puerto Rico)

    2013-09-15

    Cobalt ferrite nanocrystals synthesized by conventional and size-controlled coprecipitation methods were treated by high-energy ball milling, HEBM, in order to study the effect of crystal size reduction and/or strain on the resulting magnetic properties. Processed nanocrystals were characterized by X-ray diffraction, Brunauer, Emmett, and Teller surface area analysis, transmission electron microscopy (TEM), and vibrating sample magnetometry. The cobalt ferrite nanocrystals exhibited crystal size reduction from initial values (average crystallite sizes of 12±1 nm and 18±3 nm, respectively) down to 10 nm after HEBM for 10 h. The specific surface area was decreased by milling (from 96.5 to 59.4 m{sup 2}/g; for the 12 nm cobalt ferrite nanocrystals), due to particles aggregation. TEM analyses corroborated the aggregation of the nanoparticles at such long milling times. The same cobalt ferrite nanocrystals exhibited a rise in coercivity from 394 to 560 Oe after 5 h ball milling which was attributed to the introduction of strain anisotropy, namely point defects, as suggested by the systematic shift of the diffraction peaks towards higher angles. In turn, the magnetic characterization of the starting 18 nm-nanocrystals reported a drop in coercivity from 4506 Oe to 491 Oe that was attributed predominantly to size reduction within the single domain region. A correlation between particle size, cationic distribution, and HEBM processing conditions became evident. - Highlights: • Effect of ball milling on the structural and magnetic properties of cobalt ferrite. • Prolonged milling promotes interparticle aggregation. • Tunable coercivity due to crystal size, strain, and cation distribution.

  7. Magnetization of High Density Hadronic Fluid

    DEFF Research Database (Denmark)

    Bohr, Henrik; Providencia, Constanca; da Providencia, João

    2012-01-01

    In the present paper the magnetization of a high density relativistic fluid of elementary particles is studied. At very high densities, such as may be found in the interior of a neutron star, when the external magnetic field is gradually increased, the energy of the normal phase of the fluid...... of the magnetization is derived by first considering and solving the Dirac equation of a fermion in interaction with a magnetic field and with a chiral sigma-pion pair. The solution provides the energies of single-particle states. The energy of the system is found by summing up contributions from all particles...

  8. Magnetic properties of barium ferrite after milling by high energy milling (hem

    Directory of Open Access Journals (Sweden)

    Idayanti Novrita

    2017-01-01

    Full Text Available Magnetic properties of barium ferrite that were mashed by High Energy Milling (HEM has been characterized. The starting iron oxide powder (Fe2O3 and barium carbonate (BaCO3 were prepared by powder metallurgy technique by the stages of mixing, calcining, milling, compacting, and sintering. Weight ratio of Fe2O3: BaCO3 was 88.74 wt% : 17.52 wt%. Some additives such as calcium oxide (CaO, silicon dioxide (SiO2, and polyvinyl alcohol (PVA were added after calcining process. Milling by HEM was varied at 30, 60, 90, 120, and 150 minutes. The ball and container of HEM were made of stainless steel. Characterization micro structure by SEM showed that the milling time affect the grain size of the magnetic powder. The longer of milling time, the grain size was smaller and uniform. Characterization by using magnetic instrument Permagraph showed that the grain size will affect the magnetic properties of barium ferrite. Induction of remanence (Br, coercivity (HcJ, and product energy maximum (BHmax values increased with increasing milling time. The optimal magnetic properties were obtained at the time of milling 120 minutes with value of Hc = 1.97 kG, HcJ = 2.314 kOe, and BHmax = 0.64 MGOe.

  9. Hybrid Spintronic Structures With Magnetic Oxides and Heusler Alloys

    DEFF Research Database (Denmark)

    Xu, Y. B.; Hassan, S. S. A.; Wong, P. K. J.

    2008-01-01

    As(100) and the unit cell of the Fe3O4 was found to be rotated by 45 degrees to match the gallium arsenide GaAs. The films were found to have a bulk-like moment down to 3-4 nm and a low coercivity indicating a high-quality magnetic interface. The magnetization hysteresis loops of the ultrathin films...

  10. High Field Pulse Magnets with New Materials

    Science.gov (United States)

    Li, L.; Lesch, B.; Cochran, V. G.; Eyssa, Y.; Tozer, S.; Mielke, C. H.; Rickel, D.; van Sciver, S. W.; Schneider-Muntau, H. J.

    2004-11-01

    High performance pulse magnets using the combination of CuNb conductor and Zylon fiber composite reinforcement with bore sizes of 24, 15 and 10 mm have been designed, manufactured and tested to destruction. The magnets successfully reached the peak fields of 64, 70 and 77.8 T respectively with no destruction. Failures occurred near the end flanges at the layer. The magnet design, manufacturing and testing, and the mode of the failure are described and analyzed.

  11. Effect of Flake Thickness on Coercivity of Nanocrystalline SmCo5 Bulk Prepared from Anisotropic Nanoflake Powder (Postprint)

    Science.gov (United States)

    2016-08-23

    flake thickness. 15. SUBJECT TERMS rare earth magnets , samarium cobalt magnets , permanent magnets 16. SECURITY CLASSIFICATION OF: 17...nanoflakes have attractive magnetic properties ; coercivity of up to 21 kOe and maximum energy product of up to 22 MGOe.9 Thus, the nanoflake powders...less reported on correlation between nanoflake morphology and final properties of the SmCo5 bulk magnets . In this study, we prepared SmCo5 nanoflakes

  12. The Coercive Sterilization of Aboriginal Women in Canada

    Science.gov (United States)

    Stote, Karen

    2012-01-01

    This paper considers the coercive sterilization of Aboriginal women in legislated and non-legislated form in Canada. I provide an historical and materialist critique of coercive sterilization. I argue for coercive sterilization to be understood as one of many policies employed to undermine Aboriginal women, to separate Aboriginal peoples from…

  13. High magnetic field magnetization of a new triangular lattice antiferromagnet

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, H. D. [Univ. of Tennessee, Knoxville, TN (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab); Stritzinger, Laurel Elaine Winter [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harrison, Neil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-23

    In CsV(MoO4)2, the magnetic V3+ ions with octahedral oxygen-coordination form a geometrically frustrated triangular lattice. So fare, there is no magnetic properties reported on it. Recently, we successfully grew single crystals of CsV(MoO4)2 by using flux method. The susceptibility shows a sharp drop around 24 K, representing a long range magnetic ordering. To understand the physical properties of this new triangular lattice antiferromagnet (TLAF), we pursued high field magnetization measurements to answer two questions: (i) what is the saturation field, which will be very useful to calculate the exchange interaction of the system? (ii) Will it exhibit spin state transition, such as the up up down phase with 1/3-saturation moment as other TLAFs? Recently, we performed VSM measurements in Cell 8, Tallahassee, NHMFL, the results show that the magnetization reaches 0.38 MuB at 34 T, which is just 19% of the full moment of 2 MuB for V3+ (3d2) ions. Apparently we need higher field to reach 1/3 value or full moment.

  14. Superconductivity from magnetic elements under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Katsuya [KYOKUGEN, Research Center for Materials Science at Extreme Conditions, Osaka University, Osaka 560-8531 (Japan)]. E-mail: shimizu@rcem.osaka-u.ac.jp; Amaya, Kiichi [Toyota Physical and Chemical Research Institute, Aichi 480-1192 (Japan); Suzuki, Naoshi [Graduate School of Engineering Science, Osaka University, Osaka 560-8531 (Japan); Onuki, Yoshichika [Graduate School of Science, Osaka University, Osaka 560-0043 (Japan)

    2006-05-01

    Can we expect the appearance of superconductivity from magnetic elements? In general, superconductivity occurs in nonmagnetic metal at low temperature and magnetic impurities destroy superconductivity; magnetism and superconductivity are as incompatible as oil and water. Here, we present our experimental example of superconducting elements, iron and oxygen. They are magnetic at ambient pressure, however, they become nonmagnetic under high pressure, then superconductor at low temperature. What is the driving force of the superconductivity? Our understanding in the early stages was a simple scenario that the superconductive state was obtained as a consequence of an emergence of the nonmagnetic states. In both cases, we may consider another scenario for the appearance of superconductivity; the magnetic fluctuation mechanism in the same way as unconventional superconductors.

  15. Three-Dimensional Self-Assembly of Core/Shell-Like Nanostructures for High-Performance Nanocomposite Permanent Magnets.

    Science.gov (United States)

    Li, Hailing; Li, Xiaohong; Guo, Defeng; Lou, Li; Li, Wei; Zhang, Xiangyi

    2016-09-14

    Core/shell nanostructures are fascinating for many advanced applications including strong permanent magnets, magnetic recording, and biotechnology. They are generally achieved via chemical approaches, but these techniques limit them to nanoparticles. Here, we describe a three-dimensional (3D) self-assembly of core/shell-like nanocomposite magnets, with hard-magnetic Nd2Fe14B core of ∼45 nm and soft-magnetic α-Fe shell of ∼13 nm, through a physical route. The resulting Nd2Fe14B/α-Fe core/shell-like nanostructure allows both large remanent magnetization and high coercivity, leading to a record-high energy product of 25 MGOe which reaches the theoretical limit for isotropic Nd2Fe14B/α-Fe nanocomposite magnets. Our approach is based on a sequential growth of the core and shell nanocrystals in an alloy melt. These results make an important step toward fabricating core/shell-like nanostructure in 3D materials.

  16. Magnetic and Superconducting Materials at High Pressures

    Energy Technology Data Exchange (ETDEWEB)

    Struzhkin, Viktor V. [Carnegie Inst. of Washington, Washington, DC (United States)

    2015-03-24

    The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including

  17. High-temperature soft magnetic properties of antiperovskite nitrides ZnNFe{sub 3} and AlNFe{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Yankun [College of Science, Shangdong University of Science and Technolog, Qingdao 266510 (China); Lin, Shuai, E-mail: linshuai17@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Wang, Bosen, E-mail: bswang@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2015-03-15

    We report the synthesis, crystal structure, magnetic and electrical/thermal transport properties of antiperovskite nitrides ZnNFe{sub 3} and AlNFe{sub 3}. Both compounds display ferromagnetic (FM) ground state and transform into the paramagnetic phase at 762 K and 770 K, respectively. At FM phase, for ZnNFe{sub 3} and AlNFe{sub 3}, the saturated magnetizations at 5 K are 163 and 188 emu/g, which is the largest value among all the antiperovskite compounds; the minimal coercive forces (H{sub C}) are as low as 18.6 and 16.3 Oe; the low H{sub C} is almost constant covering a broad temperature range of 5–650 K. These characteristics indicate that both ZnNFe{sub 3} and AlNFe{sub 3} may be promising candidates of high-temperature soft magnetic material. In addition, electrons are dominant carriers owing to the negative Seebeck coefficient, the Fermi-liquid behavior is well presented via the investigation of low-temperature electrical transport, and the lattice thermal conductivity estimated by Wiedemann–Franz law is the main part of total thermal conductivity at high temperatures for both ZnNFe{sub 3} and AlNFe{sub 3}. - Highlights: • A two-step synthetic method for high quality ZnNFe{sub 3} and AlNFe{sub 3} was demonstrated. • High Curie temperature and saturated magnetization but low coercive fields are observed. • The specific heat and electrical/thermal transport properties are investigated.

  18. Inducing magnetic anisotropy and optimized microstructure in rapidly solidified Nd-Fe-B based magnets by thermal gradient, magnetic field and hot deformation

    Science.gov (United States)

    Zhao, L. Z.; Li, W.; Wu, X. H.; Hussain, M.; Liu, Z. W.; Zhang, G. Q.; Greneche, J. M.

    2016-10-01

    Direct preparation of Nd-Fe-B alloys by rapid solidification of copper mold casting is a very simple and low cost process for mini-magnets, but these magnets are generally magnetically isotropic. In this work, high coercivity Nd24Co20Fe41B11Al4 rods were produced by injection casting. To induce magnetic anisotropy, temperature gradient, assisted magnetic field, and hot deformation (HD) procedures were employed. As-cast samples showed non-uniform microstructure due to the melt convection. The thermal gradient during solidification led to the formation of radially distributed acicular hard magnetic grains, which gives the magnetic anisotropy. The growth of the oriented grains was confirmed by phase field simulation. A magnetic field up to 1 T applied along the casting direction could not induce significant magnetic anisotropy, but it improved the magnetic properties by reducing the non-uniformity and forming a uniform microstructure. The annealed alloys exhibited high intrinsic coercivity but disappeared anisotropy. HD was demonstrated to be a good approach for inducing magnetic anisotropy and enhanced coercivity by deforming and refining the grains. This work provides an alternative approach for preparing fully dense Nd-rich anisotropic bulk Nd-Fe-B magnets.

  19. Wuhan pulsed high magnetic field center

    OpenAIRE

    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; Duan, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  20. An Approach for Preparing High-Performance MnBi Alloys and Magnets

    Science.gov (United States)

    Van Nguyen, Vuong; Nguyen, Truong Xuan

    2017-06-01

    MnBi alloys were arc-melted and solidified by different cooling rates, which resulted in microstructures with different sizes of Mn grains embedded in the matrix consisting of Bi and MnBi phases. By annealing at an appropriate temperature and duration, the Mn grains become MnBi grains caused by their combination with the surrounding Bi. This process enhances the MnBi content leading to the large spontaneous magnetization ( M s) of alloyed samples. The coercivity (i H c) of alloys is determined mostly by the MnBi grain distribution formed during the annealing process. Consequently, an alloy of large M s and i H c can be produced by controlling the required cooling rate as it figures␣in the arc-melting process and the appropriate annealing. The high-performance MnBi alloy was cold ball-milled into fine powders that were used for preparing MnBi bulk magnets by aligning in an 18 kOe-field followed by warm-compaction at 280°C and 12 MPa for 10 min. The magnet is highly anisotropic with an energy product of 7 MGOe.

  1. Novel High Temperature Magnetic Bearings for Space Vehicle Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Previous high temperature magnetic bearings employed only electromagnets. The work proposed in this SBIR program seeks to utilize High Temperature Permanent Magnets...

  2. Novel High Temperature Magnetic Bearings for Space Vehicle Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Previous high temperature magnetic bearings employed electromagnets only. The work proposed in this SBIR program seeks to utilize High Temperature Permanent Magnets...

  3. Neutron Scattering and High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Winn, Barry L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Stone, Matthew B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-11-01

    The workshop “Neutron Scattering and High Magnetic Fields” was held September 4-5, 2014 at the Oak Ridge National Laboratory (ORNL). The workshop was held in response to a recent report by the National Research Council of the National Academy of Sciences entitled “High Magnetic Field Science and Its Application in the United States: Current Status and Future Directions.”1 This report highlights the fact that neutron scattering measurements carried out in high magnetic fields provide important opportunities for new science. The workshop explored the range of the scientific discoveries that could be enabled with neutron scattering measurements at high fields (25 Tesla or larger), the various technologies that might be utilized to build specialized instruments and sample environment equipment to enable this research at ORNL, and possible routes to funding and constructing these facilities and portable high field sample environments.

  4. High-frequency behavior of magnetic composites

    Science.gov (United States)

    Lagarkov, Andrey N.; Rozanov, Konstantin N.

    2009-07-01

    The paper reviews recent progress in the field of microwave magnetic properties of composites. The problem under discussion is developing composites with high microwave permeability that are needed in many applications. The theory of magnetic composites is briefly sketched with the attention paid to the laws governing the magnetic frequency dispersion in magnetic materials and basic mixing rules for composites. Recent experimental reports on the microwave performance of magnetic composites, as well as data on the agreement of the mixing rules with the measured permeability of composites that are available from the literature are discussed. From the data, a conclusion is made that the validity of a mixing rule is determined by the permeability contrast in the composite, i.e., the difference between permeability of inclusions and that of the host matrix. When the contrast is low, the Maxwell Garnet mixing rule is frequently valid. When the contrast is high, which is of the most interest for obtaining high microwave permeability of a composite, no conventionally accepted theory is capable of accurately predicting the permeability of the composites. Therefore, the mixing rules do not allow the microwave properties of magnetic composites to be predicted when the permeability of inclusions is high, that is the case of the most interest. Because of that, general limitations to the microwave performance of composites are of importance. In particular, an important relation constraining the microwave permeability of composites follows from Kittel's theory of ferromagnetic resonance and analytical properties of frequency dependence of permeability. Another constraint concerning the bandwidth of electromagnetic wave absorbers follows from the Kramers-Kronig relations for the reflection coefficient. The constraints are of importance in design and analysis of electromagnetic wave absorbers and other devices that employ the microwave magnetic properties of composites, such as

  5. Proliferation Persuasion. Coercive Bargaining with Nuclear Technology

    Energy Technology Data Exchange (ETDEWEB)

    Volpe, Tristan A. [George Washington Univ., Washington, DC (United States)

    2015-08-31

    Why do states wait for prolonged periods of time with the technical capacity to produce nuclear weapons? Only a handful of countries have ever acquired the sensitive nuclear fuel cycle technology needed to produce fissile material for nuclear weapons. Yet the enduring trend over the last five decades is for these states to delay or forgo exercising the nuclear weapons option provided by uranium enrichment or plutonium reprocessing capabilities. I show that states pause at this threshold stage because they use nuclear technology to bargain for concessions from both allies and adversaries. But when does nuclear latency offer bargaining benefits? My central argument is that challengers must surmount a dilemma to make coercive diplomacy work: the more they threaten to proliferate, the harder it becomes to reassure others that compliance will be rewarded with nuclear restraint. I identify a range of mechanisms able to solve this credibility problem, from arms control over breakout capacity to third party mediation and confidence building measures. Since each step towards the bomb raises the costs of implementing these policies, a state hits a sweet spot when it first acquires enrichment and/or reprocessing (ENR) technology. Subsequent increases in proliferation capability generate diminishing returns at the bargaining table for two reasons: the state must go to greater lengths to make a credible nonproliferation promise, and nuclear programs exhibit considerable path dependency as they mature over time. Contrary to the conventional wisdom about power in world politics, less nuclear latency thereby yields more coercive threat advantages. I marshal new primary source evidence from archives and interviews to identify episodes in the historical record when states made clear decisions to use ENR technology as a bargaining chip, and employ this theory of proliferation persuasion to explain how Japan, North Korea, and Iran succeeded and failed to barter concessions from the

  6. The high squareness Sm-Co magnet having Hcb=10.6 kOe at 150°C

    Science.gov (United States)

    Machida, Hiroaki; Fujiwara, Teruhiko; Kamada, Risako; Morimoto, Yuji; Takezawa, Masaaki

    2017-05-01

    The relationship between magnetic properties and magnetic domain structures of Sm(Fe, Cu, Zr, Co)7.5 magnet was investigated. The developed Sm-Co magnet, which is conducted homogenization heat treatment at ingot state, high temperature short time sintering and long time solid solution heat treatment showed the maximum energy product, [BH]m of 34.0 MGOe and the coercivity, Hcb of 11.3 kOe at 20°C respectively. Moreover, Hcb of 10.6 kOe at 150°C was achieved. Heat treated ingot has clear 1-7 phase in mother phase from optical microscope observation. Kerr effect microscope with magnetic field applied was used to investigate magnetic domain structure. Reverse magnetic domains were generated evenly but generation of them from inside grain were not observed. Cell structure was observed by scanning transmission electron microscope and composition analysis was conducted by energy dispersive X-ray spectroscopy. Cell size was approximately 150 ˜ 300 nm, Fe and Cu were clearly separated and concentrated to 2-17 phase and 1-5 phase respectively. Moreover, Cu concentration went up to 40 at% in 1-5 phase. That means the gap of domain wall energy between 1-5 phase and 2-17 phase was increased due to microstructure control by conducting heat treatment for compositional homogeneity.

  7. The high squareness Sm-Co magnet having Hcb=10.6 kOe at 150°C

    Directory of Open Access Journals (Sweden)

    Hiroaki Machida

    2017-05-01

    Full Text Available The relationship between magnetic properties and magnetic domain structures of Sm(Fe, Cu, Zr, Co7.5 magnet was investigated. The developed Sm-Co magnet, which is conducted homogenization heat treatment at ingot state, high temperature short time sintering and long time solid solution heat treatment showed the maximum energy product, [BH]m of 34.0 MGOe and the coercivity, Hcb of 11.3 kOe at 20°C respectively. Moreover, Hcb of 10.6 kOe at 150°C was achieved. Heat treated ingot has clear 1-7 phase in mother phase from optical microscope observation. Kerr effect microscope with magnetic field applied was used to investigate magnetic domain structure. Reverse magnetic domains were generated evenly but generation of them from inside grain were not observed. Cell structure was observed by scanning transmission electron microscope and composition analysis was conducted by energy dispersive X-ray spectroscopy. Cell size was approximately 150 ∼ 300 nm, Fe and Cu were clearly separated and concentrated to 2-17 phase and 1-5 phase respectively. Moreover, Cu concentration went up to 40 at% in 1-5 phase. That means the gap of domain wall energy between 1-5 phase and 2-17 phase was increased due to microstructure control by conducting heat treatment for compositional homogeneity.

  8. Ultrahigh coercivity and core-shell microstructure achieved in oriented Nd-Fe-B thin films diffusion-processed with Dy-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tongbo; Zhou, Xiaoqian; Yu, Dedong; Fu, Yanqing; Cui, Weibin [Northeastern University, Key Laboratory of Electromagnetic Processing of Materials (EPM), Ministry of Education, Shenyang (China); Northeastern University, Department of Physics and Chemistry of Materials, School of Materials Science and Engineering, Shenyang (China); Li, Guojian; Wang, Qiang [Northeastern University, Key Laboratory of Electromagnetic Processing of Materials (EPM), Ministry of Education, Shenyang (China)

    2017-01-15

    Ultrahigh ambient coercivities of ∝4 T were achieved in Nd-Fe-B benchmark thin film with coercivity of 1.06 T by diffusion-processing with Dy, Dy{sub 70}Cu{sub 30} and Dy{sub 80}Ag{sub 20} alloy layer. High texture and good squareness were obtained. In triple-junction regions, Dy element was found to be immiscible with Nd element. Microstructure observation indicated the typical gradient elementary distribution. Unambiguous core/shell microstructure was characterized by transition electron microscopy. Due to the enhanced ambient coercivity, the coercivity temperature stability was also substantially increased. (orig.)

  9. FY1995 preparation of magnetic films with nano size magnetic domain structure and application for magnetic recording media with ultra-high density; 1995 nendo nano jiku seigyo jisei usumaku no sosei to chokomitsudo jiki kiroku media eno oyo

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    It is required to control microstructure and micro magnetic behavior in Co-Cr based alloy thin films strictly in order to apply these thin films to the ultra high density magnetic recording media. In this study, thin film deposition technology to control nano-metric micro-structure and micro magnetic properties, especially in the distribution through thickness direction, were examined. Furthermore, to develop some evaluation technique to determine such local distribution of magnetic properties was one of the purpose of this study. The relationship between c-axis orientation of crystallites and distribution of the perpendicular coercivity H{sub c} in Co-Cr films has been investigated through the evaluation of the the H{sub c} of surface layer H{sub c}(s) measured by Kerr hysteresis loop tracer. Better c-axis orientation, higher Cr content and addition of Ta seemed to be essential requirements to get higher H{sub c} of initial growth layer H{sub c}(i) and good uniformity of H{sub c}. Lower {delta}H{sub c} caused better recording characteristics and lower media noise level. It has been clarified that the homogeneity of the magnetic properties in the film and c-axis orientation in the initial layer of the films were the essential factors to deposit low noise and high performance recording media. (NEDO)

  10. Pulsing ULXs as highly magnetized neutron stars

    Science.gov (United States)

    Mushtukov, A.; Suleimanov, V.; Tsygankov, S.; Poutanen, J.

    2017-10-01

    A recent discovery of three pulsing ultraluminous X-ray sources (ULXs) demonstrates that a significant part of ULXs could be magnetized neutron stars with extremely high mass accretion rates. Theoreticians are thus faced with a significant challenge to invent a way for transforming a highly super-Eddington accretion rate into pulsing photon luminosity. We suggested a model of the two tall accretion columns above a strongly magnetized (B ˜ 10^{14} G) neutron star surface in the vicinity of the magnetic poles as a source of this radiation, and showed that their luminosity can be as high as 10^{40} erg s^{-1}. We present the basic ideas of the model as well as possible directions for improving the model to increase its maximum possible luminosity. The results of application of the model to the ULX M82 X-2 and to other pulsed ULXs are presented.

  11. Coercive and disruptive behaviors in pediatric obsessive-compulsive disorder.

    Science.gov (United States)

    Lebowitz, Eli R; Omer, Haim; Leckman, James F

    2011-10-03

    This study explored the nature of disruptive and coercive behaviors in pediatric obsessive-compulsive disorder (OCD). Thirty children with OCD and a disruptive behavior disorder (DBD) were compared to 30 children with DBD alone using the Child Behavior Checklist and a novel 18-item questionnaire focused on distinctive coercive and disruptive behaviors seen in pediatric OCD (CD-POC). Although youth with DBD alone had higher ratings of Externalizing Behaviors on the CBCL compared to the youth with OCD + DBD, their ratings on the CB-POC scale were lower. For example, 83% of OCD + DBD parents reported that their child "Imposes rules or behaviors on others due to tactile or other sensitivity and reacts to disobedience with rage or violence (e.g. forbids certain sounds, demands specific temperature settings)" compared to 23% of the parents of youth with DBD alone. Other highly discriminating behaviors included: "Demands special 'cuddling' or ritualized contact without regard for the will of others" and "Forbids the use of objects in his/her vicinity because of feelings of fear or disgust (e.g. knives, scissors, creams)." Total scores on the CD-POC were also correlated with OCD severity (P<.01). The results suggest that the nature of DBD in pediatric OCD may be distinctive and worthy of further study. © 2011 Wiley-Liss, Inc.

  12. Tailoring the soft magnetic properties of sputtered multilayers by microstructure engineering for high frequency applications

    Directory of Open Access Journals (Sweden)

    Claudiu V. Falub

    2017-05-01

    Full Text Available Soft magnetic Ni78.5Fe21.5, Co91.5Ta4.5Zr4 and Fe52Co28B20 thin films laminated with SiO2, Al2O3, AlN, and Ta2O5 dielectric interlayers were deposited on 8” Si wafers using DC, pulsed DC and RF cathodes in the industrial, high-throughput Evatec LLS-EVO-II magnetron sputtering system. A typical multilayer consists of a bilayer stack up to 50 periods, with alternating (50-100 nm thick magnetic layers and (2-20 nm thick dielectric interlayers. We introduced the in-plane magnetic anisotropy in these films during sputtering by a combination of a linear magnetic field, seed layer texturing by means of linear collimators, and the oblique incidence inherent to the geometry of the sputter system. Depending on the magnetic material, the anisotropy field for these films was tuned in the range of ∼(7-120 Oe by choosing the appropriate interlayer thickness, the aspect ratios of the linear collimators in front of the targets, and the sputter process parameters (e.g. pressure, power, DC pulse frequency, while the coercivity was kept low, ∼(0.05-0.9 Oe. The alignment of the easy axis (EA on the 8” wafers was typically between ±1.5° and ±4°. We discuss the interdependence of structure and magnetic properties in these films, as revealed by atomic force microscopy (AFM, X-ray reflectivity (XRR with reciprocal space mapping (RSM and magneto-optical Kerr effect (MOKE measurements.

  13. Tailoring the soft magnetic properties of sputtered multilayers by microstructure engineering for high frequency applications

    Science.gov (United States)

    Falub, Claudiu V.; Rohrmann, Hartmut; Bless, Martin; Meduňa, Mojmír; Marioni, Miguel; Schneider, Daniel; Richter, Jan H.; Padrun, Marco

    2017-05-01

    Soft magnetic Ni78.5Fe21.5, Co91.5Ta4.5Zr4 and Fe52Co28B20 thin films laminated with SiO2, Al2O3, AlN, and Ta2O5 dielectric interlayers were deposited on 8" Si wafers using DC, pulsed DC and RF cathodes in the industrial, high-throughput Evatec LLS-EVO-II magnetron sputtering system. A typical multilayer consists of a bilayer stack up to 50 periods, with alternating (50-100) nm thick magnetic layers and (2-20) nm thick dielectric interlayers. We introduced the in-plane magnetic anisotropy in these films during sputtering by a combination of a linear magnetic field, seed layer texturing by means of linear collimators, and the oblique incidence inherent to the geometry of the sputter system. Depending on the magnetic material, the anisotropy field for these films was tuned in the range of ˜(7-120) Oe by choosing the appropriate interlayer thickness, the aspect ratios of the linear collimators in front of the targets, and the sputter process parameters (e.g. pressure, power, DC pulse frequency), while the coercivity was kept low, ˜(0.05-0.9) Oe. The alignment of the easy axis (EA) on the 8" wafers was typically between ±1.5° and ±4°. We discuss the interdependence of structure and magnetic properties in these films, as revealed by atomic force microscopy (AFM), X-ray reflectivity (XRR) with reciprocal space mapping (RSM) and magneto-optical Kerr effect (MOKE) measurements.

  14. High temperature superconductors for magnetic suspension applications

    Science.gov (United States)

    Mcmichael, C. K.; Cooley, R. S.; Chen, Q. Y.; Ma, K. B.; Lamb, M. A.; Meng, R. L.; Chu, C. W.; Chu, W. K.

    1994-01-01

    High temperature superconductors (HTS) hold the promise for applications in magnetic levitation bearings, vibration damping, and torque coupling. Traditional magnetic suspension systems require active feedback and vibration controls in which power consumption and low frequency vibration are among the major engineering concerns. HTS materials have been demonstrated to be an enabling approach towards such problems due to their flux trapping properties. In our laboratory at TCSUH, we have been conducting a series of experiments to explore various mechanical applications using HTS. We have constructed a 30 lb. model flywheel levitated by a hybrid superconducting magnetic bearing (HSMB). We are also developing a levitated and vibration-dampled platform for high precision instrumentation. These applications would be ideal for space usages where ambient temperature is adequate for HTS to operate properly under greatly reduced cryogenic requirements. We will give a general overview of these potential applications and discuss the operating principles of the HTS devices we have developed.

  15. The effect of particle size on coercivity and crystallinity of SmCo5

    Energy Technology Data Exchange (ETDEWEB)

    Chen, CH; Knutson, SJ; Shen, Y; Wheeler, RA; Horwath, JC; Barnes, PN

    2011-07-04

    It is observed a turning point in the particle size for which the coercivity H-ci of a Sm-Co alloy reaches a peak. Using a broad size range from 20 nm to 5 mm, the turning point of the flake thickness for SmCo5 nanoflakes is determined in the range of 100-180 nm with H-ci peak at similar to 20 kOe. A lower coercivity at a particle size well below the turning point is likely related to a more detailed nanoscale morphology that controls coercivity. The effect of particle size on crystallinity for high energy milled powder is also discussed with four observations. (C) 2011 American Institute of Physics. [doi:10.1063/1.3607958

  16. Structural and magnetic properties of new uniaxial nanocrystalline Pr5Co19 compound

    Science.gov (United States)

    Bouzidi, W.; Mliki, N.; Bessais, L.

    2017-11-01

    Highly-coercive nanocrystalline Pr5Co19 powders have been synthesized by mechanical milling for the first time. The structural properties are studied by X-ray diffraction and refined with Rietveld method. This analysis revealed that whatever annealing temperature, samples crystallize in the rhombohedral (3R) of Ce5Co19-type structure (space group R 3 bar m). The magnetization curve as a function of temperature shows a magnetic transition state at the Curie temperature TC = 690 K. The optimum hard magnetic properties have been obtained for Pr5Co19 milled for 5 h and annealed at 1048 K for 30 min. These alloys exhibit a coercivity of 15 kOe at room temperature. This high coercivity is attributed to the high uniaxial magnetocrystalline anisotropy, nanoscale grain size, and to the homogeneous nanostructure developed by mechanical milling process and subsequent annealing.

  17. Size-dependent structure and magnetic properties of co-evaporated Fe-SiO2 nanoparticle composite film under high magnetic field

    Directory of Open Access Journals (Sweden)

    Yonghui Ma

    2016-05-01

    Full Text Available Composite film of Fe nanoparticles embedded in a SiO2 matrix has been prepared by the co-evaporation of Fe and SiO2. Both source temperature and in-situ high magnetic field (HMF have been used to adjust the Fe particle size and the growth of Fe-SiO2 film. The size of Fe particle decreased with increasing the source temperature without HMF. When HMF was presented during the growth of the film, the size of Fe particle was enlarged and reduced for source temperatures of 1300 °C and 1400 °C, respectively. Meanwhile, the preferred orientation of the film grown at 1400 °C became uniform with the application of HMF. In addition, it is also found that the film was formed in two layers. One layer is formed by the Fe particle, while the other is free of Fe particles due to the existence of more SiO2. The structural variation has a significant effect on the magnetic properties. The coercivity (90 Oe of the 1300 °C film is much higher than that (6 Oe of the 1400 °C film with a small particle size and uniform orientation. The saturation magnetization can be increased by increasing the Fe particle volume fraction. This study develops a new method to tune the soft magnetic properties by the co-evaporation of Fe and SiO2.

  18. Physics of semiconductors in high magnetic fields

    CERN Document Server

    Miura, Noboru

    2008-01-01

    This book summarizes most of the fundamental physical phenomena which semiconductors and their modulated structures exhibit in high magnetic fields. Readers can learn not only the basic theoretical background but also the present state of the art from the most advanced data in this rapidly growing research area.

  19. Strain sensors for high field pulse magnets

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Christian [Los Alamos National Laboratory; Zheng, Yan [Los Alamos National Laboratory; Easton, Daniel [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory

    2009-01-01

    In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective of this preliminary study is to characterize the performance of various strain sensing technologies at liquid nitrogen temperatures (-196 C). Four sensor types are considered in this investigation: fiber Bragg gratings (FBG), resistive foil strain gauges (RFSG), piezoelectric polymers (PVDF), and piezoceramics (PZT). Three operational conditions are considered for each sensor: bond integrity, sensitivity as a function of temperature, and thermal cycling effects. Several experiments were conducted as part of this study, investigating adhesion with various substrate materials (stainless steel, aluminum, and carbon fiber), sensitivity to static (FBG and RFSG) and dynamic (RFSG, PVDF and PZT) load conditions, and sensor diagnostics using PZT sensors. This work has been conducted in collaboration with the National High Magnetic Field Laboratory (NHMFL), and the results of this study will be used to identify the set of sensing technologies that would be best suited for integration within high field pulsed magnets at the NHMFL facility.

  20. Crystallization behavior and magnetic properties in High Fe content FeBCSiCu alloy system

    Science.gov (United States)

    Fan, X. D.; Shen, B. L.

    2015-07-01

    High Fe content FeBCSiCu nanocrystalline alloys are prepared by annealing melt-spun amorphous ribbons with aim at increasing saturation magnetic flux density. Microstructures identified by XRD and TEM reveal that Cu addition inhibits the surface crystallization of Fe86B7C7 alloy and improve its glass-forming ability. Activation energy of crystallization calculated by Kissinger's equation indicates that both Cu and Si addition promotes the precipitation of α-Fe phase and improves the thermal stability. VSM and DC B-H loop tracer measurements show that the Fe85.5B7C6Si1Cu0.5 nanocrystalline alloy exhibits high saturation magnetic flux density of 1.8 T and low coercivity of 10 A/m, respectively. AC properties measured by AC B-H analyzer show this alloy exhibits low core loss of 0.35 W/kg at 1 T at 50 Hz. Low material cost and convenient productivity make the Fe85.5B7C6Si1Cu0.5 nanocrystalline alloy an economical application in industry.

  1. Extraordinary Hall-effect in colloidal magnetic nanoparticle films

    Science.gov (United States)

    Ben Gur, Leah; Tirosh, Einat; Segal, Amir; Markovich, Gil; Gerber, Alexander

    2017-03-01

    Colloidal nickel nanoparticles (NPs) coated with polyvinylpyrrolidone (PVP) were synthesized. The nanoparticle dispersions were deposited on substrates and dried under mild heating to form conductive films. The films exhibited very small coercivity, nearly metallic conductivity, and a significant extraordinary Hall effect signal. This method could be useful for preparing simple, printed magnetic field sensors with the advantage of relatively high sensitivity around zero magnetic field, in contrast to magnetoresistive sensors, which have maximal field sensitivity away from zero magnetic field.

  2. Magnetic and High-Frequency Dielectric Parameters of Divalent Ion-Substituted W-Type Hexagonal Ferrites

    Science.gov (United States)

    Ali, Akbar; Grössinger, R.; Imran, Muhammad; Khan, M. Ajmal; Elahi, Asmat; Akhtar, Majid Niaz; Mustafa, Ghulam; Khan, Muhammad Azhar; Ullah, Hafeez; Murtaza, Ghulam; Ahmad, Mukhtar

    2017-02-01

    Polycrystalline W-type hexagonal ferrites with chemical formulae Ba0.5Sr0.5 Co2- x Me x Fe16O27 ( x = 0, 0.5, Me = Mn, Mg, Zn, Ni) have been prepared using sol-gel autocombustion. It has been reported in our earlier published work that all the samples exhibit a single-phase W-type hexagonal structure which was confirmed by x-ray diffraction (XRD) analysis. The values of bulk density lie in the range of 4.64-4.78 g/cm3 for all the samples which are quite high as compared to those for other types of hexaferrites. It was also observed that Zn-substituted ferrite reflects the highest (14.7 × 107 Ω-cm) whereas Mn-substituted ferrite has the lowest (11.3 × 107 Ω-cm) values of direct current (DC) electrical resistivity. The observed values of saturation magnetization ( M s) are found to be in the range of 62.01-68.7 emu/g depending upon the type of cation substitution into the hexagonal lattice. All the samples exhibit a typical soft magnetic character with low values of coercivity ( H c) that are in the range of 26-85 Oe. These ferrites may be promising materials for microwave absorbers due to their higher saturation magnetization and low coercivities. Both the dielectric constant and tangent loss decrease with increasing frequency in the lower frequency region and become constant in the higher frequency region. The much lower dielectric constant obtained in this study makes the investigated ferrites very useful for high-frequency applications, i.e. dielectric resonators and for camouflaging military targets such as ships, tanks and aircrafts, etc.

  3. Industrialization of nanocrystalline Fe–Si–B–P–Cu alloys for high magnetic flux density cores

    Energy Technology Data Exchange (ETDEWEB)

    Takenaka, Kana, E-mail: k-takenaka@imr.tohoku.ac.jp [Research and Development Center for Ultra High Efficiency Nano-crystalline Soft Magnetic Materials, Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577 (Japan); Setyawan, Albertus D.; Sharma, Parmanand; Nishiyama, Nobuyuki [Research and Development Center for Ultra High Efficiency Nano-crystalline Soft Magnetic Materials, Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577 (Japan); Makino, Akihiro [Tohoku University, Sendai, Miyagi 980-8577 (Japan)

    2016-03-01

    Nanocrystalline Fe–Si–B–P–Cu alloys exhibit high saturation magnetic flux density (B{sub s}) and extremely low magnetic core loss (W), simultaneously. Low amorphous-forming ability of these alloys hinders their application potential in power transformers and motors. Here we report a solution to this problem. Minor addition of C is found to be effective in increasing the amorphous-forming ability of Fe–Si–B–P–Cu alloys. It allows fabrication of 120 mm wide ribbons (which was limited to less than 40 mm) without noticeable degradation in magnetic properties. The nanocrystalline (Fe{sub 85.7}Si{sub 0.5}B{sub 9.5}P{sub 3.5}Cu{sub 0.8}){sub 99}C{sub 1} ribbons exhibit low coercivity (H{sub c})~4.5 A/m, high B{sub s}~1.83 T and low W~0.27 W/kg (@ 1.5 T and 50 Hz). Success in fabrication of long (60–100 m) and wide (~120 mm) ribbons, which are made up of low cost elements is promising for mass production of energy efficient high power transformers and motors - Highlights: • Minor addition of C in FeSiBPCu alloy increases amorphous-forming ability. • The FeSiBPCuC alloy exhibits B{sub s} close to Si-steel and Core loss lower than it. • Excellent soft magnetic properties were obtained for 120 mm wide ribbons. • Nanocrystalline FeSiBPCuC alloy can be produced at industrial scale with low cost. • The alloy is suitable for making low energy loss power transformers and motors.

  4. Improving Magnet Designs With High and Low Field Regions

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Smith, Anders

    2011-01-01

    A general scheme for increasing the difference in magnetic flux density between a high and a low magnetic field region by removing unnecessary magnet material is presented. This is important in, e.g., magnetic refrigeration where magnet arrays have to deliver high field regions in close proximity...... to low field regions. Also, a general way to replace magnet material with a high permeability soft magnetic material where appropriate is discussed. As an example, these schemes are applied to a two dimensional concentric Halbach cylinder design resulting in a reduction of the amount of magnet material...

  5. Effects of minor Sn addition on the glass formation and properties of Fe-metalloid metallic glasses with high magnetization and high glass forming ability

    Science.gov (United States)

    Shi, Minjie; Liu, Zengqian; Zhang, Tao

    2015-03-01

    Effects of minor Sn addition on the glass-forming ability (GFA) as well as thermal, magnetic, and mechanical properties of Fe-P-C-B-Si bulk metallic glasses (BMGs) with compositions of Fe80-xSnxP9C8B2Si1 (x=0, 1, 2 and 3 at%) were investigated. The minor Sn substitution for Fe effectively enhances the GFA. The fully glassy rods can be produced up to 3 and 3.5 mm in diameter for the alloys with 1 and 2 at% Sn addition, respectively. Moreover, these Sn-containing BMGs exhibit good soft magnetic properties including high saturation magnetization (Ms) of 1.46-1.51 T, low coercivity (Hc) of 3.8-5.0 A/m and good mechanical properties, i.e., high fracture strength (σf) above 3.2 GPa and limited plastic strain (εp) above 0.4%. The combination of large GFA, good soft magnetic and mechanical properties as well as low cost makes the Fe-Sn-P-C-B-Si BMGs promising as soft magnetic materials for industrial applications.

  6. Coercion in mental healthcare: the principle of least coercive care.

    Science.gov (United States)

    O'Brien, A J; Golding, C G

    2003-04-01

    Coercive practices are relatively common in mental healthcare, but coercion is ethically problematic because it involves acting against an individual's autonomy. However, coercion is often poorly defined in mental health literature, resulting in problems in considering coercion from an ethical perspective. This paper challenges the traditional paternalistic justification for coercive practices in mental healthcare, and argues that the failure to make a conceptual distinction between what counts as coercive practice and what justifies coercive practice results in instances of unjustified use of coercion. It also results in the failure to recognize other justifications for coercive practice. We propose a broad definition of coercion that recognizes the prevalence of coercion in mental healthcare. In particular, we wish to recognize the potential for persuasion and manipulation of clients' wishes to be coercive. We argue that there should be a prima facie ban on coercion in mental healthcare, and that the use of coercive practices needs to be justified in the specific circumstances of each case. The presupposition that mental illness involves limited autonomy cannot be taken to justify use of coercion. We outline a principle of least coercive intervention that we think has the potential to lessen the prevalence and extent of coercion in mental healthcare.

  7. Magnetic and levitation characteristics of bulk high-temperature superconducting magnets above a permanent magnet guideway

    Science.gov (United States)

    Zheng, Jun; Zheng, Botian; He, Dabo; Sun, Ruixue; Deng, Zigang; Xu, Xun; Dou, Shixue

    2016-09-01

    Due to the large levitation force or the large guidance force of bulk high-temperature superconducting magnets (BHTSMs) above a permanent magnet guideway (PMG), it is reasonable to employ pre-magnetized BHTSMs to replace applied-magnetic-field-cooled superconductors in a maglev system. There are two combination modes between the BHTSM and the PMG, distinguished by the different directions of the magnetization. One is the S-S pole mode, and the other is the S-N pole mode combined with a unimodal PMG segment. A multi-point magnetic field measurement platform was employed to acquire the magnetic field signals of the BHTSM surface in real time during the pre-magnetization process and the re-magnetization process. Subsequently, three experimental aspects of levitation, including the vertical movement due to the levitation force, the lateral movement due to the guidance force, and the force relaxation with time, were explored above the PMG segment. Moreover, finite element modeling by COMSOL Multiphysics has been performed to simulate the different induced currents and the potentially different temperature rises with different modes inside the BHTSM. It was found that the S-S pole mode produced higher induced current density and a higher temperature rise inside the BHTSM, which might escalate its lateral instability above the PMG. The S-N pole mode exhibits the opposite characteristics. In general, this work is instructive for understanding and connecting the magnetic flux, the inner current density, the levitation behavior, and the temperature rise of BHTSMs employed in a maglev system.

  8. Magnetic properties of magnetic glass-like carbon prepared from furan resin alloyed with magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Kazumasa, E-mail: naka@sss.fukushima-u.ac.jp [Materials Science Area, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296 (Japan); Okuyama, Kyoko [Materials Science Area, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296 (Japan); Takase, Tsugiko [Institute of Environmental Radioactivity (IER), Fukushima University, 1 Kanayagawa, Fukushima 960-1296 (Japan)

    2017-03-01

    Magnetic glass-like carbons that were heat-treated at different temperatures or were filled with different magnetic nanoparticle contents were prepared from furan resin alloyed with magnetic fluid (MF) or Fe{sub 3}O{sub 4} powder in their liquid-phase states during mixing. Compared to the Fe{sub 3}O{sub 4} powder-alloyed carbon, the MF-alloyed carbon has highly dispersed the nanoparticles, and has the excellent saturation magnetization and coercivity. It is implied that saturation magnetizations are related to changes in the types of phases for the nanoparticles and the relative intensities of X-ray diffraction peaks for iron and iron-containing compounds in the carbons. Additionally, the coercivities are possibly affected by the size and crystallinity of the nanoparticles, the relative amounts of iron, and the existence of amorphous compounds on the carbon surfaces. - Highlights: • Magnetic glass-like carbons were prepared from furan resin alloyed with magnetic fluid. • The nanoparticles of MF-alloyed GLCs were highly dispersed. • MF-alloyed GLCs had excellent magnetic properties compared to powder-alloyed ones. • The magnetic properties changed with treatment temperature and nanoparticle content. • The changes in magnetic properties were investigated with XRD and FE-SEM.

  9. Coercive Sexual Experiences, Protective Behavioral Strategies, Alcohol Expectancies and Consumption among Male and Female College Students

    Science.gov (United States)

    Palmer, Rebekka S.; McMahon, Thomas J.; Rounsaville, Bruce J.; Ball, Samuel A.

    2010-01-01

    Alcohol use and sexual assault on college campuses are highly prevalent and the focus of numerous prevention and intervention efforts. Our goals were to gain a greater understanding of the relationship between coercive sexual experiences, utilization of protective behavioral strategies and alcohol expectancies and consumption among male and female…

  10. High magnetic field ohmically decoupled non-contact technology

    Science.gov (United States)

    Wilgen, John [Oak Ridge, TN; Kisner, Roger [Knoxville, TN; Ludtka, Gerard [Oak Ridge, TN; Ludtka, Gail [Oak Ridge, TN; Jaramillo, Roger [Knoxville, TN

    2009-05-19

    Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.

  11. Permanent magnet design for high-speed superconducting bearings

    Science.gov (United States)

    Hull, John R.; Uherka, Kenneth L.; Abdoud, Robert G.

    1996-01-01

    A high temperature superconducting bearing including a permanent magnet rotor levitated by a high temperature superconducting structure. The rotor preferably includes one or more concentric permanent magnet rings coupled to permanent magnet ring structures having substantially triangular and quadrangular cross-sections. Both alternating and single direction polarity magnet structures can be used in the bearing.

  12. Synthesis, characterization, and magnetic properties of ZnO-ZnFe2O4 nanoparticles with high photocatalytic activity

    Science.gov (United States)

    Falak, P.; Hassanzadeh-Tabrizi, S. A.; Saffar-Teluri, A.

    2017-11-01

    In the present research, a magnetic ZnO-ZnFe2O4 binary nanocomposite was synthesized by a one-step microemulsion method. The characteristics of the synthesized powders were characterized using various analytical instruments including X-ray diffraction, scanning electron microscope, transmission electron microscope, thermogravimetric and differential thermal analysis, vibrating sample magnetometer, and ultraviolet-visible spectroscopy. The results of transmission electron microscope proved that the synthesized nanoparticles have irregular morphologies and the average particle size is about 20 nm. The photocatalytic investigation of ZnO-ZnFe2O4 nanoparticles was carried out using methylene blue solution under UV light. The synthesized nanoparticles showed enhanced photocatalytic performance in comparison with the ZnO nanoparticles more than 40%. The magnetization saturation value of ZnO-ZnFe2O4 nanoparticles was about 5.8 emu/g, which was high enough to be magnetically removed by applying a magnetic field. The results showed that the magnetization and coercivity of the samples reduced by increasing calcination temperature.

  13. Investigations on the Magnetic Properties of High-Coercivity (Nd(1-x)Fe(x))90Al10 Bulk Amorphous Alloys

    Science.gov (United States)

    2001-04-01

    0.3 -..... 0.1 0.0 -600 -400 -200 0 200 400 600 Applied Field (kA/m) Figure 2. M-H hysteresis loops of Ndso.)- FeAl 11 melt-spun ribbons 25 and...900 600 700 800 900 Temperature (K) Temperature (K) Figure 1. DSC curves plotted for Nde0_xFexAlt0 melt-spun ribbons and cast rods as a function of...their thickness and preparation techniques. In figure 2 are presented comparatively the hysteresis loops as a function of the Fe content for 3 diffcrent

  14. Dynamic nuclear polarization at high magnetic fields.

    Science.gov (United States)

    Maly, Thorsten; Debelouchina, Galia T; Bajaj, Vikram S; Hu, Kan-Nian; Joo, Chan-Gyu; Mak-Jurkauskas, Melody L; Sirigiri, Jagadishwar R; van der Wel, Patrick C A; Herzfeld, Judith; Temkin, Richard J; Griffin, Robert G

    2008-02-07

    Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (microw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (gamma(e)gamma(l)), being approximately 660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (> or =5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms-the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in microw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.

  15. Magnetic field distribution of strong hybrid magnet in high torque motor

    Science.gov (United States)

    Oguri, Kazuya; Mizutani, Akihiro; Ogino, Sanshiroh; Ochiai, Yasuzumi; Kawahata, Masahiro; Nishi, Yoshitake

    2002-11-01

    A variable reluctance hybrid magnet has been developed to apply new type of high torque motors. A permanent magnet, electromagnet and yoke construct the variable reluctance hybrid magnet. From an engineering point of view, it is important to know the magnetic field around a variable reluctance hybrid magnet. Based on the results of magnetic flux density measurement around the hybrid variable reluctance magnet, the high magnetic flux density was found at edges and joints. The high magnetic flux density was also obtained with electrical current of 10 A at optimum setting form. Therefore, we concluded that the strong force of rotor of the hybrid motor was generated by high surface flux density of the hybrid magnet.

  16. Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

    Science.gov (United States)

    Sugimura, K.; Miyajima, Y.; Sonehara, M.; Sato, T.; Hayashi, F.; Zettsu, N.; Teshima, K.; Mizusaki, H.

    2016-05-01

    This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO2) was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC2H5)4). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.

  17. Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

    Directory of Open Access Journals (Sweden)

    K. Sugimura

    2016-05-01

    Full Text Available This study focuses on the carbonyl-iron powder (CIP used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO2 was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC2H54. Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.

  18. Effect of the template-assisted electrodeposition parameters on the structure and magnetic properties of Co nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Kac, Malgorzata, E-mail: malgorzata.kac@ifj.edu.pl [Institute of Nuclear Physics Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow (Poland); Zarzycki, Arkadiusz [Institute of Nuclear Physics Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow (Poland); Kac, Slawomir [AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Krakow (Poland); Kopec, Marek; Perzanowski, Marcin; Dutkiewicz, Erazm M.; Suchanek, Katarzyna; Maximenko, Alexey; Marszalek, Marta [Institute of Nuclear Physics Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow (Poland)

    2016-09-15

    Highlights: • Magnetic properties of Co nanowires in polycarbonate membranes were studied. • Electrodeposition stages were illustrated by SEM images. • Electrolyte and membrane parameters were optimized for Co nanowire fabrication. • Low temperature and potential favored nanowires with high coercivity and squareness. - Abstract: We studied the magnetic properties of Co nanowires electrodeposited in polycarbonate membranes as a function of the electrodeposition and template parameters. We showed the response of the current as a function of time, for nanowires prepared in various conditions. X-ray diffraction measurements indicate that nanowires have polycrystalline hcp structure with small addition of fcc phase. Magnetic properties analyzed by SQUID measurements suggest that easy axis of magnetization follows the nanowire axis with coercivity increasing with a decrease of nanowire diameter and length. The largest coercivity, equal to 850 Oe, was obtained for nanowires with the diameter of 30 nm and the length of 1.5 μm. We find the coercivity to be insensitive to pH value. Low electrodeposition temperature, low cathodic potential, and medium pH are the synthesis parameters most beneficial for large coercivity and/or magnetic anisotropy with easy axis along nanowires.

  19. Magnetic matrices used in high gradient magnetic separation (HGMS: A review

    Directory of Open Access Journals (Sweden)

    Wei Ge

    Full Text Available HGMS is effective in separating or filtering fine and weakly magnetic particles and widely applied in mineral processing, water treatment, cell and protein purification. The magnetic matrix is a crucial device used in magnetic separator to generate high magnetic field gradient and provide surface sites for capturing magnetic particles. The material, geometry, size and arrangement of the matrix elements can significantly affect the gradient and distribution of the magnetic field, and the separating or filtrating performance. In this paper, the researches and developments of magnetic matrices used in HGMS are reviewed. Keywords: Magnetic matrix, HGMS, Review

  20. 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.

  1. Coercive Tactics and Web Advertising Performance

    Directory of Open Access Journals (Sweden)

    Jiwon Lee

    2017-07-01

    Full Text Available By questioning contemporary coercive or intrusive web advertising activities, this study sheds light on the recent conditions of web advertising by focusing on a comprehensive process that leads to web ad performance. A total of 400 questionnaires were distributed by the principal investigators of this study. 170 were returned from 200 distributed questionnaires given in South Korea and 100 were returned from 200 distributed questionnaires in China. The responses total 248 out of 400 distributed questionnaires. The relationships among the measured factors are analyzed by the structural equation modeling method. Results show that the use of web ad tactics often leads to negative consequences, creating a user present avoidance behavior condition towards both the ad and ad-hosting website. In terms of the performance of the ad-hosting website, website retention was strongly influenced by content blocking. In addition, the results of the comparative test suggest that the influence of avoidance on advertising performance is stronger among users of newspaper websites than e-commerce websites.

  2. Spontaneous magnetization in high-density quark matter

    DEFF Research Database (Denmark)

    Tsue, Yasuhiko; da Providência, João; Providência, Constanca

    2015-01-01

    It is shown that spontaneous magnetization occurs due to the anomalous magnetic moments of quarks in high-density quark matter under the tensor-type four-point interaction. The spin polarized condensate for each flavor of quark appears at high baryon density, which leads to the spontaneous...... magnetization due to the anomalous magnetic moments of quarks. The implications for the strong magnetic field in compact stars is discussed....

  3. High Radiation Environment Nuclear Fragment Separator Magnet

    Energy Technology Data Exchange (ETDEWEB)

    Kahn, Stephen [Muons, Inc., Batavia, IL (United States); Gupta, Ramesh [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-01-31

    Superconducting coils wound with HTS conductor can be used in magnets located in a high radiation environment. NbTi and Nb3Sn superconductors must operate at 4.5 K or below where removal of heat is less efficient. The HTS conductor can carry significant current at higher temperatures where the Carnot efficiency is significantly more favorable and where the coolant heat capacity is much larger. Using the HTS conductor the magnet can be operated at 40 K. This project examines the use of HTS conductor for the Michigan State University Facility For Rare Isotope Beams (FRIB) fragment separator dipole magnet which bends the beam by 30° and is located in a high radiation region that will not be easily accessible. Two of these magnets are needed to select the chosen isotope. There are a number of technical challenges to be addressed in the design of this magnet. The separator dipole is 2 m long and subtends a large angle. The magnet should keep a constant transverse field profile along its beam reference path. Winding coils with a curved inner segment is difficult as the conductor will tend to unwind during the process. In the Phase I project two approaches to winding the conductor were examined. The first was to wind the coils with curved sections on the inner and outer segments with the inner segment wound with negative curvature. The alternate approach was to use a straight segment on the inner segment to avoid negative curvature. In Phase I coils with a limited number of turns were successfully wound and tested at 77 K for both coil configurations. The Phase II program concentrated on the design, coil winding procedures, structural analysis, prototyping and testing of an HTS curved dipole coil at 40 K with a heat load representative of the radiation environment. One of the key criteria of the design of this magnet is to avoid the use of organic materials that would degrade rapidly in radiation. The Lorentz forces expected from the coils interacting with the

  4. Coercive sexual experiences, protective behavioral strategies, alcohol expectancies and consumption among male and female college students.

    Science.gov (United States)

    Palmer, Rebekka S; McMahon, Thomas J; Rounsaville, Bruce J; Ball, Samuel A

    2010-09-01

    Alcohol use and sexual assault on college campuses are highly prevalent and the focus of numerous prevention and intervention efforts. Our goals were to gain a greater understanding of the relationship between coercive sexual experiences, utilization of protective behavioral strategies and alcohol expectancies and consumption among male and female college students. We surveyed 370 college students regarding their past year experiences and found that 34% of women and 31% of men reported unwanted sexual contact, 6% of women and 13% of men reported engaging in sexually coercive behavior, and 4% of women and 9% of men reported experiencing both unwanted contact and engaging in sexually coercive behavior. Findings indicated students who experienced unwanted sexual contact reported significant differences in alcohol expectancies. More specifically, those who engaged in sexually coercive behaviors had significantly higher sex-related alcohol expectancies. In addition, recipients of unwanted contact reported higher alcohol consumption, used fewer protective strategies when drinking, and experienced more negative consequences due to their alcohol use. Results suggest that campus alcohol and sexual assault prevention efforts should include information on alcohol expectancies and use of protective strategies.

  5. Crystallization behavior and magnetic properties in High Fe content FeBCSiCu alloy system

    Energy Technology Data Exchange (ETDEWEB)

    Fan, X.D., E-mail: fanxd@seu.edu.cn; Shen, B.L., E-mail: blshen@seu.edu.cn

    2015-07-01

    High Fe content FeBCSiCu nanocrystalline alloys are prepared by annealing melt-spun amorphous ribbons with aim at increasing saturation magnetic flux density. Microstructures identified by XRD and TEM reveal that Cu addition inhibits the surface crystallization of Fe{sub 86}B{sub 7}C{sub 7} alloy and improve its glass-forming ability. Activation energy of crystallization calculated by Kissinger's equation indicates that both Cu and Si addition promotes the precipitation of α-Fe phase and improves the thermal stability. VSM and DC B–H loop tracer measurements show that the Fe{sub 85.5}B{sub 7}C{sub 6}Si{sub 1}Cu{sub 0.5} nanocrystalline alloy exhibits high saturation magnetic flux density of 1.8 T and low coercivity of 10 A/m, respectively. AC properties measured by AC B–H analyzer show this alloy exhibits low core loss of 0.35 W/kg at 1 T at 50 Hz. Low material cost and convenient productivity make the Fe{sub 85.5}B{sub 7}C{sub 6}Si{sub 1}Cu{sub 0.5} nanocrystalline alloy an economical application in industry. - Highlights: • Cu addition inhibits the surface crystallization and improves the GFA. • The competitive formation of Fe{sub 3}C and α-Fe phase impedes the devitrification. • Fe{sub 85.5}B{sub 7}C{sub 6}Si{sub 1}Cu{sub 0.5} nanocrystalline alloy exhibits excellent magnetic properties. • The alloy system has an economical advantage and convenient productivity.

  6. A permanent magnet device for producing variable high magnetic field in three dimensions

    CERN Document Server

    Hwang, C S; Chang, P C; Chen, H H; Chang, C H; Huang Ming Hsiung

    2000-01-01

    By combining four parallel rows of permanent magnet blocks, a magnet device that can produce variable high magnetic field in three dimensions has been designed. In this device, the magnetic field direction and strength can be varied by shifting the four rows along their longitudinal direction and by varying the magnet gap between the top and bottom rows. With a magnet gap of 10 mm, the magnetic field strength at the center of the device is about 1.4 T along the longitudinal and two transverse directions. This device can be utilized in X-ray magnetic circular dichroism and X-ray magnetic linear dichroism experiments as well as in other applications where a variable high magnetic field in three dimensions is needed.

  7. Hybrid Superconducting Magnetic Bearing (HSMB) for high load devices

    Science.gov (United States)

    Mcmichael, C. K.; Ma, K. B.; Lamb, M. A.; Lin, M. W.; Chow, L.; Meng, R. L.; Hor, P. H.; Chu, W. K.

    1992-01-01

    Lifting capacities greater than 41 N/cm(exp 2) (60 psi) at 77 K have been achieved with a new type of levitation (hybrid) using a combination of permanent magnets and high quality melt-mixtured YBa2Cu3O(7-delta) (YBCO). The key concept of the hybrid superconducting magnetic bearing (HSMB) is the use of strong magnetic repulsion and attraction from permanent magnets for high levitation or suspension forces in conjunction with a superconductor's flux pinning characteristics to counteract the inherent instabilities in a system consisting of magnets only. To illustrate this concept, radial and axial forces between magnet/superconductor, magnet/magnet, and magnet/superconductor/magnet, were measured and compared for the thrust bearing configuration

  8. Intimate partner violence, coercive control, and child adjustment problems.

    Science.gov (United States)

    Jouriles, Ernest N; McDonald, Renee

    2015-02-01

    Coercive control is a relationship dynamic that is theorized to be key for understanding physical intimate partner violence (IPV). This research examines how coercive control in the context of physical IPV may influence child adjustment. Participants were 107 mothers and their children, aged 7 to 10 years. In each family, mothers reported the occurrence of at least one act of physical IPV in the past 6 months. Mothers reported on physical IPV and coercive control, and mothers and children reported on children's externalizing and internalizing problems. Coercive control in the context of physical IPV related positively with both mothers' and children's reports of child externalizing and internalizing problems, after accounting for the frequency of physical IPV, psychological abuse, and mothers' education. This research suggests that couple relationship dynamics underlying physical IPV are potentially important for understanding how physical IPV leads to child adjustment problems. © The Author(s) 2014.

  9. Give peace a chance: First, try coercive diplomacy

    National Research Council Canada - National Science Library

    William S Langenheim

    2002-01-01

      "Coercive diplomacy"--a range of nonmilitary options for increasing the pressure on a recalcitrant state, with credible force in the wings--is at this juncture a better option for the United States...

  10. Coercive Diplomacy: Countering War-Threatening Crises and Armed Conflicts

    DEFF Research Database (Denmark)

    Jakobsen, Peter Viggo

    2015-01-01

    Nowadays states rarely resort to war to defeat each other or to address war-threatening crises and armed conflicts. Instead, coercive diplomacy has emerged as their strategy of choice when persuasion and other non-military instruments fall short. Coercive diplomacy involves the use of military...... threats and/or limited force (sticks) coupled with inducements and assurances (carrots) in order to influence the opponent to do something it would prefer not to. States use coercive diplomacy in the hope of achieving their objectives without having to resort to full-scale war. This chapter presents...... the strategy of coercive diplomacy and its requirements for success and shows how states have employed it to manage crises and conflicts during the three strategic eras that the world has passed through since the end of the Cold War....

  11. Mitigated-force carriage for high magnetic field environments

    Science.gov (United States)

    Ludtka, Gerard M.; Ludtka, Gail M.; Wilgen, John B.; Murphy, Bart L.

    2015-05-19

    A carriage for high magnetic field environments includes a plurality of work-piece separators disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla for supporting and separating a plurality of work-pieces by a preselected, essentially equal spacing, so that, as a first work-piece is inserted into the magnetic field, a second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

  12. Tuning Ce distribution for high performanced Nd-Ce-Fe-B sintered magnets

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xiaodong [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China); Guo, Shuai; Chen, Kan; Chen, Renjie; Lee, Don [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China); You, Caiyin, E-mail: caiyinyou@xaut.edu.cn [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Yan, Aru, E-mail: aruyan@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China)

    2016-12-01

    A dual-alloy method was applied to tune the distribution of Ce for enhancing the performance of Nd-Ce-Fe-B sintered magnets with a nominal composition of (Nd{sub 0.75}Ce{sub 0.25}){sub 30.5}Fe{sub bal}Al{sub 0.1}Cu{sub 0.1}B. In comparison to the single alloy of (Nd{sub 0.75}Ce{sub 0.25}){sub 30.5}Fe{sub bal}Al{sub 0.1}Cu{sub 0.1}B, the coercivity was enhanced from 10.3 kOe to 12.1 kOe and the remanence was increased from 13.1 kG to 13.3 kG for the magnets with a dual-alloy method. In addition, the remanence temperature coefficient α and coercivity temperature coefficient β were also slightly improved for the magnet with the dual alloys. The results of microstructure characterizations show the uniform distribution of Ce for the magnet with a single alloy, and the coexistence of the Ce-rich and Ce-lean regions for the magnet with the dual alloys. In combinations with the nucleation of reversal domains and magnetic recoil curves, the property enhancement of magnets with a dual-alloy method was well explained. - Highlights: • Improved magnetic properties were obtained in dual-alloy magnet. • This is due to the tuning of Ce distribution and the change in microstructure. • The magnetic hardening effect can be observed in dual-alloy magnet.

  13. High performance hybrid magnetic structure for biotechnology applications

    Science.gov (United States)

    Humphries, David E [El Cerrito, CA; Pollard, Martin J [El Cerrito, CA; Elkin, Christopher J [San Ramon, CA

    2009-02-03

    The present disclosure provides a high performance hybrid magnetic structure made from a combination of permanent magnets and ferromagnetic pole materials which are assembled in a predetermined array. The hybrid magnetic structure provides means for separation and other biotechnology applications involving holding, manipulation, or separation of magnetic or magnetizable molecular structures and targets. Also disclosed are further improvements to aspects of the hybrid magnetic structure, including additional elements and for adapting the use of the hybrid magnetic structure for use in biotechnology and high throughput processes.

  14. Magnetic properties and thermal stability of Co/HfN multilayer films for high-frequency application

    Directory of Open Access Journals (Sweden)

    Y. Cao

    2017-06-01

    Full Text Available Sputtered metal–nonmetal granular films tend to exhibit growth-induced perpendicular magnetic anisotropy. In this work, Co/HfN multilayers were synthesized to suppress the development of columnar clusters along the deposition direction. The results reveal that a HfN interlayer thickness of less than 0.4 nm is insufficient to separate the columnar clusters; however, increasing the interlayer thickness to 0.8 nm with increasing the sputtering duration successfully led to typical in-plane magnetic anisotropy with a coercivity as low as 3 Oe. The Co(4 nm/HfN(1.5 nm multilayers exhibited high permeability of approximately 260 up to 1.6 GHz. The resonance frequency increased from 1.8 to 2.3 GHz with increasing annealing temperature, which is attributed to the increased magnetic anisotropy. Our results suggest that the multilayers still show high-frequency performance even after annealing at 450 °C, which would be a big advantage for complementary metal–oxide–semiconductor (CMOS fabrication technology.

  15. High-temperature soft magnetic properties of antiperovskite nitrides ZnNFe3 and AlNFe3

    Science.gov (United States)

    Fu, Yankun; Lin, Shuai; Wang, Bosen

    2015-03-01

    We report the synthesis, crystal structure, magnetic and electrical/thermal transport properties of antiperovskite nitrides ZnNFe3 and AlNFe3. Both compounds display ferromagnetic (FM) ground state and transform into the paramagnetic phase at 762 K and 770 K, respectively. At FM phase, for ZnNFe3 and AlNFe3, the saturated magnetizations at 5 K are 163 and 188 emu/g, which is the largest value among all the antiperovskite compounds; the minimal coercive forces (HC) are as low as 18.6 and 16.3 Oe; the low HC is almost constant covering a broad temperature range of 5-650 K. These characteristics indicate that both ZnNFe3 and AlNFe3 may be promising candidates of high-temperature soft magnetic material. In addition, electrons are dominant carriers owing to the negative Seebeck coefficient, the Fermi-liquid behavior is well presented via the investigation of low-temperature electrical transport, and the lattice thermal conductivity estimated by Wiedemann-Franz law is the main part of total thermal conductivity at high temperatures for both ZnNFe3 and AlNFe3.

  16. Alignment of molecular materials in high magnetic fields

    NARCIS (Netherlands)

    Christianen, P.C.M.; Shklyarevskiy, O.I.; Boamfa, M.I.; Maan, J.C.

    2004-01-01

    The potential of using high magnetic fields to align functional molecular materials is discussed, illustrated by magnetic orientation of two different types of materials. Alignment of side chain polymer liquid crystals leads to macroscopically ordered, transparant and strongly birefringent material.

  17. Enhanced Energy Density in Permanent Magnets using Controlled High Magnetic Field during Processing

    Energy Technology Data Exchange (ETDEWEB)

    Carter, William G [ORNL; Rios, Orlando [ORNL; Constantinides, Steven [ORNL

    2016-05-05

    This ORNL Manufacturing Demonstraction Facility (MDF) technical collaboration focused on the use of high magnetic field processing (>2Tesla) using energy efficient large bore superconducting magnet technology and high frequency electromagnetics to improve magnet performance and reduce the energy budget associated with Alnico thermal processing. Alnico, alloys containing Al, Ni, Co and Fe, represent a class of functional nanostructured alloys, and show the greatest potential for supplementing or replacing commercial Nd-based rare-earth alloy magnets.

  18. Development and operation of a Pr_{2}Fe_{14}B based cryogenic permanent magnet undulator for a high spatial resolution x-ray beam line

    Directory of Open Access Journals (Sweden)

    C. Benabderrahmane

    2017-03-01

    Full Text Available Short period, high field undulators are used to produce hard x-rays on synchrotron radiation based storage ring facilities of intermediate energy and enable short wavelength free electron laser. Cryogenic permanent magnet undulators take benefit from improved magnetic properties of RE_{2}Fe_{14}B (Rare Earth based magnets at low temperatures for achieving short period, high magnetic field and high coercivity. Using Pr_{2}Fe_{14}B instead of Nd_{2}Fe_{14}B, which is generally employed for undulators, avoids the limitation caused by the spin reorientation transition phenomenon, and simplifies the cooling system by allowing the working temperature of the undulator to be directly at the liquid nitrogen one (77 K. We describe here the development of a full scale (2 m, 18 mm period Pr_{2}Fe_{14}B cryogenic permanent magnet undulator (U18. The design, construction and optimization, as well as magnetic measurements and shimming at low temperature are presented. The commissioning and operation of the undulator with the electron beam and spectrum measurement using the Nanoscopmium beamline at SOLEIL are also reported.

  19. Levitation performance of the magnetized bulk high- Tc superconducting magnet with different trapped fields

    Science.gov (United States)

    Liu, W.; Wang, J. S.; Liao, X. L.; Zheng, S. J.; Ma, G. T.; Zheng, J.; Wang, S. Y.

    2011-03-01

    To a high- Tc superconducting (HTS) maglev system which needs large levitation force density, the magnetized bulk high- Tc superconductor (HTSC) magnet is a good candidate because it can supply additional repulsive or attractive force above a permanent magnet guideway (PMG). Because the induced supercurrent within a magnetized bulk HTSC is the key parameter for the levitation performance, and it is sensitive to the magnetizing process and field, so the magnetized bulk HTSC magnets with different magnetizing processes had various levitation performances, not only the force magnitude, but also its force relaxation characteristics. Furthermore, the distribution and configuration of the induced supercurrent are also important factor to decide the levitation performance, especially the force relaxation characteristics. This article experimentally investigates the influences of different magnetizing processes and trapped fields on the levitation performance of a magnetized bulk HTSC magnet with smaller size than the magnetic inter-pole distance of PMG, and the obtained results are qualitatively analyzed by the Critical State Model. The test results and analyses of this article are useful for the suitable choice and optimal design of magnetized bulk HTSC magnets.

  20. Oriented nanometric aggregates of partially inverted zinc ferrite: One-step processing and tunable high-frequency magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Sai, Ranajit, E-mail: ranajit@ecei.tohoku.ac.jp [Department of Electrical Engineering, Graduate School of Engineering, Tohoku University, Sendai (Japan); Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore (India); Endo, Yasushi; Shimada, Yutaka; Yamaguchi, Masahiro [Department of Electrical Engineering, Graduate School of Engineering, Tohoku University, Sendai (Japan); Shivashankar, S. A. [Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore (India)

    2015-05-07

    In this work, it is demonstrated that the in situ growth of oriented nanometric aggregates of partially inverted zinc ferrite can potentially pave a way to alter and tune magnetocrystalline anisotropy that, in turn, dictates ferromagnetic resonance frequency (f{sub FMR}) by inducing strain due to aggregation. Furthermore, the influence of interparticle interaction on magnetic properties of the aggregates is investigated. Mono-dispersed zinc ferrite nanoparticles (<5 nm) with various degrees of aggregation were prepared through decomposition of metal-organic compounds of zinc (II) and iron (III) in an alcoholic solution under controlled microwave irradiation, below 200 °C. The nanocrystallites were found to possess high degree of inversion (>0.5). With increasing order of aggregation in the samples, saturation magnetization (at 5 K) is found to decrease from 38 emu/g to 24 emu/g, while coercivity is found to increase gradually by up to 100% (525 Oe to 1040 Oe). Anisotropy-mediated shift of f{sub FMR} has also been measured and discussed. In essence, the result exhibits an easy way to control the magnetic characteristics of nanocrystalline zinc ferrite, boosted with significant degree of inversion, at GHz frequencies.

  1. Magnetic force microscopy of thin film media for high density magnetic recording

    NARCIS (Netherlands)

    Porthun, Steffen; Porthun, S.; Abelmann, Leon; Lodder, J.C.

    1998-01-01

    This paper discusses various aspect of magnetic force microscopy (MFM) for use in the field of high density magnetic recording. After an introduction of the most important magnetic imaging techniques, an overview is given of the operation and theory of MFM. The developments in instrumentation, MFM

  2. Magnetic and Magneto-Optical Properties in Paramagnetic NdF3 Under High Magnetic Field

    Science.gov (United States)

    Wang, Wei; Liu, Gong-Qiang

    2005-05-01

    In this paper, we first theoretically report the magnetic and magneto-optical properties in paramagnetic media under high external magnetic field. Considering the action of the external magnetic field He and indirect exchange interaction Hv, the characteristic of the magnetic saturation and the property of the Faraday rotation to be nonlinear with external magnetic field are presented in paramagnetic NdF3. In terms of our theory, the indirect exchange interaction plays an important role in the magnetization M and the Faraday rotation θ in NdF3 under high external magnetic field. The theory is in good agreement with experimental results. On the other hand, a reasonable explanation for the temperature dependence of the ratio of the Verdet constant to the magnetic susceptibility V/χ is obtained.

  3. [Neurofunctional MRI at high magnetic fields].

    Science.gov (United States)

    Speck, O; Turner, R

    2013-05-01

    Functional magnetic resonance imaging (fMRI) examinations are limited in their sensitivity due to the low activation-induced signal change. Within short tolerable scan times the spatial resolution is thus limited. fMRI is a reliable tool in neuroscience as well as for clinical applications such as presurgical mapping of brain function. The fMRI sensitivity improves greatly (more than linearly) with increasing magnetic field strengths. For many years this was the main driving force in the push towards higher field strengths, such as 7 T. The sensitivity gain is greatest for high spatial resolution and fMRI with very high sub-millimeter resolution becomes feasible. Current results demonstrate that the localization of the blood oxygenation level dependent (BOLD) signal is better than previously assumed. High-field fMRI not only allows quantitative improvements but also opens the way to new information content, such as columnar and layer-dependent functional structures of the cortex. This may pave the way for further information, e.g. the directionality of cortico-cortical connections; however, these possibilities also pose new challenges. New methods for processing such high resolution data are required which do not require spatial smoothing and preserve the high information content. Common spatial resolutions of 2-3 mm are still very well suited for examinations at 3 T where they benefit from the low signal void, lower geometrical distortion and reduced acoustic noise. To achieve higher resolution at 7 T parallel imaging and geometric distortion correction are essential and permit the best congruence with structural data. The echo time at 7 T should be adjusted to about 20-25 ms. Data processing for single subjects or patients should be performed with little or no smoothing to retain resolution. Group studies could achieve good correlation with local normalization. New methods for information extraction, such as multivariate pattern analysis may allow

  4. Probing High Temperature Superconductors with Magnetometry in Ultrahigh Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lu [Univ. of Michigan, Ann Arbor, MI (United States)

    2017-07-26

    The objective of this research is to investigate the high-field magnetic properties of high temperature superconductors, materials that conduct electricity without loss. A technique known as high-resolution torque magnetometry that was developed to directly measure the magnetization of high temperature superconductors. This technique was implemented using the 65 Tesla pulsed magnetic field facility that is part of the National High Magnetic Field Laboratory at Los Alamos National Laboratory. This research addressed unanswered questions about the interplay between magnetism and superconductivity, determine the electronic structure of high temperature superconductors, and shed light on the mechanism of high temperature superconductivity and on potential applications of these materials in areas such as energy generation and power transmission. Further applications of the technology resolve the novel physical phenomena such as correlated topological insulators, and spin liquid state in quantum magnets.

  5. Magnetization and magnetostriction in highly magnetostrictive materials

    Energy Technology Data Exchange (ETDEWEB)

    Thoelke, Jennifer Beth [Iowa State Univ., Ames, IA (United States)

    1993-05-26

    The majority of this research has been in developing a model to describe the magnetostrictive properties of Terfenol-D, Tbsub>1-xDyxFey (x = 0.7-0.75 and y = 1.8--2.0), a rare earth-iron alloy which displays much promise for use in device applications. In the first chapter an introduction is given to the phenomena of magnetization and magnetostriction. The magnetic processes responsible for the observed magnetic properties of materials are explained. An overview is presented of the magnetic properties of rare earths, and more specifically the magnetic properties of Terfenol-D. In the second chapter, experimental results are presented on three composition of Tb< with x = 0.7, y= 1.9, 1.95, and x= 0.73, y= 1.95. The data were taken for various levels of prestress to show the effects of composition and microstructure on the magnetic and magnetostrictive properties of Terfenol-D. In the third chapter, a theoretical model is developed based on the rotation of magnetic domains. The model is used to explain the magnetic and magnetostrictive properties of Terfenol-D, including the observed negative strictions and large change in strain. The fourth chapter goes on to examine the magnetic properties of Terfenol-D along different crystallographic orientations. In the fifth chapter initial data are presented on the time dependence of magnetization in nickel.

  6. Elliptic and weakly coercive systems of operators in Sobolev spaces

    Science.gov (United States)

    Limanskiĭ, D. V.; Malamud, Mark M.

    2008-12-01

    It is known that an elliptic system \\{P_j(x,D)\\}_1^N of order l is weakly coercive in \\overset{\\circ}{W}{}^l_{\\!\\infty}(\\mathbb R^n), that is, all differential monomials of order \\le l-1 on C_0^\\infty(\\mathbb R^n)-functions are subordinated to this system in the L^\\infty-norm. Conditions for the converse result are found and other properties of weakly coercive systems are investigated. An analogue of the de Leeuw-Mirkil theorem is obtained for operators with variable coefficients: it is shown that an operator P(x,D) of n\\ge 3 variables with constant principal part is weakly coercive in \\overset{\\circ}{W}{}^l_{\\!\\infty}(\\mathbb R^n) if and only if it is elliptic. A similar result is obtained for systems \\{P_j(D)\\}_1^N with constant coefficients under the condition n\\ge 2N+1 and with several restrictions on the symbols P_j(\\xi). A complete description of differential polynomials of two variables which are weakly coercive in \\overset{\\circ}{W}{}^l_{\\!\\infty}(\\mathbb R^2) is given. Wide classes of systems with constant coefficients which are weakly coercive in \\overset{\\circ}{W}{}^l_{\\!\\infty}(\\mathbb R^n), but non-elliptic are constructed. Bibliography: 32 titles.

  7. Rapid Solidification of Magnetic Oxides

    Science.gov (United States)

    Kalonji, G.; Deguire, M. R.

    1985-01-01

    The enhanced control over microstructural evolution inherent in rapid solidification processing techniques are exploited to create novel ceramic magnetic materials. The great sensitivity of magnetic properties to local structure provides a powerful probe both for the study of structure and of microscopic solidification mechanisms. The first system studied is the SrO-Fe2O3 binary, which contains the commercially important hard magnetic compound strontium hexaferrite. The products were analyzed by transmission electron microscopy, Mossbauer spectroscopy, magnetic measurements, and differential thermal analysis. As-quenched ribbons contain high concentrations of super-paramagnetic particles, 80 to 250 Angstroms in diameter, in a glassy matrix. This suggests the possibility of crystallizing monodomain strontium hexaferrite during subsequent heat treatment, with a resulting increase in coercivity over conventionally processed ferrite magnets. That magnetic properties can be controlled in solidification processing by varying the quench rate is demonstrated.

  8. Magnetic field effect in highly pure, highly fluorescent conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Graupner, W.; Sacher, M.; Graupner, M.; Zenz, C.; Grampp, G.; Hermetter, A.; Leising, G.

    1998-07-01

    The authors report on the magnetic field effect (MFE) on the photoluminescence in films of a highly fluorescent conjugated laddertype poly(paraphenylene) (LPPP). They observe no MFE for the pure material, however, the introduction of a very small content of chemical defects via photo-oxidation leads to a MFE proportional to the amount of defects. The chemically induced increase in MFE is correlated with a change in other properties of the LPPP films, such as photoluminescence emission and excitation spectra, transient photoluminescence and infrared spectra.

  9. Reducing Magnetic Noise of an Unmanned Aerial Vehicle for High-Quality Magnetic Surveys

    Directory of Open Access Journals (Sweden)

    Boris Sterligov

    2016-01-01

    Full Text Available The use of light and ultralight unmanned aerial vehicles (UAVs for magnetic data acquisition can be efficient for resolving multiple geological and engineering tasks including geological mapping, ore deposits’ prospecting, and pipelines’ monitoring. The accuracy of the aeromagnetic data acquired using UAV depends mainly on deviation noise of electric devices (engine, servos, etc.. The goal of this research is to develop a nonmagnetic unmanned aerial platform (NUAP for high-quality magnetic surveys. Considering parameters of regional and local magnetic survey, a fixed-wing UAV suits geological tasks better for plain area and copter type for hills and mountains. Analysis of the experimental magnetic anomalies produced by a serial light fixed-wing UAV and subsequent magnetic and aerodynamic modeling demonstrates a capacity of NUAP with internal combustion engine carrying an atomic magnetic sensor mounted on the UAV wings to facilitate a high-quality magnetic survey.

  10. The limits of Type D coercive diplomacy in Somalia

    OpenAIRE

    Harrison, John C.

    1995-01-01

    This thesis argues that the U.S./U.N. intervention in Somalia in 1992-1994 represents an attempt to use coercive diplomacy to re-create the Somali state. It further argues that the pre-conditions for a successful use of coercive diplomacy existed initially during the U.S.-led United Task Force (UNITAF) phase, but they quickly disappeared during the expanded mission of United Nations Somalia II (UNOSOM II). This thesis proposes that UNITAF leadership were quite successful in accomplishing thei...

  11. High temperature superconductor cable concepts for fusion magnets

    CERN Document Server

    AUTHOR|(CDS)2078397

    2013-01-01

    Three concepts of high temperature superconductor cables carrying kA currents (RACC, CORC and TSTC) are investigated, optimized and evaluated in the scope of their applicability as conductor in fusion magnets. The magnetic field and temperature dependence of the cables is measured; the thermal expansion and conductivity of structure, insulation and filling materials are investigated. High temperature superconductor winding packs for fusion magnets are calculated and compared with corresponding low temperature superconductor cases.

  12. Magnetic properties of (misch metal, Nd-Fe-B melt-spun magnets

    Directory of Open Access Journals (Sweden)

    R. Li

    2017-05-01

    Full Text Available The effect of replacing Nd with misch metal (MM on magnetic properties and thermal stability has been investigated on melt-spun (Nd1-xMMx13.5Fe79.5B7 ribbons by varying x from 0 to 1. All of the alloys studied crystallize in the tetragonal 2:14:1 structure with single hard magnetic phase. Curie temperature (Tc, coercivity (Hcj, remanence magnetization (Br and maximum energy product ((BHmax all decrease with MM content. The melt-spun MM13.5Fe79.5B ribbons with high ratio of La and Ce exhibit high magnetic properties of Hcj = 8.2 kOe and (BHmax= 10.3 MGOe at room temperature. MM substitution also significantly strengthens the temperature stability of coercivity. The coercivities of the samples with x = 0.2 and even 0.4 exhibit large values close to that of Nd13.5Fe79.5B7 ribbons above 400 K.

  13. Shock melt veins of Tenham chondrite as a possible paleomagnetic recorder: Rock magnetism and high-pressure minerals

    Science.gov (United States)

    Sato, Yugo; Nakamura, Norihiro

    2010-04-01

    Heavily shocked meteorites of shock stages S5 and S6 contain shock-induced melt veins (SMVs). SMVs might have reset the remanence of an asteroidal metamorphism at the time of giant collisions against a chondrite parent body. Here we present micropaleomagnetic and petrologic studies of SMVs in L6S5 Tenham chondrite with ˜500 μm thick black veins enclosing high-pressure minerals such as ringwoodite. Paleomagnetic data show that the high-temperature (HT, 200°C-650°C) and high-coercivity (HC, 20-100 mT) stable components of SMVs formed a cluster even from different portions of SMV, whereas the stable HT component of surrounding host rock showed a scattered orientation under stereonet projection. The host rock HC components form a girdle between the mixing of SMVs and unknown overprints, tracing the magnetic susceptibility foliation. Magnetic force microscopy and backscattered electron images confirmed kamacite and taenite assemblages in iron sulfides as remanence-carrying minerals in SMVs. Hysteresis data of SMVs revealed the presence of single-domain (SD) FeNi metals with Mrs/Ms = ˜0.1 and Hrc/Hc = ˜2, although these parameters are only applicable to magnetite. Because the metastable ringwoodite in SMVs transforms back to olivine at 188°C for 1000 Myr (metamorphism) or at 900°C for 1 h (postshock heating), the preservation of ringwoodite suggests that SMVs have not experienced either thermal condition. The magnetic time-temperature relation for SD FeNi metals suggested that 200°C unblocking temperature corresponds to the storage time of 100 years for kamacite and 4500 Myr for taenite at room temperature. The difference of HT components discards the possibility of postshock heating. Therefore, the SMV's remanence is a characteristic shock-induced thermal remanence that has newly been acquired during hypervelocity collision under a cryptic magnetic field.

  14. Post-assembly magnetization of a 100 kW high speed permanent magnet rotor.

    Science.gov (United States)

    Lv, Yiliang; Wang, Guobin; Li, Liang

    2015-03-01

    A post-assembly magnetizing fixture has been designed and successfully used to magnetize the rotor of a 100 kW high speed permanent magnet synchronous motor. The rotor is a solid cylinder with outer diameter of 80 mm and total length of 515 mm. The permanent magnet material is samarium-cobalt (Sm2Co17) with saturation magnetizing field of 6 T. The mechanical stability of the magnetizing fixture has been studied as well as the general design methodology. The magnetizing coil is subdivided in order to reduce the electromagnetic force, and the coils are separately reinforced in different ways. The electromagnetic and structural optimization is performed by finite element analysis and verified by experiments.

  15. Magnetic properties of α″-Fe16N2-like compound derived from Fe3O4 fine powder coated on hard magnetic BaFe12O19 particles

    Science.gov (United States)

    Tsugawa, Yuta; Matsumoto, Yoshiyuki; Masubuchi, Yuji; Uchikoshi, Tetsuo; Kikkawa, Shinichi

    2017-12-01

    An increase in magnetic coercivity is important for the α″-Fe16N2-like compound with an enhanced magnetization from α-Fe as a new hard magnetic material. In the present study, BaFe12O19 particles were coated with fine Fe3O4 powder produced by hydrolysis of Fe(acac)3 in benzyl alcohol. Smooth magnetization curves were obtained for the composite particles, suggesting they were magnetic hybrids with strong magnetic coupling between the Fe3O4 coating and the BaFe12O19 core particles. The Fe3O4 coating layer was then nitrided by ammonolysis at 150 °C to produce a dual-phase mixture of an α″-Fe16N2-like compound, which we refer to as ;α″-Fe16N2;, and residual α-Fe. Smooth magnetization hysteresis curves were obtained for (;α″-Fe16N2;)0.31(α-Fe)0.69/BaFe12O19 particles, and a magnetic coercivity of 199 mT, compared to the value of just 65 mT for (;α″-Fe16N2;)0.57(α-Fe)0.43 powder, indicating magnetic coupling between the core and shell structures. Thus, the hybrid particles exhibited both high magnetization and coercivity.

  16. Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

    Science.gov (United States)

    Li, Ling; Tirado, Angelica; Nlebedim, I. C.; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R. R.; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A.; Paranthaman, M. Parans

    2016-10-01

    Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.

  17. Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

    Science.gov (United States)

    Li, Ling; Tirado, Angelica; Nlebedim, I. C.; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R. R.; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A.; Paranthaman, M. Parans

    2016-01-01

    Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials. PMID:27796339

  18. Effect of magnetic field inhomogeneity on ion cyclotron motion coherence at high magnetic field.

    Science.gov (United States)

    Vladimirov, Gleb; Kostyukevich, Yury; Hendrickson, Christopher L; Blakney, Greg T; Nikolaev, Eugene

    2015-01-01

    A three-dimensional code based on the particle-in-cell algorithm modified to account for the inhomogeneity of the magnetic field was applied to determine the effect of Z(1), Z(2), Z(3), Z(4), X, Y, ZX, ZY, XZ(2) YZ(2), XY and X(2)-Y(2) components of an orthogonal magnetic field expansion on ion motion during detection in an FT-ICR cell. Simulations were performed for magnetic field strengths of 4.7, 7, 14.5 and 21 Tesla, including experimentally determined magnetic field spatial distributions for existing 4.7 T and 14.5 T magnets. The effect of magnetic field inhomogeneity on ion cloud stabilization ("ion condensation") at high numbers of ions was investigated by direct simulations of individual ion trajectories. Z(1), Z(2), Z(3) and Z(4) components have the largest effect (especially Z(1)) on ion cloud stability. Higher magnetic field strength and lower m/z demand higher relative magnetic field homogeneity to maintain cloud coherence for a fixed time period. The dependence of mass resolving power upper limit on Z(1) inhomogeneity is evaluated for different magnetic fields and m/z. The results serve to set the homogeneity requirements for various orthogonal magnetic field components (shims) for future FT-ICR magnet design.

  19. High Field Magnetization of Tb Single Crystals

    DEFF Research Database (Denmark)

    Roeland, L. W.; Cock, G. J.; Lindgård, Per-Anker

    1975-01-01

    The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenologica...... data on Tb. The conduction-electron polarization at zero field and temperature is (0.33+or-0.05) mu B/ion, and the susceptibility is greater than the Pauli susceptibility calculated from the band-structure.......The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenological...... Hamiltonian including isotropic exchange interactions, effective single-ion anisotropy and magnetoelastic contributions. The parameters of this Hamiltonian were determined by fitting the theoretical results for the spin wave dispersion and energy gap as a function of temperature and magnetic field to existing...

  20. High energy product chemically synthesized exchange coupled Nd2Fe14B/α-Fe magnetic powders.

    Science.gov (United States)

    Parmar, Harshida; Xiao, T; Chaudhary, V; Zhong, Y; Ramanujan, R V

    2017-09-28

    The excellent hard magnetic properties of Nd 2 Fe 14 B based magnets have an enormous range of technological applications. Exchange-coupled Nd 2 Fe 14 B/α-Fe magnets were chemically synthesized by a microwave assisted combustion process to produce mixed oxides, followed by a reduction diffusion process to form magnetic nano-composite powder. This synthesis technique offers an inexpensive and facile platform to produce exchange coupled hard magnets. The size dependent magnetic properties were investigated. The formation mechanisms of the oxide powders and the reduction diffusion mechanism were identified. The microwave power was found to play a crucial role in determining the crystallite size. The coercivity of the powder increased with increasing particle size. Room temperature coercivity (H c ) values greater than 9 kOe and magnetization of 110 emu g -1 was obtained in particles with a mean size of ∼62 nm. An energy product of 5.2 MGOe was obtained, which is the highest reported value for chemically synthesized hard magnetic Nd 2 Fe 14 B/α-Fe powders.

  1. "Coercion Experience Scale" (CES - validation of a questionnaire on coercive measures

    Directory of Open Access Journals (Sweden)

    Flammer Erich

    2010-01-01

    Full Text Available Abstract Background Although the authors of a Cochrane Review on seclusion and mechanical restraint concluded that "there is a surprising and shocking lack of published trials" on coercive interventions in psychiatry, there are only few instruments that can be applied in trials. Furthermore, as main outcome variable safety, psychopathological symptoms, and duration of an intervention cannot meet the demand to indicate subjective suffering and impact relevant to posttraumatic stress syndromes. An instrument used in controlled trials should assess the patients' subjective experiences, needs to be applicable to more than one intervention in order to compare different coercive measures and has to account for the specific psychiatric context. Methods The primary version of the questionnaire comprised 44 items, nine items on restrictions to human rights, developed on a clinical basis, and 35 items on stressors, derived from patients' comments during the pilot phase of the study. An exploratory factor analysis (EFA using principal axis factoring (PAF was carried out. The resulting factors were orthogonally rotated via VARIMAX procedure. Items with factor loadings less than .50 were eliminated. The reliability of the subscales was assessed by calculating Cronbach. Results Data of 102 patients was analysed. The analysis yielded six factors which were entitled "Humiliation", "Physical adverse effects", "Separation", "Negative environment", "Fear" and "Coercion". These six factors explained 54.5% of the total variance. Cronbach alpha ranged from .67 to .93, which can be interpreted as a high internal consistency. Convergent and discriminant validity yielded both highly significant results (r = .79, p Conclusions The "Coercion Experience Scale" is an instrument to measure the psychological impact during psychiatric coercive interventions. Its psychometric properties showed satisfying reliability and validity. For purposes of research it can be used to

  2. High-aspect ratio magnetic nanocomposite polymer cilium

    Science.gov (United States)

    Rahbar, M.; Tseng, H. Y.; Gray, B. L.

    2014-03-01

    This paper presents a new fabrication technique to achieve ultra high-aspect ratio artificial cilia micro-patterned from flexible highly magnetic rare earth nanoparticle-doped polymers. We have developed a simple, inexpensive and scalable fabrication method to create cilia structures that can be actuated by miniature electromagnets, that are suitable to be used for lab-on-a chip (LOC) and micro-total-analysis-system (μ-TAS) applications such as mixers and flow-control elements. The magnetic cilia are fabricated and magnetically polarized directly in microfluidic channels or reaction chambers, allowing for easy integration with complex microfluidic systems. These cilia structures can be combined on a single chip with other microfluidic components employing the same permanently magnetic nano-composite polymer (MNCP), such as valves or pumps. Rare earth permanent magnetic powder, (Nd0.7Ce0.3)10.5Fe83.9B5.6, is used to dope polydimethylsiloxane (PDMS), resulting in a highly flexible M-NCP of much higher magnetization and remanence [1] than ferromagnetic polymers typically employed in magnetic microfluidics. Sacrificial poly(ethylene-glycol) (PEG) is used to mold the highly magnetic polymer into ultra high-aspect ratio artificial cilia. Cilia structures with aspect ratio exceeding 8:0.13 can be easily fabricated using this technique and are actuated using miniature electromagnets to achieve a high range of motion/vibration.

  3. Magnetic structures of erbium under high pressure

    DEFF Research Database (Denmark)

    Kawano, S.; Lebech, B.; Achiwa, N.

    1993-01-01

    Neutron diffraction studies of the magnetic structures of erbium metal at 4.5 K and 11.5 kbar hydrostatic pressure have revealed that the transition to a conical structure at low temperatures is suppressed and that the cycloidal structure, with modulation vector Q congruent-to (2/7 2pi/c)c persists...... between 4.5 K and approximately 50 K, where it tends to increase. The intensities of the magnetic satellites originating from higher-order harmonics of the c-axis-moment component observed at 4.5 K decrease slowly with increasing temperature, but persist up to approximately 60 K....

  4. Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field

    Science.gov (United States)

    Bojarevics, V.; Easter, S.; Pericleous, K.

    2012-01-01

    Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case.

  5. High performance magnetocaloric perovskites for magnetic refrigeration

    DEFF Research Database (Denmark)

    Bahl, Christian R. H.; Velazquez, David; Nielsen, Kaspar K.

    2012-01-01

    We have applied mixed valance manganite perovskites as magnetocaloric materials in a magnetic refrigeration device. Relying on exact control of the composition and a technique to process the materials into single adjoined pieces, we have observed temperature spans above 9 K with two materials...

  6. Dual-stage trapped-flux magnet cryostat for measurements at high magnetic fields

    Science.gov (United States)

    Islam, Zahirul; Das, Ritesh K.; Weinstein, Roy

    2015-04-14

    A method and a dual-stage trapped-flux magnet cryostat apparatus are provided for implementing enhanced measurements at high magnetic fields. The dual-stage trapped-flux magnet cryostat system includes a trapped-flux magnet (TFM). A sample, for example, a single crystal, is adjustably positioned proximate to the surface of the TFM, using a translation stage such that the distance between the sample and the surface is selectively adjusted. A cryostat is provided with a first separate thermal stage provided for cooling the TFM and with a second separate thermal stage provided for cooling sample.

  7. Exchange biased FeNi/FeMn bilayers with coercivity and switching field enhanced by FeMn surface oxidation

    Directory of Open Access Journals (Sweden)

    A. V. Svalov

    2013-09-01

    Full Text Available FeNi/FeMn bilayers were grown in a magnetic field and subjected to heat treatments at temperatures of 50 to 350 °C in vacuum or in a gas mixture containing oxygen. In the as-deposited state, the hysteresis loop of 30 nm FeNi layer was shifted. Low temperature annealing leads to a decrease of the exchange bias field. Heat treatments at higher temperatures in gas mixture result in partial oxidation of 20 nm thick FeMn layer leading to a nonlinear dependence of coercivity and a switching field of FeNi layer on annealing temperature. The maximum of coercivity and switching field were observed after annealing at 300 °C.

  8. Electroplating and characterization of cobalt-nickel-iron and nickel-iron for magnetic microsystems applications

    DEFF Research Database (Denmark)

    Rasmussen, Frank Engel; Ravnkilde, Jan Tue; Tang, Peter Torben

    2001-01-01

    The magnetic properties of pulse reverse (PR) electroplated CoNiFe and DC electroplated NiTe are presented. CoNiFe is a very promising material for magnetic microsystems due to the possibility of achieving a high saturation flux density (B-s) and a low coercivity (H-c). A new bath formulation has...... by comparison to measurements performed with a vibrating sample magnetometer (VSM)....

  9. Magnetic and structural phase transitions of MnBi under high magnetic fields

    Directory of Open Access Journals (Sweden)

    Keiichi Koyama, Yoshifuru Mitsui and Kazuo Watanabe

    2008-01-01

    Full Text Available High-field x-ray diffraction and magnetization measurements and differential thermal analysis (DTA were carried out for polycrystalline MnBi with an NiAs-type hexagonal structure to investigate its magnetic and structural phase transitions. The lattice parameter a rapidly decreases below the spin reorientation temperature TSR(=90 K in a zero magnetic field. The parameter c decreases gradually with decreasing temperature and exhibits an anomaly in the vicinity of TSR. By applying a magnetic field of 5 T, the parameter a increases by ~0.05% when Tmagnetic phase transition temperature from the ferromagnetic state to the paramagnetic state increases linearly at a rate of 2 KT−1 with increasing magnetic field up to 14 T.

  10. Mechanical design of a high field common coil magnet

    CERN Document Server

    Caspi, S; Dietderich, D R; Gourlay, S A; Gupta, R; McInturff, A; Millos, G; Scanlan, R M

    1999-01-01

    A common coil design for high field 2-in-1 accelerator magnets has been previously presented as a "conductor-friendly" option for high field magnets applicable for a Very Large Hadron Collider. This paper presents the mechanical design for a 14 tesla 2-in-1 dipole based on the common coil design approach. The magnet will use a high current density Nb/sub 3/Sn conductor. The design addresses mechanical issues particular to the common coil geometry: horizontal support against coil edges, vertical preload on coil faces, end loading and support, and coil stresses and strains. The magnet is the second in a series of racetrack coil magnets that will provide experimental verification of the common coil design approach. (9 refs).

  11. Mechanical design of a high field common coil magnet

    Energy Technology Data Exchange (ETDEWEB)

    Caspi, S.; Chow, K.; Dietderich, D.; Gourlay, S.; Gupta, R.; McInturff, A.; Millos, G.; Scanlan, R.

    1999-03-18

    A common coil design for high field 2-in-1 accelerator magnets has been previously presented as a 'conductor-friendly' option for high field magnets applicable for a Very Large Hadron Collider. This paper presents the mechanical design for a 14 tesla 2-in-1 dipole based on the common coil design approach. The magnet will use a high current density Nb{sub 3}Sn conductor. The design addresses mechanical issues particular to the common coil geometry: horizontal support against coil edges, vertical preload on coil faces, end loading and support, and coil stresses and strains. The magnet is the second in a series of racetrack coil magnets that will provide experimental verification of the common coil design approach.

  12. Highly sensitive detection of protein biomarkers via nuclear magnetic resonance biosensor with magnetically engineered nanoferrite particles.

    Science.gov (United States)

    Jeun, Minhong; Park, Sungwook; Lee, Hakho; Lee, Kwan Hyi

    Magnetic-based biosensors are attractive for on-site detection of biomarkers due to the low magnetic susceptibility of biological samples. Here, we report a highly sensitive magnetic-based biosensing system that is composed of a miniaturized nuclear magnetic resonance (NMR) device and magnetically engineered nanoferrite particles (NFPs). The sensing performance, also identified as the transverse relaxation (R2) rate, of the NMR device is directly related to the magnetic properties of the NFPs. Therefore, we developed magnetically engineered NFPs (MnMg-NFP) and used them as NMR agents to exhibit a significantly improved R2 rate. The magnetization of the MnMg-NFPs was increased by controlling the Mn and Mg cation concentration and distribution during the synthesis process. This modification of the Mn and Mg cation directly contributed to improving the R2 rate. The miniaturized NMR system, combined with the magnetically engineered MnMg-NFPs, successfully detected a small amount of infectious influenza A H1N1 nucleoprotein with high sensitivity and stability.

  13. The Role of Superconducting Magnets for High Energy Physics

    CERN Document Server

    CERN. Geneva

    2012-01-01

    Superconducting Magnets have played a crucial role for the particle physics energy frontier. From Tevatron to LHC, passing through HERA and RHIC, they have defined the last 30 years of hadron colliders. The talk will review the successful projects and mention the reasons and learning from the ill-fated projects, Isabelle and SSC. Technology spin-off will be discussed, together with the development of the next generation magnets; the high field ones, aimed at passing the 10 Tesla frontier in collider quality magnets, and the fast cycled ones, aimed at enabling field ramp rates of 1 to 4 Tesla per second in synchrotron quality magnets.

  14. A High-Throughput SU-8Microfluidic Magnetic Bead Separator

    DEFF Research Database (Denmark)

    Bu, Minqiang; Christensen, T. B.; Smistrup, Kristian

    2007-01-01

    We present a novel microfluidic magnetic bead separator based on SU-8 fabrication technique for high through-put applications. The experimental results show that magnetic beads can be captured at an efficiency of 91 % and 54 % at flow rates of 1 mL/min and 4 mL/min, respectively. Integration of s...

  15. Conduction cooled high temperature superconducting dipole magnet for accelerator applications

    DEFF Research Database (Denmark)

    Zangenberg, N.; Nielsen, G.; Hauge, N.

    2012-01-01

    A 3T proof-of-principle dipole magnet for accelerator applications, based on 2nd generation high temperature superconducting tape was designed, built, and tested by a consortium under the lead of Danfysik. The magnet was designed to have a straight, circular bore with a good field region of radius...... = 25 mm, and a magnetic length of 250 mm. A total length of 2.5 km YBCO-based copper stabilized conductor supplied by SuperPower Inc., NY, USA, was isolated with 0.025 mm of epoxy and subsequently wound into 14 saddle coils and 4 racetrack coils with a cosine theta like configuration. The coils were......-liquid free operation of an HTS accelerator magnet was demonstrated. The cold mass support design permits magnet orientation under arbitrary angles. Careful choice of materials in terms of magnetic, heat conducting and mechanical properties resulted in a robust and compact solution which opens up...

  16. Magnetostructural transitions in a frustrated magnet at high fields.

    Science.gov (United States)

    Tsurkan, V; Zherlitsyn, S; Felea, V; Yasin, S; Skourski, Yu; Deisenhofer, J; von Nidda, H-A Krug; Lemmens, P; Wosnitza, J; Loidl, A

    2011-06-17

    Ultrasound and magnetization studies of bond-frustrated ZnCr(2)S(4) spinel are performed in static magnetic fields up to 18 T and in pulsed fields up to 62 T. At temperatures below the antiferromagnetic transition at T(N1)≈14  K, the sound velocity as a function of the magnetic field reveals a sequence of steps followed by plateaus indicating a succession of crystallographic structures with constant stiffness. At the same time, the magnetization evolves continuously with a field up to full magnetic polarization without any plateaus in contrast to geometrically frustrated chromium oxide spinels. The observed high-field magnetostructural states are discussed within a H-T phase diagram taking into account the field and temperature evolution of three coexisting spin structures and subsequent lattice transformations induced by the magnetic field.

  17. Structure and coercivity of nanocrystalline Fe–Si–B–Nb–Cu alloys

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 28; Issue 5. Structure and coercivity of ... Keywords. Fe–Si–B–Nb–Cu alloy; melt-spinning; crystallization; nanocrystalline materials; coercivity. ... It is found that the primary phase changes from -Fe(Si) to Fe3Si (DO3) on increasing the Si content. The coercivity of the ...

  18. Magnetic properties of self-assembled Fe nanoislands on BaTiO{sub 3}(001)

    Energy Technology Data Exchange (ETDEWEB)

    Govind, R.K. [Institut für Physik, Naturwissenschaftliche Fakultät II, Martin-Luther-Universität Halle-Wittenberg, von-Danckelmann-Platz 3, D-06099 Halle (Germany); Hari Babu, V. [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstraße 2, D-04103 Leipzig (Germany); Chiang, C.-T. [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany); Institut für Physik, Naturwissenschaftliche Fakultät II, Martin-Luther-Universität Halle-Wittenberg, von-Danckelmann-Platz 3, D-06099 Halle (Germany); Magnano, E.; Bondino, F. [IOM-CNR, Laboratorio Nazionale TASC, Strada Statale 14, km 163.5, Basovizza, I-34149 Trieste (Italy); Denecke, R. [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstraße 2, D-04103 Leipzig (Germany); Schindler, K.-M., E-mail: karl-michael.schindler@physik.uni-halle.de [Institut für Physik, Naturwissenschaftliche Fakultät II, Martin-Luther-Universität Halle-Wittenberg, von-Danckelmann-Platz 3, D-06099 Halle (Germany)

    2013-11-15

    The coercivity and saturation magnetization of ultrathin films of Fe on a BaTiO{sub 3}(001) single crystal substrate have been determined using magneto-optic Kerr effect (MOKE) and X-ray magnetic circular dichroism (XMCD) as a function of annealing temperature. Films deposited at room temperature exhibit bulk-like properties, whereas with increasing annealing temperature coercivity increases and saturation magnetization decreases. Investigations with scanning electron microscopy (SEM) and low-energy electron diffraction (LEED) reveal that annealing causes a morphology transformation from a continuous flat film, which completely covers the substrate, to nanoislands via self-assembled growth. The morphology and size of the islands imply stronger pinning of domain walls or complex magnetic structures as the origin of their particular magnetic properties. - Highlights: • Effect of annealing on the magnetic properties of Fe films on BaTiO{sub 3} determined. • Highly directional Fe nanoislands are formed due to self-assembly upon annealing. • Coercivity increases with increasing annealing temperature. • Saturation magnetization and magnetic moment decrease. • Reasons for the changes in magnetic properties and morphology are discussed.

  19. High accuracy magnetic field mapping of the LEP spectrometer magnet

    CERN Document Server

    Roncarolo, F

    2000-01-01

    The Large Electron Positron accelerator (LEP) is a storage ring which has been operated since 1989 at the European Laboratory for Particle Physics (CERN), located in the Geneva area. It is intended to experimentally verify the Standard Model theory and in particular to detect with high accuracy the mass of the electro-weak force bosons. Electrons and positrons are accelerated inside the LEP ring in opposite directions and forced to collide at four locations, once they reach an energy high enough for the experimental purposes. During head-to-head collisions the leptons loose all their energy and a huge amount of energy is concentrated in a small region. In this condition the energy is quickly converted in other particles which tend to go away from the interaction point. The higher the energy of the leptons before the collisions, the higher the mass of the particles that can escape. At LEP four large experimental detectors are accommodated. All detectors are multi purpose detectors covering a solid angle of alm...

  20. Abnormal variation of magnetic properties with Ce content in (PrNdCe)2Fe14B sintered magnets prepared by dual alloy method

    Science.gov (United States)

    Xue-Feng, Zhang; Jian-Ting, Lan; Zhu-Bai, Li; Yan-Li, Liu; Le-Le, Zhang; Yong-Feng, Li; Qian, Zhao

    2016-05-01

    Resource-saving (PrNdCe)2Fe14B sintered magnets with nominal composition (PrNd)15-x Ce x Fe77B8 (x = 0-10) were prepared using a dual alloy method by mixing (PrNd)5Ce10Fe77B8 with (PrNd)15Fe77B8 powders. For Ce atomic percent of 1% and 2%, coercivity decreases dramatically. With further increase of Ce atomic percent, the coercivity increases, peaks at 6.38 kOe in (PrNd)11Ce4Fe77B8, and then declines gradually. The abnormal dependence of coercivity is likely related to the inhomogeneity of rare earth chemical composition in the intergranular phase, where PrNd concentration is strongly dependent on the additive amount of (PrNd)5Ce10Fe77B8 powders. In addition, for Ce atomic percent of 8%, 7%, and 6% the coercivity is higher than that of magnets prepared by the conventional method, which shows the advantage of the dual alloy method in preparing high abundant rare earth magnets. Project supported by the National Natural Science Foundation of China (Grant Nos. 51461033, 51571126, 51541105, and 11547032), the Natural Science Foundation of Inner Mongolia, China (Grant No. 2013MS0110), and the Inner Mongolia University of Science and Technology Innovation Fund, China.

  1. Flatland Electrons in High Magnetic Fields

    Science.gov (United States)

    Shayegan, M.

    This paper provides a review of recent developments in the physics of two-dimensional carrier systems in perpendicular magnetic fields. The emphasis is on many-body phenomena in very clean GaAs/AlGaAs heterostructures, probed via magnetotransport measurements. Topics that are discussed include the integer and fractional quantum Hall effects, Wigner crystallization, composite Fermions, Skyrmions, stripe and bubble phases in single layer systems, and electron-hole pairing and Bose-Einstein condensation in interacting bilayer systems.

  2. Advanced measurements and techniques in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, L.J.; Rickel, D.G. [Los Alamos National Lab., NM (United States); Lacerda, A.H. [Florida State Univ., Tallahassee, FL (United States); Kim, Y. [Northeastern Univ., Boston, MA (United States)

    1997-07-01

    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). High magnetic fields present a unique environment for studying the electronic structure of materials. Two classes of materials were chosen for experiments at the national high Magnetic Field Laboratory at Los Alamos: highly correlated electron systems and semiconductors. Magnetotransport and thermodynamic experiments were performed on the renormalized ground states of highly correlated electron systems (such as heavy fermion materials and Kondo insulators) in the presence of magnetic fields that are large enough to disrupt the many-body correlations. A variety of optical measurements in high magnetic fields were performed on semiconductor heterostructures including GaAs/AlGaAs single heterojunctions (HEMT structure), coupled double quantum wells (CDQW), asymmetric coupled double quantum wells (ACDQW), multiple quantum wells and a CdTe single crystal thin film.

  3. Status of high temperature superconductor development for accelerator magnets

    Science.gov (United States)

    Hirabayashi, H.

    1995-01-01

    High temperature superconductors are still under development for various applications. As far as conductors for magnets are concerned, the development has just been started. Small coils wound by silver sheathed Bi-2212 and Bi-2223 oxide conductors have been reported by a few authors. Essential properties of high T(sub c) superconductors like pinning force, coherent length, intergrain coupling, weak link, thermal property, AC loss and mechanical strength are still not sufficiently understandable. In this talk, a review is given with comparison between the present achievement and the final requirement for high T(sub c) superconductors, which could be particularly used in accelerator magnets. Discussions on how to develop high T(sub c) superconductors for accelerator magnets are included with key parameters of essential properties. A proposal of how to make a prototype accelerator magnet with high T(sub c) superconductors with prospect for future development is also given.

  4. Coercivity behavior in Gd(Co{sub 1−x}Cu{sub x}){sub 5} system as function of the microstructureevolution

    Energy Technology Data Exchange (ETDEWEB)

    Pentón-Madrigal, A. [Facultad de Física, Universidad de La Habana, San Lazaro y L. C.P. 10400, C. Habana (Cuba); Oliveira, L.A.S. de, E-mail: laso.luiz@gmail.com [Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, Barão Geraldo, Campinas, SP (Brazil); Sinnecker, J.P.; Souza, D.M. [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud, 150—Urca, 22290-180, Rio de Janeiro (Brazil); Grössinger, R. [Institute für Festkörperphysik, TU Wien, Wiedner Hauptstr. 8-10, A-1040, Vienna (Austria); Concepción-Rosabal, B.; Estévez-Rams, E.; Diaz-Castañon, S. [Instituto de Ciencia y Tecnología de Materiales (IMRE), Zapata y G, Vedado. CP 10400, C. Habana (Cuba)

    2013-04-01

    Magnetic measurements, X-ray diffraction and scanning electron microscopy (SEM) experiments were carried out in the as-cast Gd(Co{sub 1−x}Cu{sub x}){sub 5} samples with different Co/Cu content. Already in the as cast state, this system shows high coercive field for x=0.3 and a magnetization driven by nucleation of reversal domain. SEM micrograph and microanalysis show possible spinodal decomposition in the as-cast state, hence regions with different Co/Cu-content are observed, while the Gd-content almost does not change. High resolution X-ray diffraction patterns show a main CaCu{sub 5}-type structure with traces of a secondary phase and distorted peak profiles as function of the Cu content. The evolution of the microstructure is discussed in relation with the Cu incorporation into the CaCu{sub 5}-type structure. The Cu addition avoids the formation of the 2:7 phase within the 1:5 matrix, favoring the formation of a more homogeneous Gd(Co,Cu){sub 5} phase. The relation between the observed microstructure and the magnetic behavior is also discussed.

  5. BaFe{sub 12}O{sub 19} powder with high magnetization prepared by acetone-aided coprecipitation

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hsuan-Fu, E-mail: hfyu@mail.tku.edu.tw

    2013-09-15

    BaFe{sub 12}O{sub 19} particles with high magnetization were produced using an acetone-aided coprecipitation process. An aqueous solution of iron and barium nitrates, in an Fe{sup 3+}/Ba{sup 2+} molar ratio of 12, was added in a stirred precipitation liquid medium composed of H{sub 2}O, CH{sub 3}(CO)CH{sub 3} and NH{sub 4}OH. After reacting metallic ions with ammonia, the precipitates were formed, centrifugally filtered, freeze dried and calcined. Effects of amount of the acetone in the precipitation liquid medium on the formation of crystalline BaFe{sub 12}O{sub 19} were investigated. The presence of acetone in the precipitation liquid medium can greatly promote formation of the crystalline BaFe{sub 12}O{sub 19} at temperature as low as 650 °C and can enhance magnetization of the derived particles. On the other hand, raising the calcination temperature can effectively accelerate development of crystallite morphology and magnetic characters of the barium hexaferrites. While the barium hexaferrite powder obtained without acetone additions and calcined at 1000 °C had magnetization (measured at 50 kOe; M(50 kOe)) of 63.5 emu/g, remanence magnetization (Mr) of 31.3 emu/g and coercivity (Hc) of 4.7 kOe, the single magnetic domain size BaFe{sub 12}O{sub 19} powder with M(50 kOe) of 70.6 emu/g, Mr of 34.4 emu/g and Hc of 3.7 kOe was produced at 1000 °C, using a precipitation liquid medium of 64 vol% acetone. - Highlights: • BaFe{sub 12}O{sub 19} with high magnetic characters was produced by an acetone-aided coprecipitation. • The effects of acetone addition in the precipitation on the formation of BaFe{sub 12}O{sub 19} were studied. • Acetone presence in the precipitation liquid medium promoted BaFe{sub 12}O{sub 19} formation at ≥650 °C. • BaFe{sub 12}O{sub 19} with M(50 kOe) of 70.6 emu/g, Mr of 34.4 emu/g and Hc of 3.7 kOe was obtained.

  6. Scientific and conceptual flaws of coercive treatment models in addiction.

    Science.gov (United States)

    Uusitalo, Susanne; van der Eijk, Yvette

    2016-01-01

    In conceptual debates on addiction, neurobiological research has been used to support the idea that addicted drug users lack control over their addiction-related actions. In some interpretations, this has led to coercive treatment models, in which, the purpose is to 'restore' control. However, neurobiological studies that go beyond what is typically presented in conceptual debates paint a different story. In particular, they indicate that though addiction has neurobiological manifestations that make the addictive behaviour difficult to control, it is possible for individuals to reverse these manifestations through their own efforts. Thus, addicted individuals should not be considered incapable of making choices voluntarily, simply on the basis that addiction has neurobiological manifestations, and coercive treatment models of addiction should be reconsidered in this respect. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  7. Replacing critical rare earth materials in high energy density magnets

    Science.gov (United States)

    McCallum, R. William

    2012-02-01

    High energy density permanent magnets are crucial to the design of internal permanent magnet motors (IPM) for hybride and electric vehicles and direct drive wind generators. Current motor designs use rare earth permanent magnets which easily meet the performance goals, however, the rising concerns over cost and foreign control of the current supply of rare earth resources has motivated a search for non-rare earth based permanent magnets alloys with performance metrics which allow the design of permanent magnet motors and generators without rare earth magnets. This talk will discuss the state of non-rare-earth permanent magnets and efforts to both improve the current materials and find new materials. These efforts combine first principles calculations and meso-scale magnetic modeling with advance characterization and synthesis techniques in order to advance the state of the art in non rare earth permanent magnets. The use of genetic algorithms in first principle structural calculations, combinatorial synthesis in the experimental search for materials, atom probe microscopy to characterize grain boundaries on the atomic level, and other state of the art techniques will be discussed. In addition the possibility of replacing critical rare earth elements with the most abundant rare earth Ce will be discussed.

  8. Magnetic superelevation design of Halbach permanent magnet guideway for high-temperature superconducting maglev

    Science.gov (United States)

    Lei, Wuyang; Qian, Nan; Zheng, Jun; Huang, Huan; Zhang, Ya; Deng, Zigang

    2017-07-01

    To improve the curve negotiating ability of high-temperature superconducting (HTS) maglev system, a special structure of magnetic superelevation for double-pole Halbach permanent magnet guideway (PMG) was designed. The most significant feature of this design is the asymmetrical PMG that forms a slanting magnetic field without affecting the smoothness of the PMG surface. When HTS maglev vehicle runs through curves with magnetic superelevation, the vehicle will slant due to asymmetry in magnetic field and the flux-pinning effect of onboard HTS bulks. At the same time, one component of the levitation force provides a part of the centripetal force that reduces lateral acceleration of the vehicle and thus enhances its curve negotiating ability. Furthermore, the slant angle of magnetic superelevation can be adjusted by changing the materials and the thickness of the added permanent magnets. This magnetic superelevation method, together with orographic uplift, can be applied to different requirements of PMG designs. Besides, the applicability of this method would benefit future development of high-speed HTS maglev system.

  9. Magnetic properties of sintered high energy sm-co and nd-fe-b magnets

    Directory of Open Access Journals (Sweden)

    Talijan Nadežda M.

    2006-01-01

    Full Text Available Magnetic properties of permanent magnetic materials based on intermetallic compounds of Sm-Co and Nd-Fe-B are in direct dependence on the microstructure. In the first part of this paper, having in mind the importance of the regime of sintering and heat treatment to obtain the optimal magnetic structure, yet another approach in defining the most adequate technological parameters of the sintering process for applied heat treatment conditions was made. The goal of these investigations was to use the correlation that exists between sintering conditions (temperature and time and intensity of the diffraction peak of the (111 plane of the SmCo5 phase to optimize. In the second part a brief overview of high energy magnetic materials based on Nd-Fe-B is presented with special emphasis to the current research and development of high remanent nanocomposite magnetic materials based on Nd-Fe-B alloys with a reduced Nd content. Part of experimental results gained during research of the sintering process of SmCo5 magnetic materials were realized and published earlier. The scientific meeting devoted to the 60th anniversary of Frankel’s theory of sintering was an opportunity to show once more the importance and role of sintering in optimization of the magnetic microstructure of sintered Sm Co5 magnetic materials.

  10. Conceptual Design of the 45 T Hybrid Magnet at the Nijmegen High Field Magnet Laboratory

    CERN Document Server

    Wiegers, SAJ; Bird, M D; Rook, J; Perenboom, J A A J; Wiegers, S A J; Bonito-Oliva, A; den Ouden, A

    2010-01-01

    A 45 T Hybrid Magnet System is being developed at the Nijmegen High Field Magnet Laboratory as part of the Nijmegen Center for Advanced Spectroscopy. The 45 T Hybrid Magnet System will be used in combination with far-infra-red light produced by a Free Electron Laser under construction directly adjacent to the High Field Magnet Laboratory. The superconducting outsert magnet will consist of three CICC coils wound on a single coil form, using Nb3Sn strands. A test program for strand and cable qualification is underway. The CICC will carry 13 kA and the coils will produce 12 T on axis field in a 600 mm warm bore. The nominal operating temperature will be 4.5 K maintained with forced-flow supercritical helium. The insert magnet will produce 33 T at 40 kA in a 32 mm bore consuming 20 MW, and will consist of four coils. The insert magnet will be galvanically and mechanically isolated from the outsert magnet. Complete system availability for users is expected in 2014. In this paper we will report on the conceptual de...

  11. Coercive Disarmament, Demobilization and Reintegration (DDR): Can It Be Successful

    Science.gov (United States)

    2008-03-01

    DEMOBLIZATION AND REINTEGRATION (DDR): CAN IT BE SUCCESSFUL ? by Shane R. Doolan March 2008 Thesis Co-Advisors: Jeanne Giraldo...DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE Coercive Disarmament Demobilization and Reintegration (DDR): Can it be Successful ? 6. AUTHOR(S...DISARMAMENT DEMOBILIZATION AND REINTEGRATION (DDR): CAN IT BE SUCCESSFUL ? Shane R. Doolan Captain, United States Army B.S., Police Studies, John Jay

  12. Inorganic Nanostructured High-Temperature Magnet Wires Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This project will develop a high-temperature tolerant electrically-insulating coating for magnet wires. The Phase I program will result in a flexible, inorganic...

  13. Radiation Shielding Utilizing A High Temperature Superconducting Magnet Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This project aims to leverage near-term high-temperature superconducting technologies to assess applicability of magnetic shielding for protecting against exposure...

  14. Self-propagating high temperature synthesis and magnetic ...

    Indian Academy of Sciences (India)

    Unknown

    , microstructure and magnetic properties of the combustion products. The effect of ... productivity, low external energy consumption, short synthesis time, simple facility and high quality of the products. Although there have been many attempts to.

  15. Structural and magnetic properties of granular CoPd multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Vivas, L.G.; Figueroa, A.I.; Bartolomé, F. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain); Rubín, J. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Ciencia y Tecnología de Materiales y Fluidos, E-50018 Zaragoza (Spain); García, L.M. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain); Deranlot, C.; Petroff, F. [Unité Mixte de Physique CNRS/Thales, F-91767 Palaiseau Cedex, France and Université Paris-Sud, F-191405 Orsay Cedex (France); Ruiz, L.; González-Calbet, J.M [Dept. de Química Inorgánica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Brookes, N.B.; Wilhelm, F.; Rogalev, A. [European Synchrotron Radiation Facility (ESRF), CS40220, F-38043 Grenoble Cedex 9 (France); Bartolomé, J. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain)

    2016-02-15

    Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk. - Highlights: • CoPd granular nanolayers show perpendicular magnetic anisotropy. • Three magnetic phases are detected: hard-ferro, soft-ferro and superparamagnetism. • The nanoparticles have Co-core and CoPd alloy shell morphology.

  16. High magnetic fields in couplers of x-band acceleratingstructures

    CERN Document Server

    Dolgashev, V A

    2003-01-01

    Recent high power tests of x-band accelerating structures at SLAC have shown that Coupler models were matched with an automated procedure that uses the commercial To reduce the high magnetic fields new couplers were designed. These couplers and typical results for couplers with sharp and rounded irises are discussed in code HFSS. This matching procedure is based on calculation of reflection from have 3 mm radius waveguide-to-coupler-cell iris and maximum magnetic field below is consistent with a model of pulsed heating due to high magnetic fields. The magnetic fields, 3D electrodynamics models of the couplers were built and matched. matching, the magnetic and electric fields in the couplers were calculated for typical observed damage is located in the region of high magnetic fields. To calculate these on sharp (approx 80 micron radius) edges of the waveguide-to-coupler-cell irises. For operation parameters. Highest magnetic fields on the order of 1 MA/m were found some input couplers, electric fields on these...

  17. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads.

    Science.gov (United States)

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-01

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm(2), a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle's position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  18. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

    Energy Technology Data Exchange (ETDEWEB)

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim [Institute of Bioelectronics (ICS-8/PGI-8), Forschungszentrum Jülich GmbH, 52425 Jülich (Germany)

    2015-04-15

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm{sup 2}, a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle’s position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  19. Low temperature superconductor and aligned high temperature superconductor magnetic dipole system and method for producing high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Ramesh; Scanlan, Ronald; Ghosh, Arup K.; Weggel, Robert J.; Palmer, Robert; Anerella, Michael D.; Schmalzle, Jesse

    2017-10-17

    A dipole-magnet system and method for producing high-magnetic-fields, including an open-region located in a radially-central-region to allow particle-beam transport and other uses, low-temperature-superconducting-coils comprised of low-temperature-superconducting-wire located in radially-outward-regions to generate high magnetic-fields, high-temperature-superconducting-coils comprised of high-temperature-superconducting-tape located in radially-inward-regions to generate even higher magnetic-fields and to reduce erroneous fields, support-structures to support the coils against large Lorentz-forces, a liquid-helium-system to cool the coils, and electrical-contacts to allow electric-current into and out of the coils. The high-temperature-superconducting-tape may be comprised of bismuth-strontium-calcium-copper-oxide or rare-earth-metal, barium-copper-oxide (ReBCO) where the rare-earth-metal may be yttrium, samarium, neodymium, or gadolinium. Advantageously, alignment of the large-dimension of the rectangular-cross-section or curved-cross-section of the high-temperature-superconducting-tape with the high-magnetic-field minimizes unwanted erroneous magnetic fields. Alignment may be accomplished by proper positioning, tilting the high-temperature-superconducting-coils, forming the high-temperature-superconducting-coils into a curved-cross-section, placing nonconducting wedge-shaped-material between windings, placing nonconducting curved-and-wedge-shaped-material between windings, or by a combination of these techniques.

  20. A harsh parenting team? Maternal reports of coparenting and coercive parenting interact in association with children's disruptive behaviour.

    Science.gov (United States)

    Latham, Rachel M; Mark, Katharine M; Oliver, Bonamy R

    2017-05-01

    Parenting and coparenting are both important for children's adjustment, but their interaction has been little explored. Using a longitudinal design and considering two children per family, we investigated mothers' and fathers' perceptions of coparenting as moderators of associations between their coercive parenting and children's disruptive behaviour. Mothers and fathers from 106 'intact' families were included from the Twins, Family and Behaviour study. At Time 1 (M child age  = 3 years 11 months, SD child age  = 4.44 months) parents reported on their coercive parenting and children's disruptive behaviour via questionnaire; at Time 2 (M child age  = 4 years 8 months, SD child age  = 4.44 months) perceptions of coparenting and the marital relationship were collected by telephone interview. Questionnaire-based reports of children's disruptive behaviour were collected at follow-up (M child age  = 5 years 11 months, SD child age  = 5.52 months). Multilevel modelling was used to examine child-specific and family-wide effects. Conservative multilevel models including both maternal and paternal perceptions demonstrated that maternal perceptions of coparenting and overall coercive parenting interacted in their prediction of parent-reported child disruptive behaviour. Specifically, accounting for perceived marital quality, behavioural stability, and fathers' perceptions, only in the context of perceived higher quality coparenting was there a positive association between mother-reported overall coercive parenting and children's disruptive behaviour at follow-up. When combined with highly coercive parenting, maternal perceptions of high quality coparenting may be detrimental for children's adjustment. © 2016 Association for Child and Adolescent Mental Health.

  1. MAGNETIC WOVEN FABRICS - PHYSICAL AND MAGNETIC PROPERTIES

    Directory of Open Access Journals (Sweden)

    GROSU Marian C

    2015-05-01

    Full Text Available A coated material is a composite structure that consists of at least two components: base material and coating layer. The purpose of coating is to provide special properties to base material, with potential to be applied in EMI shielding and diverse smart technical fields. This paper reports the results of a study about some physical and magnetic properties of coated woven fabrics made from cotton yarns with fineness of 17 metric count. For this aim, a plain woven fabric was coated with a solution hard magnetic polymer based. As hard magnetic powder, barium hexaferrite (BaFe12O19 was selected. The plain woven fabric used as base has been coated with five solutions having different amounts of hard magnetic powder (15% - 45% in order to obtain five different magnetic woven fabrics. A comparison of physical properties regarding weight (g/m2, thickness (mm, degree of charging (% and magnetic properties of magnetic woven samples were presented. Saturation magnetizing (emu/g, residual magnetizing (emu/g and coercive force (kA/m of pure hard magnetic powder and woven fabrics have been studied as hysteresis characteristics. The magnetic properties of the woven fabrics depend on the mass percentage of magnetic powder from coating solution. Also, the residual magnetism and coercive field of woven fabrics represents only a part of bulk barium hexafferite residual magnetism and coercive field.

  2. Survey of Processing Methods for High Strength High Conductivity Wires for High Field Magnet Applications

    Energy Technology Data Exchange (ETDEWEB)

    Han, K.; Embury, J.D.

    1998-10-01

    This paper will deal with the basic concepts of attaining combination of high strength and high conductivity in pure materials, in-situ composites and macrocomposites. It will survey current attainments, and outline where some future developments may lie in developing wire products that are close to the theoretical strength of future magnet applications.

  3. Strain-assisted magnetization reversal in Co/Ni multilayers with perpendicular magnetic anisotropy

    Science.gov (United States)

    Gopman, D. B.; Dennis, C. L.; Chen, P. J.; Iunin, Y. L.; Finkel, P.; Staruch, M.; Shull, R. D.

    2016-01-01

    Multifunctional materials composed of ultrathin magnetic films with perpendicular magnetic anisotropy combined with ferroelectric substrates represent a new approach toward low power, fast, high density spintronics. Here we demonstrate Co/Ni multilayered films with tunable saturation magnetization and perpendicular anisotropy grown directly on ferroelectric PZT [Pb(Zr0.52Ti0.48)O3] substrate plates. Electric fields up to ±2 MV/m expand the PZT by 0.1% and generate at least 0.02% in-plane compression in the Co/Ni multilayered film. Modifying the strain with a voltage can reduce the coercive field by over 30%. We also demonstrate that alternating in-plane tensile and compressive strains (less than 0.01%) can be used to propagate magnetic domain walls. This ability to manipulate high anisotropy magnetic thin films could prove useful for lowering the switching energy for magnetic elements in future voltage-controlled spintronic devices. PMID:27297638

  4. Strain-assisted magnetization reversal in Co/Ni multilayers with perpendicular magnetic anisotropy.

    Science.gov (United States)

    Gopman, D B; Dennis, C L; Chen, P J; Iunin, Y L; Finkel, P; Staruch, M; Shull, R D

    2016-06-14

    Multifunctional materials composed of ultrathin magnetic films with perpendicular magnetic anisotropy combined with ferroelectric substrates represent a new approach toward low power, fast, high density spintronics. Here we demonstrate Co/Ni multilayered films with tunable saturation magnetization and perpendicular anisotropy grown directly on ferroelectric PZT [Pb(Zr0.52Ti0.48)O3] substrate plates. Electric fields up to ±2 MV/m expand the PZT by 0.1% and generate at least 0.02% in-plane compression in the Co/Ni multilayered film. Modifying the strain with a voltage can reduce the coercive field by over 30%. We also demonstrate that alternating in-plane tensile and compressive strains (less than 0.01%) can be used to propagate magnetic domain walls. This ability to manipulate high anisotropy magnetic thin films could prove useful for lowering the switching energy for magnetic elements in future voltage-controlled spintronic devices.

  5. Experimental Contribution to High-Precision Characterization of Magnetic Forces in Active Magnetic Bearings

    DEFF Research Database (Denmark)

    Kjølhede, Klaus; Santos, Ilmar

    2007-01-01

    Parameter identification procedures and model validation are major steps toward intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model...... contribution of the work is the characterization of magnetic forces by using two different experimental approaches. Such approaches are investigated and described in detail. A special test rig is designed where the four pole AMB is able to generate forces up to 1900 N. The high-precision characterization...... of the magnetic forces is conducted using different experimental tests: (i) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor (ii) by measuring the input current and bearing...

  6. Application of high temperature superconductors to high-gradient magnetic separation

    Energy Technology Data Exchange (ETDEWEB)

    Daugherty, M.A.; Prenger, F.C.; Hill, D.D.; Daney, D.E.; Worl, L.W.; Schake, A.R.; Padilla, D.D.

    1994-06-01

    High Gradient Magnetic Separation (HGMS) is a powerful technique which can be used to separate widely dispersed contaminants from a host material, This technology can separate magnetic solids from other solids, liquids or gases. As the name implies HGMS uses large magnetic field gradients to separate ferromagnetic and paramagnetic particles. HGMS separators usually consist of a high-field solenoid magnet, the bore of which contains a fine-structured, ferromagnetic matrix material. The matrix material locally distorts the magnetic field and creates large field gradients in the vicinity of the matrix elements. These elements then become trapping sites for magnetic particles and are the basis for the magnetic separation. In this paper we discuss the design and construction of a prototype HGMS unit using a magnet made with high temperature superconductors (HTS). The prototype consists of an outer vacuum vessel which contains the HTS solenoid magnet The magnet is surrounded by a thermal radiation shield and multilayer insulation (MLI) blankets. The magnet, thermal shield and current leads all operate in a vacuum and are cooled by a cryocooler. High temperature superconducting current leads are used to reduce the heat leak from the ambient environment to the HTS magnet.

  7. Magnetoresistance peculiarities of bismuth wires in high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Condrea, E., E-mail: condrea@nano.asm.md [Institute of Electronic Engineering and Nanotechnologies, Academy of Science of Moldova, 2028 Chisinau, Republic of Moldova (Moldova, Republic of); International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, 51-421 Wroclaw (Poland); Gilewski, A. [International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, 51-421 Wroclaw (Poland); MagNet, 50-421 Wroclaw (Poland); Nicorici, A. [Institute of Electronic Engineering and Nanotechnologies, Academy of Science of Moldova, 2028 Chisinau, Republic of Moldova (Moldova, Republic of)

    2016-03-11

    Magnetoresistance measurements of Bi wires performed in the magnetic field oriented along the bisector axis revealed unexpected anomalous peaks in a high magnetic field far above the quantum limit of the electrons. By combining a magnetic field and an uniaxial strain, we obtained a modification of the electronic structure; as a result, the quantum limit for light and heavy electrons is changed in a different way. For the case where heavy electrons are in the quantum limit, a correlation between the exit of the lowest Landau level of light electrons and the Lifshitz transition was found. - Highlights: • Glass-coated single-crystalline Bi wires attain high limit of elastic strain of up to 3.0%. • Selective modification of the electronic structure of Bi wires is obtained by combining a high magnetic field and uniaxial strain. • The correlation between the exit of the lowest Landau level of electrons and Lifshitz transition was found.

  8. High resolution remanent magnetization scanner for long cores

    Science.gov (United States)

    Demory, François; Quesnel, Yoann; Uehara, Minoru; Rochette, Pierre; Zylberman, William; Romey, Carole; Pignol, Laure; Andrieu-Ponel, Valérie

    2017-04-01

    Superconducting rock magnetometer reaches saturation when measuring magnetic moments higher than 5 10-5 Am2. Due to the distance of the sensor from the measurement zone, the spatial resolution is low for continuous measurements led on U channel or cores. To solve these problems, we designed a core logger dedicated to the measurement of remanent magnetizations. Based on a fluxgate sensor located very close to the sample, the spatial resolution of the core logger is infra-centimetric. The fluxgate sensor is also able to detect magnetic fields of few nT produced by magnetic moments of the order of few 10-8 Am2. As the equipment does not reach saturation, we measured isothermal remanent magnetization of highly magnetic samples. This magnetization was acquired perpendicularly to the long axis of U-channels from Cassis paleo-lake (Romey et al., 2015) and of cores from Haughton impact structure (Zylberman et al., submitted) using Halbach cylinders (Rochette et al., 2001). To interpret local magnetic fields in terms of magnetic moments, we performed an inter-calibration with the superconducting rock magnetometer and signal inversion. This development led to the filing of a patent (FR.16/53142) and is funded by the ECCOREV project MESENVIMAG. References: Rochette, P., Vadeboin, F., Clochard, L., 2001. Rock magnetic applications of Halbach cylinders. Physics of the Earth and Planetary Interiors 126, 109-117. Romey, C., Vella, C., Rochette, P., Andrieu-Ponel, V., Magnin, F., Veron, A., Talon, B., Landure, C., D'Ovidio, A.M., Delanghe, D., Ghilardi, M., Angeletti, B., 2015. Environmental imprints of landscape evolution and human activities during the Holocene in a small catchment of the Calanques Massif (Cassis, southern France). Holocene 25 (9), 1454-1469. Zylberman W., Quesnel Y., Rochette P., Osinski G. R., Marion C., Gattacceca J. (submitted to MAPS) Hydrothermally-enhanced magnetization at the center of the Haughton impact structure? (Nunavut, Canada).

  9. Bringing Earth Magnetism Research into the High School Physics Classroom

    Science.gov (United States)

    Smirnov, A. V.; Bluth, G.; Engel, E.; Kurpier, K.; Foucher, M. S.; Anderson, K. L.

    2015-12-01

    We present our work in progress from an NSF CAREER project that aims to integrate paleomagnetic research and secondary school physics education. The research project is aimed at quantifying the strength and geometry of the Precambrian geomagnetic field. Investigation of the geomagnetic field behavior is crucial for understanding the mechanisms of field generation, and the development of the Earth's atmosphere and biosphere, and can serve as a focus for connecting high-level Earth science research with a standard physics curriculum. High school science teachers have participated in each summer field and research component of the project, gaining field and laboratory research experience, sets of rock and mineral samples, and classroom-tested laboratory magnetism activities for secondary school physics and earth science courses. We report on three field seasons of teacher field experiences and two years of classroom testing of paleomagnetic research materials merged into physics instruction on magnetism. Students were surveyed before and after dedicated instruction for both perceptions and attitude towards earth science in general, then more specifically on earth history and earth magnetism. Students were also surveyed before and after instruction on major earth system and magnetic concepts and processes, particularly as they relate to paleomagnetic research. Most students surveyed had a strongly positive viewpoint towards the study of Earth history and the importance of studying Earth Sciences in general, but were significantly less drawn towards more specific topics such as mineralogy and magnetism. Students demonstrated understanding of Earth model and the basics of magnetism, as well as the general timing of life, atmospheric development, and magnetic field development. However, detailed knowledge such as the magnetic dynamo, how the magnetic field has changed over time, and connections between earth magnetism and the development of an atmosphere remained largely

  10. Determination of the effective anisotropy constant of CoFe{sub 2}O{sub 4} nanoparticles through the T-dependence of the coercive field

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, M. H.; Meneses, C. T.; Duque, J. G. S. [Núcleo de Pós-Graduação em Física, Campus Prof. José Aloísio de Campos, UFS, 49100-000 São Cristóvão, SE (Brazil); Lima, R. J. S. [Universidade Federal de Campina Grande, Centro de Ciências e Tecnologia, Unidade Acadêmica de Física, 58429-900, Campina Grande, PB (Brazil); Folly, W. S. D. [Departamento de Geologia, Universidade Federal de Sergipe, 49100-000 São Cristóvão (Brazil); Sarmento, V. H. V. [Núcleo de Pós-Graduação em Química, Campus Prof. José Aloísio de Campos, UFS, 49100-000 São Cristóvão, SE (Brazil); Coelho, A. A. [Instituto de Física “Gleb Wataghin,” UNICAMP, 13083-970 Campinas, SP (Brazil)

    2016-03-07

    We present a systematic study of the coercive field of CoFe{sub 2}O{sub 4}–SiO{sub 2} nanocomposites. The samples were prepared via the sol-gel method by using the Tetraethyl Orthosilicate as starting reagent. Results of X-ray diffraction, transmission electron microscopy, and X-ray fluorescence confirm the dispersion of the magnetic nanoparticles inside the silica matrix. In addition, the shift in the maximum of Zero-Field-Cooled curves observed by varying the weight ratio of CoFe{sub 2}O{sub 4} nanoparticles to the precursor of silica is consistent with the increasing of average interparticle distances. Because our samples present a particle size distribution, we have used a generalized model which takes account such parameter to fit the experimental data of coercive field extracted from the magnetization curves as a function of applied field. Unlike most of the coercive field results reported in the literature for this material, the use of this model provided a successful description of the temperature dependence of the coercive field of CoFe{sub 2}O{sub 4} nanoparticles in a wide temperature range. Surprisingly, we have observed the decreasing of the nanoparticles anisotropy constant in comparison to the bulk value expected for the material. We believe that this can be interpreted as due to both the migration of the Co{sup 2+} from octahedral to tetrahedral sites.

  11. Induction heating of rotating nonmagnetic billet in magnetic field produced by high-parameter permanent magnets

    Directory of Open Access Journals (Sweden)

    Ivo Doležel

    2014-04-01

    Full Text Available An advanced way of induction heating of nonmagnetic billets is discussed and modeled. The billet rotates in a stationary magnetic field produced by unmoving high-parameter permanent magnets fixed on magnetic circuit of an appropriate shape. The mathematical model of the problem consisting of two coupled partial differential equations is solved numerically, in the monolithic formulation. Computations are carried out using our own code Agros2D based on a fully adaptive higher-order finite element method. The most important results are verified experimentally on our own laboratory device.

  12. Magnetic anisotropy and high-field magnetization process of CeCo[sub 5

    Energy Technology Data Exchange (ETDEWEB)

    Bartashevich, M.I. (Tokyo Univ. (Japan). Inst. for Solid State Physics (ISSP)); Goto, T. (Tokyo Univ. (Japan). Inst. for Solid State Physics (ISSP)); Radwanski, R.J. (Centre for Solid State Physics, Krakow (Poland)); Korolyov, A.V. (Inst. of Metal Physics, Ekaterinburg (Russian Federation))

    1994-03-01

    The magnetization process of single-crystalline CeCo[sub 5] has been measured at various temperatures from 4.2 to 300 K in high magnetic fields up to 40 T. The uniaxial magnetocrystalline anisotropy constant K[sub 1] is found to be about 35% higher than that of YCo[sub 5]. The magnetization anisotropy reaches p = 0.12 at 4.2 K, which is also higher than that of YCo[sub 5]. Both the anisotropies decrease with increasing temperature. These experimental results indicate that Ce in CeCo[sub 5] is in a mixed-valence state. (orig.)

  13. Highly Efficient Domain Walls Injection in Perpendicular Magnetic Anisotropy Nanowire.

    Science.gov (United States)

    Zhang, S F; Gan, W L; Kwon, J; Luo, F L; Lim, G J; Wang, J B; Lew, W S

    2016-04-21

    Electrical injection of magnetic domain walls in perpendicular magnetic anisotropy nanowire is crucial for data bit writing in domain wall-based magnetic memory and logic devices. Conventionally, the current pulse required to nucleate a domain wall is approximately ~10(12) A/m(2). Here, we demonstrate an energy efficient structure to inject domain walls. Under an applied electric potential, our proposed Π-shaped stripline generates a highly concentrated current distribution. This creates a highly localized magnetic field that quickly initiates the nucleation of a magnetic domain. The formation and motion of the resulting domain walls can then be electrically detected by means of Ta Hall bars across the nanowire. Our measurements show that the Π-shaped stripline can deterministically write a magnetic data bit in 15 ns even with a relatively low current density of 5.34 × 10(11) A/m(2). Micromagnetic simulations reveal the evolution of the domain nucleation - first, by the formation of a pair of magnetic bubbles, then followed by their rapid expansion into a single domain. Finally, we also demonstrate experimentally that our injection geometry can perform bit writing using only about 30% of the electrical energy as compared to a conventional injection line.

  14. High gradient magnetic separation applied to environmental remediation

    Energy Technology Data Exchange (ETDEWEB)

    Prenger, F.C.; Stewart, W.F.; Hill, D.D.; Avens, L.R.; Worl, L.A.; Schake, A.; Aguero, K.J. de; Padilla, D.D. [Los Alamos National Lab., NM (United States); Tolt, T.L. [Lockheed Environmental Systems and Technology Co., Las Vegas, NV (United States)

    1994-12-31

    High gradient magnetic separation (HGMS) is an application of superconducting magnet technology to the separation of magnetic solids from other solids, liquids, or gases. The production of both high magnetic fields (>4 T) and large field gradients using superconducting magnet technology has made it possible to separate a previously unreachable but large family of paramagnetic materials. This powerful technique can be used to separate widely dispersed contaminants from a host material, and it may be the only technique available for separating material in the colloidal state. Because it is a physical separation process, no additional waste is generated. The authors are applying this technology to the treatment of radioactive wastes for environmental remediation. They have conducted tests examining slurries containing nonradioactive, magnetic surrogates. Results from these studies were used to verify their analytical model of the separation process. The model describes the rate process for magnetic separation and is based on a force balance on the paramagnetic species. This model was used to support bench scale experiments and prototype separator designs.

  15. Magnetic field management of substations in high rise buildings

    Energy Technology Data Exchange (ETDEWEB)

    Farag, A.S.; Al-Shehri, A.M. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia); Cheng, T.C.; Du, Y.; Hu, L.; Penn, D. [Univ. of Southern California, LADWP, Los Angeles, CA (United States)

    1995-12-01

    The electric and magnetic field issue has become an area of increasing public concern. Utilities have been carrying out extensive projects to characterize and manage the magnetic fields around their substations in an effort to answer public concerns over the possible health hazard caused by these fields. This paper describes various techniques available for managing magnetic field strength levels in substations. The design guideline aids in the planning, design, construction of substation facilities. Low-frequency magnetic field is directly associated with current-carrying sources and its magnitude is proportional to the distance from the sources. Distribution substations in high-rise buildings are very close to public areas and the magnetic fields imposed by these substations might be relatively higher than that imposed by outdoor substations. Options to manage these substations fields are considered in this paper. Techniques to manage magnetic fields in substations such as: source relocation, compaction, rephasing, return-current control, passive and active shielding are discussed. Several techniques were applied to reduce the magnetic fields in the conference room located in the main floor above a substation located in the basement of the main office high-rise building of LADWP. 10 refs, 14 figs, 3 tabs

  16. Magnetic properties of Sm-Fe-N bulk magnets produced from Cu-plated Sm-Fe-N powder

    Directory of Open Access Journals (Sweden)

    Tetsuji Saito

    2017-05-01

    Full Text Available In this study, Cu-plated Sm-Fe-N powder was prepared for consolidation by the SPS method. The structures and magnetic properties of Sm-Fe-N bulk magnets produced from the Cu-plated Sm-Fe-N powder were examined. It was found that the powder could be consolidated into bulk materials at low temperatures of 473–673 K. The Sm-Fe-N magnet produced at a temperature of 473K from the Cu-plated Sm-Fe-N powder showed a high coercivity of 9.5 kOe, close to that of the Sm-Fe-N powder.

  17. Magnetoresistance peculiarities of bismuth wires in high magnetic field

    Science.gov (United States)

    Condrea, E.; Gilewski, A.; Nicorici, A.

    2016-03-01

    Magnetoresistance measurements of Bi wires performed in the magnetic field oriented along the bisector axis revealed unexpected anomalous peaks in a high magnetic field far above the quantum limit of the electrons. By combining a magnetic field and an uniaxial strain, we obtained a modification of the electronic structure; as a result, the quantum limit for light and heavy electrons is changed in a different way. For the case where heavy electrons are in the quantum limit, a correlation between the exit of the lowest Landau level of light electrons and the Lifshitz transition was found.

  18. Endogenous magnetic reconnection and associated high energy plasma processes

    Science.gov (United States)

    Coppi, B.; Basu, B.

    2018-02-01

    An endogenous reconnection process involves a driving factor that lays inside the layer where a drastic change of magnetic field topology occurs. A process of this kind is shown to take place when an electron temperature gradient is present in a magnetically confined plasma and the evolving electron temperature fluctuations are anisotropic. The width of the reconnecting layer remains significant even when large macroscopic distances are considered. In view of the fact that there are plasmas in the Universe with considerable electron thermal energy contents this feature can be relied upon in order to produce generation or conversion of magnetic energy, high energy particle populations and momentum and angular momentum transport.

  19. The Behavior Of Asymmetric Frontal Couplings With Permanent Magnets In Magnetic Powder And High Temperature Environments

    Directory of Open Access Journals (Sweden)

    Ion DOBROTA

    2002-12-01

    Full Text Available The main purpose of this paper is the comparative analysis of the behavior of frontal couplings with Nd-Fe-B permanent magnets in difficult environments, specific to metallurgy – such as environments with magnetic powders and high temperature – in two constructive variants: symmetric couplings and asymmetric couplings (with divided poles. The results show the superior performance of asymmetric couplings under the given conditions

  20. Superconductor Requirements and Characterization for High Field Accelerator Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Barzi, E.; Zlobin, A. V.

    2015-05-01

    The 2014 Particle Physics Project Prioritization Panel (P5) strategic plan for U.S. High Energy Physics (HEP) endorses a continued world leadership role in superconducting magnet technology for future Energy Frontier Programs. This includes 10 to 15 T Nb3Sn accelerator magnets for LHC upgrades and a future 100 TeV scale pp collider, and as ultimate goal that of developing magnet technologies above 20 T based on both High Temperature Superconductors (HTS) and Low Temperature Superconductors (LTS) for accelerator magnets. To achieve these objectives, a sound conductor development and characterization program is needed and is herein described. This program is intended to be conducted in close collaboration with U.S. and International labs, Universities and Industry.

  1. Magnetic Properties of FePt Nanoparticles Prepared by Sonoelectrodeposition

    Directory of Open Access Journals (Sweden)

    Nguyen Hoang Nam

    2012-01-01

    Full Text Available Sonoelectrodeposition is a useful technique to make metallic nanoparticles, using ultrasound during electrodeposition to remove nanoparticles as they grow on the cathode surface. This paper reports some structural and magnetic properties of FePt nanoparticles prepared by this method. The as-prepared Fe45Pt55 nanoparticles were ferromagnetic at room temperature. Upon annealing at 700°C for 1 h under H2 atmosphere, the saturation magnetization and the coercivity of the nanoparticles were improved significantly. The annealed nanoparticles showed a high coercivity of 13.5 kOe at 2 K and of 9 kOe at room temperature. Sonoelectrodeposition is a promising technique to make large quantity of FePt nanoparticles.

  2. High magnetic field {mu}SR instrument scientific case

    Energy Technology Data Exchange (ETDEWEB)

    Amato, A

    2005-10-15

    In order to gain more insight into the specific behavior of materials, it is often necessary to perform measurements as a function of different external parameters. Despite its high sensitivity to internal fields, this simple observation also applies for the {mu}SR technique. The most common parameter which can be tuned during an experiment is the sample temperature. By using a range of cryostats, temperatures between 0.02 and 900 K can be covered at the PSI {mu}SR Facility. On the other hand, and by using high-energy muons, pressures as high as 10'000 bars can nowadays be reached during {mu}SR experiments. As will be demonstrated in the following Sections, the magnetic field is an additional external parameter playing a fundamental role when studying the ground state properties of materials in condensed matter physics and chemistry. However, the availability of high magnetic fields for {mu}SR experiments is still rather limited. Hence, if on one hand the high value of the gyromagnetic ratio of the muon provides the high magnetic sensitivity of the method, on the other hand it can lead to very high muon-spin precession frequencies when performing measurements in applied fields (the muon-spin precession frequency in a field of 1 Tesla s 135.5 MHz). Consequently, the use of ultra-fast detectors and electronics is mandatory when measuring in magnetic fields exceeding 1 Tesla. If such fields are very intense when compared to the Earth magnetic field < 10{sup -4} Tesla), the energy associated with them is still modest in view of the thermal energy. Hence, the Zeeman energy splitting of a free electron in a magnetic field of 1 Tesla corresponds to a thermal energy as low as 0.67 Kelvin. It is worth mentioning that nowadays magnetic fields of the order of 10 to 15 Tesla are quite common in condensed matter laboratories and have opened up vast new exciting experimental possibilities. (author)

  3. High-Sensitivity Measurement of Density by Magnetic Levitation.

    Science.gov (United States)

    Nemiroski, Alex; Kumar, A A; Soh, Siowling; Harburg, Daniel V; Yu, Hai-Dong; Whitesides, George M

    2016-03-01

    This paper presents methods that use Magnetic Levitation (MagLev) to measure very small differences in density of solid diamagnetic objects suspended in a paramagnetic medium. Previous work in this field has shown that, while it is a convenient method, standard MagLev (i.e., where the direction of magnetization and gravitational force are parallel) cannot resolve differences in density mm) because (i) objects close in density prevent each other from reaching an equilibrium height due to hard contact and excluded volume, and (ii) using weaker magnets or reducing the magnetic susceptibility of the medium destabilizes the magnetic trap. The present work investigates the use of weak magnetic gradients parallel to the faces of the magnets as a means of increasing the sensitivity of MagLev without destabilization. Configuring the MagLev device in a rotated state (i.e., where the direction of magnetization and gravitational force are perpendicular) relative to the standard configuration enables simple measurements along the axes with the highest sensitivity to changes in density. Manipulating the distance of separation between the magnets or the lengths of the magnets (along the axis of measurement) enables the sensitivity to be tuned. These modifications enable an improvement in the resolution up to 100-fold over the standard configuration, and measurements with resolution down to 10(-6) g/cm(3). Three examples of characterizing the small differences in density among samples of materials having ostensibly indistinguishable densities-Nylon spheres, PMMA spheres, and drug spheres-demonstrate the applicability of rotated Maglev to measuring the density of small (0.1-1 mm) objects with high sensitivity. This capability will be useful in materials science, separations, and quality control of manufactured objects.

  4. Development of high magnetic fields for energy research

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, J.D.; Campbell, L.J.; Modler, R.; Movshovich, R. [Los Alamos National Lab., NM (United States); Lawrence, J.M. [Univ. of California, Irvine, CA (United States); Awschalom, D.D. [Univ. of California, Santa Barbara, CA (United States)

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The primary purpose of work has been to develop the scientific basis for DOE support of a program that would build a novel, nondestructive 100-tesla magnet that would be available as a user facility for cutting-edge, energy-related research and technology at very high magnetic fields.

  5. Coercive forms of sexual risk and associated violence perpetrated by male partners of female adolescents.

    Science.gov (United States)

    Silverman, Jay G; McCauley, Heather L; Decker, Michele R; Miller, Elizabeth; Reed, Elizabeth; Raj, Anita

    2011-03-01

    Partner violence is associated with STDs among female adolescents, but the mechanisms underlying this association remain unclear. Sexually coercive and deceptive behaviors of male partners that increase female STD risk may be factors in this relationship. A sample of 356 females aged 14-20 who attended adolescent health clinics in Greater Boston between April and December 2006 were assessed for physical and sexual violence perpetrated by male partners and for exposure to sexual risk factors. Adjusted logistic regression models were used to examine the associations between intimate partner violence and standard sexual risk behaviors (e.g., multiple partnerships) and coercive or deceptive sexual risk factors (e.g., coerced condom nonuse). More than two-fifths of the sample had experienced intimate partner violence. In adjusted analyses, adolescents reporting intimate partner violence were more likely than others to report standard sexual risk behaviors--multiple partners, anal sex and unprotected anal sex (odds ratios, 1.7-2.2). They also were more likely to report coercive or deceptive sexual risk factors--partner sexual infidelity, fear of requesting condom use, negative consequences of condom request, and coerced condom nonuse (2.9-5.3). The high prevalence of intimate partner violence against young women attending adolescent clinics strongly indicates the need to target this population for abuse-related interventions. This need is underlined by the observed association between partner violence and sexual risk involving coercion or deception by male partners. Clinic-based STD and pregnancy prevention efforts should include assessment of sexual risk factors that are beyond the control of young women, particularly for those experiencing abuse. Copyright © 2011 by the Guttmacher Institute.

  6. The effect of surfactant addition on high-energy milling upon the magnetic properties and microstructure of the Pr-Fe-B HDDR magnetic powders; Efeito da adicao de surfactantes nas propriedades e microestrutura de pos magneticos a base de Pr-Fe-B obtidos via HDDR e moagem de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Santos, P.B.; Silva, S.C.; Faria, R.N.; Takiishia, H., E-mail: pbsantos@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2010-07-01

    Nanomagnetic powders based on the composition Pr{sub 12}Fe{sub 65.9}Co{sub 16}B{sub 6}Nb{sub 0.1} have been obtained from using (a) the hydrogenation, disproportionation, desorption and recombination (HDDR) process; (b) by varying of milling time and (c) with the addition of an oleic acid as a surfactant. The latter has been used to enhance milling condition by preventing the agglomeration of particles and hence to improve the intrinsic coercivity of the material. High-energy mechanical milling has been used to yield magnetic nanoparticles. Powders were characterized magnetically using vibrating sample magnetometer (VSM) and microstructurally by Scanning Electron Microscopy (SEM), Field Emission Gun SEM (FEG-SEM) and X-ray diffraction. (author)

  7. FeSiBP bulk metallic glasses with high magnetization and excellent magnetic softness

    Science.gov (United States)

    Makino, Akihiro; Kubota, Takeshi; Chang, Chuntao; Makabe, Masahiro; Inoue, Akihisa

    Fe-based amorphous alloy ribbons are one of the major soft magnetic materials, because of their superior magnetic properties such as the relatively high saturation magnetization ( Js) of 1.5-1.6 T and good magnetic softness. However, the preparation of the ordinary amorphous magnetic alloys requires cooling rates higher than 10 4 K/s due to the low glass-forming ability (GFA) and thus restricts the material outer shape. Recently, Fe-metalloid-based bulk metallic glasses (BMGs) containing glass-forming elements such as Al, Ga, Nb, Mo, Y and so forth have been developed. These alloys have high GFA, leading to the formation of BMG rod with diameters of mm-order. However, the glass-forming metal elements in BMGs result in a remarkable decrease in magnetization. Basically, Js depends on Fe content; hence, high Js requires high Fe content in the Fe-based amorphous alloys or BMGs. On the other hand, high GFA requires a large amount of glass-forming elements in the alloys, which results in lower Fe content. Therefore, in substances, the coexistence of high Js and high GFA is difficult. Since this matter should be immensely important from academia to industry in the material field, a great deal of effort has been devoted; however, it has remained unsolved for many years. In this paper, we present a novel Fe-rich FeSiBP BMG with high Js of 1.51 T comparable to the ordinary Fe-Si-B amorphous alloy now in practical use as well as with high GFA leading to a rod-shaped specimen of 2.5 mm in diameter, obtained by Cu-mold casting in air.

  8. Angular and geometry dependence of coercivity and remanence nickel nanotube isolated

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, J.L.; Davila, Y.G.; Garcia, R.P.; Del Toro, A.D.; Martins, I.G.; Hernandez, E.P. [Universidade Federal de Pernambuco (UFPE), PE (Brazil)

    2016-07-01

    , where we vary the angle of the magnetic field applied to the ferromagnetic system. We investigated the role of geometry in the coercivity and remanence of hysteresis curves, where we analyze the types of magnetization reversal modes that can appear in isolated nanotube system. (author)

  9. Homogenous BSCCO-2212 Round Wires for Very High Field Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Scott Campbell

    2012-06-30

    The performance demands on modern particle accelerators generate a relentless push towards higher field magnets. In turn, advanced high field magnet development places increased demands on superconducting materials. Nb3Sn conductors have been used to achieve 16 T in a prototype dipole magnet and are thought to have the capability for {approx}18 T for accelerator magnets (primarily dipoles but also higher order multipole magnets). However there have been suggestions and proposals for such magnets higher than 20 T. The High Energy Physics Community (HEP) has identified important new physics opportunities that are enabled by extremely high field magnets: 20 to 50 T solenoids for muon cooling in a muon collider (impact: understanding of neutrinos and dark matter); and 20+ T dipoles and quadrupoles for high energy hadron colliders (impact: discovery reach far beyond present). This proposal addresses the latest SBIR solicitation that calls for grant applications that seek to develop new or improved superconducting wire technologies for magnets that operate at a minimum of 12 Tesla (T) field, with increases up to 15 to 20 T sought in the near future (three to five years). The long-term development of accelerator magnets with fields greater than 20 T will require superconducting wires having significantly better high-field properties than those possessed by current Nb{sub 3}Sn or other A15 based wires. Given the existing materials science base for Bi-2212 wire processing, we believe that Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212) round wires can be produced in km-long piece lengths with properties suitable to meet both the near term and long term needs of the HEP community. The key advance will be the translation of this materials science base into a robust, high-yield wire technology. While the processing and application of A15 materials have advanced to a much higher level than those of the copper oxide-based, high T{sub c} (HTS) counterparts, the HTS materials have

  10. Radiofrequency solutions in clinical high field magnetic resonance

    NARCIS (Netherlands)

    Andreychenko, A.|info:eu-repo/dai/nl/341697672

    2013-01-01

    Magnetic resonance imaging (MRI) and spectroscopy (MRS) benefit from the sensitivity gain at high field (≥7T). However, high field brings also certain challenges associated with growing frequency and spectral dispersion. Frequency growth results in degraded performance of large volume radiofrequency

  11. Optical fiber distributed sensing for high temperature superconductor magnets

    Science.gov (United States)

    Scurti, Federico; Schwartz, Justin

    2017-04-01

    Over the last two decades, high temperature superconductors (HTS) have achieved performance and technical maturity that make them an enabling technology or an attractive solution for a number of applications like electric motors and generators, particle accelerators and fusion magnets. One of the remaining challenges that hinders a wide use of HTS and needs to be solved is quench detection, since conventional voltage based quench detection puts HTS magnets at risk. In this work we have developed and experimentally investigated the application of Rayleigh-backscattering interrogated optical fibers (RIOF) to the detection of normal zones in superconducting magnets. Different ways to integrate optical fibers into magnets are explored and the earlier detection of RIOF compared to voltage is demonstrated.

  12. Coercive Sanctions and International Conflicts: A Sociological Theory

    DEFF Research Database (Denmark)

    Jaeger, Mark Daniel

    international sanctions work, and more substantially, what are the social conditions within sanctions conflicts that are conducive to either cooperation or non-cooperation? Arguing that coercive sanctions and international conflicts are socially-constructed facts, the book explores the processes involved...... in the formation of meaning that sanctions and conflicts acquire. From a sociological perspective, the answer to the question depends on the meaning that sanctions acquire for opponents in on-going conflict. On the other hand, sanctions contribute differently to the way in which opponents construct conflict...

  13. Coercive Power Scenarios in the Classes Taught by Student Teachers

    OpenAIRE

    Lojdová Kateřina; Vlčková Kateřina

    2015-01-01

    Our aim is to describe how coercive power is negotiated, used, and perceived by student teachers and their students in lower secondary classes (ISCED 2A). Power is an ability of a person to influence opinions, values, and behaviour of others (McCroscey, 2006). In our study we use the most influential, traditional typology of power as a relational phenomenon by French and Raven (1959). It distinguishes teacher‘s power in relation to a (by students perceived) principle on which it is based on, ...

  14. Synthesis, structural, magnetic and dielectric properties of zirconium copper doped M-type calcium strontium hexaferrites

    Energy Technology Data Exchange (ETDEWEB)

    Ashiq, Muhammad Naeem; Qureshi, Raheela Beenish [Institute of Chemical Sciences, Bahauddin Zakariya University, Multan 60800 (Pakistan); Malana, Muhammad Aslam, E-mail: draslammalana@gmail.com [Institute of Chemical Sciences, Bahauddin Zakariya University, Multan 60800 (Pakistan); Ehsan, Muhammad Fahad [National Center for Nanoscience and Technology (NCNST), 11 Beiyitiao, Zhongguawn, Beijing (China)

    2014-12-25

    Highlights: • Particle size of these samples is suitable for high density recording media. • The samples have coercivity suitable for longitudinal magnetic recording media. • The sample (x = 0.8) has dielectric constant useful for high frequency applications. - Abstract: Zirconium copper substituted calcium strontium hexagonal ferrites with composition Ca{sub 0.5}Sr{sub 0.5}Fe{sub 12−2x}Zr{sub x}Cu{sub x}O{sub 19} (x = 0.0, 0.2, 0.4, 0.6, 0.8) have been synthesized by the chemical co precipitation procedure. These compounds were characterized by X-ray diffraction, thermogravimetry and scanning electron microscopy. Dielectric and magnetic properties of these hexaferrites were also explored. XRD analysis confirmed the single hexagonal phase of all the compounds and the average crystallite size was between 37 and 47 nm. The dielectric parameters show relaxation behaviour at higher frequencies. The values of dielectric parameters increase with dopants. In the range of magnetic field studied, the saturation magnetization decreases as the dopant contents increase which may be due to the nonmagnetic character of the substituents. The coercivity of the Zr–Cu doped derivatives of strontium calcium hexaferrites is increased up to x = 0.2 and then decreased. The values of coercivity are above 600 Oe which make them suitable materials for use in industries in longitudinal magnetic recording media.

  15. DMSP observations of high latitude Poynting flux during magnetic storms

    Science.gov (United States)

    Huang, Cheryl Y.; Huang, Yanshi; Su, Yi-Jiun; Hairston, Marc R.; Sotirelis, Thomas

    2017-11-01

    Previous studies have demonstrated that energy can enter the high-latitude regions of the Ionosphere-Thermosphere (IT) system on open field lines. To assess the extent of high-latitude energy input, we have carried out a study of Poynting flux measured by the Defense Meteorological Satellite Program (DMSP) satellites during magnetic storms. We report sporadic intense Poynting fluxes measured by four DMSP satellites at polar latitudes during two moderate magnetic storms which occurred in August and September 2011. Comparisons with a widely used empirical model for energy input to the IT system show that the model does not adequately capture electromagnetic (EM) energy at very high latitudes during storms. We have extended this study to include more than 30 storm events and find that intense EM energy is frequently detected poleward of 75° magnetic latitude.

  16. Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4 thin films

    Science.gov (United States)

    Liu, X. H.; Liu, W.; Zhang, Z. D.

    2017-09-01

    We have systematically studied the evolution of magnetic properties, especially the coercivity and the remanence ratio in the vicinity of the Verwey transition temperature (TV), of high-quality epitaxial Fe3O4 thin films grown on MgO (001), MgAl2O4 (MAO) (001), and SrTiO3 (STO) (001) substrates. We observed rapid change of magnetization, coercivity, and remanence ratio at TV, which are consistent with the behaviors of resistivity versus temperature [ρ (T )] curves for the different thin films. In particular, we found quite different magnetic behaviors for the thin films on MgO from those on MAO and STO, in which the domain size and the strain state play very important roles. The coercivity is mainly determined by the domain size but the demagnetization process is mainly dependent on the strain state. Furthermore, we observed a reversal of remanence ratio at TV with thickness for the thin films grown on MgO: from a rapid enhancement for 40-nm- to a sharp drop for 200-nm-thick film, and the critical thickness is about 80 nm. Finally, we found an obvious hysteretic loop of coercivity (or remanence ratio) with temperature around TV, corresponding to the hysteretic loop of the ρ (T ) curve, in Fe3O4 thin film grown on MgO.

  17. Fast calculation of magnetic field distribution in magnetic gear for high torque application

    DEFF Research Database (Denmark)

    Zhang, Xiaoxu; Liu, Xiao; Song, Zhanfeng

    2016-01-01

    For applications demanding high torque and high reliability transmission, coaxial magnetic gear (CMG) may be a promising substitute of the mechanical gearbox. However, with the increasing of unit capacity, CMG tends to have a big size with large pole number, which would lead to heavy computation...... burden if finite element method (FEM) is employed. Analytical methods are therefore expected. To date, only the exact subdomain model is capable of precisely predicting the magnetic field behaviors in an analytical manner through solving a matrix equation. However, as pole number of the CMG increases...

  18. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    Energy Technology Data Exchange (ETDEWEB)

    Bouda, N. R., E-mail: nybouda@iastate.edu; Pritchard, J.; Weber, R. J.; Mina, M. [Department of Electrical and Computer engineering, Iowa State University, Ames, Iowa 50011 (United States)

    2015-05-07

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  19. Nanocomposite Nd-Y-Fe-B-Mo bulk magnets prepared by injection casting technique

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Shan [Magnetism Key Laboratory of Zhejiang Province, China Jiliang University, Hangzhou 310018 (China); Ahmad, Zubair [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Zhang, Pengyue [Magnetism Key Laboratory of Zhejiang Province, China Jiliang University, Hangzhou 310018 (China); Yan, Mi, E-mail: mse_yanmi@zju.edu.cn [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Zheng, Xiaomei [Magnetism Key Laboratory of Zhejiang Province, China Jiliang University, Hangzhou 310018 (China)

    2017-09-01

    Highlights: • Nanocomposite Nd{sub 7}Y{sub 6}Fe{sub 61}B{sub 22}Mo{sub 4} sheet magnets were synthesized by injection casting. • High coercivity of 1289 kA/m was obtained for the directly casted magnet. • Magnetic properties arise from magnetically exchange coupled soft and hard phases. - Abstract: The phase composition, magnetic and microstructural properties of Nd{sub 2}Fe{sub 14}B/(α-Fe, Fe{sub 3}B) nanocomposite magnets produced by injection casting technique have been studied. Magnetic hysteresis loop of the Nd{sub 7}Y{sub 6}Fe{sub 61}B{sub 22}Mo{sub 4} permanent magnet demonstrates the coercivity as high as 1289 kA/m. Electron microscopy elucidates a microstructure composed of magnetically soft α-Fe, Fe{sub 3}B and hard Nd{sub 2}Fe{sub 14}B/Y{sub 2}Fe{sub 14}B nanograins (20–50 nm) separated by ultra-thin grain boundary layer. The Henkel plot curve of the Nd{sub 7}Y{sub 6}Fe{sub 61}B{sub 22}Mo{sub 4} magnet yields the existence of exchange coupling interactions between soft and hard phases. Macroscopically large size sheet magnet is obtained due to high glass forming ability of the Nd{sub 7}Y{sub 6}Fe{sub 61}B{sub 22}Mo{sub 4} alloy derived from large atomic radius mismatch and negative enthalpy of alloy constituent elements. The high coercivity of the magnet is attributed to the magnetically hard phase increment, nucleation of reverse domains and the presence of thin grain boundary phase. Good magnetic properties such as remanence of 0.51 T, coercivity of 1289 kA/m and maximum energy product of 46.2 kJ/m{sup 3} are obtained in directly casted Nd{sub 7}Y{sub 6}Fe{sub 61}B{sub 22}Mo{sub 4} sheet magnets.

  20. Germany without Coercive Treatment in Psychiatry—A 15 Month Real World Experience

    Directory of Open Access Journals (Sweden)

    Martin Zinkler

    2016-03-01

    Full Text Available Coercive treatment with antipsychotic drugs was commonly used in German psychiatric institutions until it became a topic of substantial medical, legal and ethical controversy. In 2011 and 2012, several landmark decisions by Germany’s Constitutional Court and Federal Supreme Court challenged this practice in all but life-threatening emergencies. In March 2013, the new legal provisions governing coercive treatment took effect allowing coercive medication under stricter criteria. While mainstream psychiatry in Germany resumed the use of coercive medication, although less frequently than before 2012, there are examples where clinicians put an even greater emphasis on consensual treatment and did not return to coercive treatment. Data from a case study in a local mental health service suggest that the use of coercive medication could be made obsolete.

  1. Toward a Standard Approach to Operationalizing Coercive Control and Classifying Violence Types.

    Science.gov (United States)

    Hardesty, Jennifer L; Crossman, Kimberly A; Haselschwerdt, Megan L; Raffaelli, Marcela; Ogolsky, Brian G; Johnson, Michael P

    2015-08-01

    Coercive control is central to distinguishing between Johnson's (2008) 2 main types of intimate partner violence: (a) coercive controlling violence and (b) situational couple violence. Approaches to assessing coercive control, however, have been inconsistent. Using data from 2 projects involving divorcing mothers (N = 190), the authors compared common analytic strategies for operationalizing coercive control and classifying types of violence. The results establish advantages to measuring coercive control in terms of frequency versus number of tactics, illustrate the use of both hierarchical and k-means clustering methods to identify patterns of coercive control and evaluate clustering solutions, and offer a suggested cutoff for classifying violence types in general samples of separated women using the Dominance-Isolation subscale of the widely used Psychological Maltreatment of Women Inventory (Tolman, 1992). Finally, the authors demonstrate associations between types of violence and theoretically relevant variables, including frequency and severity of violence, harassment and violence after separation, fear, and perceived threat.

  2. Miniature high speed compressor having embedded permanent magnet motor

    Science.gov (United States)

    Zhou, Lei (Inventor); Zheng, Liping (Inventor); Chow, Louis (Inventor); Kapat, Jayanta S. (Inventor); Wu, Thomas X. (Inventor); Kota, Krishna M. (Inventor); Li, Xiaoyi (Inventor); Acharya, Dipjyoti (Inventor)

    2011-01-01

    A high speed centrifugal compressor for compressing fluids includes a permanent magnet synchronous motor (PMSM) having a hollow shaft, the being supported on its ends by ball bearing supports. A permanent magnet core is embedded inside the shaft. A stator with a winding is located radially outward of the shaft. The PMSM includes a rotor including at least one impeller secured to the shaft or integrated with the shaft as a single piece. The rotor is a high rigidity rotor providing a bending mode speed of at least 100,000 RPM which advantageously permits implementation of relatively low-cost ball bearing supports.

  3. Highly Charged Ions in Rare Earth Permanent Magnet Penning Traps

    CERN Document Server

    Guise, Nicholas D; Tan, Joseph N

    2013-01-01

    A newly constructed apparatus at the National Institute of Standards and Technology (NIST) is designed for the isolation, manipulation, and study of highly charged ions. Highly charged ions are produced in the NIST electron-beam ion trap (EBIT), extracted through a beamline that selects a single mass/charge species, then captured in a compact Penning trap. The magnetic field of the trap is generated by cylindrical NdFeB permanent magnets integrated into its electrodes. In a room-temperature prototype trap with a single NdFeB magnet, species including Ne10+ and N7+ were confined with storage times of order 1 second, showing the potential of this setup for manipulation and spectroscopy of highly charged ions in a controlled environment. Ion capture has since been demonstrated with similar storage times in a more-elaborate Penning trap that integrates two coaxial NdFeB magnets for improved B-field homogeneity. Ongoing experiments utilize a second-generation apparatus that incorporates this two-magnet Penning tra...

  4. Magnetic forces in high-Tc superconducting bearings

    Science.gov (United States)

    Moon, F. C.

    1991-01-01

    In September 1987, researchers at Cornell levitated a small rotor on superconducting bearings at 10,000 rpm. In April 1989, a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu307. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.

  5. Magnetic separation using high-T sub c superconductors

    CERN Document Server

    Bolt, L

    2001-01-01

    sensitivity of the high-T sub c material to magnetic fields. Finite elements modelling of the system has provided the framework for the quantitative analysis of the magnetic field distributions on the coil windings and the optimisation of the system configuration. The performance of the separator has been tested at 77 K with liquid nitrogen at atmospheric pressure, and at a temperature approx = 67 K by pumping liquid nitrogen at a pressure around 100 Torr. The highest field obtained in the air gap at 67 K was of 340 mT. Magnetic separators with an iron circuit have been in operation for many years in mineral industry, and there appear to be an opportunity of building machines with high-T sub c coils or retrofitting existing machines with high-T sub c coils to run them closer to saturation in a cheap and effective way. Superconductivity has found in magnetic separation one of its major industrial applications second only to magnetic resonance imaging. Low-T sub c superconducting coils have been employed in Hig...

  6. Renal ablation using magnetic resonance-guided high intensity focused ultrasound: Magnetic resonance imaging and histopathology assessment

    OpenAIRE

    Saeed, Maythem; Krug, Roland; Do, Loi; Steven W. Hetts; Wilson, Mark W.

    2016-01-01

    AIM: To use magnetic resonance-guided high intensity focused ultrasound (MRg-HIFU), magnetic resonance imaging (MRI) and histopathology for noninvasively ablating, quantifying and characterizing ablated renal tissue.

  7. Magnetically Regulated Gas Accretion in High-Redshift Galactic Disks

    Science.gov (United States)

    Birnboim, Yuval

    2009-09-01

    Disk galaxies are in hydrostatic equilibrium along their vertical axis. The pressure allowing for this configuration consists of thermal, turbulent, magnetic, and cosmic-ray components. For the Milky Way the thermal pressure contributes ~10% of the total pressure near the plane, with this fraction dropping toward higher altitudes. Out of the rest, magnetic fields contribute ~1/3 of the pressure to distances of ~3 kpc above the disk plane. In this Letter, we attempt to extrapolate these local values to high-redshift, rapidly accreting, rapidly star-forming disk galaxies and study the effect of the extra pressure sources on the accretion of gas onto the galaxies. In particular, magnetic field tension may convert a smooth cold-flow accretion to clumpy, irregular star formation regions and rates. The infalling gas accumulates on the edge of the magnetic fields, supported by magnetic tension. When the mass of the infalling gas exceeds some threshold mass, its gravitational force cannot be balanced by magnetic tension anymore, and it falls toward the disk's plane, rapidly making stars. Simplified estimations of this threshold mass are consistent with clumpy star formation observed in SINS, UDF, GOODS, and GEMS surveys. We discuss the shortcomings of pure hydrodynamic codes in simulating the accretion of cold flows into galaxies, and emphasize the need for magnetohydrodynamic simulations.

  8. High Force Magnetic Levitation Using Magnetized Superconducting Bulks as a Field Source for Bearing Applications

    Science.gov (United States)

    Patel, A.; Giunchi, G.; Albisetti, A. Figini; Shi, Y.; Hopkins, S. C.; Palka, R.; Cardwell, D. A.; Glowacki, B. A.

    The ability of high temperature superconducting bulks to trap magnetic fields of several tesla allows them to generate very high levitation force. This paper reports the development of a bulk-bulk superconducting rotary bearing design which uses superconducting bulks on both the rotor and the stator. An evaluation is made of the effectiveness of pulsed fields for magnetizing bulks. Modeling of the bulks using the perfectly trapped flux model is also reported to assess the limits of the bearing design. The results demonstrate the feasibility of a (RE)BCO-MgB2 bulk bearing capable of force densities of the order of 100N/cm2. The design and construction of a unique system capable of magnetizing a 25 mm (RE)BCO bulk and measuring levitation force between this bulk and a coaxial MgB2 hollow cylinder is outlined.

  9. [Compulsory hospital admission - coercive measures in medical care].

    Science.gov (United States)

    Meier-Allmendinger, Diana

    2009-08-01

    Any coercive medical intervention is a massive curtailment of the affected person's freedom that is in direct contradiction to their right to self-determination. This is why any such intervention must be laid on a solid legal and ethical foundation. Any decision to commit a person against their will for medical care will have to be made with due regard for both the institution's medical duty and society's interest in public safety. Any such decision must also involve careful consideration of whether the individual concerned is at acute risk of harming or injuring themselves or others as a result of their mental condition. Involuntary committal may be perceived as extremely insulting by the person concerned, who may feel that their right of self-determination has been violated; and at least for a limited period it will inevitably make them feel that they are not being treated like or regarded as an adult. Hence, the following ethical questions arise: Is it justified to suspend an individual's right of self-determination - if only in terms of their place of residence - by committing them for medical treatment and care? And how can such coercive committal be reconciled with the ethical medical principles of autonomy, beneficence, justice and non-maleficence? There are no stock answers or checklist answers to these questions. Whether a committal is warranted must ultimately be decided on a case-by-case basis by thoroughly assessing, weighting and comparing the various principles and considerations involved.

  10. A battered women's movement perspective of Coercive Control.

    Science.gov (United States)

    Arnold, Gretchen

    2009-12-01

    In Coercive Control, Evan Stark calls on battered women's activists to reorient their understanding of abusive relationships. Rather than being primarily about physical violence, he maintains, domestic violence is better conceptualized as men's attempts to destroy women's autonomy and reinstate patriarchy in intimate relationships. His analysis suggests important changes to defending battered women in court, modifications to the kinds of support services the movement provides for battered women, and changes in the laws and law enforcement regarding battering. Stark also maintains that, to end coercive control, the battered women's movement must renew its commitment not only to ensuring the safety of individual women but also to attaining the feminist goal of substantive freedom and equality for women in both public and private life. I contend that Stark's reframing of woman abuse is useful for battered women's advocates and may, in some cases but not in others, lead to more effective practices in battered women's programs. At the same time, it is likely to complicate activists' efforts to mobilize public opinion, resources, and public policy to address the problem of woman abuse.

  11. Special-Purpose High-Torque Permanent-Magnet Motors

    Science.gov (United States)

    Doane, George B., III

    1995-01-01

    Permanent-magnet brushless motors that must provide high commanded torques and satisfy unusual heat-removal requirement are developed. Intended for use as thrust-vector-control actuators in large rocket engines. Techniques and concepts used to design improved motors for special terrestrial applications. Conceptual motor design calls for use of rotor containing latest high-energy-product rare-earth permanent magnets so that motor produces required torque while drawing smallest possible currents from power supply. Torque generated by electromagnetic interaction between stator and permanent magnets in rotor when associated electronic circuits applied appropriately temporally and spatially phased currents to stator windings. Phase relationships needed to produce commanded torque computed in response to torque command and to electronically sensed angular position of rotor relative to stator.

  12. High-Energy Electron Confinement in a Magnetic Cusp Configuration

    Directory of Open Access Journals (Sweden)

    Jaeyoung Park

    2015-06-01

    Full Text Available We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad’s work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β. This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

  13. Excess use of coercive measures in psychiatry among migrants compared with native Danes

    DEFF Research Database (Denmark)

    Nørredam, Marie Louise; Garcia-Lopez, A; Keiding, N

    2010-01-01

    Norredam M, Garcia-Lopez A, Keiding N, Krasnik A. Excess use of coercive measures in psychiatry among migrants compared with native Danes.Objective: To investigate differences in risk of compulsory admission and other coercive measures in psychiatric emergencies among refugees and immigrants....... This was most striking for refugee men (RR = 2.00; 95%CI: 1.53; 2.61) and immigrant women (RR = 1.73; 95%CI: 1.45; 2.60). Moreover, refugees and immigrants experienced higher frequencies of other coercive measures during hospitalisation compared with native Danes. Conclusion: Coercive measures in psychiatry...

  14. Voltage Controlled Perpendicular Magnetic Anisotropy.

    Science.gov (United States)

    Noviasky, Nicholas; Sabirianov, Ildar; Cao, Shi; Zhang, Xiaozhe; Sokolov, Andrei; Kirianov, Eugene; Dowben, Peter; Ilie, Carolina C.; University of Nebraska at Lincoln Team; State University of New York at Oswego Collaboration

    Here we report the voltage controlled perpendicular magnetic anisotropy of a multilayer stack composed of P-type silicon substrate/ Gd2O3/ Co/ Pt grown by pulsed laser deposition (PLD) under ultra-high vacuum conditions. For examination of the voltage effect on magnetic properties of the samples, we performed magneto optical Kerr effect (MOKE) measurements. The results show a clear inverse relationship between voltage and coercivity. The exchange of oxygen ions which occurs at the interface between gadolinium oxide and cobalt may increase the cobalt oxide concentration within the optical interface layer. One potential application for this research could be the creation of a voltage controlled magnetic tunneling junction memory storage device. Proper implementation may be able to combine non-volatility with higher areal densities and low power consumption. NSF Research Experience for Faculty and Students at Undergraduate Institutions Program, UNL- MRSEC.

  15. Experimental Contribution to High Precision Characterization of Magnetic Forces in Active Magnetic Bearings

    DEFF Research Database (Denmark)

    Kjølhede, Klaus; Santos, Ilmar

    2006-01-01

    contribution of the work is the characterization of magnetic forces by using two different experimental approaches. Such approaches are investigated and described in detail. A special test rig is designed where the 4 pole - AMB is able to generate forces up to 1900 N. The high precision characterization...

  16. Survey of high field superconducting material for accelerator magnets

    Energy Technology Data Exchange (ETDEWEB)

    Scahlan, R.; Greene, A.F.; Suenaga, M.

    1986-05-01

    The high field superconductors which could be used in accelerator dipole magnets are surveyed, ranking these candidates with respect to ease of fabrication and cost as well as superconducting properties. Emphasis is on Nb/sub 3/Sn and NbTi. 27 refs., 2 figs. (LEW)

  17. Modelling of the magnetic and magnetostrictive properties of high ...

    Indian Academy of Sciences (India)

    This high correspondence of experimental and modelled characteristics is confirmed by the fact that Pearson r2 indicator is surpassing 99%. 4. Modelling of the magnetostrictive properties. In a simplified model, the magnetostriction λ can be calculated from quadratic equation as a function of magnetization M [11]:. Table 1.

  18. National Program on High Field Accelerator Magnet R&D

    Energy Technology Data Exchange (ETDEWEB)

    Apollinari, G. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Cooley, L. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Zlobin, A. V. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Caspi, S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gourlay, S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Prestemon, S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Larbalestier, D. [National High Magnetic Field Laboratory, Tallahassee, FL (United States); Gupta, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wanderer, P. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2014-09-26

    A National High-Field Magnet (HFM) Program is proposed as a thrust of the updated DOE-HEP General Accelerator R&D Program. The program responds to Recommendation 24 of the 2014 Particle Physics Project Prioritization Panel (P5) Report.

  19. Self-propagating high temperature synthesis and magnetic ...

    Indian Academy of Sciences (India)

    Ni–Zn ferrite powders were synthesized by self-propagating high temperature synthesis (SHS) method. X-ray diffraction, TEM and vibrating sample magnetometry (VSM) were used to characterize the phase composition, microstructure and magnetic properties of the combustion products. The effect of the combustion ...

  20. Advances in high-gradient magnetic fishing for bioprocessing

    DEFF Research Database (Denmark)

    Goncalves Gomes, Claudia Sofia

    2006-01-01

    High-gradient magnetic fishing” (HGMF) er en metode til processering af fødestrømme med biologiske molekyler. HGMF integrerer brugen af superparamagnetiske adsorbenter med separation og processering med høj-gradient magnetisk separation (HGMS) i et magnetisk filter. Adsorbenterne er uporøse og m...

  1. Magnetic forces in high-T(sub c) superconducting bearings

    Science.gov (United States)

    Moon, F. C.

    1990-01-01

    In September 1987 research at Cornell levitated a small rotor on superconducting bearing at 10,000 rpm. In April 1989 a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu3O7. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic drag forces of a magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the drag force reaches a constant value, independent of the speed. Dampling of lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.

  2. Magnetic behavior of as-deposited and annealed CoFe and CoFeCu nanowire arrays by ac-pulse electrodeposition

    Science.gov (United States)

    Ramazani, A.; Almasi-Kashi, M.; Golafshan, E.; Arefpour, M.

    2014-09-01

    CoFe and CoFeCu self-organized alloy nanowires were grown into anodic aluminum oxide template by potentiostatic mode of ac-pulse electrodeposition technique and subsequently annealed at 580 °C. The influence of bath composition, off-time between pulses and annealing treatment on the Cu content, microstructure and magnetic properties of CoFeCu nanowire arrays have been discussed. Increasing the off-time between pulses decreased the coercivity and saturation magnetization of the CoFeCu nanowires due to substitution of Co and Fe with Cu atoms which resulted in electroless process. Coercivity and squareness of the annealed samples increased due to improvement of samples crystallinity. Magnetic measurements showed high perpendicular magnetic anisotropy of the nanowires with easy axis parallel to nanowires axis. X-ray diffraction results indicated that annealed CoFeCu nanowires were polycrystalline with two distinct CoFe and Cu phases.

  3. Magnetic liposomes for colorectal cancer cells therapy by high-frequency magnetic field treatment

    Science.gov (United States)

    Hardiansyah, Andri; Huang, Li-Ying; Yang, Ming-Chien; Liu, Ting-Yu; Tsai, Sung-Chen; Yang, Chih-Yung; Kuo, Chih-Yu; Chan, Tzu-Yi; Zou, Hui-Ming; Lian, Wei-Nan; Lin, Chi-Hung

    2014-09-01

    In this study, we developed the cancer treatment through the combination of chemotherapy and thermotherapy using doxorubicin-loaded magnetic liposomes. The citric acid-coated magnetic nanoparticles (CAMNP, ca. 10 nm) and doxorubicin were encapsulated into the liposome (HSPC/DSPE/cholesterol = 12.5:1:8.25) by rotary evaporation and ultrasonication process. The resultant magnetic liposomes ( ca. 90 to 130 nm) were subject to characterization including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), zeta potential, Fourier transform infrared (FTIR) spectrophotometer, and fluorescence microscope. In vitro cytotoxicity of the drug carrier platform was investigated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using L-929 cells, as the mammalian cell model. In vitro cytotoxicity and hyperthermia (inductive heating) studies were evaluated against colorectal cancer (CT-26 cells) with high-frequency magnetic field (HFMF) exposure. MTT assay revealed that these drug carriers exhibited no cytotoxicity against L-929 cells, suggesting excellent biocompatibility. When the magnetic liposomes with 1 μM doxorubicin was used to treat CT-26 cells in combination with HFMF exposure, approximately 56% cells were killed and found to be more effective than either hyperthermia or chemotherapy treatment individually. Therefore, these results show that the synergistic effects between chemotherapy (drug-controlled release) and hyperthermia increase the capability to kill cancer cells.

  4. Thermal aging of melt-spun NdFeB magnetic powder in hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Pinkerton, Frederick E., E-mail: frederick.e.pinkerton@gm.com [Chemical and Materials Systems Laboratory, General Motors Research and Development Center, Warren, MI 48092 (United States); Balogh, Michael P.; Ellison, Nicole [Chemical and Materials Systems Laboratory, General Motors Research and Development Center, Warren, MI 48092 (United States); Foto, Aldo [Element Materials Technology Wixom, Inc (United States); Sechan, Martin; Tessema, Misle M.; Thompson, Margarita P. [Powertrain Materials/Fluids/AMPPD Engineering and Labs, GFL VE/PT Materials Engineering, General Motors LLC, Pontiac, MI 48340 (United States)

    2016-11-01

    High energy product neodymium-iron-boron (NdFeB) magnets are the premier candidate for demanding electrified vehicle traction motor applications. Injection molded (IM) or compression molded (CM) magnets made using NdFeB powders are promising routes to improve motor efficiency, cost, and manufacturability. However, IM and CM NdFeB magnets are susceptible to substantial thermal aging losses at motor operating temperatures when exposed to the automatic transmission fluid (ATF) used as a lubricant and cooling medium. The intrinsic coercivity H{sub ci} of NdFeB IM and CM magnets degrades by as much as 18% when aged for 1000 h in ATF at 150 °C, compared to a 3% loss when aged in air. Here we report aging studies of rapidly quenched NdFeB powder in air, ATF, and H{sub 2} gas. Expansion of the NdFeB crystal lattice in both ATF and H{sub 2} identified hydrogen dissociated from the ATF during aging and diffused into the primary NdFeB phase as the probable cause of the coercivity loss of IM and CM magnets. - Highlights: • Injection molded NdFeB magnets age rapidly in automatic transmission fluid (ATF). • Coercivity loss is not due to direct chemical reaction between ATF and the powder. • Chemical reaction with the binder does not play a major role in aging. • Hydrogen dissociates from ATF and diffuses into Nd{sub 2}Fe{sub 14}B, reducing coercivity.

  5. Brightness of Solar Magnetic Elements As a Function of Magnetic Flux at High Spatial Resolution

    Science.gov (United States)

    Kahil, F.; Riethmüller, T. L.; Solanki, S. K.

    2017-03-01

    We investigate the relationship between the photospheric magnetic field of small-scale magnetic elements in the quiet-Sun (QS) at disk center and the brightness at 214, 300, 313, 388, 397, and 525.02 nm. To this end, we analyzed spectropolarimetric and imaging time series acquired simultaneously by the Imaging Magnetograph eXperiment magnetograph and the SuFI filter imager on board the balloon-borne observatory {{S}}{{UNRISE}} during its first science flight in 2009, with high spatial and temporal resolution. We find a clear dependence of the contrast in the near ultraviolet and the visible on the line-of-sight component of the magnetic field, B LOS, which is best described by a logarithmic model. This function effectively represents the relationship between the Ca ii H-line emission and B LOS and works better than the power-law fit adopted by previous studies. This, along with the high contrast reached at these wavelengths, will help with determining the contribution of small-scale elements in the QS to the irradiance changes for wavelengths below 388 nm. At all wavelengths, including the continuum at 525.40 nm, the intensity contrast does not decrease with increasing B LOS. This result also strongly supports the fact that {{S}}{{UNRISE}} has resolved small strong magnetic field elements in the internetwork, resulting in constant contrasts for large magnetic fields in our continuum contrast at 525.40 nm versus the B LOS scatterplot, unlike the turnover obtained in previous observational studies. This turnover is due to the intermixing of the bright magnetic features with the dark intergranular lanes surrounding them.

  6. Dynamo Enhancement and Mode Selection Triggered by High Magnetic Permeability

    Science.gov (United States)

    Kreuzahler, S.; Ponty, Y.; Plihon, N.; Homann, H.; Grauer, R.

    2017-12-01

    We present results from consistent dynamo simulations, where the electrically conducting and incompressible flow inside a cylinder vessel is forced by moving impellers numerically implemented by a penalization method. The numerical scheme models jumps of magnetic permeability for the solid impellers, resembling various configurations tested experimentally in the von Kármán sodium experiment. The most striking experimental observations are reproduced in our set of simulations. In particular, we report on the existence of a time-averaged axisymmetric dynamo mode, self-consistently generated when the magnetic permeability of the impellers exceeds a threshold. We describe a possible scenario involving both the turbulent flow in the vicinity of the impellers and the high magnetic permeability of the impellers.

  7. Magnetization Measurements of High-Jc Nb3Sn strands

    CERN Document Server

    Bordini, B; Alknes, P; Ballarino, A; Bottura, L; Oberli, L

    2013-01-01

    High critical current density Nb3Sn wires (Jc > 2500 A/mm2 at 4.2 K and 12 T) are the conductors considered for next generation accelerator magnets. At present, the large magnetization of these strands is a concern within the scientific community because of the impact it might have on the magnet field quality. In order to characterize the magnetic behavior of these wires, an extensive campaign of magnetization measurements was launched at CERN. Powder In Tube (PIT) strands by Bruker-EAS and Restacked Rod Process (RRP®) strands by Oxford Superconducting Technology (OST) were measured between 0 T and 10.5 T at different temperatures (ranging from 1.9 K to 14.5 K). The samples, based on strands with different sub-elements dimensions (35 to 80 μm), were measured with a Vibrating Sample Magnetometer (VSM). The experimental data were analyzed to: 1) calculate the effective filament size and the optimal parameters for the pinning force scaling law; 2) define the field-temperature region where there are flux...

  8. Study of High-Efficiency Motors Using Soft Magnetic Cores

    Science.gov (United States)

    Tokoi, Hirooki; Kawamata, Shoichi; Enomoto, Yuji

    We have been developed a small and highly efficient axial gap motor whose stator core is made of a soft magnetic core. First, the loss sensitivities to various motor design parameters were evaluated using magnetic field analysis. It was found that the pole number and core dimensions had low sensitivity (≤ 2.2dB) in terms of the total loss, which is the sum of the copper loss and the iron losses in the stator core and the rotor yoke respectively. From this, we concluded that to improve the motor efficiency, it is essential to reduce the iron loss in the rotor yoke and minimize other losses. With this in mind, a prototype axial gap motor is manufactured and tested. The motor has four poles and six slots. The motor is 123mm in diameter and the axial length is 47mm. The rotor has parallel magnetized magnets and a rotor yoke with magnetic steel sheets. The maximum measured motor efficiency is 93%. This value roughly agrees with the maximum calculated efficiency of 95%.

  9. High temperature superconducting axial field magnetic coupler: realization and test

    Science.gov (United States)

    Belguerras, L.; Mezani, S.; Lubin, T.; Lévêque, J.; Rezzoug, A.

    2015-09-01

    Contactless torque transmission through a large airgap is required in some industrial applications in which hermetic isolation is necessary. This torque transmission usually uses magnetic couplers, whose dimension strongly depends on the airgap flux density. The use of high temperature superconducting (HTS) coils to create a strong magnetic field may constitute a solution to reduce the size of the coupler. It is also possible to use this coupler to replace a torque tube in transmitting the torque produced by a HTS motor to its load. This paper presents the detailed construction and tests of an axial field HTS magnetic coupler. Pancake coils have been manufactured from BSCCO tape and used in one rotor of the coupler. The second rotor is mainly composed of NdFeB permanent magnets. Several tests have been carried out showing that the constructed coupler is working properly. A 3D finite element (FE) model of the studied coupler has been developed. Airgap magnetic field and torque measurements have been carried out and compared to the FE results. It has been shown that the measured and the computed quantities are in satisfactory agreement.

  10. DR 21(OH): A HIGHLY FRAGMENTED, MAGNETIZED, TURBULENT DENSE CORE

    Energy Technology Data Exchange (ETDEWEB)

    Girart, J. M.; Frau, P. [Institut de Ciencies de l' Espai, (CSIC-IEEC), Campus UAB, Facultat de Ciencies, C5p 2, E-08193 Bellaterra, Catalonia (Spain); Zhang, Q. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Koch, P. M.; Tang, Y.-W.; Lai, S.-P.; Ho, P. T. P. [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Qiu, K., E-mail: girart@ice.cat [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

    2013-07-20

    We present high angular resolution observations of the massive star-forming core DR21(OH) at 880 {mu}m using the Submillimeter Array (SMA). The dense core exhibits an overall velocity gradient in a Keplerian-like pattern, which breaks at the center of the core where SMA 6 and SMA 7 are located. The dust polarization shows a complex magnetic field, compatible with a toroidal configuration. This is in contrast with the large, parsec-scale filament that surrounds the core, where there is a smooth magnetic field. The total magnetic field strengths in the filament and in the core are 0.9 and 2.1 mG, respectively. We found evidence of magnetic field diffusion at the core scales, far beyond the expected value for ambipolar diffusion. It is possible that the diffusion arises from fast magnetic reconnection in the presence of turbulence. The dynamics of the DR 21(OH) core appear to be controlled energetically in equal parts by the magnetic field, magnetohydrodynamic turbulence, and the angular momentum. The effect of the angular momentum (this is a fast rotating core) is probably causing the observed toroidal field configuration. Yet, gravitation overwhelms all the forces, making this a clear supercritical core with a mass-to-flux ratio of {approx_equal} 6 times the critical value. However, simulations show that this is not enough for the high level of fragmentation observed at 1000 AU scales. Thus, rotation and outflow feedback are probably the main causes of the observed fragmentation.

  11. Large coercivity and unconventional exchange coupling in manganese-oxide-coated manganese—gallium nanoparticles

    Science.gov (United States)

    Feng, Jun-Ning; Liu, Wei; Geng, Dian-Yu; Ma, Song; Yu, Tao; Zhao, Xiao-Tian; Dai, Zhi-Ming; Zhao, Xin-Guo; Zhang, Zhi-Dong

    2014-08-01

    The microstructures and magnetic properties of nanoparticles, each composed of an antiferromagnetic (AFM) manganese-oxide shell and a ferromagnetic-like core of manganese—gallium (MnGa) compounds, are studied. The core-shell structure is confirmed by transmission electron microscope (TEM). The ferromagnetic-like core contains three kinds of MnGa binary compounds, i.e., ferrimagnetic (FI) D022-type Mn3Ga, ferromagnetic (FM) Mn8Ga5, and AFM D019-type Mn3Ga, of which the first two correspond respectively to a hard magnetic phase and to a soft one. Decoupling effect between these two phases is found at low temperature, which weakens gradually with increasing temperature and disappears above 200 K. The exchange bias (EB) effect is observed simultaneously, which is caused by the exchange coupling between the AFM shell and FM-like core. A large coercivity of 6.96 kOe (1 Oe = 79.5775 A·m-1) and a maximum EB value of 0.45 kOe are achieved at 300 K and 200 K respectively.

  12. Anomalous magneto-structural behavior of MnBi explained: A path towards an improved permanent magnet

    Directory of Open Access Journals (Sweden)

    N. A. Zarkevich

    2014-03-01

    Full Text Available Low-temperature MnBi (hexagonal NiAs phase exhibits anomalies in the lattice constants (a, c and bulk elastic modulus (B below 100 K, spin reorientation and magnetic susceptibility maximum near 90 K, and, importantly for high-temperature magnetic applications, an increasing coercivity (unique to MnBi above 180  K. We calculate the total energy and magneto-anisotropy energy (MAE versus (a, c using DFT+U methods. We reproduce and explain all the above anomalies. We predict that coercivity and MAE increase due to increasing a, suggesting means to improve MnBi permanent magnets.

  13. Coercive Therapy in East and West: A Brief Review

    Directory of Open Access Journals (Sweden)

    Mohammad Jafar Bahredar

    2009-04-01

    Full Text Available "nAbstract: The physician-patient relationship has been undergoing significant changes in recent decades in Western countries. Taking a client-centered approach, society has given more autonomy and freedom to patients. The patient is regarded as a consumer who is looking for the best and most scientific approach and is free to choose among different methods of treatment. The role of the physician is only a guiding role. On the other hand, in Eastern countries, we still experience a parent-child relationship in the therapeutic setting. Eastern patients expect direct advice from their physicians and the family has an important role in decision-making. An approach which is considered coercive in Western countries could still be a useful and acceptable one in Eastern culture. The main goal of the authors in this paper is comparison of different attitudes toward this issue in Eastern and Western cultures.

  14. Effects of Video Feedback on Early Coercive Parent–Child Interactions: The Intervening Role of Caregivers’ Relational Schemas

    Science.gov (United States)

    Smith, Justin D.; Dishion, Thomas J.; Moore, Kevin J.; Shaw, Daniel S.; Wilson, Melvin N.

    2013-01-01

    Objective We examined the effect of adding a video feedback intervention component to the assessment feedback session of the Family Check-Up intervention (FCU; Dishion & Stormshak, 2007). We hypothesized that the addition of video feedback procedures during the FCU feedback at child age 2 would have a positive effect on caregivers’ negative relational schemas of their child, which in turn would mediate reductions in observed coercive caregiver-child interactions assessed at age 5. Method We observed the caregiver-child interaction videotapes of 79 high-risk families with toddlers exhibiting clinically significant problem behaviors. A quasi-random sample of families were provided with direct feedback on their interactions during the feedback session of the FCU protocol. Results Path analysis indicated that reviewing and engaging in feedback about videotaped age-2 assessment predicted reduced caregivers’ negative relational schemas of the child at age 3, which acted as an intervening variable on the reduction of observed parent–child coercive interactions recorded at age 5. Video feedback predicted improved family functioning over and above level of engagement in the FCU in subsequent years, indicating the important incremental contribution of using video feedback procedures in early family-based preventive interventions for problem behaviors. Conclusions Supportive video feedback on coercive family dynamics is an important strategy for promoting caregiver motivation to reduce negative attributions toward the child, which fuel coercive interactions. Our study also contributes to the clinical and research literature concerning coercion theory and effective intervention strategies by identifying a potential mechanism of change. PMID:23534831

  15. A new support structure for high field magnets

    CERN Document Server

    Hafalia, R R; Caspi, S; Dietderich, D R; Gourlay, S A; Hannaford, R; Lietzke, A F; Liggins, N; McInturff, A D; Sabbi, G L; Scanlan, R M; O'Neill, J; Swanson, J H

    2002-01-01

    Pre-stress of superconducting magnets can be applied directly through the magnet yoke structure. We have replaced the collar functionality in our 14 Tesla R&D Nb//3Sn dipole magnets with an assembly procedure based on an aluminum shell and bladders. Bladders, placed between the coil pack and surrounding yoke inside the shell, are pressurized up to 10 ksi left bracket 70 MPa right bracket to create an interference gap. Keys placed into the interference gap replace the bladder functionality. Following the assembly, the bladders are deflated and removed. Strain gauges mounted directly on the shell are used to monitor the stress of the entire magnet structure, thereby providing a high degree of pre-stress control without the need for high tolerances. During assembly, a force of 8.2 multiplied by 10**5 lbs /ft left bracket 12 MN/m right bracket is generated by the bladders and the stress in the 1.57 double prime left bracket 40 mm right bracket aluminum shell reaches 20.3 ksi left bracket 140 MPa right bracket...

  16. Shear-driven dynamo waves at high magnetic Reynolds number.

    Science.gov (United States)

    Tobias, S M; Cattaneo, F

    2013-05-23

    Astrophysical magnetic fields often display remarkable organization, despite being generated by dynamo action driven by turbulent flows at high conductivity. An example is the eleven-year solar cycle, which shows spatial coherence over the entire solar surface. The difficulty in understanding the emergence of this large-scale organization is that whereas at low conductivity (measured by the magnetic Reynolds number, Rm) dynamo fields are well organized, at high Rm their structure is dominated by rapidly varying small-scale fluctuations. This arises because the smallest scales have the highest rate of strain, and can amplify magnetic field most efficiently. Therefore most of the effort to find flows whose large-scale dynamo properties persist at high Rm has been frustrated. Here we report high-resolution simulations of a dynamo that can generate organized fields at high Rm; indeed, the generation mechanism, which involves the interaction between helical flows and shear, only becomes effective at large Rm. The shear does not enhance generation at large scales, as is commonly thought; instead it reduces generation at small scales. The solution consists of propagating dynamo waves, whose existence was postulated more than 60 years ago and which have since been used to model the solar cycle.

  17. Fabrication and magnetic investigations of highly uniform CoNiGa alloy nanowires

    Science.gov (United States)

    Li, Wen-Jing; Khan, U.; Irfan, Muhammad; Javed, K.; Liu, P.; Ban, S. L.; Han, X. F.

    2017-06-01

    CoNiGa ternary alloy nanowire arrays were successfully fabricated by simple DC electrodeposition into the anodized aluminum oxide (AAO) templates. A systematic study of the potential and components of the electrolyte were conducted to obtain different components of CoNiGa nanowires. The largest Ga content in the prepared alloy nanowires was about 17%, while for Co and Ni contents which can be controlled in a wide range by adjusting the composition and pH value of the electrolyte appropriately. X-ray diffraction analysis confirmed that the as-grown CoNiGa nanowire arrays were polycrystal with fcc phase of Co where Co atoms partially substituted by Ni and Ga. Magnetization curves of samples with different composition were measured at room temperature as well as low temperature. The results showed that the components of the alloy nanowires have a great impact on its magnetic properties. For Co55Ni28Ga17 nanowires, the magnetization reversal mode changes from curling mode to coherent rotation as the angle increases, and the temperature dependence of coercivity can be well described by the thermal activation effect.

  18. Characteristics of Magnetic Properties of Substituted Hexagonal Ferrites

    Directory of Open Access Journals (Sweden)

    Vladimir Jancarik

    2006-01-01

    Full Text Available The samples of barium hexaferrite BaFe12-2x(Me1Me2xO19 with x from 0.0 to 0.6 were prepared by variousmethods. The cationic preference of mainly divalent Me1 = Zn, Co, Ni, Sn ions and tetravalent Me2 = Ti, Zr, Ir, Sn, Ru ionsand their combinations in substituted Ba ferrites was investigated. The substitutions were performed to reduce the grain sizeand high magnetic uniaxial anisotropy field of the M-type Ba ferrite without affecting the magnetic polarisation. The goal isto reach the properties of ferrite proper for high-density magnetic recording and microwave absorption devices. Magneticproperties were determined as a function of the substitution level x. The specific saturation magnetic polarisation Js–m andremanence Js–rincreased with small x due to the substitution of non-magnetic and less magnetic ions in 4f1 and 4f2 sites. Thesteep decrease of coercivity Hc with increasing x may be caused by the Co2+ preference of 4f2 site and Ti4+or Zr4+ions preference of 2b and slightly in 4f1 sites. The temperature coefficient of the coercivity TKHc was very low (0.01kA.m-1.°C-1for the Co-Zr substitutions and positive for the rest of samples.

  19. Magnetic resonance imaging and spectroscopy at ultra high fields

    Energy Technology Data Exchange (ETDEWEB)

    Neuberger, Thomas

    2009-06-23

    The goal of the work presented in this thesis was to explore the possibilities and limitations of MRI / MRS using an ultra high field of 17.6 tesla. A broad range of specific applications and MR methods, from MRI to MRSI and MRS were investigated. The main foci were on sodium magnetic resonance spectroscopic imaging of rodents, magnetic resonance spectroscopy of the mouse brain, and the detection of small amounts of iron labeled stem cells in the rat brain using MRI Sodium spectroscopic imaging was explored since it benefits tremendously from the high magnetic field. Due to the intrinsically low signal in vivo, originating from the low concentrations and short transverse relaxation times, only limited results have been achieved by other researchers until now. Results in the literature include studies conducted on large animals such as dogs to animals as small as rats. No studies performed on mice have been reported, despite the fact that the mouse is the most important laboratory animal due to the ready availability of transgenic strains. Hence, this study concentrated on sodium MRSI of small rodents, mostly mice (brain, heart, and kidney), and in the case of the brain on young rats. The second part of this work concentrated on proton magnetic resonance spectroscopy of the rodent brain. Due to the high magnetic field strength not only the increasing signal but also the extended spectral resolution was advantageous for such kind of studies. The difficulties/limitations of ultra high field MRS were also investigated. In the last part of the presented work detection limits of iron labeled stem cells in vivo using magnetic resonance imaging were explored. The studies provided very useful benchmarks for future researchers in terms of the number of labeled stem cells that are required for high-field MRI studies. Overall this work has shown many of the benefits and the areas that need special attention of ultra high fields in MR. Three topics in MRI, MRS and MRSI were

  20. An H1(Ph)-Coercive Discontinuous Galerkin Formulation for The Poisson Problem : 1-D Analysis

    NARCIS (Netherlands)

    Van der Zee, K.G.; Van Brummelen, E.H.; De Borst, R.

    2006-01-01

    Coercivity of the bilinear form in a continuum variational problem is a fundamental property for finite-element discretizations: By the classical Lax–Milgram theorem, any conforming discretization of a coercive variational problem is stable; i.e., discrete approximations are well-posed and possess

  1. Magnetic studies of SiO2 coated CoFe2O4 nanoparticles

    Science.gov (United States)

    Limaye, Mukta V.; Singh, Shashi B.; Das, Raja; Poddar, Pankaj; Abyaneh, Majid K.; Kulkarni, Sulabha K.

    2017-11-01

    Oleic acid capped CoFe2O4 nanoparticles which exhibit a high coercivity of ∼9.47 kOe at room temperature were coated with a robust coating of SiO2. We have used chemical synthesis method to obtain SiO2 coated CoFe2O4 nanoparticles with different weight percentages of CoFe2O4 in SiO2 (1.5, 3.1 and 4.8 wt.%). The morphological investigation of the coated nanoparticles by transmission electron microscopy shows that the particles are spherical with average size ∼160 nm. Infrared spectroscopy reveals that oleic acid capping on the surface of CoFe2O4 nanoparticles is retained after silica coating process. The complete coating of SiO2 on CoFe2O4 nanoparticles is confirmed by X-ray photoelectron spectroscopy as there is no signature of cobalt or iron ions on the surface. Magnetic measurements show that coercivity of SiO2 coated CoFe2O4 particles remains more or less unaffected as in CoFe2O4 nanoparticles at room temperature. In addition, the temperature dependent magnetic measurements show that at 5 K the CoFe2O4 and SiO2 coated 1.5 wt.% CoFe2O4 samples exhibit a very high value of coercivity (∼20 kOe) which is more than twice as compared to room temperature coercivity value (∼9.47 kOe). We conclude that silica coating in our study does not significantly affect the coercivity of CoFe2O4 nanoparticles.

  2. Complementary analyses of hollow cylindrical unioriented permanent magnet (HCM) with high permeability external layer.

    Science.gov (United States)

    Lobo, Carlos M S; Tosin, Giancarlo; Baader, Johann E; Colnago, Luiz A

    2017-10-01

    In this article, several studies based on analytical expressions and computational simulations on Hollow Cylindrical Magnets with an external soft ferromagnetic material (HCM magnets) are presented. Electromagnetic configurations, as well as permanent-magnet-based structures, are studied in terms of magnetic field strength and homogeneity. Permanent-magnet-based structures are further analyzed in terms of the anisotropy of the magnetic permeability. It was found that the HCM magnets produce a highly homogeneous magnetic field as long as the magnetic material is isotropic. The dependency of the magnetic field strength and homogeneity in terms of the anisotropy of the magnetic permeability is also explored here. These magnets can potentially be used in medium-resolution NMR spectrometers and high-field NMR spectrometers. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. submitter A High Precision 3D Magnetic Field Scanner for Small to Medium Size Magnets

    CERN Document Server

    Bergsma, F; Garnier, F; Giudici, P A

    2016-01-01

    A bench to measure the magnetic field of small to-medium-sized magnets with high precision was built. It uses a small-sized head with three orthogonal Hall probes, supported on a long pole at continuous movement during measurement. The head is calibrated in three dimensions by rotation over the full solid angle in a special device. From 0 to 2.5 T, the precision is ±0.2 mT in all components. The spatial range is 1 × 1 × 2 m with precision of ±0.02 mm. The bench and its controls are lightweight and easy to transport. The head can penetrate through small apertures and measure as close as 0.5 mm from the surface of a magnet. The bench can scan complicated grids in Cartesian or cylindrical coordinates, steered by a simple text file on an accompanying PC. The raw data is online converted to magnetic units and stored in a text file.

  4. Output Enhancement Effect of Magnetic Underlayer in High-Density Magnetic Recording

    Science.gov (United States)

    Endo, Katsumi; Yoshida, Osamu; Sasaki, Kenji; Nakayama, Kazuhiko; Maki, Kazuo; Nakamura, Yoshihisa

    1999-10-01

    A double-layered tape with a metal particulate (MP) upper layer and a metal-evaporated (ME) underlayer is fabricated. Output properties were enhanced over the single-layered MP tape in high-density recording. This effect cannot be explained by conventional magnetic recording mechanisms, and a new model of magneto-static interaction is proposed. This model is supported by a preliminary computer simulation.

  5. 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.

  6. Manipulation of morphology and magnetic properties in cobalt nanowires

    Science.gov (United States)

    Li, Chenglin; Wu, Qiong; Yue, Ming; Xu, Huanhuan; Palaka, Subhashini; Elkins, Kevin; Ping Liu, J.

    2017-05-01

    Ferromagnetic metallic Cobalt nanowires are synthesized by the reduction of carboxylate salts of Co in 1, 2-butanediol using a solvothermal chemical process. In this process, the size and shape of the nanocrystals can be controlled via reaction parameters such as surfactant ratio, precursor concentration, and the temperature ramp. Synthesized Co nanocrystals exhibit the hexagonally close-packed phase favored the growth of anisotropic particles and the (002) crystalline direction is along the long axis of the nanowires. By varying the catalyst concentration in proper range, the effect of synthetic parameters on controlling Co nanoparticles with different length of 50 - 700 nm was systematically studied. Magnetic measurements and TEM images of the Cobalt nanowires indicate that the coercivity of the Co nanowires depends substantially on the morphology. The obtained highest coercivity of 8.4 kOe can be attributed to their small mean diameter and high crystallinity of nanowires for 200 - 300 nm.

  7. Manipulation of morphology and magnetic properties in cobalt nanowires

    Directory of Open Access Journals (Sweden)

    Chenglin Li

    2017-05-01

    Full Text Available Ferromagnetic metallic Cobalt nanowires are synthesized by the reduction of carboxylate salts of Co in 1, 2-butanediol using a solvothermal chemical process. In this process, the size and shape of the nanocrystals can be controlled via reaction parameters such as surfactant ratio, precursor concentration, and the temperature ramp. Synthesized Co nanocrystals exhibit the hexagonally close-packed phase favored the growth of anisotropic particles and the (002 crystalline direction is along the long axis of the nanowires. By varying the catalyst concentration in proper range, the effect of synthetic parameters on controlling Co nanoparticles with different length of 50 - 700 nm was systematically studied. Magnetic measurements and TEM images of the Cobalt nanowires indicate that the coercivity of the Co nanowires depends substantially on the morphology. The obtained highest coercivity of 8.4 kOe can be attributed to their small mean diameter and high crystallinity of nanowires for 200 - 300 nm.

  8. Progress with High-Field Superconducting Magnets for High-Energy Colliders

    Science.gov (United States)

    Apollinari, Giorgio; Prestemon, Soren; Zlobin, Alexander V.

    2015-10-01

    One of the possible next steps for high-energy physics research relies on a high-energy hadron or muon collider. The energy of a circular collider is limited by the strength of bending dipoles, and its maximum luminosity is determined by the strength of final focus quadrupoles. For this reason, the high-energy physics and accelerator communities have shown much interest in higher-field and higher-gradient superconducting accelerator magnets. The maximum field of NbTi magnets used in all present high-energy machines, including the LHC, is limited to ˜10 T at 1.9 K. Fields above 10 T became possible with the use of Nb3Sn superconductors. Nb3Sn accelerator magnets can provide operating fields up to ˜15 T and can significantly increase the coil temperature margin. Accelerator magnets with operating fields above 15 T require high-temperature superconductors. This review discusses the status and main results of Nb3Sn accelerator magnet research and development and work toward 20-T magnets.

  9. Use of Coercive Measures during Involuntary Psychiatric Admission and Treatment Outcomes: Data from a Prospective Study across 10 European Countries

    National Research Council Canada - National Science Library

    McLaughlin, Paul; Giacco, Domenico; Priebe, Stefan

    2016-01-01

    ... of coercive practice are those referred to as ‘coercive measures’–forced administration of psychotropic medication against the patient’s will, involuntary confinement of the patient in isolati...

  10. Synthesis, Characterization, and Enhanced Magnetic Properties of Iron Carbide Nanomaterials

    Science.gov (United States)

    Williams, Brent M.

    Permanent magnets are classified as hard magnetic materials with the main purpose of generating flux for applications such as electric motors, turbines, and hard drives. High coercivity, magnetic remanence, and saturation values with high stability are some of the requirements for permanent magnets. Rare-earth magnets including neodymium and samarium based magnets are known to have superior magnetic properties due to their high magnetocrystalline anisotropy. However, due to the price of rare-earth materials development of alternate permanent magnets composed of inexpensive materials is an ongoing process. Previously cobalt carbide (CoxC) have shown promise as a potential rare-earth free magnet alternative with magnetic properties comparable to that of hexaferrite materials. Unfortunately, CoxC magnets have a low magnetic saturation (50 emu g-1) which drastically lowers its energy product. Alternatively, iron carbide has a rather high bulk magnetization value of 140 emu g-1 and is composed of naturally abundant materials. The sole issue of iron carbide is that it is considered an intermediate magnet with properties between those of a hard and a soft magnetic material. The main focus of this work is the enhancement of the hard magnetic properties of iron carbide through size effect, shape anisotropy, magnetocrystalline anisotropy and exchange anisotropy. First a wet synthesis method was developed which utilized hexadecyltrimethylammonium chloride to control particle size, shape, and crystal structure to manipulate the magnetic properties of iron carbide. With this method a semi-hard 50 nm orthorhombic Fe3C phase and a magnetically soft single crystal hexagonal Fe7C3 structure with texture-induced magnetic properties were developed. The properties for both materials were further enhanced through formation of exchange bias Fe3C/CoO nanoaggregates and spring exchange coupling of the ferromagnetically hard and soft phases of Fe7C3/SrFe 12O19. A 33% increase in coercivity

  11. 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.

  12. Effect of C and Ce addition on the microstructure and magnetic property of the mechanically alloyed FeSiBAlNi high entropy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jing [School of Materials Science and Engineering, University of Jinan, No. 336, West Road of Nan Xinzhuang, Jinan 250022 (China); Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, No. 336, West Road of Nan Xinzhuang, Jinan 250022 (China); Axinte, Eugen [Gh. Asachi Technical University of Iasi, Faculty of Machine Manufacturing & Industrial Management, 59 A, Prof. Dimitrie Mangeron Blvd. (Romania); Zhao, Zhengfeng [School of Materials Science and Engineering, University of Jinan, No. 336, West Road of Nan Xinzhuang, Jinan 250022 (China); Wang, Yan, E-mail: mse_wangy@ujn.edu.cn [School of Materials Science and Engineering, University of Jinan, No. 336, West Road of Nan Xinzhuang, Jinan 250022 (China); Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, No. 336, West Road of Nan Xinzhuang, Jinan 250022 (China)

    2016-09-15

    The effects of elemental addition, C and Ce, on the microstructure, thermal property and magnetic property of mechanically alloyed FeSiBAlNi (based-W5) high entropy alloys (HEAs) have been investigated in depth in the present work. The amorphous HEAs have been successfully fabricated by mechanical alloying. The results reveal that Ce addition obviously shortens the formation time of fully amorphous phase, therefore leading to the enhanced glass forming ability (GFA) of the based-W5. The final products of as-milled FeSiBAlNiC alloy consist of the main amorphous phase and a small amount of Si nanocrystals. In addition, C and Ce addition are both beneficial to enhance the thermal stability. The coercivity force (H{sub c}) of the tested samples lies in the range of 50–378 Oe, suggesting the semi-hard magnetic property. The saturation magnetization (M{sub s}) becomes decreased with increasing the milling time. C addition effectively increases M{sub s} exhibiting the good magnetic property, however, Ce addition presents the negative effect. It should be noted that the amorphous phase tends to be formed when the radius ratio (R{sub r}) is larger than 1, and the GFA is enhanced with increasing R{sub r} and valence electron concentration. - Highlights: • FeSiBAlNi (C, Ce) amorphous HEAs have been fabricated by mechanical alloying. • The effects of C and Ce addition were investigated. • Ce addition exhibits a remarkably enhanced effect on glass forming ability (GFA). • C and Ce additions are beneficial to enhance thermal stability.

  13. High-performance battery electrodes via magnetic templating

    Science.gov (United States)

    Sander, J. S.; Erb, R. M.; Li, L.; Gurijala, A.; Chiang, Y.-M.

    2016-08-01

    In lithium-ion batteries, the critical need for high-energy-density, low-cost storage for applications ranging from wearable computing to megawatt-scale stationary storage has created an unmet need for facile methods to produce high-density, low-tortuosity, kinetically accessible storage electrodes. Here we show that magnetic control of sacrificial features enables the creation of directional pore arrays in lithium-ion electrodes. The directional pores result in faster charge transport kinetics and enable electrodes with more than threefold higher area capacity (for example, >12 mAh cm-2 versus electric vehicle model drive cycle.

  14. Entanglement and magnetism in high-spin graphene nanodisks

    Science.gov (United States)

    Hagymási, I.; Legeza, Ö.

    2018-01-01

    We investigate the ground-state properties of triangular graphene nanoflakes with zigzag edge configurations. The description of zero-dimensional nanostructures requires accurate many-body techniques since the widely used density-functional theory with local density approximation or Hartree-Fock methods cannot handle the strong quantum fluctuations. Applying the unbiased density-matrix renormalization group algorithm we calculate the magnetization and entanglement patterns with high accuracy for different interaction strengths and compare them to the mean-field results. With the help of quantum information analysis and subsystem density matrices we reveal that the edges are strongly entangled with each other. We also address the effect of electron and hole doping and demonstrate that the magnetic properties of triangular nanoflakes can be controlled by an electric field, which reveals features of flat-band ferromagnetism. This may open up new avenues in graphene based spintronics.

  15. High-Resolution and Frequency, Printed Miniature Magnetic Probes

    Science.gov (United States)

    Prager, James; Ziemba, Timothy; Miller, Kenneth; Picard, Julian

    2013-10-01

    Eagle Harbor Technologies, Inc. (EHT) is developing a technique to significantly reduce the cost and development time of producing magnetic field diagnostics. EHT is designing probes that can be printed on flexible PCBs thereby allowing for extremely small coils to be produced while essentially eliminating the time to wind the coils. The coil size can be extremely small when coupled with the EHT Hybrid Integrator, which is capable of high bandwidth measurements over short and long pulse durations. This integrator is currently being commercialized with the support of a DOE SBIR. Additionally, the flexible PCBs allow probes to be attached to complex surface and/or probes that have a complex 3D structure to be designed and fabricated. During the Phase I, EHT will design and construct magnetic field probes on flexible PCBs, which will be tested at the University of Washington's HIT-SI experiment and in EHT's material science plasma reactor. Funding provided by DOE SBIR/STTR Program.

  16. Magnetic probe array with high sensitivity for fluctuating field.

    Science.gov (United States)

    Kanamaru, Yuki; Gota, Hiroshi; Fujimoto, Kayoko; Ikeyama, Taeko; Asai, Tomohiko; Takahashi, Tsutomu; Nogi, Yasuyuki

    2007-03-01

    A magnetic probe array is constructed to measure precisely the spatial structure of a small fluctuating field included in a strong confinement field that varies with time. To exclude the effect of the confinement field, the magnetic probes consisting of figure-eight-wound coils are prepared. The spatial structure of the fluctuating field is obtained from a Fourier analysis of the probe signal. It is found that the probe array is more sensitive to the fluctuating field with a high mode number than that with a low mode number. An experimental demonstration of the present method is attempted using a field-reversed configuration plasma, where the fluctuating field with 0.1% of the confinement field is successfully detected.

  17. Investigating Exchange Bias and Coercivity in Fe3O4–γ-Fe2O3 Core–Shell Nanoparticles of Fixed Core Diameter and Variable Shell Thicknesses

    Directory of Open Access Journals (Sweden)

    Ihab M. Obaidat

    2017-11-01

    Full Text Available We have carried out extensive measurements on novel Fe3O4–γ-Fe2O3 core–shell nanoparticles of nearly similar core diameter (8 nm and of various shell thicknesses of 1 nm (sample S1, 3 nm (sample S2, and 5 nm (sample S3. The structure and morphology of the samples were studied using X-ray diffraction (XRD, transmission electron microscopy (TEM, and selected area electron diffraction (SAED. The direct current (DC magnetic measurements were carried out using a superconducting quantum interference device (SQUID. Exchange bias and coercivity were investigated at several temperatures where the applied field was varied between 3 and −3 T. Several key results are obtained, such as: (a the complete absence of exchange bias effect in sample S3; (b the occurrence of nonconventional exchange bias effect in samples S2 and S1; (c the sign-change of exchange bias field in sample S2; (d the monotonic increase of coercivity with temperature above 100 K in all samples; (e the existence of a critical temperature (100 K at which the coercivity is minimum; (f the surprising suppression of coercivity upon field-cooling; and (g the observation of coercivity at all temperatures, even at 300 K. The results are discussed and attributed to the existence of spin glass clusters at the core–shell interface.

  18. Study of the magnetization behavior of ferromagnetic nanowire array: Existence of growth defects revealed by micromagnetic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Vien, G., E-mail: gilles.nguyen@univ-brest.fr [Laboratoire de Magnétisme de Bretagne, EA 4522, Université de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3 (France); Rioual, S. [Laboratoire de Magnétisme de Bretagne, EA 4522, Université de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3 (France); Gloaguen, F. [Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3 (France); Rouvellou, B.; Lescop, B. [Laboratoire de Magnétisme de Bretagne, EA 4522, Université de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3 (France)

    2016-03-01

    High aspect ratio nanowires were electrodeposited in nanoporous anodic alumina template by a potentiostatic method. The angular dependence of the coercive field and remanence magnetization extracted from magnetometry measurements are compared with micromagnetic simulations. Inclusion of magnetostatic interactions between Ni nanowires in simulations is required to explain some of the properties of the magnetization reversal. However, it is not sufficient to reproduce fully the angular dependence of the coercive field. Due to the polycrystalline nature of nanowires and thus to the presence of grain boundaries, defects are included in simulations. A good agreement between theory and experiment is then clearly highlighted, in particular in the nanowire easy axis direction. The achieved results allow a description of several experimental data published in the literature and consequently to get a better understanding of reversal mechanisms that operate in such nanowire arrays. A complementary study of composite nanowire array is successfully performed to prove the adequacy of the simulations method to describe the magnetic properties of nanowire array. - Highlights: • High axial squareness nanowire array are synthetized by a potentiostatic method. • Nanowires are modeled as non-ideal magnetic particles. • Segmentation of nanowire is required to describe the angular dependence of coercivity. • Respective role of magnetostatic coupling and nanowire segmentation in nanowire array are studied. • Micromagnetic simulations lead to quantitative agreement for well-defined composite nanowire array.

  19. Phase Transitions in Mechanically Milled Mn-Al-C Permanent Magnets

    Directory of Open Access Journals (Sweden)

    Michael J. Lucis

    2014-04-01

    Full Text Available Mn-Al powders were prepared by rapid solidification followed by high-energy mechanical milling. The rapid solidification resulted in single-phase ε. The milling was performed in both the ε phase and the τ phase, with the τ-phase formation accomplished through a heat treatment at 500 °C for 10 min. For the ε-milled samples, the conversion of the ε to the τ phase was accomplished after milling via the same heat treatment. Mechanical milling induced a significant increase in coercivity in both cases, reaching 4.5 kOe and 4.1 kOe, respectively, followed by a decrease upon further milling. The increase in coercivity was the result of grain refinement induced by the high-energy mechanical milling. Additionally, in both cases a loss in magnetization was observed. Milling in the ε phase showed a smaller decrease in the magnetization due to a higher content of the τ phase. The loss in magnetization was attributed to a stress-induced transition to the equilibrium phases, as no site disorder or oxidation was observed. Surfactant-assisted milling in oleic acid also improved coercivity, but in this case values reached >4 kOe and remained stable at least through 32 h of milling.

  20. Development of controlled solid-state alignment for alnico permanent magnets in near-final shape

    Science.gov (United States)

    Anderson, Iver E.; Kassen, Aaron G.; White, Emma M. H.; Palasyuk, Andriy; Zhou, Lin; Tang, Wei; Kramer, Matthew J.

    2017-05-01

    The 2011 price shock in the rare earth (RE) permanent magnet (PM) marketplace precipitated realization of extremely poor RE supply diversity and drove renewed research in RE-free permanent magnets such as "alnico." Essentially, alnico is an Al-Ni-Co-Fe alloy with high magnetic saturation and TC, but low coercivity. It also was last researched extensively in the 1970's. Currently alnico "9" magnets with the highest energy product (10MGOe) are manufactured by directional solidification to make highly aligned anisotropic magnets. This work developed novel powder processing techniques to improve on unaligned anisotropic alnico "8H" with elevated coercivity. Gas atomization was used to produce pre-alloyed powder for binder-assisted compression molding of near-final shape magnets that were vacuum sintered to full density (direction. Evaluation of heavily stressed samples (>250g) showed reduced overall loop squareness compared to unaligned (equiaxed) 8H due to grain rotation-induced misalignment, while low stresses improved squareness and greatly improved alignment compared to equiaxed magnets, with squareness approaching 0.30 and remanence ratio as high as 0.79.

  1. Development of controlled solid-state alignment for alnico permanent magnets in near-final shape

    Directory of Open Access Journals (Sweden)

    Iver E. Anderson

    2017-05-01

    Full Text Available The 2011 price shock in the rare earth (RE permanent magnet (PM marketplace precipitated realization of extremely poor RE supply diversity and drove renewed research in RE-free permanent magnets such as “alnico.” Essentially, alnico is an Al-Ni-Co-Fe alloy with high magnetic saturation and TC, but low coercivity. It also was last researched extensively in the 1970’s. Currently alnico “9” magnets with the highest energy product (10MGOe are manufactured by directional solidification to make highly aligned anisotropic magnets. This work developed novel powder processing techniques to improve on unaligned anisotropic alnico “8H” with elevated coercivity. Gas atomization was used to produce pre-alloyed powder for binder-assisted compression molding of near-final shape magnets that were vacuum sintered to full density (250g showed reduced overall loop squareness compared to unaligned (equiaxed 8H due to grain rotation-induced misalignment, while low stresses improved squareness and greatly improved alignment compared to equiaxed magnets, with squareness approaching 0.30 and remanence ratio as high as 0.79.

  2. High resolution magnetic force microscopy using focused ion beam modified tips

    NARCIS (Netherlands)

    Phillips, G.N.; Siekman, Martin Herman; Abelmann, Leon; Lodder, J.C.

    2002-01-01

    Atomic force microscope tips coated by the thermal evaporation of a magnetic 30 nm thick Co film have been modified by focused ion beam milling with Ga+ ions to produce tips suitable for magnetic force microscopy. Such tips possess a planar magnetic element with high magnetic shape anisotropy, an

  3. Evidence for single-chain magnet behavior in a Mn(III)-Ni(II) chain designed with high spin magnetic units: a route to high temperature metastable magnets.

    Science.gov (United States)

    Clérac, Rodolphe; Miyasaka, Hitoshi; Yamashita, Masahiro; Coulon, Claude

    2002-10-30

    . This result indicates the presence of a metastable state without magnetic long-range order. This material is the first experimental design of a heterometallic chain with ST = 3 magnetic units showing a "single-chain magnet" behavior predicted in 1963 by R. J. Glauber for an Ising one-dimensional system. This work opens new perspectives for one-dimensional systems to obtain high temperature metastable magnets by combining high spin magnetic units, strong interunit interactions, and uniaxial anisotropy.

  4. Coercive measures in health promotion: can they be justified?

    Science.gov (United States)

    Wikler, D I

    1978-01-01

    Though environmental hazards and lack of medical care continue to threaten the public's health, much recent attention has turned to the role of destructive health-related behavior. If, as Fuchs suggests, changing behavior patterns is the most powerful alternative open to advanced countries in the pursuit of health, the role of the health educator is likely to grow more prominent relative to other health-care professionals. At the same time, that role may change. A campaign to solve the nation's health problems by altering habits of living may require methods which are stronger than the traditional health educator's efforts to facilitate and inform. This paper examines the coercive aspects of some of these possible measures and surveys the moral justifications for a policy of using coercion to bring about the desired changes in health-related behavior. Three such arguments are most plausible: that the coercion is justified by the social benefit; by the benefit to the coerced; and by a right of others in society to prevent the self-destructive individual from placing unfair burdens upon them.

  5. Coercive Population Control and Asylum in the U.S.

    Directory of Open Access Journals (Sweden)

    Connie Oxford

    2017-11-01

    Full Text Available In 1980, China implemented one of the most controversial population policies in modern times. China’s one-child policy shaped population politics for thirty-five years until its dissolution in 2015. During this time, many women were subjected to routine gynecological examinations, pregnancy testing, abortions, and sterilizations, which were often forced upon them by family planning officials. Some women fled China and sought refuge in the United States after having experienced a forced abortion or forced sterilization or feared that they would be subjected to a forced abortion or forced sterilization. This article focuses on how the U.S. government responded to China’s one-child policy through the passage of immigration laws and policies that made asylum a viable option for Chinese nationals who had been persecuted or feared persecution because of coercive population control policies. Based on observations of asylum hearings and interviews with immigration judges and immigration attorneys, this article uses feminist ethnographic methods to show how China’s one-child policy and U.S. asylum laws shape the gender politics of reproduction and migration.

  6. Recent trends in high spin sensitivity magnetic resonance

    Science.gov (United States)

    Blank, Aharon; Twig, Ygal; Ishay, Yakir

    2017-07-01

    Magnetic resonance is a very powerful methodology that has been employed successfully in many applications for about 70 years now, resulting in a wealth of scientific, technological, and diagnostic data. Despite its many advantages, one major drawback of magnetic resonance is its relatively poor sensitivity and, as a consequence, its bad spatial resolution when examining heterogeneous samples. Contemporary science and technology often make use of very small amounts of material and examine heterogeneity on a very small length scale, both of which are well beyond the current capabilities of conventional magnetic resonance. It is therefore very important to significantly improve both the sensitivity and the spatial resolution of magnetic resonance techniques. The quest for higher sensitivity led in recent years to the development of many alternative detection techniques that seem to rival and challenge the conventional ;old-fashioned; induction-detection approach. The aim of this manuscript is to briefly review recent advances in the field, and to provide a quantitative as well as qualitative comparison between various detection methods with an eye to future potential advances and developments. We first offer a common definition of sensitivity in magnetic resonance to enable proper quantitative comparisons between various detection methods. Following that, up-to-date information about the sensitivity capabilities of the leading recently-developed detection approaches in magnetic resonance is provided, accompanied by a critical comparison between them and induction detection. Our conclusion from this comparison is that induction detection is still indispensable, and as such, it is very important to look for ways to significantly improve it. To do so, we provide expressions for the sensitivity of induction-detection, derived from both classical and quantum mechanics, that identify its main limiting factors. Examples from current literature, as well as a description of

  7. Building high-coverage monolayers of covalently bound magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Mackenzie G.; Teplyakov, Andrew V., E-mail: andrewt@udel.edu

    2016-12-01

    Graphical abstract: - Highlights: • A method for forming a layer of covalently bound nanoparticles is offered. • A nearly perfect monolayer of covalently bound magnetic nanoparticles was formed on gold. • Spectroscopic techniques confirmed covalent binding by the “click” reaction. • The influence of the functionalization scheme on surface coverage was investigated. - Abstract: This work presents an approach for producing a high-coverage single monolayer of magnetic nanoparticles using “click chemistry” between complementarily functionalized nanoparticles and a flat substrate. This method highlights essential aspects of the functionalization scheme for substrate surface and nanoparticles to produce exceptionally high surface coverage without sacrificing selectivity or control over the layer produced. The deposition of one single layer of magnetic particles without agglomeration, over a large area, with a nearly 100% coverage is confirmed by electron microscopy. Spectroscopic techniques, supplemented by computational predictions, are used to interrogate the chemistry of the attachment and to confirm covalent binding, rather than attachment through self-assembly or weak van der Waals bonding. Density functional theory calculations for the surface intermediate of this copper-catalyzed process provide mechanistic insight into the effects of the functionalization scheme on surface coverage. Based on this analysis, it appears that steric limitations of the intermediate structure affect nanoparticle coverage on a flat solid substrate; however, this can be overcome by designing a functionalization scheme in such a way that the copper-based intermediate is formed on the spherical nanoparticles instead. This observation can be carried over to other approaches for creating highly controlled single- or multilayered nanostructures of a wide range of materials to result in high coverage and possibly, conformal filling.

  8. Nb3Sn High Field Magnets for the High Luminosity LHC Upgrade Project

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Giorgio

    2015-06-01

    The High Luminosity upgrade of the Large Hadron Collider at CERN requires a new generation of high field superconducting magnets. High field large aperture quadrupoles (MQXF) are needed for the low-beta triplets close to the ATLAS and CMS detectors, and high field two-in-one dipoles (11 T dipoles) are needed to make room for additional collimation. The MQXF quadrupoles, with a field gradient of 140 T/m in 150 mm aperture, have a peak coil field of 12.1 T at nominal current. The 11 T dipoles, with an aperture of 60 mm, have a peak coil field of 11.6 T at nominal current. Both magnets require Nb3Sn conductor and are the first applications of this superconductor to actual accelerator magnets.

  9. Thermomagnetic transitions and coercivity mechanism in bulk composite Nd{sub 60}Fe{sub 30}Al{sub 10} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Zempoalteca, R. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico D.F. 04510 (Mexico); Betancourt, I. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico D.F. 04510 (Mexico)], E-mail: israelb@correo.unam.mx; Valenzuela, R. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico D.F. 04510 (Mexico)

    2009-10-15

    The thermomagnetic behaviour (within the temperature range 553-300 K) for the bulk composite Nd{sub 60}Fe{sub 30}Al{sub 10} alloy is described in terms of a transition from paramagnetic to superferromagnetic state at T=553 K, followed by a ferromagnetic ordering for T<473 K. For the superferromagnetic regime, the alloy thermomagnetic response was associated to a homogeneous distribution of magnetic clusters with mean magnetic moment and size of 1072 {mu}{sub B} and 2.5 nm, respectively. For T<473 K, a pinning model of domain walls described properly the alloy coercivity dependence with temperature, from which the domain wall width and the magnetic anisotropy constant were estimated as being of {approx}8 nm and {approx}10{sup 5} J/m{sup 3}, typical values of hard magnetic phases. Results are supported by microstructural and magnetic domain observations.

  10. Unexpected Windy Weather Around a Highly Magnetized Neutron Star

    Science.gov (United States)

    Younes, George A.; Kouveliotou, Chryssa; Kargaltsev, Oleg; Gill, Ramandeep; Granot, Jonathan; Watts, Anna; Gelfand, Joseph; Baring, Matthew G.; Kust Harding, Alice; Pavlov, George G.; van der Horst, Alexander; Huppenkothen, Daniela; Gögüs, Ersin; Lin, Lin; Roberts, Oliver

    2016-04-01

    Magnetars and rotation-powered pulsars (RPPs) historically represented two distinct subclasses of neutron stars. Magnetars are slowly-rotating (~2-12 s), isolated neutron stars (NSs) with super-strong magnetic fields, B~10^13-10^15 G. RPPs, on the other hand, are rapidly-rotating (~0.01-0.3~s), isolated NSs with surface dipole magnetic field in the range ~10^11-10^13 G. Most pulsars possess a large rotational energy loss rate that powers a relativistic magnetized particle wind, often seen as a pulsar wind nebula (PWN; the Crab PWN being the most famous). There has not yet been convincing evidence for a wind nebula around magnetars, most likely due to their low rotational energy loss rate. Here, we report the study of new deep X-ray observations of the peculiar extended emission around the magnetar Swift J1834.9-0846. Our new results strongly support a wind nebula as the nature of the extended emission, thus, establishing Swift J1834.9-0846 as the first magnetar to possess a surrounding nebula. This implies that wind nebulae are no longer exclusive to RPPs and, along with recent discoveries in the field, further narrow the gaps between these two sub-populations of isolated NSs. The physical properties of this wind nebula, however, show peculiarities, especially its high radiative efficiency of about 10%, only shared with two other known very young RPPs, the Crab and its twin.

  11. Simulations of magnetic hysteresis loops at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Plumer, M. L.; Whitehead, J. P.; Fal, T. J. [Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John' s, Newfoundland and Labrador A1B 3X7 (Canada); Ek, J. van [Western Digital Corporation, San Jose, California 94588 (United States); Mercer, J. I. [Department of Computer Science, Memorial University of Newfoundland, St. John' s, Newfoundland and Labrador A1B 3X7 (Canada)

    2014-09-28

    The kinetic Monte-Carlo algorithm as well as standard micromagnetics are used to simulate MH loops of high anisotropy magnetic recording media at both short and long time scales over a wide range of temperatures relevant to heat-assisted magnetic recording. Microscopic parameters, common to both methods, were determined by fitting to experimental data on single-layer FePt-based media that uses the Magneto-Optic Kerr effect with a slow sweep rate of 700 Oe/s. Saturation moment, uniaxial anisotropy, and exchange constants are given an intrinsic temperature dependence based on published atomistic simulations of FePt grains with an effective Curie temperature of 680 K. Our results show good agreement between micromagnetics and kinetic Monte Carlo results over a wide range of sweep rates. Loops at the slow experimental sweep rates are found to become more square-shaped, with an increasing slope, as temperature increases from 300 K. These effects also occur at higher sweep rates, typical of recording speeds, but are much less pronounced. These results demonstrate the need for accurate determination of intrinsic thermal properties of future recording media as input to micromagnetic models as well as the sensitivity of the switching behavior of thin magnetic films to applied field sweep rates at higher temperatures.

  12. Structure, coercive control, and autonomy promotion: A comparison of fathers' and mothers' food parenting strategies.

    Science.gov (United States)

    Pratt, Mercedes; Hoffmann, Debra; Taylor, Maija; Musher-Eizenman, Dara

    2017-05-01

    This study explored differences in mothers' and fathers' food parenting strategies, specifically coercive control, structure, and autonomy promotion, and whether parenting style and parental responsibility for food parenting related to the use of these strategies. Parents of children aged 2.5-7.5 years ( N = 497) reported about their parenting practices and food parenting strategies. Parenting style accounted for the majority of the variance in food parenting. Fathers were more authoritarian than mothers. Authoritarian and permissive parenting practices were related to more coercive strategies. Mothers reported more food parenting responsibility. Responsibility was related to less coercive practices and more autonomy promotion and structure.

  13. A mineral magnetic characterization of the Plio-Pleistocene fluvial infill of the Heidelberg Basin (Germany)

    Science.gov (United States)

    Scheidt, Stephanie; Egli, Ramon; Frederichs, Thomas; Hambach, Ulrich; Rolf, Christian

    2017-08-01

    The Heidelberg Basin (Germany) hosts a quasi-continuous sedimentary sequence of primarily fluvial sediments with pedogenetic overprints and lacustrine intercalations. This unconsolidated succession has been shown to record a consistent magnetic polarity stratigraphy of the Quaternary and the late Neogene. Previous work has reported that sulphides and high-coercive minerals are the carriers of the remanent magnetization. Here, we provide the results of an extended mineral magnetic study that aims to disentangle the complex magnetic mineralogy. In addition, we assess the reliability of these minerals as carriers of palaeomagnetic signals. A major obstacle to the analysis of the drill cores was the large number of samples that were taken from a total core length of 1150 m. Rapid measurements on bulk samples provided only limited information on the magnetic mineralogy. In contrast, time-intensive methods such as first-order reversal curves (FORCs) or coercivity analyses, for example, yielded valuable information. The combined results of all the analyses consider the heterogeneous compositions of the sediments and indicate a varying palaeoenvironmental history. The Pliocene Iffezheim Formation was formed under alternating reducing and oxidizing conditions. Magnetite, maghemite, haematite and goethite are the predominant magnetic minerals. Sulphides were only preserved under specific conditions. The Pleistocene sediments reflect predominantly reducing conditions during sedimentation and diagenesis. Greigite, pyrite and most likely pyrrhotite have been shown to occur. Taken together, our work provides a detailed environmental magnetic record of the Plio-Pleistocene and elucidates the capabilities and limitations of rock magnetic studies performed on fluvial dominated sedimentary successions.

  14. High-Magnetic-Field and High-Pressure Effects in Monocrystalline URu2Si2

    NARCIS (Netherlands)

    Boer, F.R. de; Franse, J.J.M.; Louis, E.; Menovsky, A.A.; Mydosh, J.A.; Palstra, T.T.M.; Rauchschwalbe, U.; Schlabitz, W.; Steglich, F.; Visser, A. de

    1986-01-01

    High-field magnetisation and high-pressure resistivity measurements have been performed on monocrystalline samples of the superconducting compound URu2Si2 just above Tc. At 1.4 K, well below the magnetic ordering temperature of about 17.5K, two sharp transitions at 36 and 40 T have been observed in

  15. Does the Sole Description of a Tax Authority Affect Tax Evasion? - The Impact of Described Coercive and Legitimate Power

    Science.gov (United States)

    Hartl, Barbara; Hofmann, Eva; Gangl, Katharina; Hartner-Tiefenthaler, Martina; Kirchler, Erich

    2015-01-01

    Following the classic economic model of tax evasion, taxpayers base their tax decisions on economic determinants, like fine rate and audit probability. Empirical findings on the relationship between economic key determinants and tax evasion are inconsistent and suggest that taxpayers may rather rely on their beliefs about tax authority’s power. Descriptions of the tax authority’s power may affect taxpayers’ beliefs and as such tax evasion. Experiment 1 investigates the impact of fines and beliefs regarding tax authority’s power on tax evasion. Experiments 2-4 are conducted to examine the effect of varying descriptions about a tax authority’s power on participants’ beliefs and respective tax evasion. It is investigated whether tax evasion is influenced by the description of an authority wielding coercive power (Experiment 2), legitimate power (Experiment 3), and coercive and legitimate power combined (Experiment 4). Further, it is examined whether a contrast of the description of power (low to high power; high to low power) impacts tax evasion (Experiments 2-4). Results show that the amount of fine does not impact tax payments, whereas participants’ beliefs regarding tax authority’s power significantly shape compliance decisions. Descriptions of high coercive power as well as high legitimate power affect beliefs about tax authority’s power and positively impact tax honesty. This effect still holds if both qualities of power are applied simultaneously. The contrast of descriptions has little impact on tax evasion. The current study indicates that descriptions of the tax authority, e.g., in information brochures and media reports, have more influence on beliefs and tax payments than information on fine rates. Methodically, these considerations become particularly important when descriptions or vignettes are used besides objective information. PMID:25923770

  16. Does the sole description of a tax authority affect tax evasion?--the impact of described coercive and legitimate power.

    Science.gov (United States)

    Hartl, Barbara; Hofmann, Eva; Gangl, Katharina; Hartner-Tiefenthaler, Martina; Kirchler, Erich

    2015-01-01

    Following the classic economic model of tax evasion, taxpayers base their tax decisions on economic determinants, like fine rate and audit probability. Empirical findings on the relationship between economic key determinants and tax evasion are inconsistent and suggest that taxpayers may rather rely on their beliefs about tax authority's power. Descriptions of the tax authority's power may affect taxpayers' beliefs and as such tax evasion. Experiment 1 investigates the impact of fines and beliefs regarding tax authority's power on tax evasion. Experiments 2-4 are conducted to examine the effect of varying descriptions about a tax authority's power on participants' beliefs and respective tax evasion. It is investigated whether tax evasion is influenced by the description of an authority wielding coercive power (Experiment 2), legitimate power (Experiment 3), and coercive and legitimate power combined (Experiment 4). Further, it is examined whether a contrast of the description of power (low to high power; high to low power) impacts tax evasion (Experiments 2-4). Results show that the amount of fine does not impact tax payments, whereas participants' beliefs regarding tax authority's power significantly shape compliance decisions. Descriptions of high coercive power as well as high legitimate power affect beliefs about tax authority's power and positively impact tax honesty. This effect still holds if both qualities of power are applied simultaneously. The contrast of descriptions has little impact on tax evasion. The current study indicates that descriptions of the tax authority, e.g., in information brochures and media reports, have more influence on beliefs and tax payments than information on fine rates. Methodically, these considerations become particularly important when descriptions or vignettes are used besides objective information.

  17. Does the sole description of a tax authority affect tax evasion?--the impact of described coercive and legitimate power.

    Directory of Open Access Journals (Sweden)

    Barbara Hartl

    Full Text Available Following the classic economic model of tax evasion, taxpayers base their tax decisions on economic determinants, like fine rate and audit probability. Empirical findings on the relationship between economic key determinants and tax evasion are inconsistent and suggest that taxpayers may rather rely on their beliefs about tax authority's power. Descriptions of the tax authority's power may affect taxpayers' beliefs and as such tax evasion. Experiment 1 investigates the impact of fines and beliefs regarding tax authority's power on tax evasion. Experiments 2-4 are conducted to examine the effect of varying descriptions about a tax authority's power on participants' beliefs and respective tax evasion. It is investigated whether tax evasion is influenced by the description of an authority wielding coercive power (Experiment 2, legitimate power (Experiment 3, and coercive and legitimate power combined (Experiment 4. Further, it is examined whether a contrast of the description of power (low to high power; high to low power impacts tax evasion (Experiments 2-4. Results show that the amount of fine does not impact tax payments, whereas participants' beliefs regarding tax authority's power significantly shape compliance decisions. Descriptions of high coercive power as well as high legitimate power affect beliefs about tax authority's power and positively impact tax honesty. This effect still holds if both qualities of power are applied simultaneously. The contrast of descriptions has little impact on tax evasion. The current study indicates that descriptions of the tax authority, e.g., in information brochures and media reports, have more influence on beliefs and tax payments than information on fine rates. Methodically, these considerations become particularly important when descriptions or vignettes are used besides objective information.

  18. Trapped magnetic field of a superconducting bulk magnet in high- T sub c RE-Ba-Cu-O

    CERN Document Server

    Fujimoto, H; Higuchi, T; Nakamura, Y; Kamijo, H; Nagashima, K; Murakami, M

    1999-01-01

    Superconducting magnets made of high-T sub c superconductors are promising for industrial applications. It is well known that REBa sub 2 Cu sub 3 O sub 7 sub - sub x and LRE (light rare-earth) Ba sub 2 Cu sub 3 O sub 7 sub - sub x superconductors prepared by melt processes have a high critical current density, J sub c , at 77 K and high magnetic fields. Therefore, the materials are very prospective for high magnetic field application as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. LREBaCuO bulks, compared with REBaCuO bulks, exhibit a larger J sub c in high magnetic fields and a much improved irreversibility field, H sub i sub r sub r , at 77 K. In this study, we discuss the possibility and trapped field properties of a superconducting bulk magnet, as well as the melt processing for bulk superconductors and their characteristic superconducting properties. One of the applications is a superconducting magnet for the future magnetically levitated (Maglev) train.

  19. The physics of ultra-high-density magnetic recording

    CERN Document Server

    Ek, Johannes; Weller, Dieter

    2001-01-01

    In this book, 17 experts in magnetic recording focus on the underlying physical mechanisms that play crucial roles in medium and transducer development for high areal density disk drives. In 11 chapters, an examination is made of the fundamental physical concepts and their impact on recording mechanisms, with special emphasis on thin-film longitudinal, perpendicular, patterned and nanoparticle media. Theoretical and experimental investigations are presented which serve to enhance our basic understanding of thin-film dynamics, medium dynamics and thermal effects. Fundamental aspects of magnetotransport are discussed and an overview is given of recording head designs.

  20. Design and development of ITER high-frequency magnetic sensor

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y., E-mail: Yunxing.Ma@iter.org [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Fircroft Engineering, Lingley House, 120 Birchwood Point, Birchwood Boulevard, Warrington, WA3 7QH (United Kingdom); Vayakis, G. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Begrambekov, L.B. [National Research Nuclear University (MEPhI), 115409, Moscow, Kashirskoe shosse 31 (Russian Federation); Cooper, J.-J. [Culham Centre for Fusion Energy (CCFE), Abingdon, Oxfordshire OX14 3DB (United Kingdom); Duran, I. [IPP Prague, Za Slovankou 1782/3, 182 00 Prague 8 (Czech Republic); Hirsch, M.; Laqua, H.P. [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstraße 1, D-17491 Greifswald (Germany); Moreau, Ph. [CEA Cadarache, 13108 Saint Paul lez Durance Cedex (France); Oosterbeek, J.W. [Eindhoven University of Technology (TU/e), PO Box 513, 5600 MB Eindhoven (Netherlands); Spuig, P. [CEA Cadarache, 13108 Saint Paul lez Durance Cedex (France); Stange, T. [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstraße 1, D-17491 Greifswald (Germany); Walsh, M. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France)

    2016-11-15

    Highlights: • ITER high-frequency magnetic sensor system has been designed. • Prototypes have been successfully manufactured. • Manufactured prototypes have been tested in various labs. • Test results experimentally validated the design. - Abstract: High-frequency (HF) inductive magnetic sensors are the primary ITER diagnostic set for Toroidal Alfvén Eigenmodes (TAE) detection, while they also supplement low-frequency MHD and plasma equilibrium measurements. These sensors will be installed on the inner surface of ITER vacuum vessel, operated in a harsh environment with considerable neutron/nuclear radiation and high thermal load. Essential components of the HF sensor system, including inductive coil, electron cyclotron heating (ECH) shield, electrical cabling and termination load, have been designed to meet ITER measurement requirements. System performance (e.g. frequency response, thermal conduction) has been assessed. A prototyping campaign was initiated to demonstrate the manufacturability of the designed components. Prototypes have been produced according to the specifications. A series of lab tests have been performed to examine assembly issues and validate electrical and thermo-mechanical aspects of the design. In-situ microwave radiation test has been conducted in the MISTRAL test facility at IPP-Greifswald to experimentally examine the microwave shielding efficiency and structural integrity of the ECH shield. Low-power microwave attenuation measurement and scanning electron microscopic inspection were conducted to probe and examine the quality of the metal coating on the ECH shield.

  1. High Frequency Amplitude Detector for GMI Magnetic Sensors

    Directory of Open Access Journals (Sweden)

    Aktham Asfour

    2014-12-01

    Full Text Available A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.

  2. Strong magnetic fields in normal galaxies at high redshift

    Science.gov (United States)

    Bernet, Martin L.; Miniati, Francesco; Lilly, Simon J.; Kronberg, Philipp P.; Dessauges-Zavadsky, Miroslava

    2008-07-01

    The origin and growth of magnetic fields in galaxies is still something of an enigma. It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale. It was recently demonstrated that field strengths as traced by rotation measures of distant (and hence ancient) quasars are comparable to those seen today, but it was unclear whether the high fields were in the unusual environments of the quasars themselves or distributed along the lines of sight. Here we report high-resolution spectra that demonstrate that the quasars with strong MgII absorption lines are unambiguously associated with larger rotation measures. Because MgII absorption occurs in the haloes of normal galaxies along the sightlines to the quasars, this association requires that organized fields of surprisingly high strengths are associated with normal galaxies when the Universe was only about one-third of its present age.

  3. Magnetic Implosion for Novel Strength Measurements at High Strain Rates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.; Preston, D.L.; Bartsch, R.R.; Bowers, R.L.; Holtkamp, D.; Wright, B.L.

    1998-10-19

    Recently Lee and Preston have proposed to use magnetic implosions as a new method for measuring material strength in a regime of large strains and high strain rates inaccessible to previously established techniques. By its shockless nature, this method avoids the intrinsic difficulties associated with an earlier approach using high explosives. The authors illustrate how the stress-strain relation for an imploding liner can be obtained by measuring the velocity and temperature history of its inner surface. They discuss the physical requirements that lead us to a composite liner design applicable to different test materials, and also compare the code-simulated prediction with the measured data for the high strain-rate experiments conducted recently at LANL. Finally, they present a novel diagnostic scheme that will enable us to remove the background in the pyrometric measurement through data reduction.

  4. Construction of a high-performance magnetic enzyme nanosystem for rapid tryptic digestion

    OpenAIRE

    Gong Cheng; Si-Yang Zheng

    2014-01-01

    A magnetic enzyme nanosystem have been designed and constructed by a polydopamine (PDA)-modification strategy. The magnetic enzyme nanosystem has well defined core-shell structure and a relatively high saturation magnetization (Ms) value of 48.3 emu g−1. The magnetic enzyme system can realize rapid, efficient and reusable tryptic digestion of proteins by taking advantage of its magnetic core and biofunctional shell. Various standard proteins (e.g. cytochrome C (Cyt-C), myoglobin (MYO) and bov...

  5. High-field magnetic transition in Er sub 2 Fe sub 14 B

    Energy Technology Data Exchange (ETDEWEB)

    Radwanski, R.J.; Boer, F.R. de (Natuurkundig Lab., Univ. van Amsterdam (Netherlands)); Zhong, X.P.; Yang, F.M.; Li, J.Y. (Magnetism Lab., Inst. of Physics, Academia Sinica, Beijing (China)); Kohashi, T.; Ono, M.; Date, M. (Dept. of Physics, Osaka Univ. (Japan)); Yamagishi, A. (Research Center for Extreme Materials, Osaka Univ. (Japan))

    1991-10-01

    Field-induced transitions in quasi-ternary Er{sub 2}Fe{sub 14}B compounds have been revealed by means of magnetization measurements at high magnetic fields. The high-field studies for Er{sub 2}Fe{sub 14}B, in particular the modest differential high-field susceptibility and the formation of a non-collinear magnetic structure at 42 T, do not confirm the substantial canted magnetic structure at low fields. (orig.).

  6. Magnetism in meteorites. [terminology, principles and techniques

    Science.gov (United States)

    Herndon, J. M.; Rowe, M. W.

    1974-01-01

    An overview of this subject is presented. The paper includes a glossary of magnetism terminology and a discussion of magnetic techniques used in meteorite research. These techniques comprise thermomagnetic analysis, alternating field demagnetization, thermal demagnetization, magnetic anisotropy, low-temperature cycling, and coercive forces, with emphasis on the first method. Limitations on the validity of paleointensity determinations are also discussed.

  7. An induction heating device using planar coil with high amplitude alternating magnetic fields for magnetic hyperthermia.

    Science.gov (United States)

    Wu, Zuhe; Zhuo, Zihang; Cai, Dongyang; Wu, Jian'an; Wang, Jie; Tang, Jintian

    2015-01-01

    Induction heating devices using the induction coil and magnetic nanoparticles (MNPs) are the way that the magnetic hyperthermia is heading. To facilitate the induction heating of in vivo magnetic nanoparticles in hyperthermia experiments on large animals. An induction heating device using a planar coil was designed with a magnetic field frequency of 328 kHz. The coil's magnetic field distribution and the device's induction heating performance on different concentrations of magnetic nanoparticles were measured. The alternating magnetic field produced in the axis position 165 mm away from the coil center is 40 Gs in amplitude; magnetic nanoparticles with a concentration higher than 80 mg. mL-1 can be heated up rapidly. Our results demonstrate that the device can be applied not only to in vitro and in small animal experiments of magnetic hyperthermia using MNPs, but also in large animal experiments.

  8. The role of justice in the former Yugoslavia: antidote or placebo for coercive appeasement?

    National Research Council Canada - National Science Library

    Williams, Paul R; Taft, Patricia

    2003-01-01

      This article conducts a historical analysis of the interaction between the international policy approach of coercive appeasement and the norm and institutions of justice in the conflicts in the former Yugoslavia...

  9. Solutions to quasilinear equations of $N$-biharmonic type with degenerate coercivity

    Directory of Open Access Journals (Sweden)

    Sami Aouaoui

    2014-10-01

    Full Text Available In this article we show the existence of multiple solutions for quasilinear equations in divergence form with degenerate coercivity. Our strategy is to combine a variational method and an iterative technique to obtain the solutions.

  10. Magnetically-related properties of bismuth containing high Tc superconductors

    Science.gov (United States)

    Vezzoli, Gary C.; Chen, M. F.; Craver, F.; Safari, A.; Moon, B. M.; Lalevic, B.; Burke, Terence; Shoga, M.

    1990-08-01

    The effect of magnetic fields to 15 T on electrical resistance has been measured for the BiSrCaCuO superconductor at precise temperatures during the transition to the superconducting state from pre-onset conditions to essentially zero resistance conditions. The results show that the temperature at which the magnetic field causes a divergence in the resistance versus 1000/ T curve is approximately the same temperature as the value at which, during cooling, the positive Hall coefficient begins its abrupt descent to zero. This temperature gives the best measure of Tc. It is also shown that small oscillations of low frequency start near onset conditions, the amplitude of which at a given temperature is B-field dependent. Additionally, Hall effect studies as a function of temperature at 4 T in three separate experiments (including high Tc BiSrCaCu PbO of > 90% theoretical density) show that sharp delta-function-like peaks in + RH are observed near Tc and are superimposed on a broader maximum. The Hall data are explicable in terms of exciton formation and ionization. The bound holes associated with these excitons are believed to be the mediators producing Cooper-pairing, and scale very well with Tc for all the known high Tc oxides.

  11. 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.

  12. Novel microwave assisted chemical synthesis of Nd₂Fe₁₄B hard magnetic nanoparticles.

    Science.gov (United States)

    Swaminathan, Viswanathan; Deheri, Pratap Kumar; Bhame, Shekhar Dnyaneswar; Ramanujan, Raju Vijayaraghavan

    2013-04-07

    The high coercivity and excellent energy product of Nd2Fe14B hard magnets have led to a large number of high value added industrial applications. Chemical synthesis of Nd2Fe14B nanoparticles is challenging due to the large reduction potential of Nd(3+) and the high tendency for Nd2Fe14B oxidation. We report the novel synthesis of Nd2Fe14B nanoparticles by a microwave assisted combustion process. The process consisted of Nd-Fe-B mixed oxide preparation by microwave assisted combustion, followed by the reduction of the mixed oxide by CaH2. This combustion process is fast, energy efficient and offers facile elemental substitution. The coercivity of the resulting powders was ∼8.0 kOe and the saturation magnetization was ∼40 emu g(-1). After removal of CaO by washing, saturation magnetization increased and an energy product of 3.57 MGOe was obtained. A range of magnetic properties was obtained by varying the microwave power, reduction temperature and Nd to Fe ratio. A transition from soft to exchange coupled to hard magnetic properties was obtained by varying the composition of NdxFe1-xB8 (x varies from 7% to 40%). This synthesis procedure offers an inexpensive and facile platform to produce exchange coupled hard magnets.

  13. Ultra-High Intensity Magnetic Field Generation in Dense Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, Nathaniel J. [Princeton Univ., NJ (United States)

    2014-01-08

    The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereas the efficient generation of electric current in low-­energy-­density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­energy-­density plasma the ideas for steady-­state current drive developed for low-­energy-­density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­energy-­density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new forms of current drive in regimes appropriate for new fusion concepts.

  14. Raman spectroscopy of graphite in high magnetic fields

    Science.gov (United States)

    Kim, Younghee; Lombardo, Antonio; Kalugin, Nikolai G.; Kono, Junichiro; Ferrari, Andrea C.; Smirnov, Dmitry

    2011-03-01

    Recently, much attention has been paid to electron-phonon coupling in graphene. In particular, significant re-normalization and broadening of long-wavelength optical phonons are predicted to occur through resonant interaction with Landau-quantized Dirac fermions. We report here on a high-field magneto-Raman spectroscopy study of highly-oriented pyrolytic graphite (HOPG) and natural graphite at temperatures down to 5 K and in magnetic fields up to 45 T. The E2 g graphite phonon line exhibits anticrossing-like behavior at approximately 30 T, which we attribute to the magneto-phonon resonance (MPR) of graphite's massless holes at the H-point. Additionally, we observed features related to inter-Landau-level transitions at the K-point of graphite. We also observed weak graphene-like signatures of MPR, indicating the existence of graphene flakes on the graphite surface.

  15. Static high-gradient magnetic fields affect the functionality of monocytic cells

    Czech Academy of Sciences Publication Activity Database

    Syrovets, T.; Schmidt, Z.; Buechele, B.; Zablotskyy, Vitaliy A.; Dejneka, Alexandr; Dempsey, N.; Simmet, T.

    2014-01-01

    Roč. 28, č. 1 (2014), s. 1-2 ISSN 0892-6638 Institutional support: RVO:68378271 Keywords : static high-gradient * magnet ic fields * affect the functionality * monocytic cells Subject RIV: BM - Solid Matter Physics ; Magnet ism

  16. A new method of determining the reversible magnetization loop of bulk high-temperature superconductors

    NARCIS (Netherlands)

    Ermolaev, YS; Rudnev, IA

    2004-01-01

    A new method of calculation of the magnetization loop of bulk high-temperature superconductors is proposed which employs the results of measurements of the magnetic levitation force. (C) 2004 MAIK "Nauka / Interperiodica".

  17. Magnetization reversal processes of isotropic permanent magnets with various inter-grain exchange interactions

    Directory of Open Access Journals (Sweden)

    Hiroshi Tsukahara

    2017-05-01

    Full Text Available We performed a large-scale micromagnetics simulation on a supercomputing system to investigate the properties of isotropic nanocrystalline permanent magnets consisting of cubic grains. In the simulation, we solved the Landau–Lifshitz–Gilbert equation under a periodic boundary condition for accurate calculation of the magnetization dynamics inside the nanocrystalline isotropic magnet. We reduced the inter-grain exchange interaction perpendicular and parallel to the external field independently. Propagation of the magnetization reversal process is inhibited by reducing the inter-grain exchange interaction perpendicular to the external field, and the coercivity is enhanced by this restraint. In contrast, when we reduce the inter-grain exchange interaction parallel to the external field, the coercivity decreases because the magnetization reversal process propagates owing to dipole interaction. These behaviors show that the coercivity of an isotropic permanent magnet depends on the direction of the inter-grain exchange interaction.

  18. Design of High Performance Permanent-Magnet Synchronous Wind Generators

    Directory of Open Access Journals (Sweden)

    Chun-Yu Hsiao

    2014-11-01

    Full Text Available This paper is devoted to the analysis and design of high performance permanent-magnet synchronous wind generators (PSWGs. A systematic and sequential methodology for the design of PMSGs is proposed with a high performance wind generator as a design model. Aiming at high induced voltage, low harmonic distortion as well as high generator efficiency, optimal generator parameters such as pole-arc to pole-pitch ratio and stator-slot-shoes dimension, etc. are determined with the proposed technique using Maxwell 2-D, Matlab software and the Taguchi method. The proposed double three-phase and six-phase winding configurations, which consist of six windings in the stator, can provide evenly distributed current for versatile applications regarding the voltage and current demands for practical consideration. Specifically, windings are connected in series to increase the output voltage at low wind speed, and in parallel during high wind speed to generate electricity even when either one winding fails, thereby enhancing the reliability as well. A PMSG is designed and implemented based on the proposed method. When the simulation is performed with a 6 Ω load, the output power for the double three-phase winding and six-phase winding are correspondingly 10.64 and 11.13 kW. In addition, 24 Ω load experiments show that the efficiencies of double three-phase winding and six-phase winding are 96.56% and 98.54%, respectively, verifying the proposed high performance operation.

  19. High magnetic field properties of Fe-pnictide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kurth, Fritz

    2015-11-20

    The recent discovery of high-temperature superconductivity in Fe-based materials triggered worldwide efforts to investigate their fundamental properties. Despite a lot of similarities to cuprates and MgB{sub 2}, important differences like near isotropic behaviour in contrast to cuprates and the peculiar pairing symmetry of the order parameter (OP) have been reported. The OP symmetry of Fe-based superconductors (FBS) was theoretically predicted to be of so-called s± state prior to various experimental works. Still, most of the experimental results favour the s± scenario; however, definitive evidence has not yet been reported. Although no clear understanding of the superconducting mechanisms yet exists, potential applications such as high-field magnets and Josephson devices have been explored. Indeed, a lot of reports about FBS tapes, wires, and even SQUIDs have been published to this date. In this thesis, the feasibility of high-field magnet applications of FBS is addressed by studying their transport properties, involving doped BaFe{sub 2}As{sub 2} (Ba-122) and LnFeAs(O,F) [Ln=Sm and Nd]. Particularly, it is important to study physical properties in a sample form (i.e. thin films) that is close to the conditions found in applications. However, the realisation of epitaxial FBS thin films is not an easy undertaking. Recent success in growing epitaxial FBS thin films opens a new avenue to delve into transport critical current measurements. The information obtained through this research will be useful for exploring high-field magnet applications. This thesis consists of 7 chapters: Chapter 1 describes the motivation of this study, the basic background of superconductivity, and a brief summary of the thin film growth of FBS. Chapter 2 describes experimental methods employed in this study. Chapter 3 reports on the fabrication of Co-doped Ba-122 thin films on various substrates. Particular emphasis lies on the discovery of fluoride substrates to be beneficial for

  20. 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...

  1. 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...

  2. High field magnet program at Brookhaven National Laboratory

    CERN Document Server

    Ghosh, A; Muratore, J; Parker, B; Sampson, W; Wanderer, P J; Willen, E

    2000-01-01

    The magnet program at Brookhaven National Laboratory (BNL) is focussed on superconducting magnets for particle accelerators. The effort includes magnet production at the laboratory and in industry, magnet R&D, and test facilities for magnets and superconductors. Nearly 2000 magnets-dipoles, quadrupoles, sextupoles and correctors for the arc and insertion regions-were produced for the Relativistic Heavy Ion Collider (RHIC), which is being commissioned. Currently, production of helical dipoles for the polarized proton program at RHIC, insertion region dipoles for the Large Hadron Collider (LHC) at CERN, and an insertion magnet system for the Hadron-Elektron-Ring- Analage (HERA) collider at Deutsches Elektronen-Synchrotron (DESY) is underway. The R&D effort is exploring dipoles with fields above 10 T for use in post-LHC colliders. Brittle superconductors-Nb/sub 3/Sn or HTS-are being used for these magnets. The superconductor test facility measures short-sample currents and other characteristics of sample...

  3. Influence of the phenomena occurring at the interface between L1{sub 0}-ordered-FePt and Fe on the coercivity behavior

    Energy Technology Data Exchange (ETDEWEB)

    Carbucicchio, Massimo, E-mail: massimo.carbucicchio@ino.it [University of Parma, Physics Department (Italy)

    2016-12-15

    L1{sub 0}-ordered FePt/Fe thin bi-layers were grown using a molecular beam epitaxy onto (100)-MgO substrates changing the soft Fe layer thickness. The study of the intermixing phenomena occurring at the hard/soft interfaces was carried out using surface Mössbauer spectroscopy. The magnetic properties of the samples were analyzed with a magneto-optical Kerr effect magnetometer. The surface morphology and the magnetic domains were analyzed with an UHV atomic and magnetic force microscopy in tapping and lift mode respectively.The present work clearly demonstrates that the degree of interface intermixing and reactions is the responsible for the coercivity behavior in exchange-spring magnets.

  4. Magnetic properties and potential barrier between crystallites model of MgGa{sub 2-x}Fe{sub x}O{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, V.A. dos S.; Rubinger, R.M.; Oliveira, A.F.; Mendonca, C.S.P.; Silva, M.R. da, E-mail: vanderalkmin@gmail.com, E-mail: rero@unifei.edu.br, E-mail: adhimarflavio@unifei.edu.br, E-mail: sales.claudiney21@gmail.com, E-mail: mrsilva@unifei.edu.br [Universidade Federal de Itajuba (UNIFEI), MG (Brazil). Instituto de Fisica e Quimica

    2016-10-15

    The aim of this work was to investigate the magnetic properties and the electrical conductivity temperature dependence associated to the potential barrier between the crystallites model. Gallium and magnesium containing spinel ceramic has low magnetic coercivity and high electrical resistivity. MgGa{sub 2-x}Fe{sub x}O{sub 4} samples (x= 0.01, 0.05, 0.15, 0.25, 0.35) were prepared by solid-state method and sintered at 800 °C for 8 h. X-ray diffraction analysis confirmed the formation of a single phase with compact cubic spinel structure. The magnetic measurements show that the saturation magnetization and remanence of all samples increased with increasing iron concentration. The coercive field decreased up to the concentration x= 0.15, and above x= 0.25 it was observed an increase in the coercive field. Through electrical characterization it was found that the samples presented highly insulating behavior for x= 0.01, and further increase in x above 0.15 gives a semiconductor behavior compatible with the potential barrier between the crystallites model, i.e. fulfills the condition L/2 > L{sub D} (crystallite size L in comparison with the Debye length L{sub D}), and the conduction is limited by potential barriers between the crystallites. (author)

  5. CURRENT SITUATION AND PROSPECTS OF PRODUCTION AND RESERVES OF PERMANENT MAGNETS OF RARE EARTHS: BRAZIL × WORLD

    Directory of Open Access Journals (Sweden)

    Franciele Weschenfelder

    2012-12-01

    Full Text Available Generating energy from renewable sources is not an easy task since it requires different types of technologies, which can add much cost to the system. For this reason, investment in research in this area can be an alternative for economic feasibility of wind power plants, for example. One line of research in this area is the study of new materials such as permanent magnets, with even better properties. These magnets, when used in wind generators add many advantages in the operation there of, and a high torque/volume. For this application it is necessary that these magnets have high coercive field (Hc and high remanent induction (Br. Brazil still has no competition in the industry of permanent magnets, so many studies by government and private enterprise are under development in the country. There is a special focus to the Rare Earths Magnets, the primary raw material for production of permanent magnets.

  6. Microstructure and magnetic properties of Mn-X-N (X: Ni, Zr, and B) sintered alloys

    Energy Technology Data Exchange (ETDEWEB)

    Isogai, K. [NEC TOKIN Corporation, Sendai, Miyagi 982-8510 (Japan)]. E-mail: isogai@nec-tokin.com; Matsumoto, H. [NEC TOKIN Corporation, Sendai, Miyagi 982-8510 (Japan); Sugimoto, S. [Department of Materials Science, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai, Miyagi 980-8579 (Japan)

    2007-03-15

    Microstructure and magnetic properties of Mn-X-N (X: Ni, Zr, and B) alloy system were investigated in this study. The samples showed low remanence; however, relatively high coercivities of 0.5-4.4 kOe (40-350 kA/m) were obtained in the Mn-Ni-N system. Scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX) and transmission electron microscopy-energy dispersive X-ray spectrometry (TEM-EDX) analyses revealed that the Mn-Ni-N sample with high coercivity consists of a lamellar structure with the spacing of 0.5-2 {mu}m. It is also found that the lamellar structure is composed of two phases with composition of 97.4 at% Mn-2.6 at% Ni and 86.7 at% Mn-13.3 at% Ni.

  7. Plasmoid Instability in High-Lundquist-Number Magnetic Reconnection

    Science.gov (United States)

    Huang, Yi-Min

    2012-10-01

    Our understanding of magnetic reconnection in resistive magnetohydrodynamics has gone through a fundamental change in recent years. The conventional wisdom is that magnetic reconnection mediated by resistivity is slow in high Lundquist (S) plasmas, due to the S-1/2 scaling of reconnection rate predicted by the classical Sweet-Parker theory. However, recent studies showed that when S exceeds a critical value ˜10^4, the Sweet-Parker current sheet is unstable to a super-Alfvenic plasmoid instability, with a growth rate that increases with S [1]. Consequently, the reconnection layer changes to a chain of plasmoids connected by secondary current sheets that, in turn, may become unstable again. Eventually the reconnection layer will tend to a statistical steady state governed by complex dynamics of plasmoid formation and plasmoid loss due to advection and coalescence. The averaged reconnection rate in this regime is nearly independent of S [2,3], and the distribution function f(ψ) of magnetic fluxes ψ in plasmoids follows a power-law f˜&-1circ;. When Hall effects are included, the plasmoid instability may trigger onset of Hall reconnection even when the conventional criterion for onset is not satisfied. In addition to the usual single X-point topology of Hall reconnection, our large-scale resistive Hall MHD simulations reveal a novel intermediate regime, where formation of new plasmoids is observed after onset of Hall reconnection [4]. Qualitatively similar results have also been found when resistivity is replaced by hyper-resistivity. Our findings suggest that plasmoid formation may be a generic feature of magnetic reconnection in large systems, regardless of the mechanism of breaking the frozen-in condition. (In collaboration with A. Bhattacharjee and B. P. Sullivan).[4pt] [1] N. F. Loureiro, A. A. Schekochihin, and S. C. Cowley, Phys. Plasmas 14, 100703 (2007).[0pt] [2] A. Bhattacharjee, Y.-M. Huang, H. Yang, and B. Rogers, Phys. Plasmas 16, 112102 (2009).[0pt] [3

  8. Structural, magnetic, and electronic properties of high moment FeCo nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zehani, K., E-mail: zehani@icmpe.cnrs.fr [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France); Bez, R. [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France); LMOP, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis (Tunisia); Boutahar, A. [LPMMAT, Université Hassan II, Faculté des Sciences Ain Chock, B.P.5366 Maârif, Route d’El Jadida, km-8, Casablanca (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Lassri, H. [LPMMAT, Université Hassan II, Faculté des Sciences Ain Chock, B.P.5366 Maârif, Route d’El Jadida, km-8, Casablanca (Morocco); Moscovici, J. [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France); Mliki, N. [LMOP, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis (Tunisia); Bessais, L. [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France)

    2014-04-05

    Highlights: • The nanoparticles cobalt ferrite was synthesized in polyol medium (10 nm). • Subsequently, the ferrite is annealed under argon at 873 K for different times. • After annealing, we have obtained of nanoparticles FeCo. • Their Structural, electronic, and magnetic properties have been presented. • The sample annealed at 873 K for 4 h exhibits the best M{sub s} (M{sub s} = 235 emu g{sup −1}). -- Abstract: Soft-magnetic Fe{sub 55}Co{sub 45} alloy nanoparticles have been successfully synthesized by the polyol reduction process followed by annealing under argon. The diethylene glycol (DEG) was used as solvent and reducing agent simultaneously in this process. The synthesized samples of nanoparticles were annealed at 873 K for different times. The alloy formation processes, the evolution of the microstructure, the magnetic properties, and the DOS calculation have been investigated before and after samples annealing. The X-ray diffraction of the synthesized product before annealing shows that a cobalt ferrite is spinel structure of crystallite size of about 10 nm. X-ray diffraction analysis of the samples annealed at 873 K for different times also shows that of the FeCo alloy has been obtained by reducing the cobalt ferrite. It has been confirmed the formation of a body-centered-cubic (bcc) single phase structure where the wt.% increases with annealing times leading to a pure phase after annealing during 4 h. These results are confirmed by transmission electron microscopy study. The saturation magnetization of the Fe–Co alloys increases with annealing time, indicating an increasing homogeneity in composition and the single bcc FeCo phase formation. The highest saturation magnetization of 235 emu g{sup −1}with a low coercivity of 76 Oe was obtained for the Fe{sub 55}Co{sub 45}nanoparticles annealed during 4 h. The local random anisotropy constant K{sub L} has been extracted. This work presents also detailed information about total, and atom

  9. 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.

  10. Dynamics of Coulomb correlations in semiconductors in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Fromer, Neil Alan [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    Current theories have been successful in explaining many nonlinear optical experiments in undoped semiconductors. However, these theories require a ground state which is assumed to be uncorrelated. Strongly correlated systems of current interest, such as a two dimensional electron gas in a high magnetic field, cannot be explained in this manner because the correlations in the ground state and the low energy collective excitations cause a breakdown of the conventional techniques. We perform ultrafast time-resolved four-wave mixing on $n$-modulation doped quantum wells, which contain a quasi-two dimensional electron gas, in a large magnetic field, when only a single Landau level is excited and also when two levels are excited together. We find evidence for memory effects and as strong coupling between the Landau levels induced by the electron gas. We compare our results with simulations based on a new microscopic approach capable of treating the collective effects and correlations of the doped electrons, and find a good qualitative agreement. By looking at the individual contributions to the model, we determine that the unusual correlation effects seen in the experiments are caused by the scattering of photo-excited electron-hole pairs with the electron gas, leading to new excited states which are not present in undoped semiconductors, and also by exciton-exciton interactions mediated by the long-lived collective excitations of the electron gas, inter-Landau level magnetoplasmons.

  11. Desorption of harmful hydrocarbon compounds in soil using micron-sized magnetic particles and high-frequency magnetic fields

    Directory of Open Access Journals (Sweden)

    Bailey S. Tye

    2017-10-01

    Full Text Available This research looks at the use of high frequency (HF magnetic fields to desorb/reduce harmful chemical compounds within gasoline and diesel that commonly leak out of underground storage tanks. Using a multi-strand coil design, measured magnetic fields of over 3 kilo-amperes per meter are generated at an optimal frequency of 117 kHz without skin-depth losses, and without the use of expensive super-conductors or liquid-cooled mechanisms. This high frequency magnetic field is successfully used in non-contact-based magnetic heating and desorption of Gasoline and Diesel mixed with sand, water and easily-dispersible, benign micrometer-sized iron filings, used as a magnetic absorber. Gas chromatography (GC tests done on magnetically-heated Gasoline-soil and Diesel-soil mixtures show desorption/reduction of gasoline and diesel by 44% and 51% respectively, but desorption/reduction of harmful BTEX compounds and other chemical irritants within Gasoline and Diesel by 28–66% after only 80 minutes of magnetic heating. Review of remediation/desorption methods show magnetic fields fare favorably in comparison to other methods that require longer treatment period or the use of secondary pollutants at reducing hydrocarbon and BTEX compounds in them. Keywords: Engineering, Applied sciences, Environmental science, Electrical engineering

  12. Magnetic and structural properties of nano sized Dy-doped cobalt ferrite synthesized by co-precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, Z., E-mail: Zahra_kr64@yahoo.com [Department of Materials Engineering, Institute of Mechanical Engineering, University of Tabriz, Tabriz 51666-16471 (Iran, Islamic Republic of); Mohammadifar, Y.; Shokrollahi, H. [Electroceramics Group, Department of Materials Science and Engineering, Shiraz University of Technology, Shiraz (Iran, Islamic Republic of); Asl, Sh. Khameneh [Department of Materials Engineering, Institute of Mechanical Engineering, University of Tabriz, Tabriz 51666-16471 (Iran, Islamic Republic of); Yousefi, Gh. [Center for Pharmaceutical Nanotechnology and Biomaterials, Pharmaceutical Sciences Research Center, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz (Iran, Islamic Republic of); Department of Pharmaceutics, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz (Iran, Islamic Republic of); Karimi, L. [Materials Science and Engineering Department, Islamic Azad University Ahvaz Branch, Ahvaz (Iran, Islamic Republic of)

    2014-06-01

    Regarding the various applications of cobalt ferrite as a magnetic ceramic in various scientific and industrial categories, it is essential to modify and optimize its microstructural and magnetic features. Chemical composition (doped elements and their quantities) is a determining factor which has been studied in this research. For this purpose, cobalt-dysprosium ferrite ceramic nanoparticles with the chemical formula Co{sub 1−x}Dy{sub x}Fe{sub 2}O{sub 4} (x=0, 0.01, 0.03, 0.05, 0.1) were synthesized by the co-precipitation chemical method and then analyzed from the structural and magnetic perspectives. The desirable spinel phase formation was confirmed via x-ray diffractometry, and the other crystallographic parameters and cation distribution were calculated. The microscopic image of the samples showed 15 nm particles. The type and strength of the interionic bonds were determined by infrared spectroscopy. The hysteresis loop of the material was affected noticeably by doped elements as the room temperature saturation magnetization was decreased, but the residual magnetization and coercivity of ferrite were promoted by 50 and 150% after adding dysprosium, respectively. The maximum anisotropy constant, which is equal to 19.1 erg/g for undoped cobalt ferrite, was increased to 45.2 erg/g by doping 0.05 dysprosium. It is worth mentioning that introducing dopants into the lattice led to a great decrease in Curie temperature. - Highlights: • Magnetic and structural studies of Dy{sup 3+}–Co–ferrite are investigated. • Simple co-precipitation method involving less energy and low-cost is used. • The nanoparticles with high coercivity, magnetization and loop area are obtained. • The composition Co{sub 0.95}Dy{sub 0.05}Fe{sub 2}O{sub 4} has the maximum coercivity and high residual magnetization.

  13. A generalized view of self-citation: direct, co-author, collaborative, and coercive induced self-citation.

    Science.gov (United States)

    Ioannidis, John P A

    2015-01-01

    The phenomenon of self-citation can present in many different forms, including direct, co-author, collaborative, and coercive induced self-citation. It can also pertain to the citation of single scientists, groups of scientists, journals, and institutions. This article presents some case studies of extreme self-citation practices. It also discusses the implications of different types of self-citation. Self-citation is not necessarily inappropriate by default. In fact, usually it is fully appropriate but often it is even necessary. Conversely, inappropriate self-citation practices may be highly misleading and may distort the scientific literature. Coercive induced self-citation is the most difficult to discover. Coercive Induced self-citation may happen directly from reviewers of articles, but also indirectly from reviewers of grants, scientific advisors who steer a research agenda, and leaders of funding agencies who may espouse spending disproportionately large funds in research domains that perpetuate their own self-legacy. Inappropriate self-citation can be only a surrogate marker of what might be much greater distortions of the scientific corpus towards conformity to specific opinions and biases. Inappropriate self-citations eventually affect also impact metrics. Different impact metrics vary in the extent to which they can be gamed through self-citation practices. Citation indices that are more gaming-proof are available and should be more widely used. We need more empirical studies to dissect the impact of different types of inappropriate self-citation and to examine the effectiveness of interventions to limit them. Copyright © 2014. Published by Elsevier Inc.

  14. Commercial-scale recycling of NdFeB-type magnets with grain boundary modification yields products with 'designer properties' that exceed those of starting materials.

    Science.gov (United States)

    Zakotnik, M; Tudor, C O

    2015-10-01

    NdFeB-type magnets dominate the market for high performance magnetic materials, yet production of 'virgin' magnets via mining is environmentally, financially and energetically costly. Hence, interest is growing in 'magnet to magnet' recycling schemes that offer the potential for cheaper, more environmentally-friendly solutions to the world's growing appetite for rare-earth based magnetic materials. Unfortunately, previously described recycling processes only partially capitalise on this potential, because the methods described to date are limited to 'laboratory scale' or operate only under ideal conditions and result in products that fail to recapture the coercivity of the starting, scrap materials. Herein, we report a commercial scale process (120 kg batches) that completely recovers the properties of the starting scrap magnets. Indeed, 'grain boundary modification', via careful addition of a proprietary mix of blended elements, produces magnets with 'designer properties' that can exceed those of the starting materials and can be closely tailored to meet a wide variety of end-user applications, including high-coercivity (>2000 kA/m), sintered magnets suitable for motor applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Tailoring Magnetic Properties in Bulk Nanostructured Solids

    Science.gov (United States)

    Morales, Jason Rolando

    Important magnetic properties and behaviors such as coercivity, remanence, susceptibility, energy product, and exchange coupling can be tailored by controlling the grain size, composition, and density of bulk magnetic materials. At nanometric length scales the grain size plays an increasingly important role since magnetic domain behavior and grain boundary concentration determine bulk magnetic behavior. This has spurred a significant amount of work devoted to developing magnetic materials with nanometric features (thickness, grain/crystallite size, inclusions or shells) in 0D (powder), 1D (wires), and 2D (thin films) materials. Large 3D nanocrystalline materials are more suitable for many applications such as permanent magnets, magneto-optical Faraday isolators etc. Yet there are relatively few successful demonstrations of 3D magnetic materials with nanoscale influenced properties available in the literature. Making dense 3D bulk materials with magnetic nanocrystalline microstructures is a challenge because many traditional densification techniques (HIP, pressureless sintering, etc.) move the microstructure out of the "nano" regime during densification. This dissertation shows that the Current Activated Pressure Assisted Densification (CAPAD) method, also known as spark plasma sintering, can be used to create dense, bulk, magnetic, nanocrystalline solids with varied compositions suited to fit many applications. The results of my research will first show important implications for the use of CAPAD for the production of exchange-coupled nanocomposite magnets. Decreases in grain size were shown to have a significant role in increasing the magnitude of exchange bias. Second, preferentially ordered bulk magnetic materials were produced with highly anisotropic material properties. The ordered microstructure resulted in changing magnetic property magnitudes (ex. change in coercivity by almost 10x) depending on the relative orientation (0° vs. 90°) of an externally

  16. Thin Magnetically Soft Wires for Magnetic Microsensors

    Directory of Open Access Journals (Sweden)

    Arcady Zhukov

    2009-11-01

    Full Text Available Recent advances in technology involving magnetic materials require development of novel advanced magnetic materials with improved magnetic and magneto-transport properties and with reduced dimensionality. Therefore magnetic materials with outstanding magnetic characteristics and reduced dimensionality have recently gained much attention. Among these magnetic materials a family of thin wires with reduced geometrical dimensions (of order of 1–30 μm in diameter have gained importance within the last few years. These thin wires combine excellent soft magnetic properties (with coercivities up to 4 A/m with attractive magneto-transport properties (Giant Magneto-impedance effect, GMI, Giant Magneto-resistance effect, GMR and an unusual re-magnetization process in positive magnetostriction compositions exhibiting quite fast domain wall propagation. In this paper we overview the magnetic and magneto-transport properties of these microwires that make them suitable for microsensor applications.

  17. Enhanced Magnetic Properties of Graphene Coated with Fe2O3 Nanoparticles.

    Science.gov (United States)

    Neupane, Suman; Hong, Haiping; Giri, Lily; Karna, Shashi P; Seifu, Dereje

    2015-09-01

    Graphene, with its unique 2D nanostructure and excellent electrical, thermal, and mechanical properties, is considered an alternative to carbon nanotubes in nanocomposites. In this study, we present a one step approach for the deposition of iron oxide (Fe2O3) nanoparticles onto graphene sheets through solution mixture. The morphology, crystallinity, and magnetic properties of as-synthesized composites were investigated. It was shown that highly crystalline Fe2O3 nanoparticles were densely and uniformly coated on graphene surface. Magnetic measurements reveal that, as compared to weak diamagnetism of pristine graphene, graphene-Fe2O3 nanocomposites display ferromagnetic behavior with coercivity of 101 Oe, saturation magnetization of 12.6 emu g(-1), and remanent magnetization of 3.13 emu g(-1) at room temperature. The enhanced magnetic performance was attributed to the homogeneous dispersion of Fe2O3 nanoparticles in graphene matrix and such nanocomposites are promising materials for applications in magnetic media and energy storage.

  18. Rock magnetic effects induced in terrestrial basalt and diabase by >20 GPa experimental spherical shock waves

    Science.gov (United States)

    Bezaeva, N. S.; Swanson-Hysell, N.; Tikoo, S. M.; Badyukov, D. D.; Kars, M. A. C.; Egli, R.; Chareev, D. A.; Fairchild, L. M.; Khakhalova, E.; Strauss, B. E.; Lindquist, A. K.

    2015-12-01

    Understanding how shock waves generated during hypervelocity impacts affect the magnetic properties of rocks is key for interpreting the paleomagnetic records of lunar rocks, meteorites, and cratered planetary surfaces. Following ref. [1], we conducted spherical shock experiments at the RFNC-VNIIFT (Snezhinsk, Russia) on (titano)magnetite-bearing basaltic lava flow and diabase dike samples from the Osler Volcanic Group of the 1.1 Ga North American Midcontinent Rift [2]. The experimental setup allows for rock magnetic and petrographic changes to be assessed for a range of shock pressures 20 GPa and above. Consistent with prior spherical shock experiments on the Saratov ordinary chondrite [1], both shocked samples exhibited concentric zonation: a central void space was surrounded by an inner layer of impact melt (Zone I, most shocked), a middle partially melted layer (Zone II), and an outer layer of unmelted rock with solid-state shock features (Zones III and IV, least shocked). These zones are petrographically different. Like Zone IV, Zone III is characterized by an intact texture, but the plagioclase grains have been transformed into diaplectic glass. Zones I-III acquired thermoremanent magnetization from shock heating. Zone IV may have undergone shock demagnetization of the pre-shock magnetization without substantial remagnetization. Shocked samples had higher coercivities than unshocked samples of the same rocks. Magnetic force and electron microscopy reveal fracturing of the Fe-Ti oxides, which likely contributes to the observed increase in coercivity in the shocked samples. Our spherical shock experiments build on prior work to show that shock at pressures greater than 20 GPa results in coercivity increase, shock demagnetization and thermal remagnetization. This work can guide future interpretations of the remanent magnetization and bulk magnetic properties of highly shocked materials from planetary surfaces. References: [1] Bezaeva N.S. et al. 2010. MAPS 45

  19. Magnetic anisotropy study of UGe{sub 2}in a static high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Sakon, T [Center for Geo-Enviromental Science, Akita University, Akita City, 010-8502 (Japan); Saito, S [Center for Geo-Enviromental Science, Akita University, Akita City, 010-8502 (Japan); Koyama, K [Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai, 980-8577 (Japan); Awaji, S [Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai, 980-8577 (Japan); Sato, I [Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai, 980-8577 (Japan); Nojima, T [Center for Low Temperature Science, Tohoku University, Katahira 2-1-1, Sendai, 980-8577 (Japan); Watanabe, K [Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai, 980-8577 (Japan); Motokawa, M [Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai, 980-8577 (Japan); Sato, N K [Department of Physics, Graduated School of Science, Nagoya University, Nagoya 464-8602 (Japan)

    2006-11-15

    UGe{sub 2} has orthorhombic C{sub mmm} crystalline symmetry and shows ferromagnetic Heavy-Fermion (HF) Superconductor, which provides superconductivity under pressure in the range from 1.0 GPa to 1.5 GPa. Magnetic field dependence of magnetization shows strong magnetic anisotropy. When a magnetic field is applied parallel to easy axis (a-axis), magnetization presents ferromagnetic behavior. At 4.2 K, which is much lower than the Curie temperature T{sub c} = 54 K. Spontaneous magnetization is 1.4 {mu}{sub B}/U, and the magnetization gradually increase with increasing field. On the contrary, when a field is applied parallel to hard axis (b-axis or c-axis), magnetization increases linearly with increasing magnetic field. As for H//b-axis, magnetization is 0.23 {mu} {sub B}/U even at 27 T. Magnetocrystalline anisotropy constant is obtained as 230 [T {mu}{sub B}] 3.4[kJ/kg] at 4.2 K. This value is comparable with rare-earth magnet Nd{sub 2}Fe{sub 17}, which is typical strongly correlated ferromagnet.

  20. Single-step gas phase synthesis of stable iron aluminide nanoparticles with soft magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Vernieres, Jerome, E-mail: Jerome.vernieres@oist.jp; Benelmekki, Maria; Kim, Jeong-Hwan; Grammatikopoulos, Panagiotis; Diaz, Rosa E. [Nanoparticles by Design Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, 1919-1 Tancha, Onna Son, Okinawa 904-0495 (Japan); Bobo, Jean-François [Centre d’Elaboration de Materiaux et d’Etudes Structurales (CEMES), 29 rue Jeanne Marvig, 31055 Toulouse Cedex 4 (France); Sowwan, Mukhles, E-mail: Mukhles@oist.jp [Nanoparticles by Design Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, 1919-1 Tancha, Onna Son, Okinawa 904-0495 (Japan); Nanotechnology Research Laboratory, Al-Quds University, P.O. Box 51000, East Jerusalem, Palestine (Country Unknown)

    2014-11-01

    Soft magnetic alloys at the nanoscale level have long generated a vivid interest as candidate materials for technological and biomedical purposes. Consequently, controlling the structure of bimetallic nanoparticles in order to optimize their magnetic properties, such as high magnetization and low coercivity, can significantly boost their potential for related applications. However, traditional synthesis methods stumble upon the long standing challenge of developing true nanoalloys with effective control over morphology and stability against oxidation. Herein, we report on a single-step approach to the gas phase synthesis of soft magnetic bimetallic iron aluminide nanoparticles, using a versatile co-sputter inert gas condensation technique. This method allowed for precise morphological control of the particles; they consisted of an alloy iron aluminide crystalline core (DO{sub 3} phase) and an alumina shell, which reduced inter-particle interactions and also prevented further oxidation and segregation of the bimetallic core. Remarkably, the as-deposited alloy nanoparticles show interesting soft magnetic properties, in that they combine a high saturation magnetization (170 emu/g) and low coercivity (less than 20 Oe) at room temperature. Additional functionality is tenable by modifying the surface of the particles with a polymer, to ensure their good colloidal dispersion in aqueous environments.

  1. Structural, magnetic, and Mössbauer spectroscopy of Cu substituted M-type hexaferrites

    Energy Technology Data Exchange (ETDEWEB)

    Awadallah, Ahmad, E-mail: ahmadmoh@yahoo.co [Physics Department, The University of Jordan, Amman 11942 (Jordan); Mahmood, Sami H., E-mail: s.mahmood@ju.edu.jo [Physics Department, The University of Jordan, Amman 11942 (Jordan); Maswadeh, Yazan, E-mail: nawabra251@gmail.com [Physics Department, The University of Jordan, Amman 11942 (Jordan); Bsoul, Ibrahim, E-mail: ibrahimbsoul@yahoo.com [Physics Department, Al al-Bayt University, Mafraq 13040 (Jordan); Awawdeh, Mufeed, E-mail: amufeed@yu.edu.jo [Physics Department, Yarmouk University, Irbid 21163 (Jordan); Mohaidat, Qassem I., E-mail: q.muhaidat@yu.edu.jo [Physics Department, Yarmouk University, Irbid 21163 (Jordan); Juwhari, Hassan, E-mail: h.juwhari@ju.edu.jo [Physics Department, The University of Jordan, Amman 11942 (Jordan)

    2016-02-15

    Highlights: • Single BaM hexaferrite structural phases with Cu substations were prepared. • The magnetocrystalline anisotropy decreased with Cu substitution. • The coercivity was significantly modified while the magnetization remained high. • Hexaferrites with 0.2–0.4 Cu possess properties suitable for magnetic recording. • Ionic distributions from structural refinement agreed with Mössbauer spectroscopy. - Abstract: BaFe{sub 12−x}Cu{sub x}O{sub 19} hexaferrites were prepared using ball milling and sintering at 1100 °C. Refinement of the X-ray diffraction patterns was carried out to determine the structural parameters and the ionic distribution over the crystallographic sites. The preferential site occupation and valence state of Cu was consistent with the results obtained from the analysis of Mössbauer spectra. Further, the magnetic parameters of the samples were discussed in light of the structural and Mössbauer analyses. The magnetic phase transition temperature was found to decrease with the level of Cu substitution, in accordance with the reduction of the superexchange interactions. Further, the magnetic softening of the hexaferrite and the significant reduction in magnetocrystalline anisotropy with Cu substitution was consistent with the ionic distribution in the lattice. This study clearly demonstrated the feasibility of using a simple method to fabricate hexaferrites with a modified coercivity, while maintain the saturation magnetization high enough for practical applications.

  2. Effect of Coercive Voltage and Charge Injection on Performance of a Ferroelectric-Gate Thin-Film Transistor

    Directory of Open Access Journals (Sweden)

    P. T. Tue

    2013-01-01

    Full Text Available We adopted a lanthanum oxide capping layer between semiconducting channel and insulator layers for fabrication of a ferroelectric-gate thin-film transistor memory (FGT which uses solution-processed indium-tin-oxide (ITO and lead-zirconium-titanate (PZT film as a channel layer and a gate insulator, respectively. Good transistor characteristics such as a high “on/off” current ratio, high channel mobility, and a large memory window of 108, 15.0 cm2 V−1 s−1, and 3.5 V were obtained, respectively. Further, a correlation between effective coercive voltage, charge injection effect, and FGT’s memory window was investigated. It is found that the charge injection from the channel to the insulator layer, which occurs at a high electric field, dramatically influences the memory window. The memory window’s enhancement can be explained by a dual effect of the capping layer: (1 a reduction of the charge injection and (2 an increase of effective coercive voltage dropped on the insulator.

  3. Enhancing Tax Compliance through Coercive and Legitimate Power of Tax Authorities by Concurrently Diminishing or Facilitating Trust in Tax Authorities

    Science.gov (United States)

    Hofmann, Eva; Gangl, Katharina; Kirchler, Erich; Stark, Jennifer

    2014-01-01

    Both coercion, such as strict auditing and the use of fines, and legitimate procedures, such as assistance by tax authorities, are often discussed as means of enhancing tax compliance. However, the psychological mechanisms that determine the effectiveness of each strategy are not clear. Although highly relevant, there is rare empirical literature examining the effects of both strategies applied in combination. It is assumed that coercion decreases implicit trust in tax authorities, leading to the perception of a hostile antagonistic tax climate and enforced tax compliance. Conversely, it is suggested that legitimate power increases reason-based trust in the tax authorities, leading to the perception of a service climate and eventually to voluntary cooperation. The combination of both strategies is assumed to cause greater levels of intended compliance than each strategy alone. We conducted two experimental studies with convenience samples of 261 taxpayers overall. The studies describe tax authorities as having low or high coercive power (e.g., imposing lenient or severe sanctions) and/or low or high legitimate power (e.g., having nontransparent or transparent procedures). Data analyses provide supportive evidence for the assumptions regarding the impact on intended tax compliance. Coercive power did not reduce implicit trust in tax authorities; however, it had an effect on reason-based trust, interaction climate, and intended tax compliance if applied solely. When wielded in combination with legitimate power, it had no effect. PMID:26074656

  4. Enhancing Tax Compliance through Coercive and Legitimate Power of Tax Authorities by Concurrently Diminishing or Facilitating Trust in Tax Authorities.

    Science.gov (United States)

    Hofmann, Eva; Gangl, Katharina; Kirchler, Erich; Stark, Jennifer

    2014-07-01

    Both coercion, such as strict auditing and the use of fines, and legitimate procedures, such as assistance by tax authorities, are often discussed as means of enhancing tax compliance. However, the psychological mechanisms that determine the effectiveness of each strategy are not clear. Although highly relevant, there is rare empirical literature examining the effects of both strategies applied in combination. It is assumed that coercion decreases implicit trust in tax authorities, leading to the perception of a hostile antagonistic tax climate and enforced tax compliance. Conversely, it is suggested that legitimate power increases reason-based trust in the tax authorities, leading to the perception of a service climate and eventually to voluntary cooperation. The combination of both strategies is assumed to cause greater levels of intended compliance than each strategy alone. We conducted two experimental studies with convenience samples of 261 taxpayers overall. The studies describe tax authorities as having low or high coercive power (e.g., imposing lenient or severe sanctions) and/or low or high legitimate power (e.g., having nontransparent or transparent procedures). Data analyses provide supportive evidence for the assumptions regarding the impact on intended tax compliance. Coercive power did not reduce implicit trust in tax authorities; however, it had an effect on reason-based trust, interaction climate, and intended tax compliance if applied solely. When wielded in combination with legitimate power, it had no effect.

  5. High field magnetic behavior in Boron doped Fe{sub 2}VAl Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Venkatesh, Ch., E-mail: venkyphysicsiitm@gmail.com [Department of Physics, Indian Institute of Technology, Kharagpur (India); DCMP & MS, Tata Institute of Fundamental Research, Mumbai (India); Vasundhara, M., E-mail: vasu.mutta@gmail.com [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology, CSIR, Trivandrum 695019 (India); Srinivas, V. [Department of Physics, Indian Institute of Technology, Chennai (India); Rao, V.V. [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur (India)

    2016-11-15

    We have investigated the magnetic behavior of Fe{sub 2}VAl{sub 1−x}B{sub x} (x=0, 0.03, 0.06 and 0.1) alloys under high temperature and high magnetic field conditions separately. Although, the low temperature DC magnetization data for the alloys above x>0 show clear magnetic transitions, the zero field cooled (ZFC) and field cooled (FC) curves indicate the presence of spin cluster like features. Further, critical exponent (γ) deduced from the initial susceptibility above the T{sub c}, does not agree with standard models derived for 3 dimensional long range magnetic systems. The deviation in γ values are consistent with the short range magnetic nature of these alloys. We further extend the analysis of magnetic behavior by carrying the magnetization measurements at high temperatures and high magnetic fields distinctly. We mainly emphasize the following observations; (i) The magnetic hysteresis loops show sharp upturns at lower fields even at 900 K for all the alloys. (ii) High temperature inverse susceptibility do not overlap until T=900 K, indicating the persistent short range magnetic correlations even at high temperatures. (iii) The Arrott's plot of magnetization data shows spontaneous moment (M{sub S}) for the x=0 alloy at higher magnetic fields which is absent at lower fields (<50 kOe), while the Boron doped samples show feeble M{sub S} at lower fields. The origin of this short range correlation is due to presence of dilute magnetic heterogeneous phases which are not detected from the X-ray diffraction method. - Highlights: • Short range magnetic character has been confirmed by the critical exponents analysis. • Magnetoresistace is about −14% with non-saturating tendency even at 150 kOe for Fe{sub 2}VAl alloy. • Boron doped Fe{sub 2}VAl alloys show a weak magnetism even at T=900 K.

  6. Electric and magnetic field measurements in a high voltage center.

    Science.gov (United States)

    Safigianni, Anastasia S; Spyridopoulos, Anastasios I; Kanas, Vasilis L

    2012-01-01

    This paper investigates the electric and magnetic fields inside a large high voltage center constituted both of 400/150 and 150/20 kV substation areas. Results of previous field measurements and calculations in substations, made by the authors of this paper or other researchers, are presented first. The basic data distinguishing the examined center from previously examined substations follow. The main results of the field measurements in the areas of the above-mentioned center are presented in relevant diagrams. General conclusions arising from the comparison of the measured field values with relevant reference levels in force for safe public and occupational exposure as well as with the results of previous research are finally given.

  7. Nonlinear Magnetic Phenomena in Highly Polarized Target Materials

    CERN Document Server

    Kiselev, Yu F

    2007-01-01

    The report introduces and surveys nonlinear magnetic phenomena which have been observed at high nuclear polarizations in polarized targets of the SMC and of the COMPASS collaborations at CERN. Some of these phenomena, namely the frequency modulation eect and the distortion of the NMR line shape, promote the development of the polarized target technique. Others, as the spin-spin cross-relaxation between spin subsystems can be used for the development of quantum statistical physics. New findings bear on an electromagnetic noise and the spectrally resolved radiation from LiD with negatively polarized nuclei detected by low temperature bolometers. These nonlinear phenomena need to be taken into account for achieving the ultimate polarizations.

  8. "He Could Scare Me Without Laying a Hand on Me": Mothers' Experiences of Nonviolent Coercive Control During Marriage and After Separation.

    Science.gov (United States)

    Crossman, Kimberly A; Hardesty, Jennifer L; Raffaelli, Marcela

    2016-03-01

    Studies demonstrate the negative effects of violent coercive control but few examine coercive control without violence. This study describes the characteristics of nonviolent coercive control among 8 divorcing mothers and compares them with 47 mothers who experienced violent coercive control or no violence/no control. Mothers with nonviolent coercive control reported more coping strategies, risk, harassment, and perceived threat than mothers with no violence/no control; similar levels of fear and control during marriage as mothers with violent coercive control; and more postseparation fear than both groups. Findings highlight the need to include nonviolent coercive control in screening methods and research measures. © The Author(s) 2015.

  9. High-induction nanocrystalline soft magnetic Fe{sub X}Ti{sub Y}B{sub Z} films prepared by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Sheftel, Elena N.; Tedzhetov, Valentin A.; Harin, Eugene V.; Usmanova, Galina Sh. [A.A. Baikov Institute of Metallurgy and Material Science, Russian Academy of Sciences, Moscow (Russian Federation); Kiryukhantsev-Korneev, Filipp V. [National University of Science and Technology ' ' MISIS' ' , Moscow (Russian Federation)

    2016-12-15

    To design films with the Fe/TiB{sub 2} nanocomposite structure, which are characterized by high saturation induction B{sub s}, the phase and structural states and static magnetic properties of Fe-TiB{sub 2} films prepared by magnetron sputtering and subjected to subsequent annealing have been studied. According to X-ray diffraction data, either amorphous or nanocrystalline single-phase structure (an α-Fe(Ti,B) supersaturated solid solution with a bcc crystal lattice) is formed in the as-sputtered films. Depending on the film composition, the grain size of the α-Fe(Ti,B) phase varies from 45.6 to 6.5 nm; grains are characterized by high microstrain (0.21-4.96%). The annealing at 200-500 C leads to a decrease in the lattice parameter of the α-Fe(Ti,B) phase, i.e. to its depletion of titanium and boron and to the formation of two-phase α-Fe + Fe{sub 3}B structure after annealing at 500 C. The annealing at 200-500 C almost does not affect the grain size and microstrain of the bcc α-Fe-based phase. The amorphous state of the films is stable up to 500 C. All studied films are ferromagnets; the saturation induction B{sub s}(0.95-2.13 T) and coercive field H{sub c} (0.4-5 kA/m) of the films were determined. Correlations between the B{sub s} and H{sub c} magnitudes and the chemical composition of the films, their phase and structural states and magnetic structure are discussed. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Extraordinary Hall-effect in colloidal magnetic nanoparticle films

    Energy Technology Data Exchange (ETDEWEB)

    Ben Gur, Leah; Tirosh, Einat [School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801 (Israel); Segal, Amir [School of Physics, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801 (Israel); Markovich, Gil, E-mail: gilmar@post.tau.ac.il [School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801 (Israel); Gerber, Alexander, E-mail: gerber@post.tau.ac.il [School of Physics, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801 (Israel)

    2017-03-15

    Colloidal nickel nanoparticles (NPs) coated with polyvinylpyrrolidone (PVP) were synthesized. The nanoparticle dispersions were deposited on substrates and dried under mild heating to form conductive films. The films exhibited very small coercivity, nearly metallic conductivity, and a significant extraordinary Hall effect signal. This method could be useful for preparing simple, printed magnetic field sensors with the advantage of relatively high sensitivity around zero magnetic field, in contrast to magnetoresistive sensors, which have maximal field sensitivity away from zero magnetic field. - Highlights: • Ni nanoparticle ink capable of forming conductive films on drying. • The Ni nanoparticle films exhibit significant extraordinary Hall effect. • This system could be used for preparing printed magnetic field sensors integrated in 3D printed structures.

  11. Magnonic holographic imaging of magnetic microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, D.; Chiang, H.; Bhowmick, T.; Volodchenkov, A.D.; Ranjbar, M.; Liu, G.; Jiang, C.; Warren, C. [Department of Electrical and Computer Engineering, University of California - Riverside, Riverside, CA 92521 (United States); Khivintsev, Y.; Filimonov, Y. [Kotelnikov Institute of Radioengineering and Electronics of Russian Academy of Sciences, Saratov Branch, Saratov 410019 (Russian Federation); Saratov State University, Saratov 410012 (Russian Federation); Garay, J.; Lake, R.; Balandin, A.A. [Department of Electrical and Computer Engineering, University of California - Riverside, Riverside, CA 92521 (United States); Khitun, A., E-mail: akhitun@engr.ucr.edu [Department of Electrical and Computer Engineering, University of California - Riverside, Riverside, CA 92521 (United States)

    2017-04-15

    We propose and demonstrate a technique for magnetic microstructure imaging via their interaction with propagating spin waves. In this approach, the object of interest is placed on top of a magnetic testbed made of material with low spin wave damping. There are micro-antennas incorporated in the testbed. Two of these antennas are used for spin wave excitation while another one is used for the detecting of inductive voltage produced by the interfering spin waves. The measurements are repeated for different phase differences between the spin wave generating antennas which is equivalent to changing the angle of illumination. The collected data appear as a 3D plot – the holographic image of the object. We present experimental data showing magnonic holographic images of a low-coercivity Si/Co sample, a high-coercivity sample made of SrFe{sub 12}O{sub 19} and a diamagnetic copper sample. We also present images of the three samples consisting of a different amount of SrFe{sub 12}O{sub 19} powder. The imaging was accomplished on a Y{sub 3}Fe{sub 2}(FeO{sub 4}){sub 3} testbed at room temperature. The obtained data reveal the unique magnonic signatures of the objects. Experimental data is complemented by the results of numerical modeling, which qualitatively explain the characteristic features of the images. Potentially, magnonic holographic imaging may complement existing techniques and be utilized for non-destructive in-situ magnetic object characterization. The fundamental physical limits of this approach are also discussed. - Highlights: • A technique for magnetic microstructure imaging via their interaction with propagating spin waves is proposed. • In this technique, magnetic structures appear as 3D objects. • Several holographic images of magnetic microstructures are presented.

  12. High-density all-optical magnetic recording using a high-NA lens illuminated by circularly polarized pulse lights

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yaoju [College of Physics and Electronic Information, Wenzhou University, Wenzhou 325035 (China)], E-mail: zhangyaoju@sohu.com; Bai Jianping [School of Physics and Electronic Engineering, Nanyang Normal College, Nanyang 472000 (China)

    2008-10-06

    We propose a method for high-density all-optical magnetic recording. Our analyses, based on the vector diffraction theory, show that owing to the inverse Faraday effect, circularly polarized laser pulses focused by a high numerical aperture (NA) lens can induce a small magnetization domain. For an example, the FWHM of the effective magnetization domain is 0.4646{lambda} when NA=0.85. The magnetization direction is basically perpendicular to the surface of the optic-magneto film within the effective magnetization domain and the switching direction of magnetization can be controlled by the helicity of the incident circularly polarized light. These characteristics are useful to next-generation high-density all-optical magnetic storage.

  13. Numerical study of magnetic nanoparticles concentration in biofluid (blood) under influence of high gradient magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Reza Habibi, Mohammad, E-mail: mohammad_habibi_4@yahoo.co [Mechanical Engineering Department, K.N.Toosi University of Technology, P.O. Box 19395-1999, Tehran (Iran, Islamic Republic of); Ghasemi, Majid [Mechanical Engineering Department, K.N.Toosi University of Technology, P.O. Box 19395-1999, Tehran (Iran, Islamic Republic of)

    2011-01-15

    Ferrofluids are widely used in pharmaceutical industries as magnetic separation tools, anti-cancer drug carriers and micro-valve applications. The purpose of the current study is to investigate the effect of a magnetic field on the volume concentration of magnetic nanoparticles of a non-Newtonian biofluid (blood) as a drug carrier. The effect of particles on the flow field is considered. The governing non-linear differential equations, concentration and Naviar-stokes are coupled with the magnetic field. To solve these equations, a finite volume based code is developed and utilized. The results show accumulation of magnetic nanoparticles near the magnetic source until it looks like a solid object. The accumulation of nanoparticles is due to the magnetic force that overcomes the fluid drag force. As the magnetic strength and size of the magnetic particles increase, the accumulation of nanoparticles increases, as well. The magnetic susceptibility of particles also affects the flow field and the contour of the concentration considerably.

  14. Effect of Crystallographic Texture on Magnetic Characteristics of Cobalt Nanowires

    Directory of Open Access Journals (Sweden)

    Usman M

    2010-01-01

    Full Text Available Abstract Cobalt nanowires with controlled diameters have been synthesized using electrochemical deposition in etched ion-track polycarbonate membranes. Structural characterization of these nanowires with diameter 70, 90, 120 nm and length 30 μm was performed by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction techniques. The as-prepared wires show uniform diameter along the whole length and X-ray diffraction analysis reveals that [002] texture of these wires become more pronounced as diameter is reduced. Magnetic characterization of the nanowires shows a clear difference of squareness and coercivity between parallel and perpendicular orientations of the wires with respect to the applied field direction. In case of parallel applied field, the coercivity has been found to be decreasing with increasing diameter of the wires while in perpendicular case; the coercivity observes lower values for larger diameter. The results are explained by taking into account the magnetocrystalline and shape anisotropies with respect to the applied field and domain transformation mechanism when single domain limit is surpassed.

  15. In-situ magnetic property measurement of the RPV steel under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ebine, N.; Suzuki, M. [Japan Atomic Research Energy Inst. (Japan); Kikuchi, H.; Kamada, Y.; Ara, K.; Takahashi, S. [NDE and S-RC, Faculty of Engineering, Iwate Univ. (Japan)

    2004-07-01

    Magnetic properties of a RPV steel were successfully measured in-situ under neutron irradiation. Coercivity and Hysteresis loss increased with neutron fluence and showed a peak at the fluence of about 3 x 10{sup 19} n/cm{sup 2}, and the maximum increase of coercivity was 1.25%. The reason of showing a peak is not known. (orig.)

  16. High-gradient magnetic separation using ferromagnetic membrane

    Energy Technology Data Exchange (ETDEWEB)

    Podoynitsyn, Sergey N., E-mail: spod@sky.chph.ras.ru; Sorokina, Olga N., E-mail: alsiona@gmail.com; Kovarski, Alexander L., E-mail: alkogon383@yandex.ru

    2016-01-01

    The magnetic separator with the membrane separating unit made of laser-perforated thick ferromagnetic foil was tested using composite water suspension of magnetic nanoparticles adsorbed on hydroxylapatite microparticles. The average sizes of the particles in the suspension and the magnetic moment of the suspension were measured by dynamic light scattering and electron magnetic resonance correspondingly to evaluate the efficiency of the separation. It was shown experimentally that the separation is effected by the membrane type and the flow rate. Magnetic coarse grains (larger than 1 μm) were captured by the membrane preferably and the magnetic moment of the suspension decreased by 20–25% after the separation. The magnetic field simulation and experimental results demonstrate the higher separation efficiency for thicker membranes. - Highlights: • A new design of magnetic separator with ferromagnetic membrane was developed. • Coarse magnetic particles 1 μm in size are captured by the membrane preferably. • Selectivity of magnetic separation improves with flow rate decrease. • Separation efficiency of thick ferromagnetic membrane is higher than of the thin one.

  17. Extreme sensitivity of magnetic properties on the synthesis routes in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ashutosh, E-mail: ashutosh.pph13@iitp.ac.in [Department of Physics, Indian Institute of Technology Patna, Patna-801 118 (India); Sharma, Himanshu; Tomy, C. V. [Department of Physics, Indian Institute of Technology Bombay, Mumbai-400 076 (India); Thakur, Ajay D. [Department of Physics, Indian Institute of Technology Patna, Patna-801 118 (India); Centre for Energy and Environment, Indian Institute of Technology Patna, Patna-801 118 (India)

    2016-05-06

    La{sub 0.7}Sr{sub 0.3}MnO{sub 3} polycrystalline samples have been prepared using different synthesis routes. X-ray Diffraction (XRD) confirms that the samples are of single phase with R-3c space group. The surface morphology and particle size has been observed using Field Emission Scanning Electron Microscopy (FESEM). Magnetic measurement shows that the magnetization in the materials are affected by low crystallite size which destroys the spin ordering due to strain at grain boundaries and this also leads to reduction in magnetization as well as high coercivity in the material.

  18. Rational synthesis of zerovalent iron/bamboo charcoal composites with high saturation magnetization

    Science.gov (United States)

    Mingshan Wu; Jianfeng Ma; Zhiyong Cai; Genlin Tian; Shumin Yang; Youhong Wang; Xing' e Liu

    2015-01-01

    The synthesis of magnetic biochar composites is a major new research area in advanced materials sciences. A series of magnetic bamboo charcoal composites (MBC800, MBC1000 and MBC1200) with high saturation magnetization (Ms) was fabricated in this work by mixing bamboo charcoal powder with an aqueous ferric chloride solution and subsequently...

  19. High resolution three-dimensional magnetization mapping in Tokachidake Volcano using low altitude airborne magnetic survey data

    Science.gov (United States)

    Iwata, M.; Mogi, T.; Okuma, S.; Nakatsuka, T.

    2016-12-01

    Tokachidake Volcano, central Hokkaido, Japan erupted in 1926, 1962 and 1988-1989 in the 20th century from the central part. In recent years, expansions of the edifice of the volcano at shallow depth and increases of the volcanic smoke in the Taisho crater were observed (Meteorological Agency of Japan, 2014). Magnetic changes were observed at the 62-2 crater by repeated magnetic measurements in 2008-2009, implying a demagnetization beneath the crater (Hashimoto at al., 2010). Moreover, a very low resistivity part was found right under the 62-2 crater from an AMT survey (Yamaya et al., 2010). However, since the station numbers of the survey are limited, the area coverage is not sufficient. In this study, we have re-analyzed high-resolution aeromagnetic data to delineate the three-dimensional magnetic structure of the volcano to understand the nature of other craters.A low altitude airborne magnetic survey was conducted in 2014 mainly over the active areas of the volcano by the Ministry of Land, Infrastructure, Transport and Tourism to manage land slide risk in the volcano. The survey was flown at an altitude of 60 m above ground by a helicopter with a Cesium magnetometer in the towed-bird 30m below the helicopter. The low altitude survey enables us to delineate the detailed magnetic structure. We calculated magnetic anomaly distribution on a smooth surface assuming equivalent anomalies below the observation surface. Then the 3D magnetic imaging method (Nakatsuka and Okuma, 2014) was applied to the magnetic anomalies to reveal the three-dimensional magnetic structure.As a result, magnetization highs were seen beneath the Ground crater, Suribachi crater and Kitamuki crater. This implies that magmatic activity occurred in the past at these craters. These magma should have already solidified and acquired strong remanent magnetization. Relative magnetization lows were seen beneath the 62-2 crater and the Taisho crater where fumarolic activity is active. However a

  20. Size and shape dependence study of magnetization reversal in magnetic antidot lattice arrays

    Energy Technology Data Exchange (ETDEWEB)

    Mallick, Sougata; Bedanta, Subhankar, E-mail: sbedanta@niser.ac.in

    2015-05-15

    Magnetic Antidot Lattice (MAL) arrays of Co have been prepared in micron range using ultraviolet (UV) lithography technique with different shapes and sizes. Magnetization reversal in such MAL systems has been studied by magneto-optic Kerr effect (MOKE) based microscopy by varying the angle between the easy axis and the external magnetic field. The domain images evidence that the magnetization reversal along easy axis is highly dominated by nucleation of domains which is subsequently accompanied by domain wall motion. We have observed that with increase in active magnetic area domain size increases but on the contrary coercivity decreases. The presence of periodic holes turns the MALs magnetically hard when compared to similar thickness of continuous thin film. The magnetization relaxation along easy axis for the Co MAL at constant dc field fits very well with the exponential law of Fatuzzo–Labrune indicating domain nucleated dominant process. - Highlights: • The periodic holes act as pinning center and make the domains to follow a zigzag path. • Domain size for different magnetic antidot lattice arrays (MALs) has been studied. • The relaxation behavior of MALs under constant magnetic field has been studied.

  1. Conceptual design of a compact high gradient quadrupole magnet of varying strength using permanent magnets

    Directory of Open Access Journals (Sweden)

    Gautam Sinha

    2018-02-01

    Full Text Available A concept is presented to design magnets using cylindrical-shaped permanent-magnet blocks, where various types of magnetic fields can be produced by either rotating or varying the size of the magnetic blocks within a given mechanical structure. A general method is introduced to calculate the 3D magnetic field produced by a set of permanent magnets. An analytical expression of the 2D field and the condition to generate various magnetic fields like dipole, quadrupole, and sextupole are derived. Using the 2D result as a starting point, a computer code is developed to get the optimum orientation of the magnets to obtain the user-specific target field profile over a given volume in 3D. Designs of two quadrupole magnets are presented, one using 12 and the other using 24 permanent-magnet blocks. Variation of the quadrupole strength is achieved using tuning coils of a suitable current density and specially designed end tubes. A new concept is introduced to reduce the integrated quadrupole field strength by inserting two hollow cylindrical tubes made of iron, one at each end. This will not affect the field gradient at the center but reduce the integrated field strength by shielding the magnetic field near the ends where the tubes are inserted. The advantages of this scheme are that it is easy to implement, the magnetic axis will not shift, and it will prevent interference with nearby devices. Around 40% integrated field variation is achieved using this method in the present example. To get a realistic estimation of the field quality, a complete 3D model using a nonlinear B-H curve is also studied using a finite-element-based computer code. An example to generate around an 80  T/m quadrupole field gradient is also presented.

  2. RAPID COMMUNICATION: High performance superconducting wire in high applied magnetic fields via nanoscale defect engineering

    Science.gov (United States)

    Wee, Sung Hun; Goyal, Amit; Zuev, Yuri L.; Cantoni, Claudia

    2008-09-01

    High temperature superconducting (HTS) wires capable of carrying large critical currents with low dissipation levels in high applied magnetic fields are needed for a wide range of applications. In particular, for electric power applications involving rotating machinery, such as large-scale motors and generators, a high critical current, Ic, and a high engineering critical current density, JE, in applied magnetic fields in the range of 3-5 Tesla (T) at 65 K are required. In addition, exceeding the minimum performance requirements needed for these applications results in a lower fabrication cost, which is regarded as crucial to realize or enable many large-scale bulk applications of HTS materials. Here we report the fabrication of short segments of a potential superconducting wire comprised of a 4 µm thick YBa2Cu3O7-δ (YBCO) layer on a biaxially textured substrate with a 50% higher Ic and JE than the highest values reported previously. The YBCO film contained columns of self-assembled nanodots of BaZrO3 (BZO) roughly oriented along the c-axis of YBCO. Although the YBCO film was grown at a high deposition rate, three-dimensional self-assembly of the insulating BZO nanodots still occurred. For all magnetic field orientations, minimum Ic and JE at 65 K, 3 T for the wire were 353 A cm-1 and 65.4 kA cm-2, respectively.

  3. Controlling interactions between highly magnetic atoms with Feshbach resonances.

    Science.gov (United States)

    Kotochigova, Svetlana

    2014-09-01

    This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.

  4. Creating social policy to support women's agency in coercive settings: A case study from Uganda.

    Science.gov (United States)

    Burgess, Rochelle; Campbell, Catherine

    2016-01-01

    Many emphasise the need for policies that support women's agency in highly coercive settings, and the importance of involving target women in public deliberation to inform policy design. The Ugandan Marriage and Divorce Bill seeks to strengthen women's agency in marriage, but has faced many obstacles, including objections from many women themselves in public consultations. We explore key stakeholders' accounts of the difficulties facing the Bill's progress to date, through focus groups with 24 rural and urban men and women, interviews with 14 gender champions in government, non-governmental organisations and legal sectors, and 25 relevant media and radio reports. Thematic analysis revealed an array of representations of the way the Bill's progress was shaped by the public consultation process, the nature of the Ugandan public sphere, the understanding and manipulation of concepts such as 'culture' and 'custom' in public discourse, the impact of economic inequalities on women's understandings of their gendered interests and low women's trust in the law and the political process. We discuss the complexities of involving highly marginalised women in public debates about gender issues and highlight possible implications for conceptualising agency, gender and social change as tools for gender policy and activism in extreme inequality.

  5. Effects of the Ti/Fe ratio on the phase composition and magnetic properties of mechanochemically activated Ti-Fe{sub 2}O{sub 3} mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Cristobal, A.A. [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales (INTEMA), CONICET-UNMdP, Av. J.B. Justo 4302 - B7608FDQ - Mar del Plata (Argentina); Ramos, C.P. [CONICET and Centro Atomico Constituyentes (CAC), CNEA, Av. Gral. Paz 1499 (1650), San Martin (Argentina); Bercoff, P.G. [Facultad de Matematica, Astronomia y Fisica (FaMAF), Universidad Nacional de Cordoba, IFEG (CONICET), Medina Allende s/n, Ciudad Universitaria, 5000 Cordoba (Argentina); Botta, P.M., E-mail: pbotta@fi.mdp.edu.ar [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales (INTEMA), CONICET-UNMdP, Av. J.B. Justo 4302 - B7608FDQ - Mar del Plata (Argentina); Lopez, J.M. Porto [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales (INTEMA), CONICET-UNMdP, Av. J.B. Justo 4302 - B7608FDQ - Mar del Plata (Argentina)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Mechanochemical treatment of Ti/Fe{sub 2}O{sub 3} powders induces fast redox reactions at RT. Black-Right-Pointing-Pointer Composite materials Fe/TiO{sub 2} or Fe/FeTiO{sub 3} are formed according to starting Ti/Fe ratio. Black-Right-Pointing-Pointer These materials show high saturation magnetization and a relatively high coercivity. Black-Right-Pointing-Pointer Heating favors the formation of FeTiO{sub 3}, decreasing the magnetization and coercivity. - Abstract: The mechanochemical activation of Ti/Fe{sub 2}O{sub 3} powder mixtures with molar ratio 1 and 1.5 was performed with the aim of understanding the effects of the starting composition on the reactivity and structure of the produced phases. The solid mixture was characterized by scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry and Moessbauer spectroscopy. The consumption of the reactants and the formation of metallic iron are observed at short activation times. After 3 h, the redox reaction completes, yielding a composite powder formed by nanocrystalline Fe particles dispersed in an oxide matrix. The mixture with the highest Ti/Fe ratio leads to the formation of a TiO{sub 2} matrix, whereas the other composition forms FeTiO{sub 3}. Both composite materials have very high saturation magnetization and moderate coercivities. Under subsequent thermal treatment at 700 Degree-Sign C, the activated solids show a progressive crystalline ordering with partial oxidation of Fe (mainly to FeTiO{sub 3} and Fe{sub 2}O{sub 3}) and crystallization into the rutile phase of TiO{sub 2}. This leads to a significant decrease of magnetization and coercivity.

  6. High frequency electromagnetic interference shielding magnetic polymer nanocomposites

    Science.gov (United States)

    He, Qingliang

    Electromagnetic interference is one of the most concerned pollution and problem right now since more and more electronic devices have been extensively utilized in our daily lives. Besides the interference, long time exposure to electromagnetic radiation may also result in severe damage to human body. In order to mitigate the undesirable part of the electromagnetic wave energy and maintain the long term sustainable development of our modern civilized society, new technology development based researches have been made to solve this problem. However, one of the major challenges facing to the electromagnetic interference shielding is the relatively low shielding efficiency and the high cost as well as the complicated shielding material manufacture. From the materials science point of view, the key solutions to these challenges are strongly depended on the breakthrough of the current limit of shielding material design and manufacture (such as hierarchical material design with controllable and predictable arrangement in nanoscale particle configuration via an easy in-situ manner). From the chemical engineering point of view, the upgrading of advanced material shielding performance and the enlarged production scale for shielding materials (for example, configure the effective components in the shielding material in order to lower their usage, eliminate the "rate-limiting" step to enlarge the production scale) are of great importance. In this dissertation, the design and preparation of morphology controlled magnetic nanoparticles and their reinforced polypropylene polymer nanocomposites will be covered first. Then, the functionalities of these polymer nanocomposites will be demonstrated. Based on the innovative materials design and synergistic effect on the performance advancement, the magnetic polypropylene polymer nanocomposites with desired multifunctionalities are designed and produced targeting to the electromagnetic interference shielding application. In addition

  7. Temperature dependence of the coercive field of gas atomized Fe{sub 73.5}Si{sub 13.5}B{sub 9}Nb{sub 3}Cu{sub 1}

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Escorial, A., E-mail: age@cenim.csic.es [CENIM-CSIC, Avda, Gregorio del Amo, 8, 28040 Madrid (Spain); Lieblich, M. [CENIM-CSIC, Avda, Gregorio del Amo, 8, 28040 Madrid (Spain); Hernando, A.; Aragon, A.; Marin, P. [Instituto de Magnetismo Aplicado, IMA, P.O. Box 155, 28230 Madrid (Spain)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer An anomalous thermal dependence of the coercive field of gas atomized Fe{sub 73.5}Si{sub 13.5}B{sub 9}Nb{sub 3}Cu{sub 1} powder particles under 25 {mu}m powder particle, increasing Hc as temperature increases. Black-Right-Pointing-Pointer It is proposed that Cu rich regions at inter-grain boundaries could act as exchange decoupling regions contributing to the thermal increase of coercivity. Black-Right-Pointing-Pointer This anomalous thermal dependence points out that tailoring microstructure and size, by controlling the cooling rate of more adequate multiphase systems, could be a promising procedure to develop soft or hard magnets, avoiding Rare Earths metals that is nowadays an important target for the engineering of magnetic materials. - Abstract: In this work, the dependence of the coercive field of Fe{sub 73.5}Si{sub 13.5}B{sub 9}Nb{sub 3}Cu{sub 1} gas atomized powder with the temperature for different particle sizes has been studied, observing an anomalous behavior in the under 25 powder particle size fraction. This unusual behavior is related with the microstructure of the powder, and is attributed to the presence of a multiphase magnetic system, with non-magnetic regions decoupling the ferromagnetic domains.

  8. Simplified Magnetically Shielded Cylinder Using Flexible Magnetic Sheets for High-Tc Superconducting Quantum Interference Device Magnetocardiogram Systems

    Science.gov (United States)

    Suzuki, Daisuke; Yokosawa, Koichi; Miyashita, Tsuyoshi; Kandori, Akihiko; Tsukada, Keiji; Tsukamoto, Akira; Arakawa, Shunsuke

    2001-10-01

    A small and simple magnetic-shielding cylinder using a new high-permeability sheet, developed for magnetic shielding, can reduce the amount of effort expended on taking magnetocardiogram (MCG) measurements. This sheet is made of a nanocrystalline soft-magnetic material (an Fe-Cu-Nb-Si-B alloy) and is flexible and easy to handle. Moreover, magnetostriction of the material is nearly zero, unlike that of the materials used in conventional magnetic shielding. The shielding cylinder is made up of three tubes of various diameters (but having the same length), placed one inside the other. The shielding cylinder is 1.0 m in diameter and 2.0 m long, and it has a shielding factor of about 35 dB at 1 Hz. The shielding cylinder was tested by measuring MCGs using a high-Tc superconducting quantum interference device (SQUID) gradiometer.

  9. Development of High-frequency Soft Magnetic Materials for Power Electronics

    Directory of Open Access Journals (Sweden)

    LIU Jun-chang

    2017-05-01

    Full Text Available The new requirements of high-frequency magnetic properties are put forward for electronic components with the rapid development of power electronics industry and the use of new electromagnetic materials. The properties of magnetic core, which is the key unit of electronic components, determine the performance of electronic components directly. Therefore, it's necessary to study the high-frequency soft magnetic materials. In this paper, the development history of four types of soft magnetic materials was reviewed. The advantages and disadvantages of each kind of soft magnetic materials and future development trends were pointed out. The emphases were placed on the popular soft magnetic composite materials in recent years. The tendency is to develop high-frequency soft magnetic composite materials with the particle size controllable, uniform coating layer on the core and a mass production method from laboratory to industrialization.

  10. 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.

  11. Variables Associated with the Use of Coercive Measures on Psychiatric Patients in Spanish Penitentiary Centers

    Directory of Open Access Journals (Sweden)

    E. Girela

    2014-01-01

    Full Text Available We have studied the use of coercive medical measures (forced medication, isolation, and mechanical restraint in mentally ill inmates within two secure psychiatric hospitals (SPH and three regular prisons (RP in Spain. Variables related to adopted coercive measures were analyzed, such as type of measure, causes of indication, opinion of patient inmate, opinion of medical staff, and more frequent morbidity. A total of 209 patients (108 from SPH and 101 from RP were studied. Isolation (41.35% was the most frequent coercive measure, followed by mechanical restraint (33.17% and forced medication (25.48%. The type of center has some influence; specifically in RP there is less risk of isolation and restraint than in SPH. Not having had any previous imprisonment reduces isolation and restraint risk while increases the risk of forced medication, as well as previous admissions to psychiatric inpatient units does. Finally, the fact of having lived with a partner before imprisonment reduces the risk of forced medication and communication with the family decreases the risk of isolation. Patients subjected to a coercive measure exhibited a pronounced psychopathology and most of them had been subjected to such measures on previous occasions. The mere fact of external assessment of compliance with human rights slows down the incidence of coercive measures.

  12. CaO-matrix processing of MnBi alloys for permanent magnets

    Directory of Open Access Journals (Sweden)

    A. M. Gabay

    2017-05-01

    Full Text Available The possibility to suppress agglomeration of MnBi alloy particles during milling and their unwanted sintering during subsequent annealing was explored by embedding the particles in CaO through co-milling. A 15 h annealing of the micron-sized MnBi particles embedded in the CaO matrix at 300 °C is not accompanied by sintering or growth of the particles while it significantly increases their coercivity – presumably by healing the milling-induced crystal defects. After separation from the CaO matrix, the annealed MnBi powder combines a calculated energy product of 10 MGOe with a room-temperature coercivity of 14.4 kOe. At the same time, the partial loss and degradation of the MnBi low-temperature phase during warm compaction of the powders makes the effect of the CaO-matrix annealing less pronounced in the case of fully dense magnets; the residue from the solvents employed for the removal of the CaO might have contributed to the decline of the properties. Still, a relatively high room-temperature coercivity of 8.5 kOe was obtained for the fuslly-dense MnBi magnet exhibiting an energy product of 5.3 MGOe.

  13. Design of microchannels for cryostabilization of high temperature superconducting magnets

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Y.S.; Hull, J.R.; Niemann, R.C.

    1993-10-01

    Microchannel cooling using subcooled liquid nitrogen is proposed to cryogenically stabilize high-temperature superconducting magnets. Various design constraints and parameters are identified and summarized. A graphical method is proposed for the design of microchannel systems. This graphical method helps to reduce the amount of work towards achieving optimum design for a specific application because there are a large number of parameters involved in the design of a microchannel system. The proposed graphical method are illustrated by three examples. The results show that a design window may appear for a given application. Any point within this window is an acceptable design. Another advantage of the graphical method is that, by selecting a design point, the design margin against various design contrains can be easily identified. Any two of the design variables can be selected as the independent variables. The choice depends on specific application and, to a certain extent, on individual preference. The three examples revealed that, for high current density applications, the most scattering constraints are the coolant temperature rise and the fin tip temperatures provided that a moderate pressure drop can be tolerated.

  14. Directed magnetic field induced assembly of high magnetic moment cobalt nanowires

    DEFF Research Database (Denmark)

    Srivastava, Akhilesh Kumar; Madhavi, S.; Ramanujan, R.V.

    2010-01-01

    A directed magnetic field induced assembly technique was employed to align two phase (h.c.p. + f.c.c.) cobalt nanoparticles in a mechanically robust long wire morphology. Co nanoparticles with an average size of 4.3 nm and saturation magnetization comparable to bulk cobalt were synthesized by bor...

  15. Atomic magnetic gradiometer for room temperature high sensitivity magnetic field detection

    Science.gov (United States)

    Xu, Shoujun [Berkeley, CA; Lowery, Thomas L [Belmont, MA; Budker, Dmitry [El Cerrito, CA; Yashchuk, Valeriy V [Richmond, CA; Wemmer, David E [Berkeley, CA; Pines, Alexander [Berkeley, CA

    2009-08-11

    A laser-based atomic magnetometer (LBAM) apparatus measures magnetic fields, comprising: a plurality of polarization detector cells to detect magnetic fields; a laser source optically coupled to the polarization detector cells; and a signal detector that measures the laser source after being coupled to the polarization detector cells, which may be alkali cells. A single polarization cell may be used for nuclear magnetic resonance (NMR) by prepolarizing the nuclear spins of an analyte, encoding spectroscopic and/or spatial information, and detecting NMR signals from the analyte with a laser-based atomic magnetometer to form NMR spectra and/or magnetic resonance images (MRI). There is no need of a magnetic field or cryogenics in the detection step, as it is detected through the LBAM.

  16. Accelerated Testing of High Temperature Permanent Magnets for Spacecraft Propulsion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High temperature permanent magnet materials play an important role in NASA's space missions in electric propulsion, energy generation and storage and other...

  17. Modification of magnetic anisotropy in metallic glasses using high ...

    Indian Academy of Sciences (India)

    Abstract. Heavy ion irradiation in the electronic stopping power region induces macroscopic di- mensional change in metallic glasses and introduces magnetic anisotropy in some magnetic mate- rials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and ...

  18. Development of a high-performance magnetic gear

    DEFF Research Database (Denmark)

    Rasmussen, Peter Omand; Andersen, Torben Ole; Jørgensen, Frank Thorleif

    2005-01-01

    This paper presents calculation and measurement results of a highperformance permanent-magnetic gear. The analyzed permanent-magnetic gear has a gear ratio of 5.5 and is able to deliver 27 N.m. The analysis has shown that special attention needs to be paid to the system where the gear is to be in...

  19. High performance of low cost soft magnetic materials

    Indian Academy of Sciences (India)

    Administrator

    Abstract. The consistent interest in supporting research and development of magnetic materials during the last century is revealed in their steadily increasing market. In this work, the soft magnetic nanocrystalline. FINEMET alloy was prepared with commercial purity raw materials and compared for the first time with the.

  20. High-Field Magnetization of Light Rare-Earth Metals

    DEFF Research Database (Denmark)

    McEwen, K.A.; Cock, G.J.; Roeland, L.W.

    1973-01-01

    The magnetization of single crystals of Eu, Sm, Nd, Pr, and Pr-Nd alloys has been measured in fields up to 37 T (370 kG). The results give new information on the magnetic properties of these metals. Of particular interest is a first-order transition from a nonmagnetic to a metamagnetic phase...

  1. Low core losses and magnetic properties of Fe85-86Si1-2B8P4Cu1 nanocrystalline alloys with high B for power applications (invited)

    Science.gov (United States)

    Makino, Akihiro; Kubota, Takeshi; Yubuta, Kunio; Inoue, Akihisa; Urata, Akiri; Matsumoto, Hiroyuki; Yoshida, Shigeyoshi

    2011-04-01

    Recently, the energy crisis and the continued growth in electrical power generation strongly demand minimization of wasteful energy dissipation. Magnetic core loss (W) is the main source of energy dissipation in motors and transformers. This requires the development of soft magnetic materials with low coercivity (Hc) and high magnetic flux density (B). Fe-rich Fe85-86Si1-2B8P4Cu1 (at. %) alloy ribbons made from industrial raw materials (containing some impurities) with 6 mm in width have a heteroamorphous structure containing a large number of extremely small Fe grains (less than 3 nm), resulting from the unique effects of P and Cu addition in proper amounts. Crystallization of these alloys by annealing shows a uniform precipitation of α-Fe, leading to a uniform nanocrystallized structure of α-Fe grains, 16-19 nm in size, accompanied by an intergranular amorphous layer about 1 nm in width. The wide ribbons exhibit high B of 1.82-1.85 T (at 800 A/m), almost comparable to commercial oriented Fe-3 mass% Si alloys. Excellent magnetic softness (low Hc of 2.6-5.8 A/m, high permeability of 2.4-2.7 × 104 at 1 kHz and small saturation magnetostriction of 2.3-2.4 × 10-6) along with high electrical resistivity (0.67-0.74 μΩ m) of these alloys result in superior frequency characteristics of core losses and a much lower W at 50 Hz up to the maximum induction of 1.75 T, in comparison to the silicon steels now in practical use for power applications.

  2. Aspects of passive magnetic levitation based on high-T(sub c) superconducting YBCO thin films

    Science.gov (United States)

    Schoenhuber, P.; Moon, F. C.

    1995-01-01

    Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here we present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T(sub c) superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, we investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation or - without need of levitation

  3. Cobalt-based Magnetic Nanoparticles: Design, Synthesis and Characterization

    Science.gov (United States)

    Zamanpour, Mehdi

    The ever-increasing desire for more energy attainable from a smaller volume of matter has driven researchers to explore advanced materials at the molecular or even atomic size scale. Magnetic materials at the nanometer size scale have been the subject of enormous research effort worldwide for more than half a century. Different magnetic nanoparticles have shown different behavior in the absence and presence of an external magnetic field, which has led them to be categorized as soft (easy to demagnetize) or hard (resistive against demagnetization) magnets. Applications range from medical and biomedical devices to magnetic recording media and magnetic sensing have emphasized the importance of this class of materials. Soft magnetic phases have found application in power generation and magnetic targeted drug delivery, while hard magnets have been subject of extensive research for application as energy storage media. Discovery of the exchange-coupling phenomenon between the spins of two adjacent hard and soft magnetic phases which means taking advantage of both high magnetic moment of the soft phase as well as high coercivity of the hard phase has attracted scientists to develop advanced materials for energy storage with no usage of fossil fuels: clean energy. In this Dissertation, synthesis of pure phase, soft FeCo nanoparticles with high magnetic moment and hard phase CoxC nanoparticles possessing high coercivity is reported. The polyol method (chemical co-precipitating at polyhydric alcohol as reducing agent) is used to make FeCo and Co xC nanoparticles and the effects of important reaction kinetics parameters on the structure and magnetic properties of the products are studied. Careful analysis of correlations between these parameters and the properties of the magnetic particles has made synthesis of FeCo and CoxC nanoparticles with desired properties possible. Fabrication of MnAlC-FeCo heterostructures as a rare earth-free alternative for high-performance permanent

  4. Magnetic anisotropy of thin sputtered MgB2 films on MgO substrates in high magnetic fields

    Directory of Open Access Journals (Sweden)

    Savio Fabretti

    2014-03-01

    Full Text Available We investigated the magnetic anisotropy ratio of thin sputtered polycrystalline MgB2 films on MgO substrates. Using high magnetic field measurements, we estimated an anisotropy ratio of 1.35 for T = 0 K with an upper critical field of 31.74 T in the parallel case and 23.5 T in the perpendicular case. Direct measurements of a magnetic-field sweep at 4.2 K show a linear behavior, confirmed by a linear fit for magnetic fields perpendicular to the film plane. Furthermore, we observed a change of up to 12% of the anisotropy ratio in dependence of the film thickness.

  5. Magnetic neutron scattering resonance of high-¤Tc¤ superconductors in external magnetic fields: An SO(5) study

    DEFF Research Database (Denmark)

    Mortensen, Asger; Rønnow, Henrik Moodysson; Bruus, Henrik

    2000-01-01

    The magnetic resonance at 41 meV observed in neutron scattering studies of YBa2Cu3O7 holds a key position in the understanding of high-T-c, superconductivity. Within the SO(5) model for superconductivity and antiferromagnetism, we have calculated the effect of an applied magnetic field...... space we find that (i) the scattering amplitude is zero at (pi/a,pi/a), (ii) the resonance peak is split into a ring with radius pi/d centered at (pi/a, pi/a), d being the vortex lattice constant, and consequently, (iii) the splitting pi/d scales with the magnetic field as root B....... on the neutron scattering cross section of the magnetic resonance. In the presence of Abrikosov vortices, the neutron scattering cross section shows clear signatures of not only the fluctuations in the superconducting order parameter psi, but also the modulation of the phase of psi due to vortices. In reciprocal...

  6. Relevance of magnetic properties for the characterisation of burnt clays and archaeological tiles

    Science.gov (United States)

    Beatrice, C.; Coïsson, M.; Ferrara, E.; Olivetti, E. S.

    The archaeomagnetism of pottery, bricks and tiles is typically employed for dating inferences, yet the magnetic properties of ancient ceramics can also be convenient for their characterisation, to evaluate the technological conditions applied for their production (temperature, atmosphere, and duration of firing), as well as to distinguish groups of sherds having different provenance. In this work, the measurement of hysteresis loops has been applied and combined with colour survey to characterise the magnetic properties of burnt clays and archaeological tiles. Four calcareous and non-calcareous clays, along with seventeen tile fragments excavated from the sites of the ancient Roman towns of Pompeii and Gravina di Puglia, in Southern Italy, are examined. The ferrimagnetic character of the clays, in general, enhances with increasing firing temperatures until vitrification processes occur (900-1000 °C) dissolving iron oxides and dispersing the colour and magnetic properties they provide. High values of saturation magnetization are observed in clays with relevant calcareous content after firing above 900 °C, which results in the formation of Ca-silicates able to delay the onset of the vitrification processes. Magnetic properties of the tiles have been evaluated in terms of the high coercivity (i.e. mainly ferrimagnetic) or low coercivity behaviour (i.e. including relevant paramagnetic and superparamagnetic contributions). Enhanced ferrimagnetic character, mostly depending on the growth in number and volume of iron oxide particles, is associated with the development of an intense reddish hue.

  7. Particle shape and magnetization of chondrite meteorites, lunar samples, and impactites

    Science.gov (United States)

    Wasilewski, P.

    1972-01-01

    Extra terrestrial materials, certain materials which have their origin at the earth's surface due to meteoritic impact, or under highly reducing conditions, such as in the case of basaltic flows in contact with coal beds or serpentenites, all contain Fe and FeNi phases with high magnetization values and spherical shape. Normally, the demagnetizing field (H sub D = NI sub S: where N is the demagnetizing factor and I is the saturation magnetization) is corrected for. In disperse systems, such as most natural materials, the particle shape effects are analyzed in terms of the saturation fields, Hs = H sub D = NI sub S and the magnetization differences (Delta I sub S). Discrete size modes of superparamagnetic (SP), multidomain (MD), and single domain (SD) particles result in reduced coercive force (Hc), increase in the value R sub H (ratio of remanent coercive force, H sub R, to H sub C), and decrease in the value R sub I (ratio of remanent magnetization, I sub R, to saturation magnetization, T sub S). The main distinctions between the various natural materials can be made by this approach. Hysteresis loops for terrestrial basalts, Fe and Ni rods and spheres, chondrite meteorites, lunar samples, impactites, and chondritic fusion crust are presented.

  8. Defective iron-oxide nanoparticles synthesised by high temperature plasma processing: a magnetic characterisation versus temperature.

    Science.gov (United States)

    Balasubramanian, C; Joseph, B; Orpe, P B; Saini, N L; Mukherjee, S; Dziedzic-Kocurek, K; Stanek, J; Di Gioacchino, D; Marcelli, A

    2016-11-04

    Magnetic properties and phase compositions of iron-oxide nanoparticles synthesised by a high temperature arc plasma route have been investigated by Mössbauer spectroscopy and high harmonic magnetic AC susceptibility measurements, and correlated with morphological and structural properties for different synthesis conditions. The Mössbauer spectra precisely determined the presence of different iron-oxide fractions in the investigated nanoparticles, while the high harmonic magnetic susceptibility measurements revealed the occurrence of metastable magnetic phases evolving in temperature and time. This study illustrates magnetic properties and dynamics of the magnetic configurations of iron-oxide nanoparticles grown by high temperature plasma, a process less explored so far but extremely useful for synthesising large numbers of nanoparticles for industrial applications.

  9. High-gradient magnetic affinity separation of trypsin from porcine pancreatin

    DEFF Research Database (Denmark)

    Hubbuch, Jürgen; Thomas, Owen R. T.

    2002-01-01

    We introduce a robust and scale-flexible approach to macromolecule purification employing tailor-made magnetic adsorbents and high-gradient magnetic separation technology adapted from the mineral processing industries. Detailed procedures for the synthesis of large quantities of low-cost defined...... increased scale using a high-gradient magnetic separation system to capture loaded benzamidine-linked adsorbents following batch adsorption. With the aid of a simple recycle loop over 80% of the initially adsorbed trypsin was recovered in-line with an overall purification factor of approximate to3.5....... submicron-sized magnetic supports are presented. These support materials exhibit unique features, which facilitate their large-scale processing using high magnetic field gradients, namely sufficiently high magnetization, a relatively narrow particle size distribution and ideal superparamagnetism. Following...

  10. High-resolution Magnetic Resonance Imaging of Moyamoya Disease

    Science.gov (United States)

    Yu, Le-Bao; Zhang, Qian; Shi, Zhi-Yong; Wang, Ming-Qiu; Zhang, Dong

    2015-01-01

    Objective: To introduce the imaging characteristics of moyamoya disease (MMD) using high-resolution magnetic resonance imaging (HR-MRI) and to discuss the role of HR-MRI in differentiating MMD from other intracranial artery diseases, especially intracranial atherosclerotic disease (ICAD). Data Sources: This review was based on the data in articles published between 2005 and 2015, which were obtained from PubMed. The keywords included HR-MRI, MMD, ICAD, and intracranial artery diseases. Study Selection: Articles related to HR-MRI for MMD or other intracranial artery diseases were selected for review. Results: There are differences between the characteristic patterns of HR-MRI in MMD and ICAD. MMD is associated with inward remodeling, smaller outer diameters, concentric occlusive lesions and homogeneous signal intensity, while ICAD is more likely to be associated with outward remodeling, normal outer diameters, eccentric occlusive lesions, and heterogeneous signal intensity. Other intracranial artery diseases, such as dissection and vasculitis, also have distinctive characteristics in HR-MRI. HR-MRI may become a useful tool for the differential diagnosis of MMD in the future. Conclusions: HR-MRI of MMD provides a more in-depth understanding of MMD, and it is helpful in evaluating pathological changes in the vessel wall and in differentiating MMD from other intracranial artery steno-occlusive diseases, particularly ICAD. PMID:26612300

  11. NICER observations of highly magnetized neutron stars: Initial results

    Science.gov (United States)

    Enoto, Teruaki; Arzoumanian, Zaven; Gendreau, Keith C.; Nynka, Melania; Kaspi, Victoria; Harding, Alice; Guver, Tolga; Lewandowska, Natalia; Majid, Walid; Ho, Wynn C. G.; NICER Team

    2018-01-01

    The Neutron star Interior Composition Explorer (NICER) was launched on June 3, 2017, and attached to the International Space Station. The large effective area of NICER in soft X-rays makes it a powerful tool not only for its primary science objective (diagnostics of the nuclear equation state) but also for studying neutron stars of various classes. As one of the NICER science working groups, the Magnetars and Magnetospheres (M&M) team coordinates monitoring and target of opportunity (ToO) observations of magnetized neutron stars, including magnetars, high-B pulsars, X-ray dim isolated neutron stars, and young rotation-powered pulsars. The M&M working group has performed simultaneous X-ray and radio observations of the Crab and Vela pulsars, ToO observations of the active anomalous X-ray pulsar 4U 0142+61, and a monitoring campaign for the transient magnetar SGR 0501+4516. Here we summarize the current status and initial results of the M&M group.

  12. Temperature and frequency dependence of the coercive field of 0.71PbMb1/3Nb2/3O3-0.29PbTiO3 relaxor-based ferroelectric single crystal

    Science.gov (United States)

    Zhang, Yang; Chen, Zhaojiang; Cao, Wenwu; Zhang, Zhongwu

    2017-10-01

    The hysteresis loop of ferroelectric materials becomes narrower with the increase in temperature due to energy barrier reduction, while the coercive field level increases with frequency due to the inertia of polarization reversal. These two competing effects determine the limiting operation field of medical imaging transducers at high frequencies. We have measured the coercive field of the 0.71PbMb1/3Nb2/3O3-0.29PbTiO3 single crystal as functions of both temperature and frequency. It was found that the coercive field linearly decreases with temperature at all frequencies. Related theoretical analysis was also performed to understand the physics behind the observed phenomena.

  13. Crystallization and magnetic characterizations of DyIG and HoIG nanopowders fabricated using citrate sol-gel

    Directory of Open Access Journals (Sweden)

    Dao Thi Thuy Nguyet

    2016-06-01

    Full Text Available Dy and Ho iron garnets in form of nanoparticles were synthesized by citrate sol-gel method. Phase formation, lattice constant and average crystallite sizes of the samples were determined via XRD measurements. Morphology and particle size distribution were studied by TEM and chemical composition was checked by EDX. Magnetic measurements in temperature range 5–600 K and in the maximum applied field of 50 kOe were carried out by using SQUID and VSM. Their magnetic parameters, including Curie temperature, magnetization compensation temperature, spontaneous magnetization, high-field susceptibility, magnetic coercivity were discussed in the framework of three interacting magnetic sublattices, magnetocrystalline anisotropy, core-shell model and compared to those of the bulk materials. Based on these analyses further evaluation on the crystallinity and homogeneity of the samples has been made.

  14. Rock Magnetic Properties of a Late Pleistocene Paleosol From Central Mexico

    Science.gov (United States)

    Rivas, J.; Ortega, B.; Solleiro, E.; Sedov, S.

    2005-05-01

    Rock-magnetic characteristics of a volcaniclastic-paleosol sequence from Tlaxcala, central Mexico, are analyzed in order to test the hypothesis of neo-formation of magnetic minerals as result of enhanced pedogenesis in A and B soil horizons, in comparison of the less affected or pedoganically unaltered parent material. Our study was carried out in a Chromic luvisol pedocomplex thought to have been formed during the last interglacial. The results show that, even if pedogenic fine grained magnetic minerals are present in the Bt horizons, these are destroyed in upper horizons, where pedogenesis has been more intense. Horizons A and E present the lowest magnetic susceptibility, however they also present the highest concentration of high coercivity hematite/goethite phases. In order to decode the paleoclimatic signal of this paleosol, rock-magnetism analysis in different pedogenetic materials as the soil itself, and cutans, cracks-filling material and humus found in soils, is in progress.

  15. Design of the EuCARD High-Field Model Dipole Magnet FRESCA2

    CERN Document Server

    Milanese, A; Durante, M; Manil, P; Perez, J C; Rifflet, J M; de Rijk, G; Rondeaux, F

    2012-01-01

    This paper reports on the design of FRESCA2, a dipole magnet model wound with Nb3Sn Rutherford cable. This magnet is one of the deliverables of the High Field Magnets work package of the European FP7-EuCARD project. The nominal magnetic flux density of 13 Tesla in a 100 mm bore will make it suitable for upgrading the FRESCA cable test facility at CERN. The magnetic layout is based on a block coil, with four layers per pole. The mechanical structure is designed to provide adequate pre-stress, through the use of bladders, keys and an aluminum alloy shrinking cylinder.

  16. Design of the EuCARD high field model dipole magnet FRESCA2

    CERN Document Server

    Milanese, A; Durante, M; Manil, P; Perez, J-C; Rifflet, J-M; de Rijk, G; Rondeaux, F

    2011-01-01

    This paper reports on the design of FRESCA2, a dipole magnet model wound with Nb3Sn Rutherford cable. This magnet is one of the deliverables of the High Field Magnets work package of the European FP7-EuCARD project. The nominal magnetic flux density of 13 Tesla in a 100 mm bore will make it suitable for upgrading the FRESCA cable test facility at CERN. The magnetic layout is based on a block coil, with four layers per pole. The mechanical structure is designed to provide adequate pre-stress, through the use of bladders, keys and an aluminum alloy shrinking cylinder.

  17. The Characterization of the Magnetic Properties of Soft Magnetic Materials

    DEFF Research Database (Denmark)

    Larsen, Raino Michael

    1996-01-01

    The hysteresis curve and magnetic properties such as permeability, saturation induction, residual induction, coercive force and hysteresis losses are presented. The design and construction of equipment making it possible to measure true DC-values as well as AC-properties of toroid rings...

  18. Numerical simulation of screening current distribution in HTS tape of high field magnet

    OpenAIRE

    Itoh, Ryusei; Oga, Yuki; Noguchi, So; Igarashi, Hajime; Ueda, Hiroshi

    2013-01-01

    In recent years, properties of high temperature superconducting (HTS) tapes, especially in-field performance and mechanical strength, have been continuously improved. The HTS tapes have been widely used for high field (>20 T) magnet researches and there are several technical challenges including field attenuation of an HTS magnet by screening currents induced within the HTS tapes. Several publications reported that the screening currents, induced by penetration of self magnetic fields into HT...

  19. Assessment of coercive and noncoercive pressures to enter drug abuse treatment.

    Science.gov (United States)

    Marlowe, D B; Kirby, K C; Bonieskie, L M; Glass, D J; Dodds, L D; Husband, S D; Platt, J J; Festinger, D S

    1996-10-01

    This paper reports preliminary data derived from a standardized interview scoring procedure for detecting and characterizing coercive and noncoercive pressures to enter substance abuse treatment. Coercive and noncoercive pressures stemming from multiple psychosocial domains are operationalized through recourse to established behavioral principles. Inter-rater reliability for the scoring procedure was exceptional over numerous rater trials. Substantive analyses indicate that, among clients in outpatient cocaine treatment, 'coercion' is operative in multiple psychosocial domains, and that subjects perceive legal pressures as exerting substantially less influence over their decisions to enter treatment than informal psychosocial pressures. Implications for drug treatment planning, legal and ethical issues, and directions for future research are proposed.

  20. Metallic magnetic calorimeters for high resolution X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Krantz, M.; Hengstler, D.; Geist, J.; Schoetz, C.; Hassel, K.; Hendricks, S.; Keller, M.; Kempf, S.; Gastaldo, L.; Fleischmann, A.; Enss, C. [Heidelberg Univ. (Germany). KIP

    2015-07-01

    We develop microfabricated, energy dispersive particle detector arrays based on metallic magnetic calorimeters (MMCs) for high resolution X-ray spectroscopy to challenge bound-state QED calculations. Our MMCs are operated at about T=30 mK and use a paramagnetic temperature sensor, read-out by a SQUID, to measure the energy deposited by single X-ray photons. We discuss the physics of MMCs, the detector performance and the cryogenic setups for two different detector arrays. We present their microfabrication layouts with focus on challenges like the heatsinking of each pixel of the detector and the overhanging absorbers. The maXs-20 detector is a linear 1x8-pixel array with excellent linearity in its designated energy range up to 20 keV and unsurpassed energy resolution of 1.6 eV for 6 keV x-rays. MaXs-20 operated in a highly portable pulse tube cooled ADR setup has already been used at the EBIT facilities of the MPI-K for new reference measurements of V-like and Ti-like tungsten. The maXs-30 detector currently in development is a 8x8-pixel 2d-array with an active detection area of 16 mm{sup 2} and is designed to detect X-rays up to 50 keV with a designated energy resolution below 5 eV. MaXs-30 will be operated in a cryogen free 3He/4He-dilution refrigerator at the tip of a 40 cm long cold finger at T=20 mK.

  1. Magnetic structure and magnetization of helical antiferromagnets in high magnetic fields perpendicular to the helix axis at zero temperature

    Science.gov (United States)

    Johnston, David C.

    2017-09-01

    The zero-temperature angles of magnetic moments in a helix or sinusoidal fan confined to the x y plane, with respect to an in-plane magnetic field Hx applied perpendicular to the z axis of a helix or fan, are calculated for commensurate helices and fans with field-independent turn angles k d between moments in adjacent layers of the helix or fan using the classical J0-J1-J2 Heisenberg model. For 0 10.1103/PhysRevB.94.014422] for single-crystal EuCo2P2 possessing a helix ground state with k d ≈0.85 π . The low-field magnetic susceptibility and the ratio Ht/Hc are calculated analytically or numerically versus k d for helices, and are shown to approach the respective known limits for k d →0 .

  2. Magnetization in permalloy thin films

    Indian Academy of Sciences (India)

    For the samples prepared with increased nitrogen partial pressure the magnetic moment decreased rapidly and the values of coercivity increased. The polarized neutron reflectivity measurements (PNR) were performed in the sample prepared with only Ar gas and with nitrogen partial pressure of 5 and 10%. It was found ...

  3. High-performance pulsed magnets: Theory, design and construction

    Science.gov (United States)

    Li, Liang

    This thesis is an in-depth study of the design and construction of coils for pulsed magnets energised by a capacitor bank, including mathematical modelling and testing of the coils. The magnetic field generated by solenoid magnets with homogeneous and non-homogenous current distribution is calculated with the elliptical integral method. Coupled partial differential equations for magnetic and thermal diffusion and the electric circuits are solved numerically to calculate the pulse shape and the heating in a pulsed magnet. The calculations are in good agreement with test results for a large range of different coils; this provides useful insights for optimised coil design. Stresses and strains in the mid-plane of the coil are analytically calculated by solving the system of equations describing the displacement in each layer of the coil. Non-linear stress-strain characteristics and the propagation of the plastic deformation are taken into account by sub- dividing each layer of the coil in the radial direction and changing the elastic-plastic matrix at each transition point. Conductors, insulating materials and techniques used for pulsed magnets are discussed in detail. More than 80 pulsed magnets with optimised combinations of conductors and reinforcements have been built and tested, with peak fields in the range 45-73 T and a bore size from 8 mm-35 mm. The pulse duration is of the order of 10 milliseconds. A dual stage pulsed magnet for use at a free electron laser has been developed. This has a rise time of 10 microseconds and enables magneto-optical experiments in a parameter range previously inaccessible to condensed matter physicists. The joint of superconducting cables can be modelled by means of distributed circuit elements that characterise current diffusion.

  4. High magnetization aqueous ferrofluid: A simple one-pot synthesis

    Science.gov (United States)

    Carroll, Kyler J.; Shultz, Michael D.; Fatouros, Panos P.; Carpenter, Everett E.

    2010-05-01

    A one-step polyol method was utilized to prepare a stable aqueous iron/iron oxide ferrofluid. The dried powders were characterized by x-ray diffraction, electron microscopy, x-ray absorption spectroscopy, and vibrating sample magnetometry for the determination of phase, morphology, and magnetic properties. To show its potential for imaging applications, the ferrofluid was also investigated as a magnetic resonance imaging contrast agent.

  5. Justifications for coercive care in child and adolescent psychiatry, a content analysis of medical documentation in Sweden.

    Science.gov (United States)

    Pelto-Piri, Veikko; Kjellin, Lars; Lindvall, Christina; Engström, Ingemar

    2016-02-19

    There has been considerable interest in normative ethics regarding how and when coercive care can be justified. However, only a few empirical studies consider how professionals reason about ethical aspects when assessing the need for coercive care for adults, and even less concerning children and adolescents. The aim of this study was to examine and describe how professionals document their value arguments when considering the need for coercive psychiatric care of young people. All 16 clinics that admitted children or adolescents to coercive care during one year in Sweden were included in the study. These clinics had a total of 155 admissions of 142 patients over one year. Qualitative content analysis with a deductive approach was used to find different forms of justification for coercive care that was documented in the medical records, including Care Certificates. The analysis of medical records revealed two main arguments used to justify coercive care in child and adolescent psychiatry: 1) the protection argument - the patients needed protection, mainly from themselves, and 2) the treatment requirement argument - coercive care was a necessary measure for administering treatment to the patient. Other arguments, namely the caregiver support argument, the clarification argument and the solidarity argument, were used primarily to support the two main arguments. These supportive arguments were mostly used when describing the current situation, not in the explicit argumentation for coercive care. The need for treatment was often only implicitly clarified and the type of care the patient needed was not specified. Few value arguments were used in the decision for coercive care; instead physicians often used their authority to convince others that treatment was necessary. One clinical implication of the study is that decisions about the use of coercive care should have a much stronger emphasis on ethical aspects. There is a need for an ethical legitimacy founded upon

  6. High-force magnetic tweezers with force feedback for biological applications.

    Science.gov (United States)

    Kollmannsberger, Philip; Fabry, Ben

    2007-11-01

    Magnetic micromanipulation using magnetic tweezers is a versatile biophysical technique and has been used for single-molecule unfolding, rheology measurements, and studies of force-regulated processes in living cells. This article describes an inexpensive magnetic tweezer setup for the application of precisely controlled forces up to 100 nN onto 5 microm magnetic beads. High precision of the force is achieved by a parametric force calibration method together with a real-time control of the magnetic tweezer position and current. High forces are achieved by bead-magnet distances of only a few micrometers. Applying such high forces can be used to characterize the local viscoelasticity of soft materials in the nonlinear regime, or to study force-regulated processes and mechanochemical signal transduction in living cells. The setup can be easily adapted to any inverted microscope.

  7. Synthesis of crystalline CoFe{sub x} nanowire arrays through high voltage pulsed electrochemical deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Renlong; Cao, Chuanbao, E-mail: cbcao@bit.edu.cn; Chen, Zhuo; Yao, Ruimin

    2014-08-01

    A high voltage pulsed electrochemical deposition (50 Hz, −50 V) technique was used to synthesize CoFe{sub x} (x=1.57, 2.02) nanowire arrays in anodic aluminum oxide templates. The nanowire arrays (NA) are different in diameter (NA A, 40 nm; NA B, 50 nm), center-to-center distance (NA A, 60 nm; NA B, 100 nm) and length (NA A, 4 μm; NA B, 8 μm). Microstructural characterization shows high crystallinity of the formed nanowires. The magnetic measurements indicate that the nanowire arrays possess uniaxial anisotropy with the easy magnetization axis along the nanowire. When magnetic field is applied in this direction, the coercivities of both nanowire arrays are larger than 1600 Oe. The shape difference between two magnetization hysteresis loops is due to dipolar magnetostatic interaction, and analytical calculation is performed to interpret the magnetic properties as a function of the wire geometry. The results suggest that during high voltage electrodeposition, reduced atoms are highly energetic and the crystallographic growth planes can be (110), (111) and (211). - Highlights: • High voltage pulsed electrochemical deposition technique (−50 V) is employed. • Nanowire arrays exhibit high coercivities (>1600 Oe). • Crystallites with high crystallinity and different growth orientations are discovered in the nanowires. • The high-energetic reduced atoms can stack on the usually reported (110) plane together with (111) or (211) plane. • The shape difference between two magnetization hysteresis loops is due to dipolar magnetostatic interaction.

  8. A new hybrid protection system for high-field superconducting magnets

    NARCIS (Netherlands)

    Ravaioli, Emanuele; Datskov, V.I.; Kirby, G.; ten Kate, Herman H.J.; Verweij, A.P.

    2014-01-01

    The new generation of high-field superconducting accelerator magnets poses a challenge concerning the protection of the magnet coil in the case of a quench. The very high stored energy per unit volume requires a fast and efficient quench heating system in order to avoid damage due to overheating. A

  9. In vivo high field magnetic resonance imaging and spectroscopy of adult zebrafish

    NARCIS (Netherlands)

    Kabli, Samira

    2009-01-01

    This thesis contains the results of imaging of adult zebrafish by using different MR approaches. We present the first high resolution mMR images of adult zebrafish. To achieve high spatial resolution we used a magnetic field of 9.4T, in combination with strong magnetic field gradients (1000 mT/m)

  10. High-resolution imaging of remanent state and magnetization reversal of superdomain structures in high-density cobalt antidot arrays.

    Science.gov (United States)

    Rodríguez, L A; Magén, C; Snoeck, E; Gatel, C; Castán-Guerrero, C; Sesé, J; García, L M; Herrero-Albillos, J; Bartolomé, J; Bartolomé, F; Ibarra, M R

    2014-09-26

    Remanent state and magnetization reversal processes of a series of cobalt antidot arrays with a fixed hole diameter (d ≈ 55 nm) and an array periodicity (p) ranging between 95 and 524 nm were studied by in situ Lorentz microscopy (LM) as a function of the magnetic field. At remanence, defocused LM images showed the periodicity dependence of the magnetic states inside the lattice. A remarkable transition was observed in the type of domain structures as a function of p: for the large periodicities (p > 300 nm), conventional 90° and 180° domain walls were formed, whereas in small-period antidot arrays (p ≦ 160 nm) magnetic superdomain walls (SDWs) were nucleated to separate regions with different average magnetization direction, the so-called magnetic superdomains. In the SDW regime, a low-frequency Fourier filtering method was implemented to allow a quantitative analysis of the LM images by the transport of intensity equation method. In situ LM experiments under applied magnetic fields were performed to study the reversal magnetization process in a particular array (p = 160 nm), and clear differences were observed as a function of the magnetic field orientation. The switching process under magnetic fields parallel to the horizontal antidot rows occurs in two stages: the system first nucleates and propagates horizontal SDWs, parallel to the field. Then, at higher magnetic fields, vertical SDWs, perpendicular to the field, appear before saturation. When the magnetic field is applied at 45° with respect to the antidot rows, both horizontal and vertical SDWs are nucleated and propagated simultaneously. All the experiments were successfully correlated with micromagnetic simulations. The current study sheds new light on the magnetization reversal processes of antidot arrays and opens new possibilities of exploiting the potential of high-resolution in situ LM and new data analysis procedures to probe magnetization processes in nanomagnetism, particularly in

  11. An application of high-temperature superconductors YBCO to magnetic separation

    Science.gov (United States)

    Guo, Qiudong; Zhang, Peng; Bo, Lin; Zeng, Guibin; Li, Dengqian; Fan, J. D.; Liu, Huajun

    2017-10-01

    With the rapid development of manufacturing technology of high temperature superconductive YBa2Cu3O7‑x YBCO materials and decreasing in cost of production, YBCO is marching into industrial areas with its good performances as source of high-magnetic field and rather low cost in reaching superconductivity. Based on analysis of the performance of high temperature superconductors YBCO and development of technology in superconductive magnetic separation both home and abroad, we propose a new approach of taking YBCO tape to make a solenoid as the source of a high magnetic field of magnetic separatior of ores. The paper also looks into the future of the YBCO high temperature superconductive magnetic separation from the perspective of technology and cost, as well as its applications in other industries.

  12. Measurement of magnetic property of FePt granular media at near Curie temperature

    Science.gov (United States)

    Yang, H. Z.; Chen, Y. J.; Leong, S. H.; An, C. W.; Ye, K. D.; Hu, J. F.

    2017-02-01

    The characterization of the magnetic switching behavior of heat assisted magnetic recording (HAMR) media at near Curie temperature (Tc) is important for high density recording. In this study, we measured the magnetic property of FePt granular media (with room temperature coercivity 25 kOe) at near Tc with a home built HAMR testing instrument. The local area of HAMR media is heated to near Tc by a flat-top optical heating beam. The magnetic property in the heated area was in-situ measured by a magneto-optic Kerr effect (MOKE) testing beam. The switching field distribution (SFD) and coercive field (Hc) of the FePt granular media and their dependence on the optical heating power at near Tc were studied. We measured the DC demagnetization (DCD) signal with pulsed laser heating at different optical powers. We also measured the Tc distribution of the media by measuring the AC magnetic signal as a function of optical heating power. In a summary, we studied the SFD, Hc of the HAMR media at near Tc in a static manner. The present methodology will facilitate the HAMR media testing.

  13. Beyond Magnet® Designation: Perspectives From Nurse Managers on Factors of Sustainability and High-Performance Programming.

    Science.gov (United States)

    Hayden, Margaret A; Wolf, Gail A; Zedreck-Gonzalez, Judith F

    2016-10-01

    The aim of this study was to identify patterns of high-performing behaviors and nurse manager perceptions of the factors of Magnet® sustainability at a multidesignated Magnet organization. The Magnet program recognizes exemplary professional nursing practice and is challenging to achieve and sustain. Only 10% (n = 42) of Magnet hospitals sustained designation for 12 years or longer. This study explored the perspectives of Magnet nurse managers regarding high-performing teams and the sustainability of Magnet designation. A qualitative study of nurse managers was conducted at 1 multidesignated Magnet organization (n = 13). Interview responses were analyzed using pattern recognition of Magnet model domains and characteristics of high-performing teams and then related to factors of Magnet sustainability. Transformational leadership is both an essential factor for sustainability and a potential barrier to sustainability of Magnet designation. Transformational nursing leaders lead high-performing teams and should be in place at all levels as an essential factor in sustaining Magnet redesignation.

  14. DOUBLE DEGENERATE MERGERS AS PROGENITORS OF HIGH-FIELD MAGNETIC WHITE DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Berro, Enrique; Loren-Aguilar, Pablo; Aznar-Siguan, Gabriela; Torres, Santiago; Camacho, Judit [Departament de Fisica Aplicada, Universitat Politecnica de Catalunya, c/Esteve Terrades, 5, 08860 Castelldefels (Spain); Althaus, Leandro G.; Corsico, Alejandro H. [Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, (1900) La Plata (Argentina); Kuelebi, Baybars; Isern, Jordi, E-mail: garcia@fa.upc.edu [Institute for Space Studies of Catalonia, c/Gran Capita 2-4, Edif. Nexus 104, 08034 Barcelona (Spain)

    2012-04-10

    High-field magnetic white dwarfs have been long suspected to be the result of stellar mergers. However, the nature of the coalescing stars and the precise mechanism that produces the magnetic field are still unknown. Here, we show that the hot, convective, differentially rotating corona present in the outer layers of the remnant of the merger of two degenerate cores can produce magnetic fields of the required strength that do not decay for long timescales. Using a state-of-the-art Monte Carlo simulator, we also show that the expected number of high-field magnetic white dwarfs produced in this way is consistent with that found in the solar neighborhood.

  15. Unipolar and Bipolar High-Magnetic-Field Sensors Based on Surface Acoustic Wave Resonators

    Science.gov (United States)

    Polewczyk, V.; Dumesnil, K.; Lacour, D.; Moutaouekkil, M.; Mjahed, H.; Tiercelin, N.; Petit Watelot, S.; Mishra, H.; Dusch, Y.; Hage-Ali, S.; Elmazria, O.; Montaigne, F.; Talbi, A.; Bou Matar, O.; Hehn, M.

    2017-08-01

    While surface acoustic wave (SAW) sensors have been used to measure temperature, pressure, strains, and low magnetic fields, the capability to measure bipolar fields and high fields is lacking. In this paper, we report magnetic surface acoustic wave sensors that consist of interdigital transducers made of a single magnetostrictive material, either Ni or TbFe2 , or based on exchange-biased (Co /IrMn ) multilayers. By controlling the ferromagnet magnetic properties, high-field sensors can be obtained with unipolar or bipolar responses. The issue of hysteretic response of the ferromagnetic material is especially addressed, and the control of the magnetic properties ensures the reversible behavior in the SAW response.

  16. 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...

  17. Nanostructure and magnetic properties of Ni-substituted finemet ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Iturriza, N. [Dpto. Fisica Materiales, Fac. Quimica, UPV/EHU, Apdo. 1072, 20080 San Sebastian (Spain); Fernandez, L. [Dpto. Fisica Materiales, Fac. Quimica, UPV/EHU, Apdo. 1072, 20080 San Sebastian (Spain); Ipatov, M. [Dpto. Fisica Materiales, Fac. Quimica, UPV/EHU, Apdo. 1072, 20080 San Sebastian (Spain); Vara, G. [Dpto. Ingenieria Quimica y Medio Ambiente, EUPSS, YPV/EHU, 20080 San Sebastian (Spain); Pierna, A.R. [Dpto. Ingenieria Quimica y Medio Ambiente, EUPSS, YPV/EHU, 20080 San Sebastian (Spain); Val, J.J. del [Dpto. Fisica Materiales, Fac. Quimica, UPV/EHU, Apdo. 1072, 20080 San Sebastian (Spain) and Unidad de Fisica de Materiales, Centro Mixto CSIC-UPV/EHU, San Sebastian (Spain)]. E-mail: juanjose.delval@ehu.es; Chizhik, A. [Dpto. Fisica Materiales, Fac. Quimica, UPV/EHU, Apdo. 1072, 20080 San Sebastian (Spain); Gonzalez, J. [Dpto. Fisica Materiales, Fac. Quimica, UPV/EHU, Apdo. 1072, 20080 San Sebastian (Spain)

    2007-09-15

    Magnetic anisotropy has been induced during the nanocrystallization process of Ni-rich amorphous ferromagnetic (Finemet) ribbons by means of the application of a constant stress during the annealing process. Magnetization measurements have evidenced the anisotropy of the treated samples. The main goal of this work was the analysis of the treated ribbons using X-ray Diffraction (XRD), Transmission Electronic Microscopy (TEM) and Atomic Force Microscopy (AFM). AFM measurements revealed in all the cases a strong nanocrystallisation of the surface without evidences of amorphous matrix, which contrast with XRD and TEM measurements that have shown a high content of amorphous phase in the bulk of the ribbons. Magneto-optical Kerr effect measurements show much higher coercive field values than in the bulk, indicating a complex magnetic behavior for the surface of the ribbons.

  18. High Resolution Marine Magnetic Survey of Shallow Water Littoral Area

    Directory of Open Access Journals (Sweden)

    Jacob Sharvit

    2007-09-01

    Full Text Available The purpose of this paper is to present a system developed for detection andaccurate mapping of ferro-metallic objects buried below the seabed in shallow waters. Thesystem comprises a precise magnetic gradiometer and navigation subsystem, both installedon a non-magnetic catamaran towed by a low-magnetic interfering boat. In addition wepresent the results of a marine survey of a near-shore area in the vicinity of Atlit, a townsituated on the Mediterranean coast of Israel, about 15 km south of Haifa. The primarypurpose of the survey was to search for a Harvard airplane that crashed into the sea in 1960.A magnetic map of the survey area (3.5 km2 on a 0.5 m grid was created revealing theanomalies at sub-meter accuracy. For each investigated target location a correspondingferro-metallic item was dug out, one of which turned to be very similar to a part of thecrashed airplane. The accuracy of location was confirmed by matching the position of theactual dug artifacts with the magnetic map within a range of ± 1 m, in a water depth of 9 m.

  19. Termination layer compensated tunnelling magnetoresistance in ferrimagnetic Heusler compounds with high perpendicular magnetic anisotropy

    National Research Council Canada - National Science Library

    Jeong, Jaewoo; Ferrante, Yari; Faleev, Sergey V; Samant, Mahesh G; Felser, Claudia; Parkin, Stuart S P

    2016-01-01

    ...-tunnelling magnetoresistance in the latter. Here we report the preparation of highly textured, polycrystalline Mn3Ge films on amorphous substrates, with very high magnetic anisotropy fields exceeding 7 T, making them technologically relevant...

  20. Effect of cooling rate on the phase structure and magnetic properties of Fe{sub 26.7}Co{sub 28.5}Ni{sub 28.5}Si{sub 4.6}B{sub 8.7}P{sub 3} high entropy alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Ran; Sun, Huan; Chen, Chen [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Han, Zhenhua [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710068 (China); Li, Fushan, E-mail: fsli@zzu.edu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China)

    2017-08-01

    Highlights: • High entropy alloy with amorphous phase and FCC solid solution phase are successfully developed respectively. • The amorphous phase exhibits better soft magnetic properties than that of the solid solution phase. • The BCC phase transformed into FCC phase, and then into BCC phase was found in this HEA. - Abstract: The effect of cooling rate on phase structure and magnetic properties of the Fe{sub 26.7}Co{sub 28.5}Ni{sub 28.5}Si{sub 4.6}B{sub 8.7}P{sub 3} high entropy alloy (HEA) was investigated. The HEA forms into amorphous phase by melt spinning method at high cooling rate and FCC solid solution phase at low cooling rate. The soft magnetic properties of the amorphous phase (saturation magnetization B{sub s} of 1.07T and coercivity H{sub c} of 4 A/m) are better than that of the solid solution phase (B{sub s} of 1.0 T and H{sub c} of 168 A/m). In order to study the phase evolution of the present HEA, anneal experiments were conducted. It is found that crystallization products of amorphous phase are solid solution phase which constitute much of FCC and a small amount of BCC. BCC phase transforms into FCC phase, and then into BCC phase with the increase of annealing temperature.

  1. Formation and texture of Bi-2223 phase during sintering in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Lu, X.Y.; Nagata, A.; Watanabe, K.; Nojima, T.; Sugawara, K.; Hanada, S.; Kamada, S

    2003-10-15

    The formation and texture of Bi-2223 phase during sintering in high magnetic fields were investigated. Samples contained in silver crucibles were sintered at different temperatures from 835 to 860 deg. C for 120 h in a vertical tube furnace installed in a solenoid-type superconducting magnet. A vertical magnetic field, H{sub a} of 10 T can be applied parallel to the long axis of the furnace. It has been found that the mixed structures of the Bi-2223 and the Bi-2212 grains with their c-axis parallel to the magnetic field are formed in samples sintered at 850-855 deg. C in 10 T magnetic field. Below 845 deg. C sintering in 10 T, a high proportion of Bi-2223 phase is obtained, however no preferred orientation is observed. It is suggested that a liquid phase is important for the formation of the textured structure in magnetic fields.

  2. Spin Torque Oscillator for High Performance Magnetic Memory

    Directory of Open Access Journals (Sweden)

    Rachid Sbiaa

    2015-06-01

    Full Text Available A study on spin transfer torque switching in a magnetic tunnel junction with perpendicular magnetic anisotropy is presented. The switching current can be strongly reduced under a spin torque oscillator (STO, and its use in addition to the conventional transport in magnetic tunnel junctions (MTJ should be considered. The reduction of the switching current from the parallel state to the antiparallel state is greater than in  the opposite direction, thus minimizing the asymmetry of the resistance versus current in the hysteresis loop. This reduction of both switching current and asymmetry under a spin torque oscillator occurs only during the writing process and does not affect the thermal stability of the free layer.

  3. Generation and measurement of pulsed high magnetic field

    CERN Document Server

    Jana, S

    2000-01-01

    Pulsed magnetic field has been generated by discharging a capacitor bank through a 5-layer air-core solenoid. The strength of the magnetic field at its peak has been measured using the voltage induced in various pick-up coils, and also from the Zeeman splitting of an ion having a known g value. Synchronizing a xenon flash at the peak of the magnetic field, this lab-made instrument has been made well suited to study the Zeeman effect, etc. at a temperature of 25 K. As an application of this setup, we have investigated the Zeeman splitting of the sup 4 I sub 9 sub / sub 2-> sup 4 G sub 5 sub / sub 2 transition of the Nd sup 3 sup + -doped CsCdCl sub 3 crystal at 7.8 T, and determined the splitting factors.

  4. Highly Water-Soluble Magnetic Nanoparticles as Novel Draw Solutes in Forward Osmosis for Water Reuse

    KAUST Repository

    Ling, Ming Ming

    2010-06-16

    Highly hydrophilic magnetic nanoparticles have been molecularly designed. For the first time, the application of highly water-soluble magnetic nanoparticles as novel draw solutes in forward osmosis (FO) was systematically investigated. Magnetic nanoparticles functionalized by various groups were synthesized to explore the correlation between the surface chemistry of magnetic nanoparticles and the achieved osmolality. We verified that magnetic nanoparticles capped with polyacrylic acid can yield the highest driving force and subsequently highest water flux among others. The used magnetic nanoparticles can be captured by the magnetic field and recycled back into the stream as draw solutes in the FO process. In addition, magnetic nanoparticles of different diameters were also synthesized to study the effect of particles size on FO performance. We demonstrate that the engineering of surface hydrophilicity and magnetic nanoparticle size is crucial in the application of nanoparticles as draw solutes in FO. It is believed that magnetic nanoparticles will soon be extensively used in this area. © 2010 American Chemical Society.

  5. Performance analysis of a microfluidic mixer based on high gradient magnetic separation principles

    Science.gov (United States)

    Liu, Mengyu; Han, Xiaotao; Cao, Quanliang; Li, Liang

    2017-09-01

    To achieve a rapid mixing between a water-based ferrofluid and DI water in a microfluidic environment, a magnetically actuated mixing system based on high gradient magnetic separation principles is proposed in this work. The microfluidic system consists of a T-shaped mirochannel and an array of integrated soft-magnetic elements at the sidewall of the channel. With the aid of an external magnetic bias field, these elements are magnetized to produce a magnetic volume force acting on the fluids containing magnetic nanoparticles, and then to induce additional flows for improving the mixing performance. The mixing process is numerically investigated through analyzing the concentration distribution of magnetic nanoparticles using a coupled particle-fluid transport model, and mixing performances under different parametrical conditions are investigated in detail. Numerical results show that a high mixing efficiency around 97.5% can be achieved within 2 s under an inlet flow rate of 1 mm s-1 and a relatively low magnetic bias field of 50 mT. Meanwhile, it has been found that there is an optimum number of magnetic elements used for obtaining the best mixing performance. These results show the potential of the proposed mixing method in lab-on-a-chip system and could be helpful in designing and optimizing system performance.

  6. Preparation of magnetic rubber with high mechanical properties by latex compounding method

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Chunlin [Shanxi Province Key Laboratory of Functional Nanocomposites, North University of China, Taiyuan 030051 (China); College of Materials Science and Engineering, North University of China, Taiyuan 030051 (China); Gao, Li; Yu, Hailing [Shanxi Province Key Laboratory of Functional Nanocomposites, North University of China, Taiyuan 030051 (China); Sun, Youyi, E-mail: syyi@pku.edu.cn [Shanxi Province Key Laboratory of Functional Nanocomposites, North University of China, Taiyuan 030051 (China); College of Materials Science and Engineering, North University of China, Taiyuan 030051 (China); Yao, Junru; Zhao, Guizhe [Shanxi Province Key Laboratory of Functional Nanocomposites, North University of China, Taiyuan 030051 (China); Liu, Yaqing, E-mail: lyqzgz2010@163.com [Shanxi Province Key Laboratory of Functional Nanocomposites, North University of China, Taiyuan 030051 (China); College of Materials Science and Engineering, North University of China, Taiyuan 030051 (China)

    2016-06-01

    the magnetic rubber based on Fe{sub 3}O{sub 4} nanoparticles and nature rubber were prepared by latex compounding method, in which stable Fe{sub 3}O{sub 4} aqueous solutions were mixed with natural rubber latex and additives. This process was fast, versatile, reliable, safe, environmentally friendly and inexpensive. What’s more, it was found that the magnetic and mechanical properties of magnetic rubber increased together with increase in doping content of Fe{sub 3}O{sub 4} nanoparticles. Especially, it was demonstrated that the tensile strength (25.0 Mpa) of magnetic rubber was improved to be 478.0% comparing to neat natural rubber (5.2 Mpa), which was 5 times higher than maximal value reported in previous work. At the same time, the magnetic rubber revealed better thermal stability and solvent resistance comparing to the neat natural rubber, too. The work dose not only provides a new way to environmentally friendly preparation of magnetic rubber at low temperature, but also improve the mechanical and magnetic properties of magnetic rubber applied in industry. - Highlights: • The magnetic rubber was prepared by a latex compounding method. • The magnetic rubber exhibited high mechanical properties. • The mechanism of high mechanical properties was investigated by the NMR.

  7. Voting and violence in KwaZulu-Natal's no-go areas: Coercive ...

    African Journals Online (AJOL)

    This paper analyses post-confl ict elections in war-to-democracy transitions by comparing support structures for confl ict parties as well as their coercive mobilisation strategies in times of violent confl ict and post-confl ict elections. It does so through a single case study of KwaZulu-Natal. This South African province faced a ...

  8. Voting and violence in KwaZulu- Natal's no-go areas: Coercive ...

    African Journals Online (AJOL)

    into electoral logics of peaceful political contestation. Empirical reality, however, shows that the election process is often accompanied by various forms of violence. This paper analyses post-conflict elections in war-to-democracy transitions by comparing support structures for conflict parties as well as their coercive.

  9. Coercive and legitimate authority impact tax honesty: evidence from behavioral and ERP experiments.

    Science.gov (United States)

    Gangl, Katharina; Pfabigan, Daniela M; Lamm, Claus; Kirchler, Erich; Hofmann, Eva

    2017-07-01

    Cooperation in social systems such as tax honesty is of central importance in our modern societies. However, we know little about cognitive and neural processes driving decisions to evade or pay taxes. This study focuses on the impact of perceived tax authority and examines the mental chronometry mirrored in ERP data allowing a deeper understanding about why humans cooperate in tax systems. We experimentally manipulated coercive and legitimate authority and studied its impact on cooperation and underlying cognitive (experiment 1, 2) and neuronal (experiment 2) processes. Experiment 1 showed that in a condition of coercive authority, tax payments are lower, decisions are faster and participants report more rational reasoning and enforced compliance, however, less voluntary cooperation than in a condition of legitimate authority. Experiment 2 confirmed most results, but did not find a difference in payments or self-reported rational reasoning. Moreover, legitimate authority led to heightened cognitive control (expressed by increased MFN amplitudes) and disrupted attention processing (expressed by decreased P300 amplitudes) compared to coercive authority. To conclude, the neuronal data surprisingly revealed that legitimate authority may led to higher decision conflict and thus to higher cognitive demands in tax decisions than coercive authority. © The Author (2017). Published by Oxford University Press.

  10. Authorities' Coercive and Legitimate Power: The Impact on Cognitions Underlying Cooperation.

    Science.gov (United States)

    Hofmann, Eva; Hartl, Barbara; Gangl, Katharina; Hartner-Tiefenthaler, Martina; Kirchler, Erich

    2017-01-01

    The execution of coercive and legitimate power by an authority assures cooperation and prohibits free-riding. While coercive power can be comprised of severe punishment and strict monitoring, legitimate power covers expert, and informative procedures. The perception of these powers wielded by authorities stimulates specific cognitions: trust, relational climates, and motives. With four experiments, the single and combined impact of coercive and legitimate power on these processes and on intended cooperation of n1 = 120, n2 = 130, n3 = 368, and n4 = 102 student participants is investigated within two exemplary contexts (tax contributions, insurance claims). Findings reveal that coercive power increases an antagonistic climate and enforced compliance, whereas legitimate power increases reason-based trust, a service climate, and voluntary cooperation. Unexpectedly, legitimate power is additionally having a negative effect on an antagonistic climate and a positive effect on enforced compliance; these findings lead to a modification of theoretical assumptions. However, solely reason-based trust, but not climate perceptions and motives, mediates the relationship between power and intended cooperation. Implications for theory and practice are discussed.

  11. Structure and coercivity of nanocrystalline Fe–Si–B–Nb–Cu alloys

    Indian Academy of Sciences (India)

    Unknown

    –Nb–Cu alloys have been investigated. It is found that the primary phase changes from α-Fe(Si) to Fe3Si (DO3) on increasing the Si content. The coercivity of the alloys containing the Fe3Si phase is significantly lower as compared to the alloy ...

  12. Paraphilic Sexual Interests and Sexually Coercive Behavior: A Population-Based Twin Study.

    Science.gov (United States)

    Baur, Elena; Forsman, Mats; Santtila, Pekka; Johansson, Ada; Sandnabba, Kenneth; Långström, Niklas

    2016-07-01

    Prior research with selected clinical and forensic samples suggests associations between paraphilic sexual interests (e.g., exhibitionism and sexual sadism) and sexually coercive behavior. However, no study to date used a large, representative and genetically informative population sample to address the potential causal nature of this association. We used self-report data on paraphilic and sexually coercive behavior from 5990 18- to 32-year-old male and female twins from a contemporary Finnish population cohort. Logistic regression and co-twin control models were employed to examine if paraphilic behaviors were causally related to coercive behavior or if suggested links were confounded by familial (genetic or common family environment) risk factors. Results indicated that associations between four out of five tested paraphilic behaviors (exhibitionism, masochism, sadism, and voyeurism, respectively) and sexually coercive behavior were moderate to strong. Transvestic fetishism was not independently associated with sexual coercion. Comparisons of twins reporting paraphilic behavior with their paraphilic behavior-discordant twin further suggested that associations were largely independent of shared genetic and environmental confounds, consistent with a causal association. In conclusion, similar to previously reported predictive effects of paraphilias on sexual crime recidivism, paraphilic behavior among young adults in the general population increases sexual offending risk. Further, early identification of paraphilic interest and preventive interventions with at-risk individuals might also reduce perpetration of first-time sexual violence.

  13. The coercive force of fine particles of monoclinic pyrrhotite (Fe7S8 ...

    African Journals Online (AJOL)

    The temperature dependence of coercive force (Hc) between 77 K and 600 K has been investigated for fine particles of monoclinic pyrrhotite (Fe7S8) of < 1 mm and 1- 30 mm particle sizes. The study has shown that Hc is strongly dependent on temperature, as temperature rises above room temperature (293 K) to near the ...

  14. Differentiating between Confrontive and Coercive Kinds of Parental Power-Assertive Disciplinary Practices

    Science.gov (United States)

    Baumrind, Diana

    2012-01-01

    In this essay, I differentiate between coercive and confrontive kinds of power assertion to elucidate the significantly different effects on children's well-being of authoritarian and authoritative styles of parental authority. Although both parenting styles (in contrast to the permissive style) are equally demanding, forceful, and…

  15. Predicting commitment in young adults' physically aggressive and sexually coercive dating relationships.

    Science.gov (United States)

    Young, Brennan J; Furman, Wyndol

    2013-11-01

    Intimate partner violence often begins during the courtship stage of romantic relationships. Although some relationships dissolve as a result of aggression, other relationships remain intact, increasing the risk for escalated violence. The present study identified factors predictive of individual differences in emerging adults' commitment to physically aggressive or sexually coercive dating relationships. Specifically, Rusbult's Investment Model of romantic relationships (e.g., investment, satisfaction, quality of alternatives, and commitment) was applied to a longitudinal sample of 148 young adult women who reported experiencing aggression or coercion from their current partners. To further explain commitment within aggressive or coercive dating relationships, rejection sensitivity and anxious and avoidant romantic relational styles were included as predictors of the Investment Model variables. A more avoidant romantic style indirectly predicted commitment through relationship satisfaction and investment. Both commitment and rejection sensitivity significantly predicted continuing an aggressive or coercive relationship 6 months later. The present study improves our understanding of the processes involved in relationship commitment. Continuing to understand these processes will inform interventions that seek to help women who have decided to end aggressive or coercive dating relationships.

  16. Excess use of coercive measures in psychiatry among migrants compared with native Danes.

    Science.gov (United States)

    Norredam, M; Garcia-Lopez, A; Keiding, N; Krasnik, A

    2010-02-01

    To investigate differences in risk of compulsory admission and other coercive measures in psychiatric emergencies among refugees and immigrants compared with that among native Danes. A register-based retrospective cohort design. All refugees (n = 29 174) and immigrants (n = 33 287) who received residence permission in Denmark from 1.1.1993 to 31.12.1999 were included and matched 1 : 4 on age and sex with native Danes. Civil registration numbers were cross-linked to the Danish Psychiatric Central Register and the Registry of Coercive Measures in Psychiatric Treatment. Refugees (RR = 1.82; 95%CI: 1.45; 2.29) and immigrants (RR = 1.14; 95%CI: 0.83; 1.56) experienced higher rates of compulsory admissions than did native Danes. This was most striking for refugee men (RR = 2.00; 95%CI: 1.53; 2.61) and immigrant women (RR = 1.73; 95%CI: 1.45; 2.60). Moreover, refugees and immigrants experienced higher frequencies of other coercive measures during hospitalisation compared with native Danes. Coercive measures in psychiatry are more likely to be experienced by migrants than by native Danes.

  17. Study of coercive measures in prisons and secure psychiatric hospitals: the views of inmates and caregivers

    Directory of Open Access Journals (Sweden)

    A. Runte-Geidel

    2014-06-01

    Full Text Available Aim: The aim of the study was to ascertain the opinions of both inmates and staff of prison establishments about the use of coercive measures justified for clinical reasons for people with mental health problems and about the need to create protocols to regulate the application of these measures. Method: These opinions were gathered in a Qualitative Study with Focus Groups (prison inmates and prison staff from the Granada Penitentiary Centre and the Alicante Penitentiary Psychiatric Hospital, both in Spain. Results: The results showed that forced medication is the most commonly used coercive measure in these institutions. The inmates did not understand and rejected the use of this measure, above all because they were poorly informed about their illness and the medication required to treat it. The staff however defended the benefits of psychiatric medicine, even when administered without the patient's consent. Conclusions: Both inmates and staff agreed that it would be useful to have a protocol regulating the use of coercive measures. The study has also identified a number of important factors that could help to reduce the need for coercive measures or make their use unnecessary.

  18. Study of coercive measures in prisons and secure psychiatric hospitals: the views of inmates and caregivers.

    Science.gov (United States)

    Runte-Geidel, A; Girela, E; López, A; Ruiz, F; Torres-González, F

    2014-01-01

    The aim of the study was to ascertain the opinions of both inmates and staff of prison establishments about the use of coercive measures justified for clinical reasons for people with mental health problems and about the need to create protocols to regulate the application of these measures. These opinions were gathered in a Qualitative Study with Focus Groups (prison inmates and prison staff) from the Granada Penitentiary Centre and the Alicante Penitentiary Psychiatric Hospital, both in Spain. The results showed that forced medication is the most commonly used coercive measure in these institutions. The inmates did not understand and rejected the use of this measure, above all because they were poorly informed about their illness and the medication required to treat it. The staff however defended the benefits of psychiatric medicine, even when administered without the patient's consent. Both inmates and staff agreed that it would be useful to have a protocol regulating the use of coercive measures. The study has also identified a number of important factors that could help to reduce the need for coercive measures or make their use unnecessary.

  19. Effect of Fe{sub 3}P addition on magnetic properties and microstructure of injection molded iron

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jidong [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); School of Materials Science and Engineering, Xiamen University of Technology, Xiamen 361024 (China); Qin, Mingli, E-mail: qinml@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Tian, Lusha; Zhang, Lin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Khan, Dil Faraz [Department of Physics, University of Science and Technology Bannu, Bannu 28100 (Pakistan); Ding, Xiangying; Qu, Xuanhui [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhang, Houan [School of Materials Science and Engineering, Xiamen University of Technology, Xiamen 361024 (China)

    2016-01-01

    Phosphorus powder was used to improve the performance of iron based alloy products fabricated by metal injection molding. Seven kinds of Fe–xP soft magnetic alloys were formed using carbonyl iron powder and Phosphorus powder as raw materials where x=0–1.2 wt% with 0.2 wt% increment. Samples were sintered in hydrogen atmosphere at the temperature range of 1100–1450 °C for varied times. The effects of sintering temperature and time on the density, microstructure and magnetic properties like magnetic induction, maximum permeability and coercive force of the alloys were examined. The results demonstrated that better magnetic performances of the injection molded Fe–xP alloy is due to increased density of the sintered compacts because of formation of liquid phase at low temperature. For Fe–0.8%P alloy, optimum density 7.84 g/cm{sup 3} (relative density 99%) and magnetic induction (B{sub 6000}) 1.77 T, maximum permeability 17,100 were obtained at sintering temperature 1420 °C while the coercive force was 21 A/m respectively. - Highlights: • High density of injection molded Fe–P alloy was obtained at low temperature. • Sintering temperature has more significant effect on density and microstructure. • Optimum magnetic performance was achieved when the P content was 0.8%.

  20. Synthesis and characterization of highly-magnetic biodegradable poly(D,L-lactide-co-glycolide) nanospheres.

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X.; Kaminski, M. D.; Chen, H.; Torno, M.; Taylor, L.; Rosengart, A. J.; Univ. of Chicago

    2007-05-14

    The objective of this study was to develop high magnetization, biodegradable/biocompatible polymer-coated magnetic nanospheres for biomedical applications. Magnetic spheres were prepared by a modified single oil-in-water emulsion-solvent evaporation method utilizing highly-concentrated hydrophobic magnetite and poly(d,l lactide-co-glycolide) (PLGA). Hydrophobic magnetite prepared using oleic acid exhibited high magnetite concentrations (84 wt.%) and good miscibility with biopolymer solvents to form a stable oily suspension. The oily suspension was then emulsified within an aqueous solution containing poly(vinyl alcohol). After rapid evaporation of the organic solvent, we obtained solid magnetic nanospheres. We characterized these spheres in terms of external morphology, microstructure, size and zeta potential, magnetite content and distribution within the nanospheres, and magnetic properties. The results showed good encapsulation where the magnetite distorted the smooth surface morphology only at the highest magnetite concentrations. The mean diameter was 360-370 nm with polydispersity indices of 0.12-0.20. We obtained high magnetite content (40-60%) and high magnetization (26-40 emu/g). The high magnetization properties were obtained while leaving sufficient polymer to retain drugs making these biodegradable spheres suitable as a potential platform for the design of magnetically-guided drug delivery and other in vivo biomagnetic applications.