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Sample records for stripe magnetic phase

  1. Inhomogeneous Stripe Phase Revisited for Surface Superconductivity

    Science.gov (United States)

    Barzykin, Victor; Gor'kov, Lev P.

    2002-11-01

    We consider 2D surface superconductivity in high magnetic fields parallel to the surface. We demonstrate that the spin-orbit interaction at the surface changes the properties of the inhomogeneous superconducting Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state that develops above fields given by the paramagnetic criterion. Strong spin-orbit interaction significantly broadens the range of existence of the LOFF phase, which takes the form of periodic superconducting stripes running along the field direction on the surface, leading to the anisotropy of its properties. Our results provide a tool for studying surface superconductivity as a function of doping.

  2. Guiding thermomagnetic avalanches with soft magnetic stripes

    Energy Technology Data Exchange (ETDEWEB)

    Vlasko-Vlasov, V. K.; Colauto, F.; Benseman, T.; Rosenmann, D.; Kwok, W. -K.

    2017-12-01

    We demonstrate the potential for manipulating the ultrafast dynamics of thermomagnetic flux avalanches (TMA) in superconducting films with soft magnetic stripes deposited on the film. By tuning the in-plane magnetization of the stripes, we induce lines of strong magnetic potentials for Abrikosov vortices, resulting in guided slow motion of vortices along the stripe edges and preferential bursts of TMA along the stripes. Furthermore, we show that transversely polarized stripes can reduce the TMA size by diverting magnetic flux away from the major trunk of the TMA into interstripe gaps. Our data indicate that TMAs are launched from locations with enhanced vortex entry barrier, where flux accumulation followed by accelerated vortex discharge significantly reduces the threshold of the applied field ramping speed required for the creation of TMAs. Finally, vortex-antivortex annihilation at the moving front of an expanding TMA can account for the enhanced TMA activity in the receding branches of the sample's magnetization cycle and the preferred propagation of TMAs into maximum trapped flux regions.

  3. Static and dynamic magnetic properties of stripe-patterned Fe20Ni80 soft magnetic films

    Science.gov (United States)

    Zhu, Zengtai; Feng, Hongmei; Cheng, Xiaohong; Xie, Hongkang; Liu, Qingfang; Wang, Jianbo

    2018-01-01

    Stripe-patterned soft magnetic Fe20Ni80 films were fabricated on silicon substrate via radio frequency magnetron sputtering technology. The static and dynamic magnetic properties of samples were measured by a vibrating sample magnetometer and vector network analyzer. The vector network analyzer ferromagnetic resonance technique was used to analyze the experimental results, which showed that damping and in-plane uniaxial anisotropy can be tuned significantly for the samples with various stripe widths from 5 to 20 µm. A stripe-shaped anisotropy model was used to analyze the experimental results, which were in accord with the theoretical predictions. Moreover, the variation of damping was investigated in detail.

  4. Magnetic stripes and skyrmions with helicity reversals

    NARCIS (Netherlands)

    Yu, Xiuzhen; Mostovoy, Maxim; Tokunaga, Yusuke; Zhang, Weizhu; Kimoto, Koji; Matsui, Yoshio; Kaneko, Yoshio; Nagaosa, Naoto; Tokura, Yoshinori; MacDonald, Allan H.

    2012-01-01

    It was recently realized that topological spin textures do not merely have mathematical beauty but can also give rise to unique functionalities of magnetic materials. An example is the skyrmion-a nano-sized bundle of noncoplanar spins-that by virtue of its nontrivial topology acts as a flux of

  5. Explanation of the nature of stripe magnetic anomalies without inversions

    Science.gov (United States)

    Melikhov, Vjacheslav; Lygin, Ivan; Sokolova, Tatiana

    2014-05-01

    Several scientists of different branches express doubts on the validity of the Earth's geomagnetic field inversions hypothesis [Vine F.J., Matthews D.H, 1963]. Presently a lot of information allows to link the appearance of stripe magnetic anomalies of both signs with the spreading fracture structure (horizontal segmentation of intrusions and sills, breaks in the strong crust, vertical movements of blocks), remagnetization near the borders of the blocks, hydrothermal activity. Non-inversion mechanism of origin of linear stripe magnetic anomalies in the oceans could be explained as follows. Ascending asthenospheric flows have been enrich with volatile components, become thinner, pressure on the walls of the lithospheric plates grows and part them. When it approaches the surface: - horizontal tensile pressure grows, - lithostatic pressure in the vertical column of rocks decreases, - crust strong upper layer flakes away and begins to move horizontally. It is important that thin magmatic and magnetic layers (further layers) of the newly formed strong upper crust move away from the ridge axis. The structure of such layers forms by horizontal stresses and so consist of the hills and depressions sequences or updiped and downdiped blocks heaped each other. This layer is the main source of the magnetic field and cannot be approximated by a horizontal homogeneous plate as it proved before. In the mid-ocean ridges (MOR) the folding periods of layer depend on its thickness and rigidity and horizontal velocity of spreading. The higher velocity - the longer periods of roughness are and contrary. Same pattern is observed for the stripe magnetic anomalies distribution. The magnetic field of the MOR forms there due to young lava flows which get thermoremanent magnetization according the current direction of geomagnetic field. Partial destruction of the relief, overlaying and creation of the new shapes occur when new magma penetrates the moved magnetic layer. The process entails

  6. Ultrafast charge localization in a stripe-phase nickelate

    Energy Technology Data Exchange (ETDEWEB)

    Coslovich, Giacomo; Huber, Bernhard; Lee, Wei-Sheng; Sasagawa, Takao; Hussain, Zahid; Bechtel, Hans A.; Martin, Michael C.; Shen, Zhi-Xun; W. Schoenlein, Robert; A. Kaindl, Robert

    2013-08-30

    Self-organized electronically-ordered phases are a recurring feature in correlated materials, resulting in e.g. fluctuating charge stripes whose role in high-Tc superconductivity is under debate. However, the relevant cause-effect relations between real-space charge correlations and low-energy excitations remain hidden in time-averaged studies. Here, we reveal ultrafast charge localization and lattice vibrational coupling as dynamical precursors of stripe formation in the model compound La1.75Sr0.25NiO4, using ultrafast and equilibrium mid-infrared spectroscopy. The opening of a pseudogap at a crossover temperature T* far above long-range stripe formation establishes the onset of electronic localization which is accompanied by an enhanced Fano asymmetry of Ni-O stretch vibrations. Ultrafast excitation triggers a sub-picosecond dynamics exposing the synchronous modulation of electron-phonon coupling and charge localization. These results illuminate the role of localization in forming the pseudogap in nickelates, opening a path to understanding this mysterious phase in a broad class of complex oxides.

  7. Distinct Nature of Static and Dynamic Magnetic Stripes in Cuprate Superconductors

    Science.gov (United States)

    Jacobsen, H.; Holm, S. L.; Lǎcǎtuşu, M.-E.; Rømer, A. T.; Bertelsen, M.; Boehm, M.; Toft-Petersen, R.; Grivel, J.-C.; Emery, S. B.; Udby, L.; Wells, B. O.; Lefmann, K.

    2018-01-01

    We present detailed neutron scattering studies of the static and dynamic stripes in an optimally doped high-temperature superconductor, La2 CuO4 +y . We observe that the dynamic stripes do not disperse towards the static stripes in the limit of vanishing energy transfer. Therefore, the dynamic stripes observed in neutron scattering experiments are not the Goldstone modes associated with the broken symmetry of the simultaneously observed static stripes, and the signals originate from different domains in the sample. These observations support real-space electronic phase separation in the crystal, where the static stripes in one phase are pinned versions of the dynamic stripes in the other, having slightly different periods. Our results explain earlier observations of unusual dispersions in underdoped La2 -xSrx CuO4 (x =0.07 ) and La2 -xBax CuO4 (x =0.095 ).

  8. Distinct Nature of Static and Dynamic Magnetic Stripes in Cuprate Superconductors

    DEFF Research Database (Denmark)

    Jacobsen, H.; Holm, S. L.; Lăcătuşu, M. E.

    2018-01-01

    We present detailed neutron scattering studies of the static and dynamic stripes in an optimally doped high-Temperature superconductor, La2CuO4+y. We observe that the dynamic stripes do not disperse towards the static stripes in the limit of vanishing energy transfer. Therefore, the dynamic stripes...... observed in neutron scattering experiments are not the Goldstone modes associated with the broken symmetry of the simultaneously observed static stripes, and the signals originate from different domains in the sample. These observations support real-space electronic phase separation in the crystal, where...... the static stripes in one phase are pinned versions of the dynamic stripes in the other, having slightly different periods. Our results explain earlier observations of unusual dispersions in underdoped La2-xSrxCuO4 (x=0.07) and La2-xBaxCuO4 (x=0.095)....

  9. Emergent Ising degrees of freedom above a double-stripe magnetic ground state

    Science.gov (United States)

    Zhang, Guanghua; Flint, Rebecca

    2017-12-01

    Double-stripe magnetism [Q =(π /2 ,π /2 )] has been proposed as the magnetic ground state for both the iron-telluride and BaTi2Sb2O families of superconductors. Double-stripe order is captured within a J1-J2-J3 Heisenberg model in the regime J3≫J2≫J1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector (π ,π ) . Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one.

  10. Improving striping operations through system optimization - phase 2 : final report.

    Science.gov (United States)

    2016-07-01

    Striping operations generate a significant workload for MoDOT maintenance operations. The requirement for each striping crew : to replenish its stock of paint and other consumable items from a bulk storage facility, along with the necessity to make s...

  11. In-plane magnetic field-induced anisotropy and orientation energy of stripe phases at half-filled high Landau levels

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; MacDonald, A. H.; Smrčka, Ludvík; Girvin, S. M.

    2000-01-01

    Roč. 6, - (2000), s. 43-46 ISSN 1386-9477 R&D Projects: GA ČR GA202/98/0085 Institutional research plan: CEZ:AV0Z1010914 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.878, year: 2000

  12. Magnetic stripes and holes: Complex domain patterns in perforated films with weak perpendicular anisotropy

    Directory of Open Access Journals (Sweden)

    F. Valdés-Bango

    2017-05-01

    Full Text Available Hexagonal antidot arrays have been patterned on weak perpendicular magnetic anisotropy NdCo films by e-beam lithography and lift off. Domain structure has been characterized by Magnetic Force Microscopy at remanence. On a local length scale, of the order of stripe pattern period, domain configuration is controlled by edge effects within the stripe pattern: stripe domains meet the hole boundary at either perpendicular or parallel orientation. On a longer length scale, in-plane magnetostatic effects dominate the system: clear superdomains are observed in the patterned film with average in-plane magnetization along the easy directions of the antidot array, correlated over several antidot array cells.

  13. Magnetic stripes and holes: Complex domain patterns in perforated films with weak perpendicular anisotropy

    Science.gov (United States)

    Valdés-Bango, F.; Vélez, M.; Alvarez-Prado, L. M.; Alameda, J. M.; Martín, J. I.

    2017-05-01

    Hexagonal antidot arrays have been patterned on weak perpendicular magnetic anisotropy NdCo films by e-beam lithography and lift off. Domain structure has been characterized by Magnetic Force Microscopy at remanence. On a local length scale, of the order of stripe pattern period, domain configuration is controlled by edge effects within the stripe pattern: stripe domains meet the hole boundary at either perpendicular or parallel orientation. On a longer length scale, in-plane magnetostatic effects dominate the system: clear superdomains are observed in the patterned film with average in-plane magnetization along the easy directions of the antidot array, correlated over several antidot array cells.

  14. Influence of substrate on the magnetic properties of Ni and permalloy sub-micrometric patterned stripes

    Energy Technology Data Exchange (ETDEWEB)

    Duque, J G S [Nucleo de Fisica, UFS, 49500-000, Itabaiana, SE (Brazil); Rosa, W O [CSIC, Instituto de Ciencia de Materiales, 28049 Madrid (Spain); Nunes, W C [Instituto de Fisica, UFF, Campus da Praia Vermelha, Niteroi, RJ 24.210-340 (Brazil); De Araujo, A E P [Unidade Academica de Garanhuns, UFRPE, CEP 55296-190, Garanhuns-PE (Brazil); Pagliuso, P G; Cescato, L; Knobel, M [Instituto de Fisica ' Gleb Wataghin' , UNICAMP, CP 6165, Campinas SP (Brazil); Socolovsky, L M [UFG, Instituto de Fisica, BR-74001970 Goiania, GO (Brazil); Zysler, R D, E-mail: jduque@fisica.ufs.b [Centro Atomico Bariloche, 8400 San Carlos de Bariloche, RN (Argentina)

    2010-01-20

    The magnetic properties of sub-micrometric magnetic structures of Ni and permalloy (Ni{sub 80}Fe{sub 20}) patterned stripes are studied as functions of temperature. The samples are produced by combining an interferometric lithographic technique with sputtering. At room temperature, ferromagnetic resonance and hysteresis data indicate the existence of an in-plane uniaxial anisotropy in both samples. The NiFe sample has an easy axis along the stripes direction in the entire studied temperature range (2 < T < 300 K). On the other hand, an interesting change in the easy magnetization direction is observed in Ni samples, from parallel to perpendicular to the axis of the stripes, when the temperature is decreased. The results are interpreted in terms of a competition between shape and magnetoelastic anisotropies.

  15. Magnetic anisotropy of two-dimensional nanostructures: Transition-metal triangular stripes

    International Nuclear Information System (INIS)

    Dorantes-Davila, J.; Villasenor-Gonzalez, P.; Pastor, G.M.

    2005-01-01

    The magnetic anisotropy energy (MAE) of one-dimensional stripes having infinite length and triangular lateral structure are investigated in the framework of a self-consistent tight-binding method. One observes discontinuous changes in the easy magnetization direction along the crossover from one to two dimensions. The MAE oscillates as a function of stripe width and depends strongly on the considered transition metal (TM). The MAE of the two-leg ladder is strongly reduced as compared to that of the monoatomic chain and the convergence to the two-dimensional limit is rather slow

  16. Magnetic anisotropy of two-dimensional nanostructures: Transition-metal triangular stripes

    Energy Technology Data Exchange (ETDEWEB)

    Dorantes-Davila, J. [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, San Luis Potosi (Mexico)]. E-mail: jdd@ifisica.uaslp.mx; Villasenor-Gonzalez, P. [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, San Luis Potosi (Mexico); Pastor, G.M. [Laboratoire de Physique Quantique, Centre National de la Recherche Scientifique, Universite Paul Sabatier, Toulouse (France)

    2005-07-15

    The magnetic anisotropy energy (MAE) of one-dimensional stripes having infinite length and triangular lateral structure are investigated in the framework of a self-consistent tight-binding method. One observes discontinuous changes in the easy magnetization direction along the crossover from one to two dimensions. The MAE oscillates as a function of stripe width and depends strongly on the considered transition metal (TM). The MAE of the two-leg ladder is strongly reduced as compared to that of the monoatomic chain and the convergence to the two-dimensional limit is rather slow.

  17. Toward nonlinear magnonics: Intensity-dependent spin-wave switching in insulating side-coupled magnetic stripes

    Science.gov (United States)

    Sadovnikov, A. V.; Odintsov, S. A.; Beginin, E. N.; Sheshukova, S. E.; Sharaevskii, Yu. P.; Nikitov, S. A.

    2017-10-01

    We demonstrate that the nonlinear spin-wave transport in two laterally parallel magnetic stripes exhibit the intensity-dependent power exchange between the adjacent spin-wave channels. By the means of Brillouin light scattering technique, we investigate collective nonlinear spin-wave dynamics in the presence of magnetodipolar coupling. The nonlinear intensity-dependent effect reveals itself in the spin-wave mode transformation and differential nonlinear spin-wave phase shift in each adjacent magnetic stripe. The proposed analytical theory, based on the coupled Ginzburg-Landau equations, predicts the geometry design involving the reduction of power requirement to the all-magnonic switching. A very good agreement between calculation and experiment was found. In addition, a micromagnetic and finite-element approach has been independently used to study the nonlinear behavior of spin waves in adjacent stripes and the nonlinear transformation of spatial profiles of spin-wave modes. Our results show that the proposed spin-wave coupling mechanism provides the basis for nonlinear magnonic circuits and opens the perspectives for all-magnonic computing architecture.

  18. Zero-bias-field microwave dynamic magnetic properties in trapezoidal ferromagnetic stripe

    International Nuclear Information System (INIS)

    Bi, Mei; Wang, Xin; Lu, Haipeng; Zhang, Li; Deng, Longjiang; Xie, Jianliang

    2016-01-01

    Dynamic magnetization response of the axially magnetized ferromagnetic stripe with trapezoidal cross section has been studied. The stripe with beveled edges exhibits multiple resonant peaks modes under an in-plane microwave excitation compared with the single resonant of vertical edge surfaces. The complexity of the observed response is attributed to the spatially nonuniform equilibrium spin distribution at the stripe edges. Micromagnetic simulations identify spin waves as spatially localized mode at the modified edges. This one is also described by effective pinning boundary conditions taking into account finite-size effects, which is related to the exchange interaction, surface anisotropy and dipole–dipole interaction. These results provide detailed insights into the nonlinear spin dynamics of microstructures influenced by the edge properties. - Highlights: • Series of FeCoNbBCu stripes with trapezoidal cross section have been fabricated. • The stripe with beveled edges exhibits multiple resonant peaks modes. • Micromagnetic simulations identify the spatially localized mode. • The effective pinning boundary conditions taking into account finite-size effects.

  19. Superconductivity from magnetic fluctuations in FeTe{sub 1-x}Se{sub x}-feedback of double stripe magnetism on itinerant spin excitations

    Energy Technology Data Exchange (ETDEWEB)

    Mardani, Masoud; Moessner, Roderich [Max Planck Institute for the Physics of Complex Systems, Dresden (Germany); Knolle, Johannes [TCM Group, Cavendish Laboratory, University of Cambridge (United Kingdom); Eremin, Ilya [Institute for Theoretical Physics III, Ruhr-Universitaet Bochum (Germany)

    2015-07-01

    Iron-chalcogenide superconductors exhibit an unusual double stripe antiferromagnetic parent phase with ordering vector Q{sub AF} = (π/2,π/2) (in the one iron unit cell). In addition, magnetic excitations in optimally doped systems are peaked at momenta Q{sub SF} = (π,0)/(0,π), which is in contrast to most other families of iron-based superconductors. There, both the magnetic order of the parent compounds and the magnetic fluctuations in the superconducting state have the same momentum Q{sub SF}, which is taken as a strong argument in favor of spin-fluctuation induced superconductivity. Here, we model iron-chalcogenides as a system of itinerant electrons coupled to localized electrons responsible for the double stripe magnetism. We study the feedback of this unusual magnetic order on the itinerant spin excitations at Q{sub SF} and show that they increase with decreasing magnetism. We make connection to recent INS experiments and reproduce qualitatively the behavior of magnetic excitations in FeTe{sub 1-x}Se{sub x} from x=0 towards x=0.4.

  20. Magnetostatic Green's functions for the description of spin waves in finite rectangular magnetic dots and stripes

    International Nuclear Information System (INIS)

    Guslienko, Konstantin Y.; Slavin, Andrei N.

    2011-01-01

    We present derivation of the magnetostatic Green's functions used in calculations of spin-wave spectra of finite-size non-ellipsoidal (rectangular) magnetic elements. The elements (dots) are assumed to be single domain particles having uniform static magnetization. We consider the case of flat dots, when the in-plane dot size is much larger than the dot height (film thickness), and assume the uniform distribution of the variable magnetization along the dot height. The limiting cases of magnetic waveguides with rectangular cross-section and thin magnetic stripes are also considered. The developed method of tensorial Green's functions is used to solve the Maxwell equations in the magnetostatic limit, and to represent the Landau-Lifshitz equation of motion for the magnetization of a magnetic element in a closed integro-differential form. - Highlights: → The Green's functions method is used to solve the magnetostatic equations. → Explicit Green's functions are written for thin magnetic dots and stripes. → Spin-wave frequencies for finite rectangular magnetic elements are calculated.

  1. Magnetic stripe domains of [Pt/Co/Cu]10 multilayer near spin reorientation transition

    Directory of Open Access Journals (Sweden)

    L. Sun

    2016-05-01

    Full Text Available The dependence of magnetic anisotropy, magnetic domain patterns and magnetization reversal processes in [Pt/Co(tCo/Cu]10 film stack epitaxied on Cu (111 substrate have been studied as a function of the Co layer thickness tCo, by magneto-optic polar Kerr magnetometry and microscopy. We find the film undergoes spin reorientation transition from out-of-plane to in-plane as tCo increases. The SRT thickness is verified by Rotating-field Magneto-Optic Kerr effect method. The film exhibits the stripe domain structures at remanence with the width decreasing while tCo approaches SRT. As demonstrated by the first order reversal curve measurement, the magnetization reversal process encompasses irreversible domain nucleation, domain annihilation at large field and reversible domain switching near remanence.

  2. Striped Phase of 3-Hexylthiophene Self-Assembled Monolayers on Au(1 11) Formed by Vapor Phase Deposition.

    Science.gov (United States)

    Kim, Youngwoo; Kang, Hungu; Tsunoi, Azuho; Hayashi, Tomohiro; Hara, Masahiko; Noh, Jaegeun

    2016-03-01

    The formation and surface structure of 3-hexylthiophene (HTP) self-assembled monolayers (SAMs) on Au(111) prepared by solution and ambient-pressure vapor deposition at room temperature (RT) for 24 h were examined by means of scanning tunneling microscopy (STM) and cyclic voltammetry (CV). STM imaging revealed that HTP SAMs formed by solution deposition have a disordered phase, whereas those formed by vapor deposition exhibit a striped phase with a unidirectional orientation. The distance between the rows in the striped phase was measured to be 1.3 ± 0.1 nm, and the hexyl molecular backbones of HTP in the SAMs on Au(111) are oriented parallel to the Au(111) surface with the head-to-head orientation. From this STM observation, we suggest that the formation of this striped phase in HTP SAMs prepared by vapor deposition were mainly driven by the optimization of van der Waals interactions between the hexyl chains on the surface. CV measurements also demonstrated that HTP SAMs show a high blocking efficiency for electron transfer reactions between electrolytes and the gold electrode, suggesting the formation of SAMs on Au(111) from the vapor phase. Our results obtained here will be very useful for understanding the formation and structure of HTP SAMs on Au(111) surfaces and how they are influenced by deposition method.

  3. Stripe segregation and magnetic coupling in the nickelate La 5/3Sr1/3NiO4

    KAUST Repository

    Schwingenschlögl, Udo

    2009-03-02

    We investigate the consequences of the stripe formation in the nickelate La5/3Sr1/3NiO4 for the details of its crystal structure and electronic states. Our data are based on numerical simulations within density functional theory (DFT) and the generalized gradient approximation (GGA). The on-site Coulomb interaction is included in terms of the LDA+U scheme. Structure optimization of preliminary experimental data indicates a strong interaction between the structural and electronic degrees of freedom. In particular, we find a segregation of the diagonal filled stripes induced by a delicate interplay with the magnetic coupling. Beyond the cooperative effect of stripe segregation and spin order, distinct octahedral distortions are essential for the formation of an insulating state. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Expansion of the South China Sea basin: Constraints from magnetic anomaly stripes, sea floor topography, satellite gravity and submarine geothermics

    Directory of Open Access Journals (Sweden)

    Xuezhong Yu

    2017-01-01

    Full Text Available The widely distributed E–W-trending magnetic anomaly stripes in the central basin and the N–E-trending magnetic anomaly stripes in the southwest sub-basin provide the most important evidence for Neogene expansion of the South China Sea. The expansion mechanism remains, however, controversial because of the lack of direct drilling data, non-systematic marine magnetic survey data, and irregular magnetic anomaly stripes with two obvious directions. For example, researchers have inferred different ages and episodes of expansion for the central basin and southwest sub-basin. Major controversy centers on the order of basinal expansion and the mechanism of expansion for the entire South China Sea basin. This study attempts to constrain these problems from a comprehensive analysis of the seafloor topography, magnetic anomaly stripes, regional aeromagnetic data, satellite gravity, and submarine geothermics. The mapped seafloor terrain shows that the central basin is a north-south rectangle that is relatively shallow with many seamounts, whereas the southwest sub-basin is wide in northeast, gradually narrows to the southwest, and is relatively deeper with fewer seamounts. Many magnetic anomaly stripes are present in the central basin with variable dimensions and directions that are dominantly EW-trending, followed by the NE-, NW- and NS-trending. Conversely such stripes are few in the southwest sub-basin and mainly NE-trending. Regional magnetic data suggest that the NW-trending Ailaoshan-Red River fault extends into the South China Sea, links with the central fault zone in the South China Sea, which extends further southward to Reed Tablemount. Satellite gravity data show that both the central basin and southwest sub-basin are composed of oceanic crust. The Changlong seamount is particularly visible in the southwest sub-basin and extends eastward to the Zhenbei seamount. Also a low gravity anomaly zone coincides with the central fault zone in the sub

  5. Effects of 'Stripes' on the magnetic excitation spectra of La sub 1 sub . sub 4 sub 8 Nd sub 0 sub . sub 4 Sr sub 0 sub . sub 1 sub 2 CuO sub 4

    CERN Document Server

    Ito, M; Iikubo, S; Soda, M; Sato, M; Kobayashi, A; Kakurai, K

    2003-01-01

    The wave vector (q)- and energy (omega)-dependent magnetic excitation spectra chi''(q, omega), have been studied in the temperature (T) range of 10K <= T < 150K on single crystals of La sub 1 sub . sub 4 sub 8 Nd sub 0 sub . sub 4 Sr sub 0 sub . sub 1 sub 2 CuO sub 4 , which has the static 'stripe' order in the low-temperature phase. The incommensurability delta of the peak of chi''(q, omega) found by the q-scans and the peak width DELTA q exhibit characteristic T dependences. The observed profiles show a clear incommensurate structure even at rather high temperature. The results indicate the effects of the slowly fluctuating stripes' exist not only in the low-temperature tetragonal (LTT) phase but also in the orthorhombic phase (LTO1) of the present system. (author)

  6. Magnetic resonance of phase transitions

    CERN Document Server

    Owens, Frank J; Farach, Horacio A

    1979-01-01

    Magnetic Resonance of Phase Transitions shows how the effects of phase transitions are manifested in the magnetic resonance data. The book discusses the basic concepts of structural phase and magnetic resonance; various types of magnetic resonances and their underlying principles; and the radiofrequency methods of nuclear magnetic resonance. The text also describes quadrupole methods; the microwave technique of electron spin resonance; and the Mössbauer effect. Phase transitions in various systems such as fluids, liquid crystals, and crystals, including paramagnets and ferroelectrics, are also

  7. Observation of Anisotropic Stripe Phases at Even Denominator Fillings ν = 3/2, 5/2 and 7/2 in a Narrow AlAs Quantum Well

    Science.gov (United States)

    Hossain, Md. Shafayat; Mueed, M. A.; Ma, Meng K.; Chung, Yoon Jang; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.

    Anisotropic stripe phases are observed at high-index, half-filled Landau levels in high quality 2D carrier systems with high mobility. Here, we report the observation of such phases at filling factors ν = 3/2, 5/2 and 7/2 under tilted magnetic field in a narrow (56.6 Å-wide) AlAs quantum well where electrons occupy an out of plane (Z) valley with a density of 3x1011 cm-2 and a modest mobility of about 7 m2/Vs. At a critical tilting angle, when ν = 3/2 undergoes a transition from the N = 0 (Z0 ↑) to the N = 1 (Z1 ↓) Landau level, a resistance spike emerges, indicating a ferromagnetic transition. For higher tilting angles, the ground state at ν = 3/2 develops into a stripe phase with the resistance along B|| exhibiting a minimum whose value is about 6 times smaller (in a Hall-bar geometry) than the resistance perpendicular to B|| which shows a maximum. Similar phenomenon happens for ν = 5/2 and 7/2, when they undergo transitions from Z0 ↑ to Z2 ↓ and Z0 ↑ to Z3 ↓, respectively, at yet higher tilt angles. Furthermore, the anisotropic phases appear to be quite robust as they persist even at 1.8 K. Work supported by the NSF (Grants DMR-1305691, ECCS-1508925, and MRSEC DMR-1420541), the DOE Basic Energy Sciences (Grant DE-FG02-00-ER45841), the Gordon and Betty Moore Foundation (Grant GBMF4420), and the Keck Foundation.

  8. Magnetic Anisotropy and Magnetic Phase Diagram in the Ferromagnetic States of La1-x SrxMnO3 for 0.1 < x <0.2

    Science.gov (United States)

    Kotani, Atsuhiro; Nakajima, Hiroshi; Harada, Ken; Ishii, Yui; Mori, Shigeo

    Magnetic textures such as magnetic vortices, magnetic bubbles and magnetic stripe domains have been found in magnetic materials such as helical magnets without the inversion symmetry by neutron scattering and Lorentz microscopy (LM) observation. On the contrary, it has been reported that compounds having the inversion symmetry such as La0.875Sr0.125MnO3 exhibited magnetic textures in the ferromagnetic phase. Thus, we investigated formation processes of magnetic textures as functions of temperature and strength of magnetic fields by using LM and small-angle electron diffraction experiments. In-situ LM observations revealed that magnetic bubbles are formed by applying magnetic field perpendicular to thin plate having periodic magnetic stripe domains in the ferromagnetic metallic phase of La1-x SrxMnO3for 0.1 < x <0.2. In addition, we constructed phase diagram of magnetic textures such as magnetic bubbles. It is revealed that magnetic bubbles in La1-x SrxMnO3 should formed by high magnetocrystalline anisotropy in the orthorhombic and monoclinic structures.

  9. Nanoscale control of stripe-ordered magnetic domain walls by vertical spin transfer torque in La0.67Sr0.33MnO3 film

    Science.gov (United States)

    Wang, Jing; Wu, Shizhe; Ma, Ji; Xie, Lishan; Wang, Chuanshou; Malik, Iftikhar Ahmed; Zhang, Yuelin; Xia, Ke; Nan, Ce-Wen; Zhang, Jinxing

    2018-02-01

    Stripe-ordered domains with perpendicular magnetic anisotropy have been intensively investigated due to their potential applications in high-density magnetic data-storage devices. However, the conventional control methods (e.g., epitaxial strain, local heating, magnetic field, and magnetoelectric effect) of the stripe-ordered domain walls either cannot meet the demands for miniaturization and low power consumption of spintronic devices or require high strength of the electric field due to the small value of the magnetoelectric effect at room temperature. Here, a domain-wall resistive effect of 0.1% was clarified in La0.67Sr0.33MnO3 thin films between the configurations of current in the plane and perpendicular to the plane of walls. Furthermore, a reversible nanoscale control of the domain-wall re-orientation by vertical spin transfer torque across the probe/film interface was achieved, where a probe voltage of 0.1 V was applied on a manganite-based capacitor. We also demonstrated that the stripe-ordered magnetic domain-wall re-orientation strongly depends on the AC frequency of the scanning probe voltage which was applied on the capacitor.

  10. Statistical mechanics of magnetic excitations from spin waves to stripes and checkerboards

    CERN Document Server

    Rastelli, Enrico

    2013-01-01

    The aim of this advanced textbook is to provide the reader with a comprehensive explanation of the ground state configurations, the spin wave excitations and the equilibrium properties of spin lattices described by the Ising-Heisenberg Hamiltonians in the presence of short (exchange) and long range (dipole) interactions.The arguments are presented in such detail so as to enable advanced undergraduate and graduate students to cross the threshold of active research in magnetism by using both analytic calculations and Monte Carlo simulations.Recent results about unorthodox spin configurations suc

  11. Magnetic dipole self-organization of charge carriers in high-temperature superconductors and kinetics of phase transformation

    CERN Document Server

    Voronov, A V; Shuvalov, V V

    2001-01-01

    The phenomenological model, describing the magnetic dipole self-organization of charge carriers (formation of so-called stripe-structures and energy gap in the states spectrum), is designed for interpreting the data on the nonstationary nonlinear spectroscopy of the high-temperature superconductors. It is shown that after fast heating of the superconducting sample the kinetics of the subsequent phase transition depends on the initial temperature T. The destruction of the stripe-structures at low overheating T* < T < T sub m approx = (1.4-1.5)T*, whereby T sub c and T* approx = T sub c are the temperatures of transition into the superconducting state and formation of the stripe-structures occurs slowly (the times above 10 sup - sup 9 s) in spite of practically instantaneous disappearance of the superconductivity

  12. Tuning the magnetic properties of stripe domain structured CoFeB films using stack structure with spacer layer thickness dependent interlayer coupling

    Science.gov (United States)

    Das, Camelia; Alagarsamy, Perumal

    2018-02-01

    We report a novel approach for tuning the magnetic properties of stripe domain structured amorphous Co40Fe40B20 (CoFeB) films by using stack structured [CoFeB (100 nm)/Ta (z = 0-1.5 nm)]n= 0-4/CoFeB (100 nm) films with spacer layer thickness dependent interlayer coupling. All the as-deposited films deposited directly on thermally oxidized Si substrate at ambient temperature exhibit amorphous structure. Single-layer CoFeB (x = 100-300 nm) films display transcritical loops with high coercivity (HC > 4 kA/m) and large applied field required for magnetization saturation (HS > 40 kA/m) due to the formation of magnetic stripe domains induced by the stress quenched in during the preparation of the films at a high deposition rate to form amorphous structure. With increasing n, the number of CoFeB layers in stack structure increases providing an enhanced interlayer coupling and a better flux closure, which leads to a substantial drop in HC (∼1.8 kA/m) and changes the loop shape away from transcritical into soft magnetic type with reduced HS (∼10 kA/m) and increased remanence ratio (>75%). However, the improvement in magnetic properties strongly depends on the values of n and z. Temperature dependent M-H loops reveal a competition between interlayer coupling and interfacial strain, which provides unusual variation of HC(T), i.e., minimum in HC(T) vs T curve, depending on z and n. The observed results are explained on the basis of stress dependent stripe domains in single layer films and number of CoFeB layers and spacer layer thickness dependent interlayer coupling in stack structured films. It is revealed that the fabrication of stack of thick CoFeB films having stripe domains and separated by optimum z is an alternative approach to improve the magnetic properties of thick CoFeB films.

  13. Magnetic in-tube solid phase microextraction.

    Science.gov (United States)

    Moliner-Martínez, Y; Prima-Garcia, Helena; Ribera, Antonio; Coronado, Eugenio; Campíns-Falcó, P

    2012-08-21

    We report a new in-tube solid phase microextraction approach named magnetic in-tube solid phase microextraction, magnetic-IT-SPME. Magnetic-IT-SPME has been developed, taking advantage of magnetic microfluidic principles with the aim to improve extraction efficiency of IT-SPME systems. First, a magnetic hybrid material formed by Fe(3)O(4) nanoparticles supported on SiO(2) was synthesized and immobilized in the surface of a bared fused silica capillary column to obtain a magnetic adsorbent extraction phase. The capillary column was placed inside a magnetic coil that allowed the application of a variable magnetic field. Acetylsalicylic acid, acetaminophen, atenolol, diclofenac, and ibuprofen were tested as target analytes. The application of a controlled magnetic field resulted in quantitative extraction efficiencies of the target analytes between 70 and 100%. These results demonstrated that magnetic forces solve the low extraction efficiency (10-30%) of IT-SPME systems, which is one of their main drawbacks.

  14. Cross-sectional anatomy, computed tomography and magnetic resonance imaging of the head of common dolphin (Delphinus delphis) and striped dolphin (Stenella coeruleoalba).

    Science.gov (United States)

    Alonso-Farré, J M; Gonzalo-Orden, M; Barreiro-Vázquez, J D; Barreiro-Lois, A; André, M; Morell, M; Llarena-Reino, M; Monreal-Pawlowsky, T; Degollada, E

    2015-02-01

    Computed tomography (CT) and low-field magnetic resonance imaging (MRI) were used to scan seven by-caught dolphin cadavers, belonging to two species: four common dolphins (Delphinus delphis) and three striped dolphins (Stenella coeruleoalba). CT and MRI were obtained with the animals in ventral recumbency. After the imaging procedures, six dolphins were frozen at -20°C and sliced in the same position they were examined. Not only CT and MRI scans, but also cross sections of the heads were obtained in three body planes: transverse (slices of 1 cm thickness) in three dolphins, sagittal (5 cm thickness) in two dolphins and dorsal (5 cm thickness) in two dolphins. Relevant anatomical structures were identified and labelled on each cross section, obtaining a comprehensive bi-dimensional topographical anatomy guide of the main features of the common and the striped dolphin head. Furthermore, the anatomical cross sections were compared with their corresponding CT and MRI images, allowing an imaging identification of most of the anatomical features. CT scans produced an excellent definition of the bony and air-filled structures, while MRI allowed us to successfully identify most of the soft tissue structures in the dolphin's head. This paper provides a detailed anatomical description of the head structures of common and striped dolphins and compares anatomical cross sections with CT and MRI scans, becoming a reference guide for the interpretation of imaging studies. © 2014 Blackwell Verlag GmbH.

  15. Magnetic phase diagram of a nanocone

    International Nuclear Information System (INIS)

    Suarez, O; Vargas, P; Escrig, J; Landeros, P; Albir, D; Laroze, D

    2008-01-01

    In this work we analyze the magnetic properties of truncated conical nanoparticles. Based on the continuous magnetic model we find expressions for the total energy in three different magnetic configurations. Finally, we calculate the magnetic phase diagram as function of the geometrical parameters.

  16. Magnetic phase diagram of a nanocone

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, O; Vargas, P [Departamento de Fisica, Universidad Tecnica Federico Santa MarIa, P. O. Box 110-V, Valparaiso (Chile); Escrig, J; Landeros, P; Albir, D [Universidad de Santiago de Chile, Depatamento de Fisica, Casilla 307, Correo 2, Santiago (Chile); Laroze, D [Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, P. O. Box 4059, Valparaiso (Chile)], E-mail: omar.suarez@postgrado.usm.cl

    2008-11-01

    In this work we analyze the magnetic properties of truncated conical nanoparticles. Based on the continuous magnetic model we find expressions for the total energy in three different magnetic configurations. Finally, we calculate the magnetic phase diagram as function of the geometrical parameters.

  17. Magnetic phase shift reconstruction for uniformly magnetized nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Akhtari-Zavareh, Azadeh [Department of Physics, Simon Fraser University, Burnaby, British Columbia (Canada); De Graef, Marc [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA (United States); Kavanagh, Karen L. [Department of Physics, Simon Fraser University, Burnaby, British Columbia (Canada)

    2017-01-15

    A new analytical model is developed for the magnetic phase shift of uniformly magnetized nanowires with ideal cylindrical geometry. The model is applied to experimental data from off-axis electron holography measurements of the phase shift of CoFeB nanowires, and the saturation induction of a selected wire, as well as its radius, aspect ratio, position and orientation, is determined by fitting the model parameters. The saturation induction value of 1.7 T of the CoFeB nanowire is found to be similar, to be within the measurement error, to values reported in the literature. - Highlights: • We describe a mathematical model for the magnetic phase shift of a cylindrical nanowire. • We discuss electron holography experiments on magnetic nanowires. • We obtain an accurate fit of the measured magnetic phase shift profile. • We extract the magnetic induction of the nanowire from the phase shift model. • The magnetic induction of 1.7 T agrees well with literature results.

  18. Magnetically Actuated Seal, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — FTT proposes development of a magnetically actuated dynamic seal. Dynamic seals are used throughout the turbopump in high-performance, pump-fed, liquid rocket...

  19. Magnetically Actuated Seal, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — FTT proposes development of a magnetically actuated dynamic seal. Dynamic seals are used throughout the turbopump in high-performance, pump-fed, liquid rocket...

  20. The Stripe State in Cupratesa

    Directory of Open Access Journals (Sweden)

    Lee T.-K.

    2012-03-01

    Full Text Available Since the discovery of high temperature superconductors (HTS two decades ago, many anomalous properties have been reported. One of the most interesting properties is the possible existence of the stripe state consisting of one dimensional charge-density modulation coupled with some kind of spin ordering. X-ray and neutron scattering experiments and recently high resolution scanning tunneling microscopy have reported direct evidences of such a structure. In particular it has found in the La-Sr-Cu-O (LSCO family the existence of the half-doped stripe with average of half a hole in one charge modulation period below and about 1/8 hole density. These results have fueled the idea about the presence of these charge or spin density wave states competing with the superconducting phase in underdoped HTS. They may even contribute to the pairing mechanism. In this talk, we will demonstrate that the presence of these stripes is actually a natural consequence of the strongly interacting t-J model by using a variational approach which provides a good enough accuracy to address the subtle result. Furthermore we show that half-doped stripes could be stabilized in hole-doped systems if we assume a simple electron-phonon interaction to renormalize the electron mass. However we have not found any evidence to support half-doped stripes in electron-doped systems.

  1. Evaluation of rumble stripes.

    Science.gov (United States)

    2010-01-01

    The objective of this study were to: a) monitor the initial installations of rumble stripes and b) evaluate the results of rumble stripe installations. : Ten rural, two-lane road locations were selected by the Kentucky Transportation Cabinet across t...

  2. Exploding Stars and Stripes

    Science.gov (United States)

    2011-03-01

    The discovery of a pattern of X-ray "stripes" in the remains of an exploded star may provide the first direct evidence that a cosmic event can accelerate particles to energies a hundred times higher than achieved by the most powerful particle accelerator on Earth. This result comes from a very long observation of the Tycho supernova remnant with NASA's Chandra X-ray Observatory. It could explain how some of the extremely energetic particles bombarding the Earth, called cosmic rays, are produced. "We've seen lots of intriguing structures in supernova remnants, but we've never seen stripes before," said Kristoffer Eriksen, a postdoctoral researcher at Rutgers University who led the study. "This made us think very hard about what's happening in the blast wave of this powerful explosion." This latest study from Chandra provides support for a theory about how magnetic fields can be dramatically amplified in such blast waves. In this theory, the magnetic fields become highly tangled and the motions of the particles very turbulent near the expanding supernova shock wave at the front edge of the supernova remnant. High-energy charged particles can bounce back and forth across the shock wave repeatedly, gaining energy with each crossing. Theoretical models of the motion of the most energetic particles -- which are mostly protons -- are predicted to leave a messy network of holes and dense walls corresponding to weak and strong regions of magnetic fields, respectively. The X-ray stripes discovered by the Chandra researchers are thought to be regions where the turbulence is greater and the magnetic fields more tangled than surrounding areas, and may be the walls predicted by the theory. Electrons become trapped in these regions and emit X-rays as they spiral around the magnetic field lines. However, the regular and almost periodic pattern of the X-ray stripes was not predicted by the theory. "It was a big surprise to find such a neatly arranged set of stripes," said co

  3. Two phase cooling for superconducting magnets

    International Nuclear Information System (INIS)

    Eberhard, P.H.; Gibson, G.A.; Green, M.A.; Ross, R.R.; Smits, R.G.; Taylor, J.D.; Watt, R.D.

    1986-01-01

    Comments on the use of two phase helium in a closed circuit tubular cooling system and some results obtained with the TPC superconducting magnet are given. Theoretical arguments and experimental evidence are given against a previously suggested method to determine helium two phase flow regimes. Two methods to reduce pressure in the magnet cooling tubes during quenches are discussed; (1) lowering the density of helium in the magnet cooling tubes and (2) proper location of pressure relief valves. Some techniques used to protect the refrigerator from too much cold return gas are also mentioned. 10 refs., 1 fig., 5 tabs

  4. Striped states in a many-body system of tilted dipoles

    Science.gov (United States)

    Wenzel, Matthias; Böttcher, Fabian; Langen, Tim; Ferrier-Barbut, Igor; Pfau, Tilman

    2017-11-01

    We study theoretically and experimentally the behavior of a strongly confined dipolar Bose-Einstein condensate in the regime of quantum-mechanical stabilization by beyond-mean-field effects. Theoretically, we demonstrate that self-organized "striped" ground states are predicted in the framework of the extended Gross-Pitaevskii theory. Experimentally, by tilting the magnetic dipoles we show that self-organized striped states can be generated, likely in their metastable state. Matter-wave interference experiments with multiple stripes show that there is no long-range off-diagonal order (global phase coherence). We outline a parameter range where global phase coherence could be established, thus paving the way towards the observation of supersolid states in this system.

  5. Magnetic phase diagrams of UNiGe

    International Nuclear Information System (INIS)

    Nakotte, H.; Torikachvili, M.S.; Lacerda, A.H.

    1998-01-01

    UNiGe undergoes two magnetic transitions in zero field. Here, the magnetic diagrams of UNiGe for B parallel b and B parallel c are reported. We performed temperature scans of the magnetization in static magnetic fields up to 19.5 T applied along the b and c axes. For both orientations three magnetic phases have been identified in the B-T diagrams. We confirmed the previously reported phase boundaries for B parallel c, and in addition we determined the location of the phase boundaries for B parallel b. We discuss a possible relationship of the two zero-field antiferromagnetic phases (commensurate: T<42 K; incommensurate: 42 K< T<50 K) and the field-induced phase, which at low temperatures, occurs between 18 and 25 T or 4 and 10 T for B parallel b or B parallel c, respectively. Finally, we discuss the field dependence of the electronic contribution γ to the specific heat for B parallel c up to 17.5 T, and we find that its field dependence is similar to the one found in more itinerant uranium compounds. (orig.)

  6. Magnetic phase diagrams of UNiGe

    International Nuclear Information System (INIS)

    Nakotte, H.; Hagmusa, I.H.; Klaasse, J.C.P.; Hagmusa, I.H.; Klaasse, J.C.P.

    1997-01-01

    UNiGe undergoes two magnetic transitions in zero field. Here, the magnetic diagrams of UNiGe for B parallel b and B parallel c are reported. We performed temperatures scans of the magnetization in static magnetic fields up to 19.5T applied along the b and c axes. For both orientations 3 magnetic phases have been identified in the B-T diagrams. We confirmed the previously reported phase boundaries for B parallel c, and in addition we determined the location of the phase boundaries for B parallel b. We discuss a possible relationship of the two zero-field antiferromagnetic phases (commensurate: T<42K; incommensurate: 42K< T<50K) and the field-induced phase, which, at low temperatures, occurs between 18 and 25T or 4 and 10T for B parallel b or B parallel c, respectively. Finally, we discuss the field dependence of the electronic contribution γ to the specific heat for B parallel c up to 17.5T, and we find that its field dependence is similar to the one found in more itinerant uranium compounds

  7. Lighting up superconducting stripes

    Science.gov (United States)

    Ergeçen, Emre; Gedik, Nuh

    2018-02-01

    Cuprate superconductors display a plethora of complex phases as a function of temperature and carrier concentration, the understanding of which could provide clues into the mechanism of superconductivity. For example, when about one-eighth of the conduction electrons are removed from the copper oxygen planes in cuprates such as La2‑xBaxCuO4 (LBCO), the doped holes (missing electrons) organize into one-dimensional stripes (1). The bulk superconducting transition temperature (Tc) is greatly reduced, and just above Tc, electrical transport perpendicular to the planes (along the c axis) becomes resistive, but parallel to the copper oxygen planes, resistivity remains zero for a range of temperatures (2). It was proposed a decade ago (3) that this anisotropic behavior is caused by pair density waves (PDWs); superconducting Cooper pairs exist along the stripes within the planes but cannot tunnel to the adjacent layers. On page 575 of this issue, Rajasekaran et al. (4) now report detection of this state in LBCO using nonlinear reflection of high-intensity terahertz (THz) light.

  8. Nonadiabatic Berry phase in nanocrystalline magnets

    Directory of Open Access Journals (Sweden)

    R. Skomski

    2017-05-01

    Full Text Available It is investigated how a Berry phase is created in polycrystalline nanomagnets and how the phase translates into an emergent magnetic field and into a topological Hall-effect contribution. The analysis starts directly from the spin of the conduction electrons and does not involve any adiabatic Hamiltonian. Completely random spin alignment in the nanocrystallites does not lead to a nonzero emergent field, but a modulation of the local magnetization does. As an explicit example, we consider a wire with a modulated cone angle.

  9. Topological phases and phase transitions in magnets and ice

    NARCIS (Netherlands)

    Keesman, R.

    2017-01-01

    The main focus of this Thesis is the behaviour of two-dimensional materials, namely (anti)-ferromagnetic materials in the first two chapters, which show topological phases, and energetic square ice in the third and fourth chapter. The magnetic materials are of interest in part due to foreseen

  10. Evaluation of rumble stripes on low-volume rural roads in Iowa--phase I : final report, July 2009, tech transfer summary.

    Science.gov (United States)

    2009-07-01

    Objectives : Determine if rumble stripes can be used as a strategy to combat roadway departures and reduce the number of run-off-road (ROR) crashes. : Install edge line rumble stripes along the lane edge at a narrow width to avoid intruding o...

  11. Probing optically silent superfluid stripes in cuprates

    Science.gov (United States)

    Rajasekaran, S.; Okamoto, J.; Mathey, L.; Fechner, M.; Thampy, V.; Gu, G. D.; Cavalleri, A.

    2018-02-01

    In many theoretical models of high-temperature superconductors, remnants of superconductivity persist to temperatures higher than the transition temperature, TC. Rajasekaran et al. used nonlinear terahertz spectroscopy to probe this region of the phase diagram of a cuprate superconductor that is well known for a stripe phase that appears for certain doping levels (see the Perspective by Ergeçen and Gedik). For a sample deep in the stripe phase, a large nonlinear signal persisted from the superconducting region up to temperatures much higher than TC. The findings suggest the formation of a peculiar spatially modulated superconducting state called the pair-density wave.

  12. Stripe and line textures in the B2 phase of bent-shape molecules in samples with polar surface anchoring

    Czech Academy of Sciences Publication Activity Database

    Lejček, Lubor; Novotná, Vladimíra; Glogarová, Milada

    2011-01-01

    Roč. 84, č. 6 (2011), 061701/1-061701/12 ISSN 1539-3755 R&D Projects: GA ČR(CZ) GAP204/11/0723 Institutional research plan: CEZ:AV0Z10100520 Keywords : liquid crystals Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.255, year: 2011

  13. Magnetic transitions and phases in random-anisotropy magnets

    International Nuclear Information System (INIS)

    Sellmyer, D.J.; Nafis, S.; O'Shea, M.J.

    1988-01-01

    The generality and universality of the Ising spin-glass-like phase transitions observed in several rare-earth, random-anisotropy magnets are discussed. Some uncertainties and practical problems in determining critical exponents are considered, and a comparison is made to insulating spin glasses and crystalline spin glasses where an apparent anisotropy-induced crossover from Heisenberg to Ising-like behavior is seen. The observation of a reentrant transition in a weak anisotropy system and its correlation with the theory of Chudnovsky, Saslow, and Serota [Phys. Rev. B 33, 251 (1986)] for the correlated spin glass is discussed

  14. Magnetic transitions and phases in random-anisotropy magnets

    Science.gov (United States)

    Sellmyer, D. J.; Nafis, S.; O'Shea, M. J.

    1988-04-01

    The generality and universality of the Ising spin-glass-like phase transitions observed in several rare-earth, random-anisotropy magnets are discussed. Some uncertainties and practical problems in determining critical exponents are considered, and a comparison is made to insulating spin glasses and crystalline spin glasses where an apparent anisotropy-induced crossover from Heisenberg to Ising-like behavior is seen. The observation of a reentrant transition in a weak anisotropy system and its correlation with the theory of Chudnovsky, Saslow, and Serota [Phys. Rev. B 33, 251 (1986)] for the correlated spin glass is discussed.

  15. Magnetically ordered phase near transition to Bose-glass phase

    Science.gov (United States)

    Syromyatnikov, A. V.; Sizanov, A. V.

    2017-01-01

    We discuss a magnetically ordered ("superfluid") phase near quantum transition to the Bose-glass phase in a simple modeling system, a Heisenberg antiferromagnet with spatial dimension d >2 in an external magnetic field with disorder in exchange coupling constants. Our analytical consideration is based on hydrodynamic description of long-wavelength excitations. Results obtained are valid in the entire critical region near the quantum critical point (QCP), allowing us to describe a possible crossover from one critical behavior to another. We demonstrate that the system behaves in full agreement with predictions by M. P. Fisher et al. [Phys. Rev. B 40, 546 (1989), 10.1103/PhysRevB.40.546] in close vicinity to the QCP. We find as an extension to that analysis that the anomalous dimension η =2 -d and β =ν d /2 , where β and ν are critical exponents of the order parameter and the correlation length, respectively. The density of states per spin of low-energy localized excitations is found to be independent of d ("superuniversal"). We show that many recent experimental and numerical results obtained in various three-dimensional (3D) systems can be described by our formulas using percolation critical exponents. Then, it is a possibility that a percolation critical regime arises in the ordered phase in some 3D systems not very close to the QCP.

  16. Competing States in the t-J Model: Uniform d-Wave State versus Stripe State versus Stripe State

    NARCIS (Netherlands)

    Corboz, P.R.; Rice, T.M.; Troyer, M.

    2014-01-01

    Variational studies of the t-J model on the square lattice based on infinite projected-entangled pair states confirm an extremely close competition between a uniform d-wave superconducting state and different stripe states. The site-centered stripe with an in-phase d-wave order has an equal or only

  17. Model-based magnetization retrieval from holographic phase images

    Energy Technology Data Exchange (ETDEWEB)

    Röder, Falk, E-mail: f.roeder@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Vogel, Karin [Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Wolf, Daniel [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Hellwig, Olav [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); AG Magnetische Funktionsmaterialien, Institut für Physik, Technische Universität Chemnitz, D-09126 Chemnitz (Germany); HGST, A Western Digital Company, 3403 Yerba Buena Rd., San Jose, CA 95135 (United States); Wee, Sung Hun [HGST, A Western Digital Company, 3403 Yerba Buena Rd., San Jose, CA 95135 (United States); Wicht, Sebastian; Rellinghaus, Bernd [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany)

    2017-05-15

    The phase shift of the electron wave is a useful measure for the projected magnetic flux density of magnetic objects at the nanometer scale. More important for materials science, however, is the knowledge about the magnetization in a magnetic nano-structure. As demonstrated here, a dominating presence of stray fields prohibits a direct interpretation of the phase in terms of magnetization modulus and direction. We therefore present a model-based approach for retrieving the magnetization by considering the projected shape of the nano-structure and assuming a homogeneous magnetization therein. We apply this method to FePt nano-islands epitaxially grown on a SrTiO{sub 3} substrate, which indicates an inclination of their magnetization direction relative to the structural easy magnetic [001] axis. By means of this real-world example, we discuss prospects and limits of this approach. - Highlights: • Retrieval of the magnetization from holographic phase images. • Magnetostatic model constructed for a magnetic nano-structure. • Decomposition into homogeneously magnetized components. • Discretization of a each component by elementary cuboids. • Analytic solution for the phase of a magnetized cuboid considered. • Fitting a set of magnetization vectors to experimental phase images.

  18. Shielded ADR Magnets For Space Applications, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The Phase II program will concentrate on manufacturing of qualified low-current, light-weight, 10K ADR magnets for space application. Shielded ADR solenoidal magnets...

  19. The effect of magnetic domain walls on the complex permeability of bulk Z-type cobalt hexaferrite along both W and Y-phases

    Energy Technology Data Exchange (ETDEWEB)

    Daró, Fábio R., E-mail: vonrho.colaborador@ieav.cta.br [Post Graduate Program, Aeronautics Institute of Technology (ITA), Praça Marechal Eduardo Gomes, 50, CEP 12228-900, São José Dos Campos, SP (Brazil); Migliano, Antonio Carlos C. [Applied Physics Division (EFA), Institute for Advanced Studies (IEAv), Trevo Coronel Aviador José Alberto Albano do Amarante, 1, CEP 12228-001, São José Dos Campos, SP (Brazil); Zanella, Glauco P.; Hirata, Anderson K. [Post Graduate Program, Aeronautics Institute of Technology (ITA), Praça Marechal Eduardo Gomes, 50, CEP 12228-900, São José Dos Campos, SP (Brazil); De Polli, Yasmara C. [Applied Physics Division (EFA), Institute for Advanced Studies (IEAv), Trevo Coronel Aviador José Alberto Albano do Amarante, 1, CEP 12228-001, São José Dos Campos, SP (Brazil); Salvadori, Maria Cecília B. [Thin Films Laboratory (LFF), Institute of Physics (IFUSP), University of São Paulo - USP, Rua do Matão, Travessa R, 187, CEP 05508-090, São Paulo, SP (Brazil)

    2016-02-15

    We analyzed a bulk cobalt hexaferrite sample set with the same powder composition obtained by the solid–state reaction method, and made of the W, Y and Z-phases. Transmission/reflection method (TR) measurements of the complex impedance both in radio frequency (RF) and microwave (MW) spectra, as well as reflectance (RL) exhibited high absorption and small losses, still appearing similar to the pattern that is exhibited by the Z-type, even though the largest amount of W-phase. Magnetic force microscopy (MFM), in turn, revealed the existence of narrow magnetic domains consisting of 300–500 nm wide parallel stripes on the crystal basal plane and down to 100 nm wide parallel stripes aligned in parallel to stacked crystal layers that would not be easily perceived by other methods. These domains may contribute to the exhibited complex permeability, since in ferrite both domain wall resonance (DWR) and domain – or spin rotation – resonance (DR) are inversely proportional to the square root of domain width. Nevertheless, we concluded that several flux-pinning defects and impeding factors of the polycrystalline setup, such as charge carriers shown by TR, are probably more important than anisotropy isolated to determine domain setup, and how this acts on the complex magnetic permeability. - Highlights: • MFM detected small magnetic domains not easily perceived by other methods. • High ferromagnetic resonances are favored by narrow magnetic domains. • Electron hopping improves permittivity but is undesirable for permeability.

  20. METHODS OF OBTAINING LONGITUDINAL STRIPES LAYOUTS

    Directory of Open Access Journals (Sweden)

    OANA Dorina

    2014-05-01

    Full Text Available From the technological point of view it is necessary that the phase of warping to be done two or three multiple warp, which results in two or three rolls of the warp final will meet only the warping. To achieve longitudinal striped fabric spinning machines is necessary to have all tensioning mechanism dispensing rolls which requires their special construction. The homogeneity of the fabric from the point of view of the warp yarns tension must be ensured by synchronizing operation of the tensioning two cutting mechanisms of the two reels on which the wires are wound with a degree of waving and thus the fuel consumption at the different weaving. It is recommended that the design be adopted average float bonds, such that the wires can be wrapped around more than two final reels. In terms of manufacturing technology with longitudinal stripes fabrics have a more complicated and expensive technology to cross-striped fabrics for the manufacture of which technology is simplified. Cross-striped fabrics containing groups of warp threads those linked to floating average is materially different. Due to this degree of crimping of wires in the stripes with different bonds makes their contract to be different, having a direct influence on the wires consumption. The different contraction of wire weaving makes warp yarn length, contained in a linked reports are so different that it requires winding wires with different bonds also differing on the final rolls.

  1. Electrically Controllable Spontaneous Magnetism in Nanoscale Mixed Phase Multiferroics

    Energy Technology Data Exchange (ETDEWEB)

    He, Q.; Chu, Y. H.; Heron, J. T.; Yang, S. Y.; Wang, C. H.; Kuo, C. Y.; Lin, H. J.; Yu, P.; Liang, C. W.; Zeches, R. J.; Chen, C. T.; Arenholz, E.; Scholl, A.; Ramesh, R.

    2010-08-02

    The emergence of enhanced spontaneous magnetic moments in self-assembled, epitaxial nanostructures of tetragonal (T-phase) and rhombohedral phases (R-phase) of the multiferroic BiFeO{sub 3} system is demonstrated. X-ray magnetic circular dichroism based photoemission electron microscopy (PEEM) was applied to investigate the local nature of this magnetism. We find that the spontaneous magnetization of the R-phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent T-phase and the epitaxial constraint. Reversible electric field control and manipulation of this magnetic moment at room temperature is shown using a combination of piezoresponse force microscopy and PEEM studies.

  2. Forced two phase helium cooling of large superconducting magnets

    International Nuclear Information System (INIS)

    Green, M.A.; Burns, W.A.; Taylor, J.D.

    1979-08-01

    A major problem shared by all large superconducting magnets is the cryogenic cooling system. Most large magnets are cooled by some variation of the helium bath. Helium bath cooling becomes more and more troublesome as the size of the magnet grows and as geometric constraints come into play. An alternative approach to cooling large magnet systems is the forced flow, two phase helium system. The advantages of two phase cooling in many magnet systems are shown. The design of a two phase helium system, with its control dewar, is presented. The paper discusses pressure drop of a two phase system, stability of a two phase system and the method of cool down of a two phase system. The results of experimental measurements at LBL are discussed. Included are the results of cool down and operation of superconducting solenoids

  3. Magnetism and Microstructure Characterization of Phase Transitions in a Steel

    Directory of Open Access Journals (Sweden)

    M. Güler

    2014-01-01

    Full Text Available We present phase transitions in a low carbon steel according to existing phases and their magnetism. Scanning electron microscope employed research to clarify and evaluate the microstructural details. Additionally, we utilized from Mössbauer spectroscopy for magnetic characteristics of different existed phases. Scanning electron microscope examinations showed that the pure state of the steel was fully in the ferrite phase with equiaxed grains. Moreover, subsequent heat treatments on the studied steel also ensured the first austenite and then pearlite phase formation. Mössbauer spectroscopy of these phases appeared as a paramagnetic single-line absorption peak for the austenite phase and ferromagnetic six-line spectra for both ferrite and pearlite phases. From Mössbauer data, we determined that the internal magnetic fields of ferrite and pearlite phases were as 32.2 Tesla and 31.3 Tesla, respectively.

  4. Magnetic phase diagrams from non-collinear canonical band theory

    DEFF Research Database (Denmark)

    Shallcross, Sam; Nordstrom, L.; Sharma, S.

    2007-01-01

    to construct phase diagrams of magnetic order for the fcc and bcc lattices. Several examples of non-collinear magnetism are seen to be canonical in origin, in particular, that of gamma-Fe. In this approach, the determination of magnetic stability results solely from changes in kinetic energy due to spin...

  5. Out-of-phase magnetic susceptibility and environmental magnetism

    Czech Academy of Sciences Publication Activity Database

    Hrouda, F.; Chadima, Martin; Ježek, J.

    2016-01-01

    Roč. 18 (2016), EGU2016-6808 ISSN 1607-7962. [European Geosciences Union General Assembly 2016. 17.04.2016-22.04.2016, Vienna] Institutional support: RVO:67985831 Keywords : paleomagnetism * magnetic susceptibility * environmental magnetism Subject RIV: DE - Earth Magnetism , Geodesy, Geography http://meetingorganizer.copernicus.org/EGU2016/EGU2016-6808.pdf

  6. On the coexistence of the magnetic phases in chromium alloys

    DEFF Research Database (Denmark)

    Lebech, Bente; Mikke, K.

    1969-01-01

    Detailed neutron diffraction investigations have been performed on Cr-Re alloys in order to explain the several observations in Cr alloys of the coexistence of a commensurable and an oscillatory magnetic phase. It is concluded that the individual magnetic phases probably occur in separate domains....

  7. Structural phase transitions in isotropic magnetic elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Meilikhov, E. Z., E-mail: meilikhov@yandex.ru; Farzetdinova, R. M. [National Research Center “Kurchatov Institute” (Russian Federation)

    2016-06-15

    Magnetic elastomers represent a new type of materials that are “soft” matrices with “hard” magnetic granules embedded in them. The elastic forces of the matrix and the magnetic forces acting between granules are comparable in magnitude even under small deformations. As a result, these materials acquire a number of new properties; in particular, their mechanical and/or magnetic characteristics can depend strongly on the polymer matrix filling with magnetic particles and can change under the action of an external magnetic field, pressure, and temperature. To describe the properties of elastomers, we use a model in which the interaction of magnetic granules randomly arranged in space with one another is described in the dipole approximation by the distribution function of dipole fields, while their interaction with the matrix is described phenomenologically. A multitude of deformation, magnetic-field, and temperature effects that are described in this paper and are quite accessible to experimental observation arise within this model.

  8. Soft mode and magnetic phase transition in PrNi

    International Nuclear Information System (INIS)

    Alekseev, P.A.; Lazukov, V.N.; Sadikov, I.P.; Klement'ev, E.S.; Allenspach, P.; Chumlyakov, Yu.I.

    2002-01-01

    The spectrum of the magnetic excitation of the PrNi intermetallic compound monocrystal is studied through the neutrons inelastic scattering. Essential softening of certain collective modes of the magnetic excitation near the temperature of the ferromagnetic ordering T c ∼ 20 K is identified. The above result is analyzed from the viewpoint of the model, describing the magnetic phase transition in the systems with the directed magnetic moment [ru

  9. Phase separation in La-Ca manganites: Magnetic field effects

    Energy Technology Data Exchange (ETDEWEB)

    Tovar, M.; Causa, M.T. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica and Universidad Nacional de Cuyo, 8400 San Carlos de Bariloche, Rio Negro (Argentina); Ramos, C.A. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica and Universidad Nacional de Cuyo, 8400 San Carlos de Bariloche, Rio Negro (Argentina)], E-mail: cramos@cab.cnea.gov.ar; Laura-Ccahuana, D. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica and Universidad Nacional de Cuyo, 8400 San Carlos de Bariloche, Rio Negro (Argentina); Universidad Nacional de Ingenieria, Av. Tupac Amaru 210, Rimac/Lima 25 (Peru)

    2008-02-15

    The coexistence of magnetic phases seems to be a characteristic of the La-Ca family of in colossal magnetoresistant manganites. We have analyzed this phenomenon in terms of a free energy, F, where magnetic and electronic contributions of two coexistent phases are included. Three order parameters describe the behavior of the mixed material: the magnetization of each phase and the metallic fraction. Due to the coupling between order parameters there is a range: T**{<=}T{<=}T* where coexistence is possible. Values for the phenomenological parameters are obtained from the experiment. In this paper we analyze the effects of an applied magnetic field on the range of T where the phase coexistence takes place, based on results obtained from dc-magnetization and ESR measurements.

  10. Magnetic liquid metal two-phase flow research. Phase 1. Final report

    International Nuclear Information System (INIS)

    Graves, R.D.

    1983-04-01

    The Phase I research demonstrates the feasibility of the magnetic liquid metal (MLM) two-phase flow concept. A dispersion analysis is presented based on a complete set of two-phase-flow equations augmented to include stresses due to magnetic polarization of the fluid. The analysis shows that the stability of the MLM two-phase flow is determined by the magnetic Mach number, the slip ratio, geometry of the flow relative to the applied magnetic field, and by the voidage dependence of the interfacial forces. Results of a set of experiments concerned with magnetic effects on the dynamics of single bubble motion in an aqueous-based, viscous, conducting magnetic fluid are presented. Predictions in the theoretical literature are qualitatively verified using a bench-top experimental apparatus. In particular, applied magnetic fields are seen to lead to reduced bubble size at fixed generating orifice pressure

  11. Dual phase magnetic material component and method of forming

    Science.gov (United States)

    Dial, Laura Cerully; DiDomizio, Richard; Johnson, Francis

    2017-04-25

    A magnetic component having intermixed first and second regions, and a method of preparing that magnetic component are disclosed. The first region includes a magnetic phase and the second region includes a non-magnetic phase. The method includes mechanically masking pre-selected sections of a surface portion of the component by using a nitrogen stop-off material and heat-treating the component in a nitrogen-rich atmosphere at a temperature greater than about 900.degree. C. Both the first and second regions are substantially free of carbon, or contain only limited amounts of carbon; and the second region includes greater than about 0.1 weight % of nitrogen.

  12. Critical assessment of the evidence for striped nanoparticles.

    Directory of Open Access Journals (Sweden)

    Julian Stirling

    Full Text Available There is now a significant body of literature which reports that stripes form in the ligand shell of suitably functionalised Au nanoparticles. This stripe morphology has been proposed to strongly affect the physicochemical and biochemical properties of the particles. We critique the published evidence for striped nanoparticles in detail, with a particular focus on the interpretation of scanning tunnelling microscopy (STM data (as this is the only technique which ostensibly provides direct evidence for the presence of stripes. Through a combination of an exhaustive re-analysis of the original data, in addition to new experimental measurements of a simple control sample comprising entirely unfunctionalised particles, we show that all of the STM evidence for striped nanoparticles published to date can instead be explained by a combination of well-known instrumental artefacts, or by issues with data acquisition/analysis protocols. We also critically re-examine the evidence for the presence of ligand stripes which has been claimed to have been found from transmission electron microscopy, nuclear magnetic resonance spectroscopy, small angle neutron scattering experiments, and computer simulations. Although these data can indeed be interpreted in terms of stripe formation, we show that the reported results can alternatively be explained as arising from a combination of instrumental artefacts and inadequate data analysis techniques.

  13. Critical assessment of the evidence for striped nanoparticles.

    Science.gov (United States)

    Stirling, Julian; Lekkas, Ioannis; Sweetman, Adam; Djuranovic, Predrag; Guo, Quanmin; Pauw, Brian; Granwehr, Josef; Lévy, Raphaël; Moriarty, Philip

    2014-01-01

    There is now a significant body of literature which reports that stripes form in the ligand shell of suitably functionalised Au nanoparticles. This stripe morphology has been proposed to strongly affect the physicochemical and biochemical properties of the particles. We critique the published evidence for striped nanoparticles in detail, with a particular focus on the interpretation of scanning tunnelling microscopy (STM) data (as this is the only technique which ostensibly provides direct evidence for the presence of stripes). Through a combination of an exhaustive re-analysis of the original data, in addition to new experimental measurements of a simple control sample comprising entirely unfunctionalised particles, we show that all of the STM evidence for striped nanoparticles published to date can instead be explained by a combination of well-known instrumental artefacts, or by issues with data acquisition/analysis protocols. We also critically re-examine the evidence for the presence of ligand stripes which has been claimed to have been found from transmission electron microscopy, nuclear magnetic resonance spectroscopy, small angle neutron scattering experiments, and computer simulations. Although these data can indeed be interpreted in terms of stripe formation, we show that the reported results can alternatively be explained as arising from a combination of instrumental artefacts and inadequate data analysis techniques.

  14. Wheat Stripe Rust

    OpenAIRE

    Pace, Mike; Israelsen, Clark; Evans, Kent; Barnhill, James

    2008-01-01

    Stripe rust, or yellow rust, is primarily a foliar fungal disease of wheat, although it can infect spike and stem tissues. If the pathogen infects the spike (head) it causes extensive quality and grain yield loss. The disease is caused by the fungus Puccinia striiformis f. sp. tritici. The fungus can only survive and reproduce on wheat. It survives from one season to the next on volunteer plants.

  15. Stripe order from the perspective of the Hubbard model

    Energy Technology Data Exchange (ETDEWEB)

    Devereaux, Thomas Peter

    2018-03-01

    A microscopic understanding of the strongly correlated physics of the cuprates must account for the translational and rotational symmetry breaking that is present across all cuprate families, commonly in the form of stripes. Here we investigate emergence of stripes in the Hubbard model, a minimal model believed to be relevant to the cuprate superconductors, using determinant quantum Monte Carlo (DQMC) simulations at finite temperatures and density matrix renormalization group (DMRG) ground state calculations. By varying temperature, doping, and model parameters, we characterize the extent of stripes throughout the phase diagram of the Hubbard model. Our results show that including the often neglected next-nearest-neighbor hopping leads to the absence of spin incommensurability upon electron-doping and nearly half-filled stripes upon hole-doping. The similarities of these findings to experimental results on both electron and hole-doped cuprate families support a unified description across a large portion of the cuprate phase diagram.

  16. Spin beam splitter based on Goos-Haenchen shifts in two-dimensional electron gas modulated by ferromagnetic and Schottky metal stripes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Mao-Wang; Huang, Xin-Hong; Zhang, Gui-Lin; Chen, Sai-Yan [College of Science, Guilin University of Technology, Guilin 541004 (China)

    2012-11-15

    We present a theoretical study on the spin-dependent Goos-Haenchen (GH) effect in a two-dimensional electron gas modulated by ferromagnetic and Schottky metal (SM) stripes. The GH shifts for spin electron beams across this device are calculated with the help of the stationary phase method. It is shown that the GH shift of spin-up beam is significantly different from that of spin-down beam, i.e., this device shows up a considerable spin polarization effect in GH shifts of electron beams. It also is shown that both magnitude and sign of spin polarization of GH shifts are closely related to the stripe width, the magnetic strength and the gated voltage under SM stripe. These interesting properties not only provide an effective method of spin injection for spintronics application, but also give rise to a tunable spin beam splitter. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Magnetic phase diagram of the Fe-Ni system

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, W., E-mail: wxiong@yahoo.com [Division of Computational Thermodynamics, Department of Materials Science and Engineering, KTH (Royal Institute of Technology), Brinellvaegen 23, SE-100 44 Stockholm (Sweden); State Key Lab of Powder Metallurgy, Central South University, Changsha 410083 (China); Zhang, H.; Vitos, L. [Division of Applied Physics, Department of Materials Science and Engineering, KTH (Royal Institute of Technology), Brinellvaegen 23, SE-100 44 Stockholm (Sweden); Selleby, M. [Division of Computational Thermodynamics, Department of Materials Science and Engineering, KTH (Royal Institute of Technology), Brinellvaegen 23, SE-100 44 Stockholm (Sweden)

    2011-01-15

    Magnetic phase diagrams of body-centered cubic and face-centered cubic Fe-Ni alloys were constructed using available experimental data and ab initio calculations. The results show that significant improvements in the 'standard' diagrams (handbooks and CALPHAD databases) are required. The present work demonstrates that the CALPHAD magnetic model is not sophisticated enough to describe the Fe-Ni system. In addition, a new thermodynamic description of the lattice stability for pure Ni is urgently needed, since the recommended magnetic properties for CALPHAD modeling are distinct from the experimental and ab initio results. This work indicates that the construction of magnetic phase diagrams is indispensable during the phase transformation study of magnetic systems.

  18. Standing magnetic wave on Ising ferromagnet: Nonequilibrium phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Halder, Ajay, E-mail: ajay.rs@presiuniv.ac.in; Acharyya, Muktish, E-mail: muktish.physics@presiuniv.ac.in

    2016-12-15

    The dynamical response of an Ising ferromagnet to a plane polarised standing magnetic field wave is modelled and studied here by Monte Carlo simulation in two dimensions. The amplitude of standing magnetic wave is modulated along the direction x. We have detected two main dynamical phases namely, pinned and oscillating spin clusters. Depending on the value of field amplitude the system is found to undergo a phase transition from oscillating spin cluster to pinned as the system is cooled down. The time averaged magnetisation over a full cycle of magnetic field oscillations is defined as the dynamic order parameter. The transition is detected by studying the temperature dependences of the variance of the dynamic order parameter, the derivative of the dynamic order parameter and the dynamic specific heat. The dependence of the transition temperature on the magnetic field amplitude and on the wavelength of the magnetic field wave is studied at a single frequency. A comprehensive phase boundary is drawn in the plane described by the temperature and field amplitude for two different wavelengths of the magnetic wave. The variation of instantaneous line magnetisation during a period of magnetic field oscillation for standing wave mode is compared to those for the propagating wave mode. Also the probability that a spin at any site, flips, is calculated. The above mentioned variations and the probability of spin flip clearly distinguish between the dynamical phases formed by propagating magnetic wave and by standing magnetic wave in an Ising ferromagnet. - Highlights: • The Ising ferromagnet. • The system is driven by standing magnetic wave. • The low temperature pinned phase is observed • The high temperature oscillating spin bands are observed • The nonequilibrium phase boundary is drawn.

  19. Wireless Magnetic Sensor with Orthogonal Frequency Coding, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal of this SBIR Phase I research project is to develop batteryless, wireless magnetic sensors with orthogonal frequency coding (OFC). These sensors will be...

  20. Inorganic Nanostructured High-Temperature Magnet Wires, Phase I

    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...

  1. Laser Femto-Tesla Magnetic Gradiometer (LFMG), Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The LFMG instrument is used to make extremely high resolution scalar magnetic field and difference measurements at the Earthfs surface. The Phase 1 effort included...

  2. Laser Femto-Tesla Magnetic Gradiometer (LFMG), Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase 1 SBIR proposal describes development of a conceptual design for a Laser Femto-Tesla Magnetic Gradiometer (LFMG). The LFMG innovations include the ability...

  3. Quantum phase transition of a magnet in a spin bath

    DEFF Research Database (Denmark)

    Rønnow, H.M.; Parthasarathy, R.; Jensen, J.

    2005-01-01

    The excitation spectrum of a model magnetic system, LiHoF(4), was studied with the use of neutron spectroscopy as the system was tuned to its quantum critical point by an applied magnetic field. The electronic mode softening expected for a quantum phase transition was forestalled by hyperfine...

  4. Simple explanation for the reentrant magnetic phase transition in Pr ...

    Indian Academy of Sciences (India)

    The reentrant magnetic phase transition in Pr0.5Sr0.41Ca0.09MnO3 perovskite is explained using the Ising spin model on the square lattice with mixed ferromagnetic and antiferromagnetic exchange interactions. It is shown using numerical calculations that this effect is strongly affected by the external magnetic field and ...

  5. Simple explanation for the reentrant magnetic phase transition in

    Indian Academy of Sciences (India)

    The reentrant magnetic phase transition in Pr0.5Sr0.41Ca0.09MnO3 perovskite is explained using the Ising spin model on the square lattice with mixed ferromagnetic and antiferromagnetic exchange interactions. It is shown using numerical calculations that this effect is strongly affected by the external magnetic field and ...

  6. Magnetic Phase Transitions of CeSb. I

    DEFF Research Database (Denmark)

    Fischer, Pernille Hertz; Lebech, Bente; Meier, G.

    1978-01-01

    The magnetic ordering of the anomalous antiferromagnet CeSb, which has a NaCl crystal structure, was determined in zero applied magnetic field by means of neutron diffraction investigations of single crystals and powder. Below the Neel temperature TN of (16.1+or-0.1)K, there exist six partially...... a first-order phase transition at TN. At approximately TN/2 there is a first-order phase transition to a FCC type IA low-temperature configuration. The unusual magnetic properties of CeSb, which result from anisotropic exchange and crystalline electric field effects, resemble those of certain actinide Na...

  7. Extragalactic magnetic fields unlikely generated at the electroweak phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Wagstaff, Jacques M.; Banerjee, Robi, E-mail: jwagstaff@hs.uni-hamburg.de, E-mail: banerjee@hs.uni-hamburg.de [Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg (Germany)

    2016-01-01

    In this paper we show that magnetic fields generated at the electroweak phase transition are most likely too weak to explain the void magnetic fields apparently observed today unless they have considerable helicity. We show that, in the simplest estimates, the helicity naturally produced in conjunction with the baryon asymmetry is too small to explain observations, which require a helicity fraction at least of order 10{sup −14}–10{sup −10} depending on the void fields constraint used. Therefore new mechanisms to generate primordial helicity are required if magnetic fields generated during the electroweak phase transition should explain the extragalactic fields.

  8. Magnetic Solid Phase Extraction Applied to Food Analysis

    Directory of Open Access Journals (Sweden)

    Israel S. Ibarra

    2015-01-01

    Full Text Available Magnetic solid phase extraction has been used as pretreatment technique for the analysis of several compounds because of its advantages when it is compared with classic methods. This methodology is based on the use of magnetic solids as adsorbents for preconcentration of different analytes from complex matrices. Magnetic solid phase extraction minimizes the use of additional steps such as precipitation, centrifugation, and filtration which decreases the manipulation of the sample. In this review, we describe the main procedures used for synthesis, characterization, and application of this pretreatment technique which were applied in food analysis.

  9. Magnetostrictive hypersound generation by spiral magnets in the vicinity of magnetic field induced phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Bychkov, Igor V. [Chelyabinsk State University, 129 Br. Kashirinykh Str., Chelyabinsk 454001 (Russian Federation); South Ural State University (National Research University), 76 Lenin Prospekt, Chelyabinsk 454080 (Russian Federation); Kuzmin, Dmitry A., E-mail: kuzminda@csu.ru [Chelyabinsk State University, 129 Br. Kashirinykh Str., Chelyabinsk 454001 (Russian Federation); South Ural State University (National Research University), 76 Lenin Prospekt, Chelyabinsk 454080 (Russian Federation); Kamantsev, Alexander P.; Koledov, Victor V.; Shavrov, Vladimir G. [Kotelnikov Institute of Radio-engineering and Electronics of RAS, Mokhovaya Street 11-7, Moscow 125009 (Russian Federation)

    2016-11-01

    In present work we have investigated magnetostrictive ultrasound generation by spiral magnets in the vicinity of magnetic field induced phase transition from spiral to collinear state. We found that such magnets may generate transverse sound waves with the wavelength equal to the spiral period. We have examined two types of spiral magnetic structures: with inhomogeneous exchange and Dzyaloshinskii–Moriya interactions. Frequency of the waves from exchange-caused spiral magnetic structure may reach some THz, while in case of Dzyaloshinskii–Moriya interaction-caused spiral it may reach some GHz. These waves will be emitted like a sound pulses. Amplitude of the waves is strictly depends on the phase transition speed. Some aspects of microwaves to hypersound transformation by spiral magnets in the vicinity of phase transition have been investigated as well. Results of the work may be interesting for investigation of phase transition kinetics as well, as for various hypersound applications. - Highlights: • Magnetostrictive ultrasound generation by spiral magnets at phase transition (PT) is studied. • Spiral magnets during PT may generate transverse sound with wavelength equal to spiral period. • Amplitude of the sound is strictly depends on the phase transition speed. • Microwave-to-sound transformation in the vicinity of PT is investigated as well.

  10. Electronic structure of a striped nickelate studied by the exact exchange for correlated electrons (EECE) approach

    KAUST Repository

    Schwingenschlögl, Udo

    2009-12-01

    Motivated by a RIXS study of Wakimoto, et al.(Phys. Rev. Lett., 102 (2009) 157001) we use density functional theory to analyze the magnetic order in the nickelate La5/3Sr1/3NiO4 and the details of its crystal and electronic structure. We compare the generalized gradient approximation to the hybrid functional approach of exact exchange for correlated electrons (EECE). In contrast to the former, the latter reproduces the insulating state of the compound and the midgap states. The EECE approach, in general, appears to be appropriate for describing stripe phases in systems with orbital degrees of freedom. Copyright © EPLA, 2009.

  11. Microwave permeability of stripe patterned FeCoN thin film

    International Nuclear Information System (INIS)

    Wu, Yuping; Yang, Yong; Ma, Fusheng; Zong, Baoyu; Yang, Zhihong; Ding, Jun

    2017-01-01

    Magnetic stripe patterns are of great importance for microwave applications owing to their highly tunable microwave permeability by adjusting the geometrical dimensions. In this work, stripe patterned FeCoN films with 160 nm thickness are fabricated by using standard UV photolithography. Their microwave permeability are investigated systematically via both experiment and micromagnetic simulation. The good agreement between experimental and simulation results suggests that stripe width is crucial for the microwave magnetic properties of the stripe pattern. It is demonstrated by simulation that with increasing stripe width from 1 to 80 µm the initial permeability shows a continuous growth from about 8–322, whiles the resonance frequency drops dramatically from 18.7 to 3.1 GHz at 4 µm gap size. Smaller gap size would result in slightly increased initial permeability due to larger magnetic volume ratio, accompanied by decreased resonance frequency because of stronger magnetostatic interaction. Moreover, the experimental investigation on stripe length effect indicates that the stripe length should be kept as long as possible to achieve uniform bulk resonance mode and high permeability value. Insufficient stripe length would result in low frequency edge mode and decayed bulk mode. This study could provide valuable guidelines on the selection of proper geometry dimensions of FeCoN stripe patterns for high frequency applications. - Highlights: • This work presents a systematic study on permeability of FeCoN stripe pattern. • Geometrical parameters of the stripe pattern are systematically optimized. • Several important conclusions has been obtained. • The results offer guideline on FeCoN stripe patterns for high frequency applications.

  12. Microwave permeability of stripe patterned FeCoN thin film

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yuping [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 1, Singapore 117411 (Singapore); Yang, Yong, E-mail: tslyayo@nus.edu.sg [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 1, Singapore 117411 (Singapore); Ma, Fusheng; Zong, Baoyu; Yang, Zhihong [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 1, Singapore 117411 (Singapore); Ding, Jun [Department of Materials Science and Engineering, National University of Singapore, Singapore 117574 (Singapore)

    2017-03-15

    Magnetic stripe patterns are of great importance for microwave applications owing to their highly tunable microwave permeability by adjusting the geometrical dimensions. In this work, stripe patterned FeCoN films with 160 nm thickness are fabricated by using standard UV photolithography. Their microwave permeability are investigated systematically via both experiment and micromagnetic simulation. The good agreement between experimental and simulation results suggests that stripe width is crucial for the microwave magnetic properties of the stripe pattern. It is demonstrated by simulation that with increasing stripe width from 1 to 80 µm the initial permeability shows a continuous growth from about 8–322, whiles the resonance frequency drops dramatically from 18.7 to 3.1 GHz at 4 µm gap size. Smaller gap size would result in slightly increased initial permeability due to larger magnetic volume ratio, accompanied by decreased resonance frequency because of stronger magnetostatic interaction. Moreover, the experimental investigation on stripe length effect indicates that the stripe length should be kept as long as possible to achieve uniform bulk resonance mode and high permeability value. Insufficient stripe length would result in low frequency edge mode and decayed bulk mode. This study could provide valuable guidelines on the selection of proper geometry dimensions of FeCoN stripe patterns for high frequency applications. - Highlights: • This work presents a systematic study on permeability of FeCoN stripe pattern. • Geometrical parameters of the stripe pattern are systematically optimized. • Several important conclusions has been obtained. • The results offer guideline on FeCoN stripe patterns for high frequency applications.

  13. Structural and magnetic phase formation in nanophase brass–iron ...

    Indian Academy of Sciences (India)

    the fcc phase as a function of Fe concentration was investigated by Mössbauer spectroscopy and X-ray diffraction. The grain size, lattice parameters, and average hyperfine magnetic field distributions were estimated for the nanophase alloys. The fcc phase was observed to persist up to 40 atomic per cent Fe substitutions, ...

  14. Magnetic Phase Transitions of CeSb. II: Effects of Applied Magnetic Fields

    DEFF Research Database (Denmark)

    Meier, G.; Fischer, P.; Hälg, W.

    1978-01-01

    For pt.I see ibid., vol.11, p.345 (1978). The metamagnetic phase transition and the associated phase diagram of the anomalous antiferromagnet CeSb were determined in a neutron diffraction study of the magnetic ordering of CeSb single crystals in applied magnetic fields parallel to the (001...... magnetic fields. The observed magnetic structures do not correspond to the stable configurations expected from the molecular field theory of the face-centred cubic lattice. The change from a first-order transition at the Neel temperature in zero field to second-order transition at high fields points...

  15. Moessbauer study of magnetic phases of natural pyrrhotites

    International Nuclear Information System (INIS)

    Hucl, M.; Janak, F.; Zapletal, K.

    1975-01-01

    Natural pyrrhotites from ten localities were studied by Moessbauer spectroscopy. Both basic magnetic phases, i.e., ferrimagnetic and antiferromagnetic were determined by the method of powder patterns, by the analysis of thermomagnetic curves and by an electron microprobe. For the Moessbauer study three samples purely ferrimagnetic, four samples almost purely antiferromagnetic (containing less than 5 % of the ferrimagnetic phase), and three samples containing large amounts of both phases microscopically intergrown were used. (Z.S.)

  16. A solution phase fabrication of magnetic nanoparticles encapsulated in carbon

    International Nuclear Information System (INIS)

    Wei Xianwen; Zhu Guoxing; Xia Chuanjun; Ye Yin

    2006-01-01

    To avoid high energy consumption, intensive use of hardware and high cost in the manufacture of nanoparticles encapsulated in carbon, a simple, efficient and economical solution-phase method for the fabrication of FeNi at C nanostructures has been explored. The reaction to the magnetic metal at C structures here is conducted at a relatively low temperature (160 deg. C) and this strategy can be transferred to prepare other transition metal at C core-shell nanostructures. The saturation magnetization of metal in metal at C nanostructures is similar to those of the corresponding buck metals. Magnetic metal at C nanostructures with magnetic metal nanoparticles inside and a functionalized carbon surface outside may not only provide the opportunity to tailor the magnetic properties for magnetic storage devices and therapeutics but also make possible the loading of other functional molecules (e.g. enzymes, antigens) for clinic diagnostics, molecular biology, bioengineering, and catalysis

  17. Magnetically Modified Asymmetric Supercapacitors, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is for the development of an asymmetric supercapacitor that will have improved energy density and cycle life....

  18. Tunneling anisotropic magnetoresistance driven by magnetic phase transition.

    Science.gov (United States)

    Chen, X Z; Feng, J F; Wang, Z C; Zhang, J; Zhong, X Y; Song, C; Jin, L; Zhang, B; Li, F; Jiang, M; Tan, Y Z; Zhou, X J; Shi, G Y; Zhou, X F; Han, X D; Mao, S C; Chen, Y H; Han, X F; Pan, F

    2017-09-06

    The independent control of two magnetic electrodes and spin-coherent transport in magnetic tunnel junctions are strictly required for tunneling magnetoresistance, while junctions with only one ferromagnetic electrode exhibit tunneling anisotropic magnetoresistance dependent on the anisotropic density of states with no room temperature performance so far. Here, we report an alternative approach to obtaining tunneling anisotropic magnetoresistance in α'-FeRh-based junctions driven by the magnetic phase transition of α'-FeRh and resultantly large variation of the density of states in the vicinity of MgO tunneling barrier, referred to as phase transition tunneling anisotropic magnetoresistance. The junctions with only one α'-FeRh magnetic electrode show a magnetoresistance ratio up to 20% at room temperature. Both the polarity and magnitude of the phase transition tunneling anisotropic magnetoresistance can be modulated by interfacial engineering at the α'-FeRh/MgO interface. Besides the fundamental significance, our finding might add a different dimension to magnetic random access memory and antiferromagnet spintronics.Tunneling anisotropic magnetoresistance is promising for next generation memory devices but limited by the low efficiency and functioning temperature. Here the authors achieved 20% tunneling anisotropic magnetoresistance at room temperature in magnetic tunnel junctions with one α'-FeRh magnetic electrode.

  19. Magnetic ground state of FeSe

    Science.gov (United States)

    Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K.; Iida, K.; Christianson, A. D.; Walker, H. C.; Adroja, D. T.; Abdel-Hafiez, M.; Chen, Xiaojia; Chareev, D. A.; Vasiliev, A. N.; Zhao, Jun

    2016-01-01

    Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities. PMID:27431986

  20. Magnetic-field-induced phase transitions in Wigner molecules

    CERN Document Server

    Szafran, B; Adamowski, J

    2003-01-01

    A theoretical analysis of formation and symmetry transformations is presented for Wigner molecules with N = 2,..., 20 electrons confined in quantum dots at high magnetic fields. Using the unrestricted Hartree-Fock method with the multicentre Gaussian basis, we have found that Wigner molecules with N >= 6 abruptly change their shape and symmetry with an associated jump in the first derivative of the ground-state energy, i.e. they undergo phase transitions. In particular, the phases of the Wigner molecules obtained just after emerging from the maximum-density droplet (MDD) phase possess a different symmetry from that formed at a high magnetic field. We show that the properties of the electron-electron interaction energy demonstrate very well both the breakdown of the MDD and the quasi-classical character of the Wigner molecule in the high magnetic field. Possible mechanisms of the MDD decay are discussed.

  1. INVESTIGATION OF MAGNETIC MODE FOR 3-PHASE TRANSFORMER WITH SYMMETRICAL MAGNETIC CONDUCTOR OF FRAME DESIGN

    Directory of Open Access Journals (Sweden)

    A. A. Mazurenko

    2017-01-01

    Full Text Available Magnetic mode for 3-phase transformer with symmetrical magnetic conductor of frame design has been investigated on schematic model. The scheme consists of three non-linear coils having star-connection without zero wire. Weberampere characteristics correspond to similar parameters of separate frames of a magnetic conductor. It has been accepted that a magnetic flow of every frame is closed on itself without passing into other frame of the magnetic conductor. Electromagnetic state of equivalent diagram has been described by a system of differential equations which were solved with the help of MathCad program. Investigations have resulted in calculation of functions for magnetic frame induction and magnetizing current and their harmonic compositions; dependence of actual amplitude for magnetic field induction on amplitude of the main harmonic induction has been determined in the paper. While executing experiments it has been revealed the following: induction amplitude of the main harmonic in the magnetic field within frames of the magnetic conductor is higher in comparison with the design induction value by 15.5 %; due to non-linearity of weber-ampere characteristics in frames and properties of 3-phase system harmonic components, which are multiple of three, are initiated in the functions of magnetic induction for separate frames; high-order harmonics of function for magnetic frame induction being imposed on the main harmonic decrease an actual amplitude of magnetic field induction practically up to the design induction value within the operational range of the actual amplitude and in this context coefficients of high-order harmonics change insignificantly; harmonic components, which are multiple of three, are absent in magnetizing currents. 

  2. Magnetic phase diagram of FeO at high pressure

    Science.gov (United States)

    Zhang, Peng; Cohen, R. E.; Haule, K.

    2017-05-01

    FeO is an insulator with anti-ferromagnetic (AFM) spin ordering at ambient pressure. At increased external pressure, the Néel temperature of FeO first increases at the pressure below 40 GPa. Experiments predict that the AFM ordering will collapse above 80 GPa, but the mechanism of the high pressure magnetic collapse is still unknown. Using the combination of density functional theory and dynamical mean-field theory (DFT+DMFT), the nature of the magnetic collapse of FeO is examined and its magnetic phase diagram up to 180 GPa is discussed.

  3. Nonvolatile memory design magnetic, resistive, and phase change

    CERN Document Server

    Li, Hai

    2011-01-01

    The manufacture of flash memory, which is the dominant nonvolatile memory technology, is facing severe technical barriers. So much so, that some emerging technologies have been proposed as alternatives to flash memory in the nano-regime. Nonvolatile Memory Design: Magnetic, Resistive, and Phase Changing introduces three promising candidates: phase-change memory, magnetic random access memory, and resistive random access memory. The text illustrates the fundamental storage mechanism of these technologies and examines their differences from flash memory techniques. Based on the latest advances,

  4. Magnetic phase transition of CsCuCl3 in pulsed magnetic field

    International Nuclear Information System (INIS)

    Mino, Michinobu; Ubukata, Katsunori; Bokui, Takahiro; Arai, Masatoshi; Motokawa, Mitsuhiro; Tanaka, Hidekazu.

    1993-01-01

    Neutron diffraction measurements of a triangular lattice antiferromagnet CsCuCl 3 have been done in a pulsed high magnetic field up to 14T. The field applied parallel to the c-axis and it is observed that the reflection intensity at (1/3 1/3 0.085), which corresponds to the low field magnetic structure, abruptly decreases at Bc = 10T, where the magnetization shows a small jump. Above Bc, a new reflection at (1/3 1/3 0) appears. These results are consistent with a model that a new type of magnetic phase transition occurs due to the quantum effect. (author)

  5. Phase composition and magnetic properties in hot deformed magnets based on Misch-metal

    Science.gov (United States)

    Ma, Q.; Zhang, Z. Y.; Zhang, X. F.; Hu, Z. F.; Liu, Y. L.; Liu, F.; Jv, X. M.; Wang, J.; Li, Y. F.; Zhang, J. X.

    2018-04-01

    In this paper, the Rare-earth Iron Boron (RE-Fe-B) magnets were fabricated successfully by using the double main phase method through mixing the Neodymium Iron Boron (Nd-Fe-B) powders and Misch-metal Iron Boron (MM-Fe-B) powders with different ratio. Aiming at the nanocrystalline RE2Fe14B magnets prepared by using spark plasma sintering technology, phase structure and magnetic properties were investigated. It is found that the Misch-metal (MM) alloys promote the domain nucleation during the the process of magnetization reversal and then damage the coercivity (Hcj) of isotropic RE2Fe14B magnets, while the Hcj could still remain more than 1114.08 kA/m when the mass proportion of MM (simplified as: "a") is 30%. Curie temperature and phase structure were also researched. Two kinds of mixed-solid-solution (MSS) main phases with different Lanthanum (La) and Cerium (Ce) content were believed to be responsible for the two curie temperature of the RE2Fe14B magnets with "a" ≥20%. This is resulted from the inhomogeneous elemental distribution of RE2Fe14B phase.

  6. Phase Equilibria and Magnetic Phases in the Ce-Fe-Co-B System

    Directory of Open Access Journals (Sweden)

    Tian Wang

    2016-12-01

    Full Text Available Ce-Fe-Co-B is a promising system for permanent magnets. A high-throughput screening method combining diffusion couples, key alloys, Scanning Electron Microscope/Wavelength Dispersive X-ray Spectroscope (SEM/WDS, and Magnetic Force Microscope (MFM is used in this research to understand the phase equilibria and to explore promising magnetic phases in this system. Three magnetic phases were detected and their homogeneity ranges were determined at 900 °C, which were presented by the formulae: Ce2Fe14−xCoxB (0 ≤ x ≤ 4.76, CeCo4−xFexB (0 ≤ x ≤ 3.18, and Ce3Co11−x FexB4 (0 ≤ x ≤ 6.66. The phase relations among the magnetic phases in this system have been studied. Ce2(Fe, Co14B appears to have stronger magnetization than Ce(Co, Fe4B and Ce3(Co, Fe11B4 from MFM analysis when comparing the magnetic interactions of selected key alloys. Also, a non-magnetic CeCo12−xFexB6 (0 ≤ x ≤ 8.74 phase was detected in this system. A boron-rich solid solution with Ce13FexCoyB45 (32 ≤ x ≤ 39, 3 ≤ y ≤ 10 chemical composition was also observed. However, the crystal structure of this phase could not be found in the literature. Moreover, ternary solid solutions ε1 (Ce2Fe17−xCox (0 ≤ x ≤ 12.35 and ε2 (Ce2Co17−xFex (0 ≤ x ≤ 3.57 were found to form between Ce2Fe17 and Ce2Co17 in the Ce-Fe-Co ternary system at 900 °C.

  7. Magnetic phase diagram of magnetoelectric LiMnPO4

    DEFF Research Database (Denmark)

    Toft-Petersen, Rasmus; Andersen, Niels Hessel; Li, Haifeng

    2012-01-01

    The nature of the spin-flop (SF) transition in the magnetoelectric quasi-2D Heisenberg system LiMnPO4 is studied in fields applied along the a axis. A refinement of the magnetic structure using neutron diffraction data in the SF phase reveals that the spins reorient from being parallel...

  8. Surface magnetic phase transitions in Dy/Lu superlattices

    International Nuclear Information System (INIS)

    Goff, J.P.; Sarthour, R.S.; Micheletti, C.; Langridge, S.; Wilkins, C.J.T.; Ward, R.C.C.; Wells, M.R.

    1999-01-01

    Dy/Lu superlattices comprising ferromagnetic Dy blocks coupled antiferromagnetically across the Lu blocks may be modelled as a chain of XY spins with antiferromagnetic exchange and six-fold anisotropy. We have calculated the stable magnetic phases for the cases of large anisotropy and a field applied along an easy direction. For an infinite chain an intermediate phase (1, 5,...) is predicted, where the notation gives the angle between the moment and the applied field in units of π/3. Furthermore, the effects of surface reconstruction are determined for finite chains. A [Dy 20 Lu 12 ] 20 superlattice has been studied using bulk magnetization and polarized neutron reflectivity. The (1, 5,...) phase has been identified and the results provide direct evidence in support of the theoretical predictions. Dipolar forces are shown to account for the magnitude of the observed exchange coupling. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  9. Phase locking of vortex cores in two coupled magnetic nanopillars

    Directory of Open Access Journals (Sweden)

    Qiyuan Zhu

    2014-11-01

    Full Text Available Phase locking dynamics of the coupled vortex cores in two identical magnetic spin valves induced by spin-polarized current are studied by means of micromagnetic simulations. Our results show that the available current range of phase locking can be expanded significantly by the use of constrained polarizer, and the vortices undergo large orbit motions outside the polarization areas. The effects of polarization areas and dipolar interaction on the phase locking dynamics are studied systematically. Phase locking parameters extracted from simulations are discussed by theoreticians. The dynamics of vortices influenced by spin valve geometry and vortex chirality are discussed at last. This work provides deeper insights into the dynamics of phase locking and the results are important for the design of spin-torque nano-oscillators.

  10. Creation and Annihilation of Skyrmions in the Frustrated Magnets with Competing Exchange Interactions.

    Science.gov (United States)

    Hu, Yong; Chi, Xiaodan; Li, Xuesi; Liu, Yan; Du, An

    2017-11-22

    In triangular-lattice magnets, the coexistence of third-neighbor antiferromagnetic and nearest-neighbor ferromagnetic exchange interactions can induce rich magnetic phases including noncoplanar skyrmion crystals. Based on Monte Carlo simulation, we studied the dependence of magnetic phase transition on exchange interaction strength. Under the consideration of uniaxial anisotropy and magnetic field both perpendicular to the film plane, a large antiferromagnetic exchange interaction induces a high frustration. When the value of antiferromagnetic exchange interaction is one and a half times larger than the ferromagnetic one, a magnetic phase composed of canting spin stripes, never observed in the chiral magnets, forms. Interestingly, different canting spin stripes along three 120 degree propagation directions may coexist randomly in a magnetic phase, attesting that the canting spin stripes are three-fold degenerate states akin to helices and the multiple state of canting spin stripes is a circular configuration with zero skyrmion charge number. Moreover, skyrmions and antiskyrmions can be observed simultaneously in the configuration at the low temperature nearly close to 0 K, and their configuration and diameter properties are discussed. Finally, the mechanisms of skyrmion creation and annihilation are properly interpreted by comparing exchange and Zeeman energy terms.

  11. Synthesis and magnetic properties of single phase titanomagnetites

    Energy Technology Data Exchange (ETDEWEB)

    Schoenthal, W., E-mail: wms@andrew.cmu.edu; Liu, X.; Cox, T.; Laughlin, D. E.; McHenry, M. E. [Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Mesa, J. L.; Diaz-Michelena, M. [Instituto Nacional de Tecnica Aeroespacial, Madrid (Spain); Maicas, M. [Universidad Politecnica de Madrid, ISOM-ETSIT, Madrid (Spain)

    2014-05-07

    The focus of this paper is the study of cation distributions and resulting magnetizations in titanomagnetites (TMs), (1−x)Fe{sub 3}O{sub 4−x}Fe{sub 2}TiO{sub 4} solid solutions. TM remnant states are hypothesized to contribute to planetary magnetic field anomalies. This work correlates experimental data with proposed models for the TM pseudobinary. Improved synthesis procedures are reported for single phase Ulvöspinel (Fe{sub 2}TiO{sub 4}), and TM solid solutions were made using solid state synthesis techniques. X-ray diffraction and scanning electron microscopy show samples to be single phase solid solutions. M-H curves of TM75, 80, 85, 90, and 95 (TMX where X = at. % of ulvöspinel) were measured using a Physical Property Measurement System at 10 K, in fields of 0 to 8 T. The saturation magnetization was found to be close to that predicted by the Neel model for cation distribution in TMs. M-T curves of the remnant magnetization were measured from 10 K to 350 K. The remnant magnetization was acquired at 10 K by applying an 8 T field and then releasing the field. Experimental Neel temperatures are reported for samples in the Neel model ground state.

  12. Magnetic-coupled phase anomaly in mixed-phase BiFeO3 thin films

    Directory of Open Access Journals (Sweden)

    Yen-Chin Huang

    2017-08-01

    Full Text Available The rich phase diagram of rhombohedral (R-like and tetragonal (T-like monoclinic polymorph in strained BiFeO3 (BFO films brings on various functionalities. Finding correlations of physical ordering parameters in this system is generally difficult because T-like and R-like phases are undistinguishable in many aspects. In this study, the magnetic-coupled structural transitions of the mixed-phase BFO at low temperatures were investigated by atomic force microscopy (AFM, X-ray diffraction (XRD, and Raman spectroscopy. To resolve the complexity resulted from the similarity between T-like and R-like phases, we analyzed the Raman spectra on a micro-scale region with various T/R ratios, which is in situ manipulated by an AFM tip carrying a dc bias. Phonons of T-like and R-like phases were thus successfully separated. Based on temperature-dependent XRD and resolved Raman spectra, we observed two isostructural transitions at around 225 K and 150 K, and they are strongly correlated with the magnetic ordering in the mixed-phase BFO film. Moreover, through the effective spin-lattice coupling, the evolution of the T/R polymorph is changed by the magnetic cooling process at low temperatures. This study provides a pathway to modulate phonon behaviors by magnetic fields in a highly strained system.

  13. Effect of atomic disorder on the magnetic phase separation.

    Science.gov (United States)

    Groshev, Andrey; Arzhnikov, Anatoly

    2018-03-27

    The effect of disorder on the magnetic phase separation between the antiferomagnetic and incommensurate helical (Q, Q) and (Q, π) phases is investigated. The study is based on the quasi-two-dimensional single-band Hubbard model in the presence of atomic disorder (the t - t' Anderson-Hubbard model). A model of binary alloy disorder is considered, in which the disorder is determined by the difference in energy between the host and impurity atomic levels at a fixed impurity concentration. The problem is solved within the theory of functional integration in static approximation. Magnetic phase diagrams are obtained as functions of the temperature, the number of electrons and impurity concentration with allowance for phase separation. It is shown that for the model parameters chosen, the disorder caused by impurities whose atomic-level energy is greater than that of the host atomic levels, leads to qualitative changes in the phase diagram of the impurity-free system. In the opposite case, only quantitative changes occur. The peculiarities of the effect of disorder on the phase separation regions of the quasi-two-dimensional Hubbard model are discussed. . © 2018 IOP Publishing Ltd.

  14. Berry-Phase Blockade in Single-Molecule Magnets

    Science.gov (United States)

    González, Gabriel; Leuenberger, Michael N.

    2007-06-01

    We formulate the problem of electron transport through a single-molecule magnet (SMM) in the Coulomb blockade regime taking into account topological interference effects for the tunneling of the large spin of a SMM. The interference originates from spin Berry phases associated with different tunneling paths. We show that, in the case of incoherent spin states, it is essential to place the SMM between oppositely spin-polarized source and drain leads in order to detect the spin tunneling in the stationary current, which exhibits topological zeros as a function of the transverse magnetic field.

  15. Discrete modes of a ferromagnetic stripe dipolarly coupled to a ferromagnetic film: a Brillouin light scattering study

    International Nuclear Information System (INIS)

    Gubbiotti, G; Tacchi, S; Carlotti, G; Ono, T; Roussigne, Y; Tiberkevich, V S; Slavin, A N

    2007-01-01

    Spin wave excitations in a magnetic structure consisting of a series of long permalloy stripes of a rectangular cross section magnetized along the stripe length and situated above a continuous permalloy film are studied both experimentally and theoretically. Stripes and continuous film are coupled by dipole-dipole interaction across 10 nm thick Cu spacers. Experimental measurements made using the Brillouin light scattering technique (with the light wavevector oriented along the stripe width) provide evidence for one dispersive spin wave mode associated with the continuous film and several discrete non-dispersive modes resonating within the finite width of the stripes. To interpret the experimental spectra, an analytic theory based on the spin wave formalism for finite-width magnetic stripes has been developed, achieving a good qualitative and partly quantitative description of the experimentally observed spin wave spectrum of the system. In particular, it is explained why the presence of a continuous magnetic film near the magnetic stripe leads to a substantial decrease of the frequencies of the discrete dipolar spin wave modes localized within the stripes. A more quantitative description of the measured frequencies and of the spatial profiles of the spin wave eigenmodes has been obtained by numerical calculations performed using a finite element method

  16. A Statistical Study of Magnetic Strom Recovery Phase: Preliminary Results

    Directory of Open Access Journals (Sweden)

    D.-Y. Lee

    2001-06-01

    Full Text Available A statistical study has been performed of the magnetic storm recovery phase using the Dst index for 102 storm events in the interval January 1996 to December 1998. In 43 cases (or 42% out of our 102 events, the recovery phase exhibits fast recovery (taking about 8 hours or less at its initial stage or for the entire recovery period. Since this fast recovery can be explained by the fast charge exchange loss of O+ ions which mostly come from the ionosphere, and since a fraction of H+ ions is of ionospheric origin as well, our statistical result supports the view that the source of ring current ions in many magnetic storms can be terrestrial.

  17. Berry-phase blockade in single-molecule magnets

    OpenAIRE

    Gonzalez, Gabriel; Leuenberger, Michael N.

    2006-01-01

    We formulate the problem of electron transport through a single-molecule magnet (SMM) in the Coulomb blockade regime taking into account topological interference effects for the tunneling of the large spin of a SMM. The interference originates from spin Berry phases associated with different tunneling paths. We show that in the case of incoherent spin states it is essential to place the SMM between oppositely spin-polarized source and drain leads in order to detect the spin tunneling in the s...

  18. Magnetic-field-induced suppression of the amorphous blue phase.

    Science.gov (United States)

    Challa, P K; Sprunt, S N; Jákli, A; Gleeson, J T

    2014-01-01

    We present magneto-optical measurements on two liquid crystals that exhibit a wide temperature-range amorphous blue phase (BPIII). Magnetic fields up to 25 T are found to suppress the onset of BPIII in both materials by almost 1 °C. This effect appears to increase nonlinearly with the field strength. The effect of high fields on established BPIIIs is also reported, in which we find significant hysteresis and very slow dynamics. Possible explanations of these results are discussed.

  19. Structural and magnetic phase formation in nanophase brass–iron ...

    Indian Academy of Sciences (India)

    November 2005 physics pp. 847–854. Structural and magnetic phase formation in nanophase brass–iron electron compounds. A K MISHRA and C BANSAL. School of Physics, University of Hyderabad, Hyderabad 500 046, India. E-mail: cbsp@uohyd.ernet.in. Abstract. Starting with Cu0.65Zn0.35 with an e/a ratio of 1.35 we ...

  20. The structural and magnetic properties of dual phase cobalt ferrite.

    Science.gov (United States)

    Gore, Shyam K; Jadhav, Santosh S; Jadhav, Vijaykumar V; Patange, S M; Naushad, Mu; Mane, Rajaram S; Kim, Kwang Ho

    2017-05-31

    The bismuth (Bi 3+ )-doped cobalt ferrite nanostructures with dual phase, i.e. cubic spinel with space group Fd3m and perovskite with space group R3c, have been successfully engineered via self-ignited sol-gel combustion route. To obtain information about the phase analysis and structural parameters, like lattice constant, Rietveld refinement process is applied. The replacement of divalent Co 2+ by trivalent Bi 3+ cations have been confirmed from energy dispersive analysis of the ferrite samples. The micro-structural evolution of cobalt ferrite powders at room temperature under various Bi 3+ doping levels have been identified from the digital photoimages recorded using scanning electron microscopy. The hyperfine interactions, like isomer shift, quadrupole splitting and magnetic hyperfine fields, and cation distribution are confirmed from the Mossbauer spectra. Saturation magnetization is increased with Bi 3+ -addition up to x = 0.15 and then is decreased when x = 0.2. The coercivity is increased from 1457 to 2277 G with increasing Bi 3+ -doping level. The saturation magnetization, coercivity and remanent ratio for x = 0.15 sample is found to be the highest, indicating the potential of Bi 3+ -doping in enhancing the magnetic properties of cobalt ferrite.

  1. Phase diagrams and switching of voltage and magnetic field in dilute magnetic semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Escobedo, R. [Departamento de Matematica Aplicada y Ciencias de la Computacion, Universidad de Cantabria, 39005 Santander (Spain); Carretero, M.; Bonilla, L.L. [G. Millan Institute, Fluid Dynamics, Nanoscience and Industrial Maths., Universidad Carlos III de Madrid, 28911 Leganes (Spain); Unidad Asociada al Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain); Platero, G. [Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain)

    2010-04-15

    The response of an n-doped dc voltage biased II-VI multi-quantum well dilute magnetic semiconductor nanostructure having its first well doped with magnetic (Mn) impurities is analyzed by sweeping wide ranges of both the voltage and the Zeeman level splitting induced by an external magnetic field. The level splitting versus voltage phase diagram shows regions of stable self-sustained current oscillations immersed in a region of stable stationary states. Transitions between stationary states and self-sustained current oscillations are systematically analyzed by both voltage and level splitting abrupt switching. Sudden voltage or/and magnetic field changes may switch on current oscillations from an initial stationary state, and reciprocally, current oscillations may disappear after sudden changes of voltage or/and magnetic field changes into the stable stationary states region. The results show how to design such a device to operate as a spin injector and a spin oscillator by tuning the Zeeman splitting (through the applied external magnetic field), the applied voltage and the sample configuration parameters (doping density, barrier and well widths, etc.) to select the desired stationary or oscillatory behavior. Phase diagram of Zeeman level splitting {delta} vs. dimensionless applied voltage {phi} for N = 10 QWs. White region: stable stationary states; black: stable self-sustained current oscillations. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Magnetic Properties of Two-Phase Composite Magnetic Material and Its Application to Electrical Equipment

    Directory of Open Access Journals (Sweden)

    Zhiwei CHEN

    2015-11-01

    Full Text Available A detailed research on the magnetic properties, preparation, and application of two-phase composite magnetic material was conducted in this paper. Firstly, in order to obtain the characteristics of high remanence and low coercivity, a micro field mathematical model of hysteresis was established and the magnetization model of this material was determined on the basis of micro magnetic theory. Secondly, the relationship between remanence and coercivity was analyzed and the preparation technology of the material was proposed from the perspective of the elemental composition, the heat treatment, and the other steps. Finally, after mastering the magnetization characteristic, conversion and control mechanism of the material, a new power transformer with function of DC bias compensation based on the two-phase composite magnetic material was proposed. The simulation and experimental results showed that the transformer could achieve a good compensation for the DC bias problem by using material remanence, which provides intelligent and energy-saving electrical equipment for the electric network safe operation.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9707

  3. Surface and magnetic characteristics of Ni-Mn-Ga/Si (100) thin film

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S. Vinodh; Pandyan, R. Kodi; Mahendran, M., E-mail: manickam-mahendran@tce.edu, E-mail: perialangulam@gmail.com [Smart Materials Lab, Department of Physics, Thiagarajar College of Engineering, Madurai – 625 015 (India); Raja, M. Manivel [Defence Metallurgical Research Laboratory, Hyderabad – 500 058 (India); Pandi, R. Senthur [School of Advanced Sciences, VIT University, Vellore – 632 014 (India)

    2016-05-23

    Polycrystalline Ni-Mn-Ga thin films have been deposited on Si (100) substrate with different film thickness. The influence of film thickness on the phase structure and magnetic domain of the films has been examined by scanning electron microscope, atomic force microscopy and magnetic force microscopy. Analysis of structural parameters indicates that the film at lower thickness exhibits the coexistence of both austenite and martensite phase, whereas at higher thickness L1{sub 2} cubic non magnetic phase is noticed. The grains size and the surface roughness increase along with the film thickness and attain the maximum of 45 nm and 34.96 nm, respectively. At lower film thickness, the magnetic stripe domain is found like maze pattern with dark and bright images, while at higher thickness the absence of stripe domains is observed. The magnetic results reveal that the films strongly depend on their phase structure and microstructure which influence by the film thickness.

  4. Improving striping operations through system optimization.

    Science.gov (United States)

    2015-09-01

    Striping operations generate a significant workload for Missouri Department of Transportation (MoDOT) maintenance : operations. The requirement for each striping crew to replenish its stock of paint and other consumable items from a bulk storage : fa...

  5. Current-induced rotational torques in the skyrmion lattice phase of chiral magnets

    NARCIS (Netherlands)

    Everschor, K.; Garst, M.; Duine, R.A.|info:eu-repo/dai/nl/304830127; Rosch, A.

    2011-01-01

    In chiral magnets without inversion symmetry, the magnetic structure can form a lattice of magnetic whirl lines, a two-dimensional skyrmion lattice, stabilized by spin-orbit interactions in a small range of temperatures and magnetic fields. The twist of the magnetization within this phase gives rise

  6. Effect of magnetic soft phase on the magnetic properties of bulk anisotropic Nd2Fe14B/α-Fe nanocomposite permanent magnets

    Science.gov (United States)

    Li, Yuqing; Yue, Ming; Zhao, Guoping; Zhang, Hongguo

    2018-01-01

    The effects of soft phase with different particle sizes and distributions on the Nd2Fe14B/α-Fe nanocomposite magnets have been studied by the micro-magnetism simulation. The calculated results show that smaller and/or scattered distribution of soft phase can benefit to the coercivity (H ci) of the nanocomposite magnets. The magnetization moment evolution during magnetic reversal is systematically analyzed. On the other hand, magnetic properties of anisotropic Nd–Fe–B/α-Fe nanocomposite magnets prepared by hot pressing and hot deformation methods also provide evidences for the calculated results.

  7. Quantum phases for a charged particle and electric/magnetic dipole in an electromagnetic field

    Science.gov (United States)

    Kholmetskii, Alexander; Yarman, Tolga

    2017-11-01

    We point out that the known quantum phases for an electric/magnetic dipole moving in an electromagnetic field must be composed from more fundamental quantum phases emerging for moving elementary charges. Using this idea, we have found two new fundamental quantum phases, next to the known magnetic and electric Aharonov-Bohm phases, and discuss their general properties and physical meaning.

  8. Anisotropic Exchange Interaction in the Conical Magnetic Phase of Erbium

    DEFF Research Database (Denmark)

    Jensen, J.

    1974-01-01

    From a general two ion spin Hamiltonian, an expression is deduced for the energies of spin waves propagating in a hexagonal solid in which the magnetic moments are ordered in a conical or helical structure. The spin wave dispersion relation in the c direction of Er in its conical magnetic phase...... at 4.5K, which has been studied by Nicklow et al (1971) is reanalysed. In this analysis an alternative kind of anisotropic coupling between the total angular moments (Ji and Jj) on the sites i and j is introduced which is proportional to the following combination of Racah operators: O2, -2(Ji), O2, -2......(Jj), expressed with respect to a coordinate system with the z axis along the c direction. The resulting anisotropy (both the constant and the q dependent part) is reduced by an order of magnitude in comparison with that deduced by Nicklow et al (1971). The constant anisotropy is found to be equal...

  9. Magnetic phase transitions with incommensurate structures in systems with coupled order parameters

    International Nuclear Information System (INIS)

    Izyumov, Yu.A.; Laptev, V.M.; Petrov, S.B.

    1984-01-01

    Modulated magnetic phases are investigated for the case when symmetry does not allow linear by gradients Lifshits invariants and magnetic momenta are converted by two irreducible representations. Possible phase diagrams with participation of incommensurable phases are plotted on the base of Ginsburg-Landau functional for 2 bound parameters of the order. The role of the highest harmonics in spatial distribution of the order parameters is clarified on the example of magnetic phase transitions in Er

  10. Overview of the phase diagram of ionic magnetic colloidal dispersions

    International Nuclear Information System (INIS)

    Cousin, F.; Dubois, E.; Cabuil, V.; Boue, F.; Perzynski, R.

    2001-01-01

    We study ionic magnetic colloidal dispersions, which are constituted of γ-Fe 2 O 3 nanoparticles dispersed in water, and stabilized with electrostatic interparticle repulsion. The phase diagram PV versus Φ (P: osmotic pressure, V: particle volume, Φ: particle volume fraction) is explored, especially in the range of high Π and high Φ. The osmotic pressure P of the colloidal dispersion is known either by a measurement either because it is imposed during the sample preparation by osmotic compression. The structure of the colloidal dispersion is determined from Small Angle Neutron Scattering. Two regimes can be distinguished. At high pressure, fluid and solid phases can exist. Their structure is governed by strong electrostatic repulsion, the range of which is here evaluated. At low pressure, gas, liquid and glassy solids can exist. Their structure results from a sticky hard sphere potential. (author)

  11. Nanocrystalline Fe-Pt alloys. Phase transformations, structure and magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Lyubina, J.V.

    2006-12-21

    This work has been devoted to the study of phase transformations involving chemical ordering and magnetic properties evolution in bulk Fe-Pt alloys composed of nanometersized grains. Nanocrystalline Fe{sub 100-x}Pt{sub x} (x=40-60) alloys have been prepared by mechanical ball milling of elemental Fe and Pt powders at liquid nitrogen temperature. The as-milled Fe-Pt alloys consist of {proportional_to} 100 {mu}m sized particles constituted by randomly oriented grains having an average size in the range of 10-40 nm. Depending on the milling time, three major microstructure types have been obtained: samples with a multilayer-type structure of Fe and Pt with a thickness of 20-300 nm and a very thin (several nanometers) A1 layer at their interfaces (2 h milled), an intermediate structure, consisting of finer lamellae of Fe and Pt (below approximately 100 nm) with the A1 layer thickness reaching several tens of nanometers (4 h milled) and alloys containing a homogeneous A1 phase (7 h milled). Subsequent heat treatment at elevated temperatures is required for the formation of the L1{sub 0} FePt phase. The ordering develops via so-called combined solid state reactions. It is accompanied by grain growth and thermally assisted removal of defects introduced by milling and proceeds rapidly at moderate temperatures by nucleation and growth of the ordered phases with a high degree of the long-range order. In a two-particle interaction model elaborated in the present work, the existence of hysteresis in recoil loops has been shown to arise from insufficient coupling between the low- and the high-anisotropy particles. The model reveals the main features of magnetisation reversal processes observed experimentally in exchange-coupled systems. Neutron diffraction has been used for the investigation of the magnetic structure of ordered and partially ordered nanocrystalline Fe-Pt alloys. (orig.)

  12. A Partially Magnetized Ferrite LTCC-Based SIW Phase Shifter for Phased Array Applications

    KAUST Repository

    Ghaffar, Farhan A.

    2015-06-01

    The theory and design of a half-mode substrate-integrated waveguide ferrite low-temperature cofired ceramic-based phase shifter are presented in this paper. Unlike typical ferrite-based designs, the biasing is done through embedded windings in a multi-layer substrate that not only obviates the requirement of bulky electromagnets, but also prevents loss of bias fields at the air-to-ferrite interface. The phase shifter is operated in the partially magnetized state of ferrite substrate. Through the combined effect of embedded windings, half-mode waveguide operation, and partially magnetized state, the required bias fields have been reduced by 90% as compared with conventional ferrite-based designs employing electromagnets. A complete analytical model, backed up by electromagnetic simulations and measured results from a prototype, is presented in this paper. The fabricated prototype demonstrates a phase shift of 83.2° at a center frequency of 13.1 GHz and a figure of merit of 83.2°/dB. As a proof-of-concept, the proposed phase shifter design is monolithically integrated with a two-element antenna array to demonstrate a measured beam steering of 30°. The phase shifter design is highly efficient in terms of required bias fields, and it has a small form factor and can be easily integrated with other electronic components and systems. © 1965-2012 IEEE.

  13. Disorder induced stripes in d-wave superconductors

    Science.gov (United States)

    Schmid, Markus; Loder, Florian; Kampf, Arno P.; Kopp, Thilo

    2013-07-01

    Stripe phases are observed experimentally in several copper-based high-Tc superconductors near 1/8 hole doping. However, the specific characteristics may vary depending on the degree of dopant disorder and the presence or absence of a low-temperature tetragonal phase. On the basis of a Hartree-Fock decoupling scheme for the t-J model, we discuss the diverse behavior of stripe phases. In particular, the effect of inhomogeneities is investigated in two distinctly different parameter regimes which are characterized by the strength of the interaction. We observe that small concentrations of impurities or vortices pin the unidirectional density waves, and dopant disorder is capable of stabilizing a stripe phase in parameter regimes where homogeneous phases are typically favored in clean systems. The momentum-space results exhibit universal features for all coexisting density-wave solutions, nearly unchanged even in strongly disordered systems. These coexisting solutions feature generically a full energy gap and a particle-hole asymmetry in the density of states.

  14. Magnetic transition phase diagram of cobalt clusters electrodeposited on HOPG: Experimental and micromagnetic modelling study

    Energy Technology Data Exchange (ETDEWEB)

    Rivera, M., E-mail: mrivera@fisica.unam.m [Imperial College London, Department of Chemistry, South Kensington Campus, London SW7 2AZ (United Kingdom); Rios-Reyes, C.H. [Universidad Autonoma Metropolitana-Azcapotzalco, Departamento de Materiales, Av. San Pablo 180, Col. Reynosa Tamaulipas, C.P. 02200, Mexico D.F. (Mexico); Universidad Autonoma del Estado de Hidalgo, Centro de Investigaciones Quimicas, Mineral de la Reforma, Hidalgo, C.P. 42181 (Mexico); Mendoza-Huizar, L.H. [Universidad Autonoma del Estado de Hidalgo, Centro de Investigaciones Quimicas, Mineral de la Reforma, Hidalgo, C.P. 42181 (Mexico)

    2011-04-15

    The magnetic transition from mono- to multidomain magnetic states of cobalt clusters electrodeposited on highly oriented pyrolytic graphite electrodes was studied experimentally using Magnetic Force Microscopy. From these images, it was found that the critical size of the magnetic transition is dominated by the height rather than the diameter of the aggregate. This experimental behavior was found to be consistent with a theoretical single-domain ferromagnetic model that states that a critical height limits the monodomain state. By analyzing the clusters magnetic states as a function of their dimensions, magnetic exchange constant and anisotropy value were obtained and used to calculate other magnetic properties such as the exchange length, magnetic wall thickness, etc. Finally, a micromagnetic simulation study correctly predicted the experimental magnetic transition phase diagram. - Research highlights: > Electrodeposition of cobalt clusters. > Mono to multidomain magnetic transition. > Magnetic phase diagram.

  15. Magnetic transition phase diagram of cobalt clusters electrodeposited on HOPG: Experimental and micromagnetic modelling study

    International Nuclear Information System (INIS)

    Rivera, M.; Rios-Reyes, C.H.; Mendoza-Huizar, L.H.

    2011-01-01

    The magnetic transition from mono- to multidomain magnetic states of cobalt clusters electrodeposited on highly oriented pyrolytic graphite electrodes was studied experimentally using Magnetic Force Microscopy. From these images, it was found that the critical size of the magnetic transition is dominated by the height rather than the diameter of the aggregate. This experimental behavior was found to be consistent with a theoretical single-domain ferromagnetic model that states that a critical height limits the monodomain state. By analyzing the clusters magnetic states as a function of their dimensions, magnetic exchange constant and anisotropy value were obtained and used to calculate other magnetic properties such as the exchange length, magnetic wall thickness, etc. Finally, a micromagnetic simulation study correctly predicted the experimental magnetic transition phase diagram. - Research highlights: → Electrodeposition of cobalt clusters. →Mono to multidomain magnetic transition. → Magnetic phase diagram.

  16. Magnetic phase diagram of superantiferromagnetic TbCu2 nanoparticles

    Science.gov (United States)

    Echevarria-Bonet, C.; Rojas, D. P.; Espeso, J. I.; Rodríguez Fernández, J.; de la Fuente Rodríguez, M.; Fernández Barquín, L.; Rodríguez Fernández, L.; Gorria, P.; Blanco, J. A.; Fdez-Gubieda, M. L.; Bauer, E.; Damay, F.

    2015-12-01

    The structural state and static and dynamic magnetic properties of TbCu2 nanoparticles are reported to be produced by mechanical milling under inert atmosphere. The randomly dispersed nanoparticles as detected by TEM retain the bulk symmetry with an orthorhombic Imma lattice and Tb and Cu in the 4e and 8h positions, respectively. Rietveld refinements confirm that the milling produces a controlled reduction of particle sizes reaching ≃6 nm and an increase of the microstrain up to ≃0.6%. The electrical resistivity indicates a metallic behavior and the presence of a magnetic contribution to the electronic scattering which decreases with milling times. The dc-susceptibility shows a reduction of the Néel transition (from 49 K to 43 K) and a progressive increase of a peak (from 9 K to 15 K) in the zero-field-cooled magnetization with size reduction. The exchange anisotropy is very weak (a bias field of ≃30 Oe) and is due to the presence of a disordered (thin) shell coupled to the antiferromagnetic core. The dynamic susceptibility evidences a critical slowing down in the spin-disordered state for the lowest temperature peak associated with a spin glass-like freezing with a tendency of zv and β exponents to increase when the size becomes 6 nm (zv≃ 6.6 and β ≃ 0.85 ). A Rietveld analysis of the neutron diffraction patterns 1.8≤slant T≤slant 60 K, including the magnetic structure determination, reveals that there is a reduction of the expected moment (≃80%), which must be connected to the presence of the disordered particle shell. The core magnetic structure retains the bulk antiferromagnetic arrangement. The overall interpretation is based on a superantiferromagnetic behavior which at low temperatures coexists with a canting of surface moments and a mismatch of the antiferromagnetic sublattices of the nanoparticles. We propose a novel magnetic phase diagram where changes are provoked by a combination of the decrease of size and the increase of

  17. Magnetic phase transitions in Er7Rh3 studied on single crystals

    International Nuclear Information System (INIS)

    Tsutaoka, Takanori; Obata, Keisuke; Cheyvuth, Seng; Koyama, Keiichi

    2014-01-01

    Highlights: • Magnetic and electrical properties of Er 7 Rh 3 were studied on single crystals. • The magnetic phase diagram along the c-axis was constructed. • The field-induced magnetic transitions in Er 7 Rh 3 can be explained by the magnetic structure with two magnetic propagation vectors. • The anomalies of electrical resistivity can also be described by the magnetic structure in Er 7 Rh 3 . - Abstract: Magnetic phase transitions in Er 7 Rh 3 with the Th 7 Fe 3 type hexagonal structure have been studied on single crystals by measuring magnetization, magnetic susceptibility and electrical resistivity. Er 7 Rh 3 possesses antiferromagnetic state below T N = 13 K. In the ordered state, the two successive magnetic transitions at T t1 = 6.2 K and T t2 = 4.5 K were observed. Several field-induced magnetic transitions were also observed along the a- and c-axes below T N ; magnetic field H – temperature T phase diagram along the c-axis was constructed. The field-induced magnetic transitions in Er 7 Rh 3 can be explained by the magnetic structure with two magnetic propagation vectors which were derived by the previous neutron diffraction studies. Electrical resistivity shows humps just below the magnetic transition temperatures, T N and T t1 due to the super-zone gap formation at the Fermi level; these anomalies can also be described by the magnetic structure changes in Er 7 Rh 3

  18. Evidence for a Magnetic Collapse in the Epsilon Phase of Solid Oxygen

    International Nuclear Information System (INIS)

    Goncharenko, Igor N.

    2005-01-01

    Solid oxygen is the only elementary molecular magnet. Under the very high pressure of 96 GPa oxygen transforms into a metal and a superconductor. Theory predicts a nonmagnetic state occurring before the transition into the superconducting ξ phase. Nevertheless, until now there was no direct evidence of a magnetic collapse in high-pressure oxygen. For the first time direct information is provided on magnetic properties of the ε phase, which is sandwiched between the antiferromagnetic δ phase and the superconducting ξ phase. We used magnetic neutron diffraction. The data show that the long-range magnetic order disappears at the δ-ε transition. The magnetic collapse occurs at P≅8 GPa, far below the pressure of the insulator-metal (superconductor) transition. The collapse is preceded by a decrease in temperature of transition towards the long-range magnetically ordered state (T LRO ) in the δ phase, at P=7.6 GPa

  19. Evidence for a magnetic collapse in the epsilon phase of solid oxygen.

    Science.gov (United States)

    Goncharenko, Igor N

    2005-05-27

    Solid oxygen is the only elementary molecular magnet. Under the very high pressure of 96 GPa oxygen transforms into a metal and a superconductor. Theory predicts a nonmagnetic state occurring before the transition into the superconducting xi phase. Nevertheless, until now there was no direct evidence of a magnetic collapse in high-pressure oxygen. For the first time direct information is provided on magnetic properties of the epsilon phase, which is sandwiched between the antiferromagnetic delta phase and the superconducting xi phase. We used magnetic neutron diffraction. The data show that the long-range magnetic order disappears at the delta-epsilon transition. The magnetic collapse occurs at P approximately equal to 8 GPa, far below the pressure of the insulator-metal (superconductor) transition. The collapse is preceded by a decrease in temperature of transition towards the long-range magnetically ordered state (T(LRO)) in the delta phase, at P = 7.6 GPa.

  20. A Phase Current Reconstruction Approach for Three-Phase Permanent-Magnet Synchronous Motor Drive

    Directory of Open Access Journals (Sweden)

    Hao Yan

    2016-10-01

    Full Text Available Three-phase permanent-magnet synchronous motors (PMSMs are widely used in renewable energy applications such as wind power generation, tidal energy and electric vehicles owing to their merits such as high efficiency, high precision and high reliability. To reduce the cost and volume of the drive system, techniques of reconstructing three-phase current using a single current sensor have been reported for three-phase alternating current (AC control system using the power converts. In existing studies, the reconstruction precision is largely influenced by reconstructing dead zones on the Space Vector Pulse Width Modulation (SVPWM plane, which requires other algorithms to compensate either by modifying PWM modulation or by phase-shifting of the PWM signal. In this paper, a novel extended phase current reconstruction approach for PMSM drive is proposed. Six novel installation positions are obtained by analyzing the sampling results of the current paths between each two power switches. By arranging the single current sensor at these positions, the single current sensor is sampled during zero voltage vectors (ZVV without modifying the PWM signals. This proposed method can reconstruct the three-phase currents without any complex algorithms and is available in the sector boundary region and low modulation region. Finally, this method is validated by experiments.

  1. pi-phase magnetism in ferromagnetic-superconductor superlattices

    CERN Document Server

    Khusainov, M G; Proshin, Y N

    2001-01-01

    The Larkin-Ovchinnikov-Fylde-Ferrel new 0 pi- and pi pi-states are forecasted for the ferromagnetic metal/superconductor superlattices with antiferromagnetic magnetization orientation in the neighbouring layers. The above-mentioned states are characterized under certain conditions by higher critical temperature T sub c as compared to the earlier known LOFF 00- and pi 0-states with the FM-layers ferromagnetic ordering. It is shown that the nonmonotonous behavior of the T sub c of the FM/S superlattices by the thickness of the S-layers lower than the d sub s suppi value is connected with the cascades of the 0 pi-pi pi-0 pi phase transitions. The character of the T sub c oscillations by the d sub s > d sub s suppi is related to the 00-pi 0-00 transitions. The logical elements of the new type, combining the advantages of the superconducting and magnetic information recording in one sample are proposed on the basis of the FM/S superlattices

  2. Magnetic properties of anyonic systems in a normal phase

    International Nuclear Information System (INIS)

    Aronov, I.E.; Naftulin, S.A.

    1992-08-01

    We apply the concept of fractional statistics to the two-dimensional conductors. The effective Lagrangian of an external magnetic field in anyon medium at finite temperature and density is presented. The diamagnetic response to the external field is studied at temperatures above T c (i.e. in the normal phase) for various values of external parameters. Oscillations of both thermodynamic (the de Haas - van Alphen effect) and kinetic (the Shubnikov - de Haas effect) quantities are re-examined. Numerous peculiarities arise from the fact that anyon systems possess a non-zero ''statistical'' flux Φ (which is known to be a manifestation of the spontaneous parity breakdown). The cyclotron resonance is suggested as a direct test on possible parity violation (which is the key point of anyonics). The cyclotron mass dependences on external parameters reported in a series of experimental articles (H. Kublbeck and J.P. Kotthaus, Phys. Rev. Lett. 35, 1019 (1975); G. Abstreiter, J.P. Kotthaus, J.F. Koch and G. Dorda, Phys. Rev. B14, 2480 (1976)) may be attributed to an unusual behaviour or magnetic permeability in anyon medium. (author). 20 refs, 2 figs

  3. 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.

  4. Magnetic properties of Gd5(Si1.5Ge2.5) near the temperature and magnetic field induced first order phase transition

    International Nuclear Information System (INIS)

    Levin, E.M.; Gschneidner, K.A.; Pecharsky, V.K.

    2001-01-01

    The temperature (from 5 to 300 K) and DC magnetic field (from 0 to 90 kOe) dependencies of the DC magnetization and magnetic susceptibility, and the temperature (from 5 to 350 K) dependency of the AC magnetic susceptibility of Gd 5 (Si 1.5 Ge 2.5 ) have been studied. The temperature and/or magnetic field induced magnetic phase transition in Gd 5 (Si 1.5 Ge 2.5 ) is a first order ferromagnet-paramagnet transition. The temperature of the magnetic transition in low AC magnetic field is 206 and 217 K for cooling and heating, respectively. The DC magnetic field increases the transition temperature by ∼0.36 K/kOe indicating that the paramagnetic phase can be reversibly transformed into the ferromagnetic phase. When the magnetic field is removed, the ferromagnetic phase transforms into the paramagnetic phase showing a large remanence-free hysteresis. The magnetic phase diagram based on the isothermal magnetic field dependence of the DC magnetization at various temperatures for Gd 5 (Si 1.5 Ge 2.5 ) is proposed. The magnetic field dependence of the magnetization in the vicinity of the first order phase transition shows evidence for the formation of a magnetically heterogeneous system in the volume of Gd 5 (Si 1.5 Ge 2.5 ) specimen where the magnetically ordered (ferromagnetic) and disordered (paramagnetic) phases co-exist

  5. Magnetism and phase transitions in LaCoO3

    Science.gov (United States)

    Durand, A. M.; Belanger, D. P.; Booth, C. H.; Ye, F.; Chi, S.; Fernandez-Baca, J. A.; Bhat, M.

    2013-09-01

    Neutron scattering and magnetometry measurements have been used to study phase transitions in LaCoO3 (LCO). For H ≤ 100 Oe, evidence for a ferromagnetic (FM) transition is observed at Tc ≈ 87 K. For 1 kOe ≤ H ≤ 60 kOe, no transition is apparent. For all H, Curie-Weiss analysis shows predominantly antiferromagnetic (AFM) interactions for T > Tc, but the lack of long-range AFM order indicates magnetic frustration. We argue that the weak ferromagnetism in bulk LCO is induced by lattice strain, as is the case with thin films and nanoparticles. The lattice strain is present at the bulk surfaces and at the interfaces between the LCO and a trace cobalt oxide phase. The ferromagnetic ordering in the LCO bulk is strongly affected by the Co-O-Co angle (γ), in agreement with recent band calculations which predict that ferromagnetic long-range order can only take place above a critical value, γC. Consistent with recent thin film estimations, we find γC = 162.8°. For γ > γC, we observe power-law behavior in the structural parameters. γ decreases with T until the critical temperature, To ≈ 37 K below To the rate of change becomes very small. For T angle above γC.

  6. Micromagnetic simulation of magnetic small-angle neutron scattering from two-phase nanocomposites

    International Nuclear Information System (INIS)

    Michels, Andreas; Erokhin, Sergey; Berkov, Dmitry; Gorn, Nataliya

    2014-01-01

    The recent development of a micromagnetic simulation methodology—suitable for multiphase magnetic nanocomposites—permits the computation of the magnetic microstructure and of the associated magnetic small-angle neutron scattering (SANS) cross section of these materials. In this review we summarize results on the micromagnetic simulation of magnetic SANS from two-phase nanocomposites. The decisive advantage of this approach resides in the possibility to scrutinize the individual magnetization Fourier contributions to the total magnetic SANS cross section, rather than their sum, which is generally obtained from the experiment. The procedure furnishes unique and fundamental information regarding magnetic neutron scattering from nanomagnets

  7. Micromagnetic simulation of magnetic small-angle neutron scattering from two-phase nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Michels, Andreas, E-mail: andreas.michels@uni.lu [Physics and Materials Science Research Unit, University of Luxembourg, 162A Avenue de la Faïencerie, L-1511 Luxembourg (Luxembourg); Erokhin, Sergey; Berkov, Dmitry; Gorn, Nataliya [INNOVENT Technology Development, Prüssingstraße 27B, D-07745 Jena (Germany)

    2014-01-15

    The recent development of a micromagnetic simulation methodology—suitable for multiphase magnetic nanocomposites—permits the computation of the magnetic microstructure and of the associated magnetic small-angle neutron scattering (SANS) cross section of these materials. In this review we summarize results on the micromagnetic simulation of magnetic SANS from two-phase nanocomposites. The decisive advantage of this approach resides in the possibility to scrutinize the individual magnetization Fourier contributions to the total magnetic SANS cross section, rather than their sum, which is generally obtained from the experiment. The procedure furnishes unique and fundamental information regarding magnetic neutron scattering from nanomagnets.

  8. Magnetic properties and phase evolution of sintered Nd-Fe-B magnets with intergranular addition of Pr–Co alloy

    International Nuclear Information System (INIS)

    Jin, Chaoxiang; Chen, Renjie; Yin, Wenzong; Tang, Xu; Wang, Zexuan; Ju, Jinyun; Lee, Don; Yan, Aru

    2016-01-01

    The magnetic properties, thermal stability and phase evolution of sintered Nd-Fe-B magnets with intergranular addition of Pr–Co were investigated. The thermal stabilities of coercivity and remanence were simultaneously enhanced without heavy rare earth elements, resulting from the partial substitution of Pr for Nd and Co for Fe in matrix phase, respectively. After Pr–Co addition, RE-rich phase reduced and new phases containing Pr and Co, such as (NdPr) (FeCo) 2 (NdPr) 3 (FeCo) and (NdPr) 2 (FeCo) 17 phases, were formed. With the increase of Pr–Co addition amount, intrinsic coercivity firstly decreased sharply which was mainly caused by the formation of soft ferromagnetic (NdPr) (FeCo) 2 phase, and subsequently presented a remarkable recovery induced by the formation of non-magnetic (NdPr) 3 (FeCo) phase and transformation of (NdPr) (FeCo) 2 phase from ferromagnetic to non-magnetic. Due to the reduction of matrix phase proportion, the remanence decreased monotonously after the addition of Pr–Co for more than 10 wt. %. - Highlights: • The improved thermal stabilities of coercivity and remanence were obtained. • An abnormal remarkable recovery of coercivity was found. • The evolution of Co-containing phases was clarified.

  9. Magnetic properties and phase evolution of sintered Nd-Fe-B magnets with intergranular addition of Pr–Co alloy

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Chaoxiang [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Enginnering, Chinese Academy of Sciences, Ningbo 315201 (China); Rare Earth Magnetic Materials Laboratory, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Chen, Renjie, E-mail: chenrj@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Enginnering, Chinese Academy of Sciences, Ningbo 315201 (China); Rare Earth Magnetic Materials Laboratory, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Yin, Wenzong; Tang, Xu; Wang, Zexuan; Ju, Jinyun [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Enginnering, Chinese Academy of Sciences, Ningbo 315201 (China); Rare Earth Magnetic Materials Laboratory, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Lee, Don [University of Dayton, Dayton OH (United States); Yan, Aru, E-mail: aruyan@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Enginnering, Chinese Academy of Sciences, Ningbo 315201 (China); Rare Earth Magnetic Materials Laboratory, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2016-06-15

    The magnetic properties, thermal stability and phase evolution of sintered Nd-Fe-B magnets with intergranular addition of Pr–Co were investigated. The thermal stabilities of coercivity and remanence were simultaneously enhanced without heavy rare earth elements, resulting from the partial substitution of Pr for Nd and Co for Fe in matrix phase, respectively. After Pr–Co addition, RE-rich phase reduced and new phases containing Pr and Co, such as (NdPr) (FeCo){sub 2} (NdPr){sub 3}(FeCo) and (NdPr){sub 2}(FeCo){sub 17} phases, were formed. With the increase of Pr–Co addition amount, intrinsic coercivity firstly decreased sharply which was mainly caused by the formation of soft ferromagnetic (NdPr) (FeCo){sub 2} phase, and subsequently presented a remarkable recovery induced by the formation of non-magnetic (NdPr){sub 3}(FeCo) phase and transformation of (NdPr) (FeCo){sub 2} phase from ferromagnetic to non-magnetic. Due to the reduction of matrix phase proportion, the remanence decreased monotonously after the addition of Pr–Co for more than 10 wt. %. - Highlights: • The improved thermal stabilities of coercivity and remanence were obtained. • An abnormal remarkable recovery of coercivity was found. • The evolution of Co-containing phases was clarified.

  10. Invasion of the striped mollusks

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    Introduced to this country only five years ago, the prolific zebra mussel has infested the Great Lakes and has already begun to move into fresh waters beyond the region. Dense populations in utility water systems have caused serious problems, reducing plant efficiency and blocking lines used for cooling and fire fighting. Experts say the striped mollusk has the potential to become the industry's worst biological problem, possibly affecting 70% of US power plants. While it appears that the invader is here to stay, EPRI and others continue to develop and refine techniques to control mussel growth

  11. Neutron scattering evidence for magnetic-field-driven abrut magnetic and structural transitions in a phase-separated manganite

    Czech Academy of Sciences Publication Activity Database

    Yaicle, C.; Martin, C.; Jirák, Zdeněk; Fauth, F.; André, G.; Suard, E.; Maignan, A.; Hardy, V.; Retoux, R.; Hervieu, M.

    2003-01-01

    Roč. 68, č. 22 (2003), s. 224412-1 - 224412-8 ISSN 0163-1829 Institutional research plan: CEZ:AV0Z1010914 Keywords : phase-separated manganite * magnetic and structural transitions * neutron scattering Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.962, year: 2003

  12. Phase-Field simulation of phase decomposition in Fe-Cr-Co alloy under an external magnetic field

    Science.gov (United States)

    Koyama, Toshiyuki; Onodera, Hidehiro

    2004-07-01

    Phase decomposition during isothermal aging of a Fe-Cr-Co ternary alloy under an external magnetic field is simulated based on the phase-field method. In this simulation, since the Gibbs energy available from the thermodynamic CALPHAD database of the equilibrium phase diagram is employed as a chemical free energy, the present calculation provides the quantitative microstructure changes directly linked to the phase diagram. The simulated microstructure evolution demonstrates that the lamella like microstructure elongated along the external magnetic field is evolved with the progress of aging. The morphological and temporal developments of the simulated microstructures are in good agreement with experimental results that have been obtained for this alloy system.

  13. Gapped paramagnetic state in a frustrated spin-1/2 Heisenberg antiferromagnet on the cross-striped square lattice

    Science.gov (United States)

    Li, P. H. Y.; Bishop, R. F.

    2018-03-01

    We implement the coupled cluster method to very high orders of approximation to study the spin-1/2 J1 -J2 Heisenberg model on a cross-striped square lattice. Every nearest-neighbour pair of sites on the square lattice has an isotropic antiferromagnetic exchange bond of strength J1 > 0 , while the basic square plaquettes in alternate columns have either both or neither next-nearest-neighbour (diagonal) pairs of sites connected by an equivalent frustrating bond of strength J2 ≡ αJ1 > 0 . By studying the magnetic order parameter (i.e., the average local on-site magnetization) in the range 0 ≤ α ≤ 1 of the frustration parameter we find that the quasiclassical antiferromagnetic Néel and (so-called) double Néel states form the stable ground-state phases in the respective regions α α1bc = 0.615(5) . The double Néel state has Néel (⋯ ↑↓↑↓ ⋯) ordering along the (column) direction parallel to the stripes of squares with both or no J2 bonds, and spins alternating in a pairwise (⋯ ↑↑↓↓↑↑↓↓ ⋯) fashion along the perpendicular (row) direction, so that the parallel pairs occur on squares with both J2 bonds present. Further explicit calculations of both the triplet spin gap and the zero-field uniform transverse magnetic susceptibility provide compelling evidence that the ground-state phase over all or most of the intermediate regime α1ac state with no discernible long-range magnetic order.

  14. Comparison of torque capability of three-phase permanent magnet synchronous motors with different permanent magnet arrangement

    International Nuclear Information System (INIS)

    Stumberger, Bojan; Stumberger, Gorazd; Hadziselimovic, Miralem; Hamler, Anton; Gorican, Viktor; Jesenik, Marko; Trlep, Mladen

    2007-01-01

    The paper presents a comparison of torque capability of three-phase permanent magnet synchronous motors with different permanent magnet arrangement. Motors with the following permanent magnet topologies were accounted for in the comparison: the surface-mounted permanent magnet synchronous motor (SMPMSM), the interior permanent magnet synchronous motor (IPMSM), the permanent magnet-assisted synchronous reluctance motor (PMASRM) and the flux reversal permanent magnet motor (FRPMM). Finite element method analysis is employed to determine the performance of each motor. Calculated performance of four-pole IPMSM determined by finite element method calculation is confirmed with the measurements at nearly constant nominal output power in the range of speed 3000-10,000 rpm

  15. Field-Dependent Magnetic Phase Transitions in Mixed-Valent TmSe

    DEFF Research Database (Denmark)

    Bjerrum Møller, Hans; Shapiro, S. M.; Birgenau, R. J.

    1977-01-01

    A neutron diffraction study of the field-dependent magnetic ordering in TmSe is reported. The magnetic strucutre in zero field is antiferromagnetic fcc type I with TN=3.2 K. The magnetic phase diagram may be understood as a successive domain reorientation and metamagnetic transitions for T...

  16. Torque Analysis With Saturation Effects for Non-Salient Single-Phase Permanent-Magnet Machines

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Ritchie, Ewen

    2011-01-01

    The effects of saturation on torque production for non-salient, single-phase, permanent-magnet machines are studied in this paper. An analytical torque equation is proposed to predict the instantaneous torque with saturation effects. Compared to the existing methods, it is computationally faster......-element results, and experimental results obtained on a prototype single-phase permanent-magnet machine....

  17. Numerical Simulation of Magnetic Nanoparticles Injection into Two–phase Flow in a Porous Medium

    KAUST Repository

    El-Amin, Mohamed

    2017-06-09

    In this paper, the problem of magnetic nanoparticles injection into a water–oil two–phase flow under an external permanent magnetic field is investigated. The mathematical model of the problem under consideration has been developed. We treat the water-nanoparticles suspension as a miscible mixture while it is immiscible with the oil phase. The magnetized phase pressure includes an additional pressure term with the conventional thermodynamic pressure. The countercurrent imbibition flow problem is taken as an example. Physical variables including water–nanoparticles suspension saturation, nanoparticles concentration, and pore wall/throat deposited nanoparticles are investigated under the influence of the magnetic field.

  18. Magnetic phase diagram of UNi.sub.2./sub.Si.sub.2./sub. under pressure

    Czech Academy of Sciences Publication Activity Database

    Syshchenko, O.; Khmelevski, S.; Diviš, M.; Sechovský, V.; Honda, F.; Oomi, G.; Andreev, Alexander V.; Kamarád, Jiří; Šebek, Josef; Menovsky, A. A.

    2001-01-01

    Roč. 304, - (2001), s. 477-482 ISSN 0921-4526 R&D Projects: GA ČR GA106/99/0183 Institutional research plan: CEZ:AV0Z1010914 Keywords : U intermetallics * antiferromagnetism * magnetic phase diagram * electrical resistivity * pressure effects on magnetic phases * axial Ising model Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.663, year: 2001

  19. Phase space of positron trajectories exiting a charged particle source through a magnetic field point cusp

    International Nuclear Information System (INIS)

    Kiester, A.S.; Pacheco, J.L.; Ordonez, C.A.; Weathers, D.L.

    2014-01-01

    A configuration of magnetic fields using properties of cylindrically symmetric permanent magnets is presented as a candidate to produce a high purity charged particle source or trap. Cylindrically symmetric hollow permanent magnets produce magnetic field point cusps on the axis of symmetry. A magnetic field point cusp reflects all particles that lie outside a narrow region of phase space, a region dependent on particle kinetic energies and on the magnetic field intensity. An analysis of the phase space of positron trajectories entering and exiting a magnetic field point cusp is presented and quantified with respect to magnetic field intensity and particle kinetic energy. Preliminary experimental results support the use of point cusps for ion source applications

  20. Analysis of three-phase power transformer laminated magnetic core designs

    Directory of Open Access Journals (Sweden)

    M.I. Levin

    2014-03-01

    Full Text Available Analysis and research into properties and parameters of different-type laminated magnetic cores of three-phase power transformers are conducted. Most of new laminated magnetic core designs are found to have significant shortcomings resulted from design and technological features of their manufacturing. These shortcomings cause increase in ohmic loss in the magnetic core, which eliminates advantages of the new core configurations and makes them uncompetitive as compared with the classical laminated magnetic core design.

  1. Magnetic nanoparticle based solid-phase extraction of heavy metal ions: A review on recent advances.

    Science.gov (United States)

    Hemmati, Maryam; Rajabi, Maryam; Asghari, Alireza

    2018-02-06

    This review (with 151 refs) focuses on recent progress that has been made in magnetic nanoparticle-based solid phase extraction (SPE), pre-concentration and speciation of heavy metal ions. In addition, it discusses applications to complex real samples such as environmental, food, and biological matrices. The introduction addresses current obstacles and limitations associated with established SPE approaches and discusses the present state of the art in different formats of off-line and on-line SPE. The next section covers magnetized inorganic nanomaterials for use in SPE, with subsections on magnetic silica, magnetic alumina and titania, and on magnetic layered double oxides. A further section treats magnetized carbonaceous nanomaterials for use in SPE, with subsections on magnetic graphene and/or graphene oxides, magnetic carbon nanotubes and magnetic carbon nitrides. We then discuss the progress made in SPE based on the use of magnetized organic polymers (mainly non-imprinted and ion-imprinted polymer). This is followed by shorter sections on the use of magnetized metal organic frameworks, magnetized ionic liquids and magnetized biosorbents. All sections include discussions of the nanomaterials in terms of selectivity, sorption capacity, mechanisms of sorption and common routes for material synthesis. A concluding section addresses actual challenges and discusses perspective routes towards further improvements. Graphical abstract An overview on booster nanomaterials (ionic liquids, inorganic, organic and biological materials, and metal-organic frameworks) for use in magnetic nanoparticle-based solid-phase extraction of heavy metal ions.

  2. Unconventional field induced phases in a quantum magnet formed by free radical tetramers

    Science.gov (United States)

    Saúl, Andrés; Gauthier, Nicolas; Askari, Reza Moosavi; Côté, Michel; Maris, Thierry; Reber, Christian; Lannes, Anthony; Luneau, Dominique; Nicklas, Michael; Law, Joseph M.; Green, Elizabeth Lauren; Wosnitza, Jochen; Bianchi, Andrea Daniele; Feiguin, Adrian

    2018-02-01

    We report experimental and theoretical studies on the magnetic and thermodynamic properties of NIT-2Py, a free radical based organic magnet. From magnetization and specific-heat measurements we establish the temperature versus magnetic field phase diagram which includes two Bose-Einstein condensates (BEC) and an infrequent half-magnetization plateau. Calculations based on density functional theory demonstrate that magnetically this system can be mapped to a quasi-two-dimensional structure of weakly coupled tetramers. Density matrix renormalization group calculations show the unusual characteristics of the BECs where the spins forming the low-field condensate are different than those participating in the high-field one.

  3. Crystal structures, phase relationships, and magnetic phase transitions of R5M4 compounds (R = rare earths, M = Si, Ge)

    Science.gov (United States)

    Ouyang, Zhong-Wen; Rao, Guang-Hui

    2013-09-01

    Our recent studies of the crystal structures, phase transitions, and magnetic properties of intermetallic compounds R5M4 (R = rare earths; M = Si, Ge) are reviewed briefly. First, crystal structures, phase relationships, and magnetic properties of several 5:4 compounds, including Nd5Si4-xGex, Pr5Si4-xGex, Gd5-xLaxGe4, La5Si4, and Gd5Sn4, are presented. In particular, the canted spin structures as well as the magnetic phase transitions in Pr5Si2Ge2 and Pr5Ge4 investigated by neutron powder diffractions and small-angle neutron scattering are reviewed. Second, the crystal structures and magnetic properties of the most studied compounds Gd5(Si,Ge)4 are summarized. The focus is on the parent compound Gd5Ge4, which is an amazing material exhibiting magnetic anisotropy, angular dependent spin-flop transition, metastable magnetic response, Griffiths-like phase, thermal effect under pulsed fields, antiferromagnetic and ferromagnetic resonances, pronounced effects of impurities, and high-field induced magnetic transitions.

  4. Magnet design technical report---ITER definition phase

    International Nuclear Information System (INIS)

    Henning, C.

    1989-01-01

    This report contains papers on the following topics: conceptual design; radiation damage of ITER magnet systems; insulation system of the magnets; critical current density and strain sensitivity; toroidal field coil structural analysis; stress analysis for the ITER central solenoid; and volt-second capabilities and PF magnet configurations

  5. PHASE GRADIENT METHOD OF MAGNETIC FIELD MEASUREMENTS IN ELECTRIC VEHICLES

    Directory of Open Access Journals (Sweden)

    N. G. Ptitsyna

    2013-01-01

    Full Text Available Operation of electric and hybrid vehicles demands real time magnetic field control, for instance, for fire and electromagnetic safety. The article deals with a method of magnetic field measurements onboard electric cars taking into account peculiar features of these fields. The method is based on differential methods of measurements, and minimizes the quantity of magnetic sensors.

  6. Magnetic phase diagram of the UAs - USe system

    International Nuclear Information System (INIS)

    Obolenski, M.; Troc, R.

    1977-01-01

    The UAssub(1-x)Sesub(x) system was investigated in detail by means of magnetic susceptibility and magnetization measurements. For UAs the sharp transition on the chi vs. T curve at 41 K has been additionally found. For the compositions with x 0.55 all samples are ferro magnetic. (author)

  7. Magnetically driven suppression of nematic order in an iron-based superconductor.

    Science.gov (United States)

    Avci, S; Chmaissem, O; Allred, J M; Rosenkranz, S; Eremin, I; Chubukov, A V; Bugaris, D E; Chung, D Y; Kanatzidis, M G; Castellan, J-P; Schlueter, J A; Claus, H; Khalyavin, D D; Manuel, P; Daoud-Aladine, A; Osborn, R

    2014-05-22

    A theory of superconductivity in the iron-based materials requires an understanding of the phase diagram of the normal state. In these compounds, superconductivity emerges when stripe spin density wave (SDW) order is suppressed by doping, pressure or atomic disorder. This magnetic order is often pre-empted by nematic order, whose origin is yet to be resolved. One scenario is that nematic order is driven by orbital ordering of the iron 3d electrons that triggers stripe SDW order. Another is that magnetic interactions produce a spin-nematic phase, which then induces orbital order. Here we report the observation by neutron powder diffraction of an additional fourfold-symmetric phase in Ba1-xNaxFe2As2 close to the suppression of SDW order, which is consistent with the predictions of magnetically driven models of nematic order.

  8. Effect of hydrostatic pressure on magnetic phase transitions and magnetization in gadolinium monocrystal

    International Nuclear Information System (INIS)

    Nikitin, S.A.; Bezdushnyj, R.V.

    1989-01-01

    Effect of hydrostatic pressure on magnetization in gadolinium monocrystal (Δσ-effect) was investigated. Dependences of spesific magnetization, Δσ-effect and bulk magnetostriction of gadolinium monocrystal on temperatures were studied. Results of conducted investigation have shown that in gadolinium the change of specific magnetization under the hydrostatic pressure effect is caused in general case by three effects: a)change of spontaneous magnetization under the effect of hydrostatic pressure; b)change of magnetization within technical magnetization range due to the effect of hydrostatic pressure on magnetic anisotropy constants; c)change of magnetization due to the effect of hydrostatic pressure on temperature of spin-reoriented transition

  9. Invasion of the striped mollusks

    Energy Technology Data Exchange (ETDEWEB)

    1991-09-01

    Introduced to this country only five years ago, the prolific zebra mussel has infested the Great Lakes and has already begun to move into fresh waters beyond the region. Dense populations in utility water systems have caused serious problems, reducing plant efficiency and blocking lines used for cooling and fire fighting. Experts say the striped mollusk has the potential to become the industry's worst biological problem, possibly affecting 70% of US power plants. While it appears that the invader is here to stay, EPRI and others continue to develop and refine techniques to control mussel growth. This article describes how the mollusk got here, reviews the problems it can cause and what is being done to mitigate the problems and control the growth and spread of the mollusk.

  10. Geometric Phase Of The Faraday Rotation Of Electromagnetic Waves In Magnetized Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Jian Liu and Hong Qin

    2011-11-07

    The geometric phase of circularly polarized electromagnetic waves in nonuniform magnetized plasmas is studied theoretically. The variation of the propagation direction of circularly polarized waves results in a geometric phase, which also contributes to the Faraday rotation, in addition to the standard dynamical phase. The origin and properties of the geometric phase is investigated. The in uence of the geometric phase to plasma diagnostics using Faraday rotation is also discussed as an application of the theory.

  11. Order-disorder phase transformations and magnetic structure of (Ni1-xCox)Mn alloys

    International Nuclear Information System (INIS)

    Dorofeev, Yu.A.; Men'shikov, A.Z.; Teplykh, A.E.

    2000-01-01

    By means of neutron diffraction one investigated into structure and magnetic states in (Ni 1-x Co x )Mn hardened and annealed alloys. The order-disorder phase transition from the ordered tetragonal phase to the disordered cubic one was shown to occur in the hardened alloys at x ≅ 0.3 and in the annealed ones at x ≅ 0.7. Θ-NiMn magnetic structure when cobalt substituted for nickel was determined to way in such a way that manganese magnetic moments was reoriented from direction in the tetragonal phase to direction in the cubic one and the local magnetic moment in manganese atoms was reduced from 3.8 μ B up to 1.4μ B . There is no magnetic moment in nickel and cobalt atoms both in tetragonal and in cubic phases [ru

  12. Anomalously elastic intermediate phase in randomly layered superfluids, superconductors, and planar magnets.

    Science.gov (United States)

    Mohan, Priyanka; Goldbart, Paul M; Narayanan, Rajesh; Toner, John; Vojta, Thomas

    2010-08-20

    We show that layered quenched randomness in planar magnets leads to an unusual intermediate phase between the conventional ferromagnetic low-temperature and paramagnetic high-temperature phases. In this intermediate phase, which is part of the Griffiths region, the spin-wave stiffness perpendicular to the random layers displays anomalous scaling behavior, with a continuously variable anomalous exponent, while the magnetization and the stiffness parallel to the layers both remain finite. Analogous results hold for superfluids and superconductors. We study the two phase transitions into the anomalous elastic phase, and we discuss the universality of these results, and implications of finite sample size as well as possible experiments.

  13. Unconventional magnetic phase separation in γ -CoV2O6

    Science.gov (United States)

    Shen, L.; Jellyman, E.; Forgan, E. M.; Blackburn, E.; Laver, M.; Canévet, E.; Schefer, J.; He, Z.; Itoh, M.

    2017-08-01

    We have explored the magnetism in the nongeometrically frustrated spin-chain system γ -CoV2O6 which possesses a complex magnetic exchange network. Our neutron diffraction patterns at low temperatures (T ≤TN=6.6 K) are best described by a model in which two magnetic phases coexist in a volume ratio 65(1) : 35(1), with each phase consisting of a single spin modulation. This model fits previous studies and our observations better than the model proposed by Lenertz et al. [J. Phys. Chem. C 118, 13981 (2014), 10.1021/jp503389c], which consisted of one phase with two spin modulations. By decreasing the temperature from TN, the minority phase of our model undergoes an incommensurate-commensurate lock-in transition at T*=5.6 K. Based on these results, we propose that phase separation is an alternative approach for degeneracy-lifting in frustrated magnets.

  14. Possible coexistence of double-Q magnetic order and chequerboard charge order in the re-entrant tetragonal phase of Ba0.76K0.24Fe2As2

    Science.gov (United States)

    Hou, Jianqiang; Cho, Chang-woo; Shen, Junying; Tam, Pok Man; Kao, I.-Hsuan; Lee, Mang Hei Gordon; Adelmann, Peter; Wolf, Thomas; Lortz, Rolf

    2017-08-01

    We investigate the re-entrant tetragonal phase in the iron-based superconductor Ba0 .76K0.24Fe2As2 by DC magnetization and thermoelectrical measurements. The reversible magnetization confirms by a thermodynamic method that the spin alignment in the re-entrant C4 phase is out-of-plane, in agreement with an itinerant double-Q magnetic order [Allred et al., Nat. Phys. 12, 493 (2016)]. The Nernst coefficient shows the typical unusually large negative value in the stripe-type spin density wave (SDW) state owing to the Fermi surface reconstruction associated with SDW and nematic order. At the transition into the re-entrant C4 tetragonal phase it hardly changes, which could indicate that instead of a complete vanishing of the associated charge order, the spin reorientation could trigger a redistribution of the charges to form a secondary charge order, e.g. in form of a chequerboard-like pattern that no longer breaks the rotational C4 symmetry.

  15. Magnetic properties of crystalline and amorphous phase-change materials doped with 3d impurities.

    Science.gov (United States)

    Zhang, Wei; Ronneberger, Ider; Li, Yan; Mazzarello, Riccardo

    2012-08-22

    First-principles study of the structural and magnetic properties of cubic and amorphous phase-change materials doped with 3d impurities. We find that Co- and Ni-doped Ge(2) Sb(2) Te(5) is non-magnetic, whereas Cr- and Mn-doped Ge(2) Sb(2) Te(5) is magnetic and exhibits a significant magnetic contrast between the two phases in the ferromagnetic configuration. These results are explained in terms of differences in local structure and hybridization of the impurity d-orbitals with the host states. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Out-of-phase magnetic susceptibility of rocks and soils: a rapid tool for magnetic granulometry

    Czech Academy of Sciences Publication Activity Database

    Hrouda, F.; Pokorný, J.; Ježek, J.; Chadima, Martin

    2013-01-01

    Roč. 194, č. 1 (2013), s. 170-181 ISSN 0956-540X R&D Projects: GA ČR GAP210/10/2351 Institutional support: RVO:67985831 Keywords : environmental magnetism * magnetic mineralogy and petrology * rock and mineral magnetism Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 2.724, year: 2013

  17. Magnetism in grain-boundary phase of a NdFeB sintered magnet studied by spin-polarized scanning electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kohashi, Teruo, E-mail: teruo.kohashi.fc@hitachi.com; Motai, Kumi [Central Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama 350-0395 (Japan); Nishiuchi, Takeshi; Hirosawa, Satoshi [Magnetic Materials Research Laboratory, Hitachi Metals Ltd., Osaka 618-0013 (Japan)

    2014-06-09

    The magnetism in the grain-boundary phase of a NdFeB sintered magnet was measured by spin-polarized scanning electron microscopy (spin SEM). A sample magnet was fractured in the ultra-high-vacuum chamber to avoid oxidation, and its magnetizations in the exposed grain-boundary phase on the fracture surface were evaluated through the spin polarization of secondary electrons. Spin-SEM images were taken as the fracture surface was milled gradually by argon ions, and the magnetization in the grain-boundary phase was quantitatively obtained separately from that of the Nd{sub 2}Fe{sub 14}B phase. The obtained magnetization shows that the grain-boundary phase of this magnet has substantial magnetization, which was confirmed to be ferromagnetic.

  18. Pressure drop and heat transfer of lithium single-phase flow under transverse magnetic field

    International Nuclear Information System (INIS)

    Takahashi, Minoru; Aritomi, Masanori; Inoue, Akira; Matsuzaki, Mitsuo

    1996-01-01

    Pressure drop and heat transfer characteristics of a lithium single-phase flow in a rectangular channel was investigated experimentally in the presence of a magnetic field. Friction loss coefficient under non-magnetic field and skin friction coefficient under magnetic field agreed well with the Blasius formula and a simple analytical expression, respectively. Nusselt number under non-magnetic field was slightly lower than the correlation by Hartnett and Irvine. Heat transfer was enhanced by increasing magnetic field above the Hartmann number of about 200. (author)

  19. Magnetic phase diagram of Ho/Er alloys

    DEFF Research Database (Denmark)

    Cowley, R.A.; Simpson, J.A.; Bryn-Jacobsen, C.

    1998-01-01

    The magnetic structures of a series of Ho/Er alloys have been determined by neutron-diffraction techniques. The alloys were prepared as thin films (10000 Angstrom thick) by molecular beam epitaxy, and are single crystals with a mosaic spread of about 0.2 degrees. A variety of magnetic structures...

  20. Magnetic phase transitions in TbNi(Al,In) compounds

    Czech Academy of Sciences Publication Activity Database

    Klicpera, M.; Javorský, P.; Šantavá, Eva

    2010-01-01

    Roč. 118, č. 5 (2010), s. 881-883 ISSN 0587-4246 Institutional research plan: CEZ:AV0Z10100520 Keywords : AC susceptibility * magnetic ordering Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.467, year: 2010 http://przyrbwn.icm.edu.pl/APP/PDF/118/a118z5p068.pdf

  1. Magnetic phases in Pt/Co/Pt films induced by single and multiple femtosecond laser pulses

    International Nuclear Information System (INIS)

    Kisielewski, J.; Kurant, Z.; Sveklo, I.; Tekielak, M.; Maziewski, A.; Wawro, A.

    2016-01-01

    Ultrathin Pt/Co/Pt trilayers with initial in-plane magnetization were irradiated with femtosecond laser pulses. In this way, an irreversible structural modification was introduced, which resulted in the creation of numerous pulse fluence-dependent magnetic phases. This was particularly true with the out-of-plane magnetization state, which exhibited a submicrometer domain structure. This effect was studied in a broad range of pulse fluences up to the point of ablation of the metallic films. In addition to this single-pulse experiment, multiple exposure spots were also investigated, which exhibited an extended area of out-of-plane magnetization phases and a decreased damage threshold. Using a double exposure with partially overlapped spots, a two-dimensional diagram of the magnetic phases as a function of the two energy densities was built, which showed a strong inequality between the first and second incoming pulses.

  2. Origin of modulated phases and magnetic hysteresis in TmB4

    Science.gov (United States)

    Wierschem, Keola; Sunku, Sai Swaroop; Kong, Tai; Ito, Toshimitsu; Canfield, Paul C.; Panagopoulos, Christos; Sengupta, Pinaki

    2015-12-01

    We investigate the low-temperature magnetic phases in TmB4 , a metallic quantum magnet on the geometrically frustrated Shastry-Sutherland lattice, using coordinated experimental and theoretical studies. Our results provide an explanation for the appearance of the intriguing fractional plateau in TmB4 and accompanying magnetic hysteresis. Together with observation of the bump in the half plateau, our results support the picture that the magnetization plateau structure in TmB4 is strongly influenced by the zero-field modulated phases. We present a phenomenological model to explain the appearance of the modulated phases and a microscopic Hamiltonian that captures the complete magnetic behavior of TmB4 .

  3. A single-phase axially-magnetized permanent-magnet oscillating machine for miniature aerospace power sources

    Science.gov (United States)

    Sui, Yi; Zheng, Ping; Cheng, Luming; Wang, Weinan; Liu, Jiaqi

    2017-05-01

    A single-phase axially-magnetized permanent-magnet (PM) oscillating machine which can be integrated with a free-piston Stirling engine to generate electric power, is investigated for miniature aerospace power sources. Machine structure, operating principle and detent force characteristic are elaborately studied. With the sinusoidal speed characteristic of the mover considered, the proposed machine is designed by 2D finite-element analysis (FEA), and some main structural parameters such as air gap diameter, dimensions of PMs, pole pitches of both stator and mover, and the pole-pitch combinations, etc., are optimized to improve both the power density and force capability. Compared with the three-phase PM linear machines, the proposed single-phase machine features less PM use, simple control and low controller cost. The power density of the proposed machine is higher than that of the three-phase radially-magnetized PM linear machine, but lower than the three-phase axially-magnetized PM linear machine.

  4. Stock characteristics of Hudson River striped bass

    International Nuclear Information System (INIS)

    Hoff, T.B.; McLaren, J.B.; Cooper, J.C.

    1988-01-01

    Striped bass, because of their tremendous popularity both commercially and recreationally, were a principal focus of the Hudson River power plant case. Between 1976 and 1979, over 23,000 age-II and older striped bass were studied as one facet of an extensive research program on the spring population in the Hudson River. Samples were collected from the overwintering as well as the spawning portion of the striped bass population, and included immature as well as mature fish. At least 12 age-groups contributed to spawning each year. Of these 12, age-groups III, IV, and V usually were most abundant, but the percentage of the population represented by any single age-group varied as the result of fluctuations in year-class strength. Males first became sexually mature at age II and females at age IV. Fast-growing individuals within a year class tended to mature earlier. Fecundity increased with the size of fish, reaching an observed maximum of about 3 million eggs per female. Although significant annual variations in maturity and growth were detected for Hudson River striped bass, there was no evidence of a consistent change in either variable that might be associated with increasing power plant operations and a reduction in striped bass abundance. Age at maturity and age structure are the two life history components that differ the most between the Hudson River population and other striped bass populations. 36 refs., 7 tabs

  5. Checkerboard local density of states in striped domains pinned by vortices

    DEFF Research Database (Denmark)

    Andersen, B.M.; Hedegård, P.; Bruus, Henrik

    2003-01-01

    We discuss recent elastic neutron scattering and scanning tunneling experiments on high-T-c cuprates exposed to an applied magnetic field. Antiferromagnetic vortex cores operating as pinning centers for surrounding stripes is qualitatively consistent with the neutron data provided the stripes have...... the antiphase modulation. Within a Green's function formalism we study the low energy electronic structure around the vortices and find that besides the dispersive quantum interference there exists a non-dispersive checkerboard interference pattern consistent with recent scanning tunneling measurements. Thus...

  6. Magnetic-field induced phase transitions in intermetallic rare-earth ferrimagnets with a compensation point

    Czech Academy of Sciences Publication Activity Database

    Sabdenov, Ch.K.; Davydova, M.D.; Zvezdin, K.A.; Gorbunov, Denis; Tereshina, I. S.; Andreev, Alexander V.; Zvezdin, A. K.

    2017-01-01

    Roč. 43, č. 5 (2017), s. 551-558 ISSN 1063-777X R&D Projects: GA ČR GA16-03593S Institutional support: RVO:68378271 Keywords : rare -earth intermetallics * phase diagram * field-induced transition * magnetic anisotropy * high magnetic fields Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.804, year: 2016

  7. Three magnetic particles solid phase radioimmunoassay for T4: Comparison of their results with established methods

    International Nuclear Information System (INIS)

    Bashir, T.

    1996-01-01

    The introduction of solid phase separation techniques is an important improvement in radioimmunoassays and immunoradiometric assays. Magnetic particle solid phase method has additional advantages over others, as the separation is rapid and centrifugation is not required. Three types of magnetic particles have been studied in T 4 RIA and the results have been compared with commercial kits and other established methods. (author). 4 refs, 9 figs, 2 tabs

  8. In-Situ Analysis of Phase Transformations in a Supermartensitic Stainless Steel : A magnetic approach

    NARCIS (Netherlands)

    Bojack, A.

    2018-01-01

    This thesis studies in-situ the phase transformations during heat treatment of two advanced steels: a supermartensitic stainless steels (SMSS), on which the main focus of this work is, and Fe-C-Mn-Si steels. A magnetic technique, based on the analysis of saturation magnetization, is utilized as the

  9. Magnetic imaging with a Zernike-type phase plate in a transmission electron microscope

    DEFF Research Database (Denmark)

    Pollard, Shawn; Malac, Marek; Beleggia, Marco

    2013-01-01

    We demonstrate the use of a hole-free phase plate (HFPP) for magnetic imaging in transmission electron microscopy by mapping the domain structure in PrDyFeB samples. The HFPP, a Zernike-like imaging method, allows for detecting magnetic signals in-focus to correlate the sample crystal structure a...

  10. Magnetic order, hysteresis, and phase coexistence in magnetoelectric LiCoPO4

    DEFF Research Database (Denmark)

    Fogh, Ellen; Toft-Petersen, Rasmus; Ressouche, Eric

    2017-01-01

    The magnetic phase diagram of magnetoelectric LiCoPO4 is established using neutron diffraction and magnetometry in fields up to 25.9 T applied along the crystallographic b axis. For fields greater than 11.9 T, the magnetic unit cell triples in size with propagation vector Q = (0, 1...

  11. Limits of out-of-phase susceptibility in magnetic granulometry of rocks and soils

    Czech Academy of Sciences Publication Activity Database

    Hrouda, F.; Pokorný, J.; Chadima, Martin

    2015-01-01

    Roč. 59, č. 2 (2015), s. 294-308 ISSN 0039-3169 Institutional support: RVO:67985831 Keywords : out-of-phase susceptibility * frequency-dependent susceptibility measurement accuracy * environmetal magnetism * loess * soil * paleoclimatic reconstruction Subject RIV: DE - Earth Magnetism , Geodesy, Geography Impact factor: 0.818, year: 2015

  12. ADR Magnets Operating at 30-40K, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This program is designed to achieve high operational efficiency for superconducting ADR magnets in space, and to meet space launch requirements. The overall...

  13. Novel Lightweight Magnets for Space Applications, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The Tai-Yang Research Company (TYRC) of Tallahassee, Florida, will design, build and test a superconducting magnet system optimized for low current space based...

  14. Magnetic Logic Circuits for Extreme Environments, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The program aims to demonstrate a new genre of all-magnetic logic circuits which are radiation-tolerant and capable of reliable operation in extreme environmental...

  15. Shielded ADR Magnets For Space Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — An important consideration of the use of superconducting magnets in ADR applications is shielding of the other instruments in the vicinity of the superconducting...

  16. Magnetic and magnetocaloric properties of DyMn{sub 2}Si{sub 2} compound with multiple magnetic phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Reis, D.C. dos; França, E.L.T. [Centro de Ciências Sociais Saúde e Tecnologia (CCSST), Universidade Federal do Maranhão – UFMA R. Urbano Santos, s/n, 65900-410 Imperatriz, Maranhão (Brazil); Paula, V.G. de [Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas – UNICAMP, R. Sérgio Buarque de Holanda, 777, 13083-859 Campinas, São Paulo (Brazil); Santos, A.O. dos [Centro de Ciências Sociais Saúde e Tecnologia (CCSST), Universidade Federal do Maranhão – UFMA R. Urbano Santos, s/n, 65900-410 Imperatriz, Maranhão (Brazil); Coelho, A.A.; Cardoso, L.P. [Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas – UNICAMP, R. Sérgio Buarque de Holanda, 777, 13083-859 Campinas, São Paulo (Brazil); Silva, L.M. da, E-mail: luzeli.moreira@ufma.br [Centro de Ciências Sociais Saúde e Tecnologia (CCSST), Universidade Federal do Maranhão – UFMA R. Urbano Santos, s/n, 65900-410 Imperatriz, Maranhão (Brazil)

    2017-02-15

    Structural, magnetic and magnetocaloric properties of the ternary intermetallic compound DyMn{sub 2}Si{sub 2} are studied by X-ray diffraction and magnetization measurements. It is found that DyMn{sub 2}Si{sub 2} crystalizes with tetragonal ThCr{sub 2}S{sub 2}-type structure and exhibits four successive magnetic transitions at low temperature, around 20 K, 31 K, 38 K and 82 K, named respectively as T{sub 1}, T{sub 2}, T{sub 3} and T{sub 4} transitions. Large values of magnetic field (>35 kOe) favor antiferromagnetic clusters and give rise to exchange bias effect. The different responses of T{sub 2} and T{sub 3} to field change, induces two non-identical isothermal entropy change (-ΔS{sub M}) peaks. The maximum values of -ΔS{sub M} occur in temperatures around T{sub 3} and reaches 8.2 J/kgK, for a magnetic field change of 50 kOe. Also, the presence of transitions T{sub 2} and T{sub 3} close to each other induces a table-like magnetocaloric effect (MCE) in a wide temperature range. Thus, the peculiar magnetic properties observed for DyMn{sub 2}Si{sub 2} compound are interesting for low temperature magnetic refrigeration. - Highlights: • The ternary intermetallic compound DyMn{sub 2}Si{sub 2} is proposed as magnetocaloric material. • Four magnetic phase transitions were identified for DyMn{sub 2}Si{sub 2} at low temperatures. • H >35 kOe favor antiferromagnetic clusters and give rise to exchange bias effect. • Two successive magnetic phase transitions induce a large table like EMC.

  17. Charged Stripes in the Two-Orbital Hubbard Model for Pnictides

    Science.gov (United States)

    Yao, Dao-Xin; Luo, Qinlong; Prestel, Thomas; Daghofer, Maria; Moreo, Adriana; Dagotto, Elbio

    2011-03-01

    The two-orbital Hubbard model for the pnictides is studied numerically in the real-space Hartree-Fock approximation. Upon electron doping, states with a nonuniform ditribution of charge are stabilized. The patterns observed correspond to charge stripes that run perpendicular to the direction of the spin stripes of the undoped magnetic ground state. These striped states are robust when the undoped state has a gap, although with a decreasing amplitude as the gap decreases. Results for hole doping and implications for recent experiments that reported electronic nematic states and spin incommensurability in the pnictides are also discussed. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division (Q.L., A.M., E.D.), the SYSU and NSFC-11074310 (D.X.Y.), the DFG under the Emmy-Noether program (T.P., M.D.).

  18. Field driven ferromagnetic phase nucleation and propagation from the domain boundaries in antiferromagnetically coupled perpendicular anisotropy films

    Energy Technology Data Exchange (ETDEWEB)

    Hauet, Thomas; Gunther, Christian M.; Hovorka, Ondrej; Berger, Andreas; Im, Mi-Young; Fischer, Peter; Hellwig, Olav

    2008-12-09

    We investigate the reversal process in antiferromagnetically coupled [Co/Pt]{sub X-1}/{l_brace}Co/Ru/[Co/Pt]{sub X-1}{r_brace}{sub 16} multilayer films by combining magnetometry and Magnetic soft X-ray Transmission Microscopy (MXTM). After out-of-plane demagnetization, a stable one dimensional ferromagnetic (FM) stripe domain phase (tiger-tail phase) for a thick stack sample (X=7 is obtained), while metastable sharp antiferromagnetic (AF) domain walls are observed in the remanent state for a thinner stack sample (X=6). When applying an external magnetic field the sharp domain walls of the thinner stack sample transform at a certain threshold field into the FM stripe domain wall phase. We present magnetic energy calculations that reveal the underlying energetics driving the overall reversal mechanisms.

  19. Photothermally modulated magnetic resonance applied to the study of the magnetic phase transition in gadolinium thin films

    Energy Technology Data Exchange (ETDEWEB)

    Soffner, M.E.; Tedesco, J.C.G. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas (UNICAMP), 13083-859, Campinas, SP (Brazil); Pedrochi, F. [Centro de Ciencias Sociais, Saude e Tecnologia, Universidade Federal do Maranhao, Rua Urbano Santos, s/n, Centro, 65900-000, Imperatriz, MA (Brazil); Gadioli, G.Z.; Moraes, M.A.B. de [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas (UNICAMP), 13083-859, Campinas, SP (Brazil); Guimaraes, A.O.; Silva, E.C. da [Laboratorio de Ciencias Fisicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, UENF, 28013-602 Campos dos Goytacazes, RJ (Brazil); Mansanares, A.M., E-mail: manoel@ifi.unicamp.br [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas (UNICAMP), 13083-859, Campinas, SP (Brazil)

    2012-02-29

    We explore the photothermally modulated magnetic resonance technique to investigate gadolinium thin films deposited on fused quartz substrate, as a function of thickness and thermal treatment, around the magnetic phase transition temperature. It has been observed that the maximum amplitude of the photothermally modulated magnetic resonance (PM-MR) signal takes place near the phase transition temperature, similarly to the magnetocaloric effect, for which Gd has been the prototype material. The reason is that both depend on the temperature derivative of the magnetization, which maximizes at the phase transition. Besides, there is a narrowing of transition with thermal treatment, confirming that thermal treatment stabilizes the film structure. For frequency scan measurements, the heat diffusion in a two-layer system was considered, and a depth profile study was carried out in order to investigate heterogeneities along the film thickness. From the PM-MR response as a function of the modulation frequency it was possible to estimate the thermal properties of the Gd film. Magnetization, X-ray and electron spin resonance measurements were used to complement the analysis and support the conclusions. - Highlights: Black-Right-Pointing-Pointer TC values increase with thermal treatment and film thickness. Black-Right-Pointing-Pointer PM-MR signal amplitude of the main peak is maximum at temperatures close to TC. Black-Right-Pointing-Pointer Frequency scan showed uniform film profile. Black-Right-Pointing-Pointer Gd film thermal diffusivity was found to be smaller than the bulk one.

  20. First order magneto-structural phase transition and associated multi-functional properties in magnetic solids

    International Nuclear Information System (INIS)

    Roy, Sindhunil Barman

    2013-01-01

    We show that the first order magneto-structural phase transitions observed in various classes of magnetic solids are often accompanied by useful multi-functional properties, namely giant magneto-resistance, magneto-caloric effect and magneto-striction. We highlight various characteristic features associated with a disorder influenced first order phase transition namely supercooling, superheating, phase-coexistence and metastability, in several magnetic materials and discuss how a proper understanding of the transition process can help in fine tuning of the accompanied functional properties. Magneto-elastic coupling is a key element in this first order phase transition, and methods need to be explored for maximizing the contributions from both the lattice and the magnetic degree of freedom while simultaneously minimizing the thermomagnetic hysteresis loss. An analogy is also drawn with the first order phase transition observed in dielectric materials and vortex matter of type-II superconductors. (topical review)

  1. First order magneto-structural phase transition and associated multi-functional properties in magnetic solids.

    Science.gov (United States)

    Roy, Sindhunil Barman

    2013-05-08

    We show that the first order magneto-structural phase transitions observed in various classes of magnetic solids are often accompanied by useful multi-functional properties, namely giant magneto-resistance, magneto-caloric effect and magneto-striction. We highlight various characteristic features associated with a disorder influenced first order phase transition namely supercooling, superheating, phase-coexistence and metastability, in several magnetic materials and discuss how a proper understanding of the transition process can help in fine tuning of the accompanied functional properties. Magneto-elastic coupling is a key element in this first order phase transition, and methods need to be explored for maximizing the contributions from both the lattice and the magnetic degree of freedom while simultaneously minimizing the thermomagnetic hysteresis loss. An analogy is also drawn with the first order phase transition observed in dielectric materials and vortex matter of type-II superconductors.

  2. Operation of a forced two phase cooling system on a large superconducting magnet

    International Nuclear Information System (INIS)

    Green, M.A.; Burns, W.A.; Eberhard, P.H.; Gibson, G.H.; Pripstein, M.; Ross, R.R.; Smits, R.G.; Taylor, J.D.; Van Slyke, H.

    1980-05-01

    This paper describes the operation of a forced two phase cooling system on a two meter diameter superconducting solenoid. The magnet is a thin high current density superconducting solenoid which is cooled by forced two phase helium in tubes around the coil. The magnet, which is 2.18 meters in diameter and 3.4 meters long, has a cold mass of 1700 kg. The two phase cooling system contains less than 300 liters of liquid helium, most of which is contained in a control dewar. This paper describes the operating characteristics of the LBL two phase forced cooling system during cooldown and warm up. The paper presents experimental data on operations of the magnet using either a helium pump or the refrigerator compressor to circulate two phase helium through the superconducting coil cooling tubes

  3. Formation of soft magnetic high entropy amorphous alloys composites containing in situ solid solution phase

    Science.gov (United States)

    Wei, Ran; Sun, Huan; Chen, Chen; Tao, Juan; Li, Fushan

    2018-03-01

    Fe-Co-Ni-Si-B high entropy amorphous alloys composites (HEAACs), which containing high entropy solid solution phase in amorphous matrix, show good soft magnetic properties and bending ductility even in optimal annealed state, were successfully developed by melt spinning method. The crystallization phase of the HEAACs is solid solution phase with body centered cubic (BCC) structure instead of brittle intermetallic phase. In addition, the BCC phase can transformed into face centered cubic (FCC) phase with temperature rise. Accordingly, Fe-Co-Ni-Si-B high entropy alloys (HEAs) with FCC structure and a small amount of BCC phase was prepared by copper mold casting method. The HEAs exhibit high yield strength (about 1200 MPa) and good plastic strain (about 18%). Meanwhile, soft magnetic characteristics of the HEAs are largely reserved from HEAACs. This work provides a new strategy to overcome the annealing induced brittleness of amorphous alloys and design new advanced materials with excellent comprehensive properties.

  4. Pyrolytic in situ magnetization of metal-organic framework MIL-100 for magnetic solid-phase extraction.

    Science.gov (United States)

    Huo, Shu-Hui; An, Hai-Yan; Yu, Jing; Mao, Xue-Feng; Zhang, Zhe; Bai, Lei; Huang, Yan-Feng; Zhou, Peng-Xin

    2017-09-29

    In this study, we report a facile, environmental friendly fabrication of a type of magnetic metal-organic framework (MOF) MIL-100 that can be used for magnetic solid-phase extraction (MSPE). The magnetic MOF composites were fabricated using in situ calcination method. The as-synthesized materials exhibited both high porosity and magnetic characteristics. They used for the MSPE of polycyclic aromatic hydrocarbons (PAHs) from water samples. Such MOF-based magnetic solid-phase extraction in combination with gas chromatography equipped with a flame ionization detector (GC-FID), exhibited wide linearity (0.02-250μgL -1 ), low detection limits (4.6-8.9ngL -1 ), and high enrichment factors (452-907) for PAHs. The relative standard deviations (RSDs) for intra- and inter-day extractions of PAHs were ranging from 1.7% to 9.8% and 3.8% to 9.2%, respectively. The recoveries for spiked PAHs (1μgL -1 ) in water samples were in the range of 88.5% to 106.6%. The results showed that the special anion-π orbital (electron donor-acceptor) interaction and π-π stacking between magnetic MIL-100 and PAHs play an important role in the adsorption of PAHs. Copyright © 2017. Published by Elsevier B.V.

  5. Temperature-dependent striped antiferromagnetism of LaFeAsO in a Green's function approach

    International Nuclear Information System (INIS)

    Liu Guibin; Liu Banggui

    2009-01-01

    We use a Green's function method to study the temperature-dependent average moment and magnetic phase-transition temperature of the striped antiferromagnetism of LaFeAsO, and other similar compounds, as the parents of FeAs-based superconductors. We consider the nearest and the next-nearest couplings in the FeAs layer, and the nearest coupling for inter-layer spin interaction. The dependence of the transition temperature T N and the zero-temperature average spin on the interaction constants is investigated. We obtain an analytical expression for T N and determine our temperature-dependent average spin from zero temperature to T N in terms of unified self-consistent equations. For LaFeAsO, we obtain a reasonable estimation of the coupling interactions with the experimental transition temperature T N = 138 K. Our results also show that a non-zero antiferromagnetic (AFM) inter-layer coupling is essential for the existence of a non-zero T N , and the many-body AFM fluctuations reduce substantially the low-temperature magnetic moment per Fe towards the experimental value. Our Green's function approach can be used for other FeAs-based parent compounds and these results should be useful to understand the physical properties of FeAs-based superconductors.

  6. Phase transition in one Josephson junction with a side-coupled magnetic impurity

    Science.gov (United States)

    Zhi, Li-Ming; Wang, Xiao-Qi; Jiang, Cui; Yi, Guang-Yu; Gong, Wei-Jiang

    2018-04-01

    This work focuses on one Josephson junction with a side-coupled magnetic impurity. And then, the Josephson phase transition is theoretically investigated, with the help of the exact diagonalization approach. It is found that even in the absence of intradot Coulomb interaction, the magnetic impurity can efficiently induce the phenomenon of Josephson phase transition, which is tightly related to the spin correlation manners (i.e., ferromagnetic or antiferromagnetic) between the impurity and the junction. Moreover, the impurity plays different roles when it couples to the dot and superconductor, respectively. This work can be helpful in describing the influence of one magnetic impurity on the supercurrent through the Josephson junction.

  7. First-Order Transitions and the Magnetic Phase Diagram of CeSb

    DEFF Research Database (Denmark)

    Lebech, Bente; Clausen, Kurt Nørgaard; Vogt, O.

    1980-01-01

    might exist in the magnetic phase diagram of CeSb at 16K for a field of approximately 0.3 T. The present study concludes that the transitions from the paramagnetic to the magnetically ordered states are of first order for fields below 0.8 T. Within the experimental accuracy no change has been observed......The high-temperature (14-17K) low-magnetic field (0-0.8 T) region of the phase diagram of the anomalous antiferromagnet CeSb has been reinvestigated by neutron diffraction in an attempt to locate a possible tricritical point. Previous neutron diffraction studies indicated that a tricritical point...

  8. Magnetic phase transitions in RMnGe (R=Tb, Dy) compounds induced by high magnetic fields

    International Nuclear Information System (INIS)

    Ivanova, T.I.; Nikitin, S.A.; Morozkin, A.V.; Gilewski, A.

    2010-01-01

    Magnetization isotherms for polycrystalline TbMnGe and DyMnGe compounds were measured at the temperature 4.2 K in pulsed magnetic fields (up to 360 kOe). The received isotherms demonstrate the appearance of metamagnetic transitions at low temperatures. Both compounds crystallize in the orthorhombic TiNiSi-type structure. It was found that the magnetic phase transitions with a destruction of ferrimagnetic spiral structure occur in the TbMnGe and DyMnGe compounds in high magnetic fields. An attempt was undertaken to explain the nature of these transitions using the results of the powder neutron diffraction and the qualitative estimation of the exchange interaction values on the basis of the molecular field theory.

  9. The magnetic moment of Ni in the Laves phase compound GdNi2

    International Nuclear Information System (INIS)

    Yano, Kazuo; Umehara, Izuru; Miyazawa, Tomoaki; Adachi, Yoshiya; Sato, Kiyoo

    2005-01-01

    Magnetization and inverse susceptibility of the Laves phase compound GdNi 2 were investigated and analyzed in detail by employing molecular-field analysis. Both the temperature dependence of the magnetization and the Curie-Weiss (C-W) law-like linear relationship of inverse susceptibility are reproduced in terms of a two-sublattice model and it is seen that the magnetic structure of GdNi 2 is ferrimagnetic and Ni in GdNi 2 retains a magnetic moment of about 0.24μ B

  10. A novel metastable state magnetic phase of monolayer FeSe.

    Science.gov (United States)

    Meng, Lijun; Yu, Jun; Peng, Haiyan; Li, Yanru; Zhong, Jianxin

    2018-03-05

    We found a novel metastable magnetic phase by systematically calculating total energy of monolayer FeSe in various antiferromagnetic (AFM) orders using first-principles method. The new metastable magnetic phase named as QAFM is a magnetic state with short-range magnetic structure which can be regarded as a transitional state between checkerboard-like antiferromagnetic state and collinear antiferromagnetic state. Both magnetic moments with important fluctuation and charge density difference with a 24 reconstruction of orbitals breaks C4 symmetry and maybe commonly corresponds to the nematic phase in recent transmission electron microscopy (TEM) and neutron scattering experiment observations. Its electronic band displays a Dirac-like band structure along -X in the folding Brillouin zone of supercell. The QAFM phase of FeSe holds metallic feature with dxz, dyz and dz2 band crossing Fermi level even including spin-orbit coupling. Additionally, the weight of 3d orbitals varies as the applied expansion strain which maybe directly correlated with the emerging nematic phase and superconducting state of strained monolayer FeSe. The finding of novel magnetic order maybe provide important clues to elucidate the relationship of antiferromagnetism and superconductivity for unconventional Fe-based superconductor. © 2018 IOP Publishing Ltd.

  11. Multimodal imaging of human cerebellum - merging X-ray phase microtomography, magnetic resonance microscopy and histology

    Science.gov (United States)

    Schulz, Georg; Waschkies, Conny; Pfeiffer, Franz; Zanette, Irene; Weitkamp, Timm; David, Christian; Müller, Bert

    2012-11-01

    Imaging modalities including magnetic resonance imaging and X-ray computed tomography are established methods in daily clinical diagnosis of human brain. Clinical equipment does not provide sufficient spatial resolution to obtain morphological information on the cellular level, essential for applying minimally or non-invasive surgical interventions. Therefore, generic data with lateral sub-micrometer resolution have been generated from histological slices post mortem. Sub-cellular spatial resolution, lost in the third dimension as a result of sectioning, is obtained using magnetic resonance microscopy and micro computed tomography. We demonstrate that for human cerebellum grating-based X-ray phase tomography shows complementary contrast to magnetic resonance microscopy and histology. In this study, the contrast-to-noise values of magnetic resonance microscopy and phase tomography were comparable whereas the spatial resolution in phase tomography is an order of magnitude better. The registered data with their complementary information permit the distinct segmentation of tissues within the human cerebellum.

  12. Magnetic phase transition induced by electrostatic gating in two-dimensional square metal-organic frameworks

    Science.gov (United States)

    Wang, Yun-Peng; Li, Xiang-Guo; Liu, Shuang-Long; Fry, James N.; Cheng, Hai-Ping

    2018-03-01

    We investigate theoretically magnetism and magnetic phase transitions induced by electrostatic gating of two-dimensional square metal-organic framework compounds. We find that electrostatic gating can induce phase transitions between homogeneous ferromagnetic and various spin-textured antiferromagnetic states. Electronic structure and Wannier function analysis can reveal hybridizations between transition-metal d orbitals and conjugated π orbitals in the organic framework. Mn-containing compounds exhibit a strong d -π hybridization that leads to partially occupied spin-minority bands, in contrast to compounds containing transition-metal ions other than Mn, for which electronic structure around the Fermi energy is only slightly spin split due to weak d -π hybridization and the magnetic interaction is of the Ruderman-Kittel-Kasuya-Yosida type. We use a ferromagnetic Kondo lattice model to understand the phase transition in Mn-containing compounds in terms of carrier density and illuminate the complexity and the potential to control two-dimensional magnetization.

  13. Ferromagnetic phase-mass equivalence and lunar sample magnetic remanence

    Science.gov (United States)

    Wasilewski, P. J.

    1975-01-01

    Man-made alloy spheres simulating the compositions of particles found in the lunar soil and weighting approximately 10 mg are shown to be equivalent, insofar as remanence intensity and demagnetization stability are concerned, to more than about 10 billion submicrometer spherical iron particles. The large particles not only contain large stable magnetic remanence, but when the polished surfaces of these particles are etched and carefully studied, they provide useful petrogenetic information, imply the mechanism of magnetization, the time-temperature history, and outline the format for possible paleointensity analysis. The intensity and stability of the remanence in these large spheres is related to the microstructure developed during rapid cooling.

  14. Structure and magnetism of single-phase epitaxial gamma '-Fe4N

    NARCIS (Netherlands)

    Costa-Kramer, JL; Borsa, DM; Garcia-Martin, JM; Martin-Gonzalez, MS; Boerma, DO; Briones, F

    Single phase epitaxial pure gamma(')-Fe4N films are grown on MgO (001) by molecular beam epitaxy of iron in the presence of nitrogen obtained from a radio frequency atomic source. The epitaxial, single phase nature of the films is revealed by x-ray diffraction and by the local magnetic environment

  15. Field-induced magnetic phases and electric polarization in LiNiPO4

    DEFF Research Database (Denmark)

    Jensen, Thomas Bagger Stibius; Christensen, Niels Bech; Kenzelmann, M.

    2009-01-01

    Neutron diffraction is used to probe the (H,T) phase diagram of magnetoelectric (ME) LiNiPO4 for magnetic fields along the c axis. At zero field the Ni spins order in two antiferromagnetic phases. One has commensurate (C) structures and general ordering vectors k(C)=(0,0,0); the other one...

  16. Universal Properties of the C4 Magnetic Phase in Hole Doped Ternary Superconducting Pnictides

    Science.gov (United States)

    Chmaissem, Omar

    A Fe2As2 (A =Alkali Earth) superconductors exhibit phase diagrams that are remarkably similar when substitutions are made at any of the available crystallographic sites. In recent work, we demonstrated that some hole-doped compositions with low temperature orthorhombic structures exhibit universal phase reentrance back to the tetragonal symmetry with the formation of a previously unknown magnetic C4 phase facilitated by the recovery of magnetic degeneracy coupled with spin reorientation from the in-plane to the out-of-plane c-axis direction. Using neutron diffraction and Mossbauer spectroscopy, we unraveled the nature of this new phase as being a rare double-Q magnetic structure in which two orthogonal spin density waves combine to produce the tetragonal magnetic symmetry with a checkerboard -like Fe sublattice in which half the sites are magnetic (magnetic moment nearly doubled) while the other half are not. Our results give strong evidence for the electronic itineracy of the system and provide a definite proof that the structural and magnetic transitions are driven by magnetic fluctuations rather than other mechanisms. The exact location and shape of the C4 phase space have somewhat remained until recently a mystery as the phase shifted together with the superconducting dome to different doping levels in various phase diagrams but with no any clear trends. Noting the complete absence of this phase in any known electron or isovalent-substituted analog, it has become clear that detailed mapping of the phase properties requires hole-doped systems that go beyond the customary binary diagrams. In this talk, I will present and discuss the properties of a two dimensional map in a broad range of compositions that extend between binary end-members of elaborate ternary phase diagrams. This work establishes the universality of the C4 phase, its robustness and provides a quantitative relationship between the magnetic properties and the A-site ionic size and internal

  17. Magnetic Imaging with a Novel Hole-Free Phase Plate

    DEFF Research Database (Denmark)

    Pollard, Shawn; Malac, Marek; Beleggia, Marco

    2014-01-01

    One of the main interests in phase plate imaging is motivated by a decrease in irradiation dose needed to obtain desired signal to noise ratio, a result of improved contrast transfer [1]. The decrease in irradiation improves the imaging of biological materials [2]. Here we demonstrate that phase ...

  18. Magnetic and Structural Phases of Monolayer 02 on Graphite

    DEFF Research Database (Denmark)

    McTague, J. P.; Nielsen, Mourits

    1976-01-01

    Neutron diffraction studies of O2 thin films physisorbed on the basal plane of graphite show three distinct two-dimensional crystalline phases, all incommensurate with the substrate lattice. The low-temperature monolayer phase has a distorted triangular structure analogous to the closest...

  19. Magnetic field-driven 3D-Heisenberg-like phase transition in single crystalline helimagnet FeGe

    Science.gov (United States)

    Xu, Lisha; Fan, Jiyu; Sun, Weifeng; Zhu, Yan; Hu, Dazhi; Liu, Jindong; Ji, Yanda; Shi, Daning; Yang, Hao

    2017-07-01

    Significant microscopic information about fundamental magnetic interactions of magnetic materials is probed via the critical behavior of paramagnetic-ferromagnetic phase transition. In this work, we demonstrate that the critical behavior of cubic single crystalline FeGe belongs to the isotropic 3D-Heisenberg universality class by measuring the field dependence of magnetic entropy change. The above transition is one of the magnetic field-driven phase transitions but has a feature of the crossover from first- to second-order phase transition. A phenomenological model based on the evolution of magnetic skyrmions was proposed to qualitatively understand the phase transition.

  20. Bioinspired Heterogeneous Structural Color Stripes from Capillaries.

    Science.gov (United States)

    Zhao, Ze; Wang, Huan; Shang, Luoran; Yu, Yunru; Fu, Fanfan; Zhao, Yuanjin; Gu, Zhongze

    2017-12-01

    As an important characteristic of many creatures, structural colors play a crucial role in the survival of organisms. Inspired by these features, an intelligent structural color material with a heterogeneous striped pattern and stimuli-responsivity by fast self-assembly of colloidal nanoparticles in capillaries with a certain diameter range are presented here. The width, spacing, color, and even combination of the structural color stripe patterns can be precisely tailored by adjusting the self-assembly parameters. Attractively, with the integration of a near-infrared (NIR) light responsive graphene hydrogel into the structural color stripe pattern, the materials are endowed with light-controlled reversible bending behavior with self-reporting color indication. It is demonstrated that the striped structural color materials can be used as NIR-light-triggered dynamic barcode labels for the anti-counterfeiting of different products. These features of the bioinspired structural color stripe pattern materials indicate their potential values for mimicking structural color organisms, which will find important applications in constructing intelligent sensors, anti-counterfeiting devices, and so on. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Ga1-xCrxSb: magnetic phases

    Science.gov (United States)

    Matsukura, F.

    This document is part of Subvolume D 'New Data and Updates for IV-IV; III-V; II-VI and I-VII Compounds; their Mixed Crystals and Diluted Magnetic Semiconductors' of Volume 44 'Semiconductors' of Landolt-Börnstein - Group III 'Condensed Matter'.

  2. Quantum Phase Shift of a Moving Dipole under a Magnetic Field at a Distance

    Science.gov (United States)

    Lee, Kang-Ho; Kim, Young-Wan; Kang, Kicheon

    2018-03-01

    We predict a quantum phase shift of a moving electric dipole in the presence of an external magnetic field at a distance. On the basis of the Lorentz-covariant field interaction approach, we show that a phase shift appears in the internal dipole state under the condition that the dipole is moving in the field-free region, which is distinct from the topological He-McKellar-Wilkens phase generated by a direct overlap of the dipole and the field. We discuss the experimental feasibility of detecting this phase with atomic interferometry and argue that detection of this phase will resolve the question of the locality in quantum electromagnetic interaction.

  3. Magnetic phase diagrams of classical triangular and kagome antiferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Gvozdikova, M V [Department of Physics, Kharkov National University, 61077 Kharkov (Ukraine); Melchy, P-E; Zhitomirsky, M E, E-mail: mike.zhitomirsky@cea.fr [Service de Physique Statistique, Magnetisme et Supraconductivite, UMR-E9001 CEA-INAC/UJF, 17 rue des Martyrs, 38054 Grenoble (France)

    2011-04-27

    We investigate the effect of geometrical frustration on the H-T phase diagrams of the classical Heisenberg antiferromagnets on triangular and kagome lattices. The phase diagrams for the two models are obtained from large-scale Monte Carlo simulations. For the kagome antiferromagnet, thermal fluctuations are unable to lift degeneracy completely and stabilize translationally disordered multipolar phases. We find a substantial difference in the temperature scales of the order by disorder effect related to different degeneracy of the low- and the high-field classical ground states in the kagome antiferromagnet. In the low-field regime, the Kosterlitz-Thouless transition into a spin-nematic phase is produced by unbinding of half-quantum vortices.

  4. The IAC stripe82 legacy project

    Science.gov (United States)

    Román, Javier; Fliri, Juergen; Trujillo, Ignacio

    2017-03-01

    We present new deep co-adds of data taken within Stripe 82 of the Sloan Digital Sky Survey (SDSS), especially stacked to reach the faintest surface brightness limits of this data set. Our reduction puts special emphasis on preserving the characteristics of the background (sky + diffuse light) in the input images using a non-aggressive sky subtraction strategy, resulting in an exquisite quality on extremely faint structures. The IAC Stripe 82 co-adds offer a rather unique possibility to study the low surface brightness Universe like stellar haloes and disc truncations, low surface brightness, tidal galactic interactions, extremely faint dwarf galaxies, intra-cluster light or diffuse light from galactic dust. The imaging data is publicly available at http://www.iac.es/proyecto/stripe82/.

  5. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs.

    Science.gov (United States)

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K; Rüegg, Christian; Susner, Michael A; Sefat, Athena S; Zhigadlo, Nikolai D; Morenzoni, Elvezio

    2015-09-08

    The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5 magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc(3.2) as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.

  6. Ferromagnetism modulation by phase change in Mn-doped GeTe chalcogenide magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Adam, Adam Abdalla Elbashir [Huazhong University of Science and Technology, School of Optical and Electronic Information, Wuhan (China); Wuhan National Laboratory for Optoelectronics, Wuhan (China); Alneelain University, Faculty of Science and Technology, Khartoum (Sudan); Cheng, Xiaomin; Guan, Xiawei; Miao, Xiangshui [Huazhong University of Science and Technology, School of Optical and Electronic Information, Wuhan (China); Wuhan National Laboratory for Optoelectronics, Wuhan (China)

    2014-12-15

    In this work, an effective method to modulate the ferromagnetic properties of Mn-doped GeTe chalcogenide-based phase change materials is presented. The microstructure of the phase change magnetic material Ge{sub 1-x} Mn{sub x} Te thin films was studied. The X-ray diffraction results demonstrate that the as-deposited films are amorphous, and the crystalline films are formed after annealing at 350 C for 10 min. Crystallographic structure investigation shows the existence of some secondary magnetic phases. The lattice parameters of Ge{sub 1-x} Mn{sub x} Te (x = 0.04, 0.12 and 0.15) thin films are found to be slightly different with changes of Mn compositions. The structural analysis clearly indicates that all the films have a stable rhombohedral face-centered cubic polycrystalline structure. The magnetic properties of the amorphous and crystalline Ge{sub 0.96}Mn{sub 0.04}Te were investigated. The measurements of magnetization (M) as a function of the magnetic field (H) show that both amorphous and crystalline phases of Ge{sub 0.96}Mn{sub 0.04}Te thin film are ferromagnetic and there is drastic variation between amorphous and crystalline states. The temperature (T) dependence of magnetizations at zero field cooling (ZFC) and field cooling (FC) conditions of the crystalline Ge{sub 0.96}Mn{sub 0.04}Te thin film under different applied magnetic fields were performed. The measured data at 100 and 300 Oe applied magnetic fields show large bifurcations in the ZFC and FC curves while on the 5,000 Oe magnetic field there is no deviation. (orig.)

  7. The role of equilibrium volume and magnetism on the stability of iron phases at high pressures.

    Science.gov (United States)

    Alnemrat, S; Hooper, J P; Vasiliev, I; Kiefer, B

    2014-01-29

    The present study provides new insights into the pressure dependence of magnetism by tracking the hybridization between crystal orbitals for pressures up to 600 GPa in the known hcp, bcc and fcc iron. The Birch-Murnaghan equation of state parameters are; bcc: V0 = 11.759 A(3)/atom, K0 = 177.72 GPa; hcp: V0 = 10.525 A(3)/atom, K0 = 295.16 GPa; and fcc: V0 = 10.682 A(3)/atom, K0 = 274.57 GPa. These parameters compare favorably with previous studies. Consistent with previous studies we find that the close-packed hcp and fcc phases are non-magnetic at pressures above 50 GPa and 60 GPa, respectively. The principal features of magnetism in iron are predicted to be invariant, at least up to ∼6% overextension of the equilibrium volume. Our results predict that magnetism for overextended fcc iron disappears via an intermediate spin state. This feature suggests that overextended lattices can be used to stabilize particular magnetic states. The analysis of the orbital hybridization shows that the magnetic bcc structure at high pressures is stabilized by splitting the majority and minority spin bands. The bcc phase is found to be magnetic at least up to 600 GPa; however, magnetism is insufficient to stabilize the bcc phase itself, at least at low temperatures. Finally, the analysis of the orbital contributions to the total energy provides evidence that non-magnetic hcp and fcc phases are likely more stable than bcc at core earth pressures.

  8. Scaling of magnetic fluctuations near a quantum phase transition

    DEFF Research Database (Denmark)

    Schröder, A.; Aeppli, G.; Bucher, E.

    1998-01-01

    We use inelastic neutron scattering to measure the magnetic fluctuations in a single crystal of the heavy fermion alloy CeCu5.9Au0.1 close to the antiferromagnetic quantum critical point. The energy (E), wave vector (Q), and temperature (T) dependent spectra obey E/T scaling at Q near (1...... and the thermodynamics can be understood in terms of a quantum Lifshitz point....

  9. Magnetization behavior of nanocrystalline systems combining ferromagnetic and antiferromagnetic phases

    International Nuclear Information System (INIS)

    Loeffler, J.; Wagner, W.; Svygenhoven, H. van; Meier, J.; Doudin, B.; Ansermet, J.P.

    1997-01-01

    The magnetic properties of nanostructured materials on the basis of Fe and Ni have been investigated with a SQUID magnetometer, complementary to the small-angle neutron scattering study reported in the same volume. Measurements of the coercive field in a temperature range from 5 to 300 K confirm the validity of the random anisotropy model for our nanostructured systems. Furthermore, we obtain information about the presence and distribution of the antiferromagnetic oxides, joining the ferromagnetic grains. (author) 2 figs., 3 refs

  10. Magnetization behavior of nanocrystalline systems combining ferromagnetic and antiferromagnetic phases

    Energy Technology Data Exchange (ETDEWEB)

    Loeffler, J.; Wagner, W.; Svygenhoven, H. van [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Meier, J.; Doudin, B.; Ansermet, J.P. [Ecole Polytechnique Federale, Lausanne (Switzerland)

    1997-09-01

    The magnetic properties of nanostructured materials on the basis of Fe and Ni have been investigated with a SQUID magnetometer, complementary to the small-angle neutron scattering study reported in the same volume. Measurements of the coercive field in a temperature range from 5 to 300 K confirm the validity of the random anisotropy model for our nanostructured systems. Furthermore, we obtain information about the presence and distribution of the antiferromagnetic oxides, joining the ferromagnetic grains. (author) 2 figs., 3 refs.

  11. Effect of a pulsed magnetic field on terbium high pressure phase

    International Nuclear Information System (INIS)

    Tonkov, E.Yu.; Aptekar', I.L.; Degtyareva, V.F.; Ponomarev, B.K.; Tissen, V.G.

    1977-01-01

    Through the effect of an elevated (up to 90 kbar) quasi hydrostatic pressure the Tb 3 phase has been obtained having a samarium-resembling structure which remains metastable after the pressure has been removed. It is shown that the action of a pulse magnetic field reconvert the Tb 3 phase to the initial Tb 3 phase. The Tb 3 → Tb 2 transition begins at temperatures below 190 K, the quantity of the converted phase increasing as the temperature goes down. The Neel point has been observed in Tb 3 at about 190 K. The Tb 3 → Tb 2 transition can alternatively be effected by heating to about 200 deg C and under plastic strain. Magnetostriction of the antiferromagnetic Tb 3 phase can be the possible mechanism of the Tb 3 → Tb 2 transition under the effect of magnetic field

  12. 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.

  13. Tuning the phase sensitivity of a double-lambda system with a static magnetic field.

    Science.gov (United States)

    Xu, Xiwei; Shen, Shuo; Xiao, Yanhong

    2013-05-20

    We study the effect of a DC magnetic field on the phase sensitivity of a double-lambda system coupled by two laser fields, a probe and a pump. It is demonstrated that the gain and the refractive index of the probe can be controlled by either the magnetic field or the relative phase between the two laser fields. More interestingly, when the system reduces to a single-lambda system, turning on the magnetic field transforms the system from a phase-insensitive process to a phase-sensitive one. In the pulsed-probe regime, we observed switching between slow and fast light when the magnetic field or the relative phase was adjusted. Experiments using a coated 87Rb vapor cell produced results in good agreement with our numerical simulation. This work provides a novel and simple means to manipulate phase sensitive electromagnetically-induced-transparency or four-wave mixing, and could be useful for applications in quantum optics, nonlinear optics and magnetometery based on such systems.

  14. Reorientation of the diagonal double-stripe spin structure at Fe1+yTe bulk and thin-film surfaces

    Science.gov (United States)

    Hänke, Torben; Singh, Udai Raj; Cornils, Lasse; Manna, Sujit; Kamlapure, Anand; Bremholm, Martin; Hedegaard, Ellen Marie Jensen; Iversen, Bo Brummerstedt; Hofmann, Philip; Hu, Jin; Mao, Zhiqiang; Wiebe, Jens; Wiesendanger, Roland

    2017-01-01

    Establishing the relation between ubiquitous antiferromagnetism in the parent compounds of unconventional superconductors and their superconducting phase is important for understanding the complex physics in these materials. Going from bulk systems to thin films additionally affects their phase diagram. For Fe1+yTe, the parent compound of Fe1+ySe1-xTex superconductors, bulk-sensitive neutron diffraction revealed an in-plane oriented diagonal double-stripe antiferromagnetic spin structure. Here we show by spin-resolved scanning tunnelling microscopy that the spin direction at the surfaces of bulk Fe1+yTe and thin films grown on the topological insulator Bi2Te3 is canted out of the high-symmetry directions of the surface unit cell resulting in a perpendicular spin component, keeping the diagonal double-stripe order. As the magnetism of the Fe d-orbitals is intertwined with the superconducting pairing in Fe-based materials, our results imply that the superconducting properties at the surface of the related superconducting compounds might be different from the bulk.

  15. Magnetic structures, phase diagram and spin waves of magneto-electric LiNiPO4

    DEFF Research Database (Denmark)

    Jensen, Thomas Bagger Stibius

    2007-01-01

    LiNiPO4 is a magneto-electric material, having co-existing antiferromagnetic and ferroelectric phases when suitable magnetic fields are applied at low temperatures. Such systems have received growing interest in recent years, but the nature of the magneticelectric couplings is yet to be fully...... understand. Hopefully, studying LiNiPO4 will shed further light on the subject, especially since the crystal structure of LiNiPO4 is rather simple compared to most relevant multiferroic materials. Although the study of the magnetic-electric couplings is of main interest to the many scientists guiding me...... through the last three years, it is not the primary subject of this thesis. The objective of the phD project has been to provide groundwork that may be beneficiary to future studies of LiNiPO4. More specifically, we have mapped out the magnetic HT phase diagram with magnetic fields below 14.7 T applied...

  16. Magnetic Field Sensing Based on Bi-Tapered Optical Fibers Using Spectral Phase Analysis

    Directory of Open Access Journals (Sweden)

    Luis A. Herrera-Piad

    2017-10-01

    Full Text Available A compact, magnetic field sensor system based on a short, bi-tapered optical fiber (BTOF span lying on a magnetic tape was designed, fabricated, and characterized. We monitored the transmission spectrum from a broadband light source, which displayed a strong interference signal. After data collection, we applied a phase analysis of the interference optical spectrum. We here report the results on two fabricated, BTOFs with different interference spectrum characteristics; we analyzed the signal based on the interference between a high-order modal component and the core fiber mode. The sensor exhibited a linear response for magnetic field increments, and we achieved a phase sensitivity of around 0.28 rad/mT. The sensing setup presented remote sensing operation and low-cost transducer magnetic material.

  17. Microstructure, Corrosion and Magnetic Behavior of an Aged Dual-Phase Stainless Steel

    Science.gov (United States)

    Ziouche, A.; Haddad, A.; Badji, R.; Zergoug, M.; Zoubiri, N.; Bedjaoui, W.; Abaidia, S.

    2018-03-01

    In the present work, the effect of the precipitation phenomena on corrosion and magnetic behavior of an aged dual-phase stainless steel was investigated. Aging treatment caused the precipitation of the σ phase, chromium carbides and secondary austenite, which was accompanied by the shifting of the δ/γ interfaces inside the δ ferrite grains. Aging between 700 and 850 °C strongly deteriorated the pitting corrosion resistance of the studied material. Magnetic investigation of the aged material using the vibration sample magnetic technique revealed the sensitivity of the intrinsic magnetic properties to the smallest microstructural change. This was confirmed by the Eddy current technique that led also to the evaluation of the aging-induced localized corrosion.

  18. DNA methylation profiles correlated to striped bass sperm fertility

    Science.gov (United States)

    Striped bass (Morone saxatilis) spermatozoa are used to fertilize in vitro the eggs of white bass (Morone chrysops) to produce the preferred hybrid for the striped bass aquaculture industry. Currently, only one source of domestic striped bass juveniles are available to growers that are not obtained ...

  19. How to detect Berry phase in graphene without magnetic field?

    Science.gov (United States)

    Koochaki Kelardeh, Hamed; Apalkov, Vadym; Stockman, Mark I.

    2017-09-01

    We discuss the topological properties of graphene superlattices excited by ultrafast circularly-polarized laser pulses with strong electric field amplitude, aiming to directly observe of the Berry phase, a geometric quantum phase encoded in the graphene's electronic wave function. As a continuing research on our recent paper, Phys. Rev. B 96, 075409, we aim to show that the broken symmetry system of graphene superlattice and the Bragg reflection of electrons creates diffraction and "which way" interference in the reciprocal space reducing the geometrical phase shift and making it directly observable in the electron interferograms. Such a topological phase shift acquired by a carrier moving along a closed path of crystallographic wave vector is predictably observable via time and angle resolved photoemission spectroscopy (tr-ARPES). We believe that our result is an essential step in control and observation of ultrafast electron dynamics in topological solids and may open up a route to all-optical switching, ultrafast memories, and petahertz-scale information processing technologies.

  20. Commensurate-commensurate magnetic phase transitions in CeSb

    DEFF Research Database (Denmark)

    Lebech, Bente; Broholm, C.; Clausen, K.

    1986-01-01

    The q=2/3 to q=4/7 commensurate-commensurate phase transition in CeSb has been studied by neutron diffraction. On cooling the commensurate wave vector q changes abruptly from 2/3 to a higher-order commensurate value (≈14/23) at T1

  1. Probing Magnetism in the Vortex Phase of PuCoGa_{5} by X-Ray Magnetic Circular Dichroism.

    Science.gov (United States)

    Magnani, N; Eloirdi, R; Wilhelm, F; Colineau, E; Griveau, J-C; Shick, A B; Lander, G H; Rogalev, A; Caciuffo, R

    2017-10-13

    We measure x-ray magnetic circular dichroism (XMCD) spectra at the Pu M_{4,5} absorption edges from a newly prepared high-quality single crystal of the heavy-fermion superconductor ^{242}PuCoGa_{5}, exhibiting a critical temperature T_{c}=18.7  K. The experiment probes the vortex phase below T_{c} and shows that an external magnetic field induces a Pu 5f magnetic moment at 2 K equal to the temperature-independent moment measured in the normal phase up to 300 K by a superconducting quantum interference device. This observation is in agreement with theoretical models claiming that the Pu atoms in PuCoGa_{5} have a nonmagnetic singlet ground state resulting from the hybridization of the conduction electrons with the intermediate-valence 5f electronic shell. Unexpectedly, XMCD spectra show that the orbital component of the 5f magnetic moment increases significantly between 30 and 2 K; the antiparallel spin component increases as well, leaving the total moment practically constant. We suggest that this indicates a low-temperature breakdown of the complete Kondo-like screening of the local 5f moment.

  2. Phase transition of iron sulphide minerals under hydrothermal conditions and magnetic investigations

    Science.gov (United States)

    Li, Ssu Han; Chen, Yen-Hua; Lee, Jey-Jau; Sheu, Hwo-Shuenn

    2018-01-01

    Iron sulphide minerals have been used in industrial applications for many years, and more recently there has been increasing interest in the use of iron sulphide nanomaterials because of their useful properties and low cost. Previous studies have mainly focused on the synthesis of iron sulphides, but their phase transition and micro-magnetic properties are still unclear. In this study, iron sulphide minerals were synthesized via a hydrothermal method, and their phase transition mechanisms and magnetic properties were investigated. Ex situ and in situ X-ray diffraction results of the iron-sulphur system under hydrothermal conditions suggested that the transformation sequence followed the order of mackinawite (FeS) → greigite (Fe3S4) → smythite (Fe9S11) → pyrrhotite (Fe9S10). Pure greigite and pyrrhotite were obtained during the synthesis processes, after 1 h at 120 and 160 °C, respectively. Greigite showed a granular morphology with particle diameters around 30 nm, and pyrrhotite comprised stacked hexagonal sheets with thousands of nanometers in width. Pyrrhotite showed anti-ferromagnetic behaviour; however, it did not saturate up to magnetic field of 7 T. Greigite was ferrimagnetic, with a high saturation magnetization of 62.7 Am2 kg-1 and coercive magnetic field of 27.6 mT. Magnetic force microscope measurements of greigite revealed that its magnetic structure belonged to a spin-canted single domain. Overall, this study provides new information on the phase transition mechanism, related reaction formulas, and magnetic properties of iron sulphides, and it emphasizes the important role played by temperature/time in phase transitions.

  3. Moessbauer study of the magnetic phase transformations in SnMn3N

    International Nuclear Information System (INIS)

    Nagy, D.L.; Zimmer, G.J.; Lohner, T.; Senateur, J.P.

    1975-01-01

    Moessbauer measurements were performed on SnMn 3 N with the aim of verifying the magnetic phase transformations at 175 and 230 K and the Neel transition at 475 K as well as of seeking an explanation for the anomalous peak in magnetic susceptibility about 380 K. Moessbauer spectra were taken at several temperatures between 83 and 475 K and evaluated by a least square fitting program. Abrupt changes in the hyperfine field were found at 175, 230 and 350 K indicating first-order magnetic phase transformations at these temperatures; the 350 K transformation is certainly related to the anomaly in susceptibility. About 475 only a smooth change in the hyperfine field was found suggesting the Neel transition to be of the second order. An attempt is made to explain the relatively high hyperfine field in the cubic antiferromagnetic phase. (A.K.)

  4. Modelling study of magnetic and concentration phase transition in ultrathin antiferromagnetic films

    International Nuclear Information System (INIS)

    Leonid, Afremov; Aleksandr, Petrov

    2014-01-01

    Using the method of the ''average spin'' a modelling study of magnetic and concentration phase transition in ultrathin antiferromagnetic of different crystalline structure has been carried out. It has been shown, that relative change of Neel temperature is subject to the power law with negative index which doesn't depend on the film's crystal kind. The calculation of the dependence of phase transition critical concentration in diluted magnetic material on the film thickness has been made out. The legitimacy of the use of the method developed for modelling of magnetic and concentration phase transition in different nanostructures is certified by accordance between the results of calculations and the experimental data

  5. Ground state and magnetic phase transitions of orthoferrite DyFeO3

    Science.gov (United States)

    Zhao, Z. Y.; Zhao, X.; Zhou, H. D.; Zhang, F. B.; Li, Q. J.; Fan, C.; Sun, X. F.; Li, X. G.

    2014-06-01

    Low-temperature thermal conductivity (κ), as well as magnetization (M) and electric polarization (P), of multiferroic orthoferrite DyFeO3 single crystals are studied with H ∥c. When the crystal is cooled in zero field, M, P, and κ all consistently exhibit irreversible magnetic-field dependencies. In particular, with 500 mK ultra-low-T (T mK) κ (H) shows a different irreversibility and there is only one transition when the field is swept both up and down. All the results indicate a complex low-T H-T phase diagram involving successive magnetic phase transitions of the Fe3+ spins. In particular, the ground state, obtained with cooling to sub-Kelvin temperatures in zero field, is found to be an unexplored phase.

  6. High-field magnetic phase transitions and spin excitations in magnetoelectric LiNiPO4

    DEFF Research Database (Denmark)

    Toft-Petersen, Rasmus; Jensen, Jens; Jensen, Thomas Bagger Stibius

    2011-01-01

    The magnetically ordered phases and spin dynamics of magnetoelectric LiNiPO4 have been studied in fields up to 17.3 T along the c axis. Using neutron diffraction, we show that a previously proposed linearly polarized incommensurate (IC) structure exists only for temperatures just below the Neel......, the spiral structure is found to lock in to a period of five crystallographic unit cells along the b axis. Based on the neutron-diffraction data, combined with detailed magnetization measurements along all three crystallographic axes, we establish the magnetic phase diagrams for fields up to 17.3 T along c...... and for fields up to 16 T along a and b. The spin excitations in the high-field IC spiral phase have been studied in detail by inelastic neutron scattering. A mean-field analysis shows that the spin Hamiltonian derived previously from the low-temperature spin waves at zero field predicts the transition between...

  7. Dynamic magnetic hysteresis behavior and dynamic phase transition in the spin-1 Blume-Capel model

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram, E-mail: bayram.deviren@nevsehir.edu.tr [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-03-15

    The nature (time variation) of response magnetization m(wt) of the spin-1 Blume-Capel model in the presence of a periodically varying external magnetic field h(wt) is studied by employing the effective-field theory (EFT) with correlations as well as the Glauber-type stochastic dynamics. We determine the time variations of m(wt) and h(wt) for various temperatures, and investigate the dynamic magnetic hysteresis behavior. We also investigate the temperature dependence of the dynamic magnetization, hysteresis loop area and correlation near the transition point in order to characterize the nature (first- or second-order) of the dynamic transitions as well as obtain the dynamic phase transition temperatures. The hysteresis loops are obtained for different reduced temperatures and we find that the areas of the loops are decreasing with the increasing of the reduced temperatures. We also present the dynamic phase diagrams and compare the results of the EFT with the results of the dynamic mean-field approximation. The phase diagrams exhibit many dynamic critical points, such as tricritical ( Bullet ), zero-temperature critical (Z), triple (TP) and multicritical (A) points. According to values of Hamiltonian parameters, besides the paramagnetic (P), ferromagnetic (F) fundamental phases, one coexistence or mixed phase region, (F+P) and the reentrant behavior exist in the system. The results are in good agreement with some experimental and theoretical results. - Highlights: Black-Right-Pointing-Pointer Kinetic spin-1 Blume-Capel model is studied using the effective-field theory. Black-Right-Pointing-Pointer We investigated the dynamic magnetic hysteresis behavior. Black-Right-Pointing-Pointer Dynamic magnetization, hysteresis loop area and correlation are investigated. Black-Right-Pointing-Pointer System exhibits tricritical, zero-temperature, triple and multicritical points. Black-Right-Pointing-Pointer We present the dynamic phase diagrams and compare the results of the EFT

  8. Analysis of Magnetically-Coupled Impedance Source Three-Phase Four-Switch Inverters

    DEFF Research Database (Denmark)

    Li, Kerui; Abdelhakim, Ahmed; Yang, Yongheng

    2017-01-01

    In this paper, magnetically-coupled impedance source (MCIS) three-phase four-switch inverters are introduced for renewable energy applications. This inverter utilizes two single-phase MCIS inverters to obtain a three-phase output, where less component-count is achieved in order to reduce...... the inverter volume. On the other hand, as a result of the reduced number of switches, the proposed inverter suffers from higher voltage stresses. The MCIS inverters are first reviewed. Then, the modulation and operation principle of the MCIS three-phase inverter topology are introduced before sizing...

  9. Experimental and modeling studies on phase stability of nanocrystalline magnetic Sm2Co7

    International Nuclear Information System (INIS)

    Xu, Wenwu; Song, Xiaoyan; Zhang, Zhexu; Liang, Haining

    2013-01-01

    Highlights: • Low-Co Sm–Co alloy as new candidate for permanent magnets was proposed. • Relationship between the phase stability and grain size was quantified for Sm 2 Co 7 . • The work contributes to the development of nanostructured Sm–Co permanent magnetic materials. -- Abstract: In contrast to the conventional polycrystalline low-Co Sm–Co alloys that have very weak permanent magnetic properties, the Sm 2 Co 7 alloy has been found to have fairly promising permanent magnetic performance when its grain size is reduced to the nanoscale. It was discovered that the crystal structure of the nanocrystalline Sm 2 Co 7 has a strong nanograin-size-dependent stability. The rhombohedral structure of Sm 2 Co 7 phase which is metastable at temperatures lower than 1435 K in conventional polycrystalline system can exist stably at room temperature in the nanocrystalline system. To understand the phase stability of the nanocrystalline Sm 2 Co 7 , the experimental and nanothermodynamic analyses were combined to describe quantitatively the phase transformation behavior of Sm 2 Co 7 on the nanoscale. The results are important for the development of nanostructured Sm–Co permanent magnets

  10. Quantum Femtosecond Magnetism: Phase Transition in Step with Light in a Strongly Correlated Manganese Oxide

    Science.gov (United States)

    Wang, Jigang

    2014-03-01

    Research of non-equilibrium phase transitions of strongly correlated electrons is built around addressing an outstanding challenge: how to achieve ultrafast manipulation of competing magnetic/electronic phases and reveal thermodynamically hidden orders at highly non-thermal, femtosecond timescales? Recently we reveal a new paradigm called quantum femtosecond magnetism-photoinduced femtosecond magnetic phase transitions driven by quantum spin flip fluctuations correlated with laser-excited inter-atomic coherent bonding. We demonstrate an antiferromagnetic (AFM) to ferromagnetic (FM) switching during about 100 fs laser pulses in a colossal magneto-resistive manganese oxide. Our results show a huge photoinduced femtosecond spin generation, measured by magnetic circular dichroism, with photo-excitation threshold behavior absent in the picosecond dynamics. This reveals an initial quantum coherent regime of magnetism, while the optical polarization/coherence still interacts with the spins to initiate local FM correlations that compete with the surrounding AFM matrix. Our results thus provide a framework that explores quantum non-equilibrium kinetics to drive phase transitions between exotic ground states in strongly correlated elecrons, and raise fundamental questions regarding some accepted rules, such as free energy and adiabatic potential surface. This work is in collaboration with Tianqi Li, Aaron Patz, Leonidas Mouchliadis, Jiaqiang Yan, Thomas A. Lograsso, Ilias E. Perakis. This work was supported by the National Science Foundation (contract no. DMR-1055352). Material synthesis at the Ames Laboratory was supported by the US Department of Energy-Basic Energy Sciences (contract no. DE-AC02-7CH11358).

  11. CFA Films in Amorphous Substrate: Structural Phase Induction and Magnetization Dynamics

    Science.gov (United States)

    Correa, M. A.; Bohn, F.; Escobar, V. M.

    We report a systematic study of the structural and quasi-static magnetic properties, as well as of the dynamic magnetic response through MI effect, in Co2FeAl and MgO//Co2FeAl single layers and a MgO//Co2FeAl/Ag/Co2FeAl trilayered film, all grown onto an amorphous substrate. We present a new route to induce the crystalline structure in the Co2FeAl alloy and verify that changes in the structural phase of this material leads to remarkable modifications of the magnetic anisotropy and, consequently, dynamic magnetic behavior. Considering the electrical and magnetic properties of the Co2FeAl, our results open new possibilities for technological applications of this full-Heusler alloy in rigid and flexible spintronic devices.

  12. Phase transitions in a magnetic field in V2-yO3 (y=0 and 0.04)

    Science.gov (United States)

    Bao, Wei; Lacerda, A. H.; Thompson, J. D.; Honig, J. M.; Metcalf, P.

    2001-02-01

    The effect of a magnetic field on the two long-range-ordered magnetic phases, the collinear insulating antiferromagnetic (AFI) and the incommensurate metallic transverse spin density wave (SDW), is investigated for the vanadium sesquioxide system. A field of 18 T has little effect on the AFI phase of a nominal V2O3 sample. The transverse SDW phase of V1.96O3 can be suppressed by a 4.6(3)-T magnetic field applied in the plane of spiraling spins, while the same magnetic field applied along the spiral axis has little effect on the SDW phase.

  13. Anelastic spectroscopy measurements of nanoscale charge and magnetic structures in cuprates and manganites

    International Nuclear Information System (INIS)

    Cordero, F.; Paolone, A.; Castellano, C.; Cantelli, R.

    2004-01-01

    Many perovskites and perovskite related materials exhibit electronic phase separation phenomena at nanometer scales, which are thought to concur to important electric and magnetic properties, like high-T c superconductivity or colossal magnetoresistence (CMR). Recent and new anelastic spectroscopy experiments are presented, which supply information on the dynamics of such inhomogeneities in the superconductors of the La 2-x Sr x CuO 4 (LSCO) family and on the magnetic perovskite La 1-x Ca x MnO 3 . In La 2-x Sr x CuO 4 , a relaxation process at liquid He temperatures is identified as due to the motion of the hole stripes, acting as walls between antiferromagnetic (AF) domains. Another process is identified as the depinning of these stripes from defects in the disordered phase. In La 1-x Ca x MnO 3 a glassy dynamic response below the ferromagnetic (FM) transition is attributed to the insulating nanodomains coexisting with the ferromagnetic background

  14. Magnetic phase diagram of ErGe 1-xSi x (0

    Science.gov (United States)

    Thuéry, P.; El Maziani, F.; Clin, M.; Schobinger-Papamantellos, P.; Buschow, K. H. J.

    1993-10-01

    The composition-temperature magnetic phase diagram of ErGe 1- xSi x (0 0.40. For 0.17 ≥ x ≤ 0.55, a first-order transition occurs as function of the temperature between these two phases. For x ≥ 0.65, a lock-in transition takes place at TIC, leading from the wavevector ( k' x,0, k' z) to (1/2,0,1/2), as was already observed in ErSi. Finally, for x < 0.17 or 0.55 < x < 0.65, the wavevectors of the incommensurate phases characterized by (0,0, kz) or ( k' x,0, k' z) respectively remain unchanged in the whole temperature range below TN. For x≥0.65, a small amount of a magnetic phase characterized by the wavevector (0,0, 1/2) coexists with the main phases, below a Néel temperature T' N slightly lower than TN. In all cases, the erbium magnetic moments are colinear along the orthorhombic α-axis; the arrangement of the moments in the commensurate phases is the same as in ErSi and the incommensurate orderings correspond to sine-wave amplitude modulations. A brief account on the theoretical interpretation of this phase diagram is finally given.

  15. Magnetic Tunnel Junction-Based On-Chip Microwave Phase and Spectrum Analyzer

    Science.gov (United States)

    Fan, Xin; Chen, Yunpeng; Xie, Yunsong; Kolodzey, James; Wilson, Jeffrey D.; Simons, Rainee N.; Xiao, John Q.

    2014-01-01

    A magnetic tunnel junction (MTJ)-based microwave detector is proposed and investigated. When the MTJ is excited by microwave magnetic fields, the relative angle between the free layer and pinned layer alternates, giving rise to an average resistance change. By measuring the average resistance change, the MTJ can be utilized as a microwave power sensor. Due to the nature of ferromagnetic resonance, the frequency of an incident microwave is directly determined. In addition, by integrating a mixer circuit, the MTJ-based microwave detector can also determine the relative phase between two microwave signals. Thus, the MTJbased microwave detector can be used as an on-chip microwave phase and spectrum analyzer.

  16. Magnetic order in the pseudogap phase of high-Tc superconductors.

    Science.gov (United States)

    Fauqué, B; Sidis, Y; Hinkov, V; Pailhès, S; Lin, C T; Chaud, X; Bourges, P

    2006-05-19

    One of the leading issues in high-T(c) superconductors is the origin of the pseudogap phase in underdoped cuprates. Using polarized elastic neutron diffraction, we identify a novel magnetic order in the YB(2)Cu(3)O(6+) system. The observed magnetic order preserves translational symmetry of the lattice as proposed for orbital moments in the circulating current theory of the pseudogap state. To date, it is the first direct evidence of a hidden order parameter characterizing the pseudogap phase in high-T(c) cuprates.

  17. Chiral phase transition of three flavor QCD with nonzero magnetic field using standard staggered fermions

    Science.gov (United States)

    Tomiya, Akio; Ding, Heng-Tong; Mukherjee, Swagato; Schmidt, Christian; Wang, Xiao-Dan

    2018-03-01

    Lattice simulations for (2+1)-flavor QCD with external magnetic field demon-strated that the quark mass is one of the important parameters responsible for the (inverse) magnetic catalysis. We discuss the dependences of chiral condensates and susceptibilities, the Polyakov loop on the magnetic field and quark mass in three degenerate flavor QCD. The lattice simulations are performed using standard staggered fermions and the plaquette action with spatial sizes Nσ = 16 and 24 and a fixed temporal size Nτ = 4. The value of the quark masses are chosen such that the system undergoes a first order chiral phase transition and crossover with zero magnetic field. We find that in light mass regime, the quark chiral condensate undergoes magnetic catalysis in the whole temperature region and the phase transition tend to become stronger as the magnetic field increases. In crossover regime, deconfinement transition temperature is shifted by the magnetic field when quark mass ma is less than 0:4. The lattice cutoff effects are also discussed.

  18. substitution line for resistance to stripe rust

    Indian Academy of Sciences (India)

    2011-08-19

    Aug 19, 2011 ... c Indian Academy of Sciences. RESEARCH ARTICLE. Molecular cytogenetic characterization of a new wheat Secale africanum. 2R a. (2D) substitution line for resistance to stripe rust. MENGPING LEI, GUANGRONG LI, SUFEN ZHANG, CHENG LIU and ZUJUN YANG. ∗. School of Life Science and ...

  19. Geometric Phase of the Gyromotion for Charged Particles in a Time-dependent Magnetic Field

    International Nuclear Information System (INIS)

    Liu, Jian; Qin, Hong

    2011-01-01

    We study the dynamics of the gyrophase of a charged particle in a magnetic field which is uniform in space but changes slowly with time. As the magnetic field evolves slowly with time, the changing of the gyrophase is composed of two parts. The rst part is the dynamical phase, which is the time integral of the instantaneous gyrofrequency. The second part, called geometric gyrophase, is more interesting, and it is an example of the geometric phase which has found many important applications in different branches of physics. If the magnetic field returns to the initial value after a loop in the parameter space, then the geometric gyrophase equals the solid angle spanned by the loop in the parameter space. This classical geometric gyrophase is compared with the geometric phase (the Berry phase) of the spin wave function of an electron placed in the same adiabatically changing magnetic field. Even though gyromotion is not the classical counterpart of the quantum spin, the similarities between the geometric phases of the two cases nevertheless reveal the similar geometric nature of the different physics laws governing these two physics phenomena.

  20. Partial phase transition and quantum effects in helimagnetic films under an applied magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    El Hog, Sahbi, E-mail: sahbi.el-hog@u-cergy.fr; Diep, H.T., E-mail: diep@u-cergy.fr

    2017-05-01

    We study the phase transition in a helimagnetic film with Heisenberg spins under an applied magnetic field in the c direction perpendicular to the film. The helical structure is due to the antiferromagnetic interaction between next-nearest neighbors in the c direction. Helimagnetic films in zero field are known to have a strong modification of the in-plane helical angle near the film surfaces. We show that spins react to a moderate applied magnetic field by creating a particular spin configuration along the c axis. With increasing temperature (T), using Monte Carlo simulations we show that the system undergoes a phase transition triggered by the destruction of the ordering of a number of layers. This partial phase transition is shown to be intimately related to the ground-state spin structure. We show why some layers undergo a phase transition while others do not. The Green's function method for non collinear magnets is also carried out to investigate effects of quantum fluctuations. Non-uniform zero-point spin contractions and a crossover of layer magnetizations at low T are shown and discussed. - Highlights: • Monte Carlo simulations were carried out to study a helimagnetic film in a field. • Partial phase transition is found in some layers of the film. • Mechanism leading to the partial disordering is analyzed using the ground state symmetry. • Quantum fluctuations at surface are calculated using the Green's function.

  1. Breakup Behavior of a Capillary Bridge on a Hydrophobic Stripe Separating Two Hydrophilic Stripes

    Science.gov (United States)

    Hartmann, Maximilian; Hardt, Steffen

    2017-11-01

    The breakup dynamics of a capillary bridge on a hydrophobic area between two liquid filaments occupying two parallel hydrophilic stripes is studied experimentally. In addition calculations with the finite-element software Surface Evolver are performed to obtain the corresponding stable minimal surfaces. Droplets of de-ionized water are placed on substrates with alternating hydrophilic and hydrophobic stripes of different width. Their volume decreases by evaporation. This results in a droplet shaped as the letter ``H'' covering two hydrophilic stripes separated by one hydrophobic stripe. The width of the capillary bridge d(t) on the hydrophobic stripe during the breakup process is observed using a high-speed camera mounted on a bright-field microscope. The results of the experiments and the numerical studies show that the critical width dcrit, indicating the point where the capillary bridge becomes unstable, mainly depends on the width ratio of the hydrophilic and hydrophobic stripes. It is found that the time derivative of d(t) first decreases after dcrit has been reached. The final breakup dynamics then follows a t 2 / 3 scaling. We kindly acknowledge the financial support by the German Research Foundation (DFG) within the Collaborative Research Centre 1194 ``Interaction of Transport and Wetting Processes'', Project A02a.

  2. Anti-phase boundaries and magnetic domain structures in Ni{sub 2}MnGa-type Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Venkateswaran, S.P. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Nuhfer, N.T. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); De Graef, M. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States)]. E-mail: degraef@cmu.edu

    2007-05-15

    The microstructure and magnetic domain structure of austenitic Heusler Ni{sub 2}MnGa are investigated as a function of heat treatment to study the interplay of anti-phase boundaries and magnetic domain walls. Conventional electron microscopy observations on arc-melted polycrystalline samples show that anti-phase boundaries in this system are invisible for standard two-beam imaging conditions, due to the large extinction distance of the Heusler superlattice reflections. Lorentz Fresnel and Foucault observations on quenched samples reveal a wavy magnetic domain morphology, reminiscent of curved anti-phase boundaries. A close inspection of the domain images indicates that the anti-phase boundaries have a magnetization state different from that of the matrix. Fresnel image simulations for a simple magnetization model are in good agreement with the observations. Magnetic coercivity measurements show a decrease in coercivity with annealing, which correlates with the microscopy observations of reduced anti-phase boundary density for annealed samples.

  3. Effects of the randomly distributed magnetic field on the phase diagrams of the Ising Nanowire II: Continuous distributions

    International Nuclear Information System (INIS)

    Akıncı, Ümit

    2012-01-01

    The effect of the random magnetic field distribution on the phase diagrams and ground state magnetizations of the Ising nanowire has been investigated with effective field theory with correlations. Gaussian distribution has been chosen as a random magnetic field distribution. The variation of the phase diagrams with that distribution parameters has been obtained and some interesting results have been found such as disappearance of the reentrant behavior and first order transitions which appear in the case of discrete distributions. Also for single and double Gaussian distributions, ground state magnetizations for different distribution parameters have been determined which can be regarded as separate partially ordered phases of the system. - Highlights: ► We give the phase diagrams of the Ising nanowire under the continuous randomly distributed magnetic field. ► Ground state magnetization values obtained. ► Different partially ordered phases observed.

  4. Tetragonal magnetic phase in Ba1 -xKxFe2As2 from x-ray and neutron diffraction

    Science.gov (United States)

    Allred, J. M.; Avci, S.; Chung, D. Y.; Claus, H.; Khalyavin, D. D.; Manuel, P.; Taddei, K. M.; Kanatzidis, M. G.; Rosenkranz, S.; Osborn, R.; Chmaissem, O.

    2015-09-01

    Combined neutron and x-ray diffraction experiments demonstrate the formation of a low-temperature minority magnetic tetragonal phase in Ba0.76K0.24Fe2As2 in addition to the majority magnetic, orthorhombic phase. The coincident enhancement in the magnetic (1/2 1/2 1) peaks shows that this minority phase is of the same type that was observed in Ba1 -xNaxFe2As2 (0.24 ≤x ≤0.28 ), in which the magnetic moments reorient along the c axis. This is evidence that the tetragonal magnetic phase is a universal feature of the hole-doped iron-based superconductors. The observations suggest that in this regime the energy levels of the C2 and C4 symmetric magnetic phases are very close.

  5. Vortex beam production and contrast enhancement from a magnetic spiral phase plate

    International Nuclear Information System (INIS)

    Blackburn, A.M.; Loudon, J.C.

    2014-01-01

    Electron vortex beam probes offer the possibility of mapping magnetic moments with atomic resolution. In this work we consider using the stray magnetic field produced from a narrow ferromagnetic rod magnetised along its long axis to produce a vortex beam probe, as an alternative to the currently used holographic apertures or gratings. We show through numerical modelling, electron holography observations and direct imaging of the electron probe, that a long narrow ferromagnetic rod induces a phase shift in the wave-function of passing electrons that approximately describes a helix in the regions near its ends. Directing this rod towards the optical axis of a charged-particle beam probe forming system at a limiting aperture position, with the free-end sufficiently close to the axis, is shown to offer a point spread function composed of vortex modes, with evidence of this appearing in observations of the electron probe formed from inserting a micro-fabricated CoFe rod into the beam path of a 300 keV transmission electron microscope (TEM). If the rod is arranged to contain the magnetic flux of h/e, thus producing a maximum phase shift of 2π, it produces a simple spiral-like phase contrast transfer function for weak phase objects. In this arrangement the ferromagnetic rod can be used as a phase plate, positioned at the objective aperture position of a TEM, yielding enhanced image contrast which is simulated to be intermediate between comparable Zernike and Hilbert phase plates. Though this aspect of the phase plate performance is not demonstrated here, agreement between our observations and models for the probe formed from an example rod containing a magnetic flux of ∼2.35h/e, indicate this phase plate arrangement could be a simple means of enhancing contrast and gaining additional information from TEM imaged weak phase samples, while also offering the capability to produce vortex beam probes. However, steps still need to be taken to either remove or improve the

  6. Magnetic excitations in ferromagnetic phase of MnP

    International Nuclear Information System (INIS)

    Yano, Shin-ichiro; Itoh, Shinichi; Yokoo, Tetsuya; Satoh, Setsuo; Kawana, Daichi; Kousaka, Yusuke; Akimitsu, Jun; Endoh, Yasuo

    2013-01-01

    Inelastic neutron scattering experiments were performed on an intermetallic compound, MnP. We used a newly developed High Resolution Chopper Spectrometer, HRC, for energy transfers E≤75meV, besides various triple axis spectrometers; LTAS for energy transfers E≤2meV, TOPAN for E≤7.5meV and TAS-1 for E≤35meV. Spin wave excitations were observed in the ferromagnetic phase of MnP in the entire Brillouin zone along the a ⁎ - and b ⁎ -axes. The zone boundary energies of spin waves were determined to be around 60 meV along the a ⁎ -axis and around 75 meV along the b ⁎ -axis, and the dispersion relations showed two branches for both axes. The observed dispersion relations of spin waves were well described by an isotropic Heisenberg interaction adding a single ion anisotropy with two sub-lattices. - Highlights: • Inelastic neutron scattering experiments were performed mainly using pulsed neutrons. • Spin waves were observed in the ferromagnetic phase of an intermetallic compound MnP. • The dispersion relations were determined entirely along the a ⁎ - and b ⁎ -axes. • We could describe the observed dispersion relations by a two sub-lattice model

  7. Phase transitions and magnetization of the mixed-spin Ising–Heisenberg double sawtooth frustrated ladder

    Science.gov (United States)

    Arian Zad, Hamid; Ananikian, Nerses

    2018-04-01

    The mixed spin-(1,1/2) Ising–Heisenberg double sawtooth ladder containing a mixture of both spin-1 and spin-1/2 nodal atoms, and the spin-1/2 interstitial dimers are approximately solved by the transfer-matrix method. Here, we study in detail the ground-state phase diagrams, also influences of the bilinear exchange coupling on the rungs and cyclic four-spin exchange interaction in square plaquette of each block on the magnetization and magnetic susceptibility of the suggested ladder at low temperature. Such a double sawtooth ladder may be found in a Shastry-Sutherland lattice-type. In spite of the spin ordering of odd and even blocks being different from each other, due to the commutation relation between all different block Hamiltonians, phase diagrams, magnetization behavior and thermodynamic properties of the model are the same for odd and even blocks. We show that at low temperature, both exchange couplings can change the quality and quantity of the magnetization plateaus versus the magnetic field changes. Specially, we find a new magnetization plateau M/Ms= 5/6 for this model. Besides, we examine the magnetic susceptibility and specific heat of the model in detail. It is proven that behaviors of the magnetization and the magnetic susceptibility coincide at low temperature. The specific heat displays diverse temperature dependencies, which include a Schottky-type peak at a special temperature interval. We observe that with increase of the bilinear exchange coupling on the rungs, second peak temperature dependence grows.

  8. Magnetic structure of phase II in U(Ru(0.96)Rh(0.04))2Si2 determined by neutron diffraction under pulsed high magnetic fields.

    Science.gov (United States)

    Kuwahara, K; Yoshii, S; Nojiri, H; Aoki, D; Knafo, W; Duc, F; Fabrèges, X; Scheerer, G W; Frings, P; Rikken, G L J A; Bourdarot, F; Regnault, L P; Flouquet, J

    2013-05-24

    We report neutron diffraction measurements on U(Ru(0.96)Rh(0.04))(2)Si(2) single crystal under pulsed high magnetic fields up to 30 T applied along the tetragonal c axis. The high-field experiments revealed that the field-induced phase II above 26 T corresponds to a commensurate up-up-down ferrimagnetic structure characterized by the wave vector q=(2/3,0,0) with the magnetic moments parallel to the c axis, which naturally explains the one-third magnetization plateau and the substantially changed Fermi surface in phase II. This a-axis modulated magnetic structure indicates that the phase II near the hidden order phase is closely related to the characteristic incommensurate magnetic fluctuations at Q(1)=(0.6,0,0) in the pure system URu(2)Si(2), in contrast to the pressure-induced antiferromagnetic order at Q(0)=(1,0,0).

  9. Pressure-induced magnetic collapse and metallization of molecular oxygen: The ζ-O2 phase

    International Nuclear Information System (INIS)

    Serra, S.; Chiarotti, G.; Scandolo, S.; Tosatti, E.

    1998-01-01

    The behavior of solid oxygen in the pressure range between 5-116 GPa is studied by ab-initio simulations, showing a spontaneous phase transformation from the antiferromagnetic insulating δ-O 2 phase to a non-magnetic, metallic molecular phase. The calculated static structure factor of this phase is in excellent agreement with X-ray diffraction data in the metallic ζ-O 2 phase above 96 GPa. We thus propose that ζ-O 2 should be base centered monoclinic with space group C2/m and 4 molecules per cell, suggesting a re-indexing of the experimental diffraction peaks. Physical constraints on the intermediate-pressure ε - O 2 phase are also obtained. (author)

  10. Magnetic properties of liquid-phase-assisted sintered MnZn ferrites

    Directory of Open Access Journals (Sweden)

    Drofenik Miha

    2002-01-01

    Full Text Available MnZn ferrites were sintered in the presence of a Bi2O3-SiO2 - rich liquid phase. The microstructure of MnZn-ferrite samples that contained various amounts of liquid phase during sintering was investigated. The results revealed that microstructure development and final magnetic permeability depend essentially on the amount of liquid phase present during sintering. The solution-reprecipitation (S-R process in MnZn ferrites starts when a continuous liquid-phase film is formed during grain growth. The status of the microstructure developed during solid-state sintering prior to the formation of the critical liquid-phase film is essential for the final microstructure developed during liquid-phase-assisted sintering.

  11. Experimental study of the magnetic phase transition in the MnSi itinerant helimagnet

    International Nuclear Information System (INIS)

    Stishov, S. M.; Petrova, A. E.; Khasanov, S.; Panova, G. Kh.; Shikov, A. A.; Lashley, J. C.; Wu, D.; Lograsso, T. A.

    2008-01-01

    Magnetic susceptibility, heat capacity, thermal expansion, and resistivity of a high-quality single crystal of MnSi were carefully studied at ambient pressure. The calculated change in magnetic entropy in the temperature range 0-30 K is less than 0.1R, a low value that emphasizes the itinerant nature of magnetism in MnSi. A linear temperature term dominates the behavior of the thermal expansion coefficient in the range 30-150 K, which correlates to a large enhancement of the linear electronic term in the heat capacity. A surprising similarity between variation of the heat capacity, the thermal expansion coefficient, and the temperature derivative of resistivity through the phase transition in MnSi is observed. Specific forms of the heat capacity, thermal expansion coefficient, and temperature derivative of resistivity at the phase transition to a helical magnetic state near 29 K are interpreted as a combination of sharp first-order features and broad peaks or shallow valleys of yet unknown origin. The appearance of these broad satellites probably hints at a frustrated magnetic state in MnSi slightly above the transition temperature. Present experimental findings bring the current views on the phase diagram of MnSi into question

  12. Collapsing cycloidal structures in the magnetic phase diagram of erbium

    DEFF Research Database (Denmark)

    Jehan, D.A.; McMorrow, D.F.; Simpson, J.A.

    1994-01-01

    approximately 20 K, the application of a field is found to favor cycloidal structures with modulation wave vectors of q(c) = (6/23)c*, (4/15)c*, and (2/7)c*. For fields above almost-equal-to 40 kOe, the (2/7) structure dominates the phase diagram. From a detailed study of this most stable cycloid, we determine...... how it distorts as the field is increased. In low fields, there is a spin reorientation, so that the plane of the cycloid becomes perpendicular to the applied field, while in larger fields, the cycloid collapses through a series of fanlike structures. At lower temperatures, as the field is increased...

  13. β-Detected NMR Search for Magnetic Phase Separation in Epitaxial GaAs:Mn

    Science.gov (United States)

    Song, Q.; Chow, K. H.; Miller, R. I.; Fan, I.; Hossain, M. D.; Kiefl, R. F.; Morris, G. D.; Kreitzman, S. R.; Levy, C. D. P.; Parolin, T. J.; Pearson, M. R.; Salman, Z.; Saadaoui, H.; Smadella, M.; Wang, D.; Yu, K. M.; Liu, X.; Furdyna, J. K.; MacFarlane, W. A.

    To test for the microscopic magnetic phase separation in the dilute magnetic semiconductor Ga1-xMnxAs sug-gested by low energy muon spin rotation measurements[1], we present a detailed analysis of the amplitudes of the 8Li β-detected nuclear magnetic resonance in an epitaxially grown thin film of x = 5.4% Mn doped GaAs on a semi-insulating GaAs substrate with magnetic transition temperature TC =72 K. The spectrum at 100 K corresponds to 73% of the full room temperature amplitude, and at 60 K to about 62%. The 11% loss of signal through the magnetic tran-sition is much smaller than that ∼ 50% found by low energy μSR[1], and may be entirely due to an amplitude change intrinsic to GaAs. This lack of evidence for phase separation is, however, consistent with the full volume fraction magnetism found by a second low energy μSR measurement on a different sample using weak transverse field[2].

  14. Dynamic magnetizations and dynamic phase transitions in a transverse cylindrical Ising nanowire

    International Nuclear Information System (INIS)

    Deviren, Bayram; Ertaş, Mehmet; Keskin, Mustafa

    2012-01-01

    In this paper, we extend the paper of Kaneyoshi (2010 J. Magn. Magn. Mater. 322 3410-5) to investigate the dynamic magnetizations and dynamic phase transitions of a transverse cylindrical Ising nanowire system by using the effective field theory with correlations and the Glauber-type stochastic dynamics under a time-dependent oscillating external magnetic field. The dynamic effective field equations for the average longitudinal and transverse magnetizations on the surface shell and core are derived by using the Glauber transition rates. Temperature dependences of the dynamic longitudinal magnetizations, the transverse magnetizations and the total magnetizations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system is strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, four different types of compensation behaviors in the Néel classification nomenclature exist in the system. The results are compared with some theoretical works and good overall agreement is observed. (paper)

  15. 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.

  16. Magnetic order, hysteresis, and phase coexistence in magnetoelectric LiCoPO4

    Science.gov (United States)

    Fogh, Ellen; Toft-Petersen, Rasmus; Ressouche, Eric; Niedermayer, Christof; Holm, Sonja Lindahl; Bartkowiak, Maciej; Prokhnenko, Oleksandr; Sloth, Steffen; Isaksen, Frederik Werner; Vaknin, David; Christensen, Niels Bech

    2017-09-01

    The magnetic phase diagram of magnetoelectric LiCoPO4 is established using neutron diffraction and magnetometry in fields up to 25.9 T applied along the crystallographic b axis. For fields greater than 11.9 T , the magnetic unit cell triples in size with propagation vector Q =(0 ,1/3 ,0 ) . A magnetized elliptic cycloid is formed with spins in the (b ,c ) plane and the major axis oriented along b . Such a structure allows for the magnetoelectric effect with an electric polarization along c induced by magnetic fields applied along b . Intriguingly, additional ordering vectors Q ≈(0 ,1/4 ,0 ) and Q ≈(0 ,1/2 ,0 ) appear for increasing fields in the hysteresis region below the transition field. Traces of this behavior are also observed in the magnetization. A simple model based on a mean-field approach is proposed to explain these additional ordering vectors. In the field interval 20.5 -21.0 T , the propagation vector Q =(0 ,1/3 ,0 ) remains but the spins orient differently compared to the cycloid phase. Above 21.0 T and up until saturation, a commensurate magnetic structure exists with a ferromagnetic component along b and an antiferromagnetic component along c .

  17. An Integrable SIW Phase Shifter in a Partially Magnetized Ferrite LTCC Package

    KAUST Repository

    Nafe, Ahmed

    2015-06-09

    There is a growing need for small size integrable phased antenna arrays for emerging satellite communications on-the-move applications. Traditional ferrite-based phase shifters are generally bulky due to the need of electromagnets for biasing, yielding them unsuitable for this kind of application. In this paper, a novel compact light-weight substrate integrated waveguide (SIW) based phase shifter realized in a multi-layer ferrite low-temperature co-fired ceramic package with embedded bias windings is reported. By using embedded windings and operating the material in a partially magnetized state, the required bias magnetic field could be significantly reduced from typically about 1000 Oe to less than 50 Oe. Moreover, the presented phase shifter has two modes of operations corresponding to two different biasing scenarios of the SIW, namely, symmetric and anti-symmetric bias. Under anti-symmetric bias, the phase shifter can achieve high nonreciprocal phase shift, whereas under symmetric bias, the phase shift is reciprocal, but the available phase shift is less than the anti-symmetric case. The fabricated prototype operates in the 11.5-13.5-GHz range and has a peak figure of merit (phase shift per decibel of loss) of 102°/dB and a maximum phase shift per unit length of 153°/cm, which are more than five times the previously reported figures for this technology. Due to the use of embedded windings, the presented phase shifter offers a huge size reduction from the order of cm3 to mm3, making it particularly useful for mobile phased-array applications. © 2015 IEEE.

  18. Structure of the incommensurate phase of the quantum magnet TiOCl

    Czech Academy of Sciences Publication Activity Database

    Schönleber, A.; van Smaalen, S.; Palatinus, Lukáš

    2006-01-01

    Roč. 73, č. 21 (2006), 214410/1-214410/4 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : spin-Peierls transition * incommensurate phase Subject RIV: BM - Solid Matter Physics ; Magnet ism Impact factor: 3.107, year: 2006

  19. Influence of 1523 K annealing on phase and magnetic properties in ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 34; Issue 5. Influence of 1523 K annealing on phase and magnetic properties in (Gd1−Er)5Si2Ge2 compounds. Xiang Chen Yungui Chen Yangbo Tang. Volume 34 Issue 5 August 2011 pp 1103-1108 ...

  20. Magnetic and Structural Phase Transitions in Thulium under High Pressures and Low Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Vohra, Yogesh K.; Tsoi, Georgiy M.; Samudrala, Gopi K. [UAB

    2017-10-01

    The nature of 4f electrons in many rare earth metals and compounds may be broadly characterized as being either "localized" or "itinerant", and is held responsible for a wide range of physical and chemical properties. The pressure variable has a very dramatic effect on the electronic structure of rare earth metals which in turn drives a sequence of structural and magnetic transitions. We have carried out four-probe electrical resistance measurements on rare earth metal Thulium (Tm) under high pressures to 33 GPa and low temperatures to 10 K to monitor the magnetic ordering transition. These studies are complemented by angle dispersive x-ray diffraction studies to monitor crystallographic phase transitions at high pressures and low temperatures. We observe an abrupt increase in magnetic ordering temperature in Tm at a pressure of 17 GPa on phase transition from ambient pressure hcp-phase to α-Sm phase transition. In addition, measured equation of state (EOS) at low temperatures show anomalously low thermal expansion coefficients likely linked to magnetic transitions.

  1. Effect of Co on the magnetism and phase stability of lithiated ...

    Indian Academy of Sciences (India)

    Unknown

    Effect of Co on the magnetism and phase stability of lithiated manganese oxides. R PRASAD*, R BENEDEK† and M M THACKERAY†. Department of Physics, Indian Institute of Technology, Kanpur 208 016, India. †Chemical Technology Division, Argonne National Laboratory, Argonne, IL 60439, USA. Abstract. We present ...

  2. Electronic structure and magnetic properties of selected lanthanide and actinide intermetallic Laves-phase alloys

    DEFF Research Database (Denmark)

    Eriksson, Olle; Johansson, Börje; Brooks, M. S. S.

    1989-01-01

    The electronic structure and magnetic properties of some yttrium and uranium Laves-phase pseudobinary alloys with 3d elements have been calculated. The calculations were done by simulating the electronic structure of the alloy by that of an ordered compound with the same stoichiometry. In general...

  3. Study of a Nine-Phase Fault Tolerant Permanent Magnet Starter-Alternator

    OpenAIRE

    RUBA Mircea; SURDU Felicia; SZABÓ Loránd

    2011-01-01

    The paper presents a study on a nine-phasepermanent magnet synchronous starter-alternator forautomotive applications, analyzing different convertertopologies, detailing the simulation programs anddiscussing the results in different operating conditions,from entire healthy machine to several faulted phases.The comparison between the two converter topologiescontrolling the multiphase machine highlights theincreased fault tolerance, hence the reliability of suchstarter-alternator structures. Nev...

  4. Predicted stability, structures, and magnetism of 3d transition metal nitrides: the M4N phases

    NARCIS (Netherlands)

    Fang, C.M.; Koster, R.S.; Li, W.F.; van Huis, M.A.

    2014-01-01

    The 3d transition metal nitrides M4N (Sc4N, Ti4N, V4N, Cr4N, Mn4N, Fe4N, Co4N, Ni4N, and Cu4N) have unique phase relationships, crystal structures, and electronic and magnetic properties. Here we present a systematic density functional theory (DFT) study on these transition metal nitrides, assessing

  5. Phase equilibria of Fe-C binary alloys in a magnetic field

    Science.gov (United States)

    England, Roger Dale

    The deployment of high flux magnetic processing in industry requires the ability to model the expected results of a proposed processing, and the current assumptions in the literature did not reflect the actual outcome in measurements of ductile iron. Simple binary iron-carbon alloys of less than one weight percent carbon were thermo-magnetically processed and then compared with Gibbs free energy phase transformation predictions. The data was used to quantify the change in the Gibbs free energy associated with the addition of a static high flux magnetic field, which is complicated by the change in magnetic response as the iron carbon alloys pass through the Curie point. A current common practice is to modify Gibbs free energy by -12J per mole per Tesla applied, as has been reported in the literature. This current prediction practice was employed in initial experiments for this work and the experimental data did not agree with these predicted values. This work suggests two specific influences that affect the model, chemistry and magnetic dipole changes. First, that the influence of alloying elements in the original chemistry, as the samples in the literature were a manganese alloy with 0.45 weight percent carbon, as well as not being precisely controlled for tramp elements that commonly occur in recycled material, created a change that was not predicted and therefore the temperatures were incorrect. Also, the phase transformation in a high flux magnetic field was measured to have a different response under warming versus cooling than the normal hysteresis under ambient magnetism. The change in Gibbs free energy for the binary alloys was calculated as -3J per mole per Tesla in warming, and -8J per mole per tesla in cooling. The change from these values to the -12J per mole per Tesla previously reported is attributed to the change in chemistry. This work attributes the published increase in physical properties to the Hall-Petch relation as a result of the finer product

  6. Mott-insulating phases and magnetism of fermions in a double-well optical lattice

    International Nuclear Information System (INIS)

    Wang, Xin; Zhou, Qi; Das Sarma, S.

    2011-01-01

    We theoretically investigate, using nonperturbative strong correlation techniques, Mott-insulating phases and magnetic ordering of two-component fermions in a two-dimensional double-well optical lattice. At filling of two fermions per site, there are two types of Mott insulators, one of which is characterized by spin-1 antiferromagnetism below the Neel temperature. The superexchange interaction in this system is induced by the interplay between the interband interaction and the spin degree of freedom. A great advantage of the double-well optical lattice is that the magnetic quantum phase diagram and the Neel temperature can be easily controlled by tuning the orbital energy splitting of the two-level system. Particularly, the Neel temperature can be one order of magnitude larger than that in standard optical lattices, facilitating the experimental search for magnetic ordering in optical lattice systems.

  7. Spherical agarose-coated magnetic nanoparticles functionalized with a new salen for magnetic solid-phase extraction of uranyl ion

    International Nuclear Information System (INIS)

    Serenjeh, Fariba Nazari; Hashemi, Payman; Ghiasvand, Ali Reza; Naeimi, Hossein; Zakerzadeh, Elham

    2016-01-01

    The authors describe a method for magnetic solid phase extraction of uranyl ions from water samples. It is based on the use of spherical agarose-coated magnetic nanoparticles along with magnetic field agitation. The salen type Schiff base N,N’-bis(4-hydroxysalicylidene)-1,2-phenylenediamine was synthesized from resorcinol in two steps and characterized by infrared and nucleic magnetic resonance spectroscopies. The particles were then activated by an epichlorohydrin method and functionalized with the Schiff base which acts as a selective ligand for the extraction of UO 2 (II). Following preconcentration and elution with HCl, the ions were quantified by spectrophotometry using Arsenazo III as the indicator. The effects of pH value, ionic strength and amount of the adsorbent on the extraction of UO 2 (II) were optimized by a multivariate central composite design method. Six replicate analyses under optimized conditions resulted in a recovery of 96.6 % with a relative standard deviation of 3.4 % for UO 2 (II). The detection limit of the method (at a signal-to-noise ratio of 3σ) is 10 μg L -1 . The method was successfully applied to the determination of UO 2 (II) in spiked water samples. (author)

  8. Open-Phase Fault Tolerance Techniques of Five-Phase Dual-Rotor Permanent Magnet Synchronous Motor

    Directory of Open Access Journals (Sweden)

    Jing Zhao

    2015-11-01

    Full Text Available Multi-phase motors are gaining more attention due to the advantages of good fault tolerance capability and high power density, etc. By applying dual-rotor technology to multi-phase machines, a five-phase dual-rotor permanent magnet synchronous motor (DRPMSM is researched in this paper to further promote their torque density and fault tolerance capability. It has two rotors and two sets of stator windings, and it can adopt a series drive mode or parallel drive mode. The fault-tolerance capability of the five-phase DRPMSM is researched. All open circuit fault types and corresponding fault tolerance techniques in different drive modes are analyzed. A fault-tolerance control strategy of injecting currents containing a certain third harmonic component is proposed for five-phase DRPMSM to ensure performance after faults in the motor or drive circuit. For adjacent double-phase faults in the motor, based on where the additional degrees of freedom are used, two different fault-tolerance current calculation schemes are adopted and the torque results are compared. Decoupling of the inner motor and outer motor is investigated under fault-tolerant conditions in parallel drive mode. The finite element analysis (FMA results and co-simulation results based on Simulink-Simplorer-Maxwell verify the effectiveness of the techniques.

  9. Costs of magnets for large fusion power reactors: Phase I, cost of superconductors for dc magnets

    International Nuclear Information System (INIS)

    Powell, J.R.

    1972-01-01

    Projections are made for dc magnet conductor costs for large fusion power reactors. A mature fusion economy is assumed sometime after 2000 A. D. in which approximately 90,000 MW(e) of fusion reactors are constructed/year. State of the art critical current vs. field characteristics for superconductors are used in these projections. Present processing techniques are used as a basis for the design of large plants sized to produce approximately one-half of the conductor needed for the fusion magnets. Multifilamentary Nb-Ti, Pb-Bi in glass fiber, GE Nb 3 Sn tape, Linde plasma sprayed Nb 3 Sn tape, and V 3 Ga tape superconductors are investigated, together with high purity aluminum cryoconductor. Conductor costs include processing costs [capital (equipment plus buildings), labor, and operating] and materials costs. Conductor costs are compared for two sets of material costs: current (1971 A. D.) costs, and projected (after 2000 A. D.) costs. (U.S.)

  10. STRIPE: Remote Driving Using Limited Image Data

    Science.gov (United States)

    Kay, Jennifer S.

    1997-01-01

    Driving a vehicle, either directly or remotely, is an inherently visual task. When heavy fog limits visibility, we reduce our car's speed to a slow crawl, even along very familiar roads. In teleoperation systems, an operator's view is limited to images provided by one or more cameras mounted on the remote vehicle. Traditional methods of vehicle teleoperation require that a real time stream of images is transmitted from the vehicle camera to the operator control station, and the operator steers the vehicle accordingly. For this type of teleoperation, the transmission link between the vehicle and operator workstation must be very high bandwidth (because of the high volume of images required) and very low latency (because delayed images can cause operators to steer incorrectly). In many situations, such a high-bandwidth, low-latency communication link is unavailable or even technically impossible to provide. Supervised TeleRobotics using Incremental Polyhedral Earth geometry, or STRIPE, is a teleoperation system for a robot vehicle that allows a human operator to accurately control the remote vehicle across very low bandwidth communication links, and communication links with large delays. In STRIPE, a single image from a camera mounted on the vehicle is transmitted to the operator workstation. The operator uses a mouse to pick a series of 'waypoints' in the image that define a path that the vehicle should follow. These 2D waypoints are then transmitted back to the vehicle, where they are used to compute the appropriate steering commands while the next image is being transmitted. STRIPE requires no advance knowledge of the terrain to be traversed, and can be used by novice operators with only minimal training. STRIPE is a unique combination of computer and human control. The computer must determine the 3D world path designated by the 2D waypoints and then accurately control the vehicle over rugged terrain. The human issues involve accurate path selection, and the

  11. Determining the magnetically nonlinear characteristics of a three phase core-type power transformer

    International Nuclear Information System (INIS)

    Dolinar, Matjaz; Stumberger, Gorazd; Polajzer, Bostjan; Dolinar, Drago

    2006-01-01

    This paper presents nonlinear iron core model of a three-phase, three-limb power transformer which is given by the current-dependant characteristics of flux linkages. The magnetically nonlinear characteristics are determined by controlled magnetic excitation of all three limbs which allows to take into account the variable magnetic-cross couplings between different coils placed on limbs, caused by saturation. The corresponding partial derivatives of measured flux linkage characteristics are used in the transformer circuit model as a magnetically nonlinear iron core model in order to analyze the behaviour of a nonsymmetrically excited transformer. Numerical results using transformer model with the determined iron core model agree very well with the measured results

  12. Stable tetragonal phase and magnetic properties of Fe-doped HfO2 nanoparticles

    Directory of Open Access Journals (Sweden)

    T. S. N. Sales

    2017-05-01

    Full Text Available In this paper, the effect in structural and magnetic properties of iron doping with concentration of 20% in hafnium dioxide (HfO2 nanoparticles is investigated. HfO2 is a wide band gap oxide with great potential to be used as high-permittivity gate dielectrics, which can be improved by doping. Nanoparticle samples were prepared by sol-gel chemical method and had their structure, morphology, and magnetic properties, respectively, investigated by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM with electron back scattering diffraction (EBSD, and magnetization measurements. TEM and SEM results show size distribution of particles in the range from 30 nm to 40 nm with small dispersion. Magnetization measurements show the blocking temperature at around 90 K with a strong paramagnetic contribution. XRD results show a major tetragonal phase (94%.

  13. Phase-dependent dynamic potential of magnetically coupled two-degree-of-freedom bistable energy harvester.

    Science.gov (United States)

    Kim, Pilkee; Nguyen, Minh Sang; Kwon, Ojin; Kim, Young-Jin; Yoon, Yong-Jin

    2016-09-28

    A system of magnetically coupled oscillators has been recently considered as a promising compact structure to integrate multiple bistable energy harvesters (BEHs), but its design is not straightforward owing to its varying potential energy pattern, which has not been understood completely yet. This study introduces the concept of phase-dependent dynamic potential in a magnetically coupled BEH system with two degrees of freedom (DOFs) to explain the underlying principle of the complicated dynamics of the system. Through theoretical simulations and analyses, two distinct dynamic regimes, called the out-of-phase and in-phase mode regimes in this report, are found to exist in the frequency regions of the 1 st and 2 nd primary intrawell resonances. For the out-of-phase mode regime, the frequency displacement (and output power) responses of the 2-DOF BEH system exhibit typical double-well dynamics, whereas for the in-phase mode regime, only single-well dynamics is observed though the system is statically bistable. These dynamic regimes are also revealed to be caused by the difference in the dynamic potential energy trajectories propagating on a high-dimensional potential energy surface. The present approach to the dynamics of the 2-DOF BEH system can be extended and applied to higher-DOF systems, which sheds light on compact and efficient designs of magnetically coupled BEH chain structures.

  14. Effect of interionic anisotropy on the phase states and spectra of a non-Heisenberg magnet with S = 1

    Energy Technology Data Exchange (ETDEWEB)

    Kosmachev, O. A.; Krivtsova, A. V.; Fridman, Yu. A., E-mail: yuriifridman@gmail.com [Vernadskii Crimea Federal University (Russian Federation)

    2016-02-15

    We study the effect of interionic anisotropy on the phase states of a non-Heisenberg ferromagnet with magnetic ion spin S = 1. It is shown that depending on the relation between the interionic anisotropy constants, uniaxial and angular ferromagnetic and nonmagnetic phases exist in the system. We analyze the dynamic properties of the system in the vicinity of orientational phase transitions, as well as a phase transition in the magnetic moment magnitude. It is shown that orientational phase transitions in ferromagnetic and nematic phases can be first- as well as second-order.

  15. Thickness measurement of soft thin films on periodically patterned magnetic substrates by phase difference magnetic force microscopy.

    Science.gov (United States)

    Passeri, D; Dong, C; Angeloni, L; Pantanella, F; Natalizi, T; Berlutti, F; Marianecci, C; Ciccarello, F; Rossi, M

    2014-01-01

    The need for accurate measurement of the thickness of soft thin films is continuously encouraging the development of techniques suitable for this purpose. We propose a method through which the thickness of the film is deduced from the quantitative measurement of the contrast in the phase images of the sample surface acquired by magnetic force microscopy, provided that the film is deposited on a periodically patterned magnetic substrate. The technique is demonstrated by means of magnetic substrates obtained from standard floppy disks. Colonies of Staphylococcus aureus adherent to such substrates were used to obtain soft layers with limited lateral (a few microns) and vertical (hundreds of nanometers) size. The technique is described and its specific merits, limitations and potentialities in terms of accuracy and measurable thickness range are discussed. These parameters depend on the characteristics of the sensing tip/cantilever as well as of the substrates, the latter in terms of spatial period and homogeneity of the magnetic domains. In particular, with the substrates used in this work we evaluated an uncertainty of about 10%, a limit of detection of 50-100 nm and an upper detection limit (maximum measurable thickness) of 1 μm, all obtained with standard lift height values (50-100 nm). Nonetheless, these parameters can be easily optimized by selecting/realizing substrates with suitable spacing and homogeneity of the magnetic domains. For example, the upper detection limit can be increased up to 25-50 μm while the limit of detection can be reduced to a few tens of nanometers or a few nanometers. © 2013 Elsevier B.V. All rights reserved.

  16. Electric field-driven, magnetically-stabilized ferro-emulsion phase contactor

    Science.gov (United States)

    Scott, Timothy C.

    1990-01-01

    Methods and systems for interfacial surface area contact between a dispersed phase liquid and a continuous phase liquid in counter-current flow for purposes such as solvent extraction. Initial droplets of a dispersed phase liquid material containing ferromagnetic particles functioning as a "packing" are introduced to a counter-current flow of the continuous phase. A high intensity pulsed electric field is applied so as to shatter the initial droplets into a ferromagnetic emulsion comprising many smaller daughter droplets having a greater combined total surface area than that of the initial droplets in contact with the continuous phase material. A magnetic field is applied to control the position of the ferromagnetic emulsion for enhanced coalescence of the daughter droplets into larger reformed droplets.

  17. High-pressure magnetic phase diagram of CeP studied by neutron diffraction

    International Nuclear Information System (INIS)

    Hannan, A.; Kohgi, M.; Iwasa, K.; Osakabe, T.

    2002-01-01

    Neutron-diffraction experiments have been performed in order to clarify the magnetic structures of CeP under pressures above 1.9 GPa using a sapphire-anvil cell. The P-T phase diagram up to 2.8 GPa has been investigated. Some new phases have been found, for example the phase 2 + (↑ ↑ ↓ ↓ ↑ ↑) under the pressure of 1.9 GPa. Type-IA antiferromagnetic structure (↑ ↑ ↓ ↓) was found below 22.5 and 45 K at 1.9 and 2.2 GPa, respectively. A phase characterized by the wave vector k=1/3 and a ferromagnetic phase were observed in the pressure range 2.5-2.8 GPa. (orig.)

  18. Crystal shapes on striped surface domains

    International Nuclear Information System (INIS)

    Valencia, Antoni

    2004-01-01

    The equilibrium shapes of a simple cubic crystal in contact with a planar chemically patterned substrate are studied theoretically using an effective interface model. The substrate is primarily made of lyophobic material and is patterned with a lyophilic (easily wettable) stripe domain. Three regimes can be distinguished for the equilibrium shapes of the crystal. The transitions between these regimes as the volume of the crystal is changed are continuous or discontinuous depending on the strength of the couplings between the crystal and the lyophilic and lyophobic surface domains. If the crystal grows through a series of states close to equilibrium, the discontinuous transitions correspond to growth instabilities. These transitions are compared with similar results that have been obtained for a volume of liquid wetting a lyophilic stripe domain

  19. The preparation of immunochromatographic stripe of methamphetamine

    International Nuclear Information System (INIS)

    Jiang Jing; Liu Yibing; Zhou Ling; Guo Weizheng

    2004-01-01

    A gold immunochromatographic assay (GICA) is developed for methamphetamine in urine. Colloidal gold is obtained by reducing the gold chloride with sodium citrate, and labeled methamphetamine monoclonal antibody. The drug or metabolite competes with the immobilized drug conjugate in the test area for the limited colloidal gold-labeled antibody complex in which the stripe is made to screen the drug abuser. This method has sensitivity of 1000 μg/L, and without cross-reaction with some drugs

  20. Effects of induced magnetic field on large scale pulsed MHD generator with two phase flow

    International Nuclear Information System (INIS)

    Ishikawa, M.; Koshiba, Y.; Matsushita, T.

    2004-01-01

    A large pulsed MHD generator 'SAKHALIN' was constructed in Russia (the former Soviet-Union) and operated with solid fuels. The 'SAKHALIN' with the channel length of 4.5 m could demonstrate the electric power output of 510 MW. The effects of induced magnetic field and two phase flow on the shock wave within the 'SAKHALIN' generator have been studied by time dependent, one dimensional analyses. It has been shown that the magnetic Reynolds number is about 0.58 for Run No. 1, and the induced magnetic flux density is about 20% at the entrance and exit of the MHD channel. The shock wave becomes stronger when the induced magnetic field is taken into account, when the operation voltage becomes low. The working gas plasma contains about 40% of liquid particles (Al 2 O 3 ) in weight, and the present analysis treats the liquid particles as another gas. In the case of mono-phase flow, the sharp shock wave is induced when the load voltage becomes small such as 500 V with larger Lorentz force, whereas in the case of two phase flow, the shock wave becomes less sharp because of the interaction with liquid particles

  1. Hyperfine field and magnetic structure in the B phase of CeCoIn5

    Energy Technology Data Exchange (ETDEWEB)

    Graf, Matthias J [Los Alamos National Laboratory; Curro, Nicholas J [UNIV OF CAL; Young, Ben - Li [NATIONAL CHIAO UNIV; Urbano, Ricardo R [FL STATE UNIV

    2009-01-01

    We re-analyze Nuclear Magnetic Resonance (NMR) spectra observed at low temperatures and high magnetic fields in the field-induced B-phase of CeCoIn{sub 5}. The NMR spectra are consistent with incommensurate antiferromagnetic order of the Ce magnetic moments. However, we find that the spectra of the In(2) sites depend critically on the direction of the ordered moments, the ordering wavevector and the symmetry of the hyperfine coupling to the Ce spins. Assuming isotropic hyperfine coupling, the NMR spectra observed for H {parallel} [100] are consistent with magnetic order with wavevector Q = {pi}(1+{delta}/a, 1/a, 1/c) and Ce moments ordered antiferromagnetically along the [100] direction in real space. If the hyperfine coupling has dipolar symmetry, then the NMR spectra require Ce moments along the [001] direction. The dipolar scenario is also consistent with recent neutron scattering measurements that find an ordered moment of 0.15{micro}{sub B} along [001] and Q{sub n} = {pi}(1+{delta}/a, 1+{delta}c, 1/c) with incommensuration {delta} = 0.12 for field H {parallel} [1{bar 1}0]. Using these parameters, we find that the hyperfine field is consistent with both experiments. We speculate that the B phase of CeCoIn{sub 5} represents an intrinsic phase of modulated superconductivity and antiferromagnetism that can only emerge in a highly clean system.

  2. Critical point in the QCD phase diagram for extremely strong background magnetic fields

    International Nuclear Information System (INIS)

    Endrödi, Gergely

    2015-01-01

    Lattice simulations have demonstrated that a background (electro)magnetic field reduces the chiral/deconfinement transition temperature of quantum chromodynamics for eB<1 GeV 2 . On the level of observables, this reduction manifests itself in an enhancement of the Polyakov loop and in a suppression of the light quark condensates (inverse magnetic catalysis) in the transition region. In this paper, we report on lattice simulations of 1+1+1-flavor QCD at an unprecedentedly high value of the magnetic field eB=3.25 GeV 2 . Based on the behavior of various observables, it is shown that even at this extremely strong field, inverse magnetic catalysis prevails and the transition, albeit becoming sharper, remains an analytic crossover. In addition, we develop an algorithm to directly simulate the asymptotically strong magnetic field limit of QCD. We find strong evidence for a first-order deconfinement phase transition in this limiting theory, implying the presence of a critical point in the QCD phase diagram. Based on the available lattice data, we estimate the location of the critical point.

  3. Magnetic Fields at First Order Phase Transition: A Threat to Electroweak Baryogenesis

    CERN Document Server

    De Simone, Andrea; Quiros, Mariano; Riotto, Antonio

    2011-01-01

    The generation of the observed baryon asymmetry may have taken place during the electroweak phase transition, thus involving physics testable at LHC, a scenario dubbed electroweak baryogenesis. In this paper we point out that the magnetic field which is produced in the bubbles of a first order phase transition endangers the baryon asymmetry produced in the bubble walls. The reason being that the produced magnetic field couples to the sphaleron magnetic moment and lowers the sphaleron energy; this strengthens the sphaleron transitions inside the bubbles and triggers a more effective wash out of the baryon asymmetry. We apply this scenario to the Minimal Supersymmetric extension of the Standard Model (MSSM) where, in the absence of a magnetic field, successful electroweak baryogenesis requires the lightest CP-even Higgs and the right-handed stop masses to be lighter than about 127 GeV and 120 GeV, respectively. We show that even for moderate values of the magnetic field, the Higgs mass required to preserve the ...

  4. Dynamic phase transitions in a cylindrical Ising nanowire under a time-dependent oscillating magnetic field

    International Nuclear Information System (INIS)

    Deviren, Bayram; Kantar, Ersin; Keskin, Mustafa

    2012-01-01

    The dynamic phase transitions in a cylindrical Ising nanowire system under a time-dependent oscillating external magnetic field for both ferromagnetic and antiferromagnetic interactions are investigated within the effective-field theory with correlations and the Glauber-type stochastic dynamics approach. The effective-field dynamic equations for the average longitudinal magnetizations on the surface shell and core are derived by employing the Glauber transition rates. Temperature dependence of the dynamic magnetizations, the dynamic total magnetization, the hysteresis loop areas and the dynamic correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, five different types of compensation behaviors in the Néel classification nomenclature exist in the system. The system also exhibits a reentrant behavior. - Highlights: ► The dynamic aspects of a cylindrical Ising nanowire are investigated in detail. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► We studied both the FM and AFM interactions within the EFT with correlations. ► Some characteristic phenomena are found depending on the interaction parameters. ► We obtained five different types of compensation behaviors and reentrant behavior.

  5. Dynamic phase transitions in a cylindrical Ising nanowire under a time-dependent oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Kantar, Ersin [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-07-15

    The dynamic phase transitions in a cylindrical Ising nanowire system under a time-dependent oscillating external magnetic field for both ferromagnetic and antiferromagnetic interactions are investigated within the effective-field theory with correlations and the Glauber-type stochastic dynamics approach. The effective-field dynamic equations for the average longitudinal magnetizations on the surface shell and core are derived by employing the Glauber transition rates. Temperature dependence of the dynamic magnetizations, the dynamic total magnetization, the hysteresis loop areas and the dynamic correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, five different types of compensation behaviors in the Neel classification nomenclature exist in the system. The system also exhibits a reentrant behavior. - Highlights: Black-Right-Pointing-Pointer The dynamic aspects of a cylindrical Ising nanowire are investigated in detail. Black-Right-Pointing-Pointer The dynamic magnetizations, hysteresis loop areas and correlations are calculated. Black-Right-Pointing-Pointer We studied both the FM and AFM interactions within the EFT with correlations. Black-Right-Pointing-Pointer Some characteristic phenomena are found depending on the interaction parameters. Black-Right-Pointing-Pointer We obtained five different types of compensation behaviors and reentrant behavior.

  6. Distortion induced magnetic phase transition in cubic BaFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Gul, E-mail: gulrahman@qau.edu.pk [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Morbec, Juliana M. [The Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637 (United States); Ferradás, Rubén; García-Suárez, Víctor M. [Departamento de Física, Universidad de Oviedo, 33007 Oviedo (Spain); Nanomaterials and Nanotechnology Research Center (CINN) (Spain); English, Niall J. [The SFI Strategic Research Cluster in Solar Energy Conversion, School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4 (Ireland)

    2016-03-01

    The electronic and magnetic structures of cubic BaFeO{sub 3} (BFO) in the ferromagnetic (FM) and antiferromagnetic (AFM) states are studied using density functional theory (DFT) with the local spin density approximation (LSDA) and the generalized gradient approximation (GGA), with and without a Coulomb U term. Our LSDA/GGA and LSDA+U/GGA+U results show that cubic BFO has a FM ground state, in agreement with recent experimental studies. Two types of distortions, denoted as D1 and D2, are considered. The source of the distortion in the D1 (D2) case is the displacement of the oxygen (iron) atoms from their equilibrium positions. FM to ferrimagnetic (FIM) and FM to AFM magnetic phase transitions are found in the D1 and D2 distortions, respectively. Larger strains are required for the FM–AFM transition as compared to the FM–FIM. DFT+U calculations also show that the magnetic moments dramatically decrease at large strains due to strong overlapping between the iron and oxygen atoms. The origin of these transitions is discussed in terms of a competition between double exchange and superexchange interactions. From these results it is possible to conclude that oxygen and iron displacements are responsible for the magnetic phase transitions and the reduction of the magnetic moments in BFO. - Highlights: • Ferromagnetism (FM) and antiferromagnetism (AFM). • Distortion-induced FM–AFM transition. • Half-metals. • Density Functional. • Theory Electronic Structure.

  7. Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

    Directory of Open Access Journals (Sweden)

    Rachana Gupta

    2015-09-01

    Full Text Available Cobalt nitride (Co-N thin films prepared using a reactive magnetron sputtering process are studied in this work. During the thin film deposition process, the relative nitrogen gas flow (RN2 was varied. As RN2 increases, Co(N, Co4N, Co3N and CoN phases are formed. An incremental increase in RN2, after emergence of Co4N phase at RN2 = 10%, results in a linear increase of the lattice constant (a of Co4N. For RN2 = 30%, a maximizes and becomes comparable to its theoretical value. An expansion in a of Co4N, results in an enhancement of the magnetic moment, to the extent that it becomes even larger than pure Co. Such larger than pure metal magnetic moment for tetra-metal nitrides (M4N have been theoretically predicted. Incorporation of N atoms in M4N configuration results in an expansion of a (relative to pure metal and enhances the itinerary of conduction band electrons leading to larger than pure metal magnetic moment for M4N compounds. Though a higher (than pure Fe magnetic moment for Fe4N thin films has been evidenced experimentally, higher (than pure Co magnetic moment is evidenced in this work.

  8. Absence of magnetic ordering and field-induced phase diagram in the gadolinium aluminum garnet

    Science.gov (United States)

    Florea, O.; Lhotel, E.; Jacobsen, H.; Knee, C. S.; Deen, P. P.

    2017-12-01

    The robustness of spin liquids with respect to small perturbations, and the way magnetic frustration can be lifted by slight changes in the balance between competing magnetic interactions, remains a rich and open issue. We address this question through the study of the gadolinium aluminum garnet Gd3Al5O12 , a related compound to the extensively studied Gd3Ga5O12 . We report on its magnetic properties at very low temperatures. We show that despite a freezing at about 300 mK, no magnetic transition is observed, suggesting the presence of a spin-liquid state down to the lowest temperatures, similarly to Gd3Ga5O12 , in spite of a larger ratio between exchange and dipolar interactions. Finally, the phase diagram as a function of field and temperature is strongly reminiscent of the one reported in Gd3Ga5O12 . This study reveals the robust nature of the spin-liquid phase for Gd ions on the garnet lattice, in stark contrast to Gd ions on the pyrochlore lattice for which a slight perturbation drives the compound into a range of magnetically ordered states.

  9. 3D face recognition using isogeodesic stripes.

    Science.gov (United States)

    Berretti, Stefano; Del Bimbo, Alberto; Pala, Pietro

    2010-12-01

    In this paper, we present a novel approach to 3D face matching that shows high effectiveness in distinguishing facial differences between distinct individuals from differences induced by nonneutral expressions within the same individual. The approach takes into account geometrical information of the 3D face and encodes the relevant information into a compact representation in the form of a graph. Nodes of the graph represent equal width isogeodesic facial stripes. Arcs between pairs of nodes are labeled with descriptors, referred to as 3D Weighted Walkthroughs (3DWWs), that capture the mutual relative spatial displacement between all the pairs of points of the corresponding stripes. Face partitioning into isogeodesic stripes and 3DWWs together provide an approximate representation of local morphology of faces that exhibits smooth variations for changes induced by facial expressions. The graph-based representation permits very efficient matching for face recognition and is also suited to being employed for face identification in very large data sets with the support of appropriate index structures. The method obtained the best ranking at the SHREC 2008 contest for 3D face recognition. We present an extensive comparative evaluation of the performance with the FRGC v2.0 data set and the SHREC08 data set.

  10. Classifying Variable Sources in SDSS Stripe 82

    Science.gov (United States)

    Willecke Lindberg, Christina

    2018-01-01

    SDSS (Sloan Digital Sky Survey) Stripe 82 is a well-documented and researched region of the sky that does not have all of its ~67,500 variable objects labeled. By collecting data and consulting different catalogs such as the Catalina Survey, we are able to slowly cross-match more objects and add classifications within the Stripe 82 catalog. Such matching is performed either by pairing SDSS identification numbers, or by converting and comparing the coordinates of every object within the Stripe 82 catalog to every object within the classified catalog, such as the Catalina Survey catalog. If matching is performed with converted coordinates, a follow-up check is performed to ascertain that the magnitudes of the paired objects are within a reasonable margin of error and that objects have not been mismatched. Once matches have been confirmed, the light curves of classified objects can then be used to determine features that most effectively separate the different types of variable objects in feature spaces. By classifying variable objects, we can construct a reference for subsequent large research surveys, such as LSST (the Large Synoptic Survey Telescope), that could utilize SDSS data as a training set for its own classifications.

  11. Occupational Noise Reduction in CNC Striping Process

    Science.gov (United States)

    Mahmad Khairai, Kamarulzaman; Shamime Salleh, Nurul; Razlan Yusoff, Ahmad

    2018-03-01

    Occupational noise hearing loss with high level exposure is common occupational hazards. In CNC striping process, employee that exposed to high noise level for a long time as 8-hour contributes to hearing loss, create physical and psychological stress that reduce productivity. In this paper, CNC stripping process with high level noises are measured and reduced to the permissible noise exposure. First condition is all machines shutting down and second condition when all CNC machine under operations. For both conditions, noise exposures were measured to evaluate the noise problems and sources. After improvement made, the noise exposures were measured to evaluate the effectiveness of reduction. The initial average noise level at the first condition is 95.797 dB (A). After the pneumatic system with leakage was solved, the noise reduced to 55.517 dB (A). The average noise level at the second condition is 109.340 dB (A). After six machines were gathered at one area and cover that area with plastic curtain, the noise reduced to 95.209 dB (A). In conclusion, the noise level exposure in CNC striping machine is high and exceed the permissible noise exposure can be reduced to acceptable levels. The reduction of noise level in CNC striping processes enhanced productivity in the industry.

  12. Microstructure and Phase Analysis in Mn-Al and Zr-Co Permanent Magnets

    Science.gov (United States)

    Lucis, Michael J.

    In America's search for energy independence, the development of rare-earth free permanent magnets is one hurdle that still stands in the way. Permanent magnet motors provide a higher efficiency than induction motors in applications such as hybrid vehicles and wind turbines. This thesis investigates the ability of two materials, Mn-Al and Zr-Co, to fill this need for a permanent magnet material whose components are readily available within the U.S. and whose supply chain is more stable than that of the rare-earth materials. This thesis focuses on the creation and optimization of these two materials to later be used as the hard phase in nanocomposites with high energy products (greater than 10 MGOe). Mn-Al is capable of forming the pure L10 structure at a composition of Mn54Al43C3. When Mn is replaced by Fe or Cu using the formula Mn48Al43C3T6 the anisotropy constant is lowered from 1.3·107 ergs/cm3 to 1.0·107 ergs/cm3 and 0.8·10 7 ergs/cm3 respectively. Previous studies have reported a loss in magnetization in Mn-Al alloys during mechanical milling. The reason for this loss in magnetization was investigated and found to be due to the formation of the equilibrium beta-Mn phase of the composition Mn3Al2 and not due to oxidation or site disorder. It was also shown that fully dense Mn-Al permanent magnets can be created at hot pressing temperatures at or above 700°C and that the epsilon-phase to tau-phase transition and consolidation can be combined into a single processing step. The addition of small amounts of Cu to the alloy, 3% atomic, can increase the compaction density allowing high densities to be achieved at lower pressing temperatures. While the structure is still under debate, alloys at the composition Zr2Co11 in the Zr-Co system have been shown to have hard magnetic properties. This thesis shows that multiple structures exist at this Zr2Co11 composition and that altering the cooling rate during solidification of the alloy affects the ratio of the phase

  13. Parallel carbon nanotube stripes in polymer thin film with remarkable conductive anisotropy.

    Science.gov (United States)

    Huang, Jinrui; Zhu, Yutian; Jiang, Wei; Yin, Jinghua; Tang, Qingxin; Yang, Xiaodong

    2014-02-12

    In our previous study ( Mao et al. J. Phys. Chem. Lett. 2013 , 4 , 43 - 47 ), we proposed a novel method, that is, the shear-flow-induced hierarchical self-assembly of two-dimensional fillers (octadecylamine-functionalized graphene) into the well-ordered parallel stripes in a polymer matrix, to fabricate the anisotropic conductive materials. In this study, we extend this method to one-dimensional multiwalled carbon nanotubes (MWCNTs). Under the induction of shear flow, the dispersed poly(styrene ethylene/butadiene-styrene) (SEBS) phase and MWCNTs can spontaneously assemble into well-ordered parallel stripes in the polypropylene (PP) thin film. The electrical measurements indicate that the electrical resistivity in the direction parallel to the stripes is almost 6 orders of magnitude lower than that in the perpendicular direction, which is by far the most striking conductive anisotropy for the plastic anisotropic conductive materials. In addition, it is found that the size of the MWCNT stripe as well as the electrical property of the resulting anisotropic conductive thin film can be well-controlled by the gap of the shear cell.

  14. Magnetic-field- and pressure-induced quantum phases in complex materials.

    Science.gov (United States)

    Kim, Minjung; Barath, Harini; Chen, Xiaoqian; Joe, Young-Il; Fradkin, Eduardo; Abbamonte, Peter; Cooper, S Lance

    2010-03-12

    This Progress Report presents temperature-, magnetic-field-, and pressure-dependent Raman measurements of strongly correlated materials such as the charge-ordering manganese perovskites, the multiferroic material TbMnO(3), and the charge-density wave (CDW) materials 1T-TiSe(2) and Cu(x)TiSe(2). These studies illustrate the rich array of phases and properties that can be accessed with field and pressure tuning in these materials, and demonstrate the efficacy of using magnetic-field- and pressure-dependent scattering methods to elucidate the microscopic changes associated with highly tunable behavior in complex materials.

  15. Three-dimensional supercritical resolved light-induced magnetic holography.

    Science.gov (United States)

    Hao, Chenglong; Nie, Zhongquan; Ye, Huapeng; Li, Hao; Luo, Yang; Feng, Rui; Yu, Xia; Wen, Feng; Zhang, Ying; Yu, Changyuan; Teng, Jinghua; Luk'yanchuk, Boris; Qiu, Cheng-Wei

    2017-10-01

    In the era of big data, there exists a growing gap between data generated and storage capacity using two-dimensional (2D) magnetic storage technologies (for example, hard disk drives), because they have reached their performance saturation. 3D volumetric all-optical magnetic holography is emerging rapidly as a promising road map to realizing high-density capacity for its fast magnetization control and subwavelength magnetization volume. However, most of the reported light-induced magnetization confronts the problems of impurely longitudinal magnetization, diffraction-limited spot, and uncontrollable magnetization reversal. To overcome these challenges, we propose a novel 3D light-induced magnetic holography based on the conceptual supercritical design with multibeam combination in the 4π microscopic system. We theoretically demonstrate a 3D deep super-resolved [Formula: see text] purely longitudinal magnetization spot by focusing six coherent circularly polarized beams with two opposing high numerical aperture objectives, which allows 3D magnetic holography with a volumetric storage density of up to 1872 terabit per cubic inches. The number and locations of the super-resolved magnetization spots are controllable, and thus, desired magnetization arrays in 3D volume can be produced with properly designed phase filters. Moreover, flexible magnetization reversals are also demonstrated in multifocal arrays by using different illuminations with opposite light helicity. In addition to data storage, this magnetic holography may find applications in information security, such as identity verification for a credit card with magnetic stripe.

  16. Detection and characterization of elongated bubbles and drops in two-phase flow using magnetic fields

    Science.gov (United States)

    Wiederhold, A.; Boeck, T.; Resagk, C.

    2017-08-01

    We report a method to detect and to measure the size and velocity of elongated bubbles or drops in a dispersed two-phase flow. The difference of the magnetic susceptibilities between two phases causes a force on the interface between both phases when it is exposed to an external magnetic field. The force is measured with a state-of-the-art electromagnetic compensation balance. While the front and the back of the bubble pass the magnetic field, two peaks in the force signal appear, which can be used to calculate the velocity and geometry parameters of the bubble. We achieve a substantial advantage over other bubble detection techniques because this technique is contactless, non-invasive, independent of the electrical conductivity and can be applied to opaque or aggressive fluids. The measurements are performed in an inclined channel with air bubbles and paraffin oil drops in water. The bubble length is in the range of 0.1-0.25 m and the bubble velocity lies between 0.02-0.22 m s-1. Furthermore we show that it is possible to apply this measurement principle for nondestructive testing (NDT) of diamagnetic and paramagnetic materials like metal, plastics or glass, provided that defects are in the range of 10‒2 m. This technique opens up new possibilities in industrial applications to measure two-phase flow parameters and in material testing.

  17. The Cryogenic Design of the Phase I Upgrade Inner Triplet Magnets for LHC

    CERN Document Server

    van Weelderen, R; Peterson, T

    2011-01-01

    The LHC is operating with beam since end 2009. However, with the present interaction region magnets it cannot reach its nominal performance and a phased approach to upgrading them to reach that nominal performance is taken. The first phase of the LHC interaction region upgrade was approved by Council in December 2007. This phase relies on the mature Nb-Ti superconducting magnet technology with the target of increasing the LHC luminosity to 2 to 3×1034 cm-2s-1, while relying on the existing infrastructure which limits the total heat removal capacity at 1.9 K to 500 W. The Phase I Upgrade LHC interaction region final focus magnets will include four superconducting quadrupoles (low-β triplets) and one superconducting dipole (D1) cooled with pressurized, static superfluid helium (HeII) at 1.9 K. The heat absorbed in pressurized HeII, which may be more than 30 W/m due to dynamic heating from the particle beam halo, will be conducted to saturated He II at about 1.9 K and removed by the low pressure vapour. This p...

  18. Influences of P doping on magnetic phase transition and structure in MnCoSi ribbon

    Science.gov (United States)

    Du, Qian-Heng; Chen, Guo-Fu; Yang, Wen-Yun; Hua, Mu-Xin; Du, Hong-Lin; Wang, Chang-Sheng; Liu, Shun-Quan; Hang, Jing-Zhi; Zhou, Dong; Zhang, Yan; Yan, Jin-Bo

    2015-06-01

    The structure and magnetic properties of MnCoSi1- x Px (x = 0.05-0.50) are systematically investigated. With P content increasing, the lattice parameter a increases monotonically while both b and c decrease. At the same time, the temperature of metamagnetic transition from a low-temperature non-collinear ferromagnetic state to a high-temperature ferromagnetic state decreases and a new magnetic transition from a higher-magnetization ferromagnetic state to a lower-magnetization ferromagnetic state is observed in each of these compounds for the first time. This is explained by the changes of crystal structure and distance between Mn and Si atoms with the increase of temperature according to the high-temperature XRD result. The metamagnetic transition is found to be a second-order magnetic transition accompanied by a low inversed magnetocaloric effect (1.0 J·kg-1·K-1 at 5 T) with a large temperature span (190 K at 5 T) compared with the scenario of MnCoSi. The changes in the order of metamagnetic transition and structure make P-doped MoCoSi compounds good candidates for the study of magnetoelastic coupling and the modulation of magnetic phase transition. Project supported by the National Natural Science Foundation of China (Grant No. 11275013), the Fund from the National Physics Laboratory, China Academy of Engineering Physics (Grant No. 2013DB01), and the National Key Basic Research Program of China (Grant No. 2010CB833104).

  19. Monte Carlo simulation of the surface magnetic phase transition in chromium

    International Nuclear Information System (INIS)

    Mata, G.J.; Valera, M.

    1995-03-01

    Antiferromagnetic chromium is known to have a surface magnetic phase transition at a temperature T s = 780K, which is well above its bulk Neel temperature, T N = 311K. Electronic structure calculations predict an enhancement of the magnetic moment at the surface, due to changes in the local electronic environment. In order to ascertain the role of such an enhancement in the surface magnetic transition, we have modelled the surface by means of a classical Heisenberg model in which: a) the magnitude of a given spin is equal to the value of the corresponding magnetic moment predicted by band structure calculations, b) the exchange interaction J between spins is the same throughout the system, and c) the exchange interaction is chosen so as to reproduce the bulk transition temperature. We find a ratio of surface to bulk transition temperature of T S /T N = 2.5, which is an excellent agreement with the experimental result. Our results suggest that the surface magnetic transition in chromium is driven by fluctuations in the orientation of the magnetic moments and that quantum fluctuations play a minor role. (author). 18 refs, 5 figs

  20. Dynamic phase transitions and dynamic phase diagrams of the spin-2 Blume-Capel model under an oscillating magnetic field within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Ertas, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-03-15

    The dynamic phase transitions are studied in the kinetic spin-2 Blume-Capel model under a time-dependent oscillating magnetic field using the effective-field theory with correlations. The effective-field dynamic equation for the average magnetization is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic magnetization and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are constructed in the reduced temperature and magnetic field amplitude plane and are of seven fundamental types. Phase diagrams contain the paramagnetic (P), ferromagnetic-2 (F{sub 2}) and three coexistence or mixed phase regions, namely the F{sub 2}+P, F{sub 1}+P and F{sub 2}+F{sub 1}+P, which strongly depend on the crystal-field interaction (D) parameter. The system also exhibits the dynamic tricritical behavior. - Highlights: Black-Right-Pointing-Pointer Dynamic phase transitions are studied in spin-2 BC model using EFT. Black-Right-Pointing-Pointer Dynamic phase diagrams are constructed in (T/zJ, h/zJ) plane. Black-Right-Pointing-Pointer Seven fundamental types of dynamic phase diagrams are found in the system. Black-Right-Pointing-Pointer System exhibits dynamic tricritical behavior.

  1. Transverse phase space diagnostics for ionization injection in laser plasma acceleration using permanent magnetic quadrupoles

    Science.gov (United States)

    Li, F.; Nie, Z.; Wu, Y. P.; Guo, B.; Zhang, X. H.; Huang, S.; Zhang, J.; Cheng, Z.; Ma, Y.; Fang, Y.; Zhang, C. J.; Wan, Y.; Xu, X. L.; Hua, J. F.; Pai, C. H.; Lu, W.; Mori, W. B.

    2018-04-01

    We report the transverse phase space diagnostics for electron beams generated through ionization injection in a laser-plasma accelerator. Single-shot measurements of both ultimate emittance and Twiss parameters are achieved by means of permanent magnetic quadrupole. Beams with emittance of μm rad level are obtained in a typical ionization injection scheme, and the dependence on nitrogen concentration and charge density is studied experimentally and confirmed by simulations. A key feature of the transverse phase space, matched beams with Twiss parameter α T ≃ 0, is identified according to the measurement. Numerical simulations that are in qualitative agreement with the experimental results reveal that a sufficient phase mixing induced by an overlong injection length leads to the matched phase space distribution.

  2. Critical current, phase slip centers and phase slip lines in superconducting films in zero external magnetic field

    International Nuclear Information System (INIS)

    Dmitriev, V.M.; Zolochevskii, I.V.; Salenkova, T.V.; Khristenko, E.V.

    2005-01-01

    The temperature dependences of current-voltage characteristics have been measured on high-grade thin Sn films (7-50 micron wide) in zero external magnetic field. For the first time we could observe on the same samples phase slip centers (PSC) near Tc, where the samples were narrow channels, and phase slip lines (PSL) at lower temperatures when the films become wide. In this case the critical current experiences a temperature crossover which affects absolute value of the critical current while the temperature dependence of the (1-T/Tc) 3/2 type persists in a certain temperature interval. On further the temperature lowering, the critical current at which vortices due to the self-field of the current enter the sample has a linear temperature dependence and correlates with the Aslamazov-Lempitsky theory. With lowering temperature the onset of the crossover occurs at a temperature at which the film width becomes equal to the fourfold penetration depth of the weak magnetic field perpendicular to the film plane. On each side of this equality the films are either narrow or wide. The current of the formation of the first PSC is the Ginzburg-Landau critical current of pair breaking which is distributed uniformly over the film width. The current of the formation of the first PSL is the current of the vortex - state instability predicted by Aslamazov and Lempitsky. It is distributed specifically over the sample width

  3. Magnetic performance change of multi-main-phase Nd–Ce–Fe–B magnets by diffusing (Nd, Pr)H x

    Science.gov (United States)

    Ma, Tianyu; Zhang, Wenying; Peng, Baixing; Liu, Yongsheng; Chen, Yongjie; Wang, Xinhua; Yan, Mi

    2018-02-01

    The grain boundary diffusion process (GBDP) is effective to enhance coercivity of the single-main-phase (SMP) RE2Fe14B (rare earth (RE)) magnets through forming magnetic hardening shells surrounding the hard grain cores. Here, the GBDP was applied to the multi-main-phase (MMP) (Nd, Pr)22.3Ce8.24FebalM1.0B1.0 (wt.%) magnets prepared by sintering the mixture of Ce-free and Ce-containing 2:14:1 powders, which have shown superior magnetic properties, especially coercivity, to the SMP ones at the same average composition. The remanence of the (Nd, Pr)H x diffused magnets increases gradually with the increase of diffusion temperature from 480 to 880 °C, the coercivity, however, slightly decreases. The highest (BH)max of 350.1 kJ m‑3 is achieved when diffusing at 680 °C, which is 9.2% higher than 320.7 kJ m‑3 for the as-prepared magnet. The remanence increment is due to the diffusion of Nd/Pr into the 2:14:1 phase grains, enlarging the intrinsic saturation magnetic polarization. The slight coercivity reduction is due to the gradual homogenization of RE distribution within the 2:14:1 grains of the undiffused parts, i.e. approaching the ‘close to equilibrium (or SMP)’ state, which offsets the positive contributions from the enrichment of Nd/Pr in the Ce-rich 2:14:1 phase and the formation of continuous RE-rich intergranular phase. These findings suggest that the GBDP effect on coercivity of the MMP Nd–Ce–Fe–B magnets is distinctly different from the SMP ones, and that the chemical heterogeneity should be carefully controlled to improve the magnetic properties of such high cost-performance permanent magnets.

  4. Stripes developed at the strong limit of nematicity in FeSe film

    Science.gov (United States)

    Li, Wei; Zhang, Yan; Deng, Peng; Xu, Zhilin; Mo, S.-K.; Yi, Ming; Ding, Hao; Hashimoto, M.; Moore, R. G.; Lu, D.-H.; Chen, Xi; Shen, Z.-X.; Xue, Qi-Kun

    2017-10-01

    A single monolayer of iron selenide grown on strontium titanate shows an impressive enhancement of superconductivity compared with the bulk, as well as a novel Fermi surface topology, extreme two-dimensionality, and the possibility of phonon-enhanced electron pairing. For films thicker than one unit cell, however, the electronic structure is markedly different, with a drastically suppressed superconductivity and strong nematicity appearing. The physics driving this extraordinary dichotomy of superconducting behaviour is far from clear. Here, we use low-temperature scanning tunnelling microscopy to study multilayers of iron selenide grown by molecular beam epitaxy, and find a stripe-type charge ordering instability that develops beneath the nematic state. The charge ordering is visible and pinned in the vicinity of impurities. And as it emerges in the strong limit of nematicity, it suggests that a magnetic fluctuation with a rather small wavevector may be competing with the ordinary collinear antiferromagnetic ordering in multilayer films. The existence of stripes in iron-based superconductors, which resemble the stripe order in cuprates, not only suggests that electronic anisotropy and correlation are playing an important role, but also provides a platform for probing the complex interactions between nematicity, charge ordering, magnetism and superconductivity in high-temperature superconductors.

  5. Ultrasonic studies of the magnetic phase transition in MnSi.

    Science.gov (United States)

    Petrova, A E; Stishov, S M

    2009-05-13

    Measurements of the sound velocities in a single crystal of MnSi were performed in the temperature range 4-150 K. Elastic constants, controlling propagation of longitudinal waves, reveal significant softening at a temperature of about 29.6 K and small discontinuities at ∼28.8 K, which corresponds to the magnetic phase transition in MnSi. In contrast, the shear elastic moduli do not show any softening at all, reacting only to the small volume deformation caused by the magneto-volume effect. The current ultrasonic study exposes an important fact that the magnetic phase transition in MnSi, occurring at 28.8 K, is just a minor feature of the global transformation marked by the rounded maxima or minima of heat capacity, thermal expansion coefficient, sound velocities and absorption, and the temperature derivative of resistivity.

  6. Ultrasonic studies of the magnetic phase transition in MnSi

    International Nuclear Information System (INIS)

    Petrova, A E; Stishov, S M

    2009-01-01

    Measurements of the sound velocities in a single crystal of MnSi were performed in the temperature range 4-150 K. Elastic constants, controlling propagation of longitudinal waves, reveal significant softening at a temperature of about 29.6 K and small discontinuities at ∼28.8 K, which corresponds to the magnetic phase transition in MnSi. In contrast, the shear elastic moduli do not show any softening at all, reacting only to the small volume deformation caused by the magneto-volume effect. The current ultrasonic study exposes an important fact that the magnetic phase transition in MnSi, occurring at 28.8 K, is just a minor feature of the global transformation marked by the rounded maxima or minima of heat capacity, thermal expansion coefficient, sound velocities and absorption, and the temperature derivative of resistivity.

  7. Magnetic phase diagram of Sr1-xCaxCo2P2

    Science.gov (United States)

    Sugiyama, J.; Nozaki, H.; Umegaki, I.; Harada, M.; Higuchi, Y.; Ansaldo, E. J.; Brewer, J. H.; Imai, M.; Michioka, C.; Yoshimura, K.; Månsson, M.

    2014-12-01

    In order to study the phase diagram from a microscopic viewpoint, we have measured wTF- and ZF-μ+SR spectra for the Sr1-xCaxCo2P2 powder samples with x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1. Due to a characteristic time window and spatial resolution of μ+SR, the obtained phase diagram was found to be rather different from that determined by magnetization measurements. That is, as x increases from 0, a Pauli-paramagnetic phase is observed even at the lowest T measured (1.8 K) until x = 0.4, then, a spin-glass like phase appears at 0.5 detected for x = 0.8, and finally, a commensurate A-type AF ordered phase (for x = 1) is stabilized below TN ~ 80 K. Such change is most likely reasonable and connected to the shrink of the c-axis length with x, which naturally enhances the magnetic interaction between the two adjacent Co planes.

  8. Magnetic phase transitions in ferrite nanoparticles characterized by electron spin resonance

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Arias, Yesica, E-mail: yeika01@hotmail.com; Vázquez-Victorio, Gabriela; Ortega-Zempoalteca, Raul; Acevedo-Salas, Ulises; Valenzuela, Raul [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Ammar, Souad [Laboratoires ITODYS, Université de Paris-Diderot, PRES Sorbonne Paris Cité, CNRS-UMR 7086, 75205 Paris Cedex (France)

    2015-05-07

    Ferrite magnetic nanoparticles in the composition Zn{sub 0.7}Ni{sub 0.3}Fe{sub 2}O{sub 4} were synthesized by the polyol method, with an average size of 8 nm. Electron spin resonance (ESR) measurements were carried out at a frequency of 9.45 GHz in the 100–500 K temperature range. Obtained results exhibited a characteristic ESR signal in terms of resonance field, H{sub res}, linewidth, ΔH, and peak ratio, R, for each magnetic phase. At low temperatures, the ferrimagnetic phase showed low H{sub res}, broad ΔH, and asymmetric R. At high temperatures, these parameters exhibited opposite values: high H{sub res}, small ΔH, and R ∼ 1. For intermediate temperatures, a different phase was observed, which was identified as a superparamagnetic phase by means of zero-field cooling-field cooling and hysteresis loops measurements. The observed differences were explained in terms of the internal fields and especially due to the cubic anisotropy in the ordered phase.

  9. Magnetic Hamiltonian and phase diagram of the quantum spin liquid Ca10Cr7O28

    Science.gov (United States)

    Balz, Christian; Lake, Bella; Nazmul Islam, A. T. M.; Singh, Yogesh; Rodriguez-Rivera, Jose A.; Guidi, Tatiana; Wheeler, Elisa M.; Simeoni, Giovanna G.; Ryll, Hanjo

    2017-05-01

    A spin liquid is a new state of matter with topological order where the spin moments continue to fluctuate coherently down to the lowest temperatures rather than develop static long-range magnetic order as found in conventional magnets. For spin liquid behavior to arise in a material the magnetic Hamiltonian must be "frustrated", where the combination of lattice geometry, interactions, and anisotropies gives rise to competing spin arrangements in the ground state. Theoretical Hamiltonians which produce spin liquids are spin ice, the Kitaev honeycomb model, and the kagome antiferromagnet. Spin liquid behavior, however, in real materials is rare because they can only approximate these Hamiltonians and often have weak higher-order terms that destroy the spin liquid state. Ca10Cr7O28 is a new quantum spin liquid candidate with magnetic Cr5 + ions that possess quantum spin number S =½ . The spins are entirely dynamic in the ground state and the excitation spectrum is broad and diffuse, as is typical of spinons which are the excitations of a spin liquid. In this paper we determine the Hamiltonian of Ca10Cr7O28 using inelastic neutron scattering under high magnetic field to induce a field-polarized paramagnetic ground state and spin-wave excitations that can be fitted to extract the interactions. We further explore the phase diagram by using inelastic neutron scattering and heat capacity measurements and establish the boundaries of the spin liquid phase as a function of magnetic field and temperature. Our results show that Ca10Cr7O28 consists of distorted kagome bilayers with several isotropic ferromagnetic and antiferromagnetic interactions where, unexpectedly, the ferromagnetic interactions are stronger than the antiferromagnetic ones. This complex Hamiltonian does not correspond to any known spin liquid model and points to new directions in the search for quantum spin liquid behavior.

  10. Phase stability and ordering in diluted magnetic III-V semiconductors

    Czech Academy of Sciences Publication Activity Database

    Drchal, Václav; Kudrnovský, Josef; Turek, Ilja; Máca, František; Weinberger, P.

    2004-01-01

    Roč. 84, č. 18 (2004), s. 1889-1905 ISSN 1478-6435 R&D Projects: GA AV ČR IAA1010203; GA MŠk OC P5.30 Institutional research plan: CEZ:AV0Z1010914 Keywords : diluted ferromagnetic semiconductors * phase stability * Ga-Mn-As alloy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.167, year: 2004

  11. Effect of Magnetic Hysteresis of the Solid Phase on the Rheological Properties of Mr Fluids

    Science.gov (United States)

    de Vicente, J.; Durán, J. D. G.; Delgado, A. V.; González-Caballero, F.; Bossis, G.

    An experimental investigation is described concerning the effect of the existence of a remanent magnetization of the dispersed particles on the rheological properties of magnetorheological fluids (MRF). Two MRF's were used: (1) solid phase: cobalt ferrite particles + silica gel (1.5% w/w) liquid phase: silicone oil (viscosity 20 mPa.s) and (2) solid phase: carbonyl iron + silica gel; liquid phase; silicone oil. The cobalt ferrite particles were synthetized as monodisperse colloidal spheres with an average diameter of 850 nm. The dependence of the dimensionless shear stress (τ*/φ) vs. Mason number (Mn) fails to scale when a ``magnetorheological hysteresis procedure'' is followed, specially for the higher volume fractions used (~ 7.5%). The yield stress (τy) is first estimated from successive rheograms obtained decreasing the external field (H0) values for different φ. A more precise determination can be done by applying a stress ramp in the oscillatory regime. The critical stress amplitude (τc) needed to exceed the viscoelastic linear region (VLR) is obtained. It is found that both τy and τc strongly depend on the magnetic history of the sample. As expected, the previous results were not obtained in a classical MRF of carbonyl iron particles since they do not present magnetic hysteresis. We conclude that cobalt ferrite suspensions are an other kind of MRF which works at low fields (0 - 17.8 kA/m) with the opposite effect: decrease of the yield stress with the field. This property can be improved using particles with stronger remanent magnetization.

  12. A method to implement the reservoir-wave hypothesis using phase-contrast magnetic resonance imaging

    OpenAIRE

    Gray, Robert D.M.; Parker, Kim H.; Quail, Michael A.; Taylor, Andrew M.; Biglino, Giovanni

    2016-01-01

    The reservoir-wave hypothesis states that the blood pressure waveform can be usefully divided into a “reservoir pressure” related to the global compliance and resistance of the arterial system, and an “excess pressure” that depends on local conditions. The formulation of the reservoir-wave hypothesis applied to the area waveform is shown, and the analysis is applied to area and velocity data from high-resolution phase-contrast cardiovascular magnetic resonance (CMR) imaging. A validation stud...

  13. Geometry optimization of five-phase permanent magnet synchronous motors using Bees algorithm

    Directory of Open Access Journals (Sweden)

    R Ilka

    2015-12-01

    Full Text Available Among all types of electrical motors, permanent magnet synchronous motors (PMSMs are reliable and efficient motors in industrial applications. Because of their superiority over other kinds of motors, they are replacing conventional electric motors. On the other hand, high-phase PMSMs are good candidates to be used in certain industrial and military projects such as electric vehicles, spacecrafts, naval systems and etc. In these cases, the motor has to be designed with minimum volume and high torque and efficiency. Design optimization can improve their features noticeably, thus reduce volume and enhance performance of motors. In this paper, a new method for optimum design of a five-phase surface-mounted permanent magnet synchronous motor is presented to achieve minimum permanent magnets (PMs volume with an increased torque and efficiency. Design optimization is performed in search for optimum dimensions of the motor and its permanent magnets using Bees Algorithm (BA. The design optimization results in a motor with great improvement regarding the original motor which is compared with two well-known evolutionary algorithms i.e. GA and PSO. Finally, finite element method simulation is utilized to validate the accuracy of the design.

  14. Structural and magnetic states in layered manganites: An expanding view of the phase diagram

    International Nuclear Information System (INIS)

    Mitchell, J. F.; Millburn, J. E.; Ling, C.; Argyriou, D. N.; Bordallo, H. N.

    2000-01-01

    Colossal magnetoresistive (CMR) manganites display a spectacular range of structural, magnetic, and electronic phases as a function of hole concentration, temperature, magnetic field, etc. A1though the bulk of research has concentrated on the 3-D perovskite manganites, the ability to study anisotropic magnetic and electronic interactions made available in reduced dimensions has accelerated interest in the layered Ruddlesden-Popper (R-P) phases of the manganite class. The quest for understanding the coupling among lattice, spin, and electronic degrees of freedom (and dimensionality) is driven by the availability of high quality materials. In this talk, the authors will present recent results on synthesis and magnetic properties of layered manganites from the La 2-2x Sr 1+2x Mn 2 O 7 series in the Mn 4+ -rich regime x >0.5. This region of the composition diagram is populated by antiferromagnetic structures that evolve from the A-type layered order to G-type ''rocksalt'' order as x increases. Between these two regimes is a wide region (0.7 3+ /Mn 4+ sites

  15. Demonstration of Focusing Wolter Mirrors for Neutron Phase and Magnetic Imaging

    Directory of Open Access Journals (Sweden)

    Daniel S. Hussey

    2018-03-01

    Full Text Available Image-forming focusing mirrors were employed to demonstrate their applicability to two different modalities of neutron imaging, phase imaging with a far-field interferometer, and magnetic-field imaging through the manipulation of the neutron beam polarization. For the magnetic imaging, the rotation of the neutron polarization in the magnetic field was measured by placing a solenoid at the focus of the mirrors. The beam was polarized upstream of the solenoid, while the spin analyzer was situated between the solenoid and the mirrors. Such a polarized neutron microscope provides a path toward considerably improved spatial resolution in neutron imaging of magnetic materials. For the phase imaging, we show that the focusing mirrors preserve the beam coherence and the path-length differences that give rise to the far-field moiré pattern. We demonstrated that the visibility of the moiré pattern is modified by small angle scattering from a highly porous foam. This experiment demonstrates the feasibility of using Wolter optics to significantly improve the spatial resolution of the far-field interferometer.

  16. Isolation of genomic DNA using magnetic nanoparticles as a solid-phase support

    Energy Technology Data Exchange (ETDEWEB)

    Saiyed, Z M; Ramchand, C N [Kemin Nutritional Technologies (India) Pvt Ltd, Trapezium, Nelson Manickam Road, Chennai 600 029 (India); Telang, S D [Department of Biochemistry, Faculty of Science, M S University of Baroda, Sayajigunj, Vadodara 390 002 (India)], E-mail: cnramchand@yahoo.com, E-mail: ramchand.cn@kemin.com

    2008-05-21

    In recent years, techniques employing magnetizable solid-phase supports (MSPS) have found application in numerous biological fields. This magnetic separation procedure offers several advantages in terms of subjecting the analyte to very little mechanical stress compared to other methods. Secondly, these methods are non-laborious, cheap, and often highly scalable. The current paper details a genomic DNA isolation method optimized in our laboratory using magnetic nanoparticles as a solid-phase support. The quality and yields of the isolated DNA from all the samples using magnetic nanoparticles were higher or equivalent to the traditional DNA extraction procedures. Additionally, the magnetic method takes less than 15 min to extract polymerase chain reaction (PCR) ready genomic DNA as against several hours taken by traditional phenol-chloroform extraction protocols. Moreover, the isolated DNA was found to be compatible in PCR amplification and restriction endonuclease digestion. The developed procedure is quick, inexpensive, robust, and it does not require the use of organic solvents or sophisticated instruments, which makes it more amenable to automation and miniaturization.

  17. Isolation of genomic DNA using magnetic nanoparticles as a solid-phase support

    Science.gov (United States)

    Saiyed, Z. M.; Ramchand, C. N.; Telang, S. D.

    2008-05-01

    In recent years, techniques employing magnetizable solid-phase supports (MSPS) have found application in numerous biological fields. This magnetic separation procedure offers several advantages in terms of subjecting the analyte to very little mechanical stress compared to other methods. Secondly, these methods are non-laborious, cheap, and often highly scalable. The current paper details a genomic DNA isolation method optimized in our laboratory using magnetic nanoparticles as a solid-phase support. The quality and yields of the isolated DNA from all the samples using magnetic nanoparticles were higher or equivalent to the traditional DNA extraction procedures. Additionally, the magnetic method takes less than 15 min to extract polymerase chain reaction (PCR) ready genomic DNA as against several hours taken by traditional phenol-chloroform extraction protocols. Moreover, the isolated DNA was found to be compatible in PCR amplification and restriction endonuclease digestion. The developed procedure is quick, inexpensive, robust, and it does not require the use of organic solvents or sophisticated instruments, which makes it more amenable to automation and miniaturization.

  18. Magnetic shielding of 3-phase current by a composite material at low frequencies

    Directory of Open Access Journals (Sweden)

    K. L. Livesey

    2017-05-01

    Full Text Available Electromagnetic shielding at microwave frequencies (MHz and GHz can be accomplished by attenuating the waves using ferromagnetic resonance and eddy currents in conductive materials. This method is not as effective at shielding the quasi-static magnetic fields produced by low-frequency (kHz currents. We explore theoretically the use of composite materials – magnetic nanoparticles embedded in a polymer matrix – as a shielding material surrounding a 3-phase current source. We develop several methods to estimate the permeability of a single magnetic nanoparticle at low frequencies, several hundred kHz, and find that the relative permeability can be as high as 5,000-20,000. We then use two analytic effective medium theories to find the effective permeability of a collection of nanoparticles as a function of the volume filling fraction. The analytic calculations provide upper and lower bounds on the composite permeability, and we use a numerical solution to calculate the effective permeability for specific cases. The field-pattern for the 3-phase current is calculated using a magnetic scalar potential for each of the three wires surrounded by a cylinder with the effective permeability found above. For a cylinder with an inner radius of 1 cm and an outer radius of 1.5 cm and an effective permeability of 50, one finds a reduction factor of about 8 in the field strength outside the cylinder.

  19. Polarized neutron reflectivity and scattering studies of magnetic heterostructures

    Science.gov (United States)

    Zabel, H.; Theis-Bröhl, K.

    2003-02-01

    The current interest in the magnetism of ultrathin films and multilayers is driven by their manifold applications in the magneto-and spin-electronic areas, for instance as magnetic field sensors or as information storage devices. In this regard, there is a large interest in exploring spin structures and spin disorder at the interface of magnetic heterostructures, to investigate magnetic domains in thin films and superlattices, and to understand remagnetization processes of various laterally shaped magnetic nanostructures. Traditionally neutron scattering has played a dominant role in the determination of spin structures, phase transitions and magnetic excitations in bulk materials. Today, its potential for the investigation of thin magnetic films has to be redefined. Polarized neutron reflectivity (PNR) at small wavevectors can provide precise information on the magnetic field distribution parallel to the film plane and on layer resolved magnetization vectors. In addition, PNR is not only sensitive to structural interface roughness but also to the magnetic roughness. Furthermore, magnetic hysteresis measurements from polarized small angle Bragg reflections allows us to filter out correlation effects during magnetization reversals of magnetic stripes and islands. An overview is provided on most recent PNR investigations of magnetic heterostructures.

  20. Polarized neutron reflectivity and scattering studies of magnetic heterostructures

    International Nuclear Information System (INIS)

    Zabel, H; Theis-Broehl, K

    2003-01-01

    The current interest in the magnetism of ultrathin films and multilayers is driven by their manifold applications in the magneto-and spin-electronic areas, for instance as magnetic field sensors or as information storage devices. In this regard, there is a large interest in exploring spin structures and spin disorder at the interface of magnetic heterostructures, to investigate magnetic domains in thin films and superlattices, and to understand remagnetization processes of various laterally shaped magnetic nanostructures. Traditionally neutron scattering has played a dominant role in the determination of spin structures, phase transitions and magnetic excitations in bulk materials. Today, its potential for the investigation of thin magnetic films has to be redefined. Polarized neutron reflectivity (PNR) at small wavevectors can provide precise information on the magnetic field distribution parallel to the film plane and on layer resolved magnetization vectors. In addition, PNR is not only sensitive to structural interface roughness but also to the magnetic roughness. Furthermore, magnetic hysteresis measurements from polarized small angle Bragg reflections allows us to filter out correlation effects during magnetization reversals of magnetic stripes and islands. An overview is provided on most recent PNR investigations of magnetic heterostructures

  1. Microstructure and magnetic behavior of Mn doped GeTe chalcogenide semiconductors based phase change materials

    Science.gov (United States)

    Adam, Adam Abdalla Elbashir; Cheng, Xiaomin; Abuelhassan, Hassan H.; Miao, Xiang Shui

    2017-06-01

    Phase-change materials (PCMs) are the most promising candidates to be used as an active media in the universal data storage and spintronic devices, due to their large differences in physical properties of the amorphous-crystalline phase transition behavior. In the present study, the microstructure, magnetic and electrical behaviors of Ge0.94Mn0.06Te thin film were investigated. The crystallographic structure of Ge0.94Mn0.06Te thin film was studied sing X-ray diffractometer (XRD) and High Resolution Transmission Electron Microscope (HR-TEM). The XRD pattern showed that the crystallization structure of the film was rhombohedral phase for GeTe with a preference (202) orientation. The HR-TEM image of the crystalline Ge0.94Mn0.06Te thin film demonstrated that, there were two large crystallites and small amorphous areas. The magnetization as a function of the magnetic field analyses of both amorphous and crystalline states showed the ferromagnetic hysteretic behaviors. Then, the hole carriers concentration of the film was measured and it found to be greater than 1021 cm-3 at room temperature. Moreover, the anomalous of Hall Effect (AHE) was clearly observed for the measuring temperatures 5, 10 and 50 K. The results demonstrated that the magnitude of AHE decreased when the temperature was increasing.

  2. Modeling and Analysis of Magnetic Nanoparticles Injection in Water-Oil Two-Phase Flow in Porous Media under Magnetic Field Effect

    Directory of Open Access Journals (Sweden)

    Mohamed F. El-Amin

    2017-01-01

    Full Text Available In this paper, the magnetic nanoparticles are injected into a water-oil, two-phase system under the influence of an external permanent magnetic field. We lay down the mathematical model and provide a set of numerical exercises of hypothetical cases to show how an external magnetic field can influence the transport of nanoparticles in the proposed two-phase system in porous media. We treat the water-nanoparticles suspension as a miscible mixture, whereas it is immiscible with the oil phase. The magnetization properties, the density, and the viscosity of the ferrofluids are obtained based on mixture theory relationships. In the mathematical model, the phase pressure contains additional term to account for the extra pressures due to fluid magnetization effect and the magnetostrictive effect. As a proof of concept, the proposed model is applied on a countercurrent imbibition flow system in which both the displacing and the displaced fluids move in opposite directions. Physical variables, including water-nanoparticles suspension saturation, nanoparticles concentration, and pore wall/throat concentrations of deposited nanoparticles, are investigated under the influence of the magnetic field. Two different locations of the magnet are studied numerically, and variations in permeability and porosity are considered.

  3. Modeling and Analysis of Magnetic Nanoparticles Injection in Water-Oil Two-Phase Flow in Porous Media under Magnetic Field Effect

    KAUST Repository

    El-Amin, Mohamed

    2017-08-28

    In this paper, the magnetic nanoparticles are injected into a water-oil, two-phase system under the influence of an external permanent magnetic field. We lay down the mathematical model and provide a set of numerical exercises of hypothetical cases to show how an external magnetic field can influence the transport of nanoparticles in the proposed two-phase system in porous media. We treat the water-nanoparticles suspension as a miscible mixture, whereas it is immiscible with the oil phase. The magnetization properties, the density, and the viscosity of the ferrofluids are obtained based on mixture theory relationships. In the mathematical model, the phase pressure contains additional term to account for the extra pressures due to fluid magnetization effect and the magnetostrictive effect. As a proof of concept, the proposed model is applied on a countercurrent imbibition flow system in which both the displacing and the displaced fluids move in opposite directions. Physical variables, including waternanoparticles suspension saturation, nanoparticles concentration, and pore wall/throat concentrations of deposited nanoparticles, are investigated under the influence of the magnetic field. Two different locations of the magnet are studied numerically, and variations in permeability and porosity are considered.

  4. Magnetic phase investigations on fluorine (F) doped LiFePO4

    Science.gov (United States)

    Radhamani, A. V.

    2018-03-01

    LiFePO4 (LFP) is a very promising cathode material for Li-ion batteries due to its high thermal stability, less toxicity and high theoretical capacity (170 mAh g-1). Anion doping, especially fluorine (F) at the oxygen site is one way to improve the low electronic conductivity of the material. In this line, fluorine doped LFP was prepared at different fluorine concentrations (1 to 40 mol%) to study the structural, spectroscopic and magnetic properties in view of the material property optimization for battery applications. The investigation of the magnetic properties was found to be successful for the determination of small amounts of magnetic impurities which were not noticeably observed from structural characterizations. Determination of conducting magnetic impurities has its own relevance in the current scenario of Li-ion based battery applications. Systematic characterization studies along with the implications of magnetic phases on the material activity of fluorine doped LiFePO4 nanoparticles will be discussed in detail.

  5. Self-Generated Magnetic Fields in Stagnation-Phase ICF Implosions

    Science.gov (United States)

    Walsh, Christopher; Chittenden, Jeremy; McGlinchey, Kristopher; Niasse, Nicolas

    2016-10-01

    3-D extended-MHD simulations of the stagnation phase of an ICF implosion are presented, showing significant self-generated magnetic fields (1000-5000T) due to the Biermann Battery effect. Perturbed hot-spots generate magnetic fields at their edges, as the extremities of hot bubbles are rapidly cooled by the surrounding low temperature fuel, giving non-parallel electron pressure and density gradients. Larger amplitude and higher mode-number perturbations lead to an increased hot-spot surface area and more heat flow, developing greater non-parallel gradients and therefore larger magnetic fields. Due to this, largely perturbed hot-spots can be affected more by magnetic fields, although the accelerated cooling associated with greater deviations from symmetry lowers magnetisation. The Nernst effect advects magnetic field down temperature gradients towards the outer region of the hot-spot, which can also lower the magnetisation of the plasma. In some regions, however, the Nernst velocity is convergent, magnetising the tips of cold fuel spikes, resulting in anisotropic heat-flow and an improvement in energy containment. Low-mode and multi-high-mode simulations are shown, with magnetisations reaching sufficiently high levels in some regions of the hot-spot to suppress thermal conduction to lower than 50% of the unmagnetised case. A quantitative analysis of how this affects the hot-spot energy balance is included.

  6. Recent developments in Liquid Phase Electroepitaxial growth of bulk crystals under magnetic field

    Science.gov (United States)

    Dost, Sadik; Lent, Brian; Sheibani, Hamdi; Liu, Yongcai

    2004-05-01

    This review article presents recent developments in Liquid Phase Electroepitaxial (LPEE) growth of bulk single crystals of alloy semiconductors under an applied static magnetic field. The growth rate in LPEE is proportional to the applied electric current. However, at higher electric current levels the growth becomes unstable due to the strong convection occurring in the liquid zone. In order to address this problem, a significant body of research has been performed in recent years to suppress and control the natural convection for the purpose of prolonging the growth process to grow larger crystals. LPEE growth experiments show that the growth rate under an applied static magnetic field is also proportional and increases with the field intensity level. The modeling of LPEE growth under magnetic field was also the subject of interest. Two-dimensional mathematical models developed for the LPEE growth process predicted that the natural convection in the liquid zone would be suppressed almost completely with increasing the magnetic field level. However, experiments and also three-dimensional models have shown that there is an optimum magnetic field level below which the growth process is stable and the convection in the liquid zone is suppressed, but above such a field level the convective flow becomes very strong and leads to unstable growth with unstable interfaces. To cite this article: S. Dost et al., C. R. Mecanique 332 (2004).

  7. Sigma phase detection in duplex stainless steel by induced magnetic field

    Science.gov (United States)

    Silva, E. M.; Fialho, W. M. L.; Silva, H. F. B. M.; Leite, J. P.; Leite, J. P.; Oliveira, A. V. G.

    2016-07-01

    Duplex stainless steels when subjected to temperatures above 600 ° C have its tenacity decreased by the formation of sigma phase. This phase has high hardness and is rich in chromium and reduces the matrix of this element. In this study, field line density measurements, obtained in the reversibility region of magnetic domains, and application of artificial neural networks are used to monitor the formation of this undesirable phase. Samples of a stainless steel SAF 2205 were subjected to aging at temperatures of 800 ° C and 900 ° C, in order to obtain different amounts of sigma phase. The amount of this phase was obtained by image processing and the density of field lines through a Hall Effect sensor. Charpy impact tests were performed. The field lines densities were used for training of an artificial neural network and correlated with the presence of sigma phase and embrittlement of the material. The results showed that the method was able to correlate the parameters studied with the presence of the sigma phase and toughness of the material studied in both temperatures.

  8. Formation mechanism of axial macrosegregation of primary phases induced by a static magnetic field during directional solidification

    Science.gov (United States)

    Li, Xi; Fautrelle, Yves; Ren, Zhongming; Moreau, Rene

    2017-04-01

    Understanding the macrosegregation formed by applying magnetic fields is of high commercial importance. This work investigates how static magnetic fields control the solute and primary phase distributions in four directionally solidified alloys (i.e., Al-Cu, Al-Si, Al-Ni and Zn-Cu alloys). Experimental results demonstrate that significant axial macrosegregation of the solute and primary phases (i.e., Al2Cu, Si, Al3Ni and Zn5Cu phases) occurs at the initial solidification stage of the samples. This finding is accompanied by two interface transitions in the mushy zone: quasi planar → sloping → quasi planar. The amplitude of the macrosegregation of the primary phases under the magnetic field is related to the magnetic field intensity, temperature gradient and growth speed. The corresponding numerical simulations present a unidirectional thermoelectric (TE) magnetic convection pattern in the mushy zone as a consequence of the interaction between the magnetic field and TE current. Furthermore, a model is proposed to explain the peculiar macrosegregation phenomenon by considering the effect of the forced TE magnetic convection on the solute distribution. The present study not only offers a new approach to control the solute distribution by applying a static magnetic field but also facilitates the understanding of crystal growth in the solute that is controlled by the static magnetic field during directional solidification.

  9. Unsteady flow of two-phase fluid in circular pipes under applied external magnetic and electrical fields

    Energy Technology Data Exchange (ETDEWEB)

    Gedik, Engin; Recebli, Ziyaddin [Faculty of Technology, Karabuk University, TR-78050, Karabuk (Turkey); Kurt, Hueseyin [Faculty of Engineering, Karabuk University, TR-78050, Karabuk (Turkey); Kecebas, Ali [Faculty of Technology, Afyon Kocatepe University, TR-03200, Afyon (Turkey)

    2012-03-15

    The unsteady viscous incompressible and electrically conducting of two-phase fluid flow in circular pipes with external magnetic and electrical field is considered in this present study. Effects of both uniform transverse external magnetic and electrical fields applied perpendicular to the fluid and each other on the two-phase (solid/liquid) unsteady flow is investigated numerically. While iron powders are being used as the first phase of two-phase fluid, pure water was used as the second phase. The system of the derived governing equations, which are based on the Navier-Stokes equations including Maxwell equations, are solved numerically by using Pdex4 function on the Matlab for both phases. The originality of this study is that, in addition to magnetic field, the effect of electrical field on two-phase unsteady fluids is being examined. The magnetic field which is applied on flow decreases the velocity of both phases, whereas the electrical field applied along with magnetic field acted to increase and decrease the velocity values depending on the direction of electrical field. Electrical field alone did not display any impact on two-phase flow. On the other hand, analytical and numerical results are compared and favorable agreements have been obtained. (authors)

  10. Blume-Capel ferromagnet driven by propagating and standing magnetic field wave: Dynamical modes and nonequilibrium phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Acharyya, Muktish, E-mail: muktish.physics@presiuniv.ac.in; Halder, Ajay, E-mail: ajay.rs@presiuniv.ac.in

    2017-03-15

    The dynamical responses of Blume-Capel (S=1) ferromagnet to the plane propagating (with fixed frequency and wavelength) and standing magnetic field waves are studied separately in two dimensions by extensive Monte Carlo simulation. Depending on the values of temperature, amplitude of the propagating magnetic field and the strength of anisotropy, two different dynamical phases are observed. For a fixed value of anisotropy and the amplitude of the propagating magnetic field, the system undergoes a dynamical phase transition from a driven spin wave propagating phase to a pinned or spin frozen state as the system is cooled down. The time averaged magnetisation over a full cycle of the propagating magnetic field plays the role of the dynamic order parameter. A comprehensive phase diagram is plotted in the plane formed by the amplitude of the propagating wave and the temperature of the system. It is found that the phase boundary shrinks inward as the anisotropy increases. The phase boundary, in the plane described by the strength of the anisotropy and temperature, is also drawn. This phase boundary was observed to shrink inward as the field amplitude increases. - Highlights: • The Blume-Capel ferromagnet in propagating and standing magnetic wave. • Monte Carlo single spin flip Metropolis algorithm is employed. • The dynamical modes are observed. • The nonequilibrium phase transitions are studied. • The phase boundaries are drawn.

  11. Geometric-Phase Interference in a Mn12 Single-Molecule Magnet with Truly Fourfold Symmetry

    Science.gov (United States)

    Friedman, Jonathan

    2014-03-01

    A single-molecule magnet (SMM) is a large-spin system with an anisotropy barrier separating preferred ``up'' and ``down'' orientations. The spin can tunnel between these directions when an external longitudinal magnetic field brings levels in opposite wells into resonance. When there exist more than one energetically equivalent paths for tunneling, those paths can interfere, a geometric-phase effect that modulates the rate at which spins flip direction. The interference can be controlled by a magnetic field applied perpendicular to the spin's easy magnetization axis. In a ground-breaking experiment, Wernsdorfer and Sessoli found oscillations in the probability of spin tunneling as a function of the field applied along the hard axis of the Fe8 SMM. This observation confirmed a theoretical prediction by Garg. Similar geometric-phase interference has been observed in other SMMs that have effective two-fold symmetry, where tunneling involves the interference between two equal-amplitude paths. Such interference effects have not previously been seen in systems with four-fold rotational symmetry. In recent work, my group has seen evidence of the observation of a geometric-phase interference effect in the Mn12-tBuAc SMM, a variant of the bellwether Mn12-Ac SMM that has true four-fold rotational symmetry (being free of the solvent disorder that breaks the four-fold symmetry in the latter). The spin relaxation rate as a function of the applied transverse magnetic field shows a modulated behavior, with retarded relaxation near where one expects destructive interference between tunneling paths associated with excited states. Tuning the direction of the transverse field away from the hard axis washes out the observed interference effect by favoring one tunneling path over others. Detailed master-equation calculations are used to fit the observed behavior and yield anisotropy parameters consistent with values determined by other groups. Unlike previous observations of geometric-phase

  12. Monte Carlo modeling the phase diagram of magnets with the Dzyaloshinskii - Moriya interaction

    Science.gov (United States)

    Belemuk, A. M.; Stishov, S. M.

    2017-11-01

    We use classical Monte Carlo calculations to model the high-pressure behavior of the phase transition in the helical magnets. We vary values of the exchange interaction constant J and the Dzyaloshinskii-Moriya interaction constant D, which is equivalent to changing spin-spin distances, as occurs in real systems under pressure. The system under study is self-similar at D / J = constant , and its properties are defined by the single variable J / T , where T is temperature. The existence of the first order phase transition critically depends on the ratio D / J . A variation of J strongly affects the phase transition temperature and width of the fluctuation region (the ;hump;) as follows from the system self-similarity. The high-pressure behavior of the spin system depends on the evolution of the interaction constants J and D on compression. Our calculations are relevant to the high pressure phase diagrams of helical magnets MnSi and Cu2OSeO3.

  13. Melatonin metabolite levels in workers exposed to 60-Hz magnetic fields: work in substations and with 3-phase conductors.

    Science.gov (United States)

    Burch, J B; Reif, J S; Noonan, C W; Yost, M G

    2000-02-01

    Melatonin suppression by 50/60-Hz magnetic fields represents a plausible biological mechanism for explaining increased health risks in workers. Personal exposure to magnetic fields and ambient light, and excretion of the melatonin metabolite 6-hydroxymelatonin sulfate (6-OHMS), were measured over 3 consecutive workdays in electric utility workers. There was a magnetic field-dependent reduction in adjusted mean nocturnal and post-work 6-OHMS levels among men working more than 2 hours per day in substation and 3-phase environments and no effect among those working 2 hours or less. No changes were observed among men working in 1-phase environments. The results suggest that circular or elliptical magnetic field polarization, or another factor linked to substations and 3-phase electricity, is associated with magnetic field induced melatonin suppression in humans.

  14. Phase incremented echo train acquisition applied to magnetic resonance pore imaging

    Science.gov (United States)

    Hertel, S. A.; Galvosas, P.

    2017-02-01

    Efficient phase cycling schemes remain a challenge for NMR techniques if the pulse sequences involve a large number of rf-pulses. Especially complex is the Carr Purcell Meiboom Gill (CPMG) pulse sequence where the number of rf-pulses can range from hundreds to several thousands. Our recent implementation of Magnetic Resonance Pore Imaging (MRPI) is based on a CPMG rf-pulse sequence in order to refocus the effect of internal gradients inherent in porous media. While the spin dynamics for spin- 1 / 2 systems in CPMG like experiments are well understood it is still not straight forward to separate the desired pathway from the spectrum of unwanted coherence pathways. In this contribution we apply Phase Incremented Echo Train Acquisition (PIETA) to MRPI. We show how PIETA offers a convenient way to implement a working phase cycling scheme and how it allows one to gain deeper insights into the amplitudes of undesired pathways.

  15. Hysteresis loop signatures of phase transitions in a mean-field model of disordered Ising magnet

    Science.gov (United States)

    Timonin, P. N.

    2010-06-01

    The multiplicity of long-lived states in frustrated disordered magnets makes the task to experimentally deter-mine which of them has the lowest free energy (and thus what thermodynamic phase the sample is in) seem rather hopeless. Nevertheless here we show in the framework of Landau-type phenomenological model that signatures of the mean-field equilibrium phase transitions in such highly nonequilibrium systems may be found in the evolution of the hysteresis loop form. Thus the sequence of transitions from spin-glass to mixed phase and to ferromagnetic one results in the changes from inclined hysteresis loop to that with the developing vertical sides and to one with the perfectly vertical sides. Such relation between loop form and the location of global minimum may hold beyond the mean-field approximation and can be useful in the real experiments and Monte-Carlo simulations of the problems involving rugged potential landscape.

  16. Topological phases of silicene and germanene in an external magnetic field: Quantitative results

    KAUST Repository

    Singh, Nirpendra

    2014-03-17

    We investigate the topological phases of silicene and germanene that arise due to the strong spin-orbit interaction in an external perpendicular magnetic field. Below and above a critical field of 10 T, respectively, we demonstrate for silicene under 3% tensile strain quantum spin Hall and quantum anomalous Hall phases. Not far above the critical field, and therefore in the experimentally accessible regime, we obtain an energy gap in the meV range, which shows that the quantum anomalous Hall phase can be realized experimentally in silicene, in contrast to graphene (tiny energy gap) and germanene (enormous field required). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Field dependence of the magnetic entropy change in typical materials with a second-order phase transition

    International Nuclear Information System (INIS)

    Dong Qiaoyan; Zhang Hongwei; Shen Juelian; Sun Jirong; Shen Baogen

    2007-01-01

    Magnetic field dependence of the magnetic entropy change (ΔS) is the key for magnetic refrigeration. For magnetic materials with a second-order phase transition, the experimental data can be well fitted by the formula of ΔS=-kM s (0)h 2/3 -S(0,0) for a practical field change from 0 to h (the reduced field), where M s (0) is the spontaneous magnetization at 0 K. The constant k is approximately equal to 1.00 T/K, and S(0,0) is interestingly found to be negative. The formula is discussed based on the renormalization group approach to scaling. The attempts have also been made using the formula for NaZn 13 -type La(Fe,Si) 13 compounds with a magnetic first-order phase transition

  18. Magnetic field effect on Gd2(MoO4)3 domain structure formation in the phase transformation range

    International Nuclear Information System (INIS)

    Flerova, S.A.; Tsinman, I.L.

    1987-01-01

    The behaviour of ferroelastic-ferroelectric domain structure of gadolinium molybdate crystal (GMO)during its formation in the magnetic field in the vicinity of phase transformation is studied.It is shown that the formation of domain structure in the presence of a temperature gradient occurs in the field of mechanical stresses whose mainly stretching effect is concentrated near phase boundaries.The magnetic field intensifies summary mechanical stresses where a domain structure in a ferroelectric phase is formed due to interaction with the elements of inhomogeneous and differently oriented currents near phase boundaries

  19. leaf and stripe rust resistance among ethiopian grown wheat ...

    African Journals Online (AJOL)

    ADMIN

    pathogen pathotypes. These varieties and lines, therefore, may be utilized in leaf and stripe rust resistance breeding programs. Key words/phrases: Leaf rust, resistance, stripe rust, Triticum aestivum, Triticum turgidum. * Current address: University of Limpopo, School of Agricultural and Environmental Sciences, Private Bag ...

  20. Transfer of stripe rust resistance from Aegilops variabilis to bread ...

    African Journals Online (AJOL)

    In terms of area, the bread wheat producing regions of China comprise the largest area in the world that is constantly threatened by stripe rust epidemics. Consequently, it is important to exploit new adultplant resistance genes in breeding. This study reports the transfer of stripe rust resistance from Aegilops variabilis to ...

  1. Phase unwinding for dictionary compression with multiple channel transmission in magnetic resonance fingerprinting.

    Science.gov (United States)

    Lattanzi, Riccardo; Zhang, Bei; Knoll, Florian; Assländer, Jakob; Cloos, Martijn A

    2017-12-24

    Magnetic Resonance Fingerprinting reconstructions can become computationally intractable with multiple transmit channels, if the B 1 + phases are included in the dictionary. We describe a general method that allows to omit the transmit phases. We show that this enables straightforward implementation of dictionary compression to further reduce the problem dimensionality. We merged the raw data of each RF source into a single k-space dataset, extracted the transceiver phases from the corresponding reconstructed images and used them to unwind the phase in each time frame. All phase-unwound time frames were combined in a single set before performing SVD-based compression. We conducted synthetic, phantom and in-vivo experiments to demonstrate the feasibility of SVD-based compression in the case of two-channel transmission. Unwinding the phases before SVD-based compression yielded artifact-free parameter maps. For fully sampled acquisitions, parameters were accurate with as few as 6 compressed time frames. SVD-based compression performed well in-vivo with highly under-sampled acquisitions using 16 compressed time frames, which reduced reconstruction time from 750 to 25min. Our method reduces the dimensions of the dictionary atoms and enables to implement any fingerprint compression strategy in the case of multiple transmit channels. Copyright © 2018 Elsevier Inc. All rights reserved.

  2. Application of phase-contrast cine magnetic resonance imaging in endoscopic aqueductoplasty.

    Science.gov (United States)

    Chen, Guoqiang; Zheng, Jiaping; Xiao, Qing; Liu, Yunsheng

    2013-06-01

    The aim of this study was to evaluate the application of phase-contrast cine magnetic resonance imaging (MRI) in endoscopic aqueductoplasty (EA) for patients with obstructive hydrocephalus. The clinical diagnosis of hydrocephalus caused by aqueduct obstruction in 23 patients was confirmed by phase-contrast cine MRI examination. The patients were treated with EA and MRI was repeated during the follow-up. The cerebrospinal fluid (CSF) flow velocity in the aqueduct was measured to determine whether the aqueduct was obstructed. The results of phase-contrast cine MRI examinations indicated that there was no CSF flow in the aqueduct for all patients prior to surgery. Aqueductoplasty was successfully performed in all patients. The results of phase-contrast cine MRI examinations performed a week after surgery demonstrated an average CSF flow velocity of 4.74±1.77 cm/sec. During the follow-up, intracranial hypertension recurred in two patients in whom CSF flow was not observed in the aqueduct by the phase-contrast cine MRI scan. Aqueduct re-occlusion was revealed by an endoscopic exploration. By measuring the CSF flow velocity, phase-contrast cine MRI accurately identifies aqueduct obstruction. Cine MRI is a nontraumatic, simple and reliable method for determining whether the aqueduct is successfully opened following aqueductoplasty.

  3. Phase-Inductance-Based Position Estimation Method for Interior Permanent Magnet Synchronous Motors

    Directory of Open Access Journals (Sweden)

    Xin Qiu

    2017-12-01

    Full Text Available This paper presents a phase-inductance-based position estimation method for interior permanent magnet synchronous motors (IPMSMs. According to the characteristics of phase induction of IPMSMs, the corresponding relationship of the rotor position and the phase inductance is obtained. In order to eliminate the effect of the zero-sequence component of phase inductance and reduce the rotor position estimation error, the phase inductance difference is employed. With the iterative computation of inductance vectors, the position plane is further subdivided, and the rotor position is extracted by comparing the amplitudes of inductance vectors. To decrease the consumption of computer resources and increase the practicability, a simplified implementation is also investigated. In this method, the rotor position information is achieved easily, with several basic math operations and logical comparisons of phase inductances, without any coordinate transformation or trigonometric function calculation. Based on this position estimation method, the field orientated control (FOC strategy is established, and the detailed implementation is also provided. A series of experiment results from a prototype demonstrate the correctness and feasibility of the proposed method.

  4. Mathematical Development and Computational Analysis of Harmonic Phase-Magnetic Resonance Imaging (HARP-MRI) Based on Bloch Nuclear Magnetic Resonance (NMR) Diffusion Model for Myocardial Motion.

    Science.gov (United States)

    Dada, Michael O; Jayeoba, Babatunde; Awojoyogbe, Bamidele O; Uno, Uno E; Awe, Oluseyi E

    2017-09-13

    Harmonic Phase-Magnetic Resonance Imaging (HARP-MRI) is a tagged image analysis method that can measure myocardial motion and strain in near real-time and is considered a potential candidate to make magnetic resonance tagging clinically viable. However, analytical expressions of radially tagged transverse magnetization in polar coordinates (which is required to appropriately describe the shape of the heart) have not been explored because the physics required to directly connect myocardial deformation of tagged Nuclear Magnetic Resonance (NMR) transverse magnetization in polar geometry and the appropriate harmonic phase parameters are not yet available. The analytical solution of Bloch NMR diffusion equation in spherical geometry with appropriate spherical wave tagging function is important for proper analysis and monitoring of heart systolic and diastolic deformation with relevant boundary conditions. In this study, we applied Harmonic Phase MRI method to compute the difference between tagged and untagged NMR transverse magnetization based on the Bloch NMR diffusion equation and obtained radial wave tagging function for analysis of myocardial motion. The analytical solution of the Bloch NMR equations and the computational simulation of myocardial motion as developed in this study are intended to significantly improve healthcare for accurate diagnosis, prognosis and treatment of cardiovascular related deceases at the lowest cost because MRI scan is still one of the most expensive anywhere. The analysis is fundamental and significant because all Magnetic Resonance Imaging techniques are based on the Bloch NMR flow equations.

  5. Reversible and irreversible magnetization of the Chevrel-phase superconductor PbMo6S8

    International Nuclear Information System (INIS)

    Zheng, D.N.; Ramsbottom, H.D.; Hampshire, D.P.

    1995-01-01

    Magnetic measurements have been carried out on the hot-isostatically-pressed Chevrel-phase superconductor PbMo 6 S 8 at temperatures from 4.2 K to T c and for magnetic fields up to 12 T. The results show that for the PbMo 6 S 8 compound there is a wide magnetically reversible region, between the irreversibility field B irr and the upper critical field B c2 , on the isothermal magnetic hysteresis curves. The B irr (T) line, i.e., the irreversibility line, was found to obey a power-law expression: B irr =B * (1-T/T c ) α with α∼1.5. Magnetic relaxation measurements revealed that the flux-creep effect in the material studied is substantial and is greater than those observed in conventional metallic alloys, but smaller than in high-temperature superconductors. The existence of the irreversibility line and pronounced flux-creep effect in PbMo 6 S 8 is attributed to the short coherence length of the material. From the reversible magnetization data, the values of the penetration depth, the coherence length, and the critical fields are obtained together with the Ginzburg-Landau parameter κ. At 4.2 K, the critical current density J c is 10 9 A m -2 at zero field, and decreases to 2x10 8 A m -2 at 10 T. Pinning force curves measured at different temperatures obey a Kramer-scaling law of the form: F p (=J c xB)∝b 1/2 (1-b) 2 , which indicates that the J c is limited by one predominant flux-pinning mechanism

  6. Magnetic ordering in electronically phase-separated La2-xSrxCuO4+y: Neutron diffraction experiments

    DEFF Research Database (Denmark)

    Udby, Linda; Andersen, Niels Hessel; Chou, F.C.

    2009-01-01

    We present results of magnetic neutron diffraction experiments on the codoped superoxygenated La2-xSrxCuO4+y (LSCO+O) system with x=0.09. We find that the magnetic phase is long-range ordered incommensurate antiferromagnetic with a Neacuteel temperature T-N coinciding with the superconducting...

  7. Flow regime classification in air-magnetic fluid two-phase flow.

    Science.gov (United States)

    Kuwahara, T; De Vuyst, F; Yamaguchi, H

    2008-05-21

    A new experimental/numerical technique of classification of flow regimes (flow patterns) in air-magnetic fluid two-phase flow is proposed in the present paper. The proposed technique utilizes the electromagnetic induction to obtain time-series signals of the electromotive force, allowing us to make a non-contact measurement. Firstly, an experiment is carried out to obtain the time-series signals in a vertical upward air-magnetic fluid two-phase flow. The signals obtained are first treated using two kinds of wavelet transforms. The data sets treated are then used as input vectors for an artificial neural network (ANN) with supervised training. In the present study, flow regimes are classified into bubbly, slug, churn and annular flows, which are generally the main flow regimes. To validate the flow regimes, a visualization experiment is also performed with a glycerin solution that has roughly the same physical properties, i.e., kinetic viscosity and surface tension, as a magnetic fluid used in the present study. The flow regimes from the visualization are used as targets in an ANN and also used in the estimation of the accuracy of the present method. As a result, ANNs using radial basis functions are shown to be the most appropriate for the present classification of flow regimes, leading to small classification errors.

  8. Substorm activity during the main phase of magnetic storms induced by the CIR and ICME events

    Science.gov (United States)

    Boroyev, R. N.; Vasiliev, M. S.

    2018-01-01

    In this work, the relation of high-latitude indices of geomagnetic activity (AE, Kp) with the rate of storm development and a solar wind electric field during the main phase of magnetic storm induced by the CIR and ICME events is investigated. 72 magnetic storms induced by CIR and ICME events have been selected. It is shown that for the CIR and ICME events the increase of average value of the Kp index (Kpaver) is observed with the growth of rate of storm development. The value of Kpaver index correlates with the magnitude of minimum value of Dst index (|Dstmin|) only for the ICME events. The analysis of average values of AE and Kp indices during the main phase of magnetic storm depending on the SW electric field has shown that for the CIR events, unlike the ICME events, the value of AEaver increases with the growth of average value of the electric field (Eswaver). The value of Kpaver correlates with the Eswaver only for the ICME events. The relation between geomagnetic indices and the maximum value of SW electric field (Eswmax) is weak. However, for the ICME events Kpaver correlates with Eswmax.

  9. Pixelated detectors and improved efficiency for magnetic imaging in STEM differential phase contrast

    International Nuclear Information System (INIS)

    Krajnak, Matus; McGrouther, Damien; Maneuski, Dzmitry; Shea, Val O'; McVitie, Stephen

    2016-01-01

    The application of differential phase contrast imaging to the study of polycrystalline magnetic thin films and nanostructures has been hampered by the strong diffraction contrast resulting from the granular structure of the materials. In this paper we demonstrate how a pixelated detector has been used to detect the bright field disk in aberration corrected scanning transmission electron microscopy (STEM) and subsequent processing of the acquired data allows efficient enhancement of the magnetic contrast in the resulting images. Initial results from a charged coupled device (CCD) camera demonstrate the highly efficient nature of this improvement over previous methods. Further hardware development with the use of a direct radiation detector, the Medipix3, also shows the possibilities where the reduction in collection time is more than an order of magnitude compared to the CCD. We show that this allows subpixel measurement of the beam deflection due to the magnetic induction. While the detection and processing is data intensive we have demonstrated highly efficient DPC imaging whereby pixel by pixel interpretation of the induction variation is realised with great potential for nanomagnetic imaging. - Highlights: • Pixelated STEM DPC vastly improves magnetic imaging for polycrystalline thin films. • Improved efficiency imaging demonstrated on CCD camera. • Direct radiation detector faster with reduced charge spreading. • BF disk edge filtering algorithm superior to thresholding and centre of mass method. • Data intensive process but provides a step change in what is possible with STEM DPC.

  10. OBSERVATIONS OF MAGNETIC FLUX-ROPE OSCILLATION DURING THE PRECURSOR PHASE OF A SOLAR ERUPTION

    International Nuclear Information System (INIS)

    Zhou, G. P.; Wang, J. X.; Zhang, J.

    2016-01-01

    Based on combined observations from the Interface Region Imaging Spectrograph (IRIS) spectrometer with the coronal emission line of Fe xxi at 1354.08 Å and SDO /AIA images in multiple passbands, we report the finding of the precursor activity manifested as the transverse oscillation of a sigmoid, which is likely a pre-existing magnetic flux rope (MFR), that led to the onset of an X class flare and a fast halo coronal mass ejection (CME) on 2014 September 10. The IRIS slit is situated at a fixed position that is almost vertical to the main axis of the sigmoid structure that has a length of about 1.8 × 10 5 km. This precursor oscillation lasts for about 13 minutes in the MFR and has velocities in the range of [−9, 11] km s −1 and a period of ∼280 s. Our analysis, which is based on the temperature, density, length, and magnetic field strength of the observed sigmoid, indicates that the nature of the oscillation is a standing wave of fast magnetoacoustic kink mode. We further find that the precursor oscillation is excited by the energy released through an external magnetic reconnection between the unstable MFR and the ambient magnetic field. It is proposed that this precursor activity leads to the dynamic formation of a current sheet underneath the MFR that subsequently reconnects to trigger the onset of the main phase of the flare and the CME.

  11. Phase mixing of Alfvén waves in axisymmetric non-reflective magnetic plasma configurations

    Science.gov (United States)

    Petrukhin, N. S.; Ruderman, M. S.; Shurgalina, E. G.

    2018-02-01

    We study damping of phase-mixed Alfvén waves propagating in non-reflective axisymmetric magnetic plasma configurations. We derive the general equation describing the attenuation of the Alfvén wave amplitude. Then we applied the general theory to a particular case with the exponentially divergent magnetic field lines. The condition that the configuration is non-reflective determines the variation of the plasma density along the magnetic field lines. The density profiles exponentially decreasing with the height are not among non-reflective density profiles. However, we managed to find non-reflective profiles that fairly well approximate exponentially decreasing density. We calculate the variation of the total wave energy flux with the height for various values of shear viscosity. We found that to have a substantial amount of wave energy dissipated at the lower corona, one needs to increase shear viscosity by seven orders of magnitude in comparison with the value given by the classical plasma theory. An important result that we obtained is that the efficiency of the wave damping strongly depends on the density variation with the height. The stronger the density decrease, the weaker the wave damping is. On the basis of this result, we suggested a physical explanation of the phenomenon of the enhanced wave damping in equilibrium configurations with exponentially diverging magnetic field lines.

  12. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...

  13. Exploration of the Berry phase interference in a single-molecule magnets of trigonal symmetry

    Science.gov (United States)

    Quddusi, H. M.; Liu, J.; Feng, P. L.; Del Barco, E.; Hill, S.; Hendrickson, D. N.

    2012-02-01

    The quantum behavior of single-molecule magnets (SMM) is mainly governed by their molecular composition and crystallographic symmetries, thus playing an essential role in the tunneling dynamics. We present low temperature magnetometry measurements on a trigonal symmetric, low nuclearity Mn3 SMM. The experiments are designed to explore the behavior of the tunnel splittings within the transverse field magnitude/direction phase space, by applying a transverse field (0-1 T) along different directions within the hard anisotropy plane of the molecules. The expected quantum interference pattern can be understood as an outcome of a competition between different intramolecular magnetic interactions. A multi-spin description using non-collinear zero-field splitting tensors and intra molecular dipolar interactions between the manganese ions is employed to explain the symmetry patterns.

  14. Phase diagram and Chiral Magnetic Effect in Dirac Semimetals from Lattice Simulation

    Directory of Open Access Journals (Sweden)

    Boyda D.L.

    2018-01-01

    Full Text Available Dirac Semimetals Na3Bi and Cd3As2 are recently discovered materials, which low energy electronic spectrum is described by two flavours of massless 3+1D fermions. In order to study electronic properties of these materials we formulated lattice field theory with rooted staggered fermions on anisotropic lattice. It is shown that in the limit of zero temporal lattice spacing this theory reproduces effective theory of Dirac semimetals. Using the lattice field theory we study the phase diagram of Dirac semimetals in the plane effective coupling constant - Fermi velocity anisotropy. We also measure conductivity of Dirac Semimetals within lattice field theory in external magnetic field. Our results confirm the existence of Chiral Magnetic Effect in Dirac Semimetals.

  15. Automated solid-phase subcloning based on beads brought into proximity by magnetic force.

    Science.gov (United States)

    Hudson, Elton P; Nikoshkov, Andrej; Uhlen, Mathias; Rockberg, Johan

    2012-01-01

    In the fields of proteomics, metabolic engineering and synthetic biology there is a need for high-throughput and reliable cloning methods to facilitate construction of expression vectors and genetic pathways. Here, we describe a new approach for solid-phase cloning in which both the vector and the gene are immobilized to separate paramagnetic beads and brought into proximity by magnetic force. Ligation events were directly evaluated using fluorescent-based microscopy and flow cytometry. The highest ligation efficiencies were obtained when gene- and vector-coated beads were brought into close contact by application of a magnet during the ligation step. An automated procedure was developed using a laboratory workstation to transfer genes into various expression vectors and more than 95% correct clones were obtained in a number of various applications. The method presented here is suitable for efficient subcloning in an automated manner to rapidly generate a large number of gene constructs in various vectors intended for high throughput applications.

  16. Magnetic-field-induced Quantum Phase in S = 1/2 Frustrated Trellis Lattice

    Science.gov (United States)

    Yamaguchi, Hironori; Yoshizawa, Daichi; Kida, Takanori; Hagiwara, Masayuki; Matsuo, Akira; Kono, Yohei; Sakakibara, Toshiro; Tamekuni, Yusuke; Miyagai, Hirotsugu; Hosokoshi, Yuko

    2018-04-01

    We present a new model compound of an S = 1/2 frustrated system with ferromagnetic interaction composed of verdazyl radical β-2,3,5-Cl3-V. The ab initio molecular orbital calculation indicates the formation of an S = 1/2 trellis lattice in which zigzag chains and ladders with ferromagnetic rung interaction are two-dimensionally coupled. We observe a field-induced successive phase transition and an unconventional change in the magnetization curve near the saturation field, accompanied by T2 dependence on the magnetic specific heat. A two-dimensional spin-nematic state attributed to the ferromagnetic rung interactions is a possible candidate for the ground state in high-field regions.

  17. Heat Treatment of Iron-Carbon Alloys in a Magnetic Field (Phase 2)

    Energy Technology Data Exchange (ETDEWEB)

    Ludtka, Gerard Michael [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-11-01

    Thermomagnetic processing was shown to shift the phase transformation temperatures and therefore microstructural evolution in the high performance engine valve spring 9254 steel alloy by applying a high magnetic field during cooling. These effects would be anticipated to improve performance such as high cycle fatigue as demonstrated in prior projects. Thermomagnetic processing of gears and crank shafts was constrained by the size of the prototype equipment currently available at ORNL. However, the commercial procurement viability of production scale 9-Tesla, 16-inch diameter bore thermomagnetic processing equipment for truck idler gears up to ~11-inch diameter and potential crank shaft applications was shown, as multiple superconducting magnet manufacturing companies (in conjunction with an induction heat treating company, AjaxTOCCO Magnethermic) offered cryogen-free or cryocooler equipment designs to Cummins.

  18. Magnetic Phase Transition In CocMg1-CO Solid Solutions

    International Nuclear Information System (INIS)

    Mironova-Ulmane, N.; Ulmanis, U.; Kuzmin, A.; Sildos, I.; Pars, M.

    2007-01-01

    Full text: Co c Mg 1-C O system is a nice example of diluted antiferromagnet. It forms a continuous series of solid solutions, whose magnetic properties vary with the composition from antiferromagnetic-like behaviour with the Neel temperature T N =300 K for pure CoO to diamagnetic-like behaviour for pure MgO. For intermediate compositions with c>0.5, the paramagnetic-to-antiferromagnetic phase transition occurs upon cooling. In order to examine the influence of the dilution by diamagnetic ions on the magnetic ordering of single-crystal Co c Mg 1-c O solid solutions, we have performed Raman spectroscopy and domain structure studies. The temperature dependence of the intensity of Raman scattering from Co c Mg 1-c O solid solutions has been measured in a wide range of compositions (0.5< c<1) and temperatures (6 K< T<200 K). The obtained results will be discussed. (Authors)

  19. Magnetic property enhancement through microstructural engineering and phase purity control of ceramic materials

    Science.gov (United States)

    Pietras, John David

    The effects of powder synthesis and processing on the magnetic properties of the high power microwave ceramic yttrium iron garnet ( Y3Fe5O12) and the high temperature superconductor YBa2Cu3O7- x (123) were studied. Yttrium iron garnet was produced through a thermal decomposition technique. It was found that the use of iron sulfate over iron citrate in the stock solution resulted in phase pure Y3Fe5O12 at the relatively low temperature of 1100oC with a short soak time of four hours. The low forming temperature resulted in fine-grained powder that was easily milled. Milled powder was hot forged at 1275oC for 1.5 hours resulting in a 96% dense sample with an average grain size of 1.7 ± 0.6 μm. These samples were found to have a higher critical magnetic field than those presently commercially available; 211 Oe compared to 162 Oe, while not affecting the dielectric or magnetic characteristics. YBa2Cu3O7-x and Y2BaCuO5 (211) were prepared using a combustion synthesis technique. Phase pure 123 and 211 were formed by calcining combusted powder at 900oC for 4 hours and 930oC for 3 hours respectively. Tape casting and lamination were used to form bulk samples of pure 123 sheets and 123 alternated with mixed oxide and combustion synthesized 211 sheets. After melt texturing, the alternating layer structures were found to have a wider magnetization curve, a higher critical current density, a lower degree of liquid egress and a greater resistance to corrosion than either 123 only pellets or laminates.

  20. Non-invasive assessment of pulsatile intracranial pressure with phase-contrast magnetic resonance imaging.

    Directory of Open Access Journals (Sweden)

    Geir Ringstad

    Full Text Available Invasive monitoring of pulsatile intracranial pressure can accurately predict shunt response in patients with idiopathic normal pressure hydrocephalus, but may potentially cause complications such as bleeding and infection. We tested how a proposed surrogate parameter for pulsatile intracranial pressure, the phase-contrast magnetic resonance imaging derived pulse pressure gradient, compared with its invasive counterpart. In 22 patients with suspected idiopathic normal pressure hydrocephalus, preceding invasive intracranial pressure monitoring, and any surgical shunt procedure, we calculated the pulse pressure gradient from phase-contrast magnetic resonance imaging derived cerebrospinal fluid flow velocities obtained at the upper cervical spinal canal using a simplified Navier-Stokes equation. Repeated measurements of the pulse pressure gradient were also undertaken in four healthy controls. Of 17 shunted patients, 16 responded, indicating high proportion of "true" normal pressure hydrocephalus in the patient cohort. However, there was no correlation between the magnetic resonance imaging derived pulse pressure gradient and pulsatile intracranial pressure (R = -.18, P = .43. Pulse pressure gradients were also similar in patients and healthy controls (P = .26, and did not differ between individuals with pulsatile intracranial pressure above or below established thresholds for shunt treatment (P = .97. Assessment of pulse pressure gradient at level C2 was therefore not found feasible to replace invasive monitoring of pulsatile intracranial pressure in selection of patients with idiopathic normal pressure hydrocephalus for surgical shunting. Unlike invasive, overnight monitoring, the pulse pressure gradient from magnetic resonance imaging comprises short-term pressure fluctuations only. Moreover, complexity of cervical cerebrospinal fluid flow and -pulsatility at the upper cervical spinal canal may render the pulse pressure gradient a poor surrogate

  1. Multi-phase EBSD mapping and local texture analysis in NdFeB sintered magnets

    Energy Technology Data Exchange (ETDEWEB)

    Woodcock, T.G., E-mail: t.woodcock@ifw-dresden.de [IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden (Germany); Gutfleisch, O. [IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden (Germany)

    2011-02-15

    A combination of electron backscatter diffraction and energy-dispersive X-ray spectroscopy has been used to identify the crystal structure and composition of all the phases present in commercially available NdFeB sintered magnets and to map their spatial distribution. The Nd{sub 2}Fe{sub 14}B and NdO grains were shown to have low defect densities. The fcc Nd-rich and Nd{sub 2}O{sub 3} grains had intra-grain misorientation angles of up to 14{sup o}, which was shown to be due to defects. Large numbers ({approx}100) of data points for each phase were used to study texture in the NdO, Nd{sub 2}O{sub 3} and Nd{sub 2}Fe{sub 14}B phases. The Nd{sub 2}Fe{sub 14}B grains exhibited a <0 0 1> fibre texture. The Nd oxide phases showed no strong texture, which implied that no strongly preferred orientation relationships between those phases and Nd{sub 2}Fe{sub 14}B exist. The result was shown to be valid for optimally annealed samples exhibiting high coercivity and as-sintered samples exhibiting low coercivity.

  2. Finite-size, chemical-potential and magnetic effects on the phase transition in a four-fermion interacting model

    Energy Technology Data Exchange (ETDEWEB)

    Correa, E.B.S. [Universidade Federal do Sul e Sudeste do Para, Instituto de Ciencias Exatas, Maraba (Brazil); Centro Brasileiro de Pesquisas Fisicas-CBPF/MCTI, Rio de Janeiro (Brazil); Linhares, C.A. [Universidade do Estado do Rio de Janeiro, Instituto de Fisica, Rio de Janeiro (Brazil); Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas-CBPF/MCTI, Rio de Janeiro (Brazil); Malbouisson, J.M.C. [Universidade Federal da Bahia, Instituto de Fisica, Salvador (Brazil); Santana, A.E. [Universidade de Brasilia, Instituto de Fisica, Brasilia, DF (Brazil)

    2017-04-15

    We study effects coming from finite size, chemical potential and from a magnetic background on a massive version of a four-fermion interacting model. This is performed in four dimensions as an application of recent developments for dealing with field theories defined on toroidal spaces. We study effects of the magnetic field and chemical potential on the size-dependent phase structure of the model, in particular, how the applied magnetic field affects the size-dependent critical temperature. A connection with some aspects of the hadronic phase transition is established. (orig.)

  3. Detection of Cerebral Hemorrhage in Rabbits by Time-Difference Magnetic Inductive Phase Shift Spectroscopy

    Science.gov (United States)

    Pan, Wencai; Yan, Qingguang; Qin, Mingxin; Jin, Gui; Sun, Jian; Ning, Xu; Zhuang, Wei; Peng, Bin; Li, Gen

    2015-01-01

    Cerebral hemorrhage, a difficult issue in clinical practice, is often detected and studied with computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). However, these expensive devices are not readily available in economically underdeveloped regions, and hence are unable to provide bedside and emergency on-site monitoring. The magnetic inductive phase shift (MIPS) is an emerging technology that may become a new tool to detect cerebral hemorrhage and to serve as an inexpensive partial substitute to medical imaging. In order to study a wider band of cerebral hemorrhage MIPS and to provide more useful information for measuring cerebral hemorrhage, we established a cerebral hemorrhage magnetic induction phase shift spectroscopy (MIPSS) detection system. Thirteen rabbits with five cerebral hemorrhage states were studied using a single coil-coil within a 1 MHz-200 MHz frequency range in linear sweep. A feature band (FB) with the highest detection sensitivity and the greatest stability was selected for further analysis and processing. In addition, a maximum conductivity cerebrospinal fluid (CSF) MRI was performed to verify and interpret the MIPSS result. The average phase shift change induced by a 3 ml injection of autologous blood under FB was -7.7503° ± 1.4204°, which was considerably larger than our previous work. Data analysis with a non-parametric statistical Friedman M test showed that in the FB, MIPSS could distinguish the five states of cerebral hemorrhage in rabbits, with a statistical significance of phemorrhage severity from a single set of measurements. The results illustrate that the MIPSS detection method is able to provide a new possibility for real-time monitoring and diagnosis of the severity of cerebral hemorrhage. PMID:26001112

  4. Stability considerations of permanent magnet quadrupoles for CESR phase-III upgrade

    Directory of Open Access Journals (Sweden)

    W. Lou

    1998-06-01

    Full Text Available The Cornell electron storage ring (CESR phase-III upgrade plan includes very strong permanent magnet quadrupoles in front of the cryostat for the superconducting quadrupoles and physically as close as possible to the interaction point. Together with the superconducting quadrupoles, they provide tighter vertical focusing at the interaction point. The quadrupoles are built with neodymium iron boron (NdFeB material and operate inside the 15 kG solenoid field. Requirements on the field quality and stability of these quadrupoles are discussed and test results are presented.

  5. Correlation among disorder, electronic and magnetic phases of SrRuO3.

    Science.gov (United States)

    Sarkar, Babusona; Dalal, Biswajit; De, S K

    2015-03-25

    Electric and magnetic properties of Sr1-xBaxRu1-xTixO3 (0 ⩽ x ⩽ 0.8) have been investigated to find the interrelationship between metallicity and ferromagnetism in SrRuO3 (SRO). The simultaneous doping of Sr and Ru with Ba and Ti results in single phase SRO at x = 0.1 and mixed phase of SRO and hexagonal BaTiO3 (h-BTO) at x ⩾ 0.2. Co-doping at Sr and Ru sites gives rise to oxygen vacancy and mixed valency of Ru (Ru(3+) and Ru(4+)). Room temperature resistivity increases due to modification of p(O)-d(Ru) hybridization and phase segregation. Temperature dependent resistivity reveals metal-insulator transition around 232 K at x = 0.1 and insulator down to 2 K at x ⩾ 0.2. The insulating state (x = 0.1) at low temperature is well described by weak localization and electron-electron interaction. Temperature dependence of resistivity (x ⩾ 0.2) follows Mott's three dimensional variable range hopping model. Localization length and average hopping distance decrease with the increase of x, indicating the presence of more disorder. Ferromagnetic transition temperature decreases to 149 K at x = 0.1 and remains constant up to x = 0.5. The Curie-Wiess (CW) temperature (ΘCW) decreases monotonically and becomes negative at x = 0.5. The effective magnetic moment estimated from CW law is smaller than that of pure SRO due to the formation of Ru(3+) ions. The saturation magnetization diminishes, suggesting the demagnetization factor owing to diamagnetic h-BTO. The coercivity increases from 6700 Oe (x = 0) to 12 500 Oe (x = 0.4) and then decreases to 3700 Oe (x = 0.5). Ferromagnetic cluster comprising of doped SRO gives rise to the formation of a Griffith-like phase. The co-occurrence of high jump in resistivity ratio and disappearance of ferromagnetism suggests an interplay between transport process and magnetism at low temperature.

  6. Correlation among disorder, electronic and magnetic phases of SrRuO3

    Science.gov (United States)

    Sarkar, Babusona; Dalal, Biswajit; De, S. K.

    2015-03-01

    Electric and magnetic properties of Sr1-xBaxRu1-xTixO3 (0 ⩽ x ⩽ 0.8) have been investigated to find the interrelationship between metallicity and ferromagnetism in SrRuO3 (SRO). The simultaneous doping of Sr and Ru with Ba and Ti results in single phase SRO at x = 0.1 and mixed phase of SRO and hexagonal BaTiO3 (h-BTO) at x ⩾ 0.2. Co-doping at Sr and Ru sites gives rise to oxygen vacancy and mixed valency of Ru (Ru3+ and Ru4+). Room temperature resistivity increases due to modification of p(O)-d(Ru) hybridization and phase segregation. Temperature dependent resistivity reveals metal-insulator transition around 232 K at x = 0.1 and insulator down to 2 K at x ⩾ 0.2. The insulating state (x = 0.1) at low temperature is well described by weak localization and electron-electron interaction. Temperature dependence of resistivity (x ⩾ 0.2) follows Mott's three dimensional variable range hopping model. Localization length and average hopping distance decrease with the increase of x, indicating the presence of more disorder. Ferromagnetic transition temperature decreases to 149 K at x = 0.1 and remains constant up to x = 0.5. The Curie-Wiess (CW) temperature (ΘCW) decreases monotonically and becomes negative at x = 0.5. The effective magnetic moment estimated from CW law is smaller than that of pure SRO due to the formation of Ru3+ ions. The saturation magnetization diminishes, suggesting the demagnetization factor owing to diamagnetic h-BTO. The coercivity increases from 6700 Oe (x = 0) to 12 500 Oe (x = 0.4) and then decreases to 3700 Oe (x = 0.5). Ferromagnetic cluster comprising of doped SRO gives rise to the formation of a Griffith-like phase. The co-occurrence of high jump in resistivity ratio and disappearance of ferromagnetism suggests an interplay between transport process and magnetism at low temperature.

  7. Fault detection of a Five-Phase Permanent-Magnet Machine

    DEFF Research Database (Denmark)

    Bianchini, Claudio; Matzen, Torben N.; Bianchi, Nicola

    2008-01-01

    The paper focuses on the fault detection of a five-phase Permanent-Magnet (PM) machine. This machine has been de-signed for fault tolerant applications, and it is characterised by a mutual inductance equal to zero and a high self inductance, with the purpose to limit the short circuit current....... The effects of a limited number of short-circuited turns were investigated by theoretical and Finite Element (FE) analysis, and then a procedure for fault detection has been proposed, focusing on the severity of the fault (i.e. the number of short-circuited turns and the related current)....

  8. Phase contrast image simulations for electron holography of magnetic and electric fields.

    Science.gov (United States)

    Beleggia, Marco; Pozzi, Giulio

    2013-06-01

    The research on flux line lattices and pancake vortices in superconducting materials, carried out within a long and fruitful collaboration with Akira Tonomura and his group at the Hitachi Advanced Research Laboratory, led us to develop a mathematical framework, based on the reciprocal representation of the magnetic vector potential, that enables us to simulate realistic phase images of fluxons. The aim of this paper is to review the main ideas underpinning our computational framework and the results we have obtained throughout the collaboration. Furthermore, we outline how to generalize the approach to model other samples and structures of interest, in particular thin ferromagnetic films, ferromagnetic nanoparticles and p-n junctions.

  9. Phase controlled synthesis of (Mg, Ca, Ba)-ferrite magnetic nanoparticles with high uniformity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.F., E-mail: wangshifa2006@yeah.net [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Science and technology on vacuum technology and physics laboratory, Lanzhou Institute of Physics, Lanzhou 730000, Gansu (China); Li, Q. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Zu, X.T., E-mail: xtzu@uestc.edu.cn [Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Xiang, X.; Liu, W. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Li, S., E-mail: sean.li@unsw.edu.au [School of Material Science and Engineering, University of New South Wales, Sydney 2052 (Australia)

    2016-12-01

    (Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M{sup 2+} ion active sites were coordinated by −OH of the water molecules except for EDTA anions. The MFe{sub 2}O{sub 4} magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe{sub 2}O{sub 4} of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly. - Graphical abstract: Schematic representation of the proposed model for MFe{sub 2}O{sub 4} nanoparticle synthesis, starting from EDTA-chelated M{sup 2+} (M=Mg, Ca, or Ba) cations (left). High dispersion (Mg, Ca, Ba)-ferrite magnetic nanoparticles were prepared by a modified polyacrylamide gel route. Optimized utilization of polysaccharide, chelating agent, and sintering temperature allowed the formation of (Mg, Ca, Ba)-ferrite nanoparticles with a narrow diameter distribution. - Highlights: • We report a modified polyacrylamide gel route to synthesize (Mg, Ca, Ba)-ferrite magnetic nanoparticles. • Chelate mechanism of metal ions (Mg, Ca, Ba) and EDTA has been discussed. • Phase transformation process of (Mg, Ca, Ba)-ferrites has been discussed. • The preparation method increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles.

  10. Transcranial magnetic stimulation-induced global propagation of transient phase resetting associated with directional information flow

    Directory of Open Access Journals (Sweden)

    Masahiro eKawasaki

    2014-03-01

    Full Text Available Electroencephalogram (EEG phase synchronization analyses can reveal large-scale communication between distant brain areas. However, it is not possible to identify the directional information flow between distant areas using conventional phase synchronization analyses. In the present study, we applied transcranial magnetic stimulation (TMS to the occipital area in subjects who were resting with their eyes closed, and analyzed the spatial propagation of transient TMS-induced phase resetting by using the transfer entropy (TE, to quantify the causal and directional flow of information. The time-frequency EEG analysis indicated that the theta (5 Hz phase locking factor (PLF reached its highest value at the distant area (the motor area in this study, with a time lag that followed the peak of the transient PLF enhancements of the TMS-targeted area at the TMS onset. PPI (phase-preservation index analyses demonstrated significant phase resetting at the TMS-targeted area and distant area. Moreover, the TE from the TMS-targeted area to the distant area increased clearly during the delay that followed TMS onset. Interestingly, the time lags were almost coincident between the PLF and TE results (152 vs. 165 ms, which provides strong evidence that the emergence of the delayed PLF reflects the causal information flow. Such tendencies were observed only in the higher-intensity TMS condition, and not in the lower-intensity or sham TMS conditions. Thus, TMS may manipulate large-scale causal relationships between brain areas in an intensity-dependent manner. We demonstrated that single-pulse TMS modulated global phase dynamics and directional information flow among synchronized brain networks. Therefore, our results suggest that single-pulse TMS can manipulate both incoming and outgoing information in the TMS-targeted area associated with functional changes.

  11. Interplay between structural and magnetic phase transitions in copper ferrite studied with high-resolution neutron diffraction

    Science.gov (United States)

    Balagurov, A. M.; Bobrikov, I. A.; Pomjakushin, V. Yu.; Sheptyakov, D. V.; Yushankhai, V. Yu.

    2015-01-01

    A detailed neutron diffraction study of copper ferrite in a broad temperature range has allowed to precisely access the peculiarities of magnetic and structural phase transitions in it. On heating from 2 to 820 K, a fully inverted tetragonal (sp. gr. I41/amd) spinel CuFe2O4 is observed up to a TC≈660 K, where a cubic phase (sp. gr. Fd3m) appears, and up to T≈700 K, both structural phases coexist. The inversion parameter of spinel structure does not change at the transition to the cubic phase. Deformation of the (Cu,Fe)O6 octahedra in the tetragonal phase corresponds to the Jahn-Teller nature of the structural phase transition. Néel ferrimagnetic structure - a ferromagnetic ordering of the magnetic moments of Fe3+ in the tetrahedral (A) and moments of Fe3+ and Cu2+ in the octahedral (B) positions with opposite directions of magnetization of the sublattices - disappears at TN≈750 K. The magnetic moment in the A-positions (Fe3+) and the total one in the B-positions (Fe3++Cu2+) at Ttheory. In the co-existence range of structural phases diffraction peaks are significantly broadened. The size effects providing the main contribution to peak broadening is also superimposed with the microstrain-conditioned peak broadening. In the tetragonal phase, microstrains in the crystallites are highly anisotropic.

  12. Analysis of a fully packed loop model arising in a magnetic Coulomb phase.

    Science.gov (United States)

    Jaubert, L D C; Haque, M; Moessner, R

    2011-10-21

    The Coulomb phase of spin ice, and indeed the I(c) phase of water ice, naturally realize a fully packed two-color loop model in 3D. We present a detailed analysis of the statistics of these loops: we find loops spanning the system multiple times hosting a finite fraction of all sites while the average loop length remains finite. We contrast the behavior with an analogous 2D model. We connect this body of results to properties of polymers, percolation and insights from Schramm-Loewner evolution processes. We also study another extended degree of freedom, called worms, which appear as "Dirac strings" in spin ice. We discuss implications of these results for the efficiency of numerical cluster algorithms, and address implications for the ordering properties of a broader class of magnetic systems, e.g., with Heisenberg spins, such as CsNiCrF(6) or ZnCr(2)O(4). © 2011 American Physical Society

  13. High-field magnetization and magnetic phase diagrams in Nd.sub.2./sub.RhIn.sub.8./sub. and Tb.sub.2./sub.RhIn.sub.8./sub..

    Czech Academy of Sciences Publication Activity Database

    Javorský, P.; Pajskr, K.; Klicpera, M.; Čermák, P.; Skourski, Y.; Andreev, Alexander V.

    2014-01-01

    Roč. 598, Jun (2014), 278–281 ISSN 0925-8388 Grant - others:AVČR(CZ) M100101203 Institutional support: RVO:68378271 Keywords : magnetic phase diagrams * high magnetic field * magnetization Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.999, year: 2014

  14. Measurement of unique magnetic and superconducting phases in oxygen-doped high-temperature superconductors La2-xSrxCuO4+y

    DEFF Research Database (Denmark)

    Udby, Linda; Larsen, Jacob; Christensen, Niels Bech

    2013-01-01

    We present a combined magnetic neutron scattering and muon spin rotation study of the nature of the magnetic and superconducting phases in electronically phase separated La2-xSrxCuO4+y, x=0.04, 0.065, 0.09. For all samples, we find long-range modulated magnetic order below TN≃Tc=39 K. In sharp...

  15. Liquid carry-over in an injection moulded all-polymer chip system for immiscible phase magnetic bead-based solid-phase extraction

    International Nuclear Information System (INIS)

    Kistrup, Kasper; Skotte Sørensen, Karen; Wolff, Anders; Fougt Hansen, Mikkel

    2015-01-01

    We present an all-polymer, single-use microfluidic chip system produced by injection moulding and bonded by ultrasonic welding. Both techniques are compatible with low-cost industrial mass-production. The chip is produced for magnetic bead-based solid-phase extraction facilitated by immiscible phase filtration and features passive liquid filling and magnetic bead manipulation using an external magnet. In this work, we determine the system compatibility with various surfactants. Moreover, we quantify the volume of liquid co-transported with magnetic bead clusters from Milli-Q water or a lysis-binding buffer for nucleic acid extraction (0.1 (v/v)% Triton X-100 in 5 M guanidine hydrochloride). A linear relationship was found between the liquid carry-over and mass of magnetic beads used. Interestingly, similar average carry-overs of 1.74(8) nL/µg and 1.72(14) nL/µg were found for Milli-Q water and lysis-binding buffer, respectively. - Highlights: • We present an all-polymer mass producible passive filled microfluidic chip system. • Rapid system fabrication is obtained by injection moulding and ultrasonic welding. • The system is made for single-use nucleic acid extraction using magnetic beads. • We systematically map compatibility of the chip system with various surfactants. • We quantify the volume carry-over of magnetic beads in water and 0.1% triton-X solution

  16. Liquid carry-over in an injection moulded all-polymer chip system for immiscible phase magnetic bead-based solid-phase extraction

    Energy Technology Data Exchange (ETDEWEB)

    Kistrup, Kasper, E-mail: kkis@nanotech.dtu.dk [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kongens Lyngby (Denmark); Skotte Sørensen, Karen, E-mail: karen@nanotech.dtu.dk [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kongens Lyngby (Denmark); Center for Integrated Point of Care Technologies (CiPoC), DELTA, Venlighedsvej 4, DK-2870 Hørsholm (Denmark); Wolff, Anders, E-mail: anders.wolff@nanotech.dtu.dk [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kongens Lyngby (Denmark); Fougt Hansen, Mikkel, E-mail: mikkel.hansen@nanotech.dtu.dk [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kongens Lyngby (Denmark)

    2015-04-15

    We present an all-polymer, single-use microfluidic chip system produced by injection moulding and bonded by ultrasonic welding. Both techniques are compatible with low-cost industrial mass-production. The chip is produced for magnetic bead-based solid-phase extraction facilitated by immiscible phase filtration and features passive liquid filling and magnetic bead manipulation using an external magnet. In this work, we determine the system compatibility with various surfactants. Moreover, we quantify the volume of liquid co-transported with magnetic bead clusters from Milli-Q water or a lysis-binding buffer for nucleic acid extraction (0.1 (v/v)% Triton X-100 in 5 M guanidine hydrochloride). A linear relationship was found between the liquid carry-over and mass of magnetic beads used. Interestingly, similar average carry-overs of 1.74(8) nL/µg and 1.72(14) nL/µg were found for Milli-Q water and lysis-binding buffer, respectively. - Highlights: • We present an all-polymer mass producible passive filled microfluidic chip system. • Rapid system fabrication is obtained by injection moulding and ultrasonic welding. • The system is made for single-use nucleic acid extraction using magnetic beads. • We systematically map compatibility of the chip system with various surfactants. • We quantify the volume carry-over of magnetic beads in water and 0.1% triton-X solution.

  17. Low temperature spin-glass-like phases in magnetic nano-granular composites

    KAUST Repository

    Zhang, Bei

    2012-09-01

    It is a common understanding that the dipole-dipole interaction among the magnetic nanoparticles may result in a low-temperature spin-glass phase, which has been evidenced by observation of aging effect and memory effect. However, several studies on the nano-particles systems showed that some of the observed spin-glass-like phenomena could be due to the existence of spin-glasslike shells surrounding the ferrimagnetic cores. Therefore, it is very important to understand that how the dipole-dipole interaction induce the spin-glass phase. In order to address this issue, we have fabricated Co-SiO 2 and Fe-SiO 2 nano-granular thin films and measured the memory effect for them. Spin-glass-like phase has been observed at low temperatures. We found that, after annealing, the size of the clusters increased significantly. Based on a simple model, the dipole-dipole interaction between the clusters must be increased accordingly for the annealed samples. Interestingly, the memory effect is greatly weakened in the annealed films, which strongly suggested that the dipole-dipole interaction may not be the major factor for the formation of the low-temperature spin-glass-like phase. Copyright © 2012 American Scientific Publishers All rights reserved.

  18. Chemical synthesis, phase transformation and magnetic proprieties of FePt and FePd nanoparticles

    International Nuclear Information System (INIS)

    Delattre, Anastasia

    2010-01-01

    This work aims at understanding the chemical synthesis of FePt and FePd nanoparticles (NPs), and at exploring how to implement the phase transformation from the chemically disordered to the L10 phase, without coalescence. Using hexadecanenitrile instead of oleylamine, we obtain NPs with a more homogenous internal composition, instead of core-shell NPs. Through a systematic study (designed experiment relying on Taguchi tables), we developed the FePd synthesis, while evidencing the role of each ligand and of the reductor. To induce the crystalline phase transformation while avoiding coalescence, we explored two ways. In the first one, atomic vacancies are introduced in the NPs through light ion irradiation, atomic mobility being ensured by annealing at moderate temperature (300 C). As a result, the blocking temperature is multiplied by 4, due to anisotropy enhancement. However, strong chemical ordering in the L10 phase cannot be achieved. The second approach relies on the dispersion of the NPs in a salt (NaCl) matrix, prior to annealing at 700 C: high chemical ordering is achieved, and the blocking temperature is beyond 400 C. We then developed a single-step process to remove the salt by dissolution in water and to re-disperse NPs in stable aqueous or organics solutions. These high magnetic anisotropy NPs are then readily available for further chemical or manipulation steps, with applied perspectives in areas such as data storage, or biology. (author)

  19. Preliminary magnetic studies of lagoon and stream sediments from Chascomús Area (Argentina)—magnetic parameters as indicators of heavy metal pollution and some results of using an experimental method to separate magnetic phases

    Science.gov (United States)

    Chaparro, Marcos A. E.; Lirio, Juan M.; Nuñez, Héctor; Gogorza, Claudia S. G.; Sinito, Ana M.

    2005-11-01

    Magnetic properties of lagoon and stream sediments from Chascomús area (Buenos Aires Province) and the relevance of various magnetic parameters as giving pollution status are studied in the present work. This work is focussed on magnetic parameters, such as concentration-dependent (magnetic susceptibility, saturation anhysteric and isothermal remanent magnetisation) and feature-dependent parameters (S-ratio, coercivity of remanence, anhysteric susceptibility/magnetic susceptibility-ratio), as pollution indicators. Firstly and most importantly, different magnetic parameters and chemical measurements were correlated in order to investigate their goodness, obtaining the best results for feature-dependent magnetic parameters. Coercivity of remanence correlate very well with chemical variables, showing correlations at high level of significance up to 0.9094, and the anhysteric susceptibility/magnetic susceptibility-ratio also shows very good correlations (up to 0.8376). Some results and advantages of using a new experimental method in order to discriminate hard and soft magnetic phases are also shown. This method uses alternately backfield isothermal remanent magnetisation and alternating field demagnetisation. From the experimental separation, the presence of hard magnetic phases in some samples was confirmed.

  20. Enhanced spectrofluorimetric determination of aflatoxin M1 in liquid milk after magnetic solid phase extraction

    Science.gov (United States)

    Hashemi, Mahdi; Taherimaslak, Zohreh; Rashidi, Somayeh

    2014-07-01

    A simple and sensitive method using magnetic solid phase extraction (MSPE) followed by spectrofluorimetric detection has been developed for separation and determination of aflatoxin M1 (AFM1) in liquid milk. The method is based on the extraction of AFM1 on the modified magnetic nanoparticles (MMNPs) and subsequent derivatization of extracted AFM1 to AFM1 hemi-acetal derivative (AFM2a) by reaction with trifluoroacetic acid (TFA) for spectrofluorimetric detection. Magnetic nanoparticles (MNPs) coated by 3-(trimethoxysilyl)-1-propantiol (TMSPT) and modified with 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) were used as adsorbent in MSPE procedure. Influential parameters affecting the extraction efficiency were investigated and optimized. Under the optimum conditions the calibration curve for AFM1 determination showed good linearity in the range 0.030-10.0 μg L-1 (R2 = 0.9991). The repeatability and reproducibility (RSD%) for 0.050 μg L-1 of AFM1 were 4.5% and 5.3%, respectively and limit of detection limit (S/N = 3) was estimated to be 0.010 μg L-1. The developed method was successfully applied for extraction of AFM1 from spiked liquid milk and natural contaminated liquid milk. The good spiked recoveries ranging from 91.6% to 96.1% were obtained. The results demonstrated that the developed method is simple, inexpensive, accurate and remarkably free from interference effects.

  1. Dynamic Phase Transitions In The Spin-2 Ising System Under An Oscillating Magnetic Field Within The Effective-Field Theory

    International Nuclear Information System (INIS)

    Ertas, Mehmet; Keskin, Mustafa; Deviren, Bayram

    2010-01-01

    The dynamic phase transitions are studied in the spin-2 Ising model under a time-dependent oscillating magnetic field by using the effective-field theory with correlations. The effective-field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.

  2. On magnetic field strength effect on velocity and turbulence characterization using Phase-Contrast Magnetic Resonance Imaging (PC-MRI)

    Science.gov (United States)

    van de Moortele, Pierre-Francois; Amili, Omid; Coletti, Filippo; Toloui, Mostafa

    2017-11-01

    Cardiovascular flows are predominantly laminar. Nevertheless, transient and even turbulent flows have been observed in the vicinity of the heart (e.g. valves, ascending aorta, valvular/vascular stenosis). Effective in-vivo hemodynamic-based diagnostics in these sites require both high-resolution velocity measurements (especially in the near-vessel wall regions) and accurate evaluation of blood flow turbulence level (e.g. in terms of TKE). In addition to phase contrast (PC), appropriately designed PC-MRI sequences provide intravoxel incoherent motion encoding, a unique tool for simultaneous, non-invasive evaluation of velocity 3D vector fields and Reynolds stresses in cardiovascular flows in vivo. However, limited spatial and temporal resolution of PC-MRI result in inaccuracies in the estimation of hemodynamics (e.g. WSS) and of flow turbulence characteristics. This study aims to assess whether SNR gains at higher magnetic field could overcome these limits, providing more accurate velocity and turbulence characterization at higher spatial resolution. Experiments are conducted on MR Scanners at 3 and 7 Tesla with a U-bent pipe flow shaped phantom. 3D velocity fields, Reynolds stresses and TKE are analyzed and compared to a reference PIV experiments.

  3. Mach-Zehnder interferometer by utilizing phase modulation of transmitted light through magnetic fluid films possessing tunable refractive index

    International Nuclear Information System (INIS)

    Hong, C.-Y.; Yang, S.Y.; Fang, K.L.; Horng, H.E.; Yang, H.C.

    2006-01-01

    Due to its diverse applications in photonics, bio-sensors, mechanics, etc., Mach-Zehnder interferometer becomes one of important devices. Hence, lots of efforts have been paid to develop advanced Mach-Zehnder interferometers. In this work, we explore new-model Mach-Zehnder interferometer, in which one of arm is consisted of magnetic fluid films. By utilizing the tunable refractive index of magnetic fluid films under external magnetic fields, the traveling phase of a propagating light through the magnetic fluid film is changed. This could lead to a variation in the interfered intensity of the Mach-Zehnder interferometer when an external magnetic field is applied. The modulation in the interfered intensity by the external magnetic field is demonstrated experimentally, and the relevant physical origin is also discussed

  4. Magnetic inductive phase shift: a new method to differentiate hemorrhagic stroke from ischemic stroke on rabbit.

    Science.gov (United States)

    Yan, Qingguang; Jin, Gui; Ma, Ke; Qin, Mingxin; Zhuang, Wei; Sun, Jian

    2017-05-30

    The major therapy for ischemic stroke is thrombolytic treatment, but severe consequences occur when this method is used to treat hemorrhagic stroke. Currently, computed tomography and magnetic resonance imaging are used to differentiate between two types of stroke, but these two methods are ineffective for pre-hospital care. We developed a new brain diagnostic device for rabbits based on electromagnetic induction to non-invasively differentiate two types of stroke. The device includes two coils and a phase difference measurement system that detects the magnetic inductive phase shift (MIPS) value to reflect the tissue's condition. The hemorrhage model was established through the injection of autologous blood into the internal capsule of a rabbit's brain. Ischemia was induced in the brain of a rabbit by bilateral carotid artery occlusion. Two types of animal models were measured with our device. The MIPS value gradually decreased with increasing injected blood and increased with ischemia time. The MIPS changes induced by the two types of strokes were exact opposites, and the absolute values of MIPS variation in the hemorrhagic and the ischemic groups were significantly larger than those of the normal control group (P stroke from hemorrhagic stroke on rabbit brain in a non-invasive, continuous, and bulk monitoring manner by using a simple and inexpensive apparatus.

  5. Phase Behavior and Magnetic Alignment of Hydrogen Bonded Side Chain Liquid Crystalline Block Copolymers

    Science.gov (United States)

    Gopinadhan, Manesh; Majewski, Pawel; Beach, Evan; Anastas, Paul; Osuji, Chinedum

    2010-03-01

    Hydrogen bonding between a poly(styrene-b-acrylic acid) backbone and an imidazole terminated biphenyl mesogen results in the formation of a side-group liquid crystalline block copolymer (LC BCP).We use a combination of FTIR, X-ray scattering and DSC to characterize the phase behavior of the PAA-LC system, which is largely dominated by the sub-stoichiometric saturation of the binding capacity of the chain. In the melt, the self assembled materials exhibited composition and temperature dependent smectic LC phases along with characteristic birefringence and multiple thermal transitions associated with LC polymers. The diblock copolymers (LC BCP) microphase separated into lamellar microdomains with homeotropic anchoring at the IMDS. Alignment of a hierarchically ordered lamellar BCP was performed using a 5 T magnetic field at elevated temperature in the melt state and characterized by SAXS. The system exhibits a tilted smectic structure, which on alignment by the field displays scattering patterns akin to those observed in bookshelf or chevron-type structures. These results demonstrate that simple non-covalent interactions can be used to generate LC order and thus provide a convenient handle for subsequent alignment of BCP structures by magnetic fields.

  6. Nontrivial Berry phase in magnetic BaMnSb2 semimetal

    Science.gov (United States)

    Huang, Silu; Kim, Jisun; Shelton, W. A.; Plummer, E. W.; Jin, Rongying

    2017-06-01

    The subject of topological materials has attracted immense attention in condensed-matter physics because they host new quantum states of matter containing Dirac, Majorana, or Weyl fermions. Although Majorana fermions can only exist on the surface of topological superconductors, Dirac and Weyl fermions can be realized in both 2D and 3D materials. The latter are semimetals with Dirac/Weyl cones either not tilted (type I) or tilted (type II). Although both Dirac and Weyl fermions have massless nature with the nontrivial Berry phase, the formation of Weyl fermions in 3D semimetals require either time-reversal or inversion symmetry breaking to lift degeneracy at Dirac points. Here we demonstrate experimentally that canted antiferromagnetic BaMnSb2 is a 3D Weyl semimetal with a 2D electronic structure. The Shubnikov-de Hass oscillations of the magnetoresistance give nearly zero effective mass with high mobility and the nontrivial Berry phase. The ordered magnetic arrangement (ferromagnetic ordering in the ab plane and antiferromagnetic ordering along the c axis below 286 K) breaks the time-reversal symmetry, thus offering us an ideal platform to study magnetic Weyl fermions in a centrosymmetric material.

  7. Magnetically assisted matrix solid phase dispersion for extraction of parabens from breast milks.

    Science.gov (United States)

    Fotouhi, Mina; Seidi, Shahram; Shanehsaz, Maryam; Naseri, Mohammad Taghi

    2017-06-30

    In the present work, magnetically assisted matrix solid phase dispersion (MA-MSPD) was used as an efficient solid phase extraction method. MA-MSPD followed by a dispersive liquid-liquid microextraction (DLLME) was applied for determination of parabens in breast milks. The analysis were performed using LC-UV and LC-MS/MS. Poly(indole-thiophene) coated magnetic graphene oxide (MGO@PIT) was synthesized, characterized and used as the sorbent. Na 2 SO 4 was used as the drying salt as well as matrix dispersing agent. Exact amounts of MGO@PIT and Na 2 SO 4 were added into 200μL volume of the milk and the mixture was gently blended to obtain a dry powder. The blend was dispersed into ultrapure water and stirred. Because of dissolving of the matrix dispersant in water, only the magnetic sorbent is remained into water which can be easily separated by a magnet. Next, the sorbent was eluted with a suitable solvent to desorb the analyte and the eluent was used as the disperser solvent for the subsequent DLLME. In this approach, the target analytes were directly adsorbed on the surface of the magnetic sorbent without any sample pretreatment. Compared with conventional MSPD, MA-MSPD increases the simplicity of the extraction procedure, decreases the extraction time and eliminates the column packing as well as its related drawbacks. The optimum extraction parameters were obtained as 50mg of MGO@PIT, 550mg of Na 2 SO 4 in 200μL of the milk sample, 1.0mL of methanol as the eluent solvent under fierce vortex for 2.0min and 100μL of 1-octanol as the extraction solvent. Under the optimal conditions, the extraction recoveries greater than 83% were obtained, and LOD and LOQ values were found 25ngmL -1 (about 0.5ngmL -1 by LC-MS/MS) and 50ngmL -1 using LC-UV, respectively. The calibration curves were in the range of 50-4000ngmL -1 with the determination coefficients (R 2 ) higher than 0.998. Relative standard deviations (RSD%) for intra- and inter-day precisions were less than 7.5% and

  8. Magnetic properties of NiMn{sub 2}O{sub 4−δ} (nickel manganite): Multiple magnetic phase transitions and exchange bias effect

    Energy Technology Data Exchange (ETDEWEB)

    Tadic, Marin, E-mail: marint@vinca.rs [Condensed Matter Physics Laboratory, Vinca Institute of Nuclear Sciences, University of Belgrade, POB 522, 11001 Belgrade (Serbia); Savic, S.M. [Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Jaglicic, Z. [University of Ljubljana, Faculty of Civil Engineering and Geodesy and Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana (Slovenia); Vojisavljevic, K.; Radojkovic, A.; Prsic, S. [Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Nikolic, Dobrica [Department of Physics, University of Belgrade Faculty of Mining and Geology, Belgrade (Serbia)

    2014-03-05

    Highlights: • We have successfully synthesized NiMn{sub 2}O{sub 4−δ} sample by complex polymerization synthesis. • Magnetic measurements reveal complex properties and triple magnetic phase transitions. • Magnetic measurements of M(H) show hysteretic behavior below 120 K. • Hysteresis properties after cooling of the sample in magnetic field show exchange bias effect. -- Abstract: We present magnetic properties of NiMn{sub 2}O{sub 4−δ} (nickel manganite) which was synthesized by complex polymerization synthesis method followed by successive heat treatment and final calcinations in air at 1200 °C. The sample was characterized by using X-ray powder diffractometer (XRPD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM) and superconducting quantum interference device (SQUID) magnetometer. The XRPD and FE-SEM studies revealed NiMn{sub 2}O{sub 4−δ} phase and good crystallinity of particles. No other impurities have been observed by XRPD. The magnetic properties of the sample have been studied by measuring the temperature and field dependence of magnetization. Magnetic measurements of M(T) reveal rather complex magnetic properties and multiple magnetic phase transitions. We show three magnetic phase transitions with transition temperatures at T{sub M1} = 35 K (long-range antiferromagnetic transition), T{sub M2} = 101 K (antiferromagnetic-type transition) and T{sub M3} = 120 K (ferromagnetic-like transition). We found that the T{sub M1} transition is strongly dependent on the strength of the applied magnetic field (T{sub M1} decreases with increasing applied field) whereas the T{sub M3} is field independent. Otherwise, the T{sub M2} maximum almost disappears in higher applied magnetic fields (H = 1 kOe and 10 kOe). Magnetic measurements of M(H) show hysteretic behavior below T{sub M3}. Moreover, hysteresis properties measured after cooling of the sample in magnetic field of 10 kOe show exchange bias effect with an

  9. Exchange-biased AMR bridges for magnetic field sensing and biosensing

    DEFF Research Database (Denmark)

    Hansen, Mikkel Fougt; Rizzi, Giovanni

    2017-01-01

    We introduce magnetic field sensor bridges that are formed by combinations of stripes of an exchange-pinned magnetic stack displaying anisotropic magnetoresistance. We present a systematic overview on how the stripe geometries can be combined to form sensor bridges with a scalable signal and how...

  10. Isolation/separation of plasmid DNA using hemoglobin modified magnetic nanocomposites as solid-phase adsorbent.

    Science.gov (United States)

    Chen, Xu-Wei; Mao, Quan-Xing; Liu, Jia-Wei; Wang, Jian-Hua

    2012-10-15

    Hemoglobin (Hb) modified magnetic nanocomposites are prepared by immobilization of Hb onto the surface of amino-functionalized Fe(3)O(4)@SiO(2) magnetic nanoparticles via covalent bonding with glutaraldehyde as cross-linker. The obtained nanocomposites are characterized with FT-IR, SEM, XRD and surface charge analysis. A direct solid-phase extraction procedure for the isolation/separation of plasmid DNA using this nanocomposite as a novel adsorbent is thus developed. Some important experimental parameters governing the sorption efficiency, i.e., the pH of sample solution and the ionic strength, are investigated. The Hb modified magnetic nanocomposites provide a sorption capacity of 27.86 mg g(-1) for DNA. By using 2.0mg of the nanocomposites as sorption medium and a suitable acidity of pH 6.1, a sorption efficiency of 93% is achieved for 25 μg mL(-1) of DNA in 1.0 mL of sample solution. Afterwards, the absorbed DNA could be readily recovered by using 1.0 mL of Tris-HCl buffer (pH 8.9, 0.01 mol L(-1)), giving rise to a recovery of ca. 68.3%. The present solid-phased extraction protocol is applied for the isolation of plasmid DNA from Escherichia coli culture, resulting in comparable yield and purity of plasmid DNA with respect to those obtained by using commercial kits. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Discovery of slow magnetic fluctuations and critical slowing down in the pseudogap phase of YBa2Cu3O y .

    Science.gov (United States)

    Zhang, Jian; Ding, Zhaofeng; Tan, Cheng; Huang, Kevin; Bernal, Oscar O; Ho, Pei-Chun; Morris, Gerald D; Hillier, Adrian D; Biswas, Pabitra K; Cottrell, Stephen P; Xiang, Hui; Yao, Xin; MacLaughlin, Douglas E; Shu, Lei

    2018-01-01

    The origin of the pseudogap region below a temperature T * is at the heart of the mysteries of cuprate high-temperature superconductors. Unusual properties of the pseudogap phase, such as broken time-reversal and inversion symmetry are observed in several symmetry-sensitive experiments: polarized neutron diffraction, optical birefringence, dichroic angle-resolved photoemission spectroscopy, second harmonic generation, and polar Kerr effect. These properties suggest that the pseudogap region is a genuine thermodynamic phase and are predicted by theories invoking ordered loop currents or other forms of intra-unit-cell (IUC) magnetic order. However, muon spin rotation (μSR) and nuclear magnetic resonance (NMR) experiments do not see the static local fields expected for magnetic order, leaving room for skepticism. The magnetic resonance probes have much longer time scales, however, over which local fields could be averaged by fluctuations. The observable effect of the fluctuations in magnetic resonance is then dynamic relaxation. We have measured dynamic muon spin relaxation rates in single crystals of YBa 2 Cu 3 O y (6.72 neutron diffraction. Equally important, these fluctuations exhibit the critical slowing down at T mag expected near a time-reversal symmetry breaking transition. Our results explain the absence of static magnetism and provide support for the existence of IUC magnetic order in the pseudogap phase.

  12. Magnetic and dielectric studies of Fe substituted sillenite phase bismuth cobaltite nanoparticles

    International Nuclear Information System (INIS)

    Ray, J.; Biswal, A.K.; Kuila, S.; Vishwakarma, P.N.

    2015-01-01

    Highlights: • The samples prepared under ambient conditions, crystalizes in sillenite phase. • Ferrimagnetic ordering in BCO occurs at 30 K, with no bifurcation in ZFC and FC. • BCFO shows large bifurcation in ZFC and FC data as the sample is cooled down. • Dielectric loss improves by one order when 50% of cobalt is replaced with Fe. • Well distinguished extrinsic and intrinsic contributions in BCO and BCFO are seen. - Abstract: (Bi 13 Co 12 )CoO 40 (BCO) and (Bi 13 Co 5.5 Fe 6.5 )CoO 40 (BCFO) nanoparticles are prepared by sol–gel auto combustion method. The X-ray diffraction study (XRD) reveals cubic crystal structure with space group I23. Surface scanning via atomic force microscopy shows the particle size decreases from 100 nm to 75 nm on partially substituting Fe at Co site. At room temperature, BCO is paramagnetic and shows signature of magnetic ordering at 30 K, which seems to be competing paramagnetic and antiferromagnetic behavior. No sign of magnetic disorder is seen, though indication of magnetic frustration is seen. Interestingly, the Fe substituted BCFO shows large magnetic disorder (even at room temperature) with strengthening ferromagnetic ordering as the temperature is lowered. The low temperature dielectric and magnetodielectric measurement shows dominance of extrinsic contributions, through-out the temperature range for BCO. For BCFO, the behavior may be divided under two regions viz., intrinsic (<260 K) and extrinsic (>260 K). Relaxation in both the regions is described by Arrhenius behavior with activation energies 0.25 eV and 0.04 eV in the extrinsic and intrinsic regions respectively. Most interestingly, the dielectric loss decreases by one order for Fe substituted sample. The Haverliak–Negami equation is found to better describe the observed relaxation data

  13. MAGNET

    CERN Multimedia

    Benoit Curé

    The magnet subsystems resumed operation early this spring. The vacuum pumping was restarted mid March, and the cryogenic power plant was restarted on March 30th. Three and a half weeks later, the magnet was at 4.5 K. The vacuum pumping system is performing well. One of the newly installed vacuum gauges had to be replaced at the end of the cool-down phase, as the values indicated were not coherent with the other pressure measurements. The correction had to be implemented quickly to be sure no helium leak could be at the origin of this anomaly. The pressure measurements have been stable and coherent since the change. The cryogenics worked well, and the cool-down went quite smoothly, without any particular difficulty. The automated start of the turbines had to be fine-tuned to get a smooth transition, as it was observed that the cooling power delivered by the turbines was slightly higher than needed, causing the cold box to stop automatically. This had no consequence as the cold box safety system acts to keep ...

  14. Sustained eruptions on Enceladus explained by turbulent dissipation in tiger stripes

    Science.gov (United States)

    Kite, Edwin S.; Rubin, Allan M.

    2016-04-01

    Spacecraft observations suggest that the plumes of Saturn’s moon Enceladus draw water from a subsurface ocean, but the sustainability of conduits linking ocean and surface is not understood. Observations show eruptions from “tiger stripe” fissures that are sustained (although tidally modulated) throughout each orbit, and since the 2005 discovery of the plumes. Peak plume flux lags peak tidal extension by ˜1 rad, suggestive of resonance. Here, we show that a model of the tiger stripes as tidally flexed slots that puncture the ice shell can simultaneously explain the persistence of the eruptions through the tidal cycle, the phase lag, and the total power output of the tiger stripe terrain, while suggesting that eruptions are maintained over geological timescales. The delay associated with flushing and refilling of O(1)-m-wide slots with ocean water causes erupted flux to lag tidal forcing and helps to buttress slots against closure, while tidally pumped in-slot flow leads to heating and mechanical disruption that staves off slot freezeout. Much narrower and much wider slots cannot be sustained. In the presence of long-lived slots, the 106-y average power output of the tiger stripes is buffered by a feedback between ice melt-back and subsidence to O(1010) W, which is similar to observed power output, suggesting long-term stability. Turbulent dissipation makes testable predictions for the final flybys of Enceladus by Cassini. Our model shows how open connections to an ocean can be reconciled with, and sustain, long-lived eruptions. Turbulent dissipation in long-lived slots helps maintain the ocean against freezing, maintains access by future Enceladus missions to ocean materials, and is plausibly the major energy source for tiger stripe activity.

  15. Effects of biomass reducing agent on magnetic properties and phase transformation of Baotou low-grade limonite during magnetizing-roasting.

    Directory of Open Access Journals (Sweden)

    Kai Zhang

    Full Text Available Biomass was used as reducing agent to roast the Baotou low-grade limonite in a high temperature vacuum atmosphere furnace. The effect of calcination temperature, time and ratio of reducing agent on the magnetic properties of calcined ore was studied by VSM. The phase and microstructure changes of limonite before and after calcination were analyzed by XRD and SEM. The results show that in the roasting process the phase transition process of the ferrous material in limonite is first dehydrated at high temperature to formα-Fe2O3, and then it is converted into Fe3O4 by the reduction of biomass. With the increase of calcination temperature, the magnetic properties of the calcined ore first increase and then decrease. When the temperature is higher than 650°C, Fe3O4 will become Fe2SiO4, resulting in reduced the magnetic material in calcined ore and the magnetic weakened. The best magnetization effect was obtained when the roasting temperature is 550°C, the percentage of biomass was 15% and the roasting time was 30min. The saturation magnetization can reach 60.13emu·g-1, the recovery of iron was 72% and the grade of iron was 58%.

  16. Magnetic precursor of the pressure-induced superconductivity in Fe-ladder compound

    Science.gov (United States)

    Chi, Songxue; Uwatoko, Yoshiya; Cao, Huibo; Hirata, Yasuyuki; Hashizume, Kazuki; Aoyama, Takuya; Ohgushi, Kenya

    The pressure effects on the antiferromagentic orders in iron-based ladder compounds CsFe2Se3 and BaFe2S3 have been studied using neutron diffraction. With identical crystal structure and similar magnetic structures, the two compounds exhibit highly contrasting magnetic behaviors under moderate external pressures. In CsFe2Se3 the ladders are brought much closer to each other by pressure, but the stripe-type magnetic order shows no observable change. In contrast, the stripe order in BaFe2S3, undergoes a quantum phase transition where an abrupt increase of N e xel temperature by more than 50% occurs at about 1 GPa, accompanied by a jump in the ordered moment. With its spin structure unchanged, BaFe2S3 enters an enhanced magnetic phase that bears the characteristics of an orbital selective Mott phase, which is the true neighbor of superconductivity emerging at higher pressures. Research at Oak Ridge National Laboratorys HFIR was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.This work was supported by JSPS KAKENHI Grant Number 16H04019.

  17. Neutron diffraction study of anomalous high-field magnetic phases in TmNi2B2C

    DEFF Research Database (Denmark)

    Toft, K.N.; Abrahamsen, A.B.; Eskildsen, M.R.

    2004-01-01

    We present a (B,T)-phase diagram of the magnetic superconductor TmNi2B2C obtained by neutron scattering. The measurements were performed in magnetic fields up to 6 T applied along the crystalline a axis. The observed phases are characterized by three ordering vectors, Q(F)=(0.094,0.094,0),Q(AI)=(0.......90Yb0.10)Ni2B2C the Q(F)-->Q(AI) phase transition is also observed but at a larger transition field compared to the undoped compound. In (Tm0.85Yb0.15)Ni2B2C the Q(F) phase persists up to at least 1.8 T. The magnetic correlation length of the Q(AI) phase in TmNi2B2C measured parallel and perpendicular.......483,0,0), and Q(AII)=(0.496,0,0), all with the magnetic moment along the c axis. In zero and low fields the Tm 4f-moments order in a long wavelength transverse spin density wave with Q=Q(F). The magnetic Q(AI) structure is stabilized by an applied field of 1 T and a transition to Q(AII) is observed at 4 T...

  18. The effect of phase constitution on the magnetic structure of nanophase NdFeB alloys observed by magnetic force microscopy

    Science.gov (United States)

    Al-Khafaji, M. A.; Rainforth, W. M.; Gibbs, M. R. J.; Davies, H. A.; Bishop, J. E. L.

    1998-09-01

    Magnetic force microscopy (MFM) has been employed to image the magnetic structure in nanocrystalline melt spun ribbon samples of NdFeB alloys of three markedly different and contrasting compositions: Low-Nd (Nd 9.5Fe 84.5B 6) containing Nd 2Fe 14B and α-Fe phases, stoichiometric (Nd 11.8Fe 82.3B 5.9), and high-Nd (Nd 18Fe 76B 6) containing Nd 2Fe 14B and Nd-rich phases. It was found that the magnetic domain length scale is significantly larger than the mean Nd 2Fe 14B grain size (˜35 nm) in each case, although small changes in force gradient occurred down to ˜20 nm. However, both the domain length scale and the tip-sample interaction `strength' were found to decrease with increasing Nd-content. An interpretation of these results in terms of the microstructure is given.

  19. Effect of Preparation Method on Phase Formation Process and Structural and Magnetic Properties of Mn2.5Ge Samples

    Directory of Open Access Journals (Sweden)

    R. Sobhani

    2016-12-01

    Full Text Available In this paper, the phase formation process of Mn2.5Ge samples, prepared by mechanical alloying of Mn and Ge metal powders and annealing, has been studied. Results showed that in the milled samples the stable phase is Mn11Ge8 compound with orthorhombic structure and Pnam space group. The value of saturation magnetization increases by increasing milling time from 0.2 up to 1.95 (Am2Kg-1. The remanece of the samples increases by increasing the milling time while the coercivity decreases. Annealing of 15-hour milled sample results in disappearance of Mn and Ge and the formation of new phases of Mn3Ge, Mn5Ge2, Mn5Ge3 and Mn2.3Ge. Mn3Ge is the main phase with Do22 tetragonal structure and I4/mmm space group which is stable and dominant. The enhancement of saturation magnetization in the annealed sample is related to the formation of three new magnetic phases and the increase of coercivity is due to the presence of Mn3Ge compound with tetragonal structure. Studies were replicated on samples made by arc melting method to compare the results and to investigate the effect of the preparation method on phase formation and structural and magnetic properties of the materials. In these samples the saturation value was in range of 0.2 up to 1.95 (Am2Kg-1 depending on preparation methods. Rietveld refinement shows that Mn2.3Ge sample prepared from arc melted under 620oC anealing is single phase. Magnetic analysis of this sample show a saturation magnetization of 5.252(Am2Kg-1 and 0.005 T coercive field.

  20. Bipartite stripe-like order of magneto-crystalline structure in Fe-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yazdani, A., E-mail: Yazdania@modares.ac.ir; Hesani, M.

    2017-01-01

    Emergence of superconductivity in the iron-based superconductor of “LaFeAsO” is a consequence of the characteristic behavior of antiferromagnetic structure at different triplet critical points. Here, we studied x{sub 2}{sup c} (highest concentration bound) = 0.5. A new second antiferromagnetic (AFM) structure was found that is developed for three different geometrical arrangements of O/H, resulting in three different antiferromagnetic structures at x{sub 2}{sup c} = 0.5. Both crystal and magnetic orderings are a consequence of the stripe-like ordering in the stripe configuration of “H” and “O”. Moreover, in our calculation a strong correlation was obtained between the magnetic and geometrical structures, resulting in the non-uniform magnetic moments of ∼1.30 μβ (AFM1-1) and ∼1.66 μβ (AFM1-3). This phenomenon results in the Jahn-Teller distortion, reflected in the non-uniformity of spin-induced distribution, in the range of 1.07 μβ close to “H” and 1.53 μβ close to “O”, in order to stabilize the ground state of the magneto-crystalline structure. This newly found second antiferromagnetic ordering behaves as the ground state with a lower cohesive energy, resulting in a lower magnetic moment. The effects are more pronounced in the displacement of atomic positions, reflecting in the repulsion of intra-layer La atoms from each other and the attraction of inter-layer Fe atoms toward each other, in direction to induce the anisotropy variable of η ≈ 0.78. - Highlights: • A new second antiferromagnetic structure was found. • Both crystal and magnetic orderings are a consequence of stripe-like ordering. • A strong correlation between the magnetic and geometrical structures was obtained. • Decrease of asymmetrical magnetic moment in direction to the decreased energy. • The effects are more pronounced on the displacement of topological atomic position.

  1. Curcurbita pepo subspecies delineates striped cucumber beetle (Acalymma vittatum) preference

    Science.gov (United States)

    Brzozowski, L; Leckie, B M; Gardner, J; Hoffmann, M P; Mazourek, M

    2016-01-01

    The striped cucumber beetle (Acalymma vittatum (F.)) is a destructive pest of cucurbit crops, and management could be improved by host plant resistance, especially in organic farming systems. However, despite the variation in striped cucumber beetle preference observed within the economically important species, Cucurbita pepo L., plant breeders and entomologists lacked a simple framework to classify and exploit these differences. This study used recent phylogenetic evidence and bioassays to organize striped cucumber beetle preference within C. pepo. Our results indicate preference contrasts between the two agriculturally relevant subspecies: C. pepo subsp. texana and C. pepo subsp. pepo. Plants of C. pepo subsp. pepo were more strongly preferred than C. pepo subsp. texana plants. This structure of beetle preference in C. pepo will allow plant breeders and entomologists to better focus research efforts on host plant non-preference to control striped cucumber beetles. PMID:27347423

  2. Neutron-diffraction studies of the nuclear magnetic phase diagram of copper

    DEFF Research Database (Denmark)

    Annila, A.J.; Clausen, Kurt Nørgaard; Oja, A.S.

    1992-01-01

    -field phase and the intermediate-field structure is of first order. The change from (0 2/3 2/3) at intermediate fields to (100) at zero field is associated with a large region (0.02 less-than-or-equal-to B less-than-or-equal-to 0.06 mT) of coexisting-(100) and (0 2/3 2/3)-type Bragg peaks, and can......We have studied the spontaneous antiferromagnetic (AF) order in the nuclear spin system of copper by use of neutron-diffraction experiments at nanokelvin temperatures. Copper is an ideal model system as a nearest-neighbor-dominated spin-3/2 fcc antiferromagnet. The phase diagram has been...... investigated by measuring the magnetic-field dependence of the (100) reflection, characteristic of a type-I AF structure, and of a Bragg peak at (0 2/3 2/3). The results suggest the presence of high-field (100) phases at 0.12 less-than-or-equal-to B less-than-or-equal-to B(c) almost-equal-to 0.26 mT, for B...

  3. Pathological changes associated with white striping in broiler breast muscles.

    Science.gov (United States)

    Kuttappan, V A; Shivaprasad, H L; Shaw, D P; Valentine, B A; Hargis, B M; Clark, F D; McKee, S R; Owens, C M

    2013-02-01

    White striping is a condition in broiler chickens characterized grossly by the occurrence of white striations, seen parallel to the direction of muscle fibers, on broiler breast fillets and thighs. Based on visual evaluation of the intensity of white striping, breast fillets can be categorized into normal (NORM), moderate (MOD), and severe (SEV) categories. This study was undertaken to evaluate the details of changes in histology as well as proximate composition occurring in the fillets with respect to the 3 degrees of white striping. In experiment 1, representative breast fillets for each degree of white striping (n = 20) were collected from 45-d-old broilers, approximately 2 h postmortem. From each fillet, 2 skeletal muscle samples were obtained and fixed in 10% neutral buffered formalin. To identify and differentiate the histological changes, slides were prepared and stained using hematoxylin and eosin, Masson's Trichrome, and Oil Red O stains. In experiment 2, samples with 3 degrees of white striping were collected from 57-d-old birds for conducting proximate analysis. Major histopathological changes observed in the MOD and SEV samples consisted of loss of cross striations, variability in fiber size, floccular/vacuolar degeneration and lysis of fibers, mild mineralization, occasional regeneration (nuclear rowing and multinucleated cells), mononuclear cell infiltration, lipidosis, and interstitial inflammation and fibrosis. Microscopic lesions were visually scored for degeneration and necrosis, fibrosis, and lipidosis. The scale used to score the samples ranged from 0 (normal) to 3 (severe). There was an increase (P white striping increased from NORM to SEV. The results from the histopathological study were supported by the findings from proximate analysis confirming that the fat and protein contents of muscle increased (P white striping increased. In conclusion, the histopathological changes occurring in white striping indicate a degenerative myopathy that

  4. Magnetism of a sigma-phase Fe{sub 60}V{sub 40} alloy: Magnetic susceptibilities and magnetocaloric effect studies

    Energy Technology Data Exchange (ETDEWEB)

    Bałanda, Maria [Institute of Nuclear Physics, Polish Academy of Science, PL-31-342 Kraków (Poland); Dubiel, Stanisław M., E-mail: Stanislaw.Dubiel@fis.agh.edu.pl [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, PL-30-059 Kraków (Poland); Pełka, Robert [Institute of Nuclear Physics, Polish Academy of Science, PL-31-342 Kraków (Poland)

    2017-06-15

    Highlights: • Sigma-phase Fe{sub 60}V{sub 40} alloy was studied by means of AC and DC magnetic susceptibilities. • Re-entrant character of the magnetism has been evidenced. • Curie temperature was found as ∼169 K and the spin-freezing temperature as ∼164 K. • Critical exponents β = 0.6, γ = 1.0 and Δ = 1.6 were determined. • Magnetocaloric effect was investigated. - Abstract: Magnetic properties of a sigma-phase Fe{sub 60}V{sub 40} intermetallic compound were studied by means of ac and dc magnetic susceptibility and magnetocaloric effect measurements. The compound is a soft magnet yet it was found to behave like a re-entrant spin-glass system. The magnetic ordering temperature was found to be T{sub C} ≈ 170 K, while the spin-freezing temperature was ∼164 K. Its relative shift per decade of ac frequency was 0.002, a value smaller than that typical of canonical spin-glasses. Magnetic entropy change, ΔS, in the vicinity of T{sub C} was determined for magnetic field, H, ranging between 5 and 50 kOe. Analysis of ΔS in terms of the power law yielded the critical exponent, n, vs. temperature with the minimum value of 0.75 at T{sub C}, while from the analysis of a relative shift of the maximum value of ΔS with the field a critical exponent Δ = 1.7 was obtained. Based on scaling laws relationships values of other two exponents viz. β = 0.6 and γ = 1 were determined.

  5. Ab initio study of energetics and magnetism of sigma phase in Co–Mo and Fe–Mo systems

    Czech Academy of Sciences Publication Activity Database

    Pavlů, Jana; Vřešťál, Jan; Šob, Mojmír

    2016-01-01

    Roč. 24, č. 2 (2016), č. článku Art. Number 025009. ISSN 0965-0393 R&D Projects: GA ČR GA14-15576S Institutional support: RVO:68081723 Keywords : intermetallics * magnetic properties * phase stability * thermodynamic properties * site occupancy * ab-initio calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.891, year: 2016

  6. Liquid carry-over in an injection moulded all-polymer chip system for immiscible phase magnetic bead-based solid-phase extraction

    DEFF Research Database (Denmark)

    Kistrup, Kasper; Sørensen, Karen Skotte; Wolff, Anders

    2014-01-01

    -binding buffer for nucleic acid extraction (0.1 (v/v)% Triton X-100 in 5 M guanidine hydrochloride). A linear relationship was found between the liquid carry-over and mass of magnetic beads used. Interestingly, similar average carry-overs of 1.74(8) nL/µg and 1.72(14) nL/µg were found for Milli-Q water and lysis...... phase filtration and features passive liquid filling and magnetic bead manipulation using an external magnet. In this work, we determine the system compatibility with various surfactants. Moreover, we quantify the volume of liquid co-transported with magnetic bead clusters from Milli-Q water or a lysis...

  7. Magnetic anisotropy and magnetic phase transitions in RFe.sub.5./sub.Al.sub.7./sub..

    Czech Academy of Sciences Publication Activity Database

    Gorbunov, Denis; Yasin, S.; Andreev, Alexander V.; Skourski, Y.; Mushnikov, N. V.; Rosenfeld, E.V.; Zherlitsyn, S.; Wosnitza, J.

    2015-01-01

    Roč. 383, Jun (2015), 208-214 ISSN 0304-8853 R&D Projects: GA ČR GAP204/12/0150 Grant - others:AVČR(CZ) M100101203 Institutional support: RVO:68378271 Keywords : rare-earth intermetallics * magnetic anisotropy * ferrimagnetism * high magnetic fields * spontaneous transition * field-induced transition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.357, year: 2015

  8. Nanocompositional Electron Microscopic Analysis and Role of Grain Boundary Phase of Isotropically Oriented Nd-Fe-B Magnets

    Directory of Open Access Journals (Sweden)

    Gregor A. Zickler

    2017-01-01

    Full Text Available Nanoanalytical TEM characterization in combination with finite element micromagnetic modelling clarifies the impact of the grain misalignment and grain boundary nanocomposition on the coercive field and gives guidelines how to improve coercivity in Nd-Fe-B based magnets. The nanoprobe electron energy loss spectroscopy measurements obtained an asymmetric composition profile of the Fe-content across the grain boundary phase in isotropically oriented melt-spun magnets and showed an enrichment of iron up to 60 at% in the Nd-containing grain boundaries close to Nd2Fe14B grain surfaces parallel to the c-axis and a reduced iron content up to 35% close to grain surfaces perpendicular to the c-axis. The numerical micromagnetic simulations on isotropically oriented magnets using realistic model structures from the TEM results reveal a complex magnetization reversal starting at the grain boundary phase and show that the coercive field increases compared to directly coupled grains with no grain boundary phase independently of the grain boundary thickness. This behaviour is contrary to the one in aligned anisotropic magnets, where the coercive field decreases compared to directly coupled grains with an increasing grain boundary thickness, if Js value is > 0.2 T, and the magnetization reversal and expansion of reversed magnetic domains primarily start as Bloch domain wall at grain boundaries at the prismatic planes parallel to the c-axis and secondly as Néel domain wall at the basal planes perpendicular to the c-axis. In summary our study shows an increase of coercive field in isotropically oriented Nd-Fe-B magnets for GB layer thickness > 5 nm and an average Js value of the GB layer < 0.8 T compared to the magnet with perfectly aligned grains.

  9. The magnetic and nematic phase diagram of Ba1-xSrxFe2-yNiyAs2

    Science.gov (United States)

    Gong, Dongliang; Li, Shiliang; SC8, National Lab for superconductivity, IOP, CAS Team

    The correlation between magnetic and nematic orders has been widely studied in iron-based superconductors. The magnetic and nematic phase transitions may be both first order as in SrFe2As2,o or both second order as in BaFe2-xNixAs2. Within spin-nematic scenario, it is possible for a system to establish the nematic phase as second order while keeping the magnetic transition first-ordered. Experimentally, it is rather hard to distinguish a second-order transition from a weakly first-order transition. Here we have systematically studied the nematic susceptibility and magnetic susceptibility in the iron-based superconductor Ba1-xSrxFe2-yNiyAs2 by elastoresistivity and magnetic susceptibility measurements, respectively. The evolutions of the nematic and magnetic transitions from first order to second order can be continuously tuned by the substitution of Sr by Ba. Our results give a phase diagram that is consistent with the spin-nematic theory. Chinese Academy of Sciences, Ministry of Science and Technology of China, e National Science Foundation of China, China Academy of Engineering Physics.

  10. Magnetocaloric as a sensitive tool to study magnetic phase in Ca4Mn3O10-δ

    Science.gov (United States)

    Mondal, Sampad; Modak, M.; Ray, M. K.; Mandal, Swapan K.; Sardar, M.; Banerjee, S.

    2018-02-01

    We report here magnetic properties of non-stoichiometric Ca4Mn3O10-δ . We have measured magnetization, electrical resistance, magnetoresistance, specific heat and thermo remanent magnetization (TRM) relaxation measurements. We find that at temperatures above 75 K the electrical transport can be explained in terms of activated hopping of magnetic polarons. These polarons are formed due to oxygen vacancy inducing Mn3+ sites. Below 50 K the polarons begins to strongly localize causing loss of moment and the electrical transport is governed by variable range hopping (VRH) conduction. The system shows glassy spin relaxation below 50 K, which presumably evolves into cluster spin glass at 12 K due to short range ordering of the canted moments. All these aspect could be well correlated with characteristics signature from magnetocaloric effect indicating magnetocaloric is a sensitive tool to study magnetic phase.

  11. Turbulent stress measurements with phase-contrast magnetic resonance through tilted slices

    Energy Technology Data Exchange (ETDEWEB)

    MacKenzie, Jordan; Soederberg, Daniel; Lundell, Fredrik [Linne FLOW Centre, KTH Mechanics, Stockholm (Sweden); Swerin, Agne [SP Technical Research Institute of Sweden-Chemistry, Materials and Surfaces, Stockholm (Sweden); KTH Royal Institute of Technology, Surface and Corrosion Science, Stockholm (Sweden)

    2017-05-15

    Aiming at turbulent measurements in opaque suspensions, a simplistic methodology for measuring the turbulent stresses with phase-contrast magnetic resonance velocimetry is described. The method relies on flow-compensated and flow-encoding protocols with the flow encoding gradient normal to the slice. The experimental data is compared with direct numerical simulations (DNS), both directly but also, more importantly, after spatial averaging of the DNS data that resembles the measurement and data treatment of the experimental data. The results show that the most important MRI data (streamwise velocity, streamwise variance and Reynolds shear stress) is reliable up to at least anti r = 0.75 without any correction, paving the way for dearly needed turbulence and stress measurements in opaque suspensions. (orig.)

  12. Development Of Radioimmunoassay For Prolactin HORMONE Using Solid Phase Magnetic Particles

    International Nuclear Information System (INIS)

    SHAFIK, H.M.; MEHANY, N.L.

    2009-01-01

    The preparation and development of primary reagents of prolactin (PRL) radioimmunoassay (RIA) technique using solid phase magnetic particles with low cost is considered to be the main objective of the present study. The production of polyclonal antibodies was undertaken by immunizing four female New-Zealand rabbits through primary injection and four booster doses subcutaneously. The preparation of 125 I-prolactin radiotracer was carried out using chloramine-T. The preparation of standard prolactin was undertaken by preparing stock standard solution of prolactin and diluted with assay buffer. Activation and coupling of low magnetizable particles with the purified anti-PRL was carried out. Optimization and validation of the assay were carried out. The results obtained provide a highly sensitive, specific and accurate RIA system of PRL. In conclusion, this assay could be used in diagnosis of galactorrhea, prolactinoma, visual impairment and diagnosis of infertility in males and females.

  13. A comprehensive model of the quiet-time, near-Earth magnetic field: phase 3

    DEFF Research Database (Denmark)

    Sabaka, T.J.; Olsen, Nils; Langel, R.A.

    2002-01-01

    The near-Earth magnetic field is caused by sources in the Earth's core, ionosphere, magnetosphere, lithosphere and from coupling currents between the ionosphere and the magnetosphere, and between hemispheres. Traditionally, the main field (low degree internal field) and magnetospheric field have......, and includes an accounting for main field influences on the magnetosphere, main field and solar activity influences on the ionosphere, seasonal influences on the coupling currents, a priori characterization of the influence of the ionosphere and the magnetosphere on Earth-induced fields, and an explicit...... been modelled simultaneously, with fields from other sources being modelled separately. Such a scheme, however, can introduce spurious features, especially when the spatial and temporal scales of the fields overlap. A new model, designated CM3 (Comprehensive Model: phase 3), is the third in a series...

  14. Applying Closing Phase-Angle Control Technique in Bounce Reduction of AC Permanent Magnet Contactor

    Directory of Open Access Journals (Sweden)

    Chieh-Tsung Chi

    2009-01-01

    Full Text Available A new low-cost electronic control circuit actuator is proposed for minimizing the bouncing times of an AC permanent magnet (PM contactor after two contacts closing. The proposed new actuator overcomes the bouncing problem of an uncontrollable restrictions imposed by previously conventional AC electromagnetic (EM contactor based on the minimization of kinetic energy prior to two contacts impact. By choosing the closing phase angle of coil voltage on purpose, the bouncing problems of the movable contact during the closing process are then overcome. The using life of contacts is then prolonged and their operating reliability is improved as well. In order to validate the feasibility and effectiveness of the proposed method here, several simulation and experimental procedures were performed on a prototype of AC PM contactor in the laboratory. Testing results actually showed that bouncing problem of contactor's contacts during the closing process was to be controlled by using the proposed technology.

  15. Femtosecond single electron bunch generation by rotating longitudinal bunch phase space in magnetic field

    International Nuclear Information System (INIS)

    Yang, J.; Kondoh, T.; Kan, K.; Kozawa, T.; Yoshida, Y.; Tagawa, S.

    2006-01-01

    A femtosecond (fs) electron bunching was observed in a photoinjector with a magnetic compressor by rotating the bunch in longitudinal phase space. The bunch length was obtained by measuring Cherenkov radiation of the electron beam with a femtosecond streak camera technique. A single electron bunch with rms bunch length of 98 fs was observed for a 32 MeV electron beam at a charge of 0.17 nC. The relative energy spread and the normalized transverse emittance of the electron beam were 0.2% and 3.8 mm-mrad, respectively. The effect of space charge on the bunch compression was investigated experimentally for charges from 0.17 to 1.25 nC. The dependences of the relative energy spread and the normalized beam transverse emittance on the bunch charge were measured

  16. Magnets

    International Nuclear Information System (INIS)

    Young, I.R.

    1984-01-01

    A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires with one end of each wire held in a non-magnetic spacer, the other ends of the wires being brought to a pinch, and connected to a magnetic core. The wires may be embedded in a synthetic resin and the magnetisation and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece. (author)

  17. Structural and magnetic phase diagram of CrAs and its relationship with pressure-induced superconductivity

    Science.gov (United States)

    Shen, Yao; Wang, Qisi; Hao, Yiqing; Pan, Bingying; Feng, Yu; Huang, Qingzhen; Harriger, L. W.; Leao, J. B.; Zhao, Yang; Chisnell, R. M.; Lynn, J. W.; Cao, Huibo; Hu, Jiangping; Zhao, Jun

    2016-02-01

    We use neutron diffraction to study the structure and magnetic phase diagram of the newly discovered pressure-induced superconductor CrAs. Unlike most magnetic unconventional superconductors where the magnetic moment direction barely changes upon doping, here we show that CrAs exhibits a spin reorientation from the a b plane to the a c plane, along with an abrupt drop of the magnetic propagation vector at a critical pressure (Pc≈0.6 GPa). This magnetic phase transition, accompanied by a lattice anomaly, coincides with the emergence of bulk superconductivity. With further increasing pressure, the magnetic order completely disappears near the optimal Tc regime (P ≈0.94 GPa). Moreover, the Cr magnetic moments tend to be aligned antiparallel between nearest neighbors with increasing pressure toward the optimal superconductivity regime. Our findings suggest that the noncollinear helimagnetic order is strongly coupled to structural and electronic degrees of freedom, and that the antiferromagnetic correlations between nearest neighbors might be essential for superconductivity.

  18. Magnetization of exsolution intergrowths of hematite and ilmenite: Mineral chemistry, phase relations, and magnetic properties of hemo-ilmenite ores with micron- to nanometer-scale lamellae from Allard Lake, Quebec

    DEFF Research Database (Denmark)

    McEnroe, S.A.; Robinson, P.; Langenhorst, F.

    2007-01-01

    . To understand the magnetism and evolution of the exsolution lamellae, the microstructures and nanostructures were studied using scanning electron microscopy and transmission electron microscopy (TEM), phase chemistry, and relations between mineral chemistry and the hematite-ilmenite phase diagram. Cycles...

  19. Quantum phase transitions and local magnetism in Mott insulators: A local probe investigation using muons, neutrons, and photons

    Science.gov (United States)

    Frandsen, Benjamin A.

    Mott insulators are materials in which strong correlations among the electrons induce an unconventional insulating state. Rich interplay between the structural, magnetic, and electronic degrees of freedom resulting from the electron correlation can lead to unusual complexity of Mott materials on the atomic scale, such as microscopically heterogeneous phases or local structural correlations that deviate significantly from the average structure. Such behavior must be studied by suitable experimental techniques, i.e. "local probes", that are sensitive to this local behavior rather than just the bulk, average properties. In this thesis, I will present results from our studies of multiple families of Mott insulators using two such local probes: muon spin relaxation (muSR), a probe of local magnetism; and pair distribution function (PDF) analysis of x-ray and neutron total scattering, a probe of local atomic structure. In addition, I will present the development of magnetic pair distribution function analysis, a novel method for studying local magnetic correlations that is highly complementary to the muSR and atomic PDF techniques. We used muSR to study the phase transition from Mott insulator to metal in two archetypal Mott insulating systems: RENiO3 (RE = rare earth element) and V2O3. In both of these systems, the Mott insulating state can be suppressed by tuning a nonthermal parameter, resulting in a "quantum" phase transition at zero temperature from the Mott insulating state to a metallic state. In RENiO3, this occurs through variation of the rare-earth element in the chemical composition; in V 2O3, through the application of hydrostatic pressure. Our results show that the metallic and Mott insulating states unexpectedly coexist in phase-separated regions across a large portion of parameter space near the Mott quantum phase transition and that the magnitude of the ordered antiferromagnetic moment remains constant across the phase diagram until it is abruptly

  20. Reconstruction of early phase deformations by integrated magnetic and mesotectonic data evaluation

    Science.gov (United States)

    Sipos, András A.; Márton, Emő; Fodor, László

    2018-02-01

    Markers of brittle faulting are widely used for recovering past deformation phases. Rocks often have oriented magnetic fabrics, which can be interpreted as connected to ductile deformation before cementation of the sediment. This paper reports a novel statistical procedure for simultaneous evaluation of AMS (Anisotropy of Magnetic Susceptibility) and fault-slip data. The new method analyzes the AMS data, without linearization techniques, so that weak AMS lineation and rotational AMS can be assessed that are beyond the scope of classical methods. This idea is extended to the evaluation of fault-slip data. While the traditional assumptions of stress inversion are not rejected, the method recovers the stress field via statistical hypothesis testing. In addition it provides statistical information needed for the combined evaluation of the AMS and the mesotectonic (0.1 to 10 m) data. In the combined evaluation a statistical test is carried out that helps to decide if the AMS lineation and the mesotectonic markers (in case of repeated deformation of the oldest set of markers) were formed in the same or different deformation phases. If this condition is met, the combined evaluation can improve the precision of the reconstruction. When the two data sets do not have a common solution for the direction of the extension, the deformational origin of the AMS is questionable. In this case the orientation of the stress field responsible for the AMS lineation might be different from that which caused the brittle deformation. Although most of the examples demonstrate the reconstruction of weak deformations in sediments, the new method is readily applicable to investigate the ductile-brittle transition of any rock formation as long as AMS and fault-slip data are available.

  1. Chandra Phase-resolved Spectroscopy of the High Magnetic Field Pulsar B1509−58

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Chin-Ping; Ng, C.-Y. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Takata, J. [School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei (China); Shannon, R. M. [International Centre for Radio Astronomy Research, Curtin University, Bentley, WA 6102 (Australia); Johnston, S., E-mail: cphu@hku.hk, E-mail: ncy@bohr.physics.hku.hk [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Box 76, Epping, NSW 1710 (Australia)

    2017-04-01

    We report on a timing and spectral analysis of the young, high magnetic field rotation-powered pulsar (RPP) B1509−58 using Chandra continuous-clocking mode observation. The pulsar’s X-ray light curve can be fit by the two Gaussian components and the pulsed fraction shows moderate energy dependence over the Chandra band. The pulsed X-ray spectrum is well described by a power law with a photon index 1.16(4), which is harder than the values measured with RXTE /PCA and NuSTAR . This result supports the log-parabolic model for the broadband X-ray spectrum. With the unprecedented angular resolution of Chandra , we clearly identified off-pulse X-ray emission from the pulsar, and its spectrum is best fit by a power law plus blackbody model. The latter component has a temperature of ∼0.14 keV with a bolometric luminosity comparable to the luminosities of other young and high magnetic field RPPs, and it lies between the temperature of magnetars and typical RPPs. In addition, we found that the nonthermal X-ray emission of PSR B1509−58 is significantly softer in the off-pulse phase than in the pulsed phase, with the photon index varying between 1.0 and 1.8 and anticorrelated with the flux. This is similar to the behavior of three other young pulsars. We interpreted it as different contributions of pair-creation processes at different altitudes from the neutron star surface according to the outer-gap model.

  2. Automated solid-phase subcloning based on beads brought into proximity by magnetic force.

    Directory of Open Access Journals (Sweden)

    Elton P Hudson

    Full Text Available In the fields of proteomics, metabolic engineering and synthetic biology there is a need for high-throughput and reliable cloning methods to facilitate construction of expression vectors and genetic pathways. Here, we describe a new approach for solid-phase cloning in which both the vector and the gene are immobilized to separate paramagnetic beads and brought into proximity by magnetic force. Ligation events were directly evaluated using fluorescent-based microscopy and flow cytometry. The highest ligation efficiencies were obtained when gene- and vector-coated beads were brought into close contact by application of a magnet during the ligation step. An automated procedure was developed using a laboratory workstation to transfer genes into various expression vectors and more than 95% correct clones were obtained in a number of various applications. The method presented here is suitable for efficient subcloning in an automated manner to rapidly generate a large number of gene constructs in various vectors intended for high throughput applications.

  3. Magnetic phase transitions in the chiral helimagnet Cr1/3NbS2

    Science.gov (United States)

    Ghimire, Nirmal; McGuire, Michael; Sales, Brian; Debeer-Schmitt, Lisa; Cao, Huibo; Chakoumakos, Bryan; Aczel, Adam; Sipos, Balazs; Tang, Siwei; Yiu, Yuen; Yan, Jiaqiang; Nagler, Stephen; Mandrus, David

    2013-03-01

    Cr1/3NbS2 is a long period chiral helimagnet crystallizing in the noncentrosymmetric, hexagonal space group P6322. Helimagnetic ordering along the c-axis is attributed to the competition between the symmetric exchange interaction, favoring parallel moments, and the anti-symmetric Dzyaloshinsky-Moriya interaction, favoring perpendicular moments. Recently, the ground state helical ordering is found to be destabilized by a magnetic field applied perpendicular to c, forming a chiral soliton lattice phase, and, above a critical field, a commensurate ferromagnetic state. Thermal and transport properties also show interesting behaviors in the vicinity of the transition temperature. Here we present magnetic, thermal and transport properties of Cr1/3NbS2 measured on single crystals, along with recent results from neutron scattering experiments conducted on the four circle single crystal diffractometer and general purpose SANS at the High Flux Isotope Reactor, ORNL. Research supported by DOE office of Science, Division of Materials Science and Engineering and Scientific User Facilities Division. Research at ORNL's HFIR sponsored by the Scientific User Facilities Division.

  4. Study by nuclear magnetic resonance of deuterium (NMR 2H) of lyotropic phases initiators of 'micro emulsion' phases

    International Nuclear Information System (INIS)

    Latie, Laurence

    1988-01-01

    After a brief presentation of the pseudo-phases mode as an introduction to the lamellar phase of the ternary system (surfactant-co-surfactant-water) studied in this research thesis, and an explanation of the choice of deuterium nuclear magnetic resonance to perform this study, the author reports a study which aimed at a better knowledge of the membrane pseudo-phase structure. After a brief presentation of the different phases met in ternary systems, the author recalls the principles of deuterium NMR, and addresses the theory of exchange and its application to the studied systems. She presents experimental techniques, and presents, interprets and discusses the obtained results. She shows that NMR can be used to obtain a phase diagram, and to determine the exact structure of a membrane as well as its characterising constants [fr

  5. Novel High Temperature Magnetic Bearings for Space Vehicle Systems, Phase II

    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...

  6. Novel High Temperature Magnetic Bearings for Space Vehicle Systems, Phase I

    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...

  7. Inhomogeneous LOFF phase revisited for surface superconductivity

    Science.gov (United States)

    Barzykin, Victor; Gor'kov, Lev P.

    2003-03-01

    We consider 2D surface superconductivity in high magnetic fields parallel to the surface. We demonstrate that the spin-orbit interaction at the surface changes the properties of the inhomogeneous superconducting Larkin-Ovchinnikov-Fulde-Ferrell state that develops above fields given by the paramagnetic criterion. Strong spin-orbit interaction significantly broadens the range of existence of the LOFF phase, which takes the form of periodic superconducting stripes running along the field direction on the surface, leading to the anisotropy of its properties. We also discuss this problem for the d-wave pairing to indicate the possibility of a re-orientation transition as the magnetic field direction is rotated in the plane parallel to the surface. Our results provide a tool for studying surface superconductivity This work was supported in part by NHMFL through the NSF Cooperative agreement No. DMR-9521035 and the State of Florida, in part (VB) by the University of Tennessee.

  8. Dynamic phase diagrams of the Ising metamagnet in an oscillating magnetic field within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2010-07-12

    Dynamic aspects of a two-sublattice Ising metamagnet on honeycomb, square and hexagonal lattices under the presence of a time-dependent oscillating external magnetic field are studied by using the effective-field theory with correlations. The set of effective-field dynamic equations is derived by employing Glauber transition rates. The phases in the system are obtained by solving these dynamic equations. The thermal behavior of the dynamic staggered magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. The phase diagrams are constructed in two different planes, and exhibit dynamic tricritical behavior, which strongly depends on interaction parameters. In order to investigate the spin correlation effect on the dynamic phase diagrams of the system, the results are also given within the framework of the dynamic mean-field approximation.

  9. Dynamic phase diagrams of the Ising metamagnet in an oscillating magnetic field within the effective-field theory

    International Nuclear Information System (INIS)

    Deviren, Bayram; Keskin, Mustafa

    2010-01-01

    Dynamic aspects of a two-sublattice Ising metamagnet on honeycomb, square and hexagonal lattices under the presence of a time-dependent oscillating external magnetic field are studied by using the effective-field theory with correlations. The set of effective-field dynamic equations is derived by employing Glauber transition rates. The phases in the system are obtained by solving these dynamic equations. The thermal behavior of the dynamic staggered magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. The phase diagrams are constructed in two different planes, and exhibit dynamic tricritical behavior, which strongly depends on interaction parameters. In order to investigate the spin correlation effect on the dynamic phase diagrams of the system, the results are also given within the framework of the dynamic mean-field approximation.

  10. Preparation of cold ions in strong magnetic field and its application to gas-phase NMR spectroscopy

    International Nuclear Information System (INIS)

    Fuke, K.; Ohshima, Y.; Tona, M.

    2015-01-01

    Nuclear Magnetic Resonance (NMR) technique is widely used as a powerful tool to study the physical and chemical properties of materials. However, this technique is limited to the materials in condensed phases. To extend this technique to the gas-phase molecular ions, we are developing a gas-phase NMR apparatus. In this note, we describe the basic principle of the NMR detection for molecular ions in the gas phase based on a Stern-Gerlach type experiment in a Penning trap and outline the apparatus under development. We also present the experimental procedures and the results on the formation and the manipulation of cold ions under a strong magnetic field, which are the key techniques to detect the NMR by the present method

  11. Magnetic field dependence of Griffith phase and magnetocaloric effect in Ca0.85Dy0.15MnO3

    Science.gov (United States)

    Nag, Ripan; Sarkar, Bidyut; Pal, Sudipta

    2018-03-01

    Temperature and Magnetic field dependent magnetization properties of electron doped polycrystalline sample Ca0.85Dy0.15MnO3 (CDMO) prepared by solid state reaction method have been studied. The sample undergoes ferromagnetic to paramagnetic phase transition at about 111k. From the study of magnetic properties in terms of Arrot plots it is observed that the phase transition is of 2nd order. The Griffith phase behavior of the sample is suppressed with the increase of the applied magnetic field strength H. We have estimated the magnetic entropy change from experimental magnetization and temperature data. For a magnetic field change of 8000 Oe, the maximum value of magnetic entropy change arrives at a value of 1.126 J-kg-1 k-1 in this magnetocaloric material.

  12. Preclinical 4D-flow magnetic resonance phase contrast imaging of the murine aortic arch.

    Directory of Open Access Journals (Sweden)

    Moritz Braig

    Full Text Available Cardiovascular diseases remain the number one death cause worldwide. Preclinical 4D flow phase contrast magnetic resonance imaging can provide substantial insights in the analysis of aortic pathophysiologies in various animal models. These insights may allow a better understanding of pathophysiologies, therapy monitoring, and can possibly be translated to humans. This study provides a framework to acquire the velocity field within the aortic arch. It analyses important flow values at different locations within the aortic arch. Imaging parameters with high temporal and spatial resolution are provided, that still allow combining this time-consuming method with other necessary imaging-protocols.A new setup was established where a prospectively gated 4D phase contrast sequence is combined with a highly sensitive cryogenic coil on a preclinical magnetic resonance scanner. The sequence was redesigned to maintain a close to steady state condition of the longitudinal magnetization and hence to overcome steady state artifacts. Imaging parameters were optimized to provide high spatial and temporal resolution. Pathline visualizations were generated from the acquired velocity data in order to display complex flow patterns.Our setup allows data acquisition with at least two times the rate than that of previous publications based on Cartesian encoding, at an improved image quality. The "steady state" sequence reduces observed artifacts and provides uniform image intensity over the heart cycle. This made possible quantification of blood speed and wall shear stress (WSS within the aorta and its branches. The highest velocities were observed in the ascending aorta with 137.5 ± 8 cm/s. Peak velocity values in the Brachiocephalic trunk were 57 ± 12 cm/s. Quantification showed that the peak flow occurs around 20 ms post R-wave in the ascending aorta. The highest mean axial wall shear stress was observed in the analysis plane between the left common carotid artery

  13. Increasing stripe-type fluctuations in A Fe2As2 (A =K , Rb, Cs) superconductors probed by 75As NMR spectroscopy

    Science.gov (United States)

    Zhang, Z. T.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Khim, S.; Gass, S.; Wolter, A. U. B.; Wurmehl, S.; Grafe, H.-J.; Kühne, H.

    2018-03-01

    We report 75As nuclear magnetic resonance measurements on single crystals of RbFe2As2 and CsFe2As2 . Taking previously reported results for KFe2As2 into account, we find that the anisotropic electronic correlations evolve towards a magnetic instability in the A Fe2As2 series (with A =K , Rb, Cs). Upon isovalent substitution with larger alkali-metal ions, a drastic enhancement of the anisotropic nuclear spin-lattice relaxation rate and decreasing Knight shift reveal the formation of pronounced spin fluctuations with stripe-type modulation. Furthermore, a decreasing power-law exponent of the nuclear spin-lattice relaxation rate (1/T1)H ∥a b, probing the in-plane spin fluctuations, evidences an emergent deviation from Fermi-liquid behavior. All these findings clearly indicate that the expansion of the lattice in the A Fe2As2 series tunes the electronic correlations towards a quantum critical point at the transition to a yet unobserved ordered phase.

  14. Revealing the nature of magnetic phases in the semi-Heusler alloy Cu{sub 0.85}Ni{sub 0.15}MnSb

    Energy Technology Data Exchange (ETDEWEB)

    Halder, Madhumita, E-mail: mhalder@phy.iitb.ac.in [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Suresh, K.G., E-mail: suresh@phy.iitb.ac.in [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Mukadam, M.D. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Yusuf, S.M., E-mail: smyusuf@barc.gov.in [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2015-01-15

    We report the magnetic, magnetocaloric, and magnetotransport properties of the semi-Heusler alloy Cu{sub 0.85}Ni{sub 0.15}MnSb, which exhibits coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) phases. A broad magnetic phase transition is evident from the temperature variations of magnetization, heat capacity, and isothermal magnetic entropy change. This is due to the presence of both AFM and FM phases at low temperatures. The variation of electrical resistivity with temperature shows three distinct regions of magnetic phases. The magnetoresistance (MR) results also show the presence of AFM and FM phases at temperatures below 45 K, and a FM phase at temperature above 45 K. Though there is no signature of a spin-glass state at low temperatures, various results point towards the presence of short-range magnetic correlations at low temperatures. - Highlights: • Magnetic, magnetocaloric, and magnetotransport properties of Cu{sub 0.85}Ni{sub 0.15}MnSb have been investigated. • Coexistence of antiferromagnetic and ferromagnetic phases at low temperature. • Resistivity and magnetoresistance with temperature shows three distinct regions of magnetic phases. • Presence of short-range magnetic correlations at low temperatures.

  15. Using magnetic resonance phase-contrast velocity mapping for diagnosing pelvic congestion syndrome.

    Science.gov (United States)

    Meneses, L Q; Uribe, S; Tejos, C; Andía, M E; Fava, M; Irarrazaval, P

    2011-06-01

    To evaluate phase-contrast velocity mapping (PCVM) as a diagnostic tool for pelvic congestion syndrome and comparing this approach with direct venography. We prospectively include nine women with clinical suspicion of pelvic congestion syndrome during a six-month period. All patients underwent a magnetic resonance phase-contrast scan before a direct venography. We considered a case of pelvic congestion syndrome when the PCVM showed a retrograde or slow (less than 5 cm/second) flow in any gonadal vein. This criterion was compared with the standard diagnostic criterion observed from a direct venography. Using direct venography we found 14 abnormal veins and all of them were correctly identified by the PCVM. The other four veins were found to be normal by the direct venography. However, two of them (the same patient) were abnormal in the PCVM, even though this patient had the classical symptoms of pelvic congestion syndrome. PCVM is a useful tool for diagnosing pelvic contrast syndrome and can avoid invasive procedures such as direct venography.

  16. High sensitivity pressure transducer based on the phase characteristics of GMI magnetic sensors

    Science.gov (United States)

    Benavides, L. S.; Costa Silva, E.; Costa Monteiro, E.; Hall Barbosa, C. R.

    2018-03-01

    This paper presents a new configuration for a GMI pressure transducer based on the reading of the phase characteristics of GMI sensor, intended for biomedical applications. The development process of this new class of magnetic field transducers is discussed, beginning with the definition of the ideal conditioning of the GMI sensor elements (dc level and frequency of the excitation current and sample length) and continuing with computational simulations of the full electronic circuit performed using the experimental data obtained from measured GMI curves, and have shown that the improvement in the sensitivity of GMI magnetometers is larger when phase-based transducers are used instead of magnitude-based transducers. Parameters of interest of the developed prototype are thoroughly analyzed, such as: sensitivity, linearity and frequency response. Also, the spectral noise density of the developed pressure transducer is evaluated and its resolution in the passband is estimated. A low-cost GMI pressure transducer was developed, presenting high resolution, high sensitivity and a frequency bandwidth compatible to the desired biomedical applications.

  17. Cation distribution, magnetic properties and cubic-perovskite phase transition in bismuth-doped nickel ferrite

    Science.gov (United States)

    Gore, Shyam K.; Jadhav, Santosh S.; Tumberphale, Umakant B.; Shaikh, Shoyeb M.; Naushad, Mu; Mane, Rajaram S.

    2017-12-01

    The phase transition of bismuth-substituted nickel ferrite, synthesized by using a simple sol-gel autocombustion method, from cubic to perovskite is confirmed from the X-ray diffraction spectrums. The changes in isomer shift, hyperfine field and cation distribution are obtained from the Mossbauer spectroscopy analysis. The cation distribution demonstrates Ni2+ cations occupy tetrahedral sites, while Fe3+ and Bi3+ occupy both tetrahedral as well as octahedral sites. For higher concentrations of bismuth, saturation magnetization is increased whereas, coercivity is decreased which is related to phase change. The variations of dielectric constant, tangent loss and conductivity (ac) with frequency (10 Hz-5 MHz) have been explored with Bi3+-doping i.e. 'x'. According to Maxwell-Wagener model, there is an involvement of electron hopping kinetics as both dielectric constant and tangent loss are decreased with increasing frequency. Increase of conductivity with frequency (measured at room temperature, 27 °C) is attributed to increase of number of carriers and mobility.

  18. Magnetism of insulator phase in SrRu1-x Mn x O3 (0.4≤x≤0.6)

    International Nuclear Information System (INIS)

    Kawanaka, H.; Satoh, C.; Yokoyama, M.; Kitazawa, H.; Suzuki, O.; Kido, G.; Bando, H.; Nishihara, Y.

    2007-01-01

    Temperature dependence of magnetization was measured in the insulator phase of SrRu 1- x Mn x O 3 (0.4≤x≤0.6) at magnetic fields up to 15 T. For the sample with x=0.6, the peak of the magnetization changes from 210 to 250 K with increasing magnetic field up to 5 T and slightly decreases above it. The paramagnetic Curie-Weiss temperature is positive (180 K). The anti-ferromagnetic Neel temperature obtained from the neutron diffraction experiment agrees with the peak temperature measured in high magnetic fields. Discussion of the magnetization peak in high and low magnetic fields is given

  19. Small Hypervascular Hepatocellular Carcinoma: Limited Value of Portal and Delayed Phases on Dynamic Magnetic Resonance Imaging

    International Nuclear Information System (INIS)

    Yu, J.S.; Lee, J.H.; Chung, J.J.; Kim, J.H.; Kim, K.W.

    2008-01-01

    Background: Characterization of small nodules in the cirrhotic liver is always challenging in clinical practice. In the differential diagnosis of small hypervascular lesions, it has been reported that portal venous or delayed hypointensity is a useful sign to characterize hepatocellular carcinomas (HCCs) during dynamic magnetic resonance (MR) imaging. However, few studies have assessed the diagnostic value of this sign. Purpose: To determine the diagnostic value of portal-phase (PP) and delayed-phase (DP) images for the diagnosis of small hypervascular HCCs during intravenous (IV) contrast-enhanced dynamic MR imaging of cirrhotic liver. Material and Methods: A total of 69 small (6-20 mm) hypervascular HCCs in 53 cirrhotic patients were subjected to a retrospective analysis of the signal intensities (hypo-, iso-, or hyperintense) and rim enhancement on PP and 5-min DP images from three-phased dynamic MR imaging according to the pre-contrast T1- and T2-weighted imaging features. After exclusion of 33 subcapsular wedge-shaped pseudolesions and three hemangiomas by typical imaging features, 74 centrally located small hypervascular benign or pseudolesions were used as a control group for comparative analyses. Results: The sensitivities of PP hypointensity, DP hypointensity, and rim enhancement in the diagnosis were 11%, 29%, and 18%, respectively, for 6-10-mm hypervascular HCCs, and 42%, 63%, and 58%, respectively, for 16-20-mm lesions. After exclusion of the 48 lesions showing T2-weighted hyperintensity (HCCs, n=39; benign lesions, n=9), the overall sensitivity for diagnosis of small hypervascular HCCs decreased (8.3%, 25.0%, and 8.3%, respectively). Conclusion: Although DP provides a better sensitivity than PP, both PP and DP have very limited diagnostic value for diagnosis of small hypervascular HCCs during dynamic MR imaging of the cirrhotic liver

  20. Agenesis of the horizontal segment of the left portal vein demonstrated by magnetic resonance imaging including phase-contrast magnetic resonance venography

    International Nuclear Information System (INIS)

    Chevallier, P.; Oddo, F.; Diaine, B.; Padovani, B.; Baldini, E.; Peten, E.P.

    2000-01-01

    Two cases of agenesis of the horizontal segment of the left portal vein are reported. This very rare vascular anomaly probably corresponds to an embryological variation rather than to an obstruction of the left portal vein. In almost all cases liver ultrasonography is sufficient for identifying such vascular abnormalities. It shows a large aberrant vessel emerging from a right anterior segmental portal branch and running transversely in the quadrate lobe towards the teres ligamentum from which the portal supply to the left lobe arises. It is important to be able to recognize the magnetic resonance imaging features of this vascular variation, as magnetic resonance imaging may be the initial imaging study, and ultrasound may be technically challenging. To our knowledge, we present the first description of these features, including an enhanced gradient-echo T1-weighted sequence, a turbo spin-echo T2-weighted sequence with fat saturation, and a three-dimensional phase-contrast magnetic resonance portography. (orig.)

  1. Properties and geoeffectiveness of magnetic clouds in the rising, maximum and early declining phases of solar cycle 23

    Directory of Open Access Journals (Sweden)

    K. E. J. Huttunen

    2005-02-01

    Full Text Available The magnetic structure and geomagnetic response of 73 magnetic clouds (MC observed by the WIND and ACE satellites in solar cycle 23 are examined. The results have been compared with the surveys from the previous solar cycles. The preselected candidate MC events were investigated using the minimum variance analysis to determine if they have a flux-rope structure and to obtain the estimation for the axial orientation (θC, φC. Depending on the calculated inclination relative to the ecliptic we divided MCs into "bipolar" (θC<45° and "unipolar" (θC>45°. The number of observed MCs was largest in the early rising phase, although the halo CME rate was still low. It is likely that near solar maximum we did not identify all MCs at 1AU, as they were crossed far from the axis or they had interacted strongly with the ambient solar wind or with other CMEs. The occurrence rate of MCs at 1AU is also modified by the migration of the filament sites on the Sun towards the poles near solar maximum and by the deflection of CMEs towards the equator due to the fast solar wind flow from large polar coronal holes near solar minimum. In the rising phase nearly all bipolar MCs were associated with the rotation of the magnetic field from the south at the leading edge to the north at the trailing edge. The results for solar cycles 21-22 showed that the direction of the magnetic field in the leading portion of the MC starts to reverse at solar maximum. At solar maximum and in the declining phase (2000-2003 we observed several MCs with the rotation from the north to the south. We observed unipolar (i.e. highly inclined MCs frequently during the whole investigated period. For solar cycles 21-22 the majority of MCs identified in the rising phase were bipolar while in the declining phase most MCs were unipolar. The geomagnetic response of a given MC depends greatly on its magnetic structure and the orientation of the sheath fields. For each event we distinguished the

  2. MAGNET

    CERN Multimedia

    B. Curé

    The first phase of the commissioning ended in August by a triggered fast dump at 3T. All parameters were nominal, and the temperature recovery down to 4.5K was carried out in two days by the cryogenics. In September, series of ramps were achieved up to 3 and finally 3.8T, while checking thoroughly the detectors in the forward region, measuring any movement of and around the HF. After the incident of the LHC accelerator on September 19th, corrective actions could be undertaken in the forward region. When all these displacements were fully characterized and repetitive, with no sign of increments in displacement at each field ramp, it was possible to start the CRAFT, Cosmic Run at Four Tesla (which was in fact at 3.8T). The magnet was ramped up to 18.16kA and the 3 week run went smoothly, with only 4 interruptions: due to the VIP visits on 21st October during the LHC inauguration day; a water leak on the cooling demineralized water circuit, about 1 l/min, that triggered a stop of the cooling pumps, and resulte...

  3. Phase and microstructural analysis of hot rolled FeNi42 sheet, its response in magnetic and mechanical properties

    Czech Academy of Sciences Publication Activity Database

    Jirásková, Yvonna; Buršík, Jiří; Tuček, J.

    2011-01-01

    Roč. 82, č. 8 (2011), s. 898-904 ISSN 1611-3683 Institutional research plan: CEZ:AV0Z20410507 Keywords : electron microscopy * hardness * interface * Fe-Ni steel * phase transformation * thermomechanical processing Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.733, year: 2011

  4. Millijansky radio variability in SDSS stripe 82

    Energy Technology Data Exchange (ETDEWEB)

    Hodge, J. A.; Becker, R. H. [University of California, 1 Shields Avenue, Davis, CA 95616 (United States); White, R. L. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Richards, G. T., E-mail: hodge@mpia.de [Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States)

    2013-06-01

    We report on a blind survey for extragalactic radio variability that was carried out by comparing two epochs of data from the Faint Images of the Radio Sky at Twenty centimeters survey with a third epoch from a new 1.4 GHz survey of SDSS Stripe 82. The three epochs are spaced seven years apart and have an overlapping area of 60 deg{sup 2}. We uncover 89 variable sources down to the millijansky level, 75 of which are newly identified, and we find no evidence for transient phenomena. This new sample of variable sources allows us to infer an upper limit to the mean characteristic timescale of active galactic nucleus radio variability of 14 yr. We find that only 1% of extragalactic sources have fractional variability f {sub var} > 3, while 44% of Galactic sources vary by this much. The variable sample contains a larger fraction of quasars than a comparable non-variable control sample, though the majority of the variable sources appear to be extended galaxies in the optical. This implies that either quasars are not the dominant contributor to the variability of the sample, or that the deep optical data allow us to detect the host galaxies of some low-z quasars. We use the new, higher resolution data to report on the morphology of the variable sources. Finally, we show that the fraction of sources that are variable remains constant or increases at low flux densities. This may imply that next generation radio surveys with telescopes like Australian Square Kilometer Array Pathfinder and MeerKAT will see a constant or even increasing fraction of variable sources down into the sub-millijansky regime.

  5. Structural phase transition and magnetic properties of double perovskites Ba2CaMO6 (M=W, Re, Os)

    International Nuclear Information System (INIS)

    Yamamura, Kazuhiro; Wakeshima, Makoto; Hinatsu, Yukio

    2006-01-01

    Structures and magnetic properties for double perovskites Ba 2 CaMO 6 (M=W, Re, Os) were investigated. Both Ba 2 CaReO 6 and Ba 2 CaWO 6 show structural phase transitions at low temperatures. For Ba 2 CaReO 6 , the second order transition from cubic Fm3-bar m to tetragonal I4/m has been observed near 120K. For Ba 2 CaWO 6 , the space group of the crystal structure is I4/m at 295K and the transition to monoclinic I2/m has been observed between 220K. Magnetic susceptibility measurements show that Ba 2 CaReO 6 (S=1/2) and Ba 2 CaOsO 6 (S=1) transform to an antiferromagnetic state below 15.4 and 51K, respectively. Anomalies corresponding to their structural phase transition and magnetic transition have been also observed through specific heat measurements

  6. The phase diagrams and compensation behaviors of mixed spin Blume-Capel model in a trimodal magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.F. [Department of Physics, Suzhou University, Suzhou 215006 (China); Yan, S.L. [Department of Physics, Suzhou University, Suzhou 215006 (China); Jiangsu Key Loboratory of Film Materials, Suzhou University, Suzhou 215006 (China); CCAST (World Laboratory), PO Box 8730, Beijing 100080 (China)], E-mail: slyan@suda.edu.cn

    2008-04-07

    The phase diagrams and compensation behaviors of mixed spin-1/2 and spin-1 Blume-Capel model in a trimodal magnetic field are investigated in the framework of the effective field theory on simple cubic lattice. The change of negative crystal field and trimodal concentration can affect the TCP, the second-order phase and the magnetic field degeneration at ground state in T-H space. In T-D space, the trajectory of the TCP takes on the acre curve and there exist the two TCPs under certain condition. In addition to giving one or two compensation temperature points in M-T space, the mixed spin Blume-Capel model also provides one or two novel compensation magnetic field points in M-H space. Some results are not revealed in previous works.

  7. Neutron-diffraction measurements of an antiferromagnetic semiconducting phase in the vicinity of the high-temperature superconducting state of K(x)Fe(2-y)Se2.

    Science.gov (United States)

    Zhao, Jun; Cao, Huibo; Bourret-Courchesne, E; Lee, D-H; Birgeneau, R J

    2012-12-28

    The recently discovered K-Fe-Se high-temperature superconductor has caused heated debate regarding the nature of its parent compound. Transport, angle-resolved photoemission spectroscopy, and STM measurements have suggested that its parent compound could be insulating, semiconducting, or even metallic [M. H. Fang, H.-D. Wang, C.-H. Dong, Z.-J. Li, C.-M. Feng, J. Chen, and H. Q. Yuan, Europhys. Lett. 94, 27009 (2011); F. Chen et al., Phys. Rev. X 1, 021020 (2011); and W. Li et al., Phys. Rev. Lett. 109, 057003 (2012)]. Because the magnetic ground states associated with these different phases have not yet been identified and the relationship between magnetism and superconductivity is not fully understood, the real parent compound of this system remains elusive. Here, we report neutron-diffraction experiments that reveal a semiconducting antiferromagnetic (AFM) phase with rhombus iron vacancy order. The magnetic order of the semiconducting phase is the same as the stripe AFM order of the iron pnictide parent compounds. Moreover, while the sqrt[5]×sqrt[5] block AFM phase coexists with superconductivity, the stripe AFM order is suppressed by it. This leads us to conjecture that the new semiconducting magnetic ordered phase is the true parent phase of this superconductor.

  8. Magnetic solid-phase extraction based on mesoporous silica-coated magnetic nanoparticles for analysis of oral antidiabetic drugs in human plasma

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Karynne Cristina de; Andrade, Gracielle Ferreira [Centro de Desenvolvimento da Tecnologia Nuclear, CDTN/CNEN, Rua Professor Mário Werneck, s/n. Campus Universitário, Belo Horizonte, MG CEP 30.123-970 (Brazil); Vasconcelos, Ingrid; Oliveira Viana, Iara Maíra de; Fernandes, Christian [Departamento de Produtos Farmacêuticos, Faculdade de Farmácia, Universidade Federal de Minas Gerais, Belo Horizonte, MG (Brazil); Martins Barros de Sousa, Edésia, E-mail: sousaem@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear, CDTN/CNEN, Rua Professor Mário Werneck, s/n. Campus Universitário, Belo Horizonte, MG CEP 30.123-970 (Brazil)

    2014-07-01

    In the present work, magnetic nanoparticles embedded into mesoporous silica were prepared in two steps: first, magnetite was synthesized by oxidation–precipitation method, and next, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. The mesoporous SiO{sub 2}-coated Fe{sub 3}O{sub 4} samples were functionalized using octadecyltrimethoxysilane as silanizing agent. The pure and functionalized silica nanoparticles were physicochemically and morphologically characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N{sub 2} adsorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The resultant magnetic silica nanoparticles were applied as sorbents for magnetic solid-phase extraction (MSPE) of oral antidiabetic drugs in human plasma. Our results revealed that the magnetite nanoparticles were completely coated by well-ordered mesoporous silica with free pores and stable pore walls, and that the structural and magnetic properties of the Fe{sub 3}O{sub 4} nanoparticles were preserved in the applied synthesis route. Indeed, the sorbent material was capable of extracting the antidiabetic drugs from human plasma, being useful for the sample preparation in biological matrices. - Highlights: • SBA-15/Fe{sub 3}O{sub 4} was synthesized and functionalized with octadecyltrimethoxysilane. • Magnetite nanoparticles were completely coated by well-ordered mesoporous silica. • The samples were used as sorbent for magnetic solid-phase extraction (MSPE). • The sorbent material was capable of extracting drugs from human plasma. • The extraction ability makes the material a candidate to be employed as MSPE.

  9. Where is the magnetic energy for the expansion phase of auroral substorms accumulated? 2. The main body, not the magnetotail

    Science.gov (United States)

    Akasofu, Syun-Ichi

    2017-08-01

    It is suggested that the magnetosphere tries to stabilize itself by quickly unloading the magnetic energy accumulated within its main body, when the accumulated magnetic energy exceeds a limited amount, which can be identified as the energy for the expansion phase. It is this process which manifests as the impulsive expansion phase, during which auroral arcs advance well beyond the presubstorm latitude in the midnight sector. It was shown in the previous paper that the magnetotail does not have enough magnetic energy for a medium substorm (energy 5 × 1015 J; AE = 1000 nT). In this paper, it is shown that (1) the reason of the short lifetime (1-1.5 h) of the expansion phase is due to the fact that a limited amount of magnetic energy accumulated during the growth phase is dissipated in a period similar to the duration of the growth phase (1-1.5 h); the accumulation rate is similar to the dissipation rate during the expansion phase: (2) when the main body of the magnetosphere accumulates the magnetic energy, it is inflated; β (= (nkT/B2/8π)) even at XGSM = -6 RE becomes close to 1.0 for magnetic energy (2.9 × 1014 J) which is less than the amount consumed by a medium intensity substorm. (3) As a result, the plasma sheet current and thus the magnetosphere are expected to become unstable, unloading the accumulated excess magnetic energy and resulting in current reduction and deflation. (4) The resulting deflation can cause an earthward electric field of 5-50 mV/m, which can generate Bostrom's current system, which is mainly responsible in producing various phenomena of the expansion phase. (5) The large range of substorm intensity (AE = 100-2000 nT) is likely to be due to the location where the energy is accumulated; the closer is the distance to the Earth (XGSM between -10 RE and -4 RE), the more intense the substorm intensity is.

  10. Magnetic solid-phase extraction of phthalate esters (PAEs) in apparel textile by core-shell structured Fe3O4@silica@triblock-copolymer magnetic microspheres.

    Science.gov (United States)

    Xu, Mei; Liu, Minhua; Sun, Meirong; Chen, Kun; Cao, Xiujun; Hu, Yaoming

    2016-04-01

    In this paper, novel core-shell structured magnetic Fe3O4/silica nanocomposites with triblock-copolymer grafted on their surface (Fe3O4@SiO2@MDN) were successfully fabricated by combining a sol-gel method with a seeded aqueous-phase radical copolymerization approach. Owing to the excellent characteristics of the strong magnetic responsivity, outstanding hydrophilicity and abundant π-electron system, the obtained core-shell structured microspheres showed great potential as a magnetic solid phase extraction (MSPE) adsorbent. Several kinds of phthalate esters (PAEs) were selected as model analytes to systematically evaluate the applicability of adsorbents for extraction followed by gas chromatography-mass spectrometry (GC-MS) analyses. Various parameters, including adsorbents amounts, adsorption time, species of eluent, and desorption time were optimized. Under the optimized conditions, Validation experiments such as recovery, reproducibility, and limit of detection were carried on and showed satisfactory results. The analysis method showed excellent linearity with a wide range of 0.2-10mg/kg (R(2)>0.9974) and low limits of detection (LOD) of 0.02-0.09 mg/kg (S/N=3). Ultimately, the novel magnetic adsorbents were successfully employed to detect the PAEs in apparel textile samples. And the results indicated that this novel approach brought forward in the present work offered an attractive alternative for rapid, efficient and sensitive MSPE for PAEs compounds. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Preparation and characterization of magnetic carboxylated nanodiamonds for vortex-assisted magnetic solid-phase extraction of ziram in food and water samples.

    Science.gov (United States)

    Yılmaz, Erkan; Soylak, Mustafa

    2016-09-01

    A simple and rapid vortex-assisted magnetic solid phase extraction (VA-MSPE) method for the separation and preconcentration of ziram (zinc dimethyldithiocarbamate), subsequent detection of the zinc in complex structure of ziram by flame atomic absorption spectrometry (AAS) has been developed. The ziram content was calculated by using stoichiometric relationship between the zinc and ziram. Magnetic carboxylated nanodiamonds (MCNDs) as solid-phase extraction adsorbent was prepared and characterized by Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) spectrometry and scanning electron microscopy (SEM). These magnetic carboxylated nanodiamonds carrying the ziram could be easily separated from the aqueous solution by applying an external magnetic field; no filtration or centrifugation was necessary. Some important factors influencing the extraction efficiency of ziram such as pH of sample solution, amount of adsorbent, type and volume of eluent, extraction and desorption time and sample volume were studied and optimized. The total extraction and detection time was lower than 10min The preconcentration factor (PF), the precision (RSD, n=7), the limit of detection (LOD) and limit of quantification (LOQ) were 160, 7.0%, 5.3µgL(-1) and 17.5µgL(-1), respectively. The interference of various ions has been examined and the method has been applied for the determination of ziram in various waters, foodstuffs samples and synthetic mixtures. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. From stripe to slab confinement for DNA linearization in nanochannels

    Science.gov (United States)

    Cifra, Peter; Benkova, Zuzana; Namer, Pavol

    We investigate suggested advantageous analysis in the linearization experiments with macromolecules confined in a stripe-like channel using Monte Carlo simulations. The enhanced chain extension in a stripe that is due to significant excluded volume interactions between monomers in two dimensions weakens on transition to experimentally feasible slit-like channel. Based on the chain extension-confinement strength dependence and the structure factor behavior for the chain in stripe we infer the excluded volume regime typical for two-dimensional systems. On transition to the slab geometry, the advantageous chain extension decreases and the Gaussian regime is observed for not very long semiflexible chains. The evidence for pseudo-ideality in confined chains is based on indicators such as the extension curves, variation of the extension with the persistence length or the structure factor. The slab behavior is observed when the stripe (originally of monomer thickness) reaches the thickness larger than cca 10nm in the third dimension. This maximum height of the slab to retain the advantage of the stripe is very low and this have implication for DNA linearization experiments. The presented analysis, however, has a broader relevance for confined polymers. Support from Slovak R&D Agency (SRDA-0451-11) is acknowledged.

  13. Detection of microcalcifications by characteristic magnetic susceptibility effects using MR phase image cross-correlation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Baheza, Richard A. [Department of Biomedical Engineering and Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232-2310 (United States); Welch, E. Brian [Institute of Imaging Science and Departments of Radiology and Radiological Sciences and Biomedical Engineering, Vanderbilt University, Nashville, Tennessee 37232-2310 (United States); Gochberg, Daniel F. [Institute of Imaging Science and Departments of Radiology and Radiological Sciences, and Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37232-2310 (United States); Sanders, Melinda [Department of Pathology, Vanderbilt University, Nashville, Tennessee 37232-2310 (United States); Harvey, Sara [Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee 37232-2310 (United States); Gore, John C. [Institute of Imaging Science and Departments of Biomedical Engineering, Radiology and Radiological Sciences, Physics and Astronomy, and Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232-2310 (United States); Yankeelov, Thomas E., E-mail: thomas.yankeelov@vanderbilt.edu [Institute of Imaging Science and Departments of Radiology and Radiological Sciences, Biomedical Engineering, Physics and Astronomy, and Cancer Biology, Vanderbilt University, Nashville, Tennessee 37232-2310 (United States)

    2015-03-15

    Purpose: To develop and evaluate a new method for detecting calcium deposits using their characteristic magnetic susceptibility effects on magnetic resonance (MR) images at high fields and demonstrate its potential in practice for detecting breast microcalcifications. Methods: Characteristic dipole signatures of calcium deposits were detected in magnetic resonance phase images by computing the cross-correlation between the acquired data and a library of templates containing simulated phase patterns of spherical deposits. The influence of signal-to-noise ratio and various other MR parameters on the results were assessed using simulations and validated experimentally. The method was tested experimentally for detection of calcium fragments within gel phantoms and calcium-like inhomogeneities within chicken tissue at 7 T with optimized MR acquisition parameters. The method was also evaluated for detection of simulated microcalcifications, modeled from biopsy samples of malignant breast cancer, inserted in silico into breast magnetic resonance imaging (MRIs) of healthy subjects at 7 T. For both assessments of calcium fragments in phantoms and biopsy-based simulated microcalcifications in breast MRIs, receiver operator characteristic curve analyses were performed to determine the cross-correlation index cutoff, for achieving optimal sensitivity and specificity, and the area under the curve (AUC), for measuring the method’s performance. Results: The method detected calcium fragments with sizes of 0.14–0.79 mm, 1 mm calcium-like deposits, and simulated microcalcifications with sizes of 0.4–1.0 mm in images with voxel sizes between (0.2 mm){sup 3} and (0.6 mm){sup 3}. In images acquired at 7 T with voxel sizes of (0.2 mm){sup 3}–(0.4 mm){sup 3}, calcium fragments (size 0.3–0.4 mm) were detected with a sensitivity, specificity, and AUC of 78%–90%, 51%–68%, and 0.77%–0.88%, respectively. In images acquired with a human 7 T scanner, acquisition times below 12

  14. Detection of microcalcifications by characteristic magnetic susceptibility effects using MR phase image cross-correlation analysis

    Science.gov (United States)

    Baheza, Richard A.; Welch, E. Brian; Gochberg, Daniel F.; Sanders, Melinda; Harvey, Sara; Gore, John C.; Yankeelov, Thomas E.

    2015-01-01

    Purpose: To develop and evaluate a new method for detecting calcium deposits using their characteristic magnetic susceptibility effects on magnetic resonance (MR) images at high fields and demonstrate its potential in practice for detecting breast microcalcifications. Methods: Characteristic dipole signatures of calcium deposits were detected in magnetic resonance phase images by computing the cross-correlation between the acquired data and a library of templates containing simulated phase patterns of spherical deposits. The influence of signal-to-noise ratio and various other MR parameters on the results were assessed using simulations and validated experimentally. The method was tested experimentally for detection of calcium fragments within gel phantoms and calcium-like inhomogeneities within chicken tissue at 7 T with optimized MR acquisition parameters. The method was also evaluated for detection of simulated microcalcifications, modeled from biopsy samples of malignant breast cancer, inserted in silico into breast magnetic resonance imaging (MRIs) of healthy subjects at 7 T. For both assessments of calcium fragments in phantoms and biopsy-based simulated microcalcifications in breast MRIs, receiver operator characteristic curve analyses were performed to determine the cross-correlation index cutoff, for achieving optimal sensitivity and specificity, and the area under the curve (AUC), for measuring the method’s performance. Results: The method detected calcium fragments with sizes of 0.14–0.79 mm, 1 mm calcium-like deposits, and simulated microcalcifications with sizes of 0.4–1.0 mm in images with voxel sizes between (0.2 mm)3 and (0.6 mm)3. In images acquired at 7 T with voxel sizes of (0.2 mm)3–(0.4 mm)3, calcium fragments (size 0.3–0.4 mm) were detected with a sensitivity, specificity, and AUC of 78%–90%, 51%–68%, and 0.77%–0.88%, respectively. In images acquired with a human 7 T scanner, acquisition times below 12 min, and voxel sizes of

  15. Optimum Design of a Five-Phase Permanent Magnet Synchronous Motor for Underwater Vehicles by use of Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    S. Asghar Gholamian

    2012-12-01

    Full Text Available Permanent magnet synchronous motors are efficient motors which have widespread applications in electric industry due to their noticeable features. One of the interesting applications of such motors is in underwater vehicles. In these cases, reaching to minimum volume and high torque of the motor are the major concern. Design optimization can enhance their merits considerably, thus reduce volume and improve performance of motors. In this paper, a new method for optimum design of a five-phase surface-mounted permanent magnet synchronous motor is presented to achieve minimum loss and magnet volume with an increased torque. A multi-objective optimization is performed in search for optimum dimensions of the motor and its permanent magnets using particle swarm optimization. The design optimization results in a motor with great improvement regarding the original motor. Finally, finite element analysis is utilized to validate the accuracy of the design.

  16. Silicon transport under rotating and combined magnetic fields in liquid phase diffusion growth of SiGe

    Energy Technology Data Exchange (ETDEWEB)

    Armour, N.; Dost, S. [Crystal Growth Laboratory, University of Victoria, Victoria, BC, V8W 3P6 (Canada)

    2010-04-15

    The effect of applied rotating and combined (rotating and static) magnetic fields on silicon transport during the liquid phase diffusion growth of SiGe was experimentally studied. 72-hour growth periods produced some single crystal sections. Single and polycrystalline sections of the processed samples were examined for silicon composition. Results show that the application of a rotating magnetic field enhances silicon transport in the melt. It also has a slight positive effect on flattening the initial growth interface. For comparison, growth experiments were also conducted under combined (rotating and static) magnetic fields. The processed samples revealed that the addition of static field altered the thermal characteristics of the system significantly and led to a complete melt back of the germanium seed. Silicon transport in the melt was also enhanced under combined fields compared with experiments with no magnetic field. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Phase-separated magnetic ground state in Mn3Ga0.45Sn0.55C

    Science.gov (United States)

    Dias, E. T.; Priolkar, K. R.; Nigam, A. K.; Singh, R.; Das, A.; Aquilanti, G.

    2017-04-01

    The existence of nonergodic ground states is considered as a precursor to a first-order long-range magnetostructural transformation. Mn3Ga0.45Sn0.55C lies compositionally between two compounds, Mn3GaC and Mn3SnC , undergoing first-order magnetic transformation. However, Mn3Ga0.45Sn0.55C , which crystallizes in a single-phase cubic structure, exhibits more than one long-range magnetic transition. Using a combination of magnetization, ac susceptibility, neutron diffraction, and x-ray-absorption fine-structure techniques, it is shown that, although Mn3Ga0.45Sn0.55C exhibits long-range magnetic order, it presents a cluster glassy ground state due to formation of magnetically ordered Ga-rich and Sn-rich clusters. The clusters are big enough to present signatures of long-range magnetic order but are distributed in a way that limits interactions between two clusters of the same type, leading to a frozen magnetic state at low temperatures. The main reason for such a cluster-glass state is the difference in the local structure of Mn atoms that find themselves in Ga-rich and Sn-rich clusters.

  18. Magnetic solid-phase extraction based on mesoporous silica-coated magnetic nanoparticles for analysis of oral antidiabetic drugs in human plasma.

    Science.gov (United States)

    de Souza, Karynne Cristina; Andrade, Gracielle Ferreira; Vasconcelos, Ingrid; de Oliveira Viana, Iara Maíra; Fernandes, Christian; de Sousa, Edésia Martins Barros

    2014-07-01

    In the present work, magnetic nanoparticles embedded into mesoporous silica were prepared in two steps: first, magnetite was synthesized by oxidation-precipitation method, and next, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. The mesoporous SiO2-coated Fe3O4 samples were functionalized using octadecyltrimethoxysilane as silanizing agent. The pure and functionalized silica nanoparticles were physicochemically and morphologically characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The resultant magnetic silica nanoparticles were applied as sorbents for magnetic solid-phase extraction (MSPE) of oral antidiabetic drugs in human plasma. Our results revealed that the magnetite nanoparticles were completely coated by well-ordered mesoporous silica with free pores and stable pore walls, and that the structural and magnetic properties of the Fe3O4 nanoparticles were preserved in the applied synthesis route. Indeed, the sorbent material was capable of extracting the antidiabetic drugs from human plasma, being useful for the sample preparation in biological matrices. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Magnetic properties and phase stability of half-metal-type Co2Cr1-xFexGa alloys

    International Nuclear Information System (INIS)

    Kobayashi, K.; Umetsu, R.Y.; Fujita, A.; Oikawa, K.; Kainuma, R.; Fukamichi, K.; Ishida, K.

    2005-01-01

    The magnetic properties and phase stability of half-metal-type Co 2 Cr 1-x Fe x Ga alloys were investigated by differential scanning calorimetry (DSC), in a superconducting quantum interference device (SQUID) magnetometer and in a vibrating sample magnetometer (VSM), and by transmission electron microscopy (TEM). It was found that the L2 1 -type single-phase is obtainable for the entire concentration of x and that the value of the saturation magnetic moment M s at 4.2K in the lower composition range of x is in agreement with the generalized Slater-Pauling line, while it is rather larger than the generalized Slater-Pauling line above x=0.6. The Curie temperature T c monotonically increases, whereas the transition temperature from the L2 1 - to B2-type phase T t B2/L2 1 is almost constant at 1082+/-13K with increasing x

  20. Effect of Gd and Cr substitution on the structural, electronic and magnetic phases of SrRuO3: a case study of doping and chemical phase separation

    Science.gov (United States)

    Dalal, B.; Sarkar, B.; De, S. K.

    2017-12-01

    We explore the crystal structure, electrical resistivity and magnetic behavior of the compositional series (SrRuO3)1-x (GdCrO3) x (where 0 ≤slant x ≤slant 1 ), which resides between orthorhombic ferromagnetic (FM) metal SrRuO3 (TC = 160 K) and orthorhombic antiferromagnetic (AFM) insulator GdCrO3 (TN = 170 K). Crystal structure analysis reveals that complete solid solution exists only up to x = 0.1 , above which chemical phase separation of two/three phases occurs, and persists up to x = 0.7 . X-ray photoelectron spectroscopy measurement also corroborates the existence of Cr5+ for the intermediate composition x = 0.4 , which reinforces the astonishing scheelite-type GdCrO4 formation (at ambient pressure) for 0.2 ≤slant x ≤slant 0.5 compositions. Electrical resistivity measurements affirm the temperature driven metal to insulator (M–I) transition for x = 0.05 and 0.1 samples. Low temperature insulating state in these samples is interpreted by electron–electron interaction of weak disordered systems. Precise analysis of temperature dependent resistivity for x ≥slant 0.2 samples (which have insulating ground state) dictate that the transport phenomenon is mainly associated with Arrhenius-type charge conduction, Mott’s variable range hopping, short-range and long-range Coulomb interaction mediated hopping processes, due to the high degree of randomness. Interruption of magnetic Ru–O–Ru interaction by Ru–O–Cr and Cr–O–Cr interactions lowers the FM transition temperature (T C), and thereby introduces Griffiths phase in phase separated samples. Furthermore, we believe that a sharp rise in magnetization at low temperature for x ≥slant 0.2 samples is due to the formation of AFM GdCrO4 phase. Prominent thermal hysteresis in temperature dependent magnetization curves for x ≥slant 0.8 , and appearance of spin-reorientation transition for x = 1 are the distinct indications for transformation into canted AFM GdCrO3 oxide at higher x. The effective

  1. Effect of Gd and Cr substitution on the structural, electronic and magnetic phases of SrRuO3: a case study of doping and chemical phase separation.

    Science.gov (United States)

    Dalal, B; Sarkar, B; De, S K

    2017-12-13

    We explore the crystal structure, electrical resistivity and magnetic behavior of the compositional series (SrRuO 3 )[Formula: see text] (GdCrO 3 ) x (where [Formula: see text]), which resides between orthorhombic ferromagnetic (FM) metal SrRuO 3 ([Formula: see text] K) and orthorhombic antiferromagnetic (AFM) insulator GdCrO 3 ([Formula: see text] K). Crystal structure analysis reveals that complete solid solution exists only up to [Formula: see text], above which chemical phase separation of two/three phases occurs, and persists up to [Formula: see text]. X-ray photoelectron spectroscopy measurement also corroborates the existence of [Formula: see text] for the intermediate composition [Formula: see text], which reinforces the astonishing scheelite-type GdCrO 4 formation (at ambient pressure) for [Formula: see text] compositions. Electrical resistivity measurements affirm the temperature driven metal to insulator (M-I) transition for [Formula: see text] and [Formula: see text] samples. Low temperature insulating state in these samples is interpreted by electron-electron interaction of weak disordered systems. Precise analysis of temperature dependent resistivity for [Formula: see text] samples (which have insulating ground state) dictate that the transport phenomenon is mainly associated with Arrhenius-type charge conduction, Mott's variable range hopping, short-range and long-range Coulomb interaction mediated hopping processes, due to the high degree of randomness. Interruption of magnetic Ru-O-Ru interaction by Ru-O-Cr and Cr-O-Cr interactions lowers the FM transition temperature (T C ), and thereby introduces Griffiths phase in phase separated samples. Furthermore, we believe that a sharp rise in magnetization at low temperature for [Formula: see text] samples is due to the formation of AFM GdCrO 4 phase. Prominent thermal hysteresis in temperature dependent magnetization curves for [Formula: see text], and appearance of spin-reorientation transition for

  2. Magnetic order of Nd5Pb3 single crystals

    Science.gov (United States)

    Yan, J.-Q.; Ochi, M.; Cao, H. B.; Saparov, B.; Cheng, J.-G.; Uwatoko, Y.; Arita, R.; Sales, B. C.; Mandrus, D. G.

    2018-04-01

    We report millimeter-sized Nd5Pb3 single crystals grown out of a Nd-Co flux. We experimentally study the magnetic order of Nd5Pb3 single crystals by measuring the anisotropic magnetic properties, electrical resistivity under high pressure up to 8 GPa, specific heat, and neutron single crystal diffraction. Two successive magnetic orders are observed at T N1  =  44 K and T N2  =  8 K. The magnetic cells can be described with a propagation vector k=(0.5, 0, 0) . Cooling below T N1, Nd1 and Nd3 order forming ferromagnetic stripes along the b-axis, and the ferromagnetic stripes are coupled antiferromagnetically along the a-axis for the k=(0.5, 0, 0) magnetic domain. Cooling below T N2, Nd2 orders antiferromagnetically to nearby Nd3 ions. All ordered moments align along the crystallographic c-axis. The magnetic order at T N1 is accompanied by a quick drop of electrical resistivity upon cooling and a lambda-type anomaly in the temperature dependence of specific heat. At T N2, no anomaly was observed in electrical resistivity but there is a weak feature in specific heat. The resistivity measurements under hydrostatic pressures up to 8 GPa suggest a possible phase transition around 6 GPa. Our first-principles band structure calculations show that Nd5Pb3 has the same electronic structure as does Y5Si3 which has been reported to be a one-dimensional electride with anionic electrons that do not belong to any atom. Our study suggests that R 5Pb3 (R  =  rare earth) can be a materials playground for the study of magnetic electrides. This deserves further study after experimental confirmation of the presence of anionic electrons.

  3. In situ investigation of ordering phase transformations in FePt magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wittig, James E., E-mail: j.wittig@vanderbilt.edu [Interdisciplinary Materials Science, Vanderbilt University, PMB 351683, 2301 Vanderbilt Place, Nashville, TN 37232 (United States); Bentley, James, E-mail: bentleyj48@gmail.com [Materials Science and Technology Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6376 (United States); Allard, Lawrence F., E-mail: allardlfjr@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6376 (United States)

    2017-05-15

    In situ high-resolution electron microscopy was used to reveal information at the atomic level for the disordered-to-ordered phase transformation of equiatomic FePt nanoparticles that can exhibit outstanding magnetic properties after transforming from disordered face-centered-cubic into the tetragonal L1{sub 0} ordered structure. High-angle annular dark-field imaging in the scanning transmission electron microscope provided sufficient contrast between the Fe and Pt atoms to readily monitor the ordering of the atoms during in situ heating experiments. However, during continuous high-magnification imaging the electron beam influenced the kinetics of the transformation so annealing had to be performed with the electron beam blanked. At 500 °C where the reaction rate was relatively slow, observation of the transformation mechanisms using this sequential imaging protocol revealed that ordering proceeded from (002) surface facets but was incomplete and multiple-domain particles were formed that contained anti-phase domain boundaries and anti-site defects. At 600 and 700 °C, the limitations of sequential imaging were revealed as a consequence of increased transformation kinetics. Annealing for only 5 min at 700 °C produced complete single-domain L1{sub 0} order; such single-domain particles were more spherical in shape with (002) facets. The in situ experiments also provided information concerning nanoparticle sintering, coalescence, and consolidation. Although there was resistance to complete sintering due to the crystallography of L1{sub 0} order, the driving force from the large surface-area-to-volume ratio resulted in considerable nanoparticle coalescence, which would render such FePt nanoparticles unsuitable for use as magnetic recording media. Comparison of the in situ data acquired using the protocol described above with parallel ex situ annealing experiments showed that identical behavior resulted in all cases. - Highlights: • HAADF STEM imaging reveals the

  4. Strong-coupling phases of the spin-orbit-coupled spin-1 Bose-Hubbard chain: Odd-integer Mott lobes and helical magnetic phases

    Science.gov (United States)

    Pixley, J. H.; Cole, William S.; Spielman, I. B.; Rizzi, Matteo; Das Sarma, S.

    2017-10-01

    We study the odd-integer filled Mott phases of a spin-1 Bose-Hubbard chain and determine their fate in the presence of a Raman induced spin-orbit coupling which has been achieved in ultracold atomic gases; this system is described by a quantum spin-1 chain with a spiral magnetic field. The spiral magnetic field initially induces helical order with either ferromagnetic or dimer order parameters, giving rise to a spiral paramagnet at large field. The spiral ferromagnet-to-paramagnet phase transition is in a universality class with critical exponents associated with the divergence of the correlation length ν ≈2 /3 and the order-parameter susceptibility γ ≈1 /2 . We solve the effective spin model exactly using the density-matrix renormalization group, and compare with both a large-S classical solution and a phenomenological Landau theory. We discuss how these exotic bosonic magnetic phases can be produced and probed in ultracold atomic experiments in optical lattices.

  5. Structural, magnetic and superconducting phase transitions in CaFe2As2 under ambient and applied pressure

    International Nuclear Information System (INIS)

    Canfield, P.C.; Bud'ko, S.L.; Ni, N.; Kreyssig, A.; Goldman, A.I.; McQueeney, R.J.; Torikachvili, M.S.; Argyriou, D.N.; Luke, G.; Yu, W.

    2009-01-01

    At ambient pressure CaFe 2 As 2 has been found to undergo a first order phase transition from a high temperature, tetragonal phase to a low-temperature orthorhombic/antiferromagnetic phase upon cooling through T ∼ 170 K. With the application of pressure this phase transition is rapidly suppressed and by ∼0.35 GPa it is replaced by a first order phase transition to a low-temperature collapsed tetragonal, non-magnetic phase. Further application of pressure leads to an increase of the tetragonal to collapsed tetragonal phase transition temperature, with it crossing room temperature by ∼1.7 GPa. Given the exceptionally large and anisotropic change in unit cell dimensions associated with the collapsed tetragonal phase, the state of the pressure medium (liquid or solid) at the transition temperature has profound effects on the low-temperature state of the sample. For He-gas cells the pressure is as close to hydrostatic as possible and the transitions are sharp and the sample appears to be single phase at low temperatures. For liquid media cells at temperatures below media freezing, the CaFe 2 As 2 transforms when it is encased by a frozen media and enters into a low-temperature multi-crystallographic-phase state, leading to what appears to be a strain stabilized superconducting state at low temperatures.

  6. WISE-Selected Red and Obscured Quasars in Stripe 82

    Science.gov (United States)

    Glikman, Eilat; Lacy, M.; Urrutia, T.; Urry, C. M.

    2013-01-01

    We identified a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4 GHz in the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey with the near-infrared Two Micron All Sky Survey (2MASS) catalog and color-selecting red sources. We interpret this population of objects as a tansitional phase in merger-driven quasar/galaxy co-evolution where these reddened quasars are shedding their dusty environment prior to becoming a “normal” blue quasar. When correcting for extinction, we find that red quasars make up ~15%-20% of the luminous quasar population. The radio requirement was intended to avoid contamination from stars, but restricts our sample to radio-detected objects. With the release of the Wide-Field Infrared Survey Explorer (WISE) we can now select all red quasars regardless of their radio propoerties, using infrared colors. We present a pilot survey for heavily obscured luminous quasars using infrared selection from WISE colors in the SDSS Stripe 82. We concentrated on objects with both bright WISE 22 micron fluxes and 2MASS magnitudes that lack spectra in SDSS to identify the brightest (mostly high luminosity) sources that complement the fainter objects in Spitzer-selected samples. Our relatively liberal color selection produced a candidate list of 12 sources. We obtained near-infrared spectra for all using SpeX on IRTF and have spectroscopically confirmed at least five obscured and reddened quasars. We explore the nature of the dusty quasar population and how it depends on redshift, luminosity and radio-loudness.

  7. Effect of Magnetic Field on Saccharomyces cerevisiae Growth Rate and Division Phases

    International Nuclear Information System (INIS)

    El-Deen, Sh.Sh.

    2005-01-01

    The effect of Electromagnetic field (EMF) on growth rate and twokinds of meiotic and mititic divisions were studied in homothallic S. cerevisiae strain. An electromagnetic field (H) was used as 0.5 T and 1.0 T for 5,10 and 15 minutes. The yeast strain (local isolate, Iso-2) was haploid wild type. It was fluctuated of viable cell number or the survival percent from the beginning to the end growth time in this study (72h). The cell survival percent was decreased within 4th h from the beginning of inoculation. It was 53% at 4 h. The cell survival percent was the highest (94.8%) when cell culture exposed to 0.5 T for 15 min. EMF had been improvement to cell divdsion gap through the second or third generation to reveal 96% replacement low viable without EMF. Initiation, some haploid cells were converted to diploid phases; 60 diploids from 1*10 3 haploid cells. The diploids produced 4 asci. These percent had been increased to 260 diploids phase when its exposure to EMF 1.0 T for 10min. The diploids produced 25 asci. While with 0.5 T for 10 min was convenient to convert these diploids to asci (80%). Morphologically and cytologically does not experiment, neither 0.5 T nor 1.0 T increased cells vacuole size. EMF at 0.5 T for 15 min was induced chromosomes and cell division there were some phass of late metaphase and anaphase within the same culture beginning from single cell and exposed to magnetic field

  8. Roadway striping productivity data analysis for INDOT Greenfield and Crawfordsville districts.

    Science.gov (United States)

    2013-11-01

    The main objective of the SPR3650 project is to provide an accurate overview of striping operation so that INDOT finds a way to : effectively save significant investment for purchasing new striping trucks in near future without compromising roadwa...

  9. Twin InSb/GaAs quantum nano-stripes: Growth optimization and related properties

    Science.gov (United States)

    Narabadeesuphakorn, Phisut; Thainoi, Supachok; Tandaechanurat, Aniwat; Kiravittaya, Suwit; Nuntawong, Noppadon; Sopitopan, Suwat; Yordsri, Visittapong; Thanachayanont, Chanchana; Kanjanachuchai, Songphol; Ratanathammaphan, Somchai; Panyakeow, Somsak

    2018-04-01

    Growth of InSb/GaAs quantum nanostructures on GaAs substrate by using molecular beam epitaxy with low growth temperature and slow growth rate typically results in a mixture of isolated and paired nano-stripe structures, which are termed as single and twin nano-stripes, respectively. In this work, we investigate the growth conditions to maximize the number ratio between twin and single nano-stripes. The highest percentage of the twin nano-stripes of up to 59% was achieved by optimizing the substrate temperature and the nano-stripe growth rate. Transmission electron microscopy reveals the substantial size and height reduction of the buried nano-stripes. We also observed the Raman shift and photon emission from our twin nano-stripes. These twin nano-stripes are promising for spintronics and quantum computing devices.

  10. Investigating excitation-dependent and fringe-field effects of electromagnet and permanent-magnet phase shifters for a crossed undulator

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Ting-Yi, E-mail: chung.albert@nsrrc.org.tw [National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Yang, Chih-Sheng; Chu, Yun-Liang; Lin, Fu-Yuan; Jan, Jyh-Chyuan [National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Hwang, Ching-Shiang [National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Department of Electrophysics, National Chiao Tung University, Hsinchu 30050, Taiwan (China)

    2017-04-01

    To enhance the flux density or to control polarization, a phase shifter was designed and used to modulate the phase matching between segmented undulators. A larger hysteresis loop causes, however, a repeatability issue in the phase matching; the fringe field of the phase shifter creates an extra magnetic-field error. The design of the phase shifter must therefore minimize the hysteresis loop and fringe field to maintain the phases exact and to ignore the crosstalk effect. Two critical issues are the hysteresis-loop problem and the fringe-field effect, which determine the radiation performance and the stability of the ring. To investigate these issues, a phase shifter was constructed to operate in accordance with electromagnetic- and permanent-type magnets; the results from the field measurements and shims are discussed here. The shimming algorithm and a compact permanent-magnet phase shifter that eliminates the issues are also presented.

  11. POWER FACTOR CORRECTION IN PERMANENT MAGNET BRUSHLESS DC MOTOR DRIVE USING SINGLE-PHASE CUK CONVERTER

    Directory of Open Access Journals (Sweden)

    SANJEEV SINGH

    2010-12-01

    Full Text Available Permanent magnet brushless DC motor (PMBLDCM drives are being employed in many variable speed applications due to their high efficiency, silent operation, compact size, high reliability, ease of control, and low maintenance requirements. These drives have power quality problems and poor power factor at input AC mains as they are mostly fed through diode bridge rectifier based voltage source inverters. To overcome such problems a single-phase single-switch power factor correction AC-DC converter topology based on a Cuk converter is proposed to feed voltage source inverters based PMBLDCM. It focuses on the analysis, design and performance evaluation of the proposed PFC converter topology for a 1.5 kW, 1500 rpm, 400 V PMBLDCM drive used for an air-conditioning system. The proposed PFC converter topology is modelled and its performance is simulated in Matlab-Simulink environment and results show an improved power quality and good power factor in wide speed range of the drive.

  12. Rapid 2D phase-contrast magnetic resonance angiography reconstruction algorithm via compressed sensing

    Science.gov (United States)

    Lee, Dong-Hoon; Hong, Cheol-Pyo; Lee, Man-Woo; Han, Bong-Soo

    2013-09-01

    Phase-contrast magnetic resonance angiography (PC MRA) is an excellent technique for visualization of venous vessels. However, the scan time of PC MRA is long compared with there of other MRA techniques. Recently, the potential of compressed sensing (CS) reconstruction to reduce the scan time in MR image acquisition using a sparse sampling dataset has become an active field of study. In this study, we propose a combination method to apply the CS reconstruction method to 2D PC MRA. This work was performed to enable faster 2D PC MRA imaging acquisition and to demonstrate its feasibility. We used a 0.32 T MR imaging (MRI) system and a total variation (TV)-based CS reconstruction algorithm. To validate the usefulness of our proposed reconstruction method, we used visual assessment for reconstructed images, and we measured the quantitative information for sampling rates from 12.5 to 75.0%. Based on our results, when the sampling ratio is increased, images reconstructed with the CS method have a similar level of image quality to fully sampled reconstruction images. The signal to noise ratio (SNR) and the contrast-to-noise ratio (CNR) were also closer to the reference values when the sampling ratio was increased. We confirmed the feasibility of 2D PC MRA with the CS reconstruction method. Our results provide evidence that this method can improve the time resolution of 2D PC MRA.

  13. Distinguishing Patterns of Charge Order: Stripes or Checkerboards

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, J.A.

    2010-04-06

    In two dimensions, quenched disorder always rounds transitions involving the breaking of spatial symmetries so, in practice, it can often be difficult to infer what form the symmetry breaking would take in the 'ideal,' zero disorder limit. We discuss methods of data analysis which can be useful for making such inferences, and apply them to the problem of determining whether the preferred order in the cuprates is 'stripes' or 'checkerboards.' In many cases we show that the experiments clearly indicate stripe order, while in others (where the observed correlation length is short), the answer is presently uncertain.

  14. Visual acuity in the striped skunk (Mephitis mephitis).

    Science.gov (United States)

    Johnson-Ulrich, Zoe; Hoffmaster, Eric; Robeson, Audrey; Vonk, Jennifer

    2017-11-01

    The visual acuity of striped skunks (Mephitis mephitis) was tested using a 2 alternative forced-choice task with square wave gratings. Skunks were reinforced with food items for touching a ball in front of a striped stimulus when paired with a ball in front of a solid gray stimulus. Skunks demonstrated a maximum visual acuity of 0.42 cycles per degree when tested with bright outdoor illumination. This poor visual acuity may be due to their nocturnal lifestyle, lack of predation, and is consistent with their preferential use of smell and sound during foraging. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  15. Magnetic phase diagram of CeCu2Ge2 up to 15 T: On the route to understand field-induced phase transitions

    Science.gov (United States)

    Geselbracht, P.; Schneidewind, A.; Doerr, M.; Granovsky, S.; Rotter, M.; Loewenhaupt, M.; Scheerer, G. W.; Ren, Z.; Prokeš, K.

    2017-06-01

    The features of the magnetic (H ,T ) phase diagram of CeCu2Ge2 are similar to those of superconducting CeCu2Si2 , but the nature of these phases and transitions is still controversial. For CeCu2Ge2 we present results on electrical transport, thermodynamic measurements (magnetization, magnetostriction), and elastic neutron diffraction for fields up to 15 T parallel to the [110] direction. Two magnetic phases AF1, AF2 and a third, yet unidentified ferrimagnetic phase AF3 exist below TN=4.2 K and in fields up to approximately 26 T. At temperatures below 2.5 K a first-order transition from AF1 to AF2 at around 7.8 T was found experimentally, characterized by a shift of the observed propagation vector from q1=(0.285 -0.285 0.543 ) to q2=(0.34 -0.27 0.55 ) . Above 12.5 T reflections belonging neither to the AF1 nor to the AF2 type were found. To interpret the macroscopic measurements and neutron data a mean-field simulation with the McPhase program was carried out, yielding a low-field double-q magnetic structure AF1 with q1±=(0.278 ±0.278 0.556 ) that jumps to AF2 with q2±=(0.286 ±0.286 0.545 ) at about 5 T (to be compared to the experimental value of 7.8 T). This transition is followed by a single-q structure AF3 with q3=(0.28 0.28 0.56 ) at 10 T (as compared to 12.5 T from experiment) that is stable up to saturation at 26 T. These calculations also reveal the principal dependence of the experimental magnetization and susceptibility published earlier. The predicted single-q structure was not detectable by neutrons because of limitations in the employed scattering geometry.

  16. Magnetic characterization of mixed phases in FeVO4sbnd Co3V2O8 system

    Science.gov (United States)

    Guskos, N.; Zolnierkiewicz, G.; Pilarska, M.; Typek, J.; Berczynski, P.; Blonska-Tabero, A.; Aidinis, K.

    2018-04-01

    Dynamic and static magnetic properties of four nFeVO4/(1-n)Co3V2O8 composites obtained in reactions between nFeVO4 and (1-n)Co3V2O8 (n = 0.82, 0.80, 0.78 and 0.76) have been investigated by dc magnetometry and electron paramagnetic resonance (EPR). All samples were diphase containing both the howardevansite-type and the lyonsite-type phases in different proportions. Dc magnetic susceptibility study showed the Curie-Weiss paramagnetic behavior with strong antiferromagnetic (AFM) interaction in the high-temperature range and the phase transition to the AFM state at low temperatures. The calculated effective magnetic moment could be justified by the presence of high spin Fe3+ and Co2+ ions. The appearance of hysteresis loop in isothermal magnetisation at low temperature indicates the existence of the ferromagnetic component in all four samples, but only 0.5% of all magnetic ions are involved in this phase. EPR spectra recorded in high-temperature range (T > 90 K) consisted of a single broad line centred at ∼3.2 kG. The fitting of observed spectra with two Gaussian lineshape functions allowed to study the temperature dependence of EPR parameters (resonance field, linewidth, integrated intensity). This analysis suggests that EPR signal arises from two spin subsystems: paramagnetic Fe3+ ions subjected to AFM interaction and AFM spin pairs/clusters of iron/cobalt visible only at high temperatures. At low temperatures two transitions to AFM states, due to the mixture of two structural phases, are registered in magnetic susceptibility measurements.

  17. Phase diagrams of a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system under a time-dependent oscillating magnetic field

    International Nuclear Information System (INIS)

    Keskin, M.; Canko, O.; Gueldal, S.

    2009-01-01

    We present phase diagrams for a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system on a square lattice in the presence of a time dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the mean-field dynamical equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The dynamic phase transition points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p) and ferrimagnetic (i) phases, and one coexistence or mixed phase region, namely the i+p, that strongly depend on interaction parameters. The system exhibits the dynamic tricritical point and the reentrant behaviors.

  18. Phase diagrams of a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system under a time-dependent oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, M., E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Canko, O. [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Gueldal, S. [Institute of Science, Erciyes University, 38039 Kayseri (Turkey)

    2009-12-14

    We present phase diagrams for a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system on a square lattice in the presence of a time dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the mean-field dynamical equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The dynamic phase transition points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p) and ferrimagnetic (i) phases, and one coexistence or mixed phase region, namely the i+p, that strongly depend on interaction parameters. The system exhibits the dynamic tricritical point and the reentrant behaviors.

  19. Out-of-phase susceptibility and viscous magnetization: alternative tools for magnetic granulometry of sediments and soils

    Czech Academy of Sciences Publication Activity Database

    Chadima, Martin

    2016-01-01

    Roč. 6, Special issue (2016) ISSN 2007-9656. [Biennial Meeting Latinmag /4./. 23.11.2015-27.11.2015, Sao Paulo] Institutional support: RVO:67985831 Keywords : palaeomagnetism * sediments * soils Subject RIV: DE - Earth Magnetism, Geodesy, Geography http://www. geofisica .unam.mx/LatinmagLetters/LL16-01-SP/D/D07.pdf

  20. Ab initio calculations of martensitic phase behavior in Ni2FeGa magnetic shape memory alloys

    International Nuclear Information System (INIS)

    Soykan, C.; Özdemir Kart, S.; Sevik, C.; Çağın, T.

    2014-01-01

    Highlights: • L2 1 , NM and 5M phases have the energy minimum at a = 5.76 Å, c/a = 1.33 and c/a = 0.99. • Decrement in moment of Ni and increment in that of Fe reflect electrons transfer. • Differences in minority DOS over MT lead to stabilize the final structure. • C' taking small value in L2 1 leads to elastic instability in MT. - Abstract: A series of spin polarized energy calculations based on density functional theory (DFT) have been carried out to investigate the structural, magnetic, electronic and mechanical properties of Ni 2 FeGa magnetic shape memory alloys (MSMA’s) in the austenitic and martensitic structures. We report that L2 1 austenitic phase is metastable at a = 5.76 Å, the NM tetragonal and 5M monoclinic martensitic structures are stable at c/a = 1.33 and c/a = 0.99, respectively. That the electron removes from Ni to Fe site during phase transformation to martensite is confirmed by the increment in the magnetic moment of Ni, while decrement in that of Fe. The analysis of the partial density of states show that some distinguishable differences in the minority spin states occur upon martensitic phase transformation, such as, the replacement of the Fe states (e g and t 2g ) above Fermi level by only Fe-t 2g states during L2 1 -5M transformation and the splitting of Fe-t 2g states near Fermi level during 5M-NM transformation (through 7M). These changes lower the energy of the system, indicating that the final structure becomes stable. The soft tetragonal shear constant C′ of the austenitic phase designates the ease of the phase transition into martensitic phase. It is shown that the results calculated in this study are in good agreement with the previous calculations and the available experiments