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Sample records for magnetic properties existence

  1. Chondrule magnetic properties

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.; Obryan, M. V.

    1994-01-01

    The topics discussed include the following: chondrule magnetic properties; chondrules from the same meteorite; and REM values (the ratio for remanence initially measured to saturation remanence in 1 Tesla field). The preliminary field estimates for chondrules magnetizing environments range from minimal to a least several mT. These estimates are based on REM values and the characteristics of the remanence initially measured (natural remanence) thermal demagnetization compared to the saturation remanence in 1 Tesla field demagnetization.

  2. A doublet C0 IR solution using existing magnets

    SciTech Connect

    John A Johnstone

    2002-08-19

    This note explores, in a very limited way, some of the possibilities and difficulties encountered in creating collisions at C0 solely using magnets looted from the existing IR's at B0 and D0. In the strawman model considered her a standard Collins straight section is installed at D0, while all the useful D0 IR magnets are moved to C0. There is no obvious reason from either an optics or beam-separation viewpoint to prefer the demise of D0 over CDF, or vice-versa, so the model choice is fairly arbitrary. Apart from modifications to the final-focus optics, the magnets appear at C0 locations just as they are currently installed at D0.

  3. Magnetic properties of friction stir processed composite

    SciTech Connect

    Das, Shamiparna; Martinez, Nelson Y.; Das, Santanu; Mishra, Rajiv S.; Grant, Glenn J.; Jana, Saumyadeep; Polikarpov, Evgueni

    2016-03-29

    There are many existing inspection systems each with their own advantages and drawbacks. These usually comprise of semi-remote sensors which frequently causes difficulty in reaching complex areas of a component. This study proposes to overcome that difficulty by developing embedded functional composites. Through this route, embedding can be achieved in virtually any component part and can be periodically interrogated by a reading device. The “reinforcement rich” processed areas can then be utilized to record properties like strain, temperature, stress state etc. depending on the reinforcement material. In this work, friction stir processing (FSP) was utilized to fabricate a magnetostrictive composite by embedding galfenol particles into a nonmagnetic aluminum (Al) matrix. It targets to develop a composite that produces strain in a varying magnetic field. Reinforcements were observed to be distributed uniformly in the matrix. Magnetization curves were studied using a vibrating sample magnetometer (VSM). A simple and cheap setup was developed to measure the magnetostrictive strain of the composites. Important factors affecting the magnetic properties were identified and ways to improve the magnetic properties discussed.

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

    NASA Astrophysics Data System (ADS)

    Bjørk, R.

    2016-10-01

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

  5. Properties of asymmetric magnetic reconnection

    SciTech Connect

    Birn, J.; Borovsky, J. E.; Hesse, M.

    2008-03-15

    Properties of magnetic reconnection are investigated in two-dimensional, resistive magnetohydrodynamic (MHD) simulations of current sheets separating plasmas with different magnetic field strengths and densities. Specific emphasis is on the influence of the external parameters on the reconnection rate. The effect of the dissipation in the resistive MHD model is separated from this influence by evaluating resistivity dependence together with the dependence on the background parameters. Two scenarios are considered, which may be distinguished as driven and nondriven reconnection. In either scenario, the maximum reconnection rate (electric field) is found to depend on appropriate hybrid expressions based on a magnetic field strength and an Alfven speed derived from the characteristic values in the two inflow regions. The scaling compares favorably with an analytic formula derived recently by Cassak and Shay [Phys. Plasmas 14, 102114 (2007)] applied to the regime of fast reconnection. An investigation of the energy flow and conversion in the vicinity of the reconnection site revealed a significant role of enthalpy flux generation, in addition to the expected conversion of Poynting flux to kinetic energy flux. This enthalpy flux generation results from Ohmic heating as well as adiabatic, that is, compressional heating. The latter is found more important when the magnetic field strengths in the two inflow regions are comparable in magnitude.

  6. Modeling Magnetic Properties in EZTB

    NASA Technical Reports Server (NTRS)

    Lee, Seungwon; vonAllmen, Paul

    2007-01-01

    A software module that calculates magnetic properties of a semiconducting material has been written for incorporation into, and execution within, the Easy (Modular) Tight-Binding (EZTB) software infrastructure. [EZTB is designed to model the electronic structures of semiconductor devices ranging from bulk semiconductors, to quantum wells, quantum wires, and quantum dots. EZTB implements an empirical tight-binding mathematical model of the underlying physics.] This module can model the effect of a magnetic field applied along any direction and does not require any adjustment of model parameters. The module has thus far been applied to study the performances of silicon-based quantum computers in the presence of magnetic fields and of miscut angles in quantum wells. The module is expected to assist experimentalists in fabricating a spin qubit in a Si/SiGe quantum dot. This software can be executed in almost any Unix operating system, utilizes parallel computing, can be run as a Web-portal application program. The module has been validated by comparison of its predictions with experimental data available in the literature.

  7. Magnetic properties in an alternating-spin ferromagnetic Ising chain

    NASA Astrophysics Data System (ADS)

    Eloy, D.; Ramos, F. B.

    2011-08-01

    Using the transfer matrix technique, we investigated the magnetic properties of a ferromagnetic Ising chain with alternating-spins ( S, S') and single-ion anisotropy. We have calculated some physical quantities of interest such as the z component of the total magnetization per particle ( m) and magnetic susceptibility. In the regime of low temperatures, we observed the existence of magnetization plateaus. We constructed the phase diagrams of the magnetization in terms of the magnetic field and of the single-ion anisotropy for the case {1}/{2}≤(S,S')≤{9}/{2}. We were able to find a general rule for the magnetic transitions. We observed that the saturation value of the magnetization is msat=(S+S')/2.

  8. Magnetic Properties of Magnetic Nanoparticles for Efficient Hyperthermia

    PubMed Central

    Obaidat, Ihab M.; Issa, Bashar; Haik, Yousef

    2015-01-01

    Localized magnetic hyperthermia using magnetic nanoparticles (MNPs) under the application of small magnetic fields is a promising tool for treating small or deep-seated tumors. For this method to be applicable, the amount of MNPs used should be minimized. Hence, it is essential to enhance the power dissipation or heating efficiency of MNPs. Several factors influence the heating efficiency of MNPs, such as the amplitude and frequency of the applied magnetic field and the structural and magnetic properties of MNPs. We discuss some of the physics principles for effective heating of MNPs focusing on the role of surface anisotropy, interface exchange anisotropy and dipolar interactions. Basic magnetic properties of MNPs such as their superparamagnetic behavior, are briefly reviewed. The influence of temperature on anisotropy and magnetization of MNPs is discussed. Recent development in self-regulated hyperthermia is briefly discussed. Some physical and practical limitations of using MNPs in magnetic hyperthermia are also briefly discussed. PMID:28347000

  9. First-principles determination of magnetic properties

    NASA Astrophysics Data System (ADS)

    Wu, Ruqian; Yang, Zongxian; Hong, Jisang

    2003-02-01

    First-principles density functional theory calculations have achieved great success in the exciting field of low-dimension magnetism, in explaining new phenomena observed in experiments as well as in predicting novel properties and materials. As known, spin-orbit coupling (SOC) plays an extremely important role in various magnetic properties such as magnetic anisotropy, magnetostriction, magneto-optical effects and spin-dynamics. Using the full potential linearized augmented plane wave approach, we have carried out extensive investigations for the effects of SOC in various materials. Results of selected examples, such as structure and magnetic properties of Ni/Cu(001), magnetism and magnetic anisotropy in magnetic Co/Cu(001) thin films, wires and clusters, magnetostriction in FeGa alloys and magneto-optical effects in Fe/Cr superlattices, are discussed.

  10. Magnetic Properties of Tcnq Complexes

    NASA Astrophysics Data System (ADS)

    Qureshi, Saleem

    Available from UMI in association with The British Library. Requires signed TDF. This work can be divided up into three complementary steps. The first part of the work involved synthesis of a large number of TCNQ complexes, in particular complex salts, which are known to have promising electrical properties due to reduction in the on-site Coloumbic repulsion between the electrons. The cations used for the complexes are C12BPE (dodecyl bi pyridyl ethelenium), C10BPE, C8BPE, C6BPE, GTPP (geronyl triphenyl phosphonium), BI (butyl imidazolium), DMI (dimethyl imidazolium) and TB (toluidine blue). The second part of the project was to characterize these materials using different techniques to try to build up a knowledge of the materials. Particular interest was involved in the study of magnetic behaviour and in the later parts of the work some electrical measurements were made to try to determine the band gap, mobility and temperature dependence of conductivity. Considering the quasi-one-dimensional nature of the TCNQ salts, a theoretical model was devised based on the solution of one dimensional Heisenberg spin Hamiltonian. A computer program was developed that allowed for a numerical solution of a chain of spins in which number of spins could be varied. The Hamiltonian could be solved for up to 12 spins, the maximum allowable by the ICL 2900 computer at Crips computer centre of the University of Nottingham. The program allowed the user to input the coupling energy and alternation parameter between adjacent spins. The results from this program were used to explain magnetic behaviour of the TCNQ complexes prepared during this work.

  11. Magnetic properties of carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Lähderanta, E.; Lashkul, A. V.; Lisunov, K. G.; Zherebtsov, D. A.; Galimov, D. M.; Titkov, A. N.

    2012-08-01

    Magnetization M (T, B) of powder and glassy samples containing carbon nanoparticles is investigated in the interval of temperatures T between ~ 3 - 300 K and magnetic fields B up to 5 T. Low-field magnetization, M (T), exhibits a strong magnetic irreversibility, which is suppressed above the field of ~ 1 T. The dependence of M (B) saturates at high temperatures above B ~ 2 T, magnetic hysteresis is observed already at 300 K. The values of the saturation magnetization, the coercivity field and the maximum blocking temperature are obtained. Analysis of the experimental data gives evidence for concentration of the magnetization close to the surface of the particles, which is consistent with the origin of magnetism in nanocarbon presumably due to intrinsic disorder and surface defects.

  12. Origin of Magnetic Properties in Amorphous Metals.

    DTIC Science & Technology

    1979-12-01

    Magnetic Properties of Fe-Ni-B Amorphous Alloys," F. E. Luborsky, J. L. Walter, and H. H. Liebermann , IEEE Trans. on Magnetics MAG-15, 909 (1979). Also GE...Report 78CRD132. 2. "Formation and Magnetic Properties of Fe-B-Si Amorphous Alloys," F. E. Luborsky, J. J. Becker, J. L. Walter, and H. H. Liebermann ...Amorphous Alloys," F. E. Luborsky and H. H. Liebermann , J. Appl. Phys., to appear. Also GE Report 79CRD177. 4. "The Effect of Temperature on Magnetic

  13. Magnetic Properties of Antiferromagnetic Iron Oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Guyodo, Y. J.; Till, J. L.; Lagroix, F.; Bonville, P.; Penn, R. L.; Sainctavit, P.; Carvallo, C.; ona-Nguema, G.; Morin, G.

    2013-12-01

    Weakly magnetic iron oxyhydroxides such as ferrihydrite, lepidocrocite or goethite are commonly found in diverse geological and environmental setting, including ground waters and streams, sediments, soils, or acid mine drainage. These minerals take part in multiple biological and abiological processes, and can evolve to more magnetic phases such as hematite, maghemite, or magnetite. Therefore, they represent key minerals with regard to paleoclimate, paleoenvironmental, and paleomagnetic studies. At this meeting, we will present low temperature magnetic properties acquired on fully characterized synthetic samples. The complex nature of the magnetism of these minerals is revealed by comparing magnetic data with other types of characterizations such as high-resolution transmission electron microscopy or synchrotron X-ray magnetic circular dichroism (XMCD), or by studying the early-stages of solid-state alteration (under oxidizing or reducing atmosphere). In particular, we will present recent results about the presence of ferri-magnetic nano-clusters in lepidocrocite, and about uncompensated magnetic moments in goethite nanoparticles.

  14. Magnetic properties of high-density patterned magnetic media

    NASA Astrophysics Data System (ADS)

    Gurovich, B. A.; Prikhodko, K. E.; Kuleshova, E. A.; Yu Yakubovsky, A.; Meilikhov, E. Z.; Mosthenko, М. G.

    2010-10-01

    Structures of patterned magnetic media (PMM) with a density of 100-155 Gb/in. 2 have been prepared using the original method of selective removal of atoms making use of irradiation by an accelerated ion beam for producing patterns of materials whose chemical and physical properties are different from those of the matrix. Magnetic hysteresis loops for cobalt PMM structures with Co bit sizes of 40×15, 30×15, and 15×15 nm 2 show linear increase of coercivity with bit anisotropy factor. Consecutive reversals of nanobit magnetizations in bit ensembles have been visualized by the MFM technique, which allows one to reconstruct corresponding magnetic hysteresis loops.

  15. Transport and magnetic properties in topological materials

    NASA Astrophysics Data System (ADS)

    Liang, Tian

    The notion of topology has been the central topic of the condensed matter physics in recent years, ranging from 2D quantum hall (QH) and quantum spin hall (QSH) states, 3D topological insulators (TIs), topological crystalline insulators (TCIs), 3D Dirac/Weyl semimetals, and topological superconductors (TSCs) etc. The key notion of the topological materials is the bulk edge correspondence, i.e., in order to preserve the symmetry of the whole system (bulk+edge), edge states must exist to counter-compensate the broken symmetry of the bulk. Combined with the fact that the bulk is topologically protected, the edge states are robust due to the bulk edge correspondence. This leads to interesting phenomena of chiral edge states in 2D QH, helical edge states in 2D QSH, "parity anomaly'' (time reversal anomaly) in 3D TI, helical edge states in the mirror plane of TCI, chiral anomaly in Dirac/Weyl semimetals, Majorana fermions in the TSCs. Transport and magnetic properties of topological materials are investigated to yield intriguing phenomena. For 3D TI Bi1.1Sb0.9Te 2S, anomalous Hall effect (AHE) is observed, and for TCI Pb1-x SnxSe, Seebeck/Nernst measurements reveal the anomalous sign change of Nernst signals as well as the massive Dirac fermions. Ferroelectricity and pressure measurements show that TCI Pb1-xSnxTe undergoes quantum phase transition (QPT) from trivial insulator through Weyl semimetal to anomalous insulator. Dirac semimetals Cd3As2, Na 3Bi show interesting results such as the ultrahigh mobility 10 7cm2V-1s-1 protected from backscattering at zero magnetic field, as well as anomalous Nernst effect (ANE) for Cd3As2, and the negative longitudinal magnetoresistance (MR) due to chiral anomaly for Na3Bi. In-plane and out-of-plane AHE are observed for semimetal ZrTe5 by in-situ double-axes rotation measurements. For interacting system Eu2Ir2O7, full angle torque magnetometry measurements reveal the existence of orthogonal magnetization breaking the symmetry of

  16. Optical, magnetic and electronic properties of graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Guclu, A. Devrim

    2011-03-01

    We present a theory of optical, magnetic and electronic properties of graphene quantum dots. We demonstrate that there exists a class of triangular graphene quantum dots with zigzag edges [1-8] which combines magnetic, optical and transport properties in a single-material structure. These dots exhibit robust magnetic moment and optical transitions simultaneously in the THz, visible and UV spectral ranges due to the existence of a band of degenerate states lying at the Fermi level in the middle of the energy gap [1-6]. The magnetic and optical properties[5,7] are determined by strong electron-electron and excitonic interactions in the degenerate band, treated exactly using numerical techniques combining tight-binding, DFT, Hartree-Fock and configuration interactions methods. We show that the spin polarized degenerate band leads to quenching of the absorption spectrum at half-filling, while addition of a single electron fully depolarizes all electron spins and turns the absorption on. It is thus possible to design gate and size tunable graphene quantum dots with desired optical and magnetic properties for optoelectronic and photo-voltaic applications. Collaborators: P. Potasz, O. Voznyy, M. Korkusinski, and P. Hawrylak. The author thanks NRC-CNRS CRP, Canadian Institute for Advanced Research, Institute for Microstructural Sciences, and QuantumWorks for support.

  17. Magnetic properties of nanosize iron clusters

    SciTech Connect

    Venturini, E.L.; Wilcoxon, J.P.; Newcomer, P.P.

    1993-12-31

    Isolated, monodisperse {alpha}-Fe clusters between 1.4 and 15 nm in diameter were prepared inside inverse micelles using an oil-continuous, nonaqueous system. The magnetic properties of these clusters were studied in a SQUID magnetometer as a function of cluster size, temperature and applied magnetic field. The blocking temperature, coercive field and remanent moment of 12.5 nm Fe clusters in inverse micelles are significantly lower than those reported for clusters of similar {alpha}-Fe core size but with a surface oxide. The novel synthesis technique may yield metallic clusters with essentially intrinsic magnetic properties.

  18. Tailoring Magnetic Properties in Bulk Nanostructured Solids

    NASA Astrophysics Data System (ADS)

    Morales, Jason Rolando

    Important magnetic properties and behaviors such as coercivity, remanence, susceptibility, energy product, and exchange coupling can be tailored by controlling the grain size, composition, and density of bulk magnetic materials. At nanometric length scales the grain size plays an increasingly important role since magnetic domain behavior and grain boundary concentration determine bulk magnetic behavior. This has spurred a significant amount of work devoted to developing magnetic materials with nanometric features (thickness, grain/crystallite size, inclusions or shells) in 0D (powder), 1D (wires), and 2D (thin films) materials. Large 3D nanocrystalline materials are more suitable for many applications such as permanent magnets, magneto-optical Faraday isolators etc. Yet there are relatively few successful demonstrations of 3D magnetic materials with nanoscale influenced properties available in the literature. Making dense 3D bulk materials with magnetic nanocrystalline microstructures is a challenge because many traditional densification techniques (HIP, pressureless sintering, etc.) move the microstructure out of the "nano" regime during densification. This dissertation shows that the Current Activated Pressure Assisted Densification (CAPAD) method, also known as spark plasma sintering, can be used to create dense, bulk, magnetic, nanocrystalline solids with varied compositions suited to fit many applications. The results of my research will first show important implications for the use of CAPAD for the production of exchange-coupled nanocomposite magnets. Decreases in grain size were shown to have a significant role in increasing the magnitude of exchange bias. Second, preferentially ordered bulk magnetic materials were produced with highly anisotropic material properties. The ordered microstructure resulted in changing magnetic property magnitudes (ex. change in coercivity by almost 10x) depending on the relative orientation (0° vs. 90°) of an externally

  19. Tuning the Magnetic Properties of Nanoparticles

    PubMed Central

    Kolhatkar, Arati G.; Jamison, Andrew C.; Litvinov, Dmitri; Willson, Richard C.; Lee, T. Randall

    2013-01-01

    The tremendous interest in magnetic nanoparticles (MNPs) is reflected in published research that ranges from novel methods of synthesis of unique nanoparticle shapes and composite structures to a large number of MNP characterization techniques, and finally to their use in many biomedical and nanotechnology-based applications. The knowledge gained from this vast body of research can be made more useful if we organize the associated results to correlate key magnetic properties with the parameters that influence them. Tuning these properties of MNPs will allow us to tailor nanoparticles for specific applications, thus increasing their effectiveness. The complex magnetic behavior exhibited by MNPs is governed by many factors; these factors can either improve or adversely affect the desired magnetic properties. In this report, we have outlined a matrix of parameters that can be varied to tune the magnetic properties of nanoparticles. For practical utility, this review focuses on the effect of size, shape, composition, and shell-core structure on saturation magnetization, coercivity, blocking temperature, and relaxation time. PMID:23912237

  20. The magnetic-nanofluid heat pipe with superior thermal properties through magnetic enhancement

    PubMed Central

    2012-01-01

    This study developed a magnetic-nanofluid (MNF) heat pipe (MNFHP) with magnetically enhanced thermal properties. Its main characteristic was additional porous iron nozzle in the evaporator and the condenser to form a unique flowing pattern of MNF slug and vapor, and to magnetically shield the magnet attraction on MNF flowing. The results showed that an optimal thermal conductivity exists in the applied field of 200 Oe. Furthermore, the minor thermal performance of MNF at the condenser limited the thermal conductivity of the entire MNFHP, which was 1.6 times greater than that filled with water for the input power of 60 W. The feasibilities of an MNFHP with the magnetically enhanced heat transfer and the ability of vertical operation were proved for both a promising heat-dissipation device and the energy architecture integrated with an additional energy system. PMID:22716909

  1. Magnetic Properties of Electrically Contacted Fe4 Molecular Magnets

    NASA Astrophysics Data System (ADS)

    Burgess, Jacob; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Totti, Frederico; Ninova, Silviya; Yan, Shichao; Choi, Deung-Jang; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

    2015-03-01

    Single molecule magnets (SMMs) are often large and fragile molecules. This poses challenges for the construction of SMM based spintronics. Device geometries with two electronic leads contacting a molecule may be explored via scanning tunneling microscopy (STM). The Fe4 molecule stands out as a robust, thermally evaporable SMM, making it ideal for such an experiment. Here we present the first STM investigations of individual Fe4 molecules thermally evaporated onto a monolayer of Cu2N on a Cu (100) crystal. Using inelastic electron tunneling spectroscopy (IETS), spin excitations in single Fe4 molecules can be detected at meV energies. Analysis using a Spin Hamiltonian allows extraction of magnetic properties of individual Fe4 molecules, and investigation of the influence of the electronic leads. The tip and sample induce small changes in the magnetic properties of Fe4 molecules, making Fe4 a promising candidate for the development of spintronics devices based on SMMs.

  2. Indications of 8-kilogauss magnetic field existence in the sunspot umbra

    NASA Astrophysics Data System (ADS)

    Lozitsky, V. G.

    2016-01-01

    We present magnetic field diagnostics in two big sunspot of different magnetic polarity observed on 18 May 2002 and 29 October 2003. In these sunspots, according to visual measurements, magnetic field strength in Fe I 5250.2 Å line was about 3500 gauss. The existence of stronger fields follows from the detailed study of fine spectral effects in I ± V and V profiles of Fe I 6301.5 and 6302.5 Å lines, such as: (a) non-parallelism of bisectors in Fe I 6301.5 line related to distance about ±250 mÅ from the line center, and (b) weak secondary Stokes V peaks on distance, on the average, ±375 mÅ from the Fe I 6302.5 Å center. Consequently, we argue that these peculiarities indicate to the fact that spatially unresolved magnetic fields exist in the sunspot umbra, their strength being about 8 kG. In small structures with such very strong fields magnetic polarity was the same as in the background field of the sunspot umbra, and Doppler velocity is about -1.9 km/s (lifting of plasma).

  3. Magnetic properties of magnetoactive spin clusters

    SciTech Connect

    Khamzin, A. M.; Nigmatullin, R. R.

    2010-01-15

    A simple model is proposed for describing magnetic properties of magnetoactive nanoclusters, which permits exact analytic solution. Exact expressions are obtained for thermodynamic characteristics of the model, which hold in the entire range of temperatures, magnetic fields, and interaction parameters. It is found that in the case of easy-axis anisotropy, the field dependence of magnetization of a nanocluster consisting of N particles with a spin of 1/2 has [N/2] fractional plateaus ([ Horizontal-Ellipsis ] is the integer part) corresponding to polarized phases with ruptures singlet pairs. A nonmonotonic behavior observed for the magnetic susceptibility of an easy-plane cluster is typical of gap magnets. The spin gap between the ground state and excited states is proportional to the anisotropy parameter.

  4. Synthesis, magnetic and microstructural properties of Alnico magnets with additives

    NASA Astrophysics Data System (ADS)

    Ahmad, Zubair; Liu, Zhongwu; ul Haq, A.

    2017-04-01

    The phase formation, crystal structure, crystallographic texture, microstructure and magnetic properties of Alnico-8 alloys with varying Co and Nb content have been investigated and presented. Alnico-8 alloys were fabricated by induction melting and casting techniques. Magnetic properties in the alloys were induced by optimized thermomagnetic treatment and subsequent aging. The 37.9Fe-32Co-14Ni-7.5Al-3.1Cu-5.5Ti alloy exhibits coercivity of 110 kA/m, remanence of 0.66 T and energy product of 31.2 kJ/m3. The addition of 35 wt% Co in conjunction with 1.5 wt% Nb to 37.9Fe-14Ni-7.5Al-3.1Cu-5.5Ti alloys led to increase the magnetic properties, especially coercivity. The enhancement of the coercivity is attributed to ideal shape anisotropy and optimum mass fraction of ferromagnetic Fe-Co rich particles, which are 25-30 nm in diameter and 300-350 nm in length. The 33.4Fe-35Co-14Ni-7.5Al-5.5Ti-3.1Cu-1.5 Nb alloy yields the optimum magnetic properties of coercivity of 141.4 kA/m, remanence of 0.83 T and energy product of 42.4 kJ/m3. The good magnetic properties in the studied alloys are attributed to the nanostructured microstructure comprising textured Fe-Co-Nb rich α1 phase and Al-Ni-Cu rich α2 phase.

  5. Magnetic properties of nanocrystalline transition metals

    NASA Astrophysics Data System (ADS)

    Aus, Martin J.

    1999-09-01

    In the past decade, considerable attention has been devoted to the nanoprocessing of magnetic materials to enhance specific magnetic properties. For nanocrystalline materials in which the grain size approaches the dimensions of the domain wall thickness of conventional materials, considerable changes in magnetic behaviour are expected. In the present work, various electrodeposited ferromagnetic nanocrystalline pure metals and alloys were characterized by using a vibrating sample magnetometer. The systems investigated include pure Ni and Co as well as alloys of Ni-P, Ni-Fe and Co-Fe. These studies explored the effect of gram size on coercivity, indicating that the crystallographic texture is more significant than gram size. In addition, these studies reported, for the first time, that saturation magnetization of pore-free electroplated bulk nanocrystalline transition metals and their alloys is relatively little affected by grain size. In contrast, previously reported results for ultra-fine particles and nanomaterials produced from compacted powders showed a strong decrease in saturation magnetization with decreasing grain size. The difference in results for pore-free electrodeposits and ultrafine particles/compacted powders has been attributed to antiferromagnetic surface oxide layers, which is a direct result of large internal porosity in the latter group of materials. Further magnetic studies were completed on nanocrystalline electrodeposits produced by magnetoelectrohydrolysis. The effects of applied magnetic field strength and substrate orientation on saturation magnetization and coercivity of Ni-Fe and Co were explored. The results have shown that both nanoprocessing and electroplating in a magnetic field can improve soft magnetic properties by lowering the coercivity. Thermomagnetic studies examined saturation magnetization as a function of temperature, Curie temperature and coercivity changes during annealing. The Curie temperatures of electrodeposited

  6. Recent advances in magnetic nanoparticles with bulk-like properties

    NASA Astrophysics Data System (ADS)

    Batlle, Xavier

    2013-03-01

    Magnetic nanoparticles (NP) are an excellent example of nanostructured materials and exhibit fascinating properties with applications in high-density recording and biomedicine. Controlling the effects of the nanostructure and surface chemistry and magnetism at the monolayer level have become relevant issues. As the size is reduced below 100 nm, deviations from bulk behavior have been attributed to finite-size effects and changes in the magnetic ordering at the surface, thus giving rise to a significant decrease in the magnetization and increase in the magnetic anisotropy. The existence of a surface spin glass-like state due to magnetic frustration has been widely suggested in ferrimagnetic NP. However, in this talk, we will show that high crystal quality magnetite Fe3-xO4 NP of about a few nanometers in diameter and coated with different organic surfactants display bulk-like structural, magnetic and electronic properties. Magnetic measurements, transmission electron microscopy, X-ray absorption and magnetic circular dichroism and Monte Carlo simulations, evidenced that none of the usual particle-like behavior is observed in high quality NP of a few nm. Consequently, the magnetic and electronic disorder phenomena typically observed in those single-phase ferrimagnetic NP should not be considered as an intrinsic effect. We also performed a real-space characterization at the sub-nanometer scale, combining scanning transmission electron microscopy, electron energy loss spectroscopy and electron magnetic chiral dichroism. For the first time, we found that the surface magnetization is as high as about 70% of that of the core. The comparison to density functional theory suggested the relevance of the strong surface bond between the Fe ions and the organic surfactant. All the foregoing demonstrates the key role of both the crystal quality and surface bond on the physical properties of ferrimagnetic NP and paves the way to the fabrication of the next generation of NP with

  7. Linear and nonlinear magnetic properties of ferrofluids

    NASA Astrophysics Data System (ADS)

    Szalai, I.; Nagy, S.; Dietrich, S.

    2015-10-01

    Within a high-magnetic-field approximation, employing Ruelle's algebraic perturbation theory, a field-dependent free-energy expression is proposed which allows one to determine the magnetic properties of ferrofluids modeled as dipolar hard-sphere systems. We compare the ensuing magnetization curves, following from this free energy, with those obtained by Ivanov and Kuznetsova [Phys. Rev. E 64, 041405 (2001), 10.1103/PhysRevE.64.041405] as well as with new corresponding Monte Carlo simulation data. Based on the power-series expansion of the magnetization, a closed expression for the magnetization is also proposed, which is a high-density extension of the corresponding equation of Ivanov and Kuznetsova. From both magnetization equations the zero-field susceptibility expression due to Tani et al. [Mol. Phys. 48, 863 (1983), 10.1080/00268978300100621] can be obtained, which is in good agreement with our MC simulation results. From the closed expression for the magnetization the second-order nonlinear magnetic susceptibility is also derived, which shows fair agreement with the corresponding MC simulation data.

  8. Magnetic properties and energy-mapping analysis.

    PubMed

    Xiang, Hongjun; Lee, Changhoon; Koo, Hyun-Joo; Gong, Xingao; Whangbo, Myung-Hwan

    2013-01-28

    The magnetic energy levels of a given magnetic solid are closely packed in energy because the interactions between magnetic ions are weak. Thus, in describing its magnetic properties, one needs to generate its magnetic energy spectrum by employing an appropriate spin Hamiltonian. In this review article we discuss how to determine and specify a necessary spin Hamiltonian in terms of first principles electronic structure calculations on the basis of energy-mapping analysis and briefly survey important concepts and phenomena that one encounters in reading the current literature on magnetic solids. Our discussion is given on a qualitative level from the perspective of magnetic energy levels and electronic structures. The spin Hamiltonian appropriate for a magnetic system should be based on its spin lattice, i.e., the repeat pattern of its strong magnetic bonds (strong spin exchange paths), which requires one to evaluate its Heisenberg spin exchanges on the basis of energy-mapping analysis. Other weaker energy terms such as Dzyaloshinskii-Moriya (DM) spin exchange and magnetocrystalline anisotropy energies, which a spin Hamiltonian must include in certain cases, can also be evaluated by performing energy-mapping analysis. We show that the spin orientation of a transition-metal magnetic ion can be easily explained by considering its split d-block levels as unperturbed states with the spin-orbit coupling (SOC) as perturbation, that the DM exchange between adjacent spin sites can become comparable in strength to the Heisenberg spin exchange when the two spin sites are not chemically equivalent, and that the DM interaction between rare-earth and transition-metal cations is governed largely by the magnetic orbitals of the rare-earth cation.

  9. Possibility of checking the magnetic properties of ultrathin electrical steel strip during production

    SciTech Connect

    Korzunin, G.S.; Alekseev, V.A.; Rimshev, F.F.

    1995-12-01

    The possibility of making a final check of the magnetic properties of ultrathin electrical steel strip during production at the Ashina Metallurgical Works by using existing texturometers, which have proven themselves well in checking the uniformity of the properties of thick steel, or by direct measurement of the principal operating characteristics of steel (the energy loss due to magnetic reversal and the value of the magnetic induction). We consider how the degree of perfection of the crystallographic texture are related to the magnetic properties of thin strip and how the results of measurements of those properties are affected by the inevitable tension of the strip during production.

  10. On the Existence of Canonical Gyrokinetic Variables for Chaotic Magnetic Fields

    SciTech Connect

    Nicolini, Piero; Tessarotto, Massimo

    2008-12-31

    The gyrokinetic description of particle dynamics faces a basic difficulty when a special type of canonical variables is sought, i.e., the so-called gyrokinetic canonical variables. These are defined in such a way that two of them are respectively identified with the gyrophase-angle, describing the fast particle gyration motion around magnetic field lines, and its canonically conjugate momentum. In this paper we intend to discuss the conditions of existence for these variables.

  11. Magnetic properties of Martian surface material

    NASA Technical Reports Server (NTRS)

    Hargraves, R. B.

    1984-01-01

    The hypothesis that the magnetic properties of the Martian surface material are due to the production of a magnetic phase in the clay mineral nontronite by transient shock heating is examined. In the course of the investigation a magnetic material is produced with rather unusual properties. Heating from 900 C to 1000 C, of natural samples of nontronite leads first to the production of what appears to be Si doped maghemite gamma (-Fe2O3). Although apparently metastable, the growth of gamma -Fe2O3 at these temprtures is unexpected, and its relative persistence of several hours at 1000 C is most surprising. Continued annealing of this material for longer periods promote the crystallization of alpha Fe2O3 and cristobalite (high temperature polymorph of SiO2). All available data correlate this new magnetic material with the cristobalite hence our naming it magnetic ferri cristobalite. Formation of this magnetic cristobalite, however, may require topotactic growth from a smectite precursor.

  12. Magnetic Properties of 3D Printed Toroids

    NASA Astrophysics Data System (ADS)

    Bollig, Lindsey; Otto, Austin; Hilpisch, Peter; Mowry, Greg; Nelson-Cheeseman, Brittany; Renewable Energy; Alternatives Lab (REAL) Team

    Transformers are ubiquitous in electronics today. Although toroidal geometries perform most efficiently, transformers are traditionally made with rectangular cross-sections due to the lower manufacturing costs. Additive manufacturing techniques (3D printing) can easily achieve toroidal geometries by building up a part through a series of 2D layers. To get strong magnetic properties in a 3D printed transformer, a composite filament is used containing Fe dispersed in a polymer matrix. How the resulting 3D printed toroid responds to a magnetic field depends on two structural factors of the printed 2D layers: fill factor (planar density) and fill pattern. In this work, we investigate how the fill factor and fill pattern affect the magnetic properties of 3D printed toroids. The magnetic properties of the printed toroids are measured by a custom circuit that produces a hysteresis loop for each toroid. Toroids with various fill factors and fill patterns are compared to determine how these two factors can affect the magnetic field the toroid can produce. These 3D printed toroids can be used for numerous applications in order to increase the efficiency of transformers by making it possible for manufacturers to make a toroidal geometry.

  13. Estimation of hydrothermal deposits location from magnetization distribution and magnetic properties in the North Fiji Basin

    NASA Astrophysics Data System (ADS)

    Choi, S.; Kim, C.; Park, C.; Kim, H.

    2013-12-01

    The North Fiji Basin is belong to one of the youngest basins of back-arc basins in the southwest Pacific (from 12 Ma ago). We performed the marine magnetic and the bathymetry survey in the North Fiji Basin for finding the submarine hydrothermal deposits in April 2012. We acquired magnetic and bathymetry datasets by using Multi-Beam Echo Sounder EM120 (Kongsberg Co.) and Overhouser Proton Magnetometer SeaSPY (Marine Magnetics Co.). We conducted the data processing to obtain detailed seabed topography, magnetic anomaly, reduce to the pole(RTP), analytic signal and magnetization. The study areas composed of the two areas(KF-1(longitude : 173.5 ~ 173.7 and latitude : -16.2 ~ -16.5) and KF-3(longitude : 173.4 ~ 173.6 and latitude : -18.7 ~ -19.1)) in Central Spreading Ridge(CSR) and one area(KF-2(longitude : 173.7 ~ 174 and latitude : -16.8 ~ -17.2)) in Triple Junction(TJ). The seabed topography of KF-1 existed thin horst in two grabens that trends NW-SE direction. The magnetic properties of KF-1 showed high magnetic anomalies in center part and magnetic lineament structure of trending E-W direction. In the magnetization distribution of KF-1, the low magnetization zone matches well with a strong analytic signal in the northeastern part. KF-2 area has TJ. The seabed topography formed like Y-shape and showed a high feature in the center of TJ. The magnetic properties of KF-2 displayed high magnetic anomalies in N-S spreading ridge center and northwestern part. In the magnetization distribution of KF-2, the low magnetization zone matches well with a strong analytic signal in the northeastern part. The seabed topography of KF-3 presented a flat and high topography like dome structure at center axis and some seamounts scattered around the axis. The magnetic properties of KF-3 showed high magnetic anomalies in N-S spreading ridge center part. In the magnetization of KF-2, the low magnetization zone mismatches to strong analytic signal in this area. The difference of KF-3

  14. Properties of magnetically attractive experimental resin composites.

    PubMed

    Hirano, S; Yasukawa, H; Nomoto, R; Moriyama, K; Hirasawa, T

    1996-12-01

    SUS444 stainless steel filled chemically cured resin composites that can attract magnet were fabricated. The filler was treated with various concentrations of silane. The experimental composite was easy to handle and showed a good shelf life. The maximal properties obtained are as follows; The attraction force to a magnetic attachment was 1/3-1/4 lower than the commercially available magnet-keeper system for dental magnetic attachment. Flexural strength and Knoop hardness of the composite were 76MPa (7.7 kgf/mm2) and 64 KHN. These values were lower than the commercially available chemically cured composite used as a reference. Eluted metal from the composite in 1% lactic acid solution for 7 days showed 0.7 mg/cm2, but in 0.9% NaCl solution for 7 days, it could not be detected.

  15. Magnetic dipole discharges. I. Basic properties

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Teodorescu-Soare, C. T.; Ionita, C.; Schrittwieser, R.

    2013-08-15

    A simple discharge is described which uses a permanent magnet as a cold cathode and the metallic chamber wall as an anode. The magnet's equator is biased strongly negative, which produces secondary electrons due to the impact of energetic ions. The emitted electrons are highly confined by the strong dipolar magnetic field and the negative potential in the equatorial plane of the magnet. The emitted electrons ionize near the sheath and produce further electrons, which drift across field lines to the anode while the nearly unmagnetized ions are accelerated back to the magnet. A steady state discharge is maintained at neutral pressures above 10{sup −3} mbar. This is the principle of magnetron discharges, which commonly use cylindrical and planar cathodes rather than magnetic dipoles as cathodes. The discharge properties have been investigated in steady state and pulsed mode. Different magnets and geometries have been employed. The role of a background plasma has been investigated. Various types of instabilities have been observed such as sheath oscillations, current-driven turbulence, relaxation instabilities due to ionization, and high frequency oscillations created by sputtering impulses, which are described in more detail in companion papers. The discharge has also been operated in reactive gases and shown to be useful for sputtering applications.

  16. Magnetic properties of heterotrophic bacteria (abstract)

    NASA Astrophysics Data System (ADS)

    Verkhovceva, Nadezda V.; Glebova, Irina N.; Romanuk, Anatoly V.

    1994-05-01

    The magnetic properties (magnetic susceptibility and saturation magnetization) of six species of heterotrophic bacteria were studied: alcaligenes faecalis 81, arthrobacter globiformis BKM 685, bacillus cereus 8, leptothrix pseudo-ochracea D-405, proteus vulgaris 14, and seliberia stellata. It has been shown that the magnetic properties of bacteria depend on (1) the peculiarity of the micro-organism (species-specific and connected with cultivation conditions); (2) the source of the iron in the media. Most of the bacteria are diamagnetic in media with a minimum of iron (χ∞=-7.2-0.3×10-6 sm3/g). The spore forming species (bacillus cereus) has increased diamagnetism. Usually the bacteria are paramagnetic in iron-containing media because they concentrate into Fe compounds. The paramagnetism of the iron-concentrating species (anthrobacter globiformis -χpar=2.4×10-6, leptothrix pseudo-ochtracea χpar=11.0×10-6 and seliberia stellata χpar=3.2×10-6 sm3/g) depends, in general, on magnetically ordered compounds. Iron compounds not accumulated by proteus vulgaris and these species are always diamagnetic .

  17. Magnetic properties of ZnO nanoparticles.

    PubMed

    Garcia, M A; Merino, J M; Fernández Pinel, E; Quesada, A; de la Venta, J; Ruíz González, M L; Castro, G R; Crespo, P; Llopis, J; González-Calbet, J M; Hernando, A

    2007-06-01

    We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior in ZnO nanoparticles without doping with magnetic impurities but simply inducing an alteration of their electronic configuration. Capping ZnO nanoparticles ( approximately 10 nm size) with different organic molecules produces an alteration of their electronic configuration that depends on the particular molecule, as evidenced by photoluminescence and X-ray absorption spectroscopies and altering their magnetic properties that varies from diamagnetic to ferromagnetic-like behavior.

  18. Structure and Magnetic Properties of Lanthanide Nanocrystals

    SciTech Connect

    Dickerson, James Henry

    2014-06-01

    We have had considerable success on this project, particularly in the understanding of the relationship between nanostructure and magnetic properties in lanthanide nanocrystals. We also have successfully facilitated the doctoral degrees of Dr. Suseela Somarajan, in the Department of Physics and Astronomy, and Dr. Melissa Harrison, in the Materials Science Program. The following passages summarize the various accomplishments that were featured in 9 publications that were generated based on support from this grant. We thank the Department of Energy for their generous support of our research efforts in this area of materials science, magnetism, and electron microscopy.

  19. Existence of a component corotating with the earth in high-latitude disturbance magnetic fields

    NASA Technical Reports Server (NTRS)

    Suzuki, A.; Kim, J. S.; Sugiura, M.

    1982-01-01

    A study of the data from the high-latitude North American IMS network of magnetic stations suggests that there is a component in substorm perturbations that corotates with the earth. It is as yet not certain whether the existence of this component stems from the corotation of a part of the magnetospheric plasma involved in the substorm mechanism or if it is a 'phase change' resulting from the control of the substorm manifestations by the earth's main magnetic field which is not axially symmetric. There are other geophysical phenomena showing a persistence of longitudinal variations corotating with the earth. These phenomena are of significance for a better understanding of ionosphere-magnetosphere coupling.

  20. 36 CFR 72.41 - Demolition and replacement of existing recreation properties.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Demolition and replacement of existing recreation properties. 72.41 Section 72.41 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR URBAN PARK AND RECREATION RECOVERY ACT OF 1978 Grants for...

  1. 36 CFR 72.41 - Demolition and replacement of existing recreation properties.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Demolition and replacement of existing recreation properties. 72.41 Section 72.41 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR URBAN PARK AND RECREATION RECOVERY ACT OF 1978 Grants for...

  2. 36 CFR 72.41 - Demolition and replacement of existing recreation properties.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Demolition and replacement of existing recreation properties. 72.41 Section 72.41 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR URBAN PARK AND RECREATION RECOVERY ACT OF 1978 Grants for...

  3. 36 CFR 72.41 - Demolition and replacement of existing recreation properties.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Demolition and replacement of existing recreation properties. 72.41 Section 72.41 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR URBAN PARK AND RECREATION RECOVERY ACT OF 1978 Grants for...

  4. 36 CFR 72.41 - Demolition and replacement of existing recreation properties.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 1 2011-07-01 2011-07-01 false Demolition and replacement of existing recreation properties. 72.41 Section 72.41 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR URBAN PARK AND RECREATION RECOVERY ACT OF 1978 Grants for...

  5. Properties of Magnetic Reconnection as a function of magnetic shear

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Daughton, W. S.; Karimabadi, H.; Li, H.; Gary, S. P.; Guo, F.

    2013-12-01

    Observations of reconnection events at the Earth's magnetopause and in the solar wind show that reconnection occurs for a large range in magnetic shear angles extending to the very low shear limit 1. Here we report a fully kinetic study of the influence of the magnetic shear on details of reconnection such as its structure and rate. In previous work, we found that the electron diffusion region bifurcates into two or more distinct layers in regimes with weak magnetic shear2, a new feature that may be observable by NASA's up-coming Magnetospheric Multiscale mission. In this work, we have systematically extended the study to lower shear cases and found a new regime, where the reconnection electric field becomes much smaller and the properties of the reconnection changes significantly. We will discuss the role of various physics mechanisms in determining the observed scaling of the reconnection rate, including the dispersive properties of the waves in the system, the dissipation mechanisms and the tearing instability. 1 J. T. Goslings and T. D. Phan. APJL 763, L39, 2013 2 Yi-Hsin Liu et al. Phys. Rev. Lett. 110 , 265004, 2013

  6. Magnetic properties of artificially synthesized ferritins

    NASA Astrophysics Data System (ADS)

    Kim, B. J.; Lee, H. I.; Cho, S.-B.; Yoon, S.; Suh, B. J.; Jang, Z. H.; St. Pierre, T. G.; Kim, S.-W.; Kim, K.-S.

    2005-05-01

    Human ferritin homopolymers with H or L subunits (rHF and rLF) were genetically engineered in E coli. Apoferritins were then reconstituted with 2000 Fe atoms. A big difference was observed in the rates of iron uptake, whereas the mean core size was similar in rHF and rLF. Magnetization of the recombinant human ferritins were measured as functions of temperature and field. The blocking temperature TB(H) at low fields is considerably higher in rLF than in rHF. From the fit of M(H ) data to a modified Langevin function: M(H )=M0L(μpH/kBT)+χaH, the effective magnetic moment μp is found to be much larger in rLF than in rHF. Experimental data demonstrate that the magnetic properties, in particular, the uncompensated spins of ferritin core are related to the biomineralization process in ferritins.

  7. Magnetic properties and microstructure of bulk Nd-Fe-B magnets solidified in magnetic field

    NASA Astrophysics Data System (ADS)

    Wang, C.; Lai, Y. S.; Hsieh, C. C.; Chang, W. C.; Chang, H. W.; Sun, A. C.

    2011-04-01

    The Nd-Fe-B bulk magnets with a slab shape of 0.9 × 4 × 15 mm3 were prepared by injection casting into a copper mold. The effects of applying a magnetic field during the casting process on the magnetic properties and microstructure of Nd9.5Fe71.5Ti2.5Zr0.5Cr1B14.5C0.5 alloy have been studied. The results show that the sample cast with magnetic field has a stronger (00L) texture of Nd2Fe14B phase with the c-axis perpendicular to the slab plane than the sample cast without magnetic field. The intensity of the texture weakens from surface to inner region of the bulk magnets. Applying a magnetic field during the casting process is helpful to refine the grain size effectively. As a result, the magnetic properties are improved from Br = 5.8 kG, iHc = 6.5 kOe, and (BH)max = 5.9 MGOe for thesample cast without magnetic field to Br = 6.1 kG, iHc = 10.3 kOe, and (BH)max = 7.3 MGOe for the sample cast with a 3.7 kOe magnetic field.

  8. Electronic and magnetic properties of DUT-8(Ni).

    PubMed

    Trepte, Kai; Schwalbe, Sebastian; Seifert, Gotthard

    2015-07-14

    First principles calculations using density functional theory (DFT) have been performed to investigate the electronic and magnetic properties of DUT-8(Ni) (DUT - Dresden University of Technology). This flexible metal-organic framework (MOF) exists in two crystalline forms: DUT-8(Ni)open and DUT-8(Ni)closed. To identify the energetically favoured magnetic ordering, the density of states (DOS) and the energy difference between a low-spin (LS) and a high-spin (HS) coupling ΔELS-HS for those crystalline structures have been computed. Calculations on supercells have been carried out to include a variety of different magnetic couplings beyond a single unit cell. Several molecular model systems have been employed to further investigate the magnetic behaviour by introducing a diversity of chemical environments to the magnetic centers. The magnetic ground state of both crystalline structures has been found to be the low-spin state (S = 0). This low-spin ordering can be seen in the DOS as well as from ΔELS-HS calculations. Additionally, the calculations on the supercells confirm that the local character of the ordering (i.e. within the Ni dimers) is the most favoured one. However, the model systems indicate a change from the low-spin (S = 0) to a high-spin (S ≠ 0) ordering by introducing certain alterations into the chemical environment. Such alterations could be incorporated into the crystalline systems which should lead to similar results.

  9. Magnetic and dielectric properties of lunar samples

    NASA Technical Reports Server (NTRS)

    Strangway, D. W.; Pearce, G. W.; Olhoeft, G. R.

    1977-01-01

    Dielectric properties of lunar soil and rock samples showed a systematic character when careful precautions were taken to ensure there was no moisture present during measurement. The dielectric constant (K) above 100,000 Hz was directly dependent on density according to the formula K = (1.93 + or - 0.17) to the rho power where rho is the density in g/cc. The dielectric loss tangent was only slightly dependent on density and had values less than 0.005 for typical soils and 0.005 to 0.03 for typical rocks. The loss tangent appeared to be directly related to the metallic ilmenite content. It was shown that magnetic properties of lunar samples can be used to study the distribution of metallic and ferrous iron which shows systematic variations from soil type to soil type. Other magnetic characteristics can be used to determine the distribution of grain sizes.

  10. Magnetic and microstructural properties of nanocrystalline exchange coupled PrFeB permanent magnets

    NASA Astrophysics Data System (ADS)

    Goll, D.; Seeger, M.; Kronmüller, H.

    1998-05-01

    Nanocrystalline exchange coupled Pr 2Fe 14B single-phase and Pr 2Fe 14B+α-Fe two-phase magnets with grain sizes of about 20 nm were produced using the melt-spinning procedure. In the stoichiometric Pr 2Fe 14B composition a significantly enhanced remanence of JR=0.95 T was achieved in comparison with conventional Pr-rich and therefore decoupled isotropic PrFeB magnets ( JR⩽0.5 JS=0.78 T). In the composite magnets with overstoichiometric Fe a further enhancement of the remanence is possible. Values up to JR=1.42 T and ( BH) max=180.7 kJ/m 3 were obtained. As there exists no spin reorientation in PrFeB magnets, our attention was not only directed to the magnetic behaviour at room temperature but also to the magnetic properties in the whole ferromagnetic temperature range. The microstructural parameters Neff, αK and αex describing the influence of the non-ideal microstructure and the effect of the exchange coupling on the coercive field were determined within the framework of the nucleation model from the temperature dependence of the coercive field. Furthermore, reversibility measurements of the demagnetization curves in the second quadrant give important information about the magnetization processes in exchange coupled magnets. Moreover, we have investigated the law of approach to ferromagnetic saturation of the single-phase magnet in comparison with the decoupled one. The magnetic results are correlated with TEM investigations of the real microstructure.

  11. Proton Magnetic Form Factor from Existing Elastic e-p Cross Section Data

    NASA Astrophysics Data System (ADS)

    Ou, Longwu; Christy, Eric; Gilad, Shalev; Keppel, Cynthia; Schmookler, Barak; Wojtsekhowski, Bogdan

    2015-04-01

    The proton magnetic form factor GMp, in addition to being an important benchmark for all cross section measurements in hadron physics, provides critical information on proton structure. Extraction of GMp from e-p cross section data is complicated by two-photon exchange (TPE) effects, where available calculations still have large theoretical uncertainties. Studies of TPE contributions to e-p scattering have observed no nonlinear effects in Rosenbluth separations. Recent theoretical investigations show that the TPE correction goes to 0 when ɛ approaches 1, where ɛ is the virtual photon polarization parameter. In this talk, existing e-p elastic cross section data are reanalyzed by extrapolating the reduced cross section for ɛ approaching 1. Existing polarization transfer data, which is supposed to be relatively immune to TPE effects, are used to produce a ratio of electric and magnetic form factors. The extrapolated reduced cross section and polarization transfer ratio are then used to calculate GEp and GMp at different Q2 values.

  12. Magnetic Properties and Hyperfine Interactions in Iron Containing Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Unruh, Karl Marlin

    Amorphous samples of Fe(,x)B(,100-x) (30 (LESSTHEQ) x (LESSTHEQ) 90), Fe(,x)Ag(,100-x) (40 (LESSTHEQ) x (LESSTHEQ) 50), and Fe(,x)Zr(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 93) have been prepared, and their magnetic properties and hyperfine interactions studied by ('57)Fe Mossbauer spectroscopy. Each system is representative of either Fe-metalloid (Fe-B), Fe-noble metal (Fe-Ag), or Fe-early transition metal (Fe -Zr) amorphous alloys. Therefore, by studying these three amorphous solids an overview is obtained, not only of the properties of the individual alloys, but also of the wider class of alloys of which they are representative. The amorphous Fe-B and Fe-Zr systems have been successfully fabricated over very wide ranges in composition, allowing the evolution of the magnetic properties and hyperfine interactions to be systematically studied. As a result it has been possible to determine the critical concentration for magnetic order (x(,c)). It has been shown that the loss of magnetic order below x(,c) is the result of the reduction and eventual disappearance of the Fe moment. The isomer shifts (IS) and quadrupole splittings (QS) have also been determined over wide composition ranges. This has led to the observation of a maximum in IS with decreasing Fe concentration in amorphous alloys of Fe and B. On the other hand, IS in the amorphous Fe-Zr alloys has been found to decrease monotonically over the same concentration range. In the paramagnetic region all the samples display quadrupole split doublets characteristic of site symmetries lower than cubic. It has been found that the observed asymmetry in the quadrupole spectra can be correlated with the relative changes in IS and QS as a function of composition. Amorphous alloys of Fe and Ag have been prepared for the first time and have been found to be stable at room temperature. The somewhat unusual magnetic properties of these alloys suggests that they may be simpler magnetically than previously studied magnetic

  13. Physical and magnetic properties of magnetic nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Mohtasebzadeh, Abdul Rahman

    Using Scanning Electron Microscope (SEM) , Atomic Force Microscope (AFM) and Vibrating Sample Magnetometer (VSM) I studied magnetic-field directed selfassembly of magnetic nanoparticles into patterned arrays on the surface of perpendicular magnetic recording media. A controllable machine was used to coat super paramagnetic nano particles onto the surface of perpendicular recording media for different time intervals. Self assembled nano particles on the surface of the media, were transferred to a polymer layer to observe physical properties. Results from imaging shows that the average width and height of arrays is increasing as a function of time. Width of arrays with assembly time varies from 100nm at 5 minutes to 500nm at 120 minutes. Similarly, height changes from 13nm at 5 minutes to 37nm at 120 minutes. Therefore the pattern aspect ratio changes from 8:1 at 5 minutes to 14:1 at 120 minutes. For large widths compared with pattern spacing, array interaction appears as a slope change in VSM hysteresis loops. The hypothesis is that the difference in slope as a function of time for two cases; patterns oriented parallel and perpendicular to the external field is caused by array interaction; in other words wider patterns interact with each other more than narrower patterns.

  14. Philips 3T Intera Magnetic Resonance Imaging System and Upgrade of existing MRI equipment

    SciTech Connect

    Evanochko, William T

    2004-05-14

    The objective of this proposal was twofold. First, upgrade existing MRI equipment, specifically a research 4.1T whole-body system. Second, purchase a clinical, state-of-the-art 3T MRI system tailored specifically to cardiovascular and neurological applications. This project was within the guidelines of ''Medical Applications and Measurement Science''. The goals were: [1] to develop beneficial applications of magnetic resonance imaging; [2] discover new applications of MR strategies for medical research; and [2] apply them for clinical diagnosis. Much of this proposal searched for breakthroughs in this noninvasive and nondestructive imaging technology. Finally, this proposal's activities focused on research in the basic science of chemistry, biochemistry, physics, and engineering as applied to bioengineering. The centerpiece of this grant was our 4.1T ultra-high field whole-body nuclear magnetic resonance system and the newly acquired state-of-the-art, heart and head dedicated 3T clinical MRI system. We have successfully upgraded the equipment for the 4.1T system so that it is now state-of-the-art with new gradient and radio frequency amplifiers. We also purchase a unique In Vivo EKG monitoring unit that will permit tracking clinical quality EKG signals while the patient is in a high field MR scanner. Important upgrades of a peripheral vascular coil and a state-of-the-art clinical workstation for processing complex heart images were implemented. The most recent acquisition was the purchase of a state-of-the-art Philips 3T Intera clinical MRI system. This system is unique in that the magnet is only 5 1/2 feet long compare to over 12 feet long magnet of our 4.1T MRI system. The 3T MRI system is fully functional and its use and applications are already greatly benefiting the UAB with 200-300 micron resolution brain images and diagnostic quality MR angiography of coronary arteries in less than 5 minutes.

  15. 7 CFR 1955.134 - Loss, damage, or existing defects in inventory real property.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 14 2012-01-01 2012-01-01 false Loss, damage, or existing defects in inventory real... Disposal of Inventory Property General § 1955.134 Loss, damage, or existing defects in inventory real... a result of fire, vandalism, or an act of God between the time of acceptance of the bid or offer...

  16. 7 CFR 1955.134 - Loss, damage, or existing defects in inventory real property.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 14 2011-01-01 2011-01-01 false Loss, damage, or existing defects in inventory real... Disposal of Inventory Property General § 1955.134 Loss, damage, or existing defects in inventory real... a result of fire, vandalism, or an act of God between the time of acceptance of the bid or offer...

  17. 7 CFR 1955.134 - Loss, damage, or existing defects in inventory real property.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 14 2014-01-01 2014-01-01 false Loss, damage, or existing defects in inventory real... Disposal of Inventory Property General § 1955.134 Loss, damage, or existing defects in inventory real... a result of fire, vandalism, or an act of God between the time of acceptance of the bid or offer...

  18. 7 CFR 1955.134 - Loss, damage, or existing defects in inventory real property.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 14 2010-01-01 2009-01-01 true Loss, damage, or existing defects in inventory real... Disposal of Inventory Property General § 1955.134 Loss, damage, or existing defects in inventory real... a result of fire, vandalism, or an act of God between the time of acceptance of the bid or offer...

  19. 7 CFR 1955.134 - Loss, damage, or existing defects in inventory real property.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 14 2013-01-01 2013-01-01 false Loss, damage, or existing defects in inventory real... Disposal of Inventory Property General § 1955.134 Loss, damage, or existing defects in inventory real... a result of fire, vandalism, or an act of God between the time of acceptance of the bid or offer...

  20. Microscopic and magnetic properties of template assisted electrodeposited iron nanowires

    SciTech Connect

    Irshad, M. I. Mohamed, N. M. Yar, A.; Ahmad, F. Abdullah, M. Z.

    2015-07-22

    Nanowires of magnetic materials such as Iron, nickel, cobalt, and alloys of them are one of the most widely investigated structures because of their possible applications in high density magnetic recording media, sensor elements, and building blocks in biological transport systems. In this work, Iron nanowires have been prepared by electrodeposition technique using Anodized Aluminium Oxide (AAO) templates. The electrolyte used consisted of FeSO{sub 4.}6H{sub 2}O buffered with H{sub 3}BO{sub 3} and acidized by dilute H{sub 2}SO{sub 4}. FESEM analysis shows that the asdeposited nanowires are parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. To fabricate the working electrode, a thin film of copper (∼ 220 nm thick) was coated on back side of AAO template by e-beam evaporation system to create electrical contact with the external circuit. The TEM results show that electrodeposited nanowires have diameter around 100 nm and are polycrystalline in structure. Magnetic properties show the existence of anisotropy for in and out of plane configuration. These nanowires have potential applications in magnetic data storage, catalysis and magnetic sensor applications.

  1. Microscopic and magnetic properties of template assisted electrodeposited iron nanowires

    NASA Astrophysics Data System (ADS)

    Irshad, M. I.; Ahmad, F.; Mohamed, N. M.; Abdullah, M. Z.; Yar, A.

    2015-07-01

    Nanowires of magnetic materials such as Iron, nickel, cobalt, and alloys of them are one of the most widely investigated structures because of their possible applications in high density magnetic recording media, sensor elements, and building blocks in biological transport systems. In this work, Iron nanowires have been prepared by electrodeposition technique using Anodized Aluminium Oxide (AAO) templates. The electrolyte used consisted of FeSO4.6H2O buffered with H3BO3 and acidized by dilute H2SO4. FESEM analysis shows that the asdeposited nanowires are parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. To fabricate the working electrode, a thin film of copper (˜ 220 nm thick) was coated on back side of AAO template by e-beam evaporation system to create electrical contact with the external circuit. The TEM results show that electrodeposited nanowires have diameter around 100 nm and are polycrystalline in structure. Magnetic properties show the existence of anisotropy for in and out of plane configuration. These nanowires have potential applications in magnetic data storage, catalysis and magnetic sensor applications.

  2. Magnetic properties of Fe/Zr multilayers

    SciTech Connect

    Dubowik, J.; Stobiecki, F.; Szymanski, B.

    1994-03-01

    Measurements of ferromagnetic resonance (FMR), magnetic moment, and torque curves have been made for three series of Fe/Zr multilayers (MLs) with thickness ratio of Fe to Zr sublayers equal to 2:1, 1:1, and 1:2, respectively. The authors show that Fe/Zr MLs readily yield to amorphization by a solid-state reaction (SSR) during the deposition process. Nevertheless, the resulting structure may be regarded as inhomogeneous one; there still exist some ferromagnetic phases that they relate to the Fe atoms in various surroundings.

  3. Magnetic properties changes due to hydrocarbon contaminated groundwater table fluctuations

    NASA Astrophysics Data System (ADS)

    Ameen, Nawrass

    2013-04-01

    This study aims to understand the mechanisms and conditions which control the formation and transformation of ferro(i)magnetic minerals caused by hydrocarbon contaminated groundwater, in particular in the zone of fluctuating water levels. The work extends previous studies conducted at the same site. The study area is a former military air base at Hradčany, Czech Republic (50°37'22.71"N, 14°45'2.24"E). The site was heavily contaminated with petroleum hydrocarbons, due to leaks in petroleum storage tanks and jet fuelling stations over years of active use by the Soviet Union, which closed the base in 1991. The site is one of the most important sources of high quality groundwater in the Czech Republic. In a previous study, Rijal et al. (2010) concluded that the contaminants could be flushed into the sediments as the water level rose due to remediation processes leading to new formation of magnetite. In this previous study three different locations were investigated; however, from each location only one core was obtained. In order to recognize significant magnetic signatures versus depth three cores from each of these three locations were drilled in early 2012, penetrating the unsaturated zone, the groundwater fluctuation (GWF) zone and extending to about one meter below the groundwater level (~2.3 m depth at the time of sampling). Magnetic susceptibility (MS) profiles combined with other magnetic properties were analyzed to obtain a significant depth distribution of the ferro(i)magnetic concentration. Sediment properties, hydrocarbon content and bacterial activity were additionally studied. The results show that the highest ferrimagnetic mineral concentrations exist between 1.4-1.9 m depth from the baseline which is interpreted as the top of the GWF zone. Spikes of MS detected in the previous studies turned out to represent small-scale isolated features, but the trend of increasing MS values from the lowermost position of the groundwater table upward was verified

  4. Bistability properties of magnetic micro-nanowires

    NASA Astrophysics Data System (ADS)

    Baranov, S. A.; Yaltychenko, O. V.; Kanarovskii, E. Yu.

    2016-12-01

    A mathematical model that describes the process of the reversal magnetization of an amorphous microwire with the help of a large Barkhausen jump is proposed. The model has been estimated with regard to the optimization of the signal-tonoise ratio. Using nonlinear model, we studied the physical factors that cause the fluctuations of the start field. Based on the results of numerical experiments, the new data on the behavior of the start field under different conditions of a switching in a bistable ferromagnetic, including the conditions of high-frequency swapping, have been obtained and compared to the existing data. The results obtained do not contradict the existing physical concepts concerning a domain wall motion and are more general and realistic in a comparison with the previous model.

  5. Existence of the multiferroic property at room temperature in Ti doped CoFeO

    NASA Astrophysics Data System (ADS)

    Dwivedi, G. D.; Joshi, Amish G.; Kevin, H.; Shahi, P.; Kumar, A.; Ghosh, A. K.; Yang, H. D.; Chatterjee, Sandip

    2012-03-01

    The appearance of ferroelectricity has been observed in magnetically ordered Co(Fe1-xTix)2O4 at room temperature. Magnetization and dielectric constant is found to increase with Ti doping. It is observed from an X-ray Photoemission Spectroscopy study that Ti goes to the octahedral site with (+4) ionic state. An M-H hysteresis curve at room temperature shows the ferrimagnetic ordering and a P-E loop at room temperature clearly indicates the existence of ferroelectricity.

  6. A measurement setup for acquiring the local magnetic properties of plastically deformed soft magnetic materials

    SciTech Connect

    Bi Shasha; Sutor, Alexander; Lerch, Reinhard; Xiao Yunshi

    2011-04-01

    This paper introduces a new measurement setup for extraction of the local magnetic properties. With the help of finite element method simulations, modifications are made on the previous double-C-yoke method. Small dimension measuring coils are applied in the stray field produced by the magnetic circuit to evaluate the local magnetic properties of the specified part of the specimen. Through the measurements with the plastically deformed materials at different temperatures, it indicates that the magnetic properties of soft magnetic materials are quite sensitive to plastic straining. After high-temperature thermal treatment on the plastically deformed specimen, the local magnetic properties exhibit an obvious recovery.

  7. Hygroscopic properties of magnetic recording tape

    NASA Technical Reports Server (NTRS)

    Cuddihy, E. F.

    1976-01-01

    Relative humidity has been recognized as an important environmental factor in many head-tape interface phenomena such as headwear, friction, staining, and tape shed. Accordingly, the relative humidity is usually specified in many applications of tape use, especially when tape recorders are enclosed in hermetically sealed cases. Normally, the relative humidity is believed regulated by humidification of the fill gas to the specification relative humidity. This study demonstrates that the internal relative humidity in a sealed case is completely controlled by the time-dpendence of the hygroscopic properties of the pack of magnetic recording tape. Differences are found in the hygroscopic properties of the same brand of tape, which apparently result from aging, and which may have an effect on the long-term humidity-regulating behavior in a sealed case, and on the occurrence of head-tape interface phenomena from the long-term use of the tape. Results are presented on the basic hygroscopic properties of magnetic tape, its humidity-regulating behavior in a sealed case, and a theoretical commentary on the relative humidity dependence of head-wear by tape, is included.

  8. Properties of mesons in a strong magnetic field.

    PubMed

    Zhang, Rui; Fu, Wei-Jie; Liu, Yu-Xin

    By extending the [Formula: see text]-derivable approach in the Nambu-Jona-Lasinio model to a finite magnetic field we calculate the properties of pion, [Formula: see text], and [Formula: see text] mesons in a magnetic field at finite temperature not only in the quark-antiquark bound state scheme but also in the pion-pion scattering resonant state scenario. Our calculation as a result makes manifest that the masses of [Formula: see text] and [Formula: see text] meson can be nearly degenerate at the pseudo-critical temperature which increases with increasing magnetic field strength, and the [Formula: see text] mass ascends suddenly at almost the same critical temperature. Meanwhile the [Formula: see text] mesons' masses decrease with the temperature but increase with the magnetic field strength. We also check the Gell-Mann-Oakes-Renner relation and find that the relation can be violated clearly with increasing temperature, and the effect of the magnetic field becomes pronounced around the critical temperature. With different criteria, we analyze the effect of the magnetic field on the chiral phase transition and find that the pseudo-critical temperature of the chiral phase cross, [Formula: see text], is always enhanced by the magnetic field. Moreover, our calculations indicate that the [Formula: see text] mesons will get melted as the chiral symmetry has not yet been restored, but the [Formula: see text] meson does not disassociate even at very high temperature. Particularly, it is the first to show that there does not exist a vector meson condensate in the QCD vacuum in the pion-pion scattering scheme.

  9. Magnetic properties of arrays of electrodeposited nanowires

    NASA Astrophysics Data System (ADS)

    Ross, C. A.; Hwang, M.; Shima, M.; Smith, Henry I.; Farhoud, M.; Savas, T. A.; Schwarzacher, W.; Parrochon, J.; Escoffier, W.; Bertram, H. Neal; Humphrey, F. B.; Redjdal, M.

    2002-08-01

    The fabrication and magnetic properties of arrays of short nanowires are reviewed. The arrays consist of electrodeposited ferromagnetic cylinders with aspect ratios of up to 3 and diameters of 57-180 nm. Their hysteresis loops are characterized and their remanent states are related to the predictions of a three-dimensional micromagnetic model, which shows a transition from a single-domain 'flower' state to a lower-remanence 'vortex' state with increasing diameter. The shapes of the array hysteresis loops are governed by interactions between the particles. The switching fields of small Ni cylinders can be described using a dynamic micromagnetic model.

  10. Frequency-Dependent Properties of Magnetic Nanoparticle Crystals

    SciTech Connect

    Majetich, Sara

    2016-05-17

    In the proposed research program we will investigate the time- and frequency-dependent behavior of ordered nanoparticle assemblies, or nanoparticle crystals. Magnetostatic interactions are long-range and anisotropic, and this leads to complex behavior in nanoparticle assemblies, particularly in the time- and frequency-dependent properties. We hypothesize that the high frequency performance of composite materials has been limited because of the range of relaxation times; if a composite is a dipolar ferromagnet at a particular frequency, it should have the advantages of a single phase material, but without significant eddy current power losses. Arrays of surfactant-coated monodomain magnetic nanoparticles can exhibit long-range magnetic order that is stable over time. The magnetic domain size and location of domain walls is governed not by structural grain boundaries but by the shape of the array, due to the local interaction field. Pores or gaps within an assembly pin domain walls and limit the domain size. Measurements of the magnetic order parameter as a function of temperature showed that domains can exist at high temoerature, and that there is a collective phase transition, just as in an exchange-coupled ferromagnet. Dipolar ferromagnets are not merely of fundamental interest; they provide an interesting alternative to exchange-based ferromagnets. Dipolar ferromagnets made with high moment metallic particles in an insulating matrix could have high permeability without large eddy current losses. Such nanocomposites could someday replace the ferrites now used in phase shifters, isolators, circulators, and filters in microwave communications and radar applications. We will investigate the time- and frequency-dependent behavior of nanoparticle crystals with different magnetic core sizes and different interparticle barrier resistances, and will measure the magnetic and electrical properties in the DC, low frequency (0.1 Hz - 1 kHz), moderate frequency (10 Hz - 500

  11. Magnetic properties of some rare-earth nanostuctured aluminates

    NASA Astrophysics Data System (ADS)

    Lovchinov, V.; Petrov, D.; Simeonova, P.; Angelov, B.

    2010-11-01

    Nanocrystalline single-phase RAlO3 (R = Nd, Sm, Eu, Dy, Gd) has been prepared by modified Pechini's method. Malic acid has been used for the first time as a new complexing agent in the sol-gel process. It has facilited a low temperature synthesis of the compound. The characterization of the nanoparticles has been carried out by different methods. Using Physical Property Measurement System (PPMS-9 QD) the temperature and magnetic dependency of the susceptibility and magnetization of the nanostuctured aluminates were measured. The obtained results were compared with the existing ones for the single crystals and powder specimens of the same aluminates. The differences observed have been discussed in the framework of the molecular field theory for a two-sublattice system.

  12. Metastable epitaxial magnets: A study of growth and magnetic properties

    NASA Astrophysics Data System (ADS)

    Wu, Stella Zhong

    1997-11-01

    Recent advancement in the information storage industry is demanding more fundamental understanding of magnetic systems, especially the magnetic thin films, surfaces, and interfaces. In this work, we were focusing on ultrathin ferromagnetic thin films of Ni on Cu(100), Cu(110) and Cu(111) single crystal substrates, and FeNi and CoNi binary alloy films on Cu(100) with varying atomic concentration. The growth of these films by molecular beam epitaxy was monitored using a number of experimental techniques. A pseudomorphic layer-by-layer growth was achieved which resulted in an fcc metastable crystalline structure with a ferromagnetic phase. The magnetic anisotropy behavior of these thin films was monitored using surface magneto-optic Kerr effect magnetometer at both polar and longitudinal geometries, and various spin reorientation transitions were found. The measurements of Curie temperature as a variation of film thickness as well as atomic concentration resulted in the proposal of a finite-size scaling law. By using this scaling law, the bulk Curie temperature for these metastable fcc binary alloys can be extrapolated, showing that Fe atoms exist in a low-spin ferromagnetic phase. In the Ni films, a dimensionality crossover from bulk to a 2-dimensional system at a few monolayer thickness was established. By alloying, we have been able to tune the electron occupation number in the 3d band. Combined with the 3d electronic band structure information we have gained by using ultraviolet photoemission spectroscopy study of these systems at normal emission, a conclusion of continuous band filling in CoNi alloy system was drawn. However, FeNi films show a different behavior at a certain composition. The recent collaboration with synchrotron radiation facility has enabled us to quantitatively characterize the spin moment and orbital moment from each element. An x-ray magnetic circular dichroism (XMCD) study was performed on CoNi alloy system, and resulted in the conclusion of

  13. The symmetry properties of planetary magnetic fields

    SciTech Connect

    Raedler, K.H. ); Ness, N.F. )

    1990-03-01

    This paper provides a comparative study of the geometrical structures of the magnetic fields of Earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For Earth, Jupiter, and Saturn the centered dipole, quadrupole, and octupole contributions are included, while at Uranus, only the dipole and quadrupole contributoins are considered. The magnetic fields are analyzed by decomposing them into those parts which have simple symmetry properties with respect to the rotation axis and the equatorial plane. It is found that there are a number of common features of the magnetic fields of Earth and Jupiter. Compared to Earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis, by now rather well known, but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets. The implications of these results for dynamo models are discussed. With a vgiew to Cowling's theorem the symmetry of the fields is investigated with respect to not only the rotation axis but also to other axes intersecting the plaentary center. Surprisingly, the high degree of asymmetry of the Uranian field that is observed with respect to the rotation axis reduces considerably to being compare to that for Earth or Jupiter when the appropriate axis is employed.

  14. Microstructure and Magnetic Properties of Magnetic Material Fabricated by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Jhong, Kai Jyun; Huang, Wei-Chin; Lee, Wen Hsi

    Selective Laser Melting (SLM) is a powder-based additive manufacturing which is capable of producing parts layer-by-layer from a 3D CAD model. The aim of this study is to adopt the selective laser melting technique to magnetic material fabrication. [1]For the SLM process to be practical in industrial use, highly specific mechanical properties of the final product must be achieved. The integrity of the manufactured components depend strongly on each single laser-melted track and every single layer, as well as the strength of the connections between them. In this study, effects of the processing parameters, such as the space distance of surface morphology is analyzed. Our hypothesis is that when a magnetic product is made by the selective laser melting techniques instead of traditional techniques, the finished component will have more precise and effective properties. This study analyzed the magnitudes of magnetic properties in comparison with different parameters in the SLM process and compiled a completed product to investigate the efficiency in contrast with products made with existing manufacturing processes.

  15. Magnetic colloid by PLA: Optical, magnetic and thermal transport properties

    NASA Astrophysics Data System (ADS)

    Pandey, B. K.; Shahi, A. K.; Gopal, Ram

    2015-08-01

    Ferrofluids of cobalt and cobalt oxide nanoparticles (NPs) have been successfully synthesized using liquid phase-pulse laser ablation (LP-PLA) in ethanol and double distilled water, respectively. The mechanism of laser ablation in liquid media and formation process for Co target in double distilled water (DDW) and ethanol are speculated based on the reactions between laser generated highly nascent cobalt species and vaporized solvent media in a confined high temperature and pressure at the plume-surrounding liquid interface region. Optical absorption, emission, vibrational and rotational properties have been investigated using UV-vis absorption, photoluminescence (PL) and Fourier transform-infra red (FT-IR) spectroscopy, respectively. In this study optical band gap of cobalt oxide ferrofluids has been engineered using different pulse energy of Nd:YAG laser in the range of (2.80-3.60 eV). Vibrating sample magnetometer (VSM) is employed to determine the magnetic properties of ferrofluids of cobalt and cobalt oxide NPs while their thermal conductivities are examined using rotating disc method. Ferrofluids have gained enormous curiosity due to many technological applications, i.e. drug delivery, coolant and heating purposes.

  16. Magnetic Properties of Iron Oxide Nanoparticles Obtained by Laser Evaporation

    NASA Astrophysics Data System (ADS)

    Novoselova, Iu. P.; Samatov, O. M.; Kupriyanova, G. S.; Murzakaev, A. M.; Safronov, A. P.; Kurlyandskaya, G. V.

    2017-01-01

    The paper concentrates on a synthesis of spherical magnetic particles obtained by laser evaporation under various process conditions. Depending on the process conditions, which include the pressure in a process chamber, laser pulse duration, mean laser power, and the type of power gas, the stoichiometry of the material ranges from Fe 2.70 O 4 to Fe 2.84 O 4 , while the average diameter of nanoparticles ranges between 10-23 nm. The nanoparticles have an inverse spinel structure. In terms of the magnetic properties, the samples are a superparamagnetic ensemble. The spherical shape of the majority of nanoparticles as well as the existence of merely one magnetic phase are verified by the characteristics of microwave absorption. A relatively high saturation magnetization and a narrow size distribution of small nanoparticles obtained at 700 mmHg working pressure, 100 ms pulse duration, and 200 W laser power allow the authors to consider these conditions to be the most optimum for the nanopowder synthesis and recommend them for biological applications.

  17. Effects Of Hydrothermal Alteration On Magnetic Properties And Magnetic Signatures - Implications For Predictive Magnetic Exploration Models

    NASA Astrophysics Data System (ADS)

    Clark, D.

    2012-12-01

    Magnetics is the most widely used geophysical method in hard rock exploration and magnetic surveys are an integral part of exploration programs for many types of mineral deposit, including porphyry Cu, intrusive-related gold, volcanic-hosted epithermal Au, IOCG, VMS, and Ni sulfide deposits. However, the magnetic signatures of ore deposits and their associated mineralized systems are extremely variable and exploration that is based simply on searching for signatures that resemble those of known deposits and systems is rarely successful. Predictive magnetic exploration models are based upon well-established geological models, combined with magnetic property measurements and geological information from well-studied deposits, and guided by magnetic petrological understanding of the processes that create, destroy and modify magnetic minerals in rocks. These models are designed to guide exploration by predicting magnetic signatures that are appropriate to specific geological settings, taking into account factors such as tectonic province; protolith composition; post-formation tilting/faulting/ burial/ exhumation and partial erosion; and metamorphism. Patterns of zoned hydrothermal alteration are important indicators of potentially mineralized systems and, if properly interpreted, can provided vectors to ore. Magnetic signatures associated with these patterns at a range of scales can provide valuable information on prospectivity and can guide drilling, provided they are correctly interpreted in geological terms. This presentation reviews effects of the important types of hydrothermal alteration on magnetic properties within mineralized systems, with particular reference to porphyry copper and IOCG deposits. For example, an unmodified gold-rich porphyry copper system, emplaced into mafic-intermediate volcanic host rocks (such as Bajo de la Alumbrera, Argentina) exhibits an inner potassic zone that is strongly mineralized and magnetite-rich, which is surrounded by an outer

  18. A Study of Magnetic Properties of Magnetotactic Bacteria

    PubMed Central

    Wajnberg, E.; de Souza, L. H. Salvo; de Barros, Henrique G. P. Lins; Esquivel, Darci M. S.

    1986-01-01

    The first direct measurements of magnetic properties of magnetotactic bacteria from natural samples are presented. Measurements were made at 4.2 K, using a Superconducting Quantum Interfering Device (SQUID) magnetometer. From the magnetization results an anisotropy is obtained that is typical of magnetized ferro- or ferri-magnetic materials. The average magnetic moment of the bacteria determined from the results is in good agreement with the estimated moment from electron microscopy. ImagesFIGURE 2 PMID:19431685

  19. Magnetic Properties of the Chelyabinsk meteorite

    NASA Astrophysics Data System (ADS)

    Bezaeva, N. S.; Badyukov, D. D.; Nazarov, M. A.; Rochette, P.; Feinberg, J. M.

    2013-12-01

    The Chelyabinsk meteorite (the fall of February 15, 2013; Russia) is a LL5 ordinary chondrite. Numerous (thousands) stones fell as a shower to the south and the south-west of the city of Chelyabinsk. The stones consist of two intermixed lithologies, with the majority (2/3) being a light lithology with a typical chondritic texture and shock stage S4 (~30 GPa). The second lithology (1/3) is an impact melt breccia (IMB) consisting of blackened chondrite fragments embedded in a fine-grained matrix. We investigated the magnetic properties of the meteorite stones collected immediately after the fall by the expedition of the Vernadsky Institute, Moscow. The low-field magnetic susceptibility (χ0) of 174 fragments (135 chondritic and 39 IMB) weighing >3 g was measured. Each sample was measured three times in mutually perpendicular directions to average anisotropy. Also hysteresis loops (saturation magnetization Ms, coercivity Bc) and back-field remanence demagnetization curves (coercivity of remanence Bcr) in the temperature range from 10K to 700°C and other characteristics of some pieces (NRM, SIRM with their thermal and alternating field demagnetization spectra) were acquired. The mean logχ0 is 4.57×0.09 (s.d.) for the light lithology and 4.65×0.09 (s.d.) (×10-9 m3/kg) for the IMB, indicating that IMB is slightly richer in metal than the light chondritic lithology. According to [1], Chelyabinsk is three times more magnetic than the average LL5 fall, but similar to other metal-rich LL5 (e.g., Paragould, Aldsworth, Bawku, Richmond), as well as L/LL chondrites (e.g., Glanerbrug, Knyahinya, Qidong). The estimation of metal content from the Ms value gives 3.7 wt.% for the light fragments and 4.1 wt.% for IMB whereas the estimation from χ0 yields overestimated contents, e.g., 6.9 wt.% for the light lithology. Thermomagnetic curves Ms(T) up to 800°C identify the main magnetic carriers at room temperature (T0) and above as taenite and kamacite (no tetrataenite found), in

  20. Magnetic properties and heavy-metal contents of contaminated seabed sediments of Penny's Bay, Hong Kong.

    PubMed

    Chan, L S; Ng, S L; Davis, A M; Yim, W W; Yeung, C H

    2001-07-01

    Magnetic properties and heavy-metal concentrations of vibrocore samples were found to be potential indicators of shipping contamination in seabed sediments in Hong Kong Harbour. Geochemical results of 74 vibrocores located off Penny's Bay on Lantau Island revealed an enrichment of heavy metals in the upper 1-2 m of the cores within the eastern part of the study site. Whole-core magnetic susceptibility measurements also showed a greater concentration of magnetic particles in the surficial layer of these cores. A significant correlation exists between the magnetic susceptibility and the concentrations of Pb, Zn and Cu, as well as the Tomlinson pollution load index (PLI). The proximity of these cores to a major navigation fairway and an anchorage site suggests probable contamination of the surficial seabed sediments by shipping-related wastes. A study of the magnetic properties of one of the cores, VT60, revealed a difference in the magnetic properties between the contaminated and the uncontaminated sediments. Samples from the contaminated zone exhibited relatively stronger magnetic remanence and susceptibility. The two groups of samples also formed distinct trends on the hysteresis ratios plot. A level of unusually high magnetic susceptibility within the contaminated zone was attributable to the presence of strongly magnetized granules, which were probably refuse from shipping-related activities. Geochemical and magnetic results were also conducted on samples of different size-fractions from this core. The < 63 microns fraction was found to contain a relatively higher magnetic susceptibility and greater heavy-metal content.

  1. Magnetic and magnetoelastic properties of amorphous ribbons

    SciTech Connect

    Chiriac, H.; Ciobotaru, I.; Mohorianu, S.

    1994-03-01

    A phenomenological model for the magnetic and magnetoelastic behavior of the field-annealed magnetostrictive ribbon is proposed. The basic hypothesis is that the magnetic domain coupling energy due to the inhomogeneity inherent to amorphous state is dependent on the reduced magnetization. The model takes into account the anisotropy energy, Zeeman energy, magnetoelastic energy and magnetic domain coupling energy. The magnetization, engineering magnetostriction and Young`s modulus are derived as continuous functions of the applied magnetic field and stress.

  2. Hot magnetized nuclear matter: Thermodynamic and saturation properties

    NASA Astrophysics Data System (ADS)

    Rezaei, Z.; Bordbar, G. H.

    2017-03-01

    We have used a realistic nuclear potential, AV_{18}, and a many-body technique, the lowest-order constraint variational (LOCV) approach, to calculate the properties of hot magnetized nuclear matter. By investigating the free energy, spin polarization parameter, and symmetry energy, we have studied the temperature and magnetic field dependence of the saturation properties of magnetized nuclear matter. In addition, we have calculated the equation of state of magnetized nuclear matter at different temperatures and magnetic fields. It was found that the flashing temperature of nuclear matter decreases by increasing the magnetic field. In addition, we have studied the effect of the magnetic field on liquid gas phase transition of nuclear matter. The liquid gas coexistence curves, the order parameter of the liquid gas phase transition, and the properties of critical point at different magnetic fields have been calculated.

  3. Hexaferrite M (Co, Ti) magnetic properties optimization

    SciTech Connect

    Autissier, D.; Rousselle, D.; Podembski, A.

    1995-09-01

    Barium hexaferrites are anisotropic iron oxides which can present high values of permeability. We have studied Ba (Co, Ti){sub x}Fe{sub 12-2x}O{sub 19} compositions. Powders are synthesized using the ceramic method: stoichiometric amounts of basic components are ground and fired at high temperature (1170{degrees}C) to obtain the desired phase. The powders are then ground for 6 hours in order to reduce the particle size. The slurry is cast in a plaster matrix. This matrix is rotated between the poles of a stationary electromagnet. Fields of approximately 500 Oe are used for the orientation procedure. Samples are then sintered for different temperatures between 1200 and 1300{degrees}C. We present results (magnetization, permeability, permittivity, orientation rate) obtained for diverse compositions (1.1magnetic properties, orientation rate, microstructure.

  4. Magnetic Properties of Lunar Geologic Terranes: New Statistical Results

    NASA Technical Reports Server (NTRS)

    Halekas, J. S.; Mitchell, D. L.; Lin, R. P.; Frey, S.; Hood, L. L.; Acuna, M. H.; Binder, A.

    2002-01-01

    We use global magnetic field data and digitized geologic maps to determine the magnetic properties of lunar terranes. Average fields vary by a factor of 100 from demagnetized impact basins and craters to strongly magnetized antipodal regions. Additional information is contained in the original extended abstract.

  5. Magnetic properties of frictional volcanic materials

    NASA Astrophysics Data System (ADS)

    Kendrick, Jackie E.; Lavallée, Yan; Biggin, Andrew; Ferk, Annika; Leonhardt, Roman

    2015-04-01

    During dome-building volcanic eruptions, highly viscous magma extends through the upper conduit in a solid-like state. The outer margins of the magma column accommodate the majority of the strain, while the bulk of the magma is able to extrude, largely undeformed, to produce magma spines. Spine extrusion is often characterised by the emission of repetitive seismicity, produced in the upper <1 km by magma failure and slip at the conduit margins. The rheology of the magma controls the depth at which fracture can occur, while the frictional properties of the magma are important in controlling subsequent marginal slip processes. Upon extrusion, spines are coated by a carapace of volcanic fault rocks which provide insights into the deeper conduit processes. Frictional samples from magma spines at Mount St. Helens (USA), Soufriere Hills (Montserrat) and Mount Unzen (Japan) have been examined using structural, thermal and magnetic analyses to reveal a history of comminution, frictional heating, melting and cooling to form volcanic pseudotachylyte. Pseudotachylyte has rarely been noted in volcanic materials, and the recent observation of its syn-eruptive formation in dome-building volcanoes was unprecedented. The uniquely high thermal conditions of volcanic environments means that frictional melt remains at elevated temperatures for longer than usual, causing slow crystallisation, preventing the development of some signature "quench" characteristics. As such, rock-magnetic tests have proven to be some of the most useful tools in distinguishing pseudotachylytes from their andesite/ dacite hosts. In volcanic pseudotachylyte the mass normalised natural remanent magnetisation (NRM) when further normalised with the concentration dependent saturation remanence (Mrs) was found to be higher than the host rock. Remanence carriers are defined as low coercive materials across all samples, and while the remanence of the host rock displays similarities to an anhysteretic remanent

  6. Effect of high magnetic field on structure and magnetic properties of evaporated crystalline and amorphous Fe-Sm thin films

    NASA Astrophysics Data System (ADS)

    Li, Guojian; Li, Mengmeng; Wang, Jianhao; Du, Jiaojiao; Wang, Kai; Wang, Qiang

    2017-02-01

    Crystalline and amorphous Fe-Sm thin films have been fabricated by using molecular beam vapor deposition method. Then, the effects of both variation of Sm content and application of high magnetic field during film growth on the structure and magnetic properties of the Fe-Sm films have been explored. The results show that bcc structure of the Fe-Sm films with 5.8% Sm transforms to amorphization with 33.0% Sm. Meanwhile, nanocrystallite is formed in the amorphous Fe-Sm films. However, no Fe-Sm compound exists with the change of Sm content and with the application of high magnetic field. Nevertheless, high magnetic field decreases interplanar spacing. The structural evolution has a significant effect on magnetic properties. Saturation magnetization decreases 290% from 1456 emu/cm3 to 373 emu/cm3 with the increase of Sm content from 5.8% to 33.0%. The coercivity increases 1225% from 20 Oe to 265 Oe. Meanwhile, both the saturation magnetization and coercivity of the films decrease with the application of high magnetic field. The reason has been discussed.

  7. Magnetic properties of biomineral particles produced by bacteria Klebsiella oxytoca

    NASA Astrophysics Data System (ADS)

    Raĭkher, Yu. L.; Stepanov, V. I.; Stolyar, S. V.; Ladygina, V. P.; Balaev, D. A.; Ishchenko, L. A.; Balasoiu, M.

    2010-02-01

    Ferrihydrite nanoparticles (2-5 nm in size) produced by bacteria Klebsiella oxytoca in the course of biomineralization of iron salt solutions from a natural medium exhibit unique magnetic properties: they are characterized by both the antiferromagnetic order inherent in a bulk ferrihydrite and the spontaneous magnetic moment due to the decompensation of spins in sublattices of a nanoparticle. The magnetic susceptibility enhanced by the superantiferromagnetism effect and the magnetic moment independent of the magnetic field provide the possibility of magnetically controlling these natural objects. This has opened up the possibilities for their use in nanomedicine and bioengineering. The results obtained from measurements of the magnetic properties of the ferrihydrite produced by Klebsiella oxytoca in its two main crystalline modifications are reported, and the data obtained are analyzed theoretically. This has made it possible to determine numerical values of the magnetic parameters of real biomineral nanoparticles.

  8. Modeling of magnetic properties of polymer bonded Nd-Fe-B magnets with surface modifications

    NASA Astrophysics Data System (ADS)

    Xiao, Jun; Otaigbe, Joshua U.; Jiles, David C.

    2000-07-01

    The effects of surface modification on the magnetic properties of polymer-bonded Nd-Fe-B magnets have been studied. Two sets of Nd-Fe-B powders, coated and uncoated, were blended and compression molded with polyphenylene sulfide in isotropic form. Their magnetic properties were measured using a Helmholtz coil and a SQUID. The results showed that the effect of the coating significantly improved the irreversible loss in flux and energy product of the polymer-bonded magnets. The results have been interpreted using an isotropic model of hysteresis that takes into account energy losses. The modeling showed that the presence of soft magnetic materials in the Nd-Fe-B powders caused by oxidation reduces the interaction among magnetic particles, however, the coating treatment alters the magnetic properties by increasing the remanence of polymer-bonded magnets via increasing the interparticle coupling coefficient.

  9. Magnetic properties of superconducting Bi/Ni bilayers

    NASA Astrophysics Data System (ADS)

    Zhou, Hexin; Gong, Xinxin; Jin, Xiaofeng

    2017-01-01

    The magnetic properties of an unexpected superconducting bilayer consisting of non-superconducting Bi and ferromagnetic Ni have been investigated. A large magnetization signal is observed when the sample is cooled below the superconducting transition temperature in zero magnetic field, which has the same direction with the magnetization of the adjacent Ni layer. Interestingly, this Bi/Ni bilayer shows opposite responses to external magnetic field in zero field cooling (ZFC) process and field cooling (FC) process. It behaves diamagnetically in ZFC while paramagnetically in FC. Besides, magnetic hysteresis loops below the superconducting transition temperature show flux pinning and flux jumping effects.

  10. Magnetic Properties of Strontium Hexaferrite Nanostructures Measured with Magnetic Force Microscopy

    PubMed Central

    Li, Qiang; Song, Jie; Saura-Múzquiz, Matilde; Besenbacher, Flemming; Christensen, Mogens; Dong, Mingdong

    2016-01-01

    Magnetic property is one of the important properties of nanomaterials. Direct investigation of the magnetic property on the nanoscale is however challenging. Herein we present a quantitative measurement of the magnetic properties including the magnitude and the orientation of the magnetic moment of strontium hexaferrite (SrFe12O19) nanostructures using magnetic force microscopy (MFM) with nanoscale spatial resolution. The measured magnetic moments of the as-synthesized individual SrFe12O19 nanoplatelets are on the order of ~10−16 emu. The MFM measurements further confirm that the magnetic moment of SrFe12O19 nanoplatelets increases with increasing thickness of the nanoplatelet. In addition, the magnetization directions of nanoplatelets can be identified by the contrast of MFM frequency shift. Moreover, MFM frequency imaging clearly reveals the tiny magnetic structures of a compacted SrFe12O19 pellet. This work demonstrates the mesoscopic investigation of the intrinsic magnetic properties of materials has a potential in development of new magnetic nanomaterials in electrical and medical applications. PMID:27174466

  11. Magnetic Properties of Strontium Hexaferrite Nanostructures Measured with Magnetic Force Microscopy.

    PubMed

    Li, Qiang; Song, Jie; Saura-Múzquiz, Matilde; Besenbacher, Flemming; Christensen, Mogens; Dong, Mingdong

    2016-05-13

    Magnetic property is one of the important properties of nanomaterials. Direct investigation of the magnetic property on the nanoscale is however challenging. Herein we present a quantitative measurement of the magnetic properties including the magnitude and the orientation of the magnetic moment of strontium hexaferrite (SrFe12O19) nanostructures using magnetic force microscopy (MFM) with nanoscale spatial resolution. The measured magnetic moments of the as-synthesized individual SrFe12O19 nanoplatelets are on the order of ~10(-16) emu. The MFM measurements further confirm that the magnetic moment of SrFe12O19 nanoplatelets increases with increasing thickness of the nanoplatelet. In addition, the magnetization directions of nanoplatelets can be identified by the contrast of MFM frequency shift. Moreover, MFM frequency imaging clearly reveals the tiny magnetic structures of a compacted SrFe12O19 pellet. This work demonstrates the mesoscopic investigation of the intrinsic magnetic properties of materials has a potential in development of new magnetic nanomaterials in electrical and medical applications.

  12. Magnetic Properties of Strontium Hexaferrite Nanostructures Measured with Magnetic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Song, Jie; Saura-Múzquiz, Matilde; Besenbacher, Flemming; Christensen, Mogens; Dong, Mingdong

    2016-05-01

    Magnetic property is one of the important properties of nanomaterials. Direct investigation of the magnetic property on the nanoscale is however challenging. Herein we present a quantitative measurement of the magnetic properties including the magnitude and the orientation of the magnetic moment of strontium hexaferrite (SrFe12O19) nanostructures using magnetic force microscopy (MFM) with nanoscale spatial resolution. The measured magnetic moments of the as-synthesized individual SrFe12O19 nanoplatelets are on the order of ~10-16 emu. The MFM measurements further confirm that the magnetic moment of SrFe12O19 nanoplatelets increases with increasing thickness of the nanoplatelet. In addition, the magnetization directions of nanoplatelets can be identified by the contrast of MFM frequency shift. Moreover, MFM frequency imaging clearly reveals the tiny magnetic structures of a compacted SrFe12O19 pellet. This work demonstrates the mesoscopic investigation of the intrinsic magnetic properties of materials has a potential in development of new magnetic nanomaterials in electrical and medical applications.

  13. Magnetic properties of hybrid elastomers with magnetically hard fillers: rotation of particles

    NASA Astrophysics Data System (ADS)

    Stepanov, G. V.; Borin, D. Yu; Bakhtiiarov, A. V.; Storozhenko, P. A.

    2017-03-01

    Hybrid magnetic elastomers belonging to the family of magnetorheological elastomers contain magnetically hard components and are of the utmost interest for the development of semiactive and active damping devices as well as actuators and sensors. The processes of magnetizing of such elastomers are accompanied by structural rearrangements inside the material. When magnetized, the elastomer gains its own magnetic moment resulting in changes of its magneto-mechanical properties, which remain permanent, even in the absence of external magnetic fields. Influenced by the magnetic field, magnetized particles move inside the matrix forming chain-like structures. In addition, the magnetically hard particles can rotate to align their magnetic moments with the new direction of the external field. Such an elastomer cannot be demagnetized by the application of a reverse field.

  14. Magnetic properties of Ho1- x Lu x B12 solid solutions

    NASA Astrophysics Data System (ADS)

    Gabáni, S.; Gaz̆o, E.; Pristás̆, G.; Takác̆ová, I.; Flachbart, K.; Shitsevalova, N.; Siemensmeyer, K.; Sluchanko, N.

    2013-05-01

    Magnetic properties of the geometrically frustrated antiferromagnet HoB12 (with T N = 7.4 K) modified by substitution of magnetic Ho atoms through non-magnetic Lu ones are presented and discussed. In this case, in Ho1- x Lu x B12 solid solutions, both chemical pressure resulting from different Lu3+ and Ho3+ radii and magnetic dilution take place with increasing Lu content ( x) that change properties of the system. The received results show strong indication for the existence of a quantum critical point near x = 0.9, which separates the region of magnetic order (starting with HoB12 for x = 0) and the nonmagnetic region (ending with superconducting LuB12 for x = 1).

  15. Magnetism in nanoparticles: tuning properties with coatings.

    PubMed

    Crespo, Patricia; de la Presa, Patricia; Marín, Pilar; Multigner, Marta; Alonso, José María; Rivero, Guillermo; Yndurain, Félix; González-Calbet, José María; Hernando, Antonio

    2013-12-04

    This paper reviews the effect of organic and inorganic coatings on magnetic nanoparticles. The ferromagnetic-like behaviour observed in nanoparticles constituted by materials which are non-magnetic in bulk is analysed for two cases: (a) Pd and Pt nanoparticles, formed by substances close to the onset of ferromagnetism, and (b) Au and ZnO nanoparticles, which were found to be surprisingly magnetic at the nanoscale when coated by organic surfactants. An overview of theories accounting for this unexpected magnetism, induced by the nanosize influence, is presented. In addition, the effect of coating magnetic nanoparticles with biocompatible metals, oxides or organic molecules is also reviewed, focusing on their applications.

  16. Magnetic and mechanical properties of a finite-thickness superconducting strip with a cavity in oblique magnetic fields

    NASA Astrophysics Data System (ADS)

    Huang, Chen-Guang; Liu, Jun

    2017-01-01

    This paper presents an investigation of the mechanical response of a finite-thickness superconducting strip containing an elliptical cavity in oblique magnetic fields. After the Bean critical state model and the minimum magnetic energy variation procedure are employed, the dependency of the magnetic and mechanical properties on the aspect ratio of the strip and the tilt angles of the applied field and elliptical cavity is discussed. The results show that for a strip in an oblique magnetic field, the current front penetrates non-monotonically from the surface inwards in the initial stage. The magnetization of the strip and the applied field are not collinear, and the angle between them becomes smaller with increasing field. Simultaneously, the strip suffers from a torque produced by the electromagnetic force and then has a tendency to rotate. Compared with the defect-free case, the appearance of the elliptical cavity affects the magnetic property of the strip and further causes significant stress concentration. If the tilt angle of the elliptical cavity is small, a position of stable mechanical equilibrium will exist for the strip. It is interesting that due to the elliptical cavity effect, an oblique magnetization and a non-zero torque are generated even if the applied field is perpendicular or parallel to the strip.

  17. Electronic and magnetic properties of nanoribbons

    NASA Astrophysics Data System (ADS)

    Fernando, Gayanath; Zhang, Zhiwei; Kocharian, Armen

    We have performed tight-binding calculations with open boundary conditions on a set of twisted nanoribbons (4x100), monitoring the band structure as a function of the twist angle θ. When this angle is zero, the ribbon is rectangular and when it is 60 degrees, the ribbon is cut from a honeycomb lattice. Depending on the parameters of the tight-binding model and the filling factor, semi-metallic or insulating behavior is observed. We have also studied the electronic structure of such ribbons due to the adsorption of small atoms such as nitrogen, a magnetic field and the Rashba spin-orbit interaction. The role of the adsorbed atoms and the Rashba term with regard to the conducting properties and the symmetry breaking of the ribbons will be discussed in some detail. In addition, the effects of electronic correlations on selected small ribbons will be examined. The authors acknowledge the computing facilities provided by the Center for Functional Nanomaterials, Brookhaven National Laboratory supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

  18. Magnetic properties of Pr ions in perovskite-type oxides

    NASA Astrophysics Data System (ADS)

    Sekizawa, K.; Kitagawa, M.; Takano, Y.

    1998-01-01

    Magnetic properties of Pr ions with the controlled valence on the A and B sites of perovskite-type oxides (ABO 3) were investigated for two systems, PrSc 1 - xMg xO 3 and BaPr 1 - xBi xO 3. From the magnetic susceptibility χ versus temperature T curves of PrSc 1 - xMg xO 3, the χ-T curve for molar Pr 3+ ions on the A site and that of Pr 4+ ions were obtained. The 1/χ-T curves for both ions exhibit the crystalline electric field (CEF) effect and the effective magnetic moment μ eff above 100 K is 3.41 μ B for Pr 3+ and 2.58 μ B for Pr 4+, respectively. The χ-T curve of PrSc 0.8Mg 0.2O 3 is similar to that of PrBa 2Cu 3O y. In the BaPr 1 - xBi xO 3 system, only one intermediate phase BaPr 0.5Bi 0.5O 3 exists, in which Pr and Bi take an ordered arrangement on the B site. The magnetic susceptibility χ for Pr 4+ and that of Pr 3- in the ordered arrangement with Bi 5+ on the B site are much smaller than those for the A site, reflecting the strong CEF effect on the B site. Experimental χ-T curves can be well reproduced by the numerical calculation for Pr 3+ or Pr 4+ ions in the molecular field and the CEF with proper respective parameters.

  19. Magnetic properties of nanocomposites formed by magnetic nanoparticles embedded in a non-magnetic matrix: a simulation approach.

    PubMed

    Serna, J Ceballos; Restrepo-Parra, E; Rojas, J C Riaño

    2012-06-01

    In this work, simulations of magnetic properties of nanocomposites formed by magnetic nanoparticles embedded in a non magnetic matrix are presented. These simulations were carried by means of the Monte Carlo Method and Heisenberg model. Properties as magnetization and Hysteresis loops were obtained varying different parameters as the nanoparticle size, distance between nanoparticles and temperature. The model employed includes interaction between ions belonging to each nanoparticle and also the interaction between nanoparticles. Results show that the magnetization and the coercive force decrease as a function of the nanoparticles distance.

  20. Dipolar interaction effects in the magnetic and magnetotransport properties of ordered nanoparticle arrays.

    PubMed

    Kechrakos, D; Trohidou, K N

    2008-06-01

    Assemblies of magnetic nanoparticles exhibit interesting physical properties arising from the competition of intraparticle dynamics and interparticle interactions. In ordered arrays of magnetic nanoparticles magnetostatic interparticle interactions introduce collective dynamics acting competitively to random anisotropy. Basic understanding, characterization and control of dipolar interaction effects in arrays of magnetic nanoparticles is an issue of central importance. To this end, numerical simulation techniques offer an indispensable tool. We report on Monte Carlo studies of the magnetic hysteresis and spin-dependent transport in thin films formed by ordered arrays of magnetic nanoparticles. Emphasis is given to the modifications of the single-particle behavior due to interparticle dipolar interactions as these arise in quantities of experimental interest, such as, the magnetization, the susceptibility and the magnetoresistance. We investigate the role of the structural parameters of an array (interparticle separation, number of stacked monolayers) and the role of the internal structure of the nanoparticles (single phase, core-shell). Dipolar interactions are responsible for anisotropic magnetic behavior between the in-plane and out-of-plane directions of the sample, which is reflected on the investigated magnetic properties (magnetization, transverse susceptibility and magnetoresistance) and the parameters of the array (remanent magnetization, coercive field, and blocking temperature). Our numerical results are compared to existing measurements on self-assembled arrays of Fe-based and Co nanoparticles is made.

  1. Constraining the existence of magnetic monopoles by Dirac-dual electric charge renormalization effect under the Planck scale limit

    NASA Astrophysics Data System (ADS)

    Deng, Yanbin; Huang, Changyu; Huang, Yong-Chang

    2016-08-01

    It was suggested by dimensional analysis that there exists a limit called the Planck energy scale coming close to which the gravitational effects of physical processes would inflate and struggle for equal rights so as to spoil the validity of pure nongravitational physical theories that governed well below the Planck energy. Near the Planck scale, the Planck charges, Planck currents, or Planck parameters can be defined and assigned to physical quantities such as the single particle electric charge and magnetic charge as the ceiling value obeyed by the low energy ordinary physics. The Dirac electric-magnetic charge quantization relation as one form of electric-magnetic duality dictates that, the present low value electric charge corresponds to a huge magnetic charge value already passed the Planck limit so as to render theories of magnetic monopoles into the strong coupling regime, and vice versa, that small and tractable magnetic charge values correspond to huge electric charge values. It suggests that for theoretic models in which the renormalization group equation provides rapid growth for the running electric coupling constant, it is easier for the dual magnetic monopoles to emerge at lower energy scales. Allowing charges to vary with the Dirac electric-magnetic charge quantization relation while keeping values under the Planck limit informs that the magnetic charge value drops below the Planck ceiling value into the manageable region when the electric coupling constant grows to one fourth at a model dependent energy scale, and continues dropping toward half the value of the Planck magnetic charge as the electric coupling constant continues growing at the model dependent rate toward one near Planck energy scale.

  2. Measurement and modelling of magnetic properties of soft magnetic composite material under 2D vector magnetisations

    NASA Astrophysics Data System (ADS)

    Guo, Y. G.; Zhu, J. G.; Zhong, J. J.

    2006-07-01

    This paper reports the measurement and modelling of magnetic properties of SOMALOY TM 500, a soft magnetic composite (SMC) material, under different 2D vector magnetisations, such as alternating along one direction, circularly and elliptically rotating in a 2D plane. By using a 2D magnetic property tester, the B- H curves and core losses of the SMC material have been measured with different flux density patterns on a single sheet square sample. The measurements can provide useful information for modelling of the magnetic properties, such as core losses. The core loss models have been successfully applied in the design of rotating electrical machines with SMC core.

  3. Magnetic properties of stainless steels at room and cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Oxley, Paul; Goodell, Jennifer; Molt, Robert

    2009-07-01

    The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room temperature and at 77 K. The steel samples studied were in the annealed state as received from the manufacturer. Our room temperature measurements indicate significantly harder magnetic properties than those quoted in the ASM International Handbook, which studied fully annealed stainless steel samples. Despite having harder magnetic properties than fully annealed steels some of the as-received steels still display soft magnetic properties adequate for magnetic applications. The carbon content of the steels was found to affect the permeability and coercive force, with lower-carbon steels displaying significantly higher permeability and lower coercive force. The decrease in coercive force with reduced carbon content is attributed to fewer carbide inclusions which inhibit domain wall motion. Cooling to 77 K resulted in harder magnetic properties. Averaged over the ten steels tested the maximum permeability decreased by 8%, the coercive force increased by 14%, and the residual and saturation flux densities increased by 4% and 3%, respectively. The change in coercive force when cooled is comparable to the theoretical prediction for iron, based on a model of domain wall motion inhibited by inclusions. The modest changes of the magnetic properties indicate that the stainless steels can still be used in magnetic applications at very low temperatures.

  4. The electric properties of low-magnetic-loss magnetic composites containing Zn-Ni-Fe particles

    NASA Astrophysics Data System (ADS)

    Hidaka, Nobuhiro; Ishitsuka, Masayuki; Shirakata, Yasushi; Teramoto, Akinobu; Ohmi, Tadahiro

    2009-10-01

    Recently, magnetic composites consisting of magnetic particles dispersed in a polymer matrix have been widely discussed for miniaturizing high-frequency electronic components such as antennae. Previously, we investigated the influence of the manufacturing process on the homogeneous dispersion of magnetic particles in the polymer and on the magnetic properties of the magnetic composites. In order to miniaturize electronic components, it is crucial to be able to independently control the permeability and permittivity in magnetic composites. This paper investigates the anisotropy and frequency dependence of the dielectric properties of magnetic composites fabricated from 20 vol% Zn5Ni75Fe20 flaked particles. The permittivity of magnetic composites fabricated from Zn5Ni75Fe20 flaked particles is anisotropic: at 1 GHz, the relative permittivities parallel and perpendicular to the plane of the specimens are 27.2 and 16.9, respectively. The permittivity varied little between frequencies of 50 MHz and 10 GHz.

  5. Temperature effect on the magnetic property and ferroelectricity in hexaferrite SrFe12O19

    NASA Astrophysics Data System (ADS)

    Qiang, Gang; Jin, Yuan; Lu, Xiaowen; Cui, Xiaopeng; Deng, Dongmei; Kang, Baojuan; Yang, Wuguo; Cao, Shixun; Zhang, Jincang

    2016-07-01

    We studied the temperature effect on magnetic and electrical properties in bulk SrFe12O19 prepared by conventional ceramic technique. The jumping behavior of magnetization has been observed under the zero-field-cooling mode, but disappeared under the field-cooled cooling mode. The spin moment of iron ions reorients below 50 K leading to the magnetic structure changes. Magnetic parameters, saturation magnetization (Ms) and coercivity field (Hc), show opposite tendency with temperature throughout the measuring range, which is mainly ascribed to the Fe3+ ions situated at 4f2 and 2b sites. The curves of electrical polarization P vs temperature T under different external magnetic field indicate the existence of ferroelectricity and magnetoelectric coupling effect at low temperature, and the transition temperature T P is about 120 K.

  6. Correlation of magnetic properties with deformation in electrical steels

    NASA Astrophysics Data System (ADS)

    Papadopoulou, S.

    2016-03-01

    This paper investigates the utilization of magnetic Barkhausen Noise (MBN) and hysteresis loops methods for the non-destructive characterization of deformed electrical steel samples. For this reason electrical steel samples were subjected to uniaxial tensile tests on elastic and plastic region of deformations. Both the MBN and hysteresis loops were measured. The results shown a strong degradation of the magnetic properties on plastically strains. This was attributed to the irreversible movement of the magnetic domain walls, due to the presence of high dislocation density. The resulting magnetic properties were further evaluated by examining the microstructure of the deformed samples by using scanning electron microscopy.

  7. Structure and magnetic properties of Zn-Ti-substituted Ba-ferrite particles for magnetic recording

    NASA Astrophysics Data System (ADS)

    Wang, C. S.; Wei, F. L.; Lu, M.; Han, D. H.; Yang, Z.

    1998-03-01

    The formation process of Zn-Ti-doped Ba-ferrite particles was investigated by the X-ray diffraction technique, transmission electron microscope and magnetic measurements. The effects of heating temperature Th and the Zn-Ti substitution x on the microstructure and magnetic properties of BaFe 12-2 xZn xTi x O 19 particles with x=0.10-0.80 were studied. The temperature dependence of magnetic properties of these particles was measured.

  8. Magnetic and magnetothermal properties and the magnetic phase diagram of high purity single crystalline terbium along the easy magnetization direction

    SciTech Connect

    Zverev, V. I.; Tishin, A. M.; Chernyshov, A. S.; Mudryk, Ya; Gschneidner Jr., Karl A.; Pecharsky, Vitalij K.

    2014-01-21

    The magnetic and magnetothermal properties of a high purity terbium single crystal have been re-investigated from 1.5 to 350 K in magnetic fields ranging from 0 to 75 kOe using magnetization, ac magnetic susceptibility and heat capacity measurements. The magnetic phase diagram has been refined by establishing a region of the fan-like phase broader than reported in the past, by locating a tricritical point at 226 K, and by a more accurate definition of the critical fields and temperatures associated with the magnetic phases observed in Tb.

  9. Magnetic properties of synthetic eumelanin--preliminary results.

    PubMed

    Cano, M E; Castañeda-Priego, R; Gil-Villegas, A; Sosa, M A; Schio, P; de Oliveira, A J A; Chen, F; Baffa, O; Graeff, C F O

    2008-01-01

    We report an experimental and theoretical study of magnetic properties of synthetic eumelanin. The magnetization curves are determined by using both a vibrating sample magnetometer and a superconducting quantum interferometer device in an extended range of magnetic fields ranging from -10 kOe to 10 kOe at different temperatures. We find that the eumelanin magnetization can be qualitatively explained in terms of a simple model of dipolar spheres with an intrinsic magnetic moment. The latter one is experimentally measured by using X-band electron paramagnetic resonance. Our findings indicate that synthetic melanins are superparamagnetic.

  10. Magnetic Properties of Nanoparticle Matrix Composites

    DTIC Science & Technology

    2015-06-02

    been optimized for each composition of Fe-Pt and their spin isomers have been studied to find the magnetic moments of the lowest energy structures ...numbers in brackets below the structures refer to the energy (eV) relative to the lowest energy isomer and the magnetic moment (µB). Red (blue) balls...Approved for public release; distribution is unlimited. Distribution is unlimited structures . The magnetic moments increase systematically by 4µB when a

  11. Enhancement in magnetic properties of magnesium substituted bismuth ferrite nanoparticles

    SciTech Connect

    Xu, Jianlong; Xie, Dan E-mail: RenTL@mail.tsinghua.edu.cn; Teng, Changjiu; Zhang, Xiaowen; Zhang, Cheng; Sun, Yilin; Ren, Tian-Ling E-mail: RenTL@mail.tsinghua.edu.cn; Zeng, Min; Gao, Xingsen; Zhao, Yonggang

    2015-06-14

    We report a potential way to effectively improve the magnetic properties of BiFeO{sub 3} (BFO) nanoparticles through Mg{sup 2+} ion substitution at the Fe-sites of BFO lattice. The high purity and structural changes induced by Mg doping are confirmed by X-ray powder diffractometer and Raman spectra. Enhanced magnetic properties are observed in Mg substituted samples, which simultaneously exhibit ferromagnetic and superparamagnetic properties at room temperature. A physical model is proposed to support the observed ferromagnetism of Mg doped samples, and the superparamagnetic properties are revealed by the temperature dependent magnetization measurements. The improved magnetic properties and soft nature obtained by Mg doping in BFO nanoparticles demonstrate the possibility of BFO nanoparticles to practical applications.

  12. Enhancement in magnetic properties of magnesium substituted bismuth ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Xu, Jianlong; Xie, Dan; Teng, Changjiu; Zhang, Xiaowen; Zhang, Cheng; Sun, Yilin; Ren, Tian-Ling; Zeng, Min; Gao, Xingsen; Zhao, Yonggang

    2015-06-01

    We report a potential way to effectively improve the magnetic properties of BiFeO3 (BFO) nanoparticles through Mg2+ ion substitution at the Fe-sites of BFO lattice. The high purity and structural changes induced by Mg doping are confirmed by X-ray powder diffractometer and Raman spectra. Enhanced magnetic properties are observed in Mg substituted samples, which simultaneously exhibit ferromagnetic and superparamagnetic properties at room temperature. A physical model is proposed to support the observed ferromagnetism of Mg doped samples, and the superparamagnetic properties are revealed by the temperature dependent magnetization measurements. The improved magnetic properties and soft nature obtained by Mg doping in BFO nanoparticles demonstrate the possibility of BFO nanoparticles to practical applications.

  13. Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

    NASA Astrophysics Data System (ADS)

    Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

    2011-04-01

    Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH)max of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

  14. Material properties of hollow clay tile and existing mortar characterization study

    SciTech Connect

    Butala, M.B.; Jones, W.D.

    1993-10-01

    Several Buildings at the Department of Energy (DOE) Oak Ridge Y-12 Plant were constructed (circa 1950) using unreinforced hollow clay tile (UHCT) masonry walls, which act as shear walls to resist lateral forces. A comprehensive test program, managed by the Center for Natural Phenomena Engineering (CNPE) of Martin Marietta Energy Systems, Inc. (MMES), is under way to determine material properties of existing hollow clay tile walls that will be used to help determine the structural strength of those buildings. This paper presents the results of several types of material property tests of 4-in.- and 8-in.-thick hollow clay tiles. These tests include determination of weight, size, void area, net area and gross area, initial rate of absorption, absorption, modules of rupture, splitting tensile strength, and compressive strength. The tests were performed on old, reclaimed tiles and new tiles. A total of 336 tiles were tested. The stress-strain relationship for 40 specimens was also obtained. All testing was performed in accordance with ASTM standards and procedures developed by CNPE. This paper also presents the results of an investigation of mortar removed from the existing walls. The mortar characterization study was performed by Testwell Craig Materials Consultants (TCMC) under subcontract to MMES. Petrographic and chemical investigations were conducted on 18 mortar samples removed from four buildings at the plant. The primary purpose of the investigations was to evaluate the properties of existing mortar and provide a similar specification for the mortar to be used for construction of test specimens and test walls for the test program. The study showed variability in the mortars among buildings and among different locations within a building; it was concluded that an average mortar mix conforming to ASTM type N proportioned by volume of Portland cement, hydrated lime, and Tennessee river sand would be used to conduct further laboratory studies of masonry assemblages.

  15. Using existing data to estimate aquifer properties, Great Lakes Region, USA

    USGS Publications Warehouse

    Darner, Robert A.; Sheets, Rodney A.

    2012-01-01

    To determine specific storage and porosity, areally limited and time-consuming aquifer tests are frequently done. Hydrogeologic studies often do not have the resources to collect such data and rely on existing data sources for aquifer properties. An alternative tool for determining these aquifer properties is the analysis of earth tides. The objective of this study was to determine whether existing water-level and barometric-pressure data could be used to determine aquifer properties, such as porosity and specific storage, on a regional scale. In this study, national databases from the Great Lakes Region were queried for continuous records of groundwater-level and barometric-pressure data. Records from 37 selected wells were then analyzed for barometric efficiency and earth-tide responses. Specific-storage (Ss) and porosity values were determined, and the quality of the results were assessed with a measure of the "goodness of fit" (percent variance) of reconstruction of the response. Records from wells completed in several aquifer systems were analyzed with varying degrees of success. Aquifer Ss values ranging from 5.9 x 10-8 to 3.8 x 10-6/m were derived, with percent variance of reconstruction ranging from 1% to 78%. Comparisons with aquifer and laboratory testing of Ss and porosity are favorable if the percent variance of reconstruction is above about 30%. Although the earth-tide-analysis method is not suitable for every situation, the Ss and porosity of aquifers can, in many places, be estimated with existing water-level and barometric-pressure data or with data that are relatively inexpensive to collect.

  16. Numerical investigation of nanofluid transportation in a curved cavity in existence of magnetic source

    NASA Astrophysics Data System (ADS)

    Sheikholeslami, Mohsen; Ganji, Davood Domiri

    2017-01-01

    Thermal radiation impact on magnetic nanofluid heat transfer in a curved cavity is studied. Impact of external magnetic source is taken into account. Innovative numerical method is chosen namely CVFEM. Impacts of radiation parameter (Rd) , Rayleigh (Ra) , Hartmann (Ha) numbers and volume fraction of Fe3O4 (ϕ) on hydrothermal treatment are examined. Results indicate that temperature gradient enhances with augment of Ra, ϕ , but it reduces with rise of Rd, Ha . Lorentz forces cause the nanofluid velocity to reduce and augment the thermal boundary layer thickness. Impact of radiation becomes stronger for higher buoyancy forces.

  17. Viking magnetic properties experiment - Extended mission results

    NASA Technical Reports Server (NTRS)

    Hargraves, R. B.; Collinson, D. W.; Arvidson, R. E.; Cates, P. M.

    1979-01-01

    The backhoe magnets on Viking Lander (VL) 2 were successfully cleaned, followed by a test involving successive insertions of the cleaned backhoe into the surface. Rapid saturation of the magnets confirmed evidence from primary mission results that the magnetic mineral in the Martian surface is widely distributed, most probably in the form of composite particles of magnetic and nonmagnetic minerals. An image of the VL 2 backhoe taken via the X4 magnifying mirror demonstrates the fine-grained nature of the attracted magnetic material. The presence of maghemite and its occurrence as a pigment in, or a thin coating on, all mineral particles or as discrete, finely divided and widely distributed crystallites, are consistent with data from the inorganic analysis experiments and with laboratory simulations of results of the biology experiments on Mars.

  18. EM Properties of Magnetic Minerals at RADAR Frequencies

    NASA Technical Reports Server (NTRS)

    Stillman, D. E.; Olhoeft, G. R.

    2005-01-01

    Previous missions to Mars have revealed that Mars surface is magnetic at DC frequency. Does this highly magnetic surface layer attenuate RADAR energy as it does in certain locations on Earth? It has been suggested that the active magnetic mineral on Mars is titanomaghemite and/or titanomagnetite. When titanium is incorporated into a maghemite or magnetite crystal, the Curie temperature can be significantly reduced. Mars has a wide range of daily temperature fluctuations (303K - 143K), which could allow for daily passes through the Curie temperature. Hence, the global dust layer on Mars could experience widely varying magnetic properties as a function of temperature, more specifically being ferromagnetic at night and paramagnetic during the day. Measurements of EM properties of magnetic minerals were made versus frequency and temperature (300K- 180K). Magnetic minerals and Martian analog samples were gathered from a number of different locations on Earth.

  19. Magnetic properties of a nanoribbon: An effective-field theory

    NASA Astrophysics Data System (ADS)

    Wang, Jiu-Ming; Jiang, Wei; Zhou, Chen-Long; Shi, Zuo; Wu, Chuang

    2017-02-01

    An effective-field theory is proposed to study magnetic properties of a nanoribbon. The model consists of a core spin-3/2 and shell spin-2 with a ferrimagnetic exchange coupling, which is described by transverse Ising model with the anisotropy. Based on the differential operator technique, the magnetization and the susceptibility formulas of the nanoribbon are given. Numerical results of the magnetization, the susceptibility, the hysteresis loop of the system are discussed for specific values of the parameters. Magnetization plateaus exhibits on the magnetization curves at low temperature. The exchange coupling, the anisotropy and the transverse field have important roles in the magnetic properties for the nanoribbon. Results may provide some guidance to design in the nanoribbons.

  20. The magnetic properties of powdered and compacted microcrystalline permalloy

    NASA Astrophysics Data System (ADS)

    Kollár, P.; Olekšáková, D.; Füzer, J.; Kováč, J.; Roth, S.; Polański, K.

    2007-03-01

    The aim of this work is to investigate the magnetic properties of powdered and compacted microcrystalline Ni-Fe (81 wt% of Ni) permalloy. It was found by investigating the influence of mechanical milling on the magnetic properties of powder samples prepared by milling of the ribbon that the alloy remains a solid solution with stable structure during the whole milling process. With decreasing particle size the rotation of magnetization vector gradually becomes dominant magnetization process and thus coercivity increases. After compaction of the powder by uniaxial hot pressing the magnetic contact between powder particles is recreated and for resulting bulk the displacement of the domain walls becomes dominant magnetization process with coercivity of 11 A/m (comparable with the coercivity of conventional permalloy).

  1. Navier-Stokes in Aperture Domains:. Existence with Bounded Flux and Qualitative Properties

    NASA Astrophysics Data System (ADS)

    Maremonti, P.

    2008-04-01

    In this note we show a result of existence and some qualitative properties of solution to the Navier-Stokes equations in aperture domains. Roughly speaking, an aperture domain is an open connected consisting of two separated half-spaces connected by a hole. As it is known, in this special but physically interesting geometry the IBVP is a well posed if a flux condition trhough the hole is given as data. Our results correspond to an assumption on the flux that we consider physically reasonable. The results of this note will appear in the papers [2,18].

  2. Magnetic properties of cobalt ferrite synthesized by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Allaedini, Ghazaleh; Tasirin, Siti Masrinda; Aminayi, Payam

    2015-05-01

    In this study, the magnetic properties of nanocrystalline cobalt ferrite synthesized via the hydrothermal method have been investigated. The structural properties of the produced powders were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The observed XRD pattern confirmed the spinel/cubic structure of the prepared cobalt ferrite. The SEM pictures show that the simple hydrothermal method produces uniform sphere-shaped nanopowders. Moreover, infrared spectroscopy was used to confirm the formation of cobalt ferrite particles. Magnetic hysteresis was measured using a vibrating sample magnetometer in a maximum field of 10 kOe. The magnetization of the prepared nanoparticles was investigated, and the saturation magnetization ( M s), remanence ( M r), and coercivity ( H c) were derived from the hysteresis loops. The results revealed that the cobalt ferrite nanoparticles synthesized via the simple hydrothermal method exhibit superior magnetic properties.

  3. Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, Xiang; Pu, Shengli; Ji, Hongzhu; Yu, Guojun

    2012-05-01

    Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (Δ n) and figure of merit of optical properties ( Q = Δ n/α, where α is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of Q R exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field.

  4. Investigation on microstructure and magnetic properties of Sm2Co17 magnets aged at high temperature

    NASA Astrophysics Data System (ADS)

    Feng, Haibo; Chen, Hongsheng; Guo, Zhaohui; Pan, Wei; Zhu, Minggang; Li, Wei

    2011-04-01

    The Sm2Co17 magnet is the most promising candidate for high temperature applications. The microstructure evolutions and losses in the magnetic properties of the magnet in high temperature aging status have been investigated. The Sm(CobalFe0.22Cu0.068Zr0.025)7.75 magnets were prepared using the conventional powder sintering method. The magnet samples were isothermally aged at 500°C, 600 °C, and 700 °C for 72 h, respectively. The magnetic properties and the demagnetization curve were kept invariable for the magnet samples aged at 500 °C. The coercivity Hcj of the magnet samples decreased with increasing aging temperature. The Hcj decreased from 29.2 kOe for the original status samples to 10.8 kOe for the samples aged at 700 °C. The cell structure in the magnet is not destroyed after aging at 700 °C for 72 h. The deterioration of the magnetic properties and the demagnetization-curve squareness was caused by an increasing lattice mismatch between the 2:17R cell phase and the cell-boundary 1:5H phase, and by an increasing cell diameter for the magnet sample aged at a high temperature.

  5. Electronic and magnetic properties of Co doped MoS2 monolayer

    PubMed Central

    Wang, Yiren; Li, Sean; Yi, Jiabao

    2016-01-01

    First principle calculations are employed to calculate the electronic and magnetic properties of Co doped MoS2 by considering a variety of defects including all the possible defect complexes. The results indicate that pristine MoS2 is nonmagnetic. The materials with the existence of S vacancy or Mo vacancy alone are non-magnetic either. Further calculation demonstrates that Co substitution at Mo site leads to spin polarized state. Two substitutional CoMo defects tend to cluster and result in the non-magnetic behaviour. However, the existence of Mo vacancies leads to uniform distribution of Co dopants and it is energy favourable with ferromagnetic coupling, resulting in an intrinsic diluted magnetic semiconductor. PMID:27052641

  6. Magnetic properties in polycrystalline and single crystal Ca-doped LaCoO3

    NASA Astrophysics Data System (ADS)

    Zeng, R.; Debnath, J. C.; Chen, D. P.; Shamba, P.; Wang, J. L.; Kennedy, S. J.; Campbell, S. J.; Silver, T.; Dou, S. X.

    2011-04-01

    Polycrystalline (PC) and single crystalline (SC) Ca-doped LaCoO3 (LCCO) samples with the perovskite structure were synthesized by conventional solid-state reaction and the floating-zone growth method. We present the results of a comprehensive investigation of the magnetic properties of the LCCO system. Systematic measurements have been conducted on dc magnetization, ac susceptibility, exchange-bias, and the magnetocaloric effect. These findings suggest that complex structural phases, ferromagnetic (FM), and spin-glass/cluster-spin-glass (CSG), and their transitions exist in PC samples, while there is a much simpler magnetic phase in SC samples. It was also of interest to discover that the CSG induced a magnetic field memory effect and an exchange-bias-like effect, and that a large inverse irreversible magnetocaloric effect exists in this system.

  7. Electronic and magnetic properties of Am and Cm

    SciTech Connect

    Edelstein, N.

    1985-02-01

    A review of the present status of the analyses of the optical spectra of Am and Cm in various oxidation states is given. From these analyses, the magnetic properties of the ground states of these ions can be determined. These predicted values are compared with the various magnetic measurements available.

  8. Elastic properties of DNA linked flexible magnetic filaments

    NASA Astrophysics Data System (ADS)

    Ērglis, K.; Zhulenkovs, D.; Sharipo, A.; Cēbers, A.

    2008-05-01

    Elastic properties of magnetic filaments linked by DNA in solutions of univalent and bivalent salts with different pH values are investigated through their deformation in an external field. A strong dependence of the bending modulus in bivalent salt solution on the pH is shown. Experimental results are interpreted on the basis of the magnetic elastica.

  9. Synthesis and Magnetic Properties of CoPt Nanoparticles

    NASA Astrophysics Data System (ADS)

    Trung, Truong Thanh; Nhung, Do Thi; Nam, Nguyen Hoang; Luong, Nguyen Hoang

    2016-07-01

    Magnetic nanoparticles CoPt were prepared by the chemical reduction of cobalt (II) chloride and chloroplatinic acid, then the samples were ultrasonicated for 2 h. After annealing at various temperatures from 400°C to 700°C for 1 h, the samples showed hard magnetic properties with coercivity up to 1.15 kOe at room temperature.

  10. Synthesis and magnetic properties of nickel nanoparticles

    NASA Astrophysics Data System (ADS)

    Singh, Jaiveer; Patel, Tarachand; Kaurav, Netram; Okram, Gunadhor S.

    2016-05-01

    Monodisperse nickel nanoparticles (Ni-NPs) were synthesized via a thermal decomposition process. The NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). They were spherical with mean diameter of 4 nm. Zero field cooled (ZFC) and field cooled (FC) magnetization versus temperature data displayed interesting magnetic interactions. ZFC showed a peak at 4.49 K, indicating the super paramagnetic behavior. Magnetic anisotropic constant was estimated to be 4.62×105 erg/cm3 and coercive field was 168 Oe at 3 K.

  11. Magnetic porous composite material: Synthesis and properties

    NASA Astrophysics Data System (ADS)

    Peretyat'ko, P. I.; Kulikov, L. A.; Melikhov, I. V.; Perfil'ev, Yu. D.; Pal', A. F.; Timofeev, M. A.; Gudoshnikov, S. A.; Usov, N. A.

    2015-10-01

    A new method of obtaining magnetic porous composite materials is described, which is based on the self-propagating high-temperature synthesis (SHS) in the form of solid-phase combustion. The SHS process involves transformation of the nonmagnetic α-Fe2O3 particles (contained in the initial mixture) into magnetic Fe3O4 particles. The synthesized material comprises a porous carbonaceous matrix with immobilized Fe3O4 particles. The obtained composite has been characterized by electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. The sorption capacity of the porous material has been studied.

  12. Thermodynamic and magnetic properties of the layered triangular magnet NaNiO2

    NASA Astrophysics Data System (ADS)

    Baker, P. J.; Lancaster, T.; Blundell, S. J.; Brooks, M. L.; Hayes, W.; Prabhakaran, D.; Pratt, F. L.

    2005-09-01

    We report muon-spin rotation, heat capacity, magnetization, and ac magnetic susceptibility measurements of the magnetic properties of the layered spin- 1/2 antiferromagnet NaNiO2 . These show the onset of long-range magnetic order below TN=19.5K . Rapid muon depolarization, persisting from TN to about 5 K above TN , is consistent with the presence of short-range magnetic order. The temperature and frequency dependence of the ac susceptibility suggests that magnetic clusters persist above 25 K and that their volume fraction decreases with increasing temperature. A frequency dependent peak in the ac magnetic susceptibility at Tsf=3K is observed, consistent with a slowing of spin fluctuations at this temperature. A partial magnetic phase diagram is deduced.

  13. On the existence of finite amplitude, transverse Alfven waves in the interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Sari, J. W.

    1977-01-01

    Interplanetary magnetic field data from the Mariner 10 spacecraft were examined for evidence of small and finite amplitude transverse Alfven waves, general finite amplitude Alfven waves, and magnetosonic waves. No evidence for transverse Alfven waves was found. Instead, the field fluctuations were found to be dominated by the general finite amplitude Alfven wave. Such wave modes correspond to non-plane-wave solutions of the nonlinear magnetohydrodynamic equations.

  14. Isotropic-Cholesteric Co-Existence and Magnetic Field-Induced Isotropic-Nematic Transition of Filamentous Bacteriophage FD in Aqueous Suspension.

    NASA Astrophysics Data System (ADS)

    Tang, Jianxin

    1995-01-01

    Isotropic to liquid crystalline phase transition for a lyotropic suspension of geometrically asymmetric macromolecules occurs to a wild class of synthetic polymers and biopolymers. Although in decades statistical mechanical theories have been developed to predict the thermodynamic conditions and the properties of such transition, quantitative comparison with theory has been compounded with complications such as charge, shape, polydispersity in size, and additional interactions with the solvent and among the macromolecules themselves. We chose the aqueous suspension of the filamentous bacteriophage fd as a model system to study the isotropic to liquid crystalline transition. The co-existence concentrations, as a function of ionic strength, were measured directly by spectrophotometry. Our data confirm quantitatively the predictions of a statistical mechanic treatment first described by Onsager, modified to include the effects of charge and flexibility of rodlike particles. We have also extended a previous study of the pretransitional angular correlations in the isotropic solutions of fd through the measurement of the magnetic-field-induced birefringence, i.e. the measurement of the Cotton-Mouton constant. At several ionic strengths the magnetic-field-induced birefringence, which is proportional to the number of particles in a correlation volume N_{rm corr}, was measured for fd concentrations spanning the entire isotropic region. From this data the limiting concentration of stability (spinodal) of the isotropic phase is obtained. A theoretical expression for the magnetic birefringence of persistent polymers was derived and agreed well with the data with the exception that N_{rm corr} at the isotropic to liquid crystal transition was smaller than predicted. In the proximity of the highest possible isotropic concentration, that is the isotropic in co-existence with anisotropic, we studied the effect of a high magnetic field. A first order field-induced isotropic

  15. Magnetic properties of alluvial soils polluted with heavy metals

    NASA Astrophysics Data System (ADS)

    Dlouha, S.; Petrovsky, E.; Boruvka, L.; Kapicka, A.; Grison, H.

    2012-04-01

    Magnetic properties of soils, reflecting mineralogy, concentration and grain-size distribution of Fe-oxides, proved to be useful tool in assessing the soil properties in terms of various environmental conditions. Measurement of soil magnetic properties presents a convenient method to investigate the natural environmental changes in soils as well as the anthropogenic pollution of soils with several risk elements. The effect of fluvial pollution with Cd, Cu, Pb and Zn on magnetic soil properties was studied on highly contaminated alluvial soils from the mining/smelting district (Příbram; CZ) using a combination of magnetic and geochemical methods. The basic soil characteristics, the content of heavy metals, oxalate, and dithionite extractable iron were determined in selected soil samples. Soil profiles were sampled using HUMAX soil corer and the magnetic susceptibility was measured in situ, further detailed magnetic analyses of selected distinct layers were carried out. Two types of variations of magnetic properties in soil profiles were observed corresponding to indentified soil types (Fluvisols, and Gleyic Fluvisols). Significantly higher values of topsoil magnetic susceptibility compared to underlying soil are accompanied with high concentration of heavy metals. Sequential extraction analysis proved the binding of Pb, Zn and Cd in Fe and Mn oxides. Concentration and size-dependent parameters (anhysteretic and isothermal magnetization) were measured on bulk samples in terms of assessing the origin of magnetic components. The results enabled to distinguish clearly topsoil layers enhanced with heavy metals from subsoil samples. The dominance of particles with pseudo-single domain behavior in topsoil and paramagnetic/antiferromagnetic contribution in subsoil were observed. These measurements were verified with room temperature hysteresis measurement carried out on bulk samples and magnetic extracts. Thermomagnetic analysis of magnetic susceptibility measured on

  16. Transport Properties of Equilibrium Argon Plasma in a Magnetic Field

    SciTech Connect

    Bruno, D.; Laricchiuta, A.; Chikhaoui, A.; Kustova, E. V.; Giordano, D.

    2005-05-16

    Electron electrical conductivity coefficients of equilibrium Argon plasma in a magnetic field are calculated up to the 12th Chapman-Enskog approximation at pressure of 1 atm and 0.1 atm for temperatures 500K-20000K; the magnetic Hall parameter spans from 0.01 to 100. The collision integrals used in the calculations are discussed. The convergence properties of the different approximations are assessed. The degree of anisotropy introduced by the presence of the magnetic field is evaluated. Differences with the isotropic case can be very substantial. The biggest effects are visible at high ionization degrees, i.e. high temperatures, and at strong magnetic fields.

  17. Thermal to electricity conversion using thermal magnetic properties

    DOEpatents

    West, Phillip B [Idaho Falls, ID; Svoboda, John [Idaho Falls, ID

    2010-04-27

    A system for the generation of Electricity from Thermal Energy using the thermal magnetic properties of a Ferromagnetic, Electrically Conductive Material (FECM) in one or more Magnetic Fields. A FECM is exposed to one or more Magnetic Fields. Thermal Energy is applied to a portion of the FECM heating the FECM above its Curie Point. The FECM, now partially paramagnetic, moves under the force of the one or more Magnetic Fields. The movement of the FECM induces an electrical current through the FECM, generating Electricity.

  18. Structural and Magnetic Properties of Thin Film of Iron Nitride

    NASA Astrophysics Data System (ADS)

    Kayani, Zohra Nazir; Riaz, Saira; Naseem, Shahzad

    2014-12-01

    The nano-crystalline iron nitride films with a mixture of γ-Fe4N, ɛFe3N and αFe2N phases were synthesized on copper substrate by sol-gel technology. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. The films are ferromagnetic at room temperature. Magnetic properties such as coercive forces and saturation magnetization were found to be 398 Oestered and 32.92 emu/cm3, respectively.

  19. Preparation and Magnetic Properties of MnBi/Co Nanocomposite Magnets

    NASA Astrophysics Data System (ADS)

    Nguyen, Truong Xuan; Vuong, Oanh Kim Thi; Nguyen, Hieu Trung; Nguyen, Vuong Van

    2017-02-01

    The method of synthesis and the magnetic properties of MnBi/Co nanocomposite magnets prepared with a combination of the magnetically hard MnBi alloy and semi-hard Co nanowires (CoNWs) have been investigated. The MnBi alloys were produced by arc-melting and temperature-gradient-driven annealing techniques. The CoNWs with high spontaneous magnetization M s (125 emu/g) and large aspect ratio α (5 ÷ 10) were synthesized by the solvothermal method. The nanocomposite MnBi/Co powder mixtures were cold ball-milled, aligned in an 18-kOe-field and warm-compacted into bulk magnets at 300°C under a uniaxial pressure of 2000 psi for 10 min. The magnetization and coercivity of the nanocomposite magnets were improved due to the intrinsic high magnetization and shape anisotropy of the CoNWs. The energy product, (BH)max, of the MnBi/Co nanocomposite magnets with 15 wt.% CoNWs reached its highest value of 4.8 MGOe. The simulation of magnetic properties of MnBi/Co magnets is also discussed in detail.

  20. Defective graphene and nanoribbons: electronic, magnetic and structural properties

    NASA Astrophysics Data System (ADS)

    Guerra, Thiago; Azevedo, Sérgio; Machado, Marcelo

    2016-03-01

    We make use of first-principles calculations, based on the density functional theory (DFT), to investigate the alterations at the structural, energetic, electronic and magnetic properties of graphene and zigzag graphene nanoribbons (ZGNRs) due to the inclusion of different types of line and punctual defects. For the graphene it is found that the inclusion of defects breaks the translational symmetry of the crystal with drastic changes at its electronic structure, going from semimetallic to semiconductor and metallic. Regarding the magnetic properties, no magnetization is observed for the defective graphene. We also show that the inclusion of defects at ZGNRs is a good way to create and control pronounced peaks at the Fermi level. Furthermore, defective ZGNRs structures show magnetic moment by supercell up to 2.0 μ B . For the non defective ZGNRs is observed a switch of the magnetic coupling between opposite ribbon edges from the antiferromagnetic to the ferrimagnetic and ferromagnetic configurations.

  1. Characterizing the Properties of Coronal Magnetic Null Points

    NASA Astrophysics Data System (ADS)

    Barnes, Graham; DeRosa, Marc; Wagner, Eric

    2015-08-01

    The topology of the coronal magnetic field plays a role in a wide range of phenomena, from Coronal Mass Ejections (CMEs) through heating of the corona. One fundamental topological feature is the null point, where the magnetic field vanishes. These points are natural sites of magnetic reconnection, and hence the release of energy stored in the magnetic field. We present preliminary results of a study using data from the Helioseismic and Magnetic Imager aboard NASA's Solar Dynamics Observatory to characterize the properties and evolution of null points in a Potential Field Source Surface model of the coronal field. The main properties considered are the lifetime of the null points, their distribution with height, and how they form and subsequently vanish.This work is supported by NASA/LWS Grant NNX14AD45G, and by NSF/SHINE grant 1357018.

  2. Magnetic properties of ErN films

    NASA Astrophysics Data System (ADS)

    Meyer, C.; Ruck, B. J.; Preston, A. R. H.; Granville, S.; Williams, G. V. M.; Trodahl, H. J.

    2010-07-01

    We report a magnetization study of stoichiometric ErN nanocrystalline films grown on Si and protected by a GaN passivating layer. According to the temperature dependence of the resistivity the films are heavily doped semiconductors. Above 100 K the magnetization data fit well to a Curie-Weiss behavior with a moment expected within the free-ion ErJ={15}/{2} multiplet. Below 50 K the Curie-Weiss plot steepens to an effective moment corresponding to that in the crystal-field determined quartet ground state, and develops a clear paramagnetic Curie-Weiss temperature of about 4.5 K. Zero-field- and field-cooled magnetization curves and the AC susceptibility firmly establish a ferromagnetic ground state within that multiplet below a Curie temperature of 6.3±0.7 K. Due to the (1 1 1) texture of the film the comparison between the magnetization behavior, when the field is applied parallel and perpendicular to the film plane, gives new information about the magnetic structure. An arrangement of the moments according to the model derived from neutron diffraction for bulk HoN is strongly suggested.

  3. Controlling electronic and magnetic properties of ultra narrow multilayered nanowires

    NASA Astrophysics Data System (ADS)

    Panigrahi, Puspamitra

    Interest in the study of magnetic/non-magnetic multilayered structures took a giant leap since Grunberg and his group established that the interlayer exchange coupling (IEC) is a function of the non-magnetic spacer width. This interest was further fuelled by the discovery of the phenomenal Giant Magnetoresistance (GMR) effect. In fact, in 2007 Albert Fert and Peter Grunberg were awarded the Nobel Prize in Physics for their contribution to the discovery of GMR. GMR is the key property that is being used in the read-head of the present day computer hard drive as it requires a high sensitivity in the detection of magnetic field. The recent increase in demand for device miniaturization encouraged researchers to look for GMR in nanoscale multilayered structures. In this context, one dimensional (1-D) multilayered nanowire structure has shown tremendous promise as a viable candidate for ultra sensitive read head sensors. In fact, the phenomenal giant magnetoresistance (GMR) effect, which is the novel feature of the currently used multilayered thin film, has already been observed in multilayered nanowire systems at ambient temperature. Geometrical confinement of the supper lattice along the 2-dimensions (2-D) to construct the 1-D multilayered nanowire prohibits the minimization of magnetic interaction-offering a rich variety of magnetic properties in nanowire that can be exploited for novel functionality. In addition, introduction of non-magnetic spacer between the magnetic layers presents additional advantage in controlling magnetic properties via tuning the interlayer magnetic interaction. Despite of a large volume of theoretical works devoted towards the understanding of GMR and IEC in super lattice structures, limited theoretical calculations are reported in 1-D multilayered systems. Thus to gauge their potential application in new generation magneto-electronic devices, in this thesis, I have discussed the usage of first principles density functional theory (DFT) in

  4. Magnetic properties of rivers sands and rocks from Martinique Island: tracers of weathering?

    NASA Astrophysics Data System (ADS)

    Salomé, Anne-Lise; Meynadier, Laure

    The purpose of this study is to compare the magnetic properties of parent rocks with their weathering products (i.e., sands) in order to ultimately trace the transport pathways of magnetic particles into the ocean. Considering the high rate of alteration and the high magnetic content of volcanic rocks, we chose to study a volcanic island as a test area. We selected the small Martinique Island, which is characterized by a hot climate and important alteration of the lava flows. Martinique Island sample sites consist of andesitic rocks that range in age from 0.7-23 Ma. Sands were sampled in several riverbeds on the island while rocks were taken in the surrounding lava flows. Classical rock magnetic parameters with associated ratios, hysteresis loops and the monitoring of magnetic susceptibility during heating were used as indicators of magnetic mineralogy, grain size and concentration. We found that the parent rocks and their weathering products have similar magnetic properties, thereby demonstrating that rock magnetic parameters of the parent rocks are, to the first order, good tracers of sediment sources and transport in the ocean. However, small variations between rocks and sands are mostly due to mineralogical changes between the parent rocks and their weathered sands. A small amount of a second mineral, that could be pyrrhotite, was detected in sands but not in the parent rocks. These observations indicate that the iron oxides within lavas can be affected by chemical weathering during their alteration in situ or during transport. Reduction/oxidation processes have some (limited) effects on the magnetic particles. These results agree with previous geochemical studies, which show that the particles transported to the ocean are not simply crushed parent rocks but are slightly chemically different. We suggest here that similarly small differences may exist in magnetic mineralogy, but this does not affect the magnetic parameters enough to induce problems in their use

  5. Nuclear magnetic resonance properties of lunar samples.

    NASA Technical Reports Server (NTRS)

    Kline, D.; Weeks, R. A.

    1972-01-01

    Nuclear magnetic resonance spectra of Na-23, Al-27, and P-31 in fines samples 10084,60 and 14163,168 and in crystalline rock samples 12021,55 and 14321,166, have been recorded over a range of frequencies up to 20 MHz. A shift in the field at which maximum absorption occurs for all of the spectra relative to the field at which maximum absorption occurs for terrestrial analogues is attributed to a sample-dependent magnetic field at the Na, Al, and P sites opposing the laboratory field. The magnitude of these fields internal to the samples is sample dependent and varies from 5 to 10 G. These fields do not correlate with the iron content of the samples. However, the presence of single-domain particles of iron distributed throughout the plagioclase fraction that contains the principal fraction of Na and Al is inferred from electron magnetic resonance spectra shapes.

  6. Magnetic properties of 42CrMo4 steel

    NASA Astrophysics Data System (ADS)

    Bulin, T.; Svabenska, E.; Hapla, M.; Roupcova, P.; Ondrusek, C.; Schneeweiss, O.

    2017-02-01

    Low alloyed high-grade chrome-molybdenum ferritic steel was investigated from the point of views of magnetic properties in dependence on heat and mechanical treatment. This steel can be used as components of magnetic circuits or some parts in electrical equipment. The basic information on structure and phase composition was obtained by optical and scanning electron microscopy, X-ray Powder Diffraction and Mössbauer Spectroscopy. The temperature stability of the material was proved by measurements of temperature dependences of magnetic moment. The magnetic parameters were obtained by measuring of magnetic hysteresis loops in dependence on saturation field and their frequencies. The results are discussed from the point of view of possible applications as a magnetic material in the very extremely environment, where high mechanical stresses and elevated temperatures can occur.

  7. Magnetic properties of Cr and Mn powders (abstract)

    NASA Astrophysics Data System (ADS)

    Zhukov, A. P.; Ivanov, S. A.; Nudelman, M. A.; Ponomarev, B. K.; Kaloshkin, S. D.; Shatov, A. A.

    1993-05-01

    Mn and Cr powders were produced from electrolytic Mn and Cr by ball milling in a stainless steel container with carbon steel balls. The milling time, t, varied from 5 min to 8 h. Structures were investigated by x-ray and electron microscopy. Chemical compositions of samples were checked by flame atomic absorption spectrometry. The magnetization was measured by induction method in a pulsed magnetic field up to 10 T. The main part of Mn and Cr powder volume was occupied by α-Mn and b.c.c. Cr, respectively. Diffraction peaks became vaster and more asymmetric with increasing t due to the onset of defects of the structure. The presence of MnO was observed in the Mn sample after 8 h of milling. The size of Mn and Cr particles over same critical t (for chromium t=100 min) was no more than 1 mm. A noticeable Fe content, which increases at higher t, was observed. The Mössbauer spectra of Cr and Mn samples showed the lines of α-Fe and γ-Fe. High values of saturation magnetization, σ, up to 5.4 emu/g, and susceptibility and existence of the hysteresis in low fields at temperatures up to 360 K, indicate ferromagnetic ordering of the samples. Within the range of 78-360 K σ only slightly depends on temperature, but noticeably grows with increasing t at fixed temperature in Cr powders, remaining practically constant in Mn powders. No correlation could be observed between Fe content and σ : the latter remained the same in Mn with Fe concentration increasing, but in Cr, as Fe concentration increased sevenfold, it grew by four times. Spontaneous magnetization per mass unit of Fe, σ, was sufficiently lower than that of pure α-Fe (220 emu/g). The obtained values of σ correspond neither to Fe solid solution nor to pure Cr or Mn. Elucidation of the obtained results can be done both by the presence of α-Fe particles and by variation of exchange interactions caused by sample defects. A noticeable difference of σ values from those properties of bulk α-Fe can be explained by

  8. Magnetic properties of a classical XY spin dimer in a "planar" magnetic field

    NASA Astrophysics Data System (ADS)

    Ciftja, Orion; Prenga, Dode

    2016-10-01

    Single-molecule magnetism originates from the strong intra-molecular magnetic coupling of a small number of interacting spins. Such spins generally interact very weakly with the neighboring spins in the other molecules of the compound, therefore, inter-molecular spin couplings are negligible. In certain cases the number of magnetically coupled spins is as small as a dimer, a system that can be considered the smallest nanomagnet capable of storing non-trivial magnetic information on the molecular level. Additional interesting patterns arise if the spin motion is confined to a two-dimensional space. In such a scenario, clusters consisting of spins with large-spin values are particularly attractive since their magnetic interactions can be described well in terms of classical Heisenberg XY spins. In this work we calculate exactly the magnetic properties of a nanomagnetic dimer of classical XY spins in a "planar" external magnetic field. The problem is solved by employing a mathematical approach whose idea is the introduction of auxiliary spin variables into the starting expression of the partition function. Results for the total internal energy, total magnetic moment, spin-spin correlation function and zero-field magnetic susceptibility can serve as a basis to understand the magnetic properties of large-spin dimer building blocks.

  9. Magnetic and Electrical Properties of Ferromagnetic Semiconductors,

    DTIC Science & Technology

    magnetism and of the mechanism of the electronic conductivity of ferromagnetic semiconductors in connection with their chemical composition and crystalline ... structure . The basic groups of oxide compounds of 4f- and 3d-transition metals with maximum spin values were selected for the studies in this work. The

  10. Magnetic Properties of Radiation Damage in Pu

    SciTech Connect

    McCall, S; Fluss, M J; Chung, B W; McElfresh, M; Chapline, G; Jackson, D

    2004-10-27

    First, we review earlier studies reporting possible magnetic characteristics for radiation defects in Pu. We then report, for {alpha}-Pu, two studies of the excess magnetic susceptibility (EMS) due to radiation damage, as a function of time and temperature. We have observed several annealing stages associated with the EMS of the accumulated self-damage and we report that annealing begins at {approx}31K, while below that temperature the displacement damage from self-irradiation of the Pu alpha particle emission and the U recoil are immobile. A detailed investigation was made of this EMS well below the first annealing stage as a function of temperature (2K < T < 15K) and time in a magnetic field of 2T. A linear increase in magnetic susceptibility is seen as a function of time for all isotherms. The excess susceptibility per alpha decay, determined from a linear fit of the slope of the time dependent EMS, is reasonably described with a Curie-Weiss law exhibiting a small negative Weiss temperature. We conclude by describing some future experiments in light of the present results.

  11. Statistical thermodynamics of magnetic fluids. Monte Carlo calculation of the magnetic properties

    SciTech Connect

    Berkovskii, B.M.; Kalikmanov, V.I.; Filinov, V.S.

    1988-07-01

    An approach is proposed, and a modification of the Monte Carlo method is presented, for the calculation of the equilibrium thermodynamic properties of a magnetic fluid. The magnetization and mean energy are calculated. It is shown that the behavior of these properties differs from Langevin behavior, as a result of taking particle interactions into account. The results obtained are in good agreement with experimental data.

  12. Vortex magnetic structure in framboidal magnetite reveals existence of water droplets in an ancient asteroid

    NASA Astrophysics Data System (ADS)

    Kimura, Yuki; Sato, Takeshi; Nakamura, Norihiro; Nozawa, Jun; Nakamura, Tomoki; Tsukamoto, Katsuo; Yamamoto, Kazuo

    2013-10-01

    The majority of water has vanished from modern meteorites, yet there remain signatures of water on ancient asteroids. How and when water disappeared from the asteroids is important, because the final fluid-concentrated chemical species played critical roles in the early evolution of organics and in the final minerals in meteorites. Here we show evidence of vestigial traces of water based on a nanometre-scale palaeomagnetic method, applying electron holography to the framboids in the Tagish Lake meteorite. The framboids are colloidal crystals composed of three-dimensionally ordered magnetite nanoparticles and therefore are only able to form against the repulsive force induced by the surface charge of the magnetite as a water droplet parches in microgravity. We demonstrate that the magnetites have a flux closure vortex structure, a unique magnetic configuration in nature that permits the formation of colloidal crystals just before exhaustion of water from a local system within a hydrous asteroid.

  13. Influence of a large amount of Co substitution on the magnetic properties of NdFeCoGaB magnets (abstract)

    NASA Astrophysics Data System (ADS)

    Tsutai, A.; Sakai, I.; Sahashi, M.; Inomata, K.

    1990-05-01

    We have found that a NdFeCoGaB sintered magnet containing 30 at. % Co still shows high coercive force in spite of such a large amount of Co substitution. The Curie temperature of the magnet is higher than that of the ternary NdFeB magnet by 280 °C. As a result, the following magnetic properties have been attained for Nd14.5Fe46Co30Ga1B8.5: Tc=590 °C, Br =11.7 kG, Hci =14.3 kOe, and (BH)max=32 MG Oe. Furthermore, in this magnet there exists an additional phase, Nd1(FeCoGa)4B1 with Ce1Co4B1 structure, which, as far as authors know, has not been reported to exist in the NdFeB-based magnets. In this study we investigated the magnetic properties and microstructure of Nd14.5Fe76-xCoxGa1B8.5 (x=16-50) sintered magnets. The high coercive force can be obtained in the Co-content region from 16 to 30 at. %. In particular, the magnet with 30 at. % Co shows coercive force as high as 14.3 kOe. However, further substitution of Co drastically deteriorates the magnetic properties. The coercive force of the magnet with 50 at. % Co is less than 1 kOe. From the metallographical point of view, the above-mentioned Nd1(FeCoGa)4B1 phase is not observed in the magnets containing less than 30 at. % Co. This phase abruptly appears in the magnet with 30 at. % Co and its amount increases with increasing Co content. The strongest x-ray-diffraction peak observed in the magnet with 50 at. % Co comes from the Nd1(FeCoGa)4B1 phase. The demagnetization-curve measurements suggest that reverse magnetic domains are nucleated in the Nd1(FeCoGa)4B1 phase at a low reverse magnetic field. It is noteworthy that the magnet with 30 at. % Co maintains the high coercive force in spite of the existence of such a soft magnetic phase. Details will be discussed in the coming session.

  14. Magnetic properties of solid oxygen under pressure (Review Article)

    NASA Astrophysics Data System (ADS)

    Freiman, Yu. A.

    2015-11-01

    Solid oxygen is a unique crystal combining properties of a simple molecular solid and a magnet. Unlike ordinary magnets, the exchange interaction in solid oxygen acts on a background of weak Van der Waals forces, providing a significant part of the total lattice energy. Therefore, the magnetic and lattice properties of solid oxygen are very closely related. This manifests itself in a very rich phase diagram and numerous anomalies of thermal, magnetic and optical properties. Low-temperature low-pressure α-O2 is a two-sublattice collinear Neel antiferromagnet. At a pressure of ˜6 GPa, α-O2 is transformed into δ-O2, in which three different magnetic structures are realized upon increasing temperature. At ˜8 GPa δ-O2 is transformed into ɛ-O2. In this transition, O2 molecules combine into four-molecule clusters (O2)4. This transformation is accompanied by a magnetic collapse. This review describes the evolution of the magnetic structure with increasing pressure, and analyzes the causes behind this behavior.

  15. The symmetry properties of planetary magnetic fields

    NASA Technical Reports Server (NTRS)

    Raedler, Karl-Heinz; Ness, Norman F.

    1990-01-01

    This paper provides a comparative study of the geometrical structures of the magnetic fields of earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For earth, Jupiter, and Saturn, the centered dipole, quadrupole, and octupole contributions are included, while at Uranus only the dipole and quadrupole contributions are considered. It is found that there are a number of common features of the magnetic fields of earth and Jupiter. Compared to earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets.

  16. Magnetic properties of nano-composite particles

    NASA Astrophysics Data System (ADS)

    Xu, Xia

    Chemical synthesis routes for hollow spherical BaFe12O 19, hollow mesoporous spherical BaFe12O19, worm-shape BaFe12O19 and FeCo particles were developed. These structured particles have great potentials for the applications including magnetic recording medium, catalyst support, and energy storage. Magnetically exchange coupled hard/soft SrFe12O19/FeCo and MnBi/FeCo composites were synthesized through a newly proposed process of magnetic self-assembly. These exchange coupled composites can be potentially used as rare-earth free permanent magnets. Hollow spherical BaFe12O19 particles (shell thickness ˜5 nm) were synthesized from eth-ylene glycol assisted spray pyrolysis. Hollow mesoporous spherical BaFe12O19 particles (shell thickness ˜100 nm) were synthesized from ethanol assisted spray pyrolysis, followed by alkaline ethylene glycol etching at 185 °C. An alpha-Fe2O3 and BaCO3 nanoparticle mixture was synthesized with reverse microemulsion, followed by annealing at 900 °C for 2 hours to get worm-shape BaFe 12O19 particles, which consisted of 3-7 stacked hexagonal plates. FeCo nanoparticles were synthesized by reducing FeCl2 and CoCl2 in diphenyl ether with n-butyllithium at 200 °C in an inert gas environment. The surfactant of oleic acid was used in the synthesis to make particles well dispersed in nonpolar solvents (such as hexane). SrFe12O19/FeCo core/shell particles were prepared through a magnetic self-assembly process. The as-synthesized soft FeCo nanoparticles were magnetically attracted by hard SrFe12O19 parti-cles, forming a SrFe12O19/FeCo core/shell structure. The magnetic self-assembly mechanism was confirmed by applying alternating-current demagnetization to the core/shell particles, which re-sulted in a separation of SrFe 12O19 and FeCo particles. MnBi/FeCo composites were synthesized, and the exchange coupling between MnBi and FeCo phases was demonstrated by smooth magnetic hysteresis loop of MnBi/FeCo composites. The thermal stability of Mn

  17. Basic magnetic properties of bituminous coal

    USGS Publications Warehouse

    Alexander, C.C.; Thorpe, A.N.; Senftle, F.E.

    1979-01-01

    Magnetic susceptibility and other static magnetic parameters have been measured on a number of bituminous coals from various locations in the United States. The paramagnetic Curie constant correlates negatively with carbon concentration on a moisture-free basis. The major contribution to the total paramagnetism comes from the mineral matter rather than from free radicals or broken bonds. Analysis of the data indicates that the specific paramagnetism is generally lower in the mineral matter found in high-ash compared to low-ash coal. A substantial number of the coal specimens tested also had a ferromagnetic susceptibility which appeared to be associated with magnetite. Magnetite and ??-iron spherules, possibly of meteoritic or volcanic origin, were found in several specimens. ?? 1979.

  18. Microstructure and magnetic properties of FINEMET nanowires

    NASA Astrophysics Data System (ADS)

    Chiriac, H.; Corodeanu, S.; Óvári, T.-A.; Lupu, N.

    2013-05-01

    FINEMET (Fe73.5Cu1Nb3Si13.5B9) glass-coated nanowires and submicron wires with metallic nucleus diameters (Φm) between 100 and 500 nm and the glass coating thickness (tg) of 5 μm are reported for the first time. The microstructure of annealed ultrathin glass-coated wires evolves into a nanocrystalline one (DO3 nanograins of 10-20 nm embedded into the residual amorphous matrix) after annealing at 550 °C and 600 °C for 60 min. Despite the similar size of the nanograins, the volume occupied by them relative to the total volume increases from 50%-53% after annealing at 550 °C to 63%-65% after annealing at 600 °C, due to the increase in their number. This is reflected in a more accurate manner in the domain wall velocity measurements than in variation of the magnetic characteristics such as M(H), relative magnetic permeability or switching field. The magnetically softest nanocrystalline phase is formed at larger values of annealing temperature (Ta) for thinner wires, since larger temperature is needed to grow a sufficient number of DO3 grains at distances below the exchange length among them.

  19. A Linear Relationship Exists among Brain Diffusion Eigenvalues Measured by Diffusion Tensor Magnetic Resonance Imaging

    NASA Astrophysics Data System (ADS)

    Bahn, Mark M.

    1999-03-01

    Diffusion in biological tissues can be measured by magnetic resonance diffusion tensor imaging The complex nature of anisotropic diffusion in the brain has been described by a diffusion tensor which contains information about the magnitude of diffusion in different directions. Each tensor contains a set of three eigenvalues which are related to the major, intermediate, and minor axes of a diffusion ellipsoid. This investigation demonstrates that the various sets of diffusion eigenvalues from different regions of the brain lie along a line in ordered eigenvalue space. Sets of ordered diffusion eigenvalues were considered points in ordered eigenvalue space. The line which best fit the data by minimizing the total squared deviations was determined. A new coordinate system was constructed through translation and rotation which spanned ordered eigenvalue space. Eigenvalues from both monkey brain and human brain were studied. It was found that the sets of eigenvalues from both species have significant linear trends. Moreover, the same line may describe the brain eigenvalues from both species. It is likely that this linear relationship of the eigenvalues observed in an ordered eigenvalue plot is related to a combination of (1) conservation of total isotropic diffusion and (2) the degree of orientational dispersion of the microfibers within each voxel.

  20. Synthesis and magnetic properties of a novel ferrite organogel

    NASA Astrophysics Data System (ADS)

    Li, Sichu; John, Vijay T.; Irvin, Glen C.; Rachakonda, Suguna H.; McPherson, Gary L.; O'Connor, Charles J.

    1999-04-01

    A novel magnetic organogel that can be considered a precursor example of a magnetoresponsive gel is reported. The gel is formed by the bridging of ferrite containing anionic bis(2-ethlhexyl) sodium sulfosuccinate reverse micelles with 2,6-dihydroxynaphthalene (2,6-DHN). The addition of 2,6-DHN leads to a room temperature quotes "freezing in" of the liquid solution to a clear organogel. Ferrite particles in the size range 10-15 nm are doped into the gel network and are thus suspended in the optically clear gel media. The magnetic properties of the gel were measured using a superconducting quantum interference device magnetometer. The results reveal that the gel exhibits superparamagnetic behavior with a blocking temperature of 6 K (at an applied field of 1000 G), and a coercivity of 850 G at 2 K. The ferrites introduced into the gel serve the function of magnetic "seeds" via which magnetic properties are acquired by the gel.

  1. Magnetic Properties of ni Nanowires Grown in Mesoporous Silicon Templates

    NASA Astrophysics Data System (ADS)

    Dolgiy, A. L.; Redko, S. V.; Yanushkevich, K. I.

    2013-05-01

    Magnetic properties of Ni nanowires electrochemically deposited into pores of mesoporous silicon template under the stationary galvanostatic regime were investigated by measuring the temperature dependence (77-700 K) of the specific magnetization σ. The measured σ values were lower with respect to that of bulk Ni. The Curie temperature, TC, derived from σ(T) for low deposition times of Ni was less (575 K) than that for bulk Ni (630 K). This is caused by dimensional effects of Ni nanoparticles.

  2. GEMAS: Unmixing magnetic properties of European agricultural soil

    NASA Astrophysics Data System (ADS)

    Fabian, Karl; Reimann, Clemens; Kuzina, Dilyara; Kosareva, Lina; Fattakhova, Leysan; Nurgaliev, Danis

    2016-04-01

    High resolution magnetic measurements provide new methods for world-wide characterization and monitoring of agricultural soil which is essential for quantifying geologic and human impact on the critical zone environment and consequences of climatic change, for planning economic and ecological land use, and for forensic applications. Hysteresis measurements of all Ap samples from the GEMAS survey yield a comprehensive overview of mineral magnetic properties in European agricultural soil on a continental scale. Low (460 Hz), and high frequency (4600 Hz) magnetic susceptibility k were measured using a Bartington MS2B sensor. Hysteresis properties were determined by a J-coercivity spectrometer, built at the paleomagnetic laboratory of Kazan University, providing for each sample a modified hysteresis loop, backfield curve, acquisition curve of isothermal remanent magnetization, and a viscous IRM decay spectrum. Each measurement set is obtained in a single run from zero field up to 1.5 T and back to -1.5 T. The resulting data are used to create the first continental-scale maps of magnetic soil parameters. Because the GEMAS geochemical atlas contains a comprehensive set of geochemical data for the same soil samples, the new data can be used to map magnetic parameters in relation to chemical and geological parameters. The data set also provides a unique opportunity to analyze the magnetic mineral fraction of the soil samples by unmixing their IRM acquisition curves. The endmember coefficients are interpreted by linear inversion for other magnetic, physical and chemical properties which results in an unprecedented and detailed view of the mineral magnetic composition of European agricultural soils.

  3. Dust properties and magnetic field geometry towards LDN 1570

    NASA Astrophysics Data System (ADS)

    Eswaraiah, C.; Maheswar, G.; Pandey, A. K.

    2015-03-01

    We have performed both optical linear polarimetric and photometric observations of an isolated dark globule LDN 1570 aim to study the dust polarizing and extinction properties and to map the magnetic field geometry so as to understand not only the importance of magnetic fields in formation and evolution of clouds but also the correlation of the inferred magnetic field structure with the cloud structure and its dynamics. Dust size indicators (R V and λ max ) reveal for the presence of slightly bigger dust grains towards the cloud region. The inferred magnetic field geometry, which closely follows the cloud structure revealed by Herschel images, suggest that the cloud could have been formed due to converging material flows along the magnetic field lines.

  4. Studying the magnetic properties of CoSi single crystals

    SciTech Connect

    Narozhnyi, V. N. Krasnorussky, V. N.

    2013-05-15

    The magnetic properties of CoSi single crystals have been measured in a range of temperatures T = 5.5-450 K and magnetic field strengths H {<=} 11 kOe. A comparison of the results for crystals grown in various laboratories allowed the temperature dependence of magnetic susceptibility {chi}(T) = M(T)/H to be determined for a hypothetical 'ideal' (free of magnetic impurities and defects) CoSi crystal. The susceptibility of this ideal crystal in the entire temperature range exhibits a diamagnetic character. The {chi}(T) value significantly increases in absolute value with decreasing temperature and exhibits saturation at the lowest temperatures studied. For real CoSi crystals of four types, paramagnetic contributions to the susceptibility have been evaluated and nonlinear (with respect to the field) contributions to the magnetization have been separated and taken into account in the calculations of {chi}(T).

  5. Structural and magnetic properties of granular CoPd multilayers

    NASA Astrophysics Data System (ADS)

    Vivas, L. G.; Figueroa, A. I.; Bartolomé, F.; Rubín, J.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Brookes, N. B.; Wilhelm, F.; Rogalev, A.; Bartolomé, J.

    2016-02-01

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

  6. Microstructure and Magnetic Properties of Bulk Nanocrystalline MnAl

    SciTech Connect

    Chaturvedi, A; Yaqub, R; Baker, I

    2014-01-22

    MnAl is a promising rare-earth free permanent magnet for technological use. We have examined the effects of consolidation by back-pressure, assisted equal channel angular extrusion processing on mechanically-milled, gas-atomized Mn-46% at. Al powder. X-ray diffraction showed both that the extruded rod consisted mostly of metastable tau phase, with some of the equilibrium gamma(2) and beta phases, and that it largely retained the as-milled nanostructure. Magnetic measurements show a coercivity of <= 4.4 kOe and a magnetization at 10 kOe of <= 40 emu/g. In addition, extrusions exhibit greater than 95% of the theoretical density. This study opens a new window in the area of bulk MnAl magnets with improved magnetic properties for technological use.

  7. Enhanced Magnetic Properties in Antiferromagnetic-Core/Ferrimagnetic-Shell Nanoparticles

    PubMed Central

    Vasilakaki, Marianna; Trohidou, Kalliopi N.; Nogués, Josep

    2015-01-01

    Bi-magnetic core/shell nanoparticles are gaining increasing interest due to their foreseen applications. Inverse antiferromagnetic(AFM)/ferrimagnetic(FiM) core/shell nanoparticles are particularly appealing since they may overcome some of the limitations of conventional FiM/AFM systems. However, virtually no simulations exist on this type of morphology. Here we present systematic Metropolis Monte Carlo simulations of the exchange bias properties of such nanoparticles. The coercivity, HC, and loop shift, Hex, present a non-monotonic dependence with the core diameter and the shell thickness, in excellent agreement with the available experimental data. Additionally, we demonstrate novel unconventional behavior in FiM/AFM particles. Namely, while HC and Hex decrease upon increasing FiM thickness for small AFM cores (as expected), they show the opposite trend for large cores. This presents a counterintuitive FiM size dependence for large AFM cores that is attributed to the competition between core and shell contributions, which expands over a wider range of core diameters leading to non-vanishing Hex even for very large cores. Moreover, the results also hint different possible ways to enhance the experimental performance of inverse core/shell nanoparticles for diverse applications. PMID:25872473

  8. Development of integrated AC-DC magnetometer using high-Tc SQUID for magnetic properties evaluation of magnetic nanoparticles in solution

    NASA Astrophysics Data System (ADS)

    Mawardi Saari, Mohd; Takagi, Ryuki; Kusaka, Toki; Ishihara, Yuichi; Tsukamoto, Yuya; Sakai, Kenji; Kiwa, Toshihiko; Tsukada, Keiji

    2014-05-01

    We developed an integrated AC-DC magnetometer using a high critical temperature superconducting quantum interference device (high-Tc SQUID) to evaluate the static and dynamic magnetic properties of magnetic nanoparticles (MNPs) in solution. The flux-transformer method consisted of first-order planar and axial differential coils that were constructed for static and dynamic magnetization measurements, respectively. Vibrating-sample and harmonic detection techniques were used to reduce interference from excitation magnetic fields in the static and dynamic magnetization measurements, respectively. Static and dynamic magnetization measurements were performed on commercially available iron oxide nanoparticles in diluted solutions. The magnetic responses increased with the increase in concentration of the solutions in both measurement results. The magnetization curves showed that the diamagnetic signal due to the carrier liquid of the iron oxide nanoparticles existed in a dilute solution. Biasing with a proper DC magnetic field in the dynamic magnetization measurement resulted in improved signals of the second and third harmonics. Therefore, highly sensitive magnetic characterizations of MNPs utilizing the static and dynamic magnetization measurement are possible via the developed system.

  9. Enhanced magnetic properties of cobalt-doped graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Kaur, Navjot; Pal, Kaushik

    2017-04-01

    We have studied structural and magnetic properties of reduced graphene nanoribbons (GNRs) and cobalt (Co)-doped GNRs. The effect of Co was also investigated on the magnetic properties of pristine GNRs, which play vital role in contribution of calculated magnetic moment. Herein, we have synthesized the pristine GNRs and Co-doped GNRs via a simple chemical refluxing process. The analysis of synthesised materials were carried out using different techniques such as Field emission scanning electron microscopy (FESEM) with EDAX analysis and X-ray diffraction pattern were confirmed the doping of Co into the GNRs. Moreover, from morphological analysis (FESEM), impurity or dopant (Co) shows as adsorbed at the surface of GNRs. Raman analysis has proved that the incorporation of Co into graphitic structure creates more defective sites. The results obtained from VSM analysis is clearly revealed that enhanced saturation magnetization (Ms) from 13.08 × 10-2 emu/g to 37.35 × 10-2 emu/g, due to the presence of unbalanced electron spins in Co which may be responsible for higher saturation magnetization in case of Co-doped GNRs as comparison of pristine GNRs. The obtained interesting magnetic properties of Co-doped GNRs create much attention towards various applications including spintronics devices and some related fields.

  10. Single crystal Processing and magnetic properties of gadolinium nickel

    SciTech Connect

    Shreve, Andrew John

    2012-01-01

    GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd2O3 W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

  11. Magnetic nanoparticles: surface effects and properties related to biomedicine applications.

    PubMed

    Issa, Bashar; Obaidat, Ihab M; Albiss, Borhan A; Haik, Yousef

    2013-10-25

    Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10-100 μm), viruses, genes, down to proteins (3-50 nm). The optimization of the nanoparticles' size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents.

  12. Magnetic Nanoparticles: Surface Effects and Properties Related to Biomedicine Applications

    PubMed Central

    Issa, Bashar; Obaidat, Ihab M.; Albiss, Borhan A.; Haik, Yousef

    2013-01-01

    Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10–100 μm), viruses, genes, down to proteins (3–50 nm). The optimization of the nanoparticles’ size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents. PMID:24232575

  13. Particle size dependent rheological property in magnetic fluid

    NASA Astrophysics Data System (ADS)

    Wu, Jie; Pei, Lei; Xuan, Shouhu; Yan, Qifan; Gong, Xinglong

    2016-06-01

    The influence of the particle size on the rheological property of magnetic fluid was studied both by the experimental and computer simulation methods. Firstly, the magnetic fluids were prepared by dispersing Fe3O4 nanospheres with size varied from 40 nm to 100 nm and 200 nm in the solution. Then, the rheological properties were investigated and it was found that the relative magnetorheological effects increased with increasing the particle size. Finally, the molecular dynamic simulation was used to analyze the mechanical characteristics of the magnetic fluid and the chain-like model agreed well with the experimental result. The authentic chain-like structure observed by a microscope agreed with the simulation results. The three particles composed of the similar cluster nanostructure, thus they exhibited similar magnetic property. To this end, the unique assembling microstructures was the origination of the mechanical difference. And it was found that the higher MR (magnetorheological) effects of the large particle based magnetic fluid was originated from the stronger assembling microstructure under the applying magnetic field.

  14. Magnetic properties of superparamagnetic nanoparticles loaded into silicon nanotubes

    NASA Astrophysics Data System (ADS)

    Granitzer, Petra; Rumpf, Klemens; Gonzalez, Roberto; Coffer, Jeffery; Reissner, Michael

    2014-08-01

    In this work, the magnetic properties of silicon nanotubes (SiNTs) filled with Fe3O4 nanoparticles (NPs) are investigated. SiNTs with different wall thicknesses of 10 and 70 nm and an inner diameter of approximately 50 nm are prepared and filled with superparamagnetic iron oxide nanoparticles of 4 and 10 nm in diameter. The infiltration process of the NPs into the tubes and dependence on the wall-thickness is described. Furthermore, data from magnetization measurements of the nanocomposite systems are analyzed in terms of iron oxide nanoparticle size dependence. Such biocompatible nanocomposites have potential merit in the field of magnetically guided drug delivery vehicles.

  15. Growth, structure, morphology, and magnetic properties of Ni ferrite films

    PubMed Central

    2013-01-01

    The morphology, structure, and magnetic properties of nickel ferrite (NiFe2O4) films fabricated by radio frequency magnetron sputtering on Si(111) substrate have been investigated as functions of film thickness. Prepared films that have not undergone post-annealing show the better spinel crystal structure with increasing growth time. Meanwhile, the size of grain also increases, which induces the change of magnetic properties: saturation magnetization increased and coercivity increased at first and then decreased. Note that the sample of 10-nm thickness is the superparamagnetic property. Transmission electron microscopy displays that the film grew with a disorder structure at initial growth, then forms spinel crystal structure as its thickness increases, which is relative to lattice matching between substrate Si and NiFe2O4. PMID:23622034

  16. Optical, magnetic, and microwave properties of Ni/NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Rostamnejadi, Ali; Bagheri, Saber

    2017-04-01

    In this research, the optical, magnetic, and microwave properties of NiO and Ni/NiO nanoparticles have been studied. The absorbance spectra of the samples show the electronic d-d excitations with energy band gap of about 3.8 eV. The magnetization measurement confirms the existence of ferromagnetic phase at room temperature, which could be originated from the uncompensated surface spins or ferromagnetic clusters in the antiferromagnetic ground state of NiO nanoparticles. The microwave parameters such as ac conductivity, skin depth, electric and magnetic loss tangents, attenuation constant, and reflection loss have been calculated. While both magnetic and dielectric relaxation processes have been observed in the complex permeability and permittivity, the microwave absorption is mainly attributed to the dielectric relaxation processes.

  17. The effect of mechanical deformation to the magnetic properties of stainless steel 304

    NASA Astrophysics Data System (ADS)

    Mubarok, N.; Notonegoro, H. A.; Zaini Thosin, K. A.; Manaf, A.

    2016-11-01

    A study of a non-magnetic 304 austenitic stainless steel alloy through mechanical deformation has been done. These specimens are pipe usually used to deliver gas which contains corrosive oil fields. The metallographic observation of a 20% deformation shows the increase in the value of the magnetization, as compensation for the formation of martensite phase as a result of a mechanical treatment. Martensitic phase formed due to a shift in the structure of the z-axis due to the effects of pressure and shear from the cold rolled. The existence of martensite phase and magnetic properties conducted through x-ray diffraction and permagraf investigation. An identified x-ray diffraction pattern shows the presence of a new peak between 10°-30° angle indicate the mechanical deformation in crystallite structure. Furthermore, at in 20% distortion, the value of magnetization is increased above 0.2 T in small coercivity value and caused decreased the ability of corrosion resistant.

  18. Composite ceramic anvil cell for high-pressure magnetic properties measurements

    NASA Astrophysics Data System (ADS)

    Narayanaswamy, Suresh; Tallon, Jeff

    2013-06-01

    A ceramic-anvil based non-magnetic high-pressure cell has been developed for the magnetic properties measurement system (SQUID). The purpose of the development of this new cell is to undertake high-pressure measurements on samples like spin-crossover compounds, and antiferromagnetic materials with very weak magnetization beyond the existing capability of 1.2 GPa1. This new design is a combination of the diamond anvil cell (DAC) and piston-cylinder cell but very simplified by removing the laborious anvil-alignment procedure and making it user-friendly. A maximum pressure of 5 GPa was attained with this new cell using a 1.0 mm diameter culet composite anvils and a pre-indented CuBe gasket. We report the results of the magnetization on the CaFe2As2 single crystal sample using this new pressure-cell. Research Support: The Marsden Fund

  19. Composite Materials with Magnetically Aligned Carbon Nanoparticles Having Enhanced Electrical Properties and Methods of Preparation

    NASA Technical Reports Server (NTRS)

    Hong, Haiping (Inventor); Peterson, G.P. (Bud) (Inventor); Salem, David R. (Inventor)

    2016-01-01

    Magnetically aligned carbon nanoparticle composites have enhanced electrical properties. The composites comprise carbon nanoparticles, a host material, magnetically sensitive nanoparticles and a surfactant. In addition to enhanced electrical properties, the composites can have enhanced mechanical and thermal properties.

  20. Damage dosimetry and embrittlement monitoring of nuclear pressure vessels in real time by magnetic properties measurement

    SciTech Connect

    Stubbins, J.F.; Ougouag, A.M.; Williams, J.G.

    1992-07-01

    The objective of this project is to develop a technique for real-time monitoring of neutron dose and of the onset and progression of embrittlement in operating nuclear pressure vessels. The technique relies on the measurement of magnetic properties of steel and other magnetic materials which are extremely sensitive to radiation-induced properties changes. The approach being developed here is innovative and unique. It promises to be readily applicable to all existing and planned reactor structures. The significance of this program is that it addresses a major concern in the operation of existing nuclear pressure vessels. The development of microscopic defect clusters during irradiation in the nuclear pressure vessel beltline region leads to an increase in material yield strength and a concomitant decrease in ductility, or ability to absorb energy in fracture (i.e. fracture toughness). This decrease in fracture toughness is alarming since it may impair the ability of the pressure vessel to resist fracture during unusual loading situations.

  1. Magnetic properties of heat treated bacterial ferrihydrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Balaev, D. A.; Krasikov, A. A.; Dubrovskiy, A. A.; Popkov, S. I.; Stolyar, S. V.; Bayukov, O. A.; Iskhakov, R. S.; Ladygina, V. P.; Yaroslavtsev, R. N.

    2016-07-01

    The magnetic properties of ferrihydrite nanoparticles, which are products of vital functions of Klebsiella oxitoca bacteria, have been studied. The initial powder containing the nanoparticles in an organic shell was subjected to low-temperature (T=160 °C) heat treatment for up to 240 h. The bacterial ferrihydrite particles exhibit a superparamagnetic behavior. Their characteristic blocking temperature increases from 26 to 80 K with the heat treatment. Analysis of the magnetization curves with regard to the magnetic moment distribution function and antiferromagnetic contribution shows that the low-temperature heat treatment enhances the average magnetic moment of a particle; i.e., the nanoparticles coarsen, probably due to their partial agglomeration during heat treatment. It was established that the blocking temperature nonlinearly depends on the particle volume. Therefore, a model was proposed that takes into account both the bulk and surface magnetic anisotropy. Using this model, the bulk and surface magnetic anisotropy constants KV≈1.7×105 erg/cm3 and KS≈0.055 erg/cm2 have been determined. The effect of the surface magnetic anisotropy of ferrihydrite nanoparticles on the observed magnetic hysteresis loops is discussed.

  2. Magnetic properties and scale-up of nanostructured cobalt carbide permanent magnetic powders

    SciTech Connect

    Zamanpour, Mehdi Bennett, Steven; Taheri, Parisa; Chen, Yajie; Harris, Vincent G.

    2014-05-07

    Co{sub x}C magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co{sub 2}C and Co{sub 3}C phases possessing magnetization values exceeding 45 emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of surfactants, reaction temperature, and reaction duration on the crystallographic structure and magnetic properties of Co{sub x}C, while tetraethylene glycol was employed as a reducing agent. The role of the ratios of Co{sub 2}C and Co{sub 3}C phases in the admixture magnetic properties is discussed. The crystallographic structure and particle size of the Co{sub x}C nanoparticles were characterized by X-ray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 g per batch was demonstrated with no significant degradation of magnetic properties.

  3. Magnetic properties and scale-up of nanostructured cobalt carbide permanent magnetic powders

    NASA Astrophysics Data System (ADS)

    Zamanpour, Mehdi; Bennett, Steven; Taheri, Parisa; Chen, Yajie; Harris, Vincent G.

    2014-05-01

    CoxC magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co2C and Co3C phases possessing magnetization values exceeding 45 emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of surfactants, reaction temperature, and reaction duration on the crystallographic structure and magnetic properties of CoxC, while tetraethylene glycol was employed as a reducing agent. The role of the ratios of Co2C and Co3C phases in the admixture magnetic properties is discussed. The crystallographic structure and particle size of the CoxC nanoparticles were characterized by X-ray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 g per batch was demonstrated with no significant degradation of magnetic properties.

  4. Geometric properties of the magnetic Laplacian on the Euclidean 4-space

    SciTech Connect

    Kazmierowski, Dominique; Zinoun, Azzouz; Intissar, Ahmed

    2010-12-15

    When the four-dimensional Euclidean space is endowed with a covariant derivative that is either self-dual or antiself-dual and of constant curvature, the corresponding magnetic Laplacian is closely related to the sub-Laplacian of the quaternionic Heisenberg group. Some geometric properties of this operator are studied. In particular, it is proved that there exists a canonical orthogonal complex structure which provides a factorization in the sense of Schroedinger.

  5. Control of Magnetic Properties Across Metal to Insulator Transitions

    NASA Astrophysics Data System (ADS)

    de La Venta, Jose

    2013-03-01

    Controlling the magnetic properties of ferromagnetic (FM) thin films without magnetic fields is an on-going challenge in condensed matter physics with multiple technological implications. External stimuli and proximity effects are the most used methods to control the magnetic properties. An interesting possibility arises when ferromagnets are in proximity to materials that undergo a metal-insulator (MIT) and structural phase transition (SPT). The stress associated with the structural changes produces a magnetoelastic anisotropy in proximity coupled ferromagnetic films that allows controlling the magnetic properties without magnetic fields. Canonical examples of materials that undergo MIT and SPT are the vanadium oxides (VO2 and V2O3) . VO2 undergoes a metal/rutile to an insulator/monoclinic phase transition at 340 K. In V2O3 the transition at 160 K is from a metallic/rhombohedral to an insulating/ monoclinic phase. We have investigated the magnetic properties of different combinations of ferromagnetic (Ni, Co and Fe) and vanadium oxide thin films. The (0.32%) volume expansion in VO2 or the (1.4%) volume decrease in V2O3 across the MIT produces an interfacial stress in the FM overlayer. We show that the coercivities and magnetizations of the ferromagnetic films grown on vanadium oxides are strongly affected by the phase transition. The changes in coercivity can be as large as 168% and occur in a very narrow temperature interval. These effects can be controlled by the thickness and deposition conditions of the different ferromagnetic films. For VO2/Ni bilayers the large change in the coercivity occurring above room temperature opens the possibilities for technological applications. Work done in collaboration with Siming Wang, J. G. Ramirez, and Ivan K. Schuller. Funded by the US DoE, Office of Basic Energy Sciences, under Award FG03-87ER-45332 and the Air Force Office of Scientific Research No. FA9550-12-1-0381.

  6. Magnetic properties of nanoclusters embedded in a matrix

    NASA Astrophysics Data System (ADS)

    Sabiryanov, Renat; Qiang, You; Jaswal, Siataram; Sellmyer, David

    2001-03-01

    The technological demand to use smaller devices propelled studies of the properties of nanoscale magnetic clusters embedded in some medium. We present theoretical analysis of the magnetic behavior of the monodispersed Co nanoclusters embedded into Cu matrix. Co cluster embedded in Cu matrix, prepared by using beam deposition technique, show that (i) magnetizationof the Co clusters (M) is always much lower than the magnetization of bulk Co, (ii) M increases with the increase of the size of the co cluster (clusters between 300 atoms and 9000) were considered), (iii) magnetization of Co clusters decreases with the increase of the volume concentration of Co clusters at the same size of the single cluster. In order to understand this behavior we performed ab-initio calculations of the electronic structure and magnetic properties of small Co clusters embedded in Cu matrix using tight-binding linear-muffin-tin-orbitals and recursion method. The calculation for single Co cluster (1-321 atoms) show that the magnetic moments of inner atoms in the Co cluster is close to the Co bulk value while 2-3 outer shells have reduced moment (up to 20magnetization of the cluster increase with the size of the cluster as the surface effect but the total magnetic moment is much closer to the bulk value than experimental data. We found that interaction between clusters are very strong and oscillate with the distance between two clusters causing frustration in the system. We present model that takes the interdiffusion at the interface into account. The Monte Carlo simulations of the finite temperature magnetic behavior of the system will be presented.

  7. Magnetic properties of xenoliths from Yakut kimberlite pipes

    NASA Astrophysics Data System (ADS)

    Tselebrovskiy, Alexey; Maksimochkin, Valeriy

    2014-05-01

    Lower continental crust is poorly known due to its limited availability. One source of information about the formation of the lower crust is the study of xenoliths found in kimberlites, mainly peridotites, eclogites and other rocks made by the kimberlite magma to the surface from great depths. Magnetic methods can solve problems related on the one hand, the definition of the phase composition of natural ferrimagnetics responsible for the magnetic properties of rocks, and on the other - with the establishment of the thermodynamic conditions in which they were formed - their genesis. For example, in [1, 2], there were differences in the magnetic properties of kimberlites taken from tubes with different diamond productivity. In this work, studies have been conducted of the magnetic properties and mineralogy of xenoliths from 10 Yakut kimberlit pipes, courtesy of Doctor of Geological and Mineralogical Sciences V. K. Garanin. Found that the natural remanent magnetization (NRM) and magnetic susceptibility (k0) of the investigated samples varies widely: NRM = (0.002-12.59) A/m, k0 = (0.23-59.9)*10-3 SI. Magnetic properties vary by species: average NRM peridotites (0.002-0.32) A/m order of magnitude smaller eclogitic rocks (0.58-12.59) A/m. Thermomagnetic analysis (TMA) of the test samples showed the presence of xenoliths of the ferromagnetic phase with a Curie point close to Tc magnetite. Because of the high correlation between the values of NRM, k0 and ferrimagnetic saturation magnetization (SM) can be inferred that the magnetic properties of the rocks studied at temperatures above ambient is basically determined by the concentration of magnetite in them. Besides magnetite TMA were also identified ferrimagnetic phase with Curie temperatures from -50°C to -125°C. Mineralogical analysis performed on three samples of peridotite tubes Udachnaya, Yubileynaya and Mir and two samples of eclogite tubes Udachnaya and Komsomolskaya, showed that at temperatures below room

  8. Effects of heat treatment on crystallographic and magnetic properties of magnetic steels

    NASA Astrophysics Data System (ADS)

    Battistini, L.; Benasciutti, R.; Tassi, A.

    1994-05-01

    The keeper and the head of a modern electrovalve for electronic injection can be succesfully realized using AISI 430 ferromagnetic steel. Important improvements in the performance of the device, mainly in terms of its regularity and energy savings, are possible by means of a better comprehension of the origins of the steel's magnetic properties. The magnetic behaviour of the AISI 430 steel upon different heat treatments was investigated, looking for the best compromise between time saving in the heat treatments and the ensuing magnetic properties of the material. In particular, the relationships between the structural effects of the heat treatments and the magnetic behaviour of the samples were studied. Values of the coercive force Hc, residual induction Br, maximum permeability μ max and the approach to saturation values for H and B were determined by mean of a computerized permeameter, based on a Sanford-Bennet closed yoke for differently shaped samples.

  9. Magnetic properties of the ternary aluminide TbFe2Al10

    NASA Astrophysics Data System (ADS)

    Khandelwal, Ashish; Sharma, V. K.; Sharath Chandra, L. S.; Singh, M. N.; Sinha, A. K.; Chattopadhyay, M. K.

    2013-09-01

    The magnetic properties of the ternary aluminide TbFe2Al10 have been studied with the help of magnetization measurements. From the temperature and field dependence of magnetization, a detailed magnetic phase diagram of TbFe2Al10 has been constructed. While the high- and low-temperature phases (in low fields) of TbFe2Al10 are paramagnetic and antiferromagnetic respectively, the signature of a field-induced ferromagnetic phase is obtained in the magnetization results in the intermediate temperature regime. While it was already known that TbFe2Al10 has a ferrimagnetic phase in between the low-field antiferromagnetic and the high-field ferromagnetic phases, the present results indicate the presence of a second intermediate-field-induced ferrimagnetic phase in the compound, in between the first ferrimagnetic and the high-field ferromagnetic phases. The possible magnetic structure for this second ferrimagnetic phase is proposed on the basis of existing neutron diffraction results. The successive field-induced or metamagnetic transitions in TbFe2Al10 are found to be induced by temperature as well, when the applied magnetic field is appropriate. The present magnetization results also indicate the presence of short-range magnetic correlations in TbFe2Al10 well inside the paramagnetic regime. Owing to the presence of successive temperature and field-induced magnetic phase transitions, TbFe2Al10 is found to exhibit a moderate magneto-caloric effect with a maximum of 7.86 J kg-1K-1 at 18.5 K. The magneto-caloric effect is found to persist well inside the paramagnetic regime because of the presence of short-range magnetic correlations at these temperatures. This leads to a substantial refrigerant capacity in the material, which could be useful information for future technology.

  10. Dependence of the magnetic properties on the alignment magnetic field for NdFeB bonded magnets made from anisotropic HDDR powders

    NASA Astrophysics Data System (ADS)

    Gao, R. W.; Zhang, J. C.; Zhang, D. H.; Dai, Y. Y.; Meng, X. H.; Wang, Z. M.; Zhang, Y. J.; Liu, H. Q.

    1999-01-01

    The dependence of the hard magnetic properties on the alignment magnetic field for Nd(Fe,Co)B bonded magnets made from anisotropic HDDR powders is studied. The experimental results demonstrate that addition of a little Ga can induce a strong magnetic anisotropy in the HDDR magnetic powders. The application of an alignment magnetic field while the powders are bonded can increase the remanence, the coercivity and the maximum energy product in different degrees and the hard magnetic properties of the magnet are obviously improved with increasing alignment field.

  11. Thermophysical and Magnetic Properties of Carbon Beads Containing Cobalt Nanocrystallites

    NASA Astrophysics Data System (ADS)

    Izydorzak, M.; Skumiel, A.; Leonowicz, M.; Kaczmarek-Klinowska, M.; Pomogailo, A. D.; Dzhardimalieva, G. I.

    2012-04-01

    Magnetic Co-beads were fabricated in the course of a three-step procedure comprising preparation of a metal-acrylamide complex, followed by frontal polymerization and finally pyrolysis of the polymer. The composites obtained were composed of cobalt nanocrystallites stabilized in a carbon matrix built of disordered graphite. The crystallite size, material morphology, fraction of the magnetic component, and thus the magnetic properties can be tailored by a proper choice of the processing variables. The samples were subjected to an alternating magnetic field of different strengths ( H = 0 to 5 kA · m-1) at a frequency of f = 500 kHz. From the calorimetric measurements, we concluded that the relaxation processes dominate in the heat generation mechanism for the beads pyrolyzed at 773 K. For the beads pyrolyzed at 1073 K, significant values of magnetic properties, such as the coercive force and remanence give substantial contribution to the energy losses for hysteresis. The specific absorption coefficient ( SAR) related to the cobalt mass unit for the 1073 K pyrolyzed beads {({SAR} = 1340 W \\cdot g^{-1 }_cobalt)} is in very good conformity with the results obtained by other authors. The effective density power loss, caused by eddy currents, can be neglected for heating processes applied in magnetic hyperthermia. The Co-beads can potentially be applied for hyperthermia treatment.

  12. Electronic and magnetic properties of orthorhombic iron selenide

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.

    2016-02-01

    Iron orbitals in orthorhombic iron selenide (FeSe) can produce chargelike multipoles that are polar (parity-odd). Orbitals in question include Fe (3 d ), Fe (4 p ), and p -type ligands that participate in transport properties and bonding. The polar multipoles may contribute weak, space-group forbidden Bragg spots to diffraction patterns collected with x rays tuned in energy to a Fe atomic resonance (Templeton & Templeton scattering). Ordering of conventional, axial magnetic dipoles does not accompany the tetragonal-orthorhombic structural phase transition in FeSe, unlike other known iron-based superconductors. We initiate a new line of inquiry for this puzzling property of orthorhombic FeSe, using a hidden magnetic order that belongs to the m'm'm' magnetic crystal class. It is epitomized by the absence of ferromagnetism and axial magnetic dipoles and the appearance of magnetic monopoles and magnetoelectric quadrupoles. A similar magnetic order occurs in cuprate superconductors, yttrium barium copper oxide and Hg1201, where it was unveiled with the Kerr effect and in Bragg diffraction patterns revealed by polarized neutrons.

  13. Magnetic Properties of Different-Aged Chernozemic Soils

    NASA Astrophysics Data System (ADS)

    Fattakhova, Leysan; Shinkarev, Alexandr; Kosareva, Lina; Nourgaliev, Danis; Shinkarev, Aleksey; Kondrashina, Yuliya

    2016-04-01

    We investigated the magnetic properties and degree of mineral weathering in profiles of different-aged chernozemic soils derived from a uniform parent material. In this work, layer samples of virgin leached chernozem and chernozemic soils formed on the mound of archaeological earthy monument were used. The characterization of the magnetic properties was carried out on the data of the magnetometry and differential thermomagnetic analysis. The evaluation of the weathering degree was carried out on a loss on ignition, cation exchange capacity and X-ray phase analysis on the data of the original soil samples and samples of the heavy fraction of minerals. It was found that the magnetic susceptibility enhancement in humus profiles of newly formed chernozemic soils lagged significantly behind the organic matter content enhancement. This phenomenon is associated with differences in kinetic parameters of humus formation and structural and compositional transformation of the parent material. It is not enough time of 800-900 years to form a relatively "mature" magnetic profile. These findings are well consistent with the chemical kinetic model (Boyle et al., 2010) linking the formation of the soils magnetic susceptibility with the weathering of primary Fe silicate minerals. Different-aged chernozemic soils are at the first stage of formation of a magnetic profile when it is occur an active production of secondary ferrimagnetic minerals from Fe2+ released by primary minerals.

  14. Anomalous magnetic properties of mechanically milled cobalt oxide nanoparticles.

    PubMed

    Mishra, S R; Dubenko, I; Losby, J; Ghosh, l K; Khan, M; Ali, N

    2005-12-01

    Defect induced magnetic properties of CoO nanoparticles produced via mechanical ball milling have been assessed by detailed magnetic measurements. A progressive decrease in the particle size and a concomitant increase in the induced strain have been observed with the milling times. The mechanically milled nanoparticles of CoO exhibit anomalous magnetic properties such as FM hysteresis when compared with the unmilled CoO sample. The presence of weak ferromagnetism, with a highest value of magnetization of 0.532 emu/g at 10 K in the 100 h milled sample, is attributed to the uncompensated surface spins resulting from induced surface defects via mechanical milling. The ZFC coercive force, measured at 10 K, increases with milling time reaching a maximum value of 1066 Oe for the 100 h milled sample. The temperature dependent field-cooled (FC) and zero-field-cooled (ZFC) magnetic measurements indicate a presence of an exchange bias field arising from uncompensated moments generated by mechanical strain and the antiferromagnetic (AFM) core. The exchange bias field measured at 10 K reaches a value 210 Oe for the 50 h milled sample and decreases upon prolonged milling. The exchange bias field vanishes at a temperature approximately 200 K, a temperature much lower than the Neel temperature of CoO (TN approximately 291 K). The observed anomalous magnetic behavior of CoO could be interpreted in terms of the exchanged bias FM-AFM model.

  15. Magnetic properties of maraging steels in relation to nickel concentration

    SciTech Connect

    Ahmed, M.; Nasim, I.; Ayub, H.; Hasnain, K.

    1995-07-01

    Magnetic properties of maraging steels have been investigated as a function of nickel concentration. The alloys nickel content varied from 12 to 24 wt pct, while other alloying constituents were kept at a level maintained in the 18Ni-2,400 MPA-grade maraging steel. The magnetic properties were determined following aging for 1 hour in the temperature range of 450 to 750 C. In every alloy investigated, the coercive field increased with aging temperature, reaching a maximum around 670 C {+-} 30 C. The saturation magnetization values were lowest around temperatures where maximum coercive field was observed. The coercive field increased from {approximately}55 to {approximately}175 Oe ({approximately}4,380 to {approximately} 13,900 amp/meter) and the corresponding saturation magnetization decreased from {approximately}18,500 to {approximately}4,000 G ({approximately}1.85 to {approximately}0.4 T) in the alloys containing 12 and 24 wt pct Ni, respectively. The reverted austenite increased from 25 vol pct at 12 wt pct Ni to 10 vol pct at 24 wt pct Ni. The hardness and Charpy impact strength of the alloys have also been determined. An attempt has been made to correlate magnetic properties with different phase transformations occurring in maraging steels.

  16. Non-perturbative calculation of molecular magnetic properties within current-density functional theory.

    PubMed

    Tellgren, E I; Teale, A M; Furness, J W; Lange, K K; Ekström, U; Helgaker, T

    2014-01-21

    We present a novel implementation of Kohn-Sham density-functional theory utilizing London atomic orbitals as basis functions. External magnetic fields are treated non-perturbatively, which enable the study of both magnetic response properties and the effects of strong fields, using either standard density functionals or current-density functionals-the implementation is the first fully self-consistent implementation of the latter for molecules. Pilot applications are presented for the finite-field calculation of molecular magnetizabilities, hypermagnetizabilities, and nuclear magnetic resonance shielding constants, focusing on the impact of current-density functionals on the accuracy of the results. Existing current-density functionals based on the gauge-invariant vorticity are tested and found to be sensitive to numerical details of their implementation. Furthermore, when appropriately regularized, the resulting magnetic properties show no improvement over standard density-functional results. An advantage of the present implementation is the ability to apply density-functional theory to molecules in very strong magnetic fields, where the perturbative approach breaks down. Comparison with high accuracy full-configuration-interaction results show that the inadequacies of current-density approximations are exacerbated with increasing magnetic field strength. Standard density-functionals remain well behaved but fail to deliver high accuracy. The need for improved current-dependent density-functionals, and how they may be tested using the presented implementation, is discussed in light of our findings.

  17. Stochastic functional differential equations with infinite delay: Existence and uniqueness of solutions, solution maps, Markov properties, and ergodicity

    NASA Astrophysics Data System (ADS)

    Wu, Fuke; Yin, George; Mei, Hongwei

    2017-02-01

    This work is devoted to stochastic functional differential equations (SFDEs) with infinite delay. First, existence and uniqueness of the solutions of such equations are examined. Because the solutions of the delay equations are not Markov, a viable alternative for studying further asymptotic properties is to use solution maps or segment processes. By examining solution maps, this work investigates the Markov properties as well as the strong Markov properties. Also obtained are adaptivity and continuity, mean-square boundedness, and convergence of solution maps from different initial data. This paper then examines the ergodicity of underlying processes and establishes existence of the invariant measure for SFDEs with infinite delay under suitable conditions.

  18. GEMAS: Mineral magnetic properties of European agricultural soils

    NASA Astrophysics Data System (ADS)

    Kuzina, Dilyara; Kosareva, Lina; Fattakhova, Leysan; Fabian, Karl; Nourgaliev, Danis; Reimann, Clemens

    2015-04-01

    The GEMAS survey of European agricultural soil provides a unique opportunity to create the first comprehensive overview of mineral magnetic properties in agricultural soil on a continental scale. Samples from the upper 20 cm were taken in large agricultural fields (Ap-sample) at a density of 1 site/2500 km2. After air drying and sieving to < 2 mm, low (460 Hz), and high frequency (4600 Hz) magnetic susceptibility k was measured on 2500 samples using a Bartington MS2B sensor to obtain frequency dependence of magnetic susceptibility kfd. Hysteresis properties are determined using a J coercivity spectrometer, built in the paleomagnetic laboratory of Kazan University, providing for each sample a modified hysteresis loop, backfield curve, acquisition curve of isothermal remanent magnetization, and a viscous IRM decay spectrum. Each measurement set is obtained in a single run from zero field up to 1.5 T and back to -1.5 T, taking approximately 15 minutes. This allows to measure a wide range of magnetic parameters for large sample collections. Because the GEMAS geochemical atlas provides a comprehensive set of geochemical measurements characterizing the individual soil samples, the new data allow to study magnetic parameters in relation to chemical and geological parameters. The results show a clear large scale spatial distribution with e.g. broad distinct lows of k over sandy sediments of the last glaciation in central northern Europe and other sedimentary basins. More localized positive k anomalies occur near young volcanism, or old basalts exposed on the surface. On the other hand, frequency dependence of k displays a much more scattered behavior, indicating either high noise level, or large local variability. Clearly distinguishable, small-scale patterns in the randomized data set indicate that the latter is more likely. This indicates that local influences on soil magnetic properties, including anthropogenic effects, may be easier detected by frequency dependence

  19. Annealing effects on magnetic properties of silicone-coated iron-based soft magnetic composites

    NASA Astrophysics Data System (ADS)

    Wu, Shen; Sun, Aizhi; Zhai, Fuqiang; Wang, Jin; Zhang, Qian; Xu, Wenhuan; Logan, Philip; Volinsky, Alex A.

    2012-03-01

    This paper focuses on novel iron-based soft magnetic composites synthesis utilizing high thermal stability silicone resin to coat iron powder. The effect of an annealing treatment on the magnetic properties of synthesized magnets was investigated. The coated silicone insulating layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Silicone uniformly coated the powder surface, resulting in a reduction of the imaginary part of the permeability, thereby increasing the electrical resistivity and the operating frequency of the synthesized magnets. The annealing treatment increased the initial permeability, the maximum permeability, and the magnetic induction, and decreased the coercivity. Annealing at 580 °C increased the maximum permeability by 72.5%. The result of annealing at 580 °C shows that the ferromagnetic resonance frequency increased from 2 kHz for conventional epoxy resin coated samples to 80 kHz for the silicone resin insulated composites.

  20. Intrinsic Magnetism and Collective Magnetic Properties of Size-Selected Nanoparticles

    NASA Astrophysics Data System (ADS)

    Antoniak, C.; Friedenberger, N.; Trunova, A.; Meckenstock, R.; Kronast, F.; Fauth, K.; Farle, M.; Wende, H.

    Using size-selected spherical FePt nanoparticles and cubic Fe/Fe-oxide nanoparticles as examples, we discuss the recent progress in the determination of static and dynamic properties of nanomagnets. Synchroton radiation-based characterisation techniques in combination with detailed structural, chemical and morphological investigations by transmission and scanning electron microscopy allow the quantitative correlation between element-specific magnetic response and spin structure on the one hand and shape, crystal and electronic structure of the particles on the other hand. Examples of measurements of element-specific hysteresis loops of single 18 nm sized nanocubes are discussed. Magnetic anisotropy of superparamagnetic ensembles and their dynamic magnetic response are investigated by ferromagnetic resonance as a function of temperature at different microwave frequencies. Such investigations allow the determination of the magnetic relaxation and the extraction of the average magnetic anisotropy energy density of the individual particles.

  1. Magnetic properties of tephras from Lake Van (Eastern Turkey)

    NASA Astrophysics Data System (ADS)

    Makaroglu, Ozlem; Caǧatay, Namık; Pesonen, Lauri J.; Orbay, Naci

    2013-04-01

    Here we present magnetic properties of tephra layers in the cores taken from Lake Van, Eastern Anatolia, Turkey. Lake Van is the fourth largest terminal Lake in the world by volume (607 km3). It is 460 m deep and has a salinity of 21.4 per mil and a pH of 9.81. It is located on the East Anatolian Plateau with present day water level of 1648 m.a.s.l., and surrounded by large stratovolcanoes Nemrut, Suphan, Tendurek, and Ararat to the west and north. It has accumulated varved-sediments with tephra units, which all provide important paleoenvironmental records. After a seismic survey, four different locations were selected for coring in Lake Van, with water depths varying between 60 m and 90 m. Four cores having between 3 and 4.8 m length were analyzed for for element geochemistry using XRF Core Scanner analysis. The sub-samples were taken into plastic boxes with a volume of 6.4 cm3 for mineral magnetic analysis. The mineral magnetic measurements included magnetic susceptibility (χ), anhysteretic remanent magnetisation (ARM), isothermal remanent magnetisation (IRM), hysteresis properties and thermomagnetic analyses. According to the mineral magnetic measurements and geochemical analysis, we identified the five tephra layers (T1-T5). These tephra units were correlated with the previously varve-dated units of Landmann et al. (2011). The varve ages of the tephra layers were used to obtain the age-depth model for the cores. According to the age models the cores extend back to 9500 ka BP (varve years). Down-core profiles of all the magnetic properties are highly correlatable between different cores, suggesting that the magnetic records are of regional character. ARM values are found to be more convenient than χ values for correlating the tephra layers. The hysteresis parameters of samples taken from these layers indicate that they are within Pseudo Single Domain range. IRM curves show that low coersivity magnetic minerals are dominated in all tephra layers. Measurements

  2. Transport properties of interacting magnetic islands in tokamak plasmas

    SciTech Connect

    Gianakon, T.A.; Callen, J.D.; Hegna, C.C.

    1993-10-01

    This paper explores the equilibrium and transient transport properties of a mixed magnetic topology model for tokamak equilibria. The magnetic topology is composed of a discrete set of mostly non-overlapping magnetic islands centered on the low-order rational surfaces. Transport across the island regions is fast due to parallel transport along the stochastic magnetic field lines about the separatrix of each island. Transport between island regions is assumed to be slow due to a low residual cross-field transport. In equilibrium, such a model leads to: a nonlinear dependence of the heat flux on the pressure gradient; a power balance diffusion coefficient which increases from core to edge; and profile resiliency. Transiently, such a model also exhibits a heat pulse diffusion coefficient larger than the power balance diffusion coefficient.

  3. Graph-topological approach to magnetic properties of benzenoid hydrocarbons.

    PubMed

    Ciesielski, Arkadiusz; Krygowski, Tadeusz M; Cyrański, Michał K; Dobrowolski, Michał A; Aihara, Jun-ichi

    2009-12-28

    Application of topological properties and graph theory to benzenoid hydrocarbons allowed us to construct an effective approach interpreting ring current formation in molecules when exposed to an external magnetic field. Transformation of unexcited canonical structures for molecules of 34 benzenoid hydrocarbons into circuit structures and then to directed circuit structures allowed us to define global magnetic characteristics (GMC). GMC/n(2) values correlate very well with exaltation of magnetic susceptibility DeltaLambda/n(2) (computed at the CSGT/B3LYP/6-311G** level of theory by using optimized geometries at the B3LYP/6-311G** DFT level) with cc = 0.993. If the approach is applied to individual rings, then the correlation between local magnetic characteristics (LMC) for 129 various rings of 34 benzenoid hydrocarbons and NICS(1) works with cc = -0.975.

  4. Effect of interactions on edge property measurements in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    McMichael, Robert; Zhu, Meng

    2010-03-01

    The edges of patterned thin films are important, especially in magnetic nanostructures. In previous work, it has been shown that the magnetic properties of film edges in Ni80Fe20 (Py) stripe arrays can be measured with a precision of a few percent using the ferromagnetic resonance (FMR) of localized edge modes. In this work, we extend this measurement technique to multilayer films, showing the effects of interactions between edge modes in the magnetic layers. We fabricate magnetic multilayer stripes consisting of 10 nm Py / x Cu / 20 nm Py, where x ranges from 1 nm to 20 nm, and we find that the edge saturation fields of both Py layers increase as the spacer is reduced, indicating enhanced magnetostatic interactions. An approximate analytical model based on the static dipolar interactions is used to simulate experimental and micromagnetic model data.

  5. Versatile magnetometer assembly for characterizing magnetic properties of nanoparticles

    NASA Astrophysics Data System (ADS)

    Araujo, J. F. D. F.; Bruno, A. C.; Louro, S. R. W.

    2015-10-01

    We constructed a versatile magnetometer assembly for characterizing iron oxide nanoparticles. The magnetometer can be operated at room temperature or inside a cryocooler at temperatures as low as 6 K. The magnetometer's sensor can be easily exchanged and different detection electronics can be used. We tested the assembly with a non-cryogenic commercial Hall sensor and a benchtop multimeter in a four-wire resistance measurement scheme. A magnetic moment sensitivity of 8.5 × 10-8 Am2 was obtained with this configuration. To illustrate the capability of the assembly, we synthesized iron oxide nanoparticles coated with different amounts of a triblock copolymer, Pluronic F-127, and characterized their magnetic properties. We determined that the polymer coating does not affect the magnetization of the particles at room temperature and demonstrates that it is possible to estimate the average size of coating layers from measurements of the magnetic field of the sample.

  6. Thermodynamic properties of the magnetized Coulomb crystal lattices

    NASA Astrophysics Data System (ADS)

    Kozhberov, A. A.

    2016-08-01

    It is thought that Coulomb crystals of ions with hexagonal close-packed lattice may form in the crust of strongly-magnetized neutron stars (magnetars). In this work we are trying to verify this prediction assuming that the direction of the magnetic field corresponds to the minimum of the zero-point energy. We also continue a detailed study of vibration modes and thermodynamic properties of magnetized Coulomb crystals in a wide range of temperatures and magnetic fields. It is demonstrated that the total Helmholtz free energy of the body-centered cubic Coulomb crystal is always lower than that of the Coulomb crystal with hexagonal close-packed or face-centered cubic lattice, which casts doubt on the hypothesis above.

  7. Versatile magnetometer assembly for characterizing magnetic properties of nanoparticles.

    PubMed

    Araujo, J F D F; Bruno, A C; Louro, S R W

    2015-10-01

    We constructed a versatile magnetometer assembly for characterizing iron oxide nanoparticles. The magnetometer can be operated at room temperature or inside a cryocooler at temperatures as low as 6 K. The magnetometer's sensor can be easily exchanged and different detection electronics can be used. We tested the assembly with a non-cryogenic commercial Hall sensor and a benchtop multimeter in a four-wire resistance measurement scheme. A magnetic moment sensitivity of 8.5 × 10(-8) Am(2) was obtained with this configuration. To illustrate the capability of the assembly, we synthesized iron oxide nanoparticles coated with different amounts of a triblock copolymer, Pluronic F-127, and characterized their magnetic properties. We determined that the polymer coating does not affect the magnetization of the particles at room temperature and demonstrates that it is possible to estimate the average size of coating layers from measurements of the magnetic field of the sample.

  8. Versatile magnetometer assembly for characterizing magnetic properties of nanoparticles

    SciTech Connect

    Araujo, J. F. D. F.; Bruno, A. C.; Louro, S. R. W.

    2015-10-15

    We constructed a versatile magnetometer assembly for characterizing iron oxide nanoparticles. The magnetometer can be operated at room temperature or inside a cryocooler at temperatures as low as 6 K. The magnetometer’s sensor can be easily exchanged and different detection electronics can be used. We tested the assembly with a non-cryogenic commercial Hall sensor and a benchtop multimeter in a four-wire resistance measurement scheme. A magnetic moment sensitivity of 8.5 × 10{sup −8} Am{sup 2} was obtained with this configuration. To illustrate the capability of the assembly, we synthesized iron oxide nanoparticles coated with different amounts of a triblock copolymer, Pluronic F-127, and characterized their magnetic properties. We determined that the polymer coating does not affect the magnetization of the particles at room temperature and demonstrates that it is possible to estimate the average size of coating layers from measurements of the magnetic field of the sample.

  9. Transport and magnetic properties of CMR manganites with antidot arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Du, Kai; Niu, Jiebin; Wei, Wengang; Chen, Jinjie; Yin, Lifeng; Shen, Jian

    2014-03-01

    We fabricated and characterized a series of manganites thin film samples with different densities of antidots. With increasing antidot density, the samples show higher MIT temperature and lower resistivity under zero and low magnetic fields. These differences become smaller and finally vanished when the magnetic field is large enough to melt the charge ordered phase in the system, which is expected in our theoretical explanations. We believe that emerging edge states at the ring of antidotes play a significant role for observed metal-insulator transition and electrical transport properties, which are of great importance of real storage and sensor device design. Magnetic property measurements and theoretical simulation also support the conclusion. These results open up new ways to control and tune the strongly correlated oxides without introduce any new material or field.

  10. Preparation and electrical properties of oil-based magnetic fluids

    NASA Astrophysics Data System (ADS)

    Sartoratto, P. P. C.; Neto, A. V. S.; Lima, E. C. D.; Rodrigues de Sá, A. L. C.; Morais, P. C.

    2005-05-01

    This paper describes an improvement in the preparation of magnetic fluids for electrical transformers. The samples are based on surface-coated maghemite nanoparticles dispersed in transformer insulating oil. Colloidal stability at 90°C was higher for oleate-grafted maghemite-based magnetic fluid, whereas decanoate and dodecanoate-grafted samples were very unstable. Electrical properties were evaluated for samples containing 0.80%-0.0040% maghemite volume fractions. Relative permittivity varied from 8.8 to 2.1 and the minimum value of the loss factor was 12% for the most diluted sample. The resistivity falls in the range of 0.7-2.5×1010Ωm, whereas the ac dielectric strength varied from 70to79kV. These physical characteristics reveal remarkable step forward in the properties of the magnetic fluid samples and may result in better operation of electrical transformers.

  11. Influence of Barium Hexaferrite on Magnetic Properties of Hydroxyapatite Ceramics.

    PubMed

    Jarupoom, P; Jaita, P

    2015-11-01

    Hydroxyapatite (HA) powders was derived from natural bovine bone by sequence of thermal processes. The barium hexaferrite (BF) find magnetic powders were added into HA powders in ratio of 1-3 vol.%. The HA-BF ceramics were prepared by a solid state reaction method and sintered at 1250 degrees C for 2 h. Effects of BF additive on structural, physical and magnetic properties of HA ceramics were investigated. X-ray diffraction revealed that all HA-BF samples showed a main phase of high purity hydroxyapatite [Ca10(PO4)6(OH)2] with calcium and phosphate molar ratio of 1.67. The addition of BF into HA inhibited grain growth and caused an improvement of mechanical properties. The M-H hysteresis loops also showed an improvement in magnetic behavior for higher content of BF. Moreover, in vitro bioactivity test indicated that the 2-3 vol.% sample may be suitable for biological applications.

  12. Transport properties of graphene under periodic and quasiperiodic magnetic superlattices

    NASA Astrophysics Data System (ADS)

    Lu, Wei-Tao; Wang, Shun-Jin; Wang, Yong-Long; Jiang, Hua; Li, Wen

    2013-08-01

    We study the transmission of Dirac electrons through the one-dimensional periodic, Fibonacci, and Thue-Morse magnetic superlattices (MS), which can be realized by two different magnetic blocks arranged in certain sequences in graphene. The numerical results show that the transmission as a function of incident energy presents regular resonance splitting effect in periodic MS due to the split energy spectrum. For the quasiperiodic MS with more layers, they exhibit rich transmission patterns. In particular, the transmission in Fibonacci MS presents scaling property and fragmented behavior with self-similarity, while the transmission in Thue-Morse MS presents more perfect resonant peaks which are related to the completely transparent states. Furthermore, these interesting properties are robust against the profile of MS, but dependent on the magnetic structure parameters and the transverse wave vector.

  13. On a few properties of very dilute matter frozen in space magnetic fields

    NASA Astrophysics Data System (ADS)

    Berdichevsky, D. B.; Schefers, K.

    2014-12-01

    For a case study, the flux-rope (FR) that passed Earth on June 2, 2014(1) (see also listing of magnetic clouds and their properties in the Wind SC MFI science team site at http://wind.gsfc.nasa.gov/mfi/mag_cloud_S1.html), we proceed to interpret plasma and magnetic field observations in the context of MHD. The observations used are 3s average interplanetary magnetic field (Wind/MFI instrument) and 3s plasma (Wind/SWE instruments) data(2). After identifying the observed correlation between electron density, temperature and pressure in the plasma frame of reference we proceed to establish the existence of a relationship between these plasma observables with the magnetic field pressure. By assuming ideal MHD conditions to be valid we proceed to confirm that the medium is diamagnetic, as is to be expected for the MHD state of matter and magnetic field which is assumed to be a superconducting medium. Additionally we infer the presence of magnetization work, as well as a few other constitutive properties of this state of matter. 1 Berdichevsky D. B., R. P. Lepping, and C. J. Farrugia, Geometric considerations of the evolution of magnetic flux ropes, Phys. Rev. E67, doi:10.1103/PhysRevE.036405. Lepping R. P. et al, A summary of Wind magnetic clouds for years 1995 - 2003: model-fitted parameters, associated errors and classifications, Ann. Geophysicae, 24, 215-245, 2006.2006 2 Ogilvie, K. W., et al, SWE, A comprehensive plasma instrument for the Wind spacecraft, Space Sci. Rev., 71, 55 - 77, 1995; Lepping R. P., et al , The Wind Magnetic Field Investigation, Space Sci. Rev., 71, 207 - 229, 1995.

  14. Thermophysical and Magnetic Properties of Carbon Beads Containing Nickel Nanocrystallites

    NASA Astrophysics Data System (ADS)

    Skumiel, A.; Izydorzak, M.; Leonowicz, M.; Pomogailo, A. D.; Dzhardimalieva, G. I.

    2011-09-01

    Ferromagnetic and superparamagnetic nickel nanocrystallites, stabilized in a carbon matrix, were prepared by a three-step procedure including formation of a Ni acrylamide complex, followed by frontal polymerization and pyrolysis of the polymer at various temperatures. It was found that the procedure applied enables fabrication of magnetic beads containing metallic nanocrystallites embedded in a carbon matrix. The size of the crystallites, their morphology, volume fraction, and magnetic properties can be tailored by the pyrolysis temperature. The size of the crystallites affects their behavior in an external magnetic field, i.e., a heating process is the most effective for a sample pyrolyzed at 873 K. The revealed H n-type dependence of the temperature increase rate, (d T/d t) t=0, on the amplitude of the magnetic field indicates the presence of both superparamagnetic and ferromagnetic particles in all the samples studied since n > 2. For the superparamagnetic particles, the heating mechanism is associated with Néel relaxation. For the lower values of the magnetic field amplitude, H < H 0, the relaxation losses dominate whereas for the opposite case, H > H 0, the magnetic hysteresis is the main source of thermal energy losses. The composites containing magnetic Ni nanocrystallites entrapped in a carbon matrix can be potentially applied for hyperthermia treatment.

  15. Structural, magnetic, and transport properties of Permalloy for spintronic experiments

    SciTech Connect

    Nahrwold, Gesche; Scholtyssek, Jan M.; Motl-Ziegler, Sandra; Albrecht, Ole; Merkt, Ulrich; Meier, Guido

    2010-07-15

    Permalloy (Ni{sub 80}Fe{sub 20}) is broadly used to prepare magnetic nanostructures for high-frequency experiments where the magnetization is either excited by electrical currents or magnetic fields. Detailed knowledge of the material properties is mandatory for thorough understanding its magnetization dynamics. In this work, thin Permalloy films are grown by dc-magnetron sputtering on heated substrates and by thermal evaporation with subsequent annealing. The specific resistance is determined by van der Pauw methods. Point-contact Andreev reflection is employed to determine the spin polarization of the films. The topography is imaged by atomic-force microscopy, and the magnetic microstructure by magnetic-force microscopy. Transmission-electron microscopy and transmission-electron diffraction are performed to determine atomic composition, crystal structure, and morphology. From ferromagnetic resonance absorption spectra the saturation magnetization, the anisotropy, and the Gilbert damping parameter are determined. Coercive fields and anisotropy are measured by magneto-optical Kerr magnetometry. The sum of the findings enables optimization of Permalloy for spintronic experiments.

  16. Magnetorheological properties of a magnetic nanofluid with dispersed carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Felicia, Leona J.; Philip, John

    2014-02-01

    We investigate the effect of multiwalled carbon nanotubes (MWCNTs) on the magnetorheological properties of an oil based magnetic nanofluid (ferrofluid). The shear resistant plateau observed in a pure ferrofluid disappears when 0.5 wt % of MWCNT is incorporated. The yield stress values of the composite system are slightly smaller than that of the pure system. This shows that the presence of carbon nanotubes (CNTs) weakens the magnetic field induced microstructure of the ferrofluid due to their interaction that affects the hydrodynamic and magnetic interactions between the dispersed nanoparticles. Interestingly, the Mason number plots for both the pure and composite system show scaling of the viscosity curves onto a single master curve for magnetic fields of 80 mT and above while deviations are observed for lower magnetic fields. The weakening of the ferrofluid microstructure in the presence of CNTs is further evident in the amplitude sweep measurements where the linear viscoelastic region develops only at a higher magnetic field strength compared to lower magnetic fields in pure ferrofluids. These results are useful for tailoring ferrofluids with a faster response for various applications.

  17. Magnetic Properties of Ubiquitous yet Underrated Antiferromagnetic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Guyodo, Y. J.; Till, J. L.; Lagroix, F.; Bonville, P.; Penn, R.; Sainctavit, P.; Ona-Nguema, G.; Morin, G.

    2013-05-01

    Ferrihydrite, lepidocrocite and goethite are antiferromagnetic, weakly "ferromagnetic" iron oxyhydroxides that are commonly found in diverse environments, including ground waters and streams, sediments, soils, or acid mine drainage. One of them, ferrihydrite, constitutes the mineral core of ferritin, a vital iron storage protein. Iron oxyhydroxides take part in multiple biological and abiological processes, and can evolve, under changing environmental or geological conditions, to more magnetic phases such as hematite, maghemite, or magnetite. Therefore, they represent key minerals with regard to paleoclimate, paleoenvironmental, and paleomagnetic studies. We will present low temperature magnetic properties acquired on fully characterized synthetic iron oxyhydroxides. The complex nature of the magnetism of these minerals is revealed by comparing magnetic data with other types of characterizations such as high-resolution transmission electron microscopy or synchrotron X-ray magnetic circular dichroism (XMCD), or when the early-stages of solid-state alteration (under oxidizing or reducing atmosphere) are studied. In particular, we will present resent results about the structure of 6-line ferrihydrite, about the possible presence of ferri-magnetic nano-clusters in lepidocrocite, and about uncompensated magnetic moments in goethite nanoparticles.

  18. Confinining properties of QCD in strong magnetic backgrounds

    NASA Astrophysics Data System (ADS)

    Bonati, Claudio; D'Elia, Massimo; Mariti, Marco; Mesiti, Michele; Negro, Francesco; Rucci, Andrea; Sanfilippo, Francesco

    2017-03-01

    Strong magnetic backgrounds are known to modify QCD properties at a nonperturbative level. We discuss recent lattice results, obtained for Nf = 2 + 1 QCD with physical quark masses, concerning in particular the modifications and the anisotropies induced at the level of the static quark-antiquark potential, both at zero and finite temperature.

  19. Magnetic and structural properties of manganese ion implanted silicon

    NASA Astrophysics Data System (ADS)

    Awo-Affouda, Chaffra A.

    2007-12-01

    This thesis focuses on semiconductor based spin electronics. The integration of ferromagnetic regions into semiconductor "spintronic" devices to produce spin polarized current is a dynamic research area. One avenue is to make conventional semiconductors ferromagnetic by doping with a transition metal impurity such as Mn. For this, we first investigated the magnetic properties of Mn-implanted Si. We were able to measure above room temperature ferromagnetic hysteresis loops. The high Curie temperature obtained (>400 K), indicated that the synthesis of a technologically useful Si-based magnetic semiconductor is possible. We then focused on studying the structure of the implanted samples in order to establish a correlation between the magnetic and structural properties. The structural investigation involved secondary ion mass spectrometry, Rutherford backscattering, and transmission electron microscopy (TEM) as the main characterization techniques. The combination of the structural and magnetic studies allowed us to isolate an "active" region from which the ferromagnetism originates. We then found that the magnetic properties of the samples are strongly dependant on the interaction of the Mn atoms with the residual implant damage. The evolution of the Mn concentration profiles was also found to be closely related to the distribution of the Si lattice defects. We also observed the formation of Mn rich secondary phases at high enough annealing temperatures >800°C. However, we argued that theses crystallites cannot account for all the observed magnetic properties due to the low Curie temperature of these compounds in bulk form. We concluded that achieving a room temperature Si-based DMS has great potential but careful synthesis of this material system is needed to prevent secondary phase formation.

  20. Structural and magnetic properties of polymer coated iron based nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Balakrishnan, Srinivasan

    Magnetic nanoparticles have recently attracted much attention for potential biomedical applications such as targeted drug delivery, magnetic resonance imaging contrast agents and hyperthermia treatment of cancerous cells. Future research on biomedical applications also includes use of magnetic nanoparticles for cell and DNA separation. By functionalizing magnetic nanoparticles with cells or DNA selective biomolecules, the particles attach to the target and are removed from the sample upon passing through magnetic field gradients. The field gradients apply a force that attracts the particles given by the equation F = ∇(m · B), where m is the magnetization of the MNP, and B is the applied magnetic field. This type of magnetic manipulation is potential for in vivo applications such as targeted drug delivery, magnetic resonance imaging contrast enhancement and hyperthermia treatment of cancer. The magnitude of the field gradients of magnetic nanoparticles are significantly reduced due to the inverse square law dependence of magnetic field strength and subsequently the forces set up are reduced. Although the research in this field has focused primarily on iron oxide nanoparticles, these oxide nanoparticles have a low magnetization that renders them ineffective, at the distances required for in vivo applications, due to the reduced forces felt by the nanoparticles. Successful implementation of such magnetic nanoparticles based system in vivo may require higher magnetization. The aim of this proposal is to synthesize high magnetization Fe-based MNPs functionalized with artificial proteins. The research described in this dissertation focuses on synthesis, size control, structural and magnetic characterization and associated experimental studies to characterize their properties for application in magnetic fluid hyperthermia and magnetic resonance imaging applications. The method used for the synthesis of the Fe-based nanoparticles is the conventional borohydride

  1. Superconducting and magnetic properties of Sr3Ir4Sn13

    DOE PAGES

    Biswas, P. K.; Amato, A.; Khasanov, R.; ...

    2014-10-10

    In this research, magnetization and muon spin relaxation or rotation (µSR) measurements have been performed to study the superconducting and magnetic properties of Sr₃Ir₄Sn₁₃. From magnetization measurements the lower and upper critical fields of Sr₃Ir₄Sn₁₃ are found to be 81(1) Oe and 14.4(2) kOe, respectively. Zero-field µSR data show no sign of any magnetic ordering or weak magnetism in Sr₃Ir₄Sn₁₃. Transverse-field µSR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth λ. The dependence of λ⁻² with temperature is consistent with the existence of single s-wave energy gap in the superconducting state of Sr₃Ir₄Sn₁₃ withmore » a gap value of 0.82(2) meV at absolute zero temperature. The magnetic penetration depth at zero temperature λ(0) is 291(3) nm. The ratio Δ(0)/kBTc = 2.1(1) indicates that Sr₃Ir₄Sn₁₃ should be considered as a strong-coupling superconductor.« less

  2. Interest and design of magnetic properties measurements on planetary and asteroid landers

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Gattacceca, J.; Eisenlohr, P.

    2003-04-01

    Intrinsic magnetic properties, like susceptibility X, provide a precise determination of the iron phases with a penetration depth not available with other chemical and mineralogical sensing tools, thus allowing to unravel space weathering effects. Systematic studies of meteorites (see PS10.01 abstract of Rochette et al.) demonstrate that X measurements on asteroid surface could be a very efficient way to assign a meteorite class to a given asteroid. Another application could be the characterisation of the higly magnetic martian regolith. On the other hand natural remanent magnetization (NRM) measurements are crucial to interpret magnetic field anomalies such as those found on Mars and Moon, and likely to be found on Mercury. NRM gives also access to past magnetic fields and extinct planetary dynamo. Rugged, light and low consumption systems already exist for such measurements on earth and we will present a scheme to integrate both magnetic susceptibility (using a LC oscillator) and NRM (using a 3 axis fluxgate) on a lander to offer a versatile instrument package for every mission involving a lander. For the LC oscillator calibration of the geometric factor will be presented on a set of pebble of variable uneven shape and size. The fluxgate can be used both for making local magnetic anomaly maps, thus investigating subsurface structures, and for evaluating NRM of individual boulders.

  3. Reinforced magnetic properties of Ni-doped BiFeO3 ceramic

    NASA Astrophysics Data System (ADS)

    Hwang, J. S.; Yoo, Y. J.; Lee, Y. P.; Kang, J.-H.; Lee, K. H.; Lee, B. W.; Park, S. Y.

    2016-08-01

    Multiferroic materials attract considerable interest because of the wide range of potential applications such as spintronic devices, data storage devices and sensors. As a strong candidate for the applications among the limited list of single-phase multiferroic materials, BiFeO3 (BFO) is a quite attractive material due to its multiferroic properties at room temperature (RT). However, BFO is widely known to have large leakage current and small spontaneous polarization due to the existence of crystalline defects such as oxygen vacancies. Furthermore, the magnetic moment of pure BFO is very weak owing to its antiferromagnetic nature. In this paper, the effects of Ni2+ substitution on the magnetic properties of bulk BFO were investigated. BFO, and BiFe0.99Ni0.01O3, BiFe0.98Ni0.02O3 and BiFe0.97Ni0.03O3 (BFNO: Ni-doped BFO) ceramics were prepared by solid-state reaction and rapid sintering, and analyzed by structural and magnetic-property measurements. The leakage current density was measured at RT by using a standard ferroelectric tester. All the Ni-doped BFO samples exhibited the similar rhombohedral perovskite structure ( R3c) to that of BFO. The magnetic properties of Ni-doped BFO were much enhanced with respect to BFO prepared at the same conditions, because the enhanced ferromagnetic interaction is caused by the Fe/Ni coupling.

  4. Magnetic microstructure and magnetic properties of uniaxial itinerant ferromagnet Fe3GeTe2

    DOE PAGES

    León-Brito, Neliza; Bauer, Eric Dietzgen; Ronning, Filip; ...

    2016-08-28

    Here, magnetic force microscopy was used to observe the magnetic microstructure of Fe3GeTe2 at 4 K on the (001) surface. The surface magnetic structure consists of a two-phase domain branching pattern that is characteristic for highly uniaxial magnets in the plane perpendicular to the magnetic easy axis. The average surface magnetic domain width Ds = 1.3 μm determined from this pattern, in combination with intrinsic properties calculated from bulk magnetization data (the saturation magnetization Ms = 376 emu/cm3 and the uniaxial magnetocrystalline anisotropy constant Ku = 1.46 × 107 erg/cm3), was used to determine the following micromagnetic parameters for Fe3GeTe2more » from phenomenological models: the domain wall energy γw = 4.7 erg/cm2, the domain wall thickness δw = 2.5 nm, the exchange stiffness constant Aex = 0.95 × 10–7 erg/cm, the exchange length lex = 2.3 nm, and the critical single domain particle diameter dc = 470 nm.« less

  5. Magnetic microstructure and magnetic properties of uniaxial itinerant ferromagnet Fe3GeTe2

    NASA Astrophysics Data System (ADS)

    León-Brito, N.; Bauer, E. D.; Ronning, F.; Thompson, J. D.; Movshovich, R.

    2016-08-01

    Magnetic force microscopy was used to observe the magnetic microstructure of Fe3GeTe2 at 4 K on the (001) surface. The surface magnetic structure consists of a two-phase domain branching pattern that is characteristic for highly uniaxial magnets in the plane perpendicular to the magnetic easy axis. The average surface magnetic domain width Ds = 1.3 μm determined from this pattern, in combination with intrinsic properties calculated from bulk magnetization data (the saturation magnetization Ms = 376 emu/cm3 and the uniaxial magnetocrystalline anisotropy constant Ku = 1.46 × 107 erg/cm3), was used to determine the following micromagnetic parameters for Fe3GeTe2 from phenomenological models: the domain wall energy γw = 4.7 erg/cm2, the domain wall thickness δw = 2.5 nm, the exchange stiffness constant Aex = 0.95 × 10-7 erg/cm, the exchange length lex = 2.3 nm, and the critical single domain particle diameter dc = 470 nm.

  6. Synthesis, characterization and magnetic properties of carbon nanotubes decorated with magnetic MIIFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ali, Syed Danish; Hussain, Syed Tajammul; Gilani, Syeda Rubina

    2013-04-01

    In this study, a simple, efficient and reproducible microemulsion method was applied for the successful decoration of carbon nanotubes (CNTs) with magnetic MIIFe2O4 (M = Co, Ni, Cu, Zn) nanoparticles. The structure, composition and morphology of the prepared nanocomposite materials were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The magnetic properties were investigated by the vibrating sample magnetometer (VSM). The SEM results illustrated that large quantity of MIIFe2O4 nanoparticles were uniformly decorated around the circumference of CNTs and the sizes of the nanoparticles ranged from 15 to 20 nm. Magnetic hysteresis loop measurements revealed that all the MIIFe2O4/CNTs nanocomposites displayed ferromagnetic behavior at 300 K and can be manipulated using an external magnetic field. The CoFe2O4/CNTs nanocomposite showed maximum value of saturation magnetization which was 37.47 emu g-1. The as prepared MIIFe2O4/CNTs nanocomposites have many potential application in magnetically guided targeted drug delivery, clinical diagnosis, electrochemical biosensing, magnetic data storage and magnetic resonance imaging.

  7. Measurement of dielectric and magnetic properties of soil

    SciTech Connect

    Patitz, W.E.; Brock, B.C.; Powell, E.G.

    1995-11-01

    The possibility of subsurface imaging using SAR technology has generated a considerable amount of interest in recent years. One requirement for the successful development of a subsurface imagin system is an understanding of how the soil affects the signal. In response to a need for an electromagnetic characterization of the soil properties, the Radar/Antenna department has developed a measurement system which determines the soils complex electric permittivity and magnetic permeability at UHF frequencies. The one way loss in dB is also calculated using the measured values. There are many reports of measurements of the electric properties of soil in the literature. However, most of these are primarily concerned with measuring only a real dielectric constant. Because some soils have ferromagnetic constituents it is desirable to measure both the electric and magnetic properties of the soil.

  8. On the some magnetic properties of the Earth's solid core

    NASA Astrophysics Data System (ADS)

    Golbraikh, E.

    2013-09-01

    The role of the solid part of Earth's core in the generation, stabilization and maintenance of the Earth's magnetic field and influence of this field on the properties of the solid core have not been sufficiently studied until now. It is well known that the core consists essentially of iron. In the last 10-15 years new methods were developed for the study of its properties at high pressure and temperature. As was shown in different experiments, the crystal structure of the iron is returned to the bcc state in the Earth's solid core. In this report we will discuss the possibility that the core can be in the vicinity of the Curie point. At the same time, it is shown that if the solid core temperature is somewhat higher than the Curie temperature, then the effective magnetic field generation connected with magnetic moment fluctuations near the transition point is possible. The estimate of the effective magnetic field is obtained in our work. Simultaneously, we have estimated the interaction of the solid part of the core with magnetic field generated in its fluid part.

  9. Magnetic antenna excitation of whistler modes. I. Basic properties

    SciTech Connect

    Urrutia, J. M.; Stenzel, R. L.

    2014-12-15

    Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

  10. Growth and Properties of MnxGa Magnetic Nanostructures

    NASA Astrophysics Data System (ADS)

    Jamer, Michelle; Assaf, Badih A.; Eich, Marius; Moodera, Jagadeesh S.; Heiman, Don

    2013-03-01

    Rare-Earth (RE) magnets are becoming more expensive and less available for current applications in technology. MnxGa (x =2-3) has previously shown coercivity of > 2.5 T, close to that of RE magnets.[2] In this project, the vapor-liquid-solid (VLS) method was used to grow nanoparticles of MnxGa (x =1-3) with MBE. The goal was to study the magnetic properties as a function of reduced dimensionality. The samples were prepared by depositing a 3-6 nm layer of Au on Si, GaAs, and glass. It was found that the miscibility of Ga and Au is high, but for Mn and Au it is much lower. Therefore, during the growth process Ga was deposited on the gold catalyst followed by Mn deposition. The samples were then annealed at temperatures 100-500 °C. Nanostructures, including regions of nanowires, were found using scanning electron microscopy on all samples. The magnetic properties of the nanostructured samples were studied with SQUID magnetometry and found to have a magnetization of 200 emu/cm3. Work supported by NSF-DMR-0907007 and NSF-DMR-0819762.

  11. Thermodynamic properties of magnetic strings on a square lattice

    NASA Astrophysics Data System (ADS)

    Mol, Lucas; Oliveira, Denis Da Mata; Bachmann, Michael

    2015-03-01

    In the last years, spin ice systems have increasingly attracted attention by the scientific community, mainly due to the appearance of collective excitations that behave as magnetic monopole like particles. In these systems, geometrical frustration induces the appearance of degenerated ground states characterized by a local energy minimization rule, the ice rule. Violations of this rule were shown to behave like magnetic monopoles connected by a string of dipoles that carries the magnetic flux from one monopole to the other. In order to obtain a deeper knowledge about the behavior of these excitations we study the thermodynamics of a kind of magnetic polymer formed by a chain of magnetic dipoles in a square lattice. This system is expected to capture the main properties of monopole-string excitations in the artificial square spin ice. It has been found recently that in this geometry the monopoles are confined, but the effective string tension is reduced by entropic effects. To obtain the thermodynamic properties of the strings we have exactly enumerated all possible string configurations of a given length and used standard statistical mechanics analysis to calculate thermodynamic quantities. We show that the low-temperature behavior is governed by strings that satisfy ice rules. Financial support from FAPEMIG and CNPq (Brazilian agencies) are gratefully acknowledged.

  12. Magnetic antenna excitation of whistler modes. I. Basic properties

    NASA Astrophysics Data System (ADS)

    Urrutia, J. M.; Stenzel, R. L.

    2014-12-01

    Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

  13. Magnetic properties of tektites and other related impact glasses

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Gattacceca, J.; Devouard, B.; Moustard, F.; Bezaeva, N. S.; Cournède, C.; Scaillet, B.

    2015-12-01

    We present a comprehensive overview of the magnetic properties of the four known tektite fields and related fully melted impact glasses (Aouelloul, Belize, Darwin, Libyan desert and Wabar glasses, irghizites, and atacamaites), namely magnetic susceptibility and hysteresis properties as well as properties dependent on magnetic grain-size. Tektites appear to be characterized by pure Fe2+ paramagnetism, with ferromagnetic traces below 1 ppm. The different tektite fields yield mostly non-overlapping narrow susceptibility ranges. Belize and Darwin glasses share similar characteristics. On the other hand the other studied glasses have wider susceptibility ranges, with median close to paramagnetism (Fe2+ and Fe3+) but with a high-susceptibility population bearing variable amounts of magnetite. This signs a fundamental difference between tektites (plus Belize and Darwin glasses) and other studied glasses in terms of oxygen fugacity and heterogeneity during formation, thus bringing new light to the formation processes of these materials. It also appears that selecting the most magnetic glass samples allows to find impactor-rich material, opening new perspectives to identify the type of impactor responsible for the glass generation.

  14. Statistical Properties of Magnetic Reconnection in MHD turbulence

    NASA Astrophysics Data System (ADS)

    Servidio, Sergio; Matthaeus, William; Cassak, Paul; Shay, Michael; Dmitruk, Pablo

    2009-11-01

    Magnetic reconnection is an integral part of MHD turbulence[1] in that the fragmentation of magnetic eddies into smaller structures necessarily involves change of magnetic topology. To better understand this relationship, recently the properties of thousands of magnetic reconnection events in moderate Reynolds number MHD turbulence have been studied [1] using 2D spectral method simulations of compressible and incompressible MHD. Reconnection between magnetic islands, different in size and energy, occurs locally and sporadically in time. The associated reconnection rates are distributed over a wide range of values and scale with the geometry of the diffusion region. Matching classical turbulence analysis with the Sweet-Parker theory, the main statistical features of these multi-scale reconnection events are identified. Magnetic reconnection in turbulence can be described through an asymmetric Sweet-Parker model, in which the parameters that control the reconnection rates are determined by turbulence itself. This new and general perspective on reconnection is relevant in space and astrophysical systems, where plasma is generally in a fully nonlinear regime. [1] W. Matthaeus and S. Lamkin, Phys. Fluids, 29, 2513 (1986). [2] S. Servidio et al, PRL, 102, 115003 (2009).

  15. A Study of the Magnetic and Thermal Properties of Ln

    SciTech Connect

    Harada, Daijitsu; Hinatsu, Yukio

    2001-05-01

    Crystal structures, and magnetic, electric, and thermal properties of fluorite related compounds Ln{sub 3}RuO{sub 7} (Ln=Sm, Eu) have been investigated. For Eu{sub 3}RuO{sub 7}, a magnetic transition due to Ru{sup 5+} ions is found at T{sub N}=22.5 K on the susceptibility-temperature curve. Specific heat measurements also exhibit a {lambda}-type anomaly at the same temperature. The Moessbauer spectrum measured at 10 K shows broadening of the line corresponding to magnetic splitting. For Sm{sub 3}RuO{sub 7}, two magnetic anomalies have been observed at 10.5 and 22.5 K from its magnetic susceptibility measurements. Below 22.5 K Ru{sup 5+} ions are antiferromagnetically coupled, and when the temperature is decreased through 10.5 K the ordering of Sm{sup 3+} ions occurs rapidly. Specific heat measurements show first-order transition peaks at T=280 and 190 K for Eu{sub 3}RuO{sub 7} and Sm{sub 3}RuO{sub 7}, respectively. T he results of magnetic susceptibility and electric resistivity measurements indicate that these transitions are structural phase transitions.

  16. Electronic and magnetic properties of small rhodium clusters

    SciTech Connect

    Soon, Yee Yeen; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework. The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh{sub 4} and Rh{sub 6} are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.

  17. Monte Carlo simulation of magnetic domain structure and magnetic properties near the morphotropic phase boundary.

    PubMed

    Wei, Songrui; Yang, Sen; Wang, Dong; Song, Xiaoping; Ke, Xiaoqin; Gao, Yipeng; Liao, Xiaoqi; Wang, Yunzhi

    2017-03-08

    The morphotropic phase boundary (MPB), which is the boundary separating a tetragonal phase from a rhombohedral phase by varying the composition or mechanical pressure in ferroelectrics, has been studied extensively for decades because it can lead to strong enhancement of piezoelectricity. Recently, a parallel ferromagnetic MPB was experimentally reported in the TbCo2-DyCo2 ferromagnetic system and this discovery proposes a new way to develop potential materials with giant magnetostriction. However, the role of magnetic domain switching and spin reorientation near the MPB region is still unclear. For the first time, we combine micromagnetic theory with Monte Carlo simulation to investigate the evolution of magnetic domain structures and the corresponding magnetization properties near the MPB region. It is demonstrated that the magnetic domain structure and the corresponding magnetization properties are determined by the interplay among anisotropy energy, magnetostatic energy and exchange energy. If the anisotropy energy barrier is large compared with the magnetostatic energy barrier and the exchange energy barrier, the MPB region is a T and R mixed structure and magnetic domain switching is the dominant mechanism. If the anisotropy energy barrier is small, the MPB region will also contain M phases and spin reorientation is the dominant mechanism. Our work could provide a guide for the design of advanced ferromagnetic materials with enhanced magnetostriction.

  18. Optical Writing of Magnetic Properties by Remanent Photostriction.

    PubMed

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

    2016-09-02

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

  19. Optical Writing of Magnetic Properties by Remanent Photostriction

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  20. Magnetic properties of metastable Fe Pd alloys by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Yabe, Hiromasa; O'Handley, Robert C.; Kuji, Toshiro

    2007-03-01

    Metastable Fe-Pd powder samples with various Pd content were synthesized by mechanical alloying. Their fundamental properties, i.e., structure, magnetization and coercive fore are discussed. The saturation magnetizations of the metastable Fe-Pd powders gradually decreases with increasing Pd content. The coercive forces observed in as-milled samples are all less than 40 Oe. However, some of the heat-treated samples, notably, Pd content around 55 at% with L1 0 structure, shows Hc up to 1589 Oe.

  1. Aging of magnetic properties in MgO films

    SciTech Connect

    Balcells, Ll.; Konstantinovic, Z.; Martinez, B.; Beltran, J. I.; Martinez-Boubeta, C.; Arbiol, J.

    2010-12-20

    In this work we report on the magnetic behavior of MgO thin films prepared by sputtering. A severe aging process of the ferromagnetic properties is detected in magnetic samples exposed to ambient atmosphere. However, ferromagnetism can be successively switched on again by annealing samples in vacuum. We suggest this behavior reflects the key role played by defects in stabilizing ferromagnetism in MgO films and is likely to be closely related to the hydrogen-driven instability of V-type centers in this material.

  2. Magnetic properties of Y0.9Gd0.1Fe2D4.2 compound under continuous magnetic field up to 310 kOe

    NASA Astrophysics Data System (ADS)

    Paul-Boncour, V.; Guillot, M.; Mazet, T.

    2012-04-01

    In this work are presented results on the structural, magnetic, and magnetocaloric properties of the Y0.9Gd0.1Fe2D4.2 compound in which TM0 is shifted from 84 K to 110 K because of Gd influence. Magnetization measurements have been performed with a magnetic field up to 310 kOe in the 4.2-300 K temperature range with special attention paid near TM0. The spontaneous magnetization at 4.2 K (3.2 μB/mol) is smaller than for YFe2D4.2 (3.7 μB/mol), showing the contribution of Gd moments. Above 110 K, metamagnetic field-induced transitions are observed: the transition field HTR increases linearly with T. These transitions exist up to 170 K. The influence of both cell volume change and Gd magnetic contribution are finally discussed in comparison with other deuterides.

  3. Magnetic and magnetodielectric properties of erbium iron garnet ceramic

    SciTech Connect

    Maignan, A.; Singh, K.; Simon, Ch.; Lebedev, O. I.; Martin, C.

    2013-01-21

    An Er{sub 3}Fe{sub 5}O{sub 12} ceramic has been sintered in oxygen atmosphere at 1400 Degree-Sign C for dielectric measurements. Its structural quality at room temperature has been checked by combining transmission electron microscopy and X-ray diffraction. It crystallizes in the cubic space group Ia3d with a = 12.3488(1). The dielectric permittivity ({epsilon} Prime ) and losses (tan {delta}) measurements as a function of temperature reveal the existence of two anomalies, a broad one between 110 K and 80 K, attributed to the Er{sup 3+} spin reorientation, and a second sharper feature at about 45 K associated to the appearance of irreversibility on the magnetic susceptibility curves. In contrast to the lack of magnetic field impact on {epsilon} Prime for the former anomaly, a complex magnetic field effect has been evidenced below 45 K. The isothermal {epsilon} Prime (H) curves show the existence of positive magnetodielectric effect, reaching a maximum of 0.14% at 3 T and 10 K. Its magnitude decreases as H is further increased. Interestingly, for the lowest H values, a linear regime in the {epsilon} Prime (H) curve is observed. From this experimental study, it is concluded that the {epsilon} Prime anomaly, starting above the compensation temperature T{sub c} (75 K) and driven by the internal magnetic field, is not sensitive to an applied external magnetic field. Thus, below 45 K, it is the magnetic structure which is responsible for the coupling between spin and charge in this iron garnet.

  4. Transport and magnetic properties of RTX and related compounds

    NASA Astrophysics Data System (ADS)

    Goruganti, Venkateshwarlu

    Physical properties of RTX compounds (R = Rare earth, T = Transition metal and X = main group element from B, C or N group) compounds have been studied by means of electrical resistivity, heat capacity, dc magnetization and NMR. Searching for new magnetic materials is always an interesting topic from both a technological and basic research prospective; it is even more interesting when unusual magnetic phases are observed. Ternary intermetallic plumbides are interesting because of their unconventional magnetic ordering and variety of multiple magnetic transitions. Crystalline electric fields (CEF) also strongly effect the magnetic properties of these intermetallics. To understand the phase transitions, CEF effects, and magnetic interactions, a systematic study of the RNiPb, R 2Ni2Pb, R5NiPb3 and RCuGe systems were conducted. Among the results for NdNiPb a single antiferromagnetic transition was found at 3.5K, while the superconductivity found in some ingots of this material was shown not to correspond to a bulk behavior for this phase. Nd2Ni 2Pb was shown to have a canted zero field magnetic structure with a low temperature metamagnetic transition 3 T. In NdCuGe, a 3K AF transition was found along with a corresponding magnon contribution to the specific heat and magnetic and thermodynamic behavior from which the detailed CEF configuration was obtained. In a series of measurements on recently-synthesized R 5NiPb3 (R=Ce, Nd, Gd), for Ce5NiPb 3 a transition at 48 K was found, which was confirmed to be ferromagnetic character from field dependent heat capacity and Curie-Weiss susceptibility. Nd5NiPb3 exhibits two transitions, an antiferromagnetic transition at 42 K and an apparently weak ferromagnetic canting transition at 8 K. For Gd5NiPb3, a ferro- or ferrimagnetic transition was found at 68 K. For the Ce and Nd materials metamagnetism was also observed at low temperatures. In addition, very large metallic type gamma terms were found in the specific heat, as well as a

  5. Influence of magnetic electrodes thicknesses on the transport properties of magnetic tunnel junctions with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Cuchet, Léa; Rodmacq, Bernard; Auffret, Stéphane; Sousa, Ricardo C.; Dieny, Bernard

    2014-08-01

    The influence of the bottom and top magnetic electrodes thicknesses on both perpendicular anisotropy and transport properties is studied in (Co/Pt)/Ta/CoFeB/MgO/FeCoB/Ta magnetic tunnel junctions. By carefully investigating the relative magnetic moment of the two electrodes as a function of their thicknesses, we identify and quantify the presence of magnetically dead layers, likely localized at the interfaces with Ta, that is, 0.33 nm for the bottom electrode and 0.60 nm for the top one. Critical thicknesses (spin-reorientation transitions) are determined as 1.60 and 1.65 nm for bottom and top electrodes, respectively. The tunnel magnetoresistance ratio reaches its maximum value, as soon as both effective (corrected from dead layer) electrode thicknesses exceed 0.6 nm.

  6. Magnetic properties of ultrathin tetragonal Heusler D022-Mn3Ge perpendicular-magnetized films

    NASA Astrophysics Data System (ADS)

    Sugihara, A.; Suzuki, K. Z.; Miyazaki, T.; Mizukami, S.

    2015-05-01

    We investigated the crystal structure and magnetic properties of Manganese-germanium (Mn3Ge) films having the tetragonal D022 structure, with varied thicknesses (5-130 nm) prepared on chromium (Cr)-buffered single crystal MgO(001) substrates. A crystal lattice elongation in the in-plane direction, induced by the lattice mismatch between the D022-Mn3Ge and the Cr buffer layer, increased with decreasing thickness of the D022-Mn3Ge layer. The films exhibited clear magnetic hysteresis loops with a squareness ratio close to unity, and a step-like magnetization reversal even at a 5-nm thickness under an external field perpendicular to the film's plane. The uniaxial magnetic anisotropy constant of the films showed a reduction to less than 10 Merg/cm3 in the small thickness range (≤20 nm), likely due to the crystal lattice elongation in the in-plane direction.

  7. Influence of magnetic electrodes thicknesses on the transport properties of magnetic tunnel junctions with perpendicular anisotropy

    SciTech Connect

    Cuchet, Léa; Rodmacq, Bernard; Auffret, Stéphane; Sousa, Ricardo C.; Dieny, Bernard

    2014-08-04

    The influence of the bottom and top magnetic electrodes thicknesses on both perpendicular anisotropy and transport properties is studied in (Co/Pt)/Ta/CoFeB/MgO/FeCoB/Ta magnetic tunnel junctions. By carefully investigating the relative magnetic moment of the two electrodes as a function of their thicknesses, we identify and quantify the presence of magnetically dead layers, likely localized at the interfaces with Ta, that is, 0.33 nm for the bottom electrode and 0.60 nm for the top one. Critical thicknesses (spin-reorientation transitions) are determined as 1.60 and 1.65 nm for bottom and top electrodes, respectively. The tunnel magnetoresistance ratio reaches its maximum value, as soon as both effective (corrected from dead layer) electrode thicknesses exceed 0.6 nm.

  8. Magnetic structure and Magnetic transport Properties of Graphene Nanoribbons With Sawtooth Zigzag Edges

    NASA Astrophysics Data System (ADS)

    Wang, D.; Zhang, Z.; Zhu, Z.; Liang, B.

    2014-12-01

    The magnetic structure and magnetic transport properties of hydrogen-passivated sawtooth zigzag-edge graphene nanoribbons (STGNRs) are investigated theoretically. It is found that all-sized ground-state STGNRs are ferromagnetic and always feature magnetic semiconductor properties, whose spin splitting energy gap Eg changes periodically with the width of STGNRs. More importantly, for the STGNR based device, the dual spin-filtering effect with the perfect (100%) spin polarization and high-performance dual spin diode effect with a rectification ratio about 1010 can be predicted. Particularly, a highly effective spin-valve device is likely to be realized, which displays a giant magnetoresistace (MR) approaching 1010%, which is three orders magnitude higher than the value predicted based on the zigzag graphene nanoribbons and six orders magnitude higher than previously reported experimental values for the MgO tunnel junction. Our findings suggest that STGNRs might hold a significant promise for developing spintronic devices.

  9. Magnetic Properties of Bermuda Rise Sediments Controlled by Glacial Cycles During the Late Pleistocene

    NASA Astrophysics Data System (ADS)

    Roud, S.

    2015-12-01

    Sediments from ODP site 1063 (Bermuda Rise, North Atlantic) contain a high-resolution record of geomagnetic field behavior during the Brunhes Chron. We present rock magnetic data of the upper 160 mcd (<900 ka) from hole 1063D that show magnetic properties vary in concert with glacial cycles. Magnetite appears to be the main magnetic carrier in the carbonate-dominated interglacial horizons, yet exhibits contrasting grain size distributions depending on the redox state of the horizons. Higher contributions of single domain magnetite exist above the present day sulfate reduction zone (ca. 44 mcd) with relatively higher multidomain magnetite components below that likely arise from the partial dissolution of SD magnetite in the deeper, anoxic horizons. Glacial horizons on the other hand, characterized by enhanced terrigenous deposition, show no evidence for diagenetic dissolution but do indicate the presence of authigenic greigite close to glacial maxima (acquisition of gyro-remanence, strong magnetostatic interactions and SD properties). Glacial horizons contain hematite (maxima in HIRM and S-Ratio consistent with a reddish hue) and exhibit higher ARM anisotropy and pronounced sedimentary fabrics. We infer that post depositional processes affected the magnetic grain size and mineralogy of Bermuda rise sediments deposited during the late Pleistocene. Hematite concentration is interpreted to reflect primary terrigenous input that is likely derived from the Canadian Maritime Provinces. A close correlation between HIRM and magnetic foliation suggests that changes in sediment composition (terrigenous vs. marine biogenic) were accompanied by changes in the depositional processes at the site.

  10. Magnetic and electrical properties of In doped cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Nongjai, Razia; Khan, Shakeel; Asokan, K.; Ahmed, Hilal; Khan, Imran

    2012-10-01

    Nanoparticles of CoFe2O4 and CoIn0.15Fe1.85O4 ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In3+ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric constant (ɛ') and dielectric loss (tan δ) are also studied as a function of frequency and temperature. The variation of dielectric properties ɛ', tan δ, and ac conductivity (σac) with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe2+ and Fe3+ as well as between Co2+ and Co3+ ions at B-sites. Magnetization and electrical property study showed its dominant dependence on the grain size.

  11. Magnetic properties of electrodeposited Ni‒P alloys with varying phosphorus content

    NASA Astrophysics Data System (ADS)

    Knyazev, A. V.; Fishgoit, L. A.; Chernavskii, P. A.; Safonov, V. A.; Filippova, S. E.

    2017-02-01

    The effect thermal treatment has on the magnetic properties (magnetization, saturation magnetization, and coercivity) of Ni‒P alloys prepared via electrodeposition is studied. The process of amorphous Ni‒P alloys devitrification is investigated by differential scanning calorimetry. The effects of chemical composition and thermal treatment on magnetic properties of the alloys are revealed.

  12. Magnetic nanoparticles supported ionic liquids improve firefly luciferase properties.

    PubMed

    Noori, Ali Reza; Hosseinkhani, Saman; Ghiasi, Parisa; Akbari, Jafar; Heydari, Akbar

    2014-03-01

    Ionic liquids as neoteric solvents, microwave irradiation, and alternative energy source are becoming as a solvent for many enzymatic reactions. We recently showed that the incubation of firefly luciferase from Photinus pyralis with various ionic liquids increased the activity and stability of luciferase. Magnetic nanoparticles supported ionic liquids have been obtained by covalent bonding of ionic liquids-silane on magnetic silica nanoparticles. In the present study, the effects of [γ-Fe2O3@SiO2][BMImCl] and [γ-Fe2O3@SiO2][BMImI] were investigated on the structural properties and function of luciferase using circular dichroism, fluorescence spectroscopy, and bioluminescence assay. Enzyme activity and structural stability increased in the presence of magnetic nanoparticles supported ionic liquids. Furthermore, the effect of ingredients which were used was not considerable on K(m) value of luciferase for adenosine-5'-triphosphate and also K(m) value for luciferin.

  13. Discontinuous properties of current-induced magnetic domain wall depinning

    PubMed Central

    Hu, X. F.; Wu, J.; Niu, D. X.; Chen, L.; Morton, S. A.; Scholl, A.; Huang, Z. C.; Zhai, Y.; Zhang, W.; Will, I.; Xu, Y. B.; Zhang, R.; van der Laan, G.

    2013-01-01

    The current-induced motion of magnetic domain walls (DWs) confined to nanostructures is of great interest for fundamental studies as well as for technological applications in spintronic devices. Here, we present magnetic images showing the depinning properties of pulse-current-driven domain walls in well-shaped Permalloy nanowires obtained using photoemission electron microscopy combined with x-ray magnetic circular dichroism. In the vicinity of the threshold current density (Jth = 4.2 × 1011 A.m−2) for the DW motion, discontinuous DW depinning and motion have been observed as a sequence of “Barkhausen jumps”. A one-dimensional analytical model with a piecewise parabolic pinning potential has been introduced to reproduce the DW hopping between two nearest neighbour sites, which reveals the dynamical nature of the current-driven DW motion in the depinning regime. PMID:24170087

  14. Magnetic Properties of Nanocrystalline Nickel-Cobalt Ferrites

    NASA Astrophysics Data System (ADS)

    Tiwari, D. K.; Villaseñor-Cendejas, L. M.; Thakur, A. K.

    2013-09-01

    In this study, the nanocrystalline nickel-cobalt ferrites were prepared via the citrate route method at . The samples were calcined at for 3 h. The crystalline structure and the single-phase formations were confirmed by X-ray diffraction (XRD) measurements. Prepared materials showed the cubic spinel structure with m3m symmetry and Fd3m space group. The analyses of XRD patterns were carried out using POWD software. It gave an estimation of lattice constant “” of 8.3584 Å, which was in good agreement with the results reported in JCPDS file no. 742081. The crystal size of the prepared materials calculated by Scherer’s formula was 27.6 nm and the electrical conductivity was around . The permeability component variations with frequency were realized. The magnetic properties of the prepared materials were analyzed by a vibrating sample magnetometer (VSM). It showed a saturation magnetization of and the behavior of a hard magnet.

  15. Magnetic properties of Al/57Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Jani, Snehal; Lakshmi, N.; Jain, Vishal; Reddy, V. R.; Gupta, Ajay; Venugopalan, K.

    2013-06-01

    Conversion Electron Mössbauer Spectroscopy (CEMS) and DC magnetization are used to compare magnetic properties of as-deposited multilayer (MLS) and Fe2CrAl thin film made from Al/57Fe/Cr MLS deposited by ion beam sputtering and then annealed in UHV. Interdiffusion of elements on annealing sample-1 at 500°C leads to formation of a single, disordered film of Fe2CrAl as evidenced by hyperfine field values obtained by CEMS in the film which compares well with that in bulk Fe2CrAl. CEMS also shows contributions from Fe, Fe/Cr and Fe/Al interfaces in the MLS. Saturation magnetization of as-deposited sample-1 is much less than pure Fe due to reduced Fe thickness because of interface formation and also reduction in Fe-Fe interaction due to intervening Al and Cr layers.

  16. Magnetic properties of X-ray bright points. [in sun

    NASA Technical Reports Server (NTRS)

    Golub, L.; Krieger, A. S.; Harvey, J. W.; Vaiana, G. S.

    1977-01-01

    Using high-resolution Kitt Peak National Observatory magnetograms and sequences of simultaneous S-054 soft X-ray solar images, the properties of X-ray bright points (XBP) and ephemeral active regions (ER) are compared. All XBP appear on the magnetograms as bipolar features, except for very recently emerged or old and decayed XBP. The separation of the magnetic bipoles is found to increase with the age of the XBP, with an average emergence growth rate of 2.2 plus or minus 0.4 km per sec. The total magnetic flux in a typical XBP living about 8 hr is found to be about two times ten to the nineteenth power Mx. A proportionality is found between XBP lifetime and total magnetic flux, equivalent to about ten to the twentieth power Mx per day of lifetime.

  17. Structure and magnetic properties of nanostructured Ni-ferrite

    NASA Astrophysics Data System (ADS)

    Albuquerque, A. S.; Ardisson, J. D.; Macedo, W. A. A.; López, J. L.; Paniago, R.; Persiano, A. I. C.

    2001-05-01

    The structural and magnetic properties of NiFe 2O 4 ultrafine powders synthesized by coprecipitation, a nonconventional method of preparation, were investigated. The samples were obtained by annealing at relatively low temperatures (300-600°C) and characterized by X-ray diffraction, Mössbauer spectroscopy, and vibrating sample magnetometry. The average particle diameter ranges from 4 to 15 nm, as determined by X-ray diffraction. All nanometric powder samples presented strong superparamagnetic relaxation at room temperature and reduced magnetic hyperfine fields at -193°C. Magnetometry measurements indicated different magnetic behavior related with crystallinity of samples, coercivity as high as 168 Oe at 27°C, value that is nearly two times higher than coercivity of bulk Ni-ferrite.

  18. Astroid curves of high-moment antiferromagnetic nanoparticles with tunable magnetic properties

    NASA Astrophysics Data System (ADS)

    Forrester, D. M.; Kovacs, E.; Kürten, K. E.; Kusmartsev, F. V.

    2009-04-01

    We have determined astroids for high-moment antiferromagnetic nanoparticles (AN), which have been recently discovered and used in numerous biomedical applications. The astroid curves for such a system, which is a stack of two isolated disk-shaped ferromagnetic nanoparticles interacting antiferromagnetically, show the regions in the magnetic field plane where different numbers of minima associated with stable or metastable states may exist. We describe the properties of these ANs and estimate their other characteristic parameters such as magnetic saturation field and exchange antiferrtomagnetic coupling. We argue that the finding of these astroids and the properties of ANs is crucial for the use of ANs in numerous applications and for modeling stable information storage devices.

  19. Magnetic microstructure and magnetic properties of spark plasma sintered NdFeB magnets

    NASA Astrophysics Data System (ADS)

    Huang, Y. L.; Wang, Y.; Hou, Y. H.; Wang, Y. L.; Wu, Y.; Ma, S. C.; Liu, Z. W.; Zeng, D. C.; Tian, Y.; Xia, W. X.; Zhong, Z. C.

    2016-02-01

    Nanocrystalline NdFeB magnets were prepared by spark plasma sintering (SPS) technique using melt-spun ribbons as starting materials. A distinct two-zone structure with coarse grain zone and fine grain zone was formed in the SPSed magnets. Multi-domain particle in coarse grain zone and exchange interaction domain for fine grain zone were observed. Intergranular non-magnetic phase was favorable to improve the coercivity due to the enhancement of domain wall pinning effects and increased exchange-decouple. The remanent polarization of 0.83 T, coercivity of 1516 kA/m, and maximum energy product of 118 kJ/m3 are obtained for an isotropic magnet.

  20. Magnetic and electronic properties of porphyrin-based molecular nanowires

    SciTech Connect

    Zheng, Jia-Jia; Li, Qiao-Zhi; Dang, Jing-Shuang; Zhao, Xiang; Wang, Wei-Wei

    2016-01-15

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  1. Non-destructive evaluation of mechanical properties of magnetic materials

    SciTech Connect

    Kankolenski, K.P.; Hua, S.Z.; Yang, D.X.; Hicho, G.E.; Swartzendruber, L.J.; Zang, Z.; Chopra, H.D.

    2000-07-01

    A magnetic-based non-destructive evaluation (NDE) method, which employs Barkhausen effect and measurement of the hysteresis loops, is used to correlate the magnetic and mechanical properties of ultra low carbon (ULC) steel. In particular, the NDE method was used to detect small deviations from linearity that occur in the stress-strain curve well below the 0.2% offset strain, and which generally defines the yield point in materials. Results show that three parameters: jumpsum and jumpsum rate (derived from the Barkhausen spectrum), and the relative permeability (derived from the B-H loops) varies sensitively with small permanent strains, and can be related to the plastic deformation in ULC steels. Investigation of micromagnetic structure revealed that plastic deformation leaves a residual stress state in the samples; the associated magneto-elastic energy makes the favorable easy axis of magnetization in a given grain to be the one that lies closest to the tensile axis. The consequence of this realignment of domains is that wall motion becomes intergranular in nature (as opposed to intragranular in unstrained samples). As a result, the more complex grain boundaries instead of dislocations, become the dominant pinning sites for domain walls. These observations provide a microscopic interpretation of the observed changes in the measured magnetic properties.

  2. Electronic structure and magnetic properties of zigzag blue phosphorene nanoribbons

    SciTech Connect

    Hu, Tao; Hong, Jisang

    2015-08-07

    We investigated the electronic structure and magnetism of zigzag blue phosphorene nanoribbons (ZBPNRs) using first principles density functional theory calculations by changing the widths of ZBPNRs from 1.5 to 5 nm. In addition, the effect of H and O passivation was explored as well. The ZBPNRs displayed intra-edge antiferromagnetic ground state with a semiconducting band gap of ∼0.35 eV; and this was insensitive to the edge structure relaxation effect. However, the edge magnetism of ZBPNRs disappeared with H-passivation. Moreover, the band gap of H-passivated ZBPNRs was greatly enhanced because the calculated band gap was ∼1.77 eV, and this was almost the same as that of two-dimensional blue phosphorene layer. For O-passivated ZBPNRs, we also found an intra-edge antiferromagnetic state. Besides, both unpassivated and O-passivated ZBPNRs preserved almost the same band gap. We predict that the electronic band structure and magnetic properties can be controlled by means of passivation. Moreover, the edge magnetism can be also modulated by the strain. Nonetheless, the intrinsic physical properties are size independent. This feature can be an advantage for device applications because it may not be necessary to precisely control the width of the nanoribbon.

  3. Magnetic and electronic properties of porphyrin-based molecular nanowires

    NASA Astrophysics Data System (ADS)

    Zheng, Jia-Jia; Li, Qiao-Zhi; Dang, Jing-Shuang; Wang, Wei-Wei; Zhao, Xiang

    2016-01-01

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  4. Size-dependent magnetic properties of branchlike nickel oxide nanocrystals

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Li, Dongsheng; Yang, Deren

    2017-01-01

    Branchlike nickel oxide nanocrystals with narrow size distribution are obtained by a solution growth method. The size-dependent of magnetic properties of the nickel oxides were investigated. The results of magnetic characterization indicate that the NiO nanocrystals with size below 12.8 nm show very weak ferromagnetic state at room temperature due to the uncompensated spins. Both of the average blocking temperature (Tb) and the irreversible temperature (Tirr) increase with the increase of nanoparticle sizes, while both the remnant magnetization and the coercivity at 300 K increase with the decrease of the particle sizes. Moreover, the disappearance of two-magnon (2M) band and redshift of one-phonon longitudinal (1LO) and two-phonon LO in vibrational properties due to size reduction are observed. Compared to the one with the spherical morphological, it is also found that nano-structured nickel oxides with the branchlike morphology have larger remnant magnetization and the coercivity at 5 K due to their larger surface-to-volume ratio and greater degree of broken symmetry at the surface or the higher proportion of broken bonds.

  5. Structural, dielectric and magnetic properties of Ni substituted zinc ferrite

    NASA Astrophysics Data System (ADS)

    Kumbhar, S. S.; Mahadik, M. A.; Mohite, V. S.; Rajpure, K. Y.; Kim, J. H.; Moholkar, A. V.; Bhosale, C. H.

    2014-08-01

    NixZn1-xFe2O4 ferrite has been synthesized by the ceramic method using Ni CO3, ZnO, Fe2O3 precursors. The influence of Ni content on the structural, morphological, electrical and magnetic properties of NixZn1-xFe2O4 ferrites is studied. The X-ray diffraction (XRD) analysis reveals that the samples are polycrystalline with spinel cubic structure. The SEM images of NixZn1-xFe2O4 ferrite show that the grain size decreases with an increase in the Ni content. The tetrahedral and octahedral vibrations in the samples are studied by IR spectra. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. Conduction mechanism due to polarons has been analyzed by measuring the AC conductivity. Impedance spectroscopy is used to study the electrical behavior. Magnetic properties of NixZn1-xFe2O4 are studied by using hysteresis loop measurement. The maximum value of saturation magnetization of 132.8 emu/g obtained for the composition, x=0.8, is attributed to magnetic moment of Fe3+ ions.

  6. Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

    USGS Publications Warehouse

    Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

    2011-01-01

    The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

  7. Magnetic and transport properties of PrRhSi3.

    PubMed

    Anand, V K; Adroja, D T; Hillier, A D

    2013-05-15

    We have investigated the magnetic and transport properties of a noncentrosymmetric compound PrRhSi3 by dc magnetic susceptibility χ(T), isothermal magnetization M(H), thermoremanent magnetization M(t), specific heat Cp(T), electrical resistivity ρ(T,H) and muon spin relaxation (μSR) measurements. At low fields χ(T) shows two anomalies near 15 and 7 K with an irreversibility between ZFC and FC data below 15 K. In contrast, no anomaly is observed in Cp(T) or ρ(T) data. M(H) data at 2 K exhibit very sharp increase below 0.5 T and a weak hysteresis. M(t) exhibits very slow relaxation, typical for a spin-glass system. Even though the absence of any anomaly in Cp(T) is consistent with the spin-glass type behavior, there is no obvious origin of spin-glass behavior in this structurally well ordered compound. The crystal electric field (CEF) analysis of Cp(T) data indicates a CEF-split singlet ground state lying below a doublet at 81(1) K and a quasi-triplet at 152(2) K. The ρ(T) data indicate a metallic behavior, and ρ(H) exhibits a very high positive magnetoresistance, as high as ~300% in 9 T at 2 K. No long range magnetic order or spin-glass behavior was detected in a μSR experiment down to 1.2 K.

  8. Possible Properties of Kinetic Flux Ropes Generated by Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Ng, C. S.

    2015-12-01

    We present latest results of numerical studies of a recently obtained analytic solution that can describe small-scale kinetic flux ropes. Such exact nonlinear solution of the Vlasov-Poisson-Ampere system of equations can be regarded as two-dimensional Bernstein-Greene-Kruskal (BGK) mode, generalizing from a solution in a magnetized plasma with finite magnetic field strength [Ng, Bhattacharjee, and Skiff, Phys. Plasmas 13, 055903 (2006)], with the additional effect of field-aligned current. Such solution might explain magnetic flux ropes observed to form within the diffusion region in 3D kinetic simulations of magnetic reconnection, and the 2D version of them (plasmoids, secondary islands). We will present properties of solutions based on a range of typical plasma parameters within regions of the magnetosphere where magnetic reconnection could happen. These solutions could potentially be used to compare with future Magnetospheric Multiscale Mission (MMS) observation. This work is supported by a National Science Foundation grant PHY-1004357 and the Alaska NASA EPSCoR Program (NNX13AB28A).

  9. Cryogenic properties of dispersion strengthened copper for high magnetic fields

    SciTech Connect

    Toplosky, V. J.; Han, K.; Walsh, R. P.; Swenson, C. A.

    2014-01-27

    Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

  10. Nonaqueous magnetic nanoparticle suspensions with controlled particle size and nuclear magnetic resonance properties.

    PubMed

    Meledandri, Carla J; Stolarczyk, Jacek K; Ghosh, Swapankumar; Brougham, Dermot F

    2008-12-16

    We report the preparation of monodisperse maghemite (gamma-Fe2O3) nanoparticle suspensions in heptane, by thermal decomposition of iron(III) acetylacetonate in the presence of oleic acid and oleylamine surfactants. By varying the surfactant/Fe precursor mole ratio during synthesis, control was exerted both over the nanocrystal core size, in the range from 3 to 6 nm, and over the magnetic properties of the resulting nanoparticle dispersions. We report field-cycling 1H NMR relaxation analysis of the superparamagnetic relaxation rate enhancement of nonaqueous suspensions for the first time. This approach permits measurement of the relaxivity and provides information on the saturation magnetization and magnetic anisotropy energy of the suspended particles. The saturation magnetization was found to be in the expected range for maghemite particles of this size. The anisotropy energy was found to increase significantly with decreasing particle size, which we attribute to increased shape anisotropy. This study can be used as a guide for the synthesis of maghemite nanoparticles with selected magnetic properties for a given application.

  11. Theoretical study of magnetic properties and x-ray magnetic circular dichroism of the ordered Fe{sub 0.5}Pd{sub 0.5} alloy

    SciTech Connect

    Galanakis, I.; Ostanin, S.; Alouani, M.; Dreysse, H.; Wills, J. M.

    2000-01-01

    A detailed theoretical study of magnetic and structural properties of Fe{sub 0.5}Pd{sub 0.5} ordered face-centered tetragonal (fct) alloy, using both the local spin density approximation (LSDA) and the generalized gradient approximation (GGA), is presented. The total energy surface as a function of the lattice parameters a and c shows a long valley where stable structures may exist. Our calculation using the GGA predicts a magnetic phase transition from perpendicular to parallel magnetization as a function of the lattice parameter, whereas LSDA favors always the [001] magnetization axis for all values of the lattice parameters. The spin and orbital magnetic moments and x-ray magnetic circular dichroism spectra are calculated for the easy [001] and the hard [100] magnetization axis and for three sets of experimental lattice parameters, and are compared to the available experimental results on these films. A supercell calculation for a 4 monolayer Fe{sub 0.5}Pd{sub 0.5} thin film produced similar results. While the spin magnetic moments are in fair agreement with experiment, the orbital magnetic moments are considerably underestimated. To improve the agreement with experiment we included an atomic orbital polarization term; however, the computed orbital moments scarcely changed. (c) 2000 The American Physical Society.

  12. Fermi surface, magnetic, and superconducting properties in actinide compounds

    NASA Astrophysics Data System (ADS)

    Ōnuki, Yoshichika; Settai, Rikio; Haga, Yoshinori; Machida, Yo; Izawa, Koichi; Honda, Fuminori; Aoki, Dai

    2014-08-01

    The de Haas-van Alphen effect, which is a powerful method to explore Fermi surface properties, has been observed in cerium, uranium, and nowadays even in neptunium and plutonium compounds. Here, we present the results of several studies concerning the Fermi surface properties of the heavy fermion superconductors UPt3 and NpPd5Al2, and of the ferromagnetic pressure-induced superconductor UGe2, together with those of some related compounds for which fascinating anisotropic superconductivity, magnetism, and heavy fermion behavior has been observed. xml:lang="fr"

  13. Complex magnetic properties in multilayer rare earth oxypnictides

    NASA Astrophysics Data System (ADS)

    Wang, Jiakui; Marcinkova, Andrea; Chen, Chih-Wei; Morosan, Emilia; Morosan Group Team

    2014-03-01

    Intensive research interest on layered transition metal pnictide materials was stimulated by the discovery of high temperature superconductivity in Fe-pnictides a few years ago. To study the relationship between superconductivity, crystal structure and magnetism, and to search for novel superconductors of better application potential, more transition metal pnictides are worth investigating. In this talk, I will discuss physical properties of members of a particular class of layered oxypnictides, with four transition metal pnictogen layers per unit cell. While varying the rare earth ion, we find that one compound is a low temperature superconductor (Tc 1.7 K), and others show diverse magnetic properties, including ferromagnetic or antiferromagnetic order, or spin glass behavior. I will show our observation from measurements of DC and AC magnetization, specific heat and resistivity. The understanding of the physical properties of these isostructual compounds may serve as a guide in the search for superconductivity in these systems. This work is supported by MURI-AFOSR and Rice University.

  14. Magnetic properties of Fe-Cu-Nb-Si-B nanocrystalline magnetic alloys

    SciTech Connect

    Garcia del Muro, M.; Batlle, X.; Zquiak, R.; Tejada, J.; Polak, C.; Groessinger, R.

    1994-03-01

    Several ribbons of composition Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 16.5}B{sub 6} and Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9} were prepared by annealing the as-quenched samples between 525 C and 700 C, which induced nucleation of nanocrystallites of Fe bcc-type composition. Mean grain sizes were obtained from X-ray diffraction. Static magnetic properties were measured with both a Magnet Physik Hysteresis-Graph (up to 200 Oe) and a SHE S.Q.U.I.D. Magnetometer (up to 50 kOe). Soft magnetic parameters (coercive field and initial permeability) were very sensitive to grain size. The ZFC magnetization at low field showed a broad peak at a temperature T{sub M}, thus signaling a certain distribution of nanocrystalline sizes, and T{sub M} strongly decreased when the mean grain size decreased. Isothermal magnetization curves at low temperature showed the expected asymptotic behavior of a random magnet material at low and high fields.

  15. Synthesis, photoluminescence and magnetic properties of barium vanadate nanoflowers

    SciTech Connect

    Xu, Jing; Hu, Chenguo; Xi, Yi; Peng, Chen; Wan, Buyong; He, Xiaoshan

    2011-06-15

    Graphical abstract: The flower-shaped barium vanadate was obtained for the first time. The photoluminescence and magnetic properties of the barium vanadate nanoflowers were investigated at room temperature. Research highlights: {yields} In the paper, the flower-shaped barium vanadate were obtained for the first time. The CHM method used here is new and simple for preparation of barium vanadate. {yields} The photoluminescence and magnetic properties of the barium vanadate nanoflowers were investigated at room temperature. The strong bluish-green emission was observed. {yields} The ferromagnetic behavior of the barium vanadate nanoflowers was found with saturation magnetization of about 83.50 x 10{sup -3} emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 x 10{sup -3} emu/g. {yields} The mechanisms of PL and magnetic property of barium vanadate nanoflowers have been discussed. -- Abstract: The flower-shaped barium vanadate has been obtained by the composite hydroxide mediated (CHM) method from V{sub 2}O{sub 5} and BaCl{sub 2} at 200 {sup o}C for 13 h. XRD and XPS spectrum of the as-synthesized sample indicate it is hexagonal Ba{sub 3}V{sub 2}O{sub 8} with small amount of Ba{sub 3}VO{sub 4.8} coexistence. Scan electron microscope and transmission electron microscope display that the flower-shaped crystals are composed of nanosheets with thickness of {approx}20 nm. The UV-visible spectrum shows that the barium vanadate sample has two optical gaps (3.85 eV and 3.12 eV). Photoluminescence spectrum of the barium vanadate flowers exhibits a visible light emission centered at 492 and 525 nm which might be attributed to VO{sub 4} tetrahedron with T{sub d} symmetry in Ba{sub 3}V{sub 2}O{sub 8}. The ferromagnetic behavior of the barium vanadate nanoflowers has been found with saturation magnetization of about 83.50 x 10{sup -3} emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 x 10{sup -3} emu/g, which is mainly due to the presence of a non

  16. Metal nanoparticle fluids with magnetically induced electrical switching properties

    NASA Astrophysics Data System (ADS)

    Kim, Younghoon; Cho, Jinhan

    2013-05-01

    We report the successful preparation of solvent-free metal nanoparticle (NP) fluids with multiple-functionalities, such as rheological properties, magnetism, ionic conductivity, and electrical properties, allowing for facile synthesis and mass production. The gold nanoparticles (AuNPs) used in this study were synthesized using tetraoctylammonium bromide (TOABr) in toluene and then directly phase-transferred to solvent-free low-molecular-weight (Mw) imidazolium-type ionic liquid media containing thiol groups (i.e., IL-SH). Magnetic metal fluids (i.e., MIL-SH-AuNPs) were prepared by the addition of FeCl3 powder to metal fluids (i.e., IL-SH-AuNPs). These fluids showed relatively high ionic and electrical conductivities compared with those of conventional metal NP fluids based on organic ILs with high Mw. Furthermore, it was demonstrated that these fluids could be used as electric switches operated using an external magnetic field in organic media.We report the successful preparation of solvent-free metal nanoparticle (NP) fluids with multiple-functionalities, such as rheological properties, magnetism, ionic conductivity, and electrical properties, allowing for facile synthesis and mass production. The gold nanoparticles (AuNPs) used in this study were synthesized using tetraoctylammonium bromide (TOABr) in toluene and then directly phase-transferred to solvent-free low-molecular-weight (Mw) imidazolium-type ionic liquid media containing thiol groups (i.e., IL-SH). Magnetic metal fluids (i.e., MIL-SH-AuNPs) were prepared by the addition of FeCl3 powder to metal fluids (i.e., IL-SH-AuNPs). These fluids showed relatively high ionic and electrical conductivities compared with those of conventional metal NP fluids based on organic ILs with high Mw. Furthermore, it was demonstrated that these fluids could be used as electric switches operated using an external magnetic field in organic media. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00653k

  17. Magnetic properties of Dirac fermions in a buckled honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Tabert, C. J.; Carbotte, J. P.; Nicol, E. J.

    2015-01-01

    We calculate the magnetic response of a buckled honeycomb lattice with intrinsic spin-orbit coupling (such as silicene) which supports valley-spin polarized energy bands when subjected to a perpendicular electric field Ez. By changing the magnitude of the external electric field, the size of the two band gaps involved can be tuned, and a transition from a topological insulator (TI) to a trivial band insulator (BI) is induced as one of the gaps becomes zero, and the system enters a valley-spin polarized metallic state (VSPM). In an external magnetic field (B ), a distinct signature of the transition is seen in the derivative of the magnetization with respect to chemical potential μ , which gives the quantization of the Hall plateaus through the Streda relation. When plotted as a function of the external electric field, the magnetization has an abrupt change in slope at its minimum, which signals the VSPM state. The magnetic susceptibility χ shows jumps as a function of μ when a band gap is crossed, which provides a measure of the gaps' variation as a function of external electric field. Alternatively, at fixed μ , the susceptibility displays an increasingly large diamagnetic response as the electric field approaches the critical value of the VSPM phase. In the VSPM state, magnetic oscillations exist for any value of chemical potential while for the TI and BI states, μ must be larger than the minimum gap in the system. When μ is larger than both gaps, there are two fundamental cyclotron frequencies (which can also be tuned by Ez) involved in the de-Haas van-Alphen oscillations that are close in magnitude. This causes a prominent beating pattern to emerge.

  18. Nanofabrication and ion milling introduced effects on magnetic properties in magnetic recording

    NASA Astrophysics Data System (ADS)

    Sun, Zhenzhong

    Perpendicular magnetic nanostructures have played an important role in magnetic recording technologies. In this dissertation, a systematic study on the CoPt magnetic nanostructures from fabrication, characterization to computer simulation has been performed. During the fabrication process, ion irradiation/bombardment in ion mill can cause physical damage to the magnetic nanostructures and degrade their magnetic properties. To study the effect of ion damage on CoPt nanostructures, different degrees of ion damage are introduced into CoPt nanopillars by varying the accelerating voltage in ion mill. The results demonstrate that the ion damage can reduce the coercivity by softening circumferential edge, and therefore changes the switching mechanism from coherent rotation to nucleation followed by rapid domain wall propagation. The SFD of CoPt nanostructures is independent of ion damage and is mainly determined by the intrinsic anisotropy distribution of the film rather than the nanostructure size distribution. Anisotropy-graded bit-patterned media are fabricated and studied based on high anisotropy L10-FePt material system. L10-FePt thin films with linearly and quadratically distributed anisotropy are achieved by varying substrate temperature during film growth. After patterning, the anisotropy-graded L10-FePt nanopillars display a reduced switching field and maintain a good thermal stability compared to the non-graded one. Experimental investigation and comparison further prove the concept of "anisotropy-graded" bit-patterned media and their potential application in the future magnetic recording. During magnetic write head fabrication, ion-beam damage may degrade the performance of the magnetic write pole. A surface sensitive MOKE is used to characterize the magnetic properties of these etched FeCo films. MOKE measurement shows a hard axis hysteresis loop with a high Mr in the high power etched film due to the ion beam introduced defects. The high power etched film

  19. Effect of hydriding degree on the microstructure and magnetic properties of sintered NdFeB magnets

    NASA Astrophysics Data System (ADS)

    Guo, Shuai; Liu, Youhao; Chen, Bicheng; Yan, Changjiang; Chen, Renjie; Lee, Don; Yan, Aru

    2012-04-01

    The effects of hydriding degree on the microstructure and magnetic properties of sintered NdFeB magnets have been studied. The degree of crushing depends on the absorption content of hydrogen and affects the magnetic properties of final magnet. Insertion of hydrogen atoms leads to a significant increase of the unit cell volume. And the crush mechanism depends on the internal stress resulting from differences in the expansion rates of the two phases. The remanence of final magnets increases monotonously while the coercivity decreases sharply with the increasing of hydriding degree, attributed to the strip fracture features and the morphology of particles.

  20. Experimental deformation of synthetic magnetite-bearing calcite sandstones - Effects on remanence, bulk magnetic properties, and magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Jackson, Mike; Borradaile, Graham; Hudleston, Peter; Banerjee, Subir

    1993-01-01

    The simultaneous effects of deformation on the magnetic remanence, bulk magnetic properties, and magnetic anisotropy of magnetite-bearing calcite sandstones were investigated in a set of synthetic magnetite-bearing samples prepared as described by Borradaile and Alford (1987). Experimental deformations of synthetic sandstone analogs containing 40-micron magnetite were found to produce significant changes in the orientation of anhysteretic remanence, in bulk magnetic properties, and in magnetic anisotropy. These changes proceeded slowly for shortening strains below about 10 percent, but much more rapidly at higher strains.

  1. Dielectric and magnetic properties of some gadolinium silica nanoceramics

    SciTech Connect

    Coroiu, I. Pascuta, P. Bosca, M. Culea, E.

    2013-11-13

    Some nanostructure gadolinium silica glass-ceramics were obtained undergoing a sol gel method and a heat-treatment at 1000°C about two hours. The magnetic and dielectric properties of these samples were studied. The magnetic properties were evidenced performing susceptibility measurements in the 80-300K temperature range. A Curie-Weiss behavior has acquired. The values estimated for paramagnetic Curie temperature being small and positive suggest the presence of weak ferromagnetic interactions between Gd{sup 3+} ions. The dielectric properties were evaluated from dielectric permittivity (ε{sub r}) and dielectric loss (tanδ) measurements at the frequency 1 kHz, 10 kHz and 100 kHz, in the 25-225°C temperature range and dielectric dispersion at room temperature for 79.5 kHz - 1GHz frequency area. The dielectric properties suggest that the main polarization mechanism corresponds to interfacial polarization, characteristic for polycrystalline-structured dielectrics. The polycrystalline structure of the samples is due to the polymorphous transformations of the nanostructure silica crystallites in the presence of gadolinium oxide. They were highlighted by SEM micrographs.

  2. Structural and magnetic properties of L10 -FePt nanoparticles aligned by external magnetic field

    NASA Astrophysics Data System (ADS)

    Tamada, Yoshinori; Yamamoto, Shinpei; Nasu, Saburo; Ono, Teruo

    2008-12-01

    We investigated structural and magnetic properties of the easy-axis aligned L10 -FePt nanoparticles by the combined use of x-ray diffraction (XRD), magnetization, and F57e Mössbauer measurements. The L10 -FePt nanoparticles were fixed in a polystyrene matrix by performing free radical polymerization of styrene under an aligning external magnetic field. Mössbauer spectrum of the L10 -FePt nanoparticles/polystyrene composite showed tremendous decrease in the second and fifth absorption lines under the condition that the incident γ ray was parallel to the aligning field. This result indicates that the easy axes of the L10 -FePt nanoparticles in the composite have a strong preferred orientation with a finite distribution. We estimated the distribution of easy-axis orientation by using the Mössbauer hyperfine parameters, which is in good agreement with that determined by the XRD rocking curve.

  3. Body-centered-cubic Ni and its magnetic properties.

    PubMed

    Tian, C S; Qian, D; Wu, D; He, R H; Wu, Y Z; Tang, W X; Yin, L F; Shi, Y S; Dong, G S; Jin, X F; Jiang, X M; Liu, F Q; Qian, H J; Sun, K; Wang, L M; Rossi, G; Qiu, Z Q; Shi, J

    2005-04-08

    The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.

  4. Observed Spatial Properties of the Solar Eigenfunctions and the Implications for the Existence of Resolved Multiplets

    NASA Technical Reports Server (NTRS)

    Caudell, T. P.; Hill, H. A.; Bos, R. J.

    1984-01-01

    Solar oscillations are manifested in the solar atmosphere as spatial and temporal perturbations in the local thermodynamical and mechanical properties. When measuring the solar radius/diameter, these perturbations enter the observation through changes in the radiative source function and opacity at the extreme limb. When compared to the disk center, the observable portion of these perturbations is changed in spatial character by projection effects and oblique optical depth geometry. The time varying solar radius signal at SCLERA (Santa Catalina Laboratory for Experimental Relativity) is produced by an edge definition sensitive to the resultant changes in the spatial shape of the limb intensity profile. An attempt is made to further determine the shape and properties of the limb signals which display global solar oscillations.

  5. Existence and qualitative properties of travelling waves for an epidemiological model with mutations

    NASA Astrophysics Data System (ADS)

    Griette, Quentin; Raoul, Gaël

    2016-05-01

    In this article, we are interested in a non-monotonic system of logistic reaction-diffusion equations. This system of equations models an epidemic where two types of pathogens are competing, and a mutation can change one type into the other with a certain rate. We show the existence of travelling waves with minimal speed, which are usually non-monotonic. Then we provide a description of the shape of those constructed travelling waves, and relate them to some Fisher-KPP fronts with non-minimal speed.

  6. Magnetic properties of nickel halide hydrates including deuteration effects

    NASA Astrophysics Data System (ADS)

    DeFotis, G. C.; Van Dongen, M. J.; Hampton, A. S.; Komatsu, C. H.; Trowell, K. T.; Havas, K. C.; Davis, C. M.; DeSanto, C. L.; Hays, K.; Wagner, M. J.

    2017-01-01

    Magnetic measurements on variously hydrated nickel chlorides and bromides, including deuterated forms, are reported. Results include locations and sizes of susceptibility maxima, Tmax and χmax, ordering temperatures Tc, Curie constants and Weiss theta in the paramagnetic regime, and primary and secondary exchange interactions from analysis of low temperature data. For the latter a 2D Heisenberg model augmented by interlayer exchange in a mean-field approximation is applied. Magnetization data to 16 kG as a function of temperature show curvature and hysteresis characteristics quite system dependent. For four materials high field magnetization data to 70 kG at 2.00 K are also obtained. Comparison is made with theoretical relations for spin-1 models. Trends are apparent, primarily that Tmax of each bromide hydrate is less than for the corresponding chloride, and that for a given halide nD2O (n=1 or 2) deuterates exhibit lesser Tmax than do nH2O hydrates. A monoclinic unit cell determined from powder X-ray diffraction data on NiBr2·2D2O is different from and slightly larger than that of NiBr2·2H2O. This provides some rationale for the difference in magnetic properties between these.

  7. Nano-structured magnetic metamaterial with enhanced nonlinear properties

    PubMed Central

    Kobljanskyj, Yuri; Melkov, Gennady; Guslienko, Konstantin; Novosad, Valentyn; Bader, Samuel D.; Kostylev, Michael; Slavin, Andrei

    2012-01-01

    Nano-structuring can significantly modify the properties of materials. We demonstrate that size-dependent modification of the spin-wave spectra in magnetic nano-particles can affect not only linear, but also nonlinear magnetic response. The discretization of the spectrum removes the frequency degeneracy between the main excitation mode of a nano-particle and the higher spin-wave modes, having the lowest magnetic damping, and reduces the strength of multi-magnon relaxation processes. This reduction of magnon-magnon relaxation for the main excitation mode leads to a dramatic increase of its lifetime and amplitude, resulting in the intensification of all the nonlinear processes involving this mode. We demonstrate this experimentally on a two-dimensional array of permalloy nano-dots for the example of parametric generation of a sub-harmonic of an external microwave signal. The characteristic lifetime of this sub-harmonic is increased by two orders of magnitude compared to the case of a continuous magnetic film, where magnon-magnon relaxation limits the lifetime. PMID:22745899

  8. Nano-structured magnetic metamaterial with enhanced nonlinear properties.

    PubMed

    Kobljanskyj, Yuri; Melkov, Gennady; Guslienko, Konstantin; Novosad, Valentyn; Bader, Samuel D; Kostylev, Michael; Slavin, Andrei

    2012-01-01

    Nano-structuring can significantly modify the properties of materials. We demonstrate that size-dependent modification of the spin-wave spectra in magnetic nano-particles can affect not only linear, but also nonlinear magnetic response. The discretization of the spectrum removes the frequency degeneracy between the main excitation mode of a nano-particle and the higher spin-wave modes, having the lowest magnetic damping, and reduces the strength of multi-magnon relaxation processes. This reduction of magnon-magnon relaxation for the main excitation mode leads to a dramatic increase of its lifetime and amplitude, resulting in the intensification of all the nonlinear processes involving this mode. We demonstrate this experimentally on a two-dimensional array of permalloy nano-dots for the example of parametric generation of a sub-harmonic of an external microwave signal. The characteristic lifetime of this sub-harmonic is increased by two orders of magnitude compared to the case of a continuous magnetic film, where magnon-magnon relaxation limits the lifetime.

  9. Magnetic and magnetocaloric properties of bulk dysprosium chromite

    SciTech Connect

    McDannald, A.; Kuna, L.; Jain, M.

    2013-09-21

    In this work, a polycrystalline bulk DyCrO{sub 3} sample was prepared by a solution route and the structural and magnetic properties were investigated. The phase purity and ionic valence state of the DyCrO{sub 3} sample were determined by x-ray diffraction/Raman spectroscopy and x-ray photoelectron spectroscopy, respectively. The AC and DC magnetization measurements revealed the onset of antiferromagnetic order at 146 K with an effective moment of 8.88 μ{sub B}. Isothermal magnetization measurements of this material are presented for the first time, showing a peak in the coercive field at 80 K that is explained by the competition between the paramagnetic Dy{sup 3+} and Cr{sup 3+} sublattices. DyCrO{sub 3} was found to display a large magnetocaloric effect (8.4 J/kg K) and relative cooling power (217 J/kg) at 4 T applied field, which renders DyCrO{sub 3} useful for magnetic refrigeration between 5 K and 30 K.

  10. Electronic and magnetic properties of monolayer MnS2

    NASA Astrophysics Data System (ADS)

    Yue, Yunliang

    2016-12-01

    First-principles calculations are performed to study the electronic and magnetic properties of monolayer MnS2. Based on the electronic structure, a half-metallic state is predicted for monolayer MnS2. The magnetic moment is 3.0 μB per formula unit, and the main contribution is localized at the transition metal site Mn with a local moment of 3.733 μB. The magnetic anisotropy energy (MAE) is 0.056 meV per formula unit with an easy axis perpendicular to the plane, and it indicates that monolayer MnS2 belongs to the category of Ising magnets. The positive MAE of nanosheets mainly stems from the area around Γ in the reciprocal space. To find the microscopic origin, we take the method of the second-order spin orbit coupling. The occupied spin-up dz2 state and the unoccupied spin-down dyz states in the Γ point through the Lx operator make positive contributions to the MAE.

  11. Tailoring the magnetic properties of cobalt-ferrite nanoclusters

    NASA Astrophysics Data System (ADS)

    de la Vega, A. Estrada; Garza-Navarro, M. A.; Durán-Guerrero, J. G.; Moreno Cortez, I. E.; Lucio-Porto, R.; González-González, V.

    2016-01-01

    In this contribution, we report on the tuning of magnetic properties of cobalt-ferrite nanoclusters. The cobalt-ferrite nanoclusters were synthesized from a two-step approach that consists of the synthesis of cobalt-ferrite nanoparticles in organic media, followed by their dispersion into aqueous dissolution to form an oil-in-water emulsion. These emulsions were prepared at three different concentrations of the cationic surfactant cetyltrimethylammonium bromide (CTAB), in order to control the size and clustering density of the nanoparticles in the nanoclusters. The synthesized samples were characterized by transmission electron microscopy and their related techniques, such as bright-field and Z-contrast imaging, electron diffraction and energy-dispersive X-ray spectrometry; as well as static magnetic measures. The experimental evidence indicates that the size, morphology, and nanoparticles clustering density in the nanoclusters is highly dependent of the cobalt-ferrite:CTAB molar ratio that is used in their synthesis. In addition, due to the clustering of the nanoparticles into the nanoclusters, their magnetic moments are blocked to relax cooperatively. Hence, the magnetic response of the nanoclusters can be tailored by controlling the size and nanoparticles clustering density.

  12. Size-dependent magnetic properties of iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Patsula, Vitalii; Moskvin, Maksym; Dutz, Silvio; Horák, Daniel

    2016-01-01

    Uniform iron oxide nanoparticles in the size range from 10 to 24 nm and polydisperse 14 nm iron oxide particles were prepared by thermal decomposition of Fe(III) carboxylates in the presence of oleic acid and co-precipitation of Fe(II) and Fe(III) chlorides by ammonium hydroxide followed by oxidation, respectively. While the first method produced hydrophobic oleic acid coated particles, the second one formed hydrophilic, but uncoated, nanoparticles. To make the iron oxide particles water dispersible and colloidally stable, their surface was modified with poly(ethylene glycol) and sucrose, respectively. Size and size distribution of the nanoparticles was determined by transmission electron microscopy, dynamic light scattering and X-ray diffraction. Surface of the PEG-functionalized and sucrose-modified iron oxide particles was characterized by Fourier transform infrared (FT-IR) and Raman spectroscopy and thermogravimetric analysis (TGA). Magnetic properties were measured by means of vibration sample magnetometry and specific absorption rate in alternating magnetic fields was determined calorimetrically. It was found, that larger ferrimagnetic particles showed higher heating performance than smaller superparamagnetic ones. In the transition range between superparamagnetism and ferrimagnetism, samples with a broader size distribution provided higher heating power than narrow size distributed particles of comparable mean size. Here presented particles showed promising properties for a possible application in magnetic hyperthermia.

  13. Magnetic and structural properties of ferrihydrite/hematite nanocomposites

    NASA Astrophysics Data System (ADS)

    Pariona, N.; Camacho-Aguilar, K. I.; Ramos-González, R.; Martinez, Arturo I.; Herrera-Trejo, M.; Baggio-Saitovitch, E.

    2016-05-01

    A rich variety of ferrihydrite/hematite nanocomposites (NCs) with specific size, composition and properties were obtained in transformation reactions of 2-line ferrihydrite. Transmission electron microscopy (TEM) observations showed that the NCs consist of clusters of strongly aggregated nanoparticles (NPs) similarly to a "plum pudding", where hematite NPs "raisins" are surrounded by ferrihydrite "pudding". Magnetic measurements of the NCs correlate very well with TEM results; i.e., higher coercive fields correspond to greater hematite crystallite size. First order reversal curve (FORC) measurements were used for the characterization of the magnetic components of the NCs. FORC diagrams revealed that the NCs prepared at short times are composed by single domains with low coercivity, and NCs prepared at times larger than 60 min exhibited elongated distribution along the Hc axis. It suggested that these samples consist of mixtures of different kinds of hematite particles, ones with low coercivity and others with coercivity greater than 600 Oe. For NCs prepared at times larger than 60 min, Mossbauer spectroscopy revealed the presence of two sextets, which one was assigned to fine hematite particles and other to hematite particles with hyperfine parameters near to bulk hematite. The correlation of the structural and magnetic properties of the ferrihydrite/hematite NCs revealed important characteristics of these materials which have not been reported elsewhere.

  14. Influence of a silica interlayer on the structural and magnetic properties of sol-gel TiO₂-coated magnetic nanoparticles.

    PubMed

    De Matteis, Laura; Fernández-Pacheco, Rodrigo; Custardoy, Laura; García-Martín, María L; de la Fuente, Jesús M; Marquina, Clara; Ibarra, M Ricardo

    2014-05-13

    Superparamagnetic iron oxide nanoparticles coated with titanium dioxide have been synthesized, growing the titanium dioxide directly either on the magnetic nuclei or on magnetic nanoparticles previously coated with a semihydrophobic silica layer. Both coatings have been obtained by sol-gel. Since it is well-known that the existence of the intermediate silica layer influences the physicochemical properties of the material, a detailed characterization of both types of coatings has been carried out. The morphology, structure, and composition of the synthesized nanomatrices have been locally analyzed with subangstrom spatial resolution, by means of aberration corrected transmission electron microscopy (HRTEM and STEM-HAADF). Besides magnetization measurements, proton relaxivity experiments have been also performed on water suspensions of the as-synthesized nanoparticles to investigate the role of the silica interlayer in the relaxometric properties. The silica interlayer leads to nanoparticles with much higher water stability and to higher relaxivity of the suspensions.

  15. Some Considerations about Inferring Coronal Magnetic Fields and Other Coronal Properties from Coronal Emission Line Polarization

    NASA Astrophysics Data System (ADS)

    Arnaud, J.; Habbal, S. R.; Arndt, M.; Woo, R.

    2003-12-01

    Ground based studies of Coronal Emission Lines (CEL) linear polarization had been carried out for the 530.3 nm FeXIV line at Pic du Midi and for the 1074.7 nm Fe XIII line at Sac Peak in the 1977-1980 period. The large scale organization of the polarization has clearly revealed the existence of a large scale structure of the coronal magnetic field. More recently, the first successful eclipse CEL polarimetric measurements were made in the 1074.7 nm line during the total solar eclipse of 21 June 2001, confirming earlier results of the predominance of a radial direction of the coronal magnetic field. A first measurement of the circular polarization in the 1074.7 nm line has also recently been performed. Circular polarization gives access to the strength of the LOS magnetic field while the linear polarization maps the transverse magnetic field direction. We will use ground based and eclipse 1074.7 nm line polarimetric data to provide examples of the properties (e.g., magnetic field, abundances, inhomogeneities) such observations can help to infer in this 3-D and optically thin medium.

  16. Pion and σ-meson Properties in a Strong Magnetic Field

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Fu, Wei-Jie; Liu, Yu-Xin

    2015-09-01

    With the Nambu-Jona-Lasinio (NJL) model we calculate the properties of pion and σ-meson at finite temperature and finite magnetic field. The obtained temperature and magnetic field strength dependence of the constituent quark mass M, the pion and σ-meson masses and the neutral pion decay constant indicates that, in the simple four fermion interaction model, there exists the magnetic catalysis effect. It also shows that the Gell-Mann-Oakes-Renner relation is violated obviously with the increasing of the temperature, and the effect of the magnetic field becomes pronounced only around the critical temperature. The deviation of the critical temperatures obtained with different criteria indicates that the chiral phase transition driven by the temperature in the magnetic field strength region we have considered is in fact a crossover. Supported by the National Natural Science Foundation of China under Grant Nos. 10935001, 11175004, and 11435001, and the National Key Basic Research Program of China under Grant Nos. G2013CB834400 and G2015CB856900

  17. Global existence and uniqueness theorem to 2-D incompressible non-resistive MHD system with non-equilibrium background magnetic field

    NASA Astrophysics Data System (ADS)

    Zhai, Cuili; Zhang, Ting

    2016-09-01

    In this article, we consider the global existence and uniqueness of the solution to the 2D incompressible non-resistive MHD system with non-equilibrium background magnetic field. Our result implies that a strong enough non-equilibrium background magnetic field will guarantee the stability of the nonlinear MHD system. Beside the classical energy method, the interpolation inequalities and the algebraic structure of the equations coming from the incompressibility of the fluid are crucial in our arguments.

  18. Drug delivery property, bactericidal property and cytocompatibility of magnetic mesoporous bioactive glass.

    PubMed

    Liu, Yi-Zhuo; Li, Yang; Yu, Xi-Bin; Liu, Li-Na; Zhu, Zhen-An; Guo, Ya-Ping

    2014-08-01

    A multifunctional magnetic mesoporous bioactive glass (MMBG) has been widely used for a drug delivery system, but its biological properties have been rarely reported. Herein, the effects of mesopores and Fe3O4 nanoparticles on drug loading-release property, bactericidal property and biocompatibility have been investigated by using mesoporous bioactive glass (MBG) and non-mesoporous bioactive glass (NBG) as control samples. Both MMBG and MBG have better drug loading efficiency than NBG because they possess ordered mesoporous channels, big specific surface areas and high pore volumes. As compared with MBG, the Fe3O4 nanoparticles in MMBG not only provide magnetic property, but also improve sustained drug release property. For gentamicin-loaded MMBG (Gent-MMBG), the sustained release of gentamicin and the Fe3O4 nanoparticles minimize bacterial adhesion significantly and prevent biofilm formation against Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). Moreover, the magnetic Fe3O4 nanoparticles in MMBG can promote crucial cell functions such as cell adhesion, spreading and proliferation. The excellent biocompatibility and drug delivery property of MMBG suggest that Gent-MMBG has great potentials for treatment of implant-associated infections.

  19. Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations

    SciTech Connect

    Zhao, Xin; Ke, Liqin; Nguyen, Manh Cuong; Wang, Cai-Zhuang Ho, Kai-Ming

    2015-06-28

    The structures and magnetic properties of Co-Zr-B alloys near the composition of Co{sub 5}Zr with B at. % ≤6% were studied using adaptive genetic algorithm and first-principles calculations. The energy and magnetic moment contour maps as a function of chemical composition were constructed for the Co-Zr-B magnet alloys through extensive structure searches and calculations. We found that Co-Zr-B system exhibits the same structure motif as the “Co{sub 11}Zr{sub 2}” polymorphs, and such motif plays a key role in achieving strong magnetic anisotropy. Boron atoms were found to be able to substitute cobalt atoms or occupy the “interruption” sites. First-principles calculations showed that the magnetocrystalline anisotropy energies of the boron-doped alloys are close to that of the high-temperature rhombohedral Co{sub 5}Zr phase and larger than that of the low-temperature Co{sub 5.25}Zr phase. Our calculations provide useful guidelines for further experimental optimization of the magnetic performances of these alloys.

  20. Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations

    DOE PAGES

    Zhao, Xin; Ke, Liqin; Nguyen, Manh Cuong; ...

    2015-06-23

    The structures and magnetic properties of Co-Zr-B alloys near the composition of Co5Zr with B at. % ≤6% were studied using adaptive genetic algorithm and first-principles calculations. The energy and magnetic moment contour maps as a function of chemical composition were constructed for the Co-Zr-B magnet alloys through extensive structure searches and calculations. We found that Co-Zr-B system exhibits the same structure motif as the “Co11Zr2” polymorphs, and such motif plays a key role in achieving strong magnetic anisotropy. Boron atoms were found to be able to substitute cobalt atoms or occupy the “interruption” sites. First-principles calculations showed that themore » magnetocrystalline anisotropy energies of the boron-doped alloys are close to that of the high-temperature rhombohedral Co5Zr phase and larger than that of the low-temperature Co5.25Zr phase. As a result, our calculations provide useful guidelines for further experimental optimization of the magnetic performances of these alloys.« less

  1. Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations

    SciTech Connect

    Zhao, Xin; Ke, Liqin; Nguyen, Manh Cuong; Wang, Cai -Zhuang; Ho, Kai -Ming

    2015-06-23

    The structures and magnetic properties of Co-Zr-B alloys near the composition of Co5Zr with B at. % ≤6% were studied using adaptive genetic algorithm and first-principles calculations. The energy and magnetic moment contour maps as a function of chemical composition were constructed for the Co-Zr-B magnet alloys through extensive structure searches and calculations. We found that Co-Zr-B system exhibits the same structure motif as the “Co11Zr2” polymorphs, and such motif plays a key role in achieving strong magnetic anisotropy. Boron atoms were found to be able to substitute cobalt atoms or occupy the “interruption” sites. First-principles calculations showed that the magnetocrystalline anisotropy energies of the boron-doped alloys are close to that of the high-temperature rhombohedral Co5Zr phase and larger than that of the low-temperature Co5.25Zr phase. As a result, our calculations provide useful guidelines for further experimental optimization of the magnetic performances of these alloys.

  2. Structural Electronic and Magnetic Properties of Semiconductor Interfaces

    NASA Astrophysics Data System (ADS)

    Continenza, Alessandra

    1990-01-01

    This work is focussed on the structural, electronic and magnetic properties of semiconductor interfaces. The issues and the interest involved in these particular systems are various and have engaged both the scientific and the technological community for more than three decades. The technological interest toward semiconductors is obviously related to device applications while the scientific interest is mainly focussed on the understanding of some characteristic properties, such as potential barriers, carrier properties and band gaps, and how these can be modified by changing different external factors, such as epitaxial growth, strain effects, junctions and doping. A complete knowledge and understanding of these complex issues is, in fact, the basic requirement necessary in order to achieve the ability to "tune" basic properties "at will" and designing the "ad hoc" material for each different device application. We have performed a study of the magnetic, structural and electronic properties of a few particular examples of semiconductor interfaces and heterojunctions namely, rm Fe_{n}/(ZnSe)_ {m}, rm(InAs)_{n }/(InP)_{n} and rm( alpha-Sn)_{n}/(CdTe)_{n }, using the all-electron full-potential linearized augmented plane wave (FLAPW) method. Together with a study of the interface properties, we present results of calculations performed on all the pure constituents, in order to provide comparisons and to better understand how the bulk properties are modified by the interface. In particular, we have analyzed how the properties of these structures can be tailored by changing quantities such as the superlattice periodicity, the epitaxial strain and the interface morphology. We found that the relevance of these factors changes depending on the particular material under study and that it is possible, indeed, to model the characteristics electronic and transport properties of each structure by properly tuning the growth conditions. Our results are in very good agreement with

  3. Magnetic properties of sputtered Permalloy/molybdenum multilayers

    SciTech Connect

    Romera, M.; Ciudad, D.; Maicas, M.; Aroca, C.

    2011-10-15

    In this work, we report the magnetic properties of sputtered Permalloy (Py: Ni{sub 80}Fe{sub 20})/molybdenum (Mo) multilayer thin films. We show that it is possible to maintain a low coercivity and a high permeability in thick sputtered Py films when reducing the out-of-plane component of the anisotropy by inserting thin film spacers of a non-magnetic material like Mo. For these kind of multilayers, we have found coercivities which are close to those for single layer films with no out-of-plane anisotropy. The coercivity is also dependent on the number of layers exhibiting a minimum value when each single Py layer has a thickness close to the transition thickness between Neel and Bloch domain walls.

  4. Electrical and magnetic properties of ion-exchangeable layered ruthenates

    SciTech Connect

    Sugimoto, Wataru . E-mail: wsugi@shinshu-u.ac.jp; Omoto, Masashi; Yokoshima, Katsunori; Murakami, Yasushi; Takasu, Yoshio

    2004-12-01

    An ion-exchangeable ruthenate with a layered structure, K{sub 0.2}RuO{sub 2.1}, was prepared by solid-state reactions. The interlayer cation was exchanged with H{sup +}, C{sub 2}H{sub 5}NH{sub 3}{sup +}, and ((C{sub 4}H{sub 9}){sub 4}N{sup +}) through proton-exchange, ion-exchange, and guest-exchange reactions. The electrical and magnetic properties of the products were characterized by DC resistivity and susceptibility measurements. Layered K{sub 0.2}RuO{sub 2.1} exhibited metallic conduction between 300 and 13K. The products exhibited similar magnetic behavior despite the differences in the type of interlayer cation, suggesting that the ruthenate sheet in the protonated form and the intercalation compounds possesses metallic nature.

  5. Magnetic properties of electrospun non-woven superconducting fabrics

    NASA Astrophysics Data System (ADS)

    Koblischka, Michael R.; Zeng, Xian Lin; Karwoth, Thomas; Hauet, Thomas; Hartmann, Uwe

    2016-03-01

    Non-woven superconducting fabrics were prepared by the electrospinning technique, consisting of Bi2Sr2CaCuO8 (Bi-2212) nanowires. The individual nanowires have a diameter of ˜150-200 nm and lengths of up to 100 μm. A non-woven fabric forming a network with a large number of interconnects results, which enables the flow of transport currents through the entire network. We present here magnetization data [M(T) and M(H)-loops] of this new class of superconducting material. The magnetic properties of these nanowire networks are discussed including the irreversibility line and effects of different field sweep rates, regarding the microstructure of the nanowire networks investigated by electron microscopy.

  6. Ferrite synthesis in microstructured media: Template effects and magnetic properties

    NASA Astrophysics Data System (ADS)

    O'Connor, C. J.; Buisson, Y. S. L.; Li, S.; Banerjee, S.; Premchandran, R.; Baumgartner, T.; John, V. T.; McPherson, G. L.; Akkara, J. A.; Kaplan, D. L.

    1997-04-01

    Inverse micelles and organogels provide novel environments to synthesize ferrite particles. The fluid microstructure provides a template for the synthesis. Our experiments with ferrite synthesis in inverse micelles indicate the formation of superparamagnetic nanoparticles. Of interest is the encapsulation of these particles in polymer microspheres. The encapsulation is done using simple polymer precipitation in the micellar nonsolvent. The process results in a polymer-ferrite composite exhibiting supermagnetism. Low temperature spin glass properties of the composite are characterized through SQUID measurements. These composites have a superparamagnetic blocking temperature of 16 K and follow Curie-Weiss law at temperatures above 60 K with the fitted parameters: C=0.941 emu/g K, θ=-287 K, and TIP=0.0001 emu/g. Since the polymer used is polyphenol, a highly functionalizable material, the composite is well suited for applications in magnetic bioseparations and magnetic coatings.

  7. Tailoring magnetic properties of core/shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Zeng, Hao; Sun, Shouheng; Li, J.; Wang, Z. L.; Liu, J. P.

    2004-08-01

    Bimagnetic FePt /MFe2O4(M =Fe,Co) core/shell nanoparticles are synthesized via high-temperature solution phase coating of 3.5nm FePt core with MFe2O4 shell. The thickness of the shell is controlled from 0.5 to 3nm. An assembly of the core/shell nanoparticles shows a smooth magnetization transition under an external field, indicating effective exchange coupling between the FePt core and the oxide shell. The coercivity of the FePt /Fe3O4 particles depends on the volume ratio of the hard and soft phases, consistent with previous theoretical predictions. These bimagnetic core/shell nanoparticles represent a class of nanostructured magnetic materials with their properties tunable by varying the chemical composition and thickness of the coating materials.

  8. Preparation and magnetic properties of barium hexaferrite nanorods

    SciTech Connect

    Mu Guohong Pan Xifeng; Chen Na; Gan Keke; Gu Mingyuan

    2008-06-03

    The barium hexaferrite nanorods were successfully prepared by sol-gel technique combined with polymethylmethacrylate as template. The crystal structure, morphology and magnetic properties of BaFe{sub 12}O{sub 19} with different shape were investigated with X-ray diffraction, field emission scanning electron microscope and vibrating sample magnetometry. The results show that diameters and lengths of magnetic nanorods are about 60 nm and 300 nm, respectively. The coercivity of rod-shaped BaFe{sub 12}O{sub 19} is increased to 5350 Oe, in comparison with 4800 Oe with plate-shape. The formation mechanism of BaFe{sub 12}O{sub 19} nanorods and reasons resulting in high coercivity are discussed.

  9. Anisotropic Thermal Properties of Nanostructured Magnetic, Carbon and Hybrid Magnetic - Carbon Materials

    NASA Astrophysics Data System (ADS)

    Ramirez, Sylvester

    In this dissertation research we investigated thermal properties of three groups of nanostructured materials: (i) magnetic; (ii) reduced graphene oxide films; and (iii) hybrid magnetic -- graphite -- graphene composites. The thermal measurements were conducted using the transient "hot disk" and "laser flash" techniques. The rare-earth free nanostructured SrFe12O19 permanent magnets were produced by the current activated pressure assisted densification technique. The thermal conductivity of the nanostructured bulk magnets was found to range from 3.8 to 5.6 W/mK for the in-plane and 2.36 W/mk to 2.65 W/mK for the cross-plane directions, respectively. The heat conduction was dominated by phonons near the room temperature. The anisotropy of heat conduction was explained by the brick-like alignment of crystalline grains with the longer grain size in-plane direction. The thermal conductivity scales up with the average grain size and mass density of the material revealing weak temperature dependence. Using the nanostructured ferromagnetic Fe3O4 composites as an example system, we incorporated graphene and graphite fillers into magnetic material without changing their morphology. It was demonstrated that addition of 5 wt. % of equal mixture of graphene and graphite flakes to the composite results in a factor of x2.6 enhancement of the thermal conductivity without significant degradation of the saturation magnetization. We investigated thermal conductivity of free-standing reduced graphene oxide films subjected to a high-temperature treatment of up to 1000°C. It was found that the high-temperature annealing dramatically increased the in-plane thermal conductivity, K, of the films from ˜3 W/mK to ˜61 W/mK at room temperature. The cross-plane thermal conductivity, K⊥, revealed an interesting opposite trend of decreasing to a very small value of ˜0.09 W/mK in the reduced graphene oxide films annealed at 1000°C. The obtained films demonstrated an exceptionally strong

  10. Magnetic Resonance Based Electrical Properties Tomography: A Review

    PubMed Central

    Zhang, Xiaotong; Liu, Jiaen

    2014-01-01

    Frequency-dependent electrical properties (EPs; conductivity and permittivity) of biological tissues provide important diagnostic information (e.g. tumor characterization), and also play an important role in quantifying radiofrequency (RF) coil induced Specific Absorption Rate (SAR) which is a major safety concern in high- and ultrahigh-field Magnetic Resonance Imaging (MRI) applications. Cross-sectional imaging of EPs has been pursued for decades. Recently introduced Electrical Properties Tomography (EPT) approaches utilize the measurable RF magnetic field induced by the RF coil in an MRI system to quantitatively reconstruct the EP distribution in vivo and non-invasively with a spatial resolution of a few millimeters or less. This paper reviews the Electrical Properties Tomography approach from its basic theory in electromagnetism to the state of the art research outcomes. Emphasizing on the imaging reconstruction methods rather than experimentation techniques, we review the developed imaging algorithms, validation results in physical phantoms and biological tissues, as well as their applications in in vivo tumor detection and subject-specific SAR prediction. Challenges for future research are also discussed. PMID:24803104

  11. Copper nanoparticles functionalized PE: Preparation, characterization and magnetic properties

    NASA Astrophysics Data System (ADS)

    Reznickova, A.; Orendac, M.; Kolska, Z.; Cizmar, E.; Dendisova, M.; Svorcik, V.

    2016-12-01

    We report grafting of copper nanoparticles (CuNP) on plasma activated high density polyethylene (HDPE) via dithiol interlayer pointing out to the structural and magnetic properties of those composites. The as-synthesized Cu nanoparticles have been characterized by high-resolution transmission electron microscopy (HRTEM/TEM) and UV-vis spectroscopy. Properties of pristine PE and their plasma treated counterparts were studied by different experimental techniques: X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, energy dispersive X-ray spectroscopy (EDS), zeta potential, electron spin resonance (ESR) and SQUID magnetometry. From TEM and HRTEM analyses, it is found that the size of high purity Cu nanoparticles is (12.2 ± 5.2) nm. It was determined that in the CuNPs, the copper atoms are arranged mostly in the (111) and (200) planes. Absorption in UV-vis region by these nanoparticles is ranging from 570 to 670 nm. EDS revealed that after 1 h of grafting are Cu nanoparticles homogeneously distributed over the whole surface and after 24 h of grafting Cu nanoparticles tend to aggregate slightly. The combined investigation of magnetic properties using ESR spectrometry and SQUID magnetometry confirmed the presence of copper nanoparticles anchored on PE substrate and indicated ferromagnetic interactions.

  12. Stability, electronic and magnetic properties of embedded triangular graphene nanoflakes.

    PubMed

    Dai, Q Q; Zhu, Y F; Jiang, Q

    2012-01-21

    Stability, electronic and magnetic properties of triangular graphene nanoflakes embedded in graphane (graphane-embedded TGNFs) are investigated by density functional theory. It is found that the interface between the embedded TGNF and graphane is stable since the diffusion of H atoms from the graphane region to the embedded TGNF is energetically unfavorable with high energy barriers. The electronic and magnetic properties of the system completely depend on the embedded TGNF. The band gaps of graphane-embedded ATGNFs (armchair-edged TGNFs) arise due to the quantum confinement, while the special characteristics of nonbonding states of graphane-embedded ZTGNFs (zigzag-edged TGNFs) play an important role in their electronic properties. As the edge sizes increase, the differences of band gaps between graphane-embedded TGNFs and the isolated ones decrease. Furthermore, owing to the partially paired p(z) orbitals of edge C atoms, graphane-embedded ZTGNFs exhibit a ferrimagnetic ground state with size-dependant total spin being consistent with Lieb's theorem. Our work provides a possible way to obtain TGNFs without physical cutting.

  13. Magnetic Properties of the Precambrian Granitic Rocks in Minnesota

    NASA Astrophysics Data System (ADS)

    Mochizuki, N.; Jackson, M.; Kogiso, T.; Sato, M.; Seita, K.; Tsunakawa, H.

    2008-12-01

    It has been known that granitic rocks have stable components of natural remanent magnetization (NRM) as well as unstable NRM. It is noted that remanent magnetization of plagioclase crystals in granitic and basaltic rocks can yield reliable paleomagnetic data (e.g. Wu et al., 1974; Geissman et al., 1988; Tarduno et al., 2001; Wakabayashi et al., 2006). The acquisition process of thermoremanent magnetization (TRM) of granitic rocks is not well-understood because the size of magnetic grains varies from less than a few μm to hundreds of μm and parts of them are included in each crystal of granitic rocks. Thus we have made rock-magnetic studies and microscopic observations on granitic rocks and their separated crystals. Samples used in this study are collected from multiple sites of the Sacred Heart Granite (2.6 Ga U-Pb zircon ages) and the St. Cloud Granite and Granodiorite (1.8 Ga U-Pb zircon age) in Minnesota. For most of the bulk samples from granitic rocks, the Verwey transition at 120 K is clearly recognized. Susceptibility- temperature (χ-T) curves show an abrupt drop at about 580°C. Hysteresis parameters of bulk samples are distributed along a mixing line between the multi-domain (MD) and pseudo-single-domain (PSD) areas on the Day plot. Saturation isothermal remanence (SIRM) cooling and warming curves indicate that low-temperature memories range in a few to several tens % of the initial SIRM. These results indicate the MD magnetite grains dominate the magnetic properties but more or less PSD (or single-domain (SD)) magnetite grains are present in the granitic rocks. The separated crystals of feldspar and quartz show the Verwey transition at 120 K and the Curie temperature of about 580°C. Hysteresis properties of them are similar to those of bulk samples. These suggest that the MD and PSD (or SD) magnetite are included in both feldspar and quartz, suggesting that those magnetite grains primarily formed during the initial formation of the granitic rocks. We

  14. Electronic, magnetic and spectroscopic properties of manganese nanostructures

    NASA Astrophysics Data System (ADS)

    Demangeat, C.; Parlebas, J. C.

    2002-11-01

    This paper presents a review of the electronic, magnetic and spectroscopic properties of manganese (Mn)-based nanostructures. In the last few years a variety of techniques have been used to prepare mesoscopic transition-metal islands and novel effects associated with the electronic structure in nanoscale systems have been reported. Mn in the atomic configuration possesses a moment as high as 5μB so it should be very interesting to dope semiconductors with Mn for spin injection or to use Mn itself for permanent magnets. In this paper the introduction (section 1) focuses mainly on metallic Mn nanostructures which are the core of this review. Nevertheless we try to present a general overview of various kinds of Mn structures as well as several theoretical methods with their own limitations to handle the corresponding problems. More precisely, section 2 outlines a variety of bulk, surface, interface and cluster structures with their resulting magnetism as far as Mn is concerned. Actually, in these past two decades, considerable interest has been devoted to Mn nanostructures deposited on various metallic substrates (section 3). Because of its exotic structural and magnetic properties, Mn is indeed an interesting candidate for ultra-thin film growth as it is expected to accept different local configurations. Experimentally, one may attempt to stabilize normally high-temperature phases of Mn by epitaxial growth on a suitable substrate. Specifically, we shall point out the frequently occurring, important situation of magnetically stabilized surface alloys. Next (section 4) we first focus on spectroscopic properties of Mn compounds as well as Mn adsorbates upon graphite and other substrates both experimentally and theoretically. Moreover, we recall a few remarks about Mn impurities with respect to the Kondo problem and also with respect to semiconductors and spintronics. In the latter field, practical applications actually require room-temperature Mn ferromagnetism which

  15. Anisotropic nanomaterials: Synthesis, optical and magnetic properties, and applications

    NASA Astrophysics Data System (ADS)

    Banholzer, Matthew John

    As nanoscience and nanotechnology mature, anisotropic metal nanostructures are emerging in a variety of contexts as valuable class of nanostructures due to their distinctive attributes. With unique properties ranging from optical to magnetic and beyond, these structures are useful in many new applications. Chapter two discusses the nanodisk code: a linear array of metal disk pairs that serve as surface-enhanced Raman scattering substrates. These multiplexing structures employ a binary encoding scheme, perform better than previous nanowires designs (in the context of SERS) and are useful for both convert encoding and tagging of substrates (based both on spatial disk position and spectroscopic response) as well as biomolecule detection (e.g. DNA). Chapter three describes the development of improved, silver-based nanodisk code structures. Work was undertaken to generate structures with high yield and reproducibility and to reoptimize the geometry of each disk pair for maximum Raman enhancement. The improved silver structures exhibit greater enhancement than Au structures (leading to lower DNA detection limits), convey additional flexibility, and enable trinary encoding schemes where far more unique structures can be created. Chapter four considers the effect of roughness on the plasmonic properties of nanorod structures and introduces a novel method to smooth the end-surfaces of nanorods structures. The smoothing technique is based upon a two-step process relying upon diffusion control during nanowires growth and selective oxidation after each step of synthesis is complete. Empirical and theoretical work show that smoothed nanostructures have superior and controllable optical properties. Chapter five concerns silica-encapsulated gold nanoprisms. This encapsulation allows these highly sensitive prisms to remain stable and protected in solution, enabling their use as class-leading sensors. Theoretical study complements the empirical work, exploring the effect of

  16. Microstructure and magnetic property of Co/Cu multilayers

    SciTech Connect

    Kim, P.D.; Song, J.H.; Turpanov, I.A.; Komogortsev, S.V.; Semenov, L.I.; Karpenko, M.M.; Jeong, Y.H.

    1999-09-01

    Co/Cu multilayers consisting of 120 bilayers, [Co(3.5{angstrom})/Cu(t)]{sub 120} with t = 15.8 {angstrom} and 18.3 {angstrom}, were fabricated on glass substrates by dc magnetron sputtering, and their magnetic properties were investigated. The Co layers in a multilayer are found to be an aggregate of ferromagnetic and superparamagnetic Co clusters dispersed in a Cu matrix. The present Co/Cu multilayers are revealed to be periodically modulated granular alloys with stochastic ferromagnetic structure.

  17. Luminescent, magnetic and optical properties of ZnO-ZnS nanocomposites

    NASA Astrophysics Data System (ADS)

    Raleaooa, Pule V.; Roodt, Andreas; Mhlongo, Gugu G.; Motaung, David E.; Kroon, Robin E.; Ntwaeaborwa, Odireleng M.

    2017-02-01

    The structure, particle morphology, optical and magnetic properties of ZnO, ZnS and ZnO-ZnS nanoparticles prepared by the sol-gel method are reported. ZnO and ZnS were combined at room temperature by an ex situ synthetic route to prepare ZnO-ZnS nanocomposites. The nanocomposites exhibited particle morphology different from that of ZnO and ZnS nanoparticles. The ZnO and ZnS nanoparticles exhibited quantum confinement as inferred from the widening of their respective bandgap energies. The electron paramagnetic resonance data provided evidence for the existence of magnetic clusters near the surface, electron to nuclei interactions and defect states. The ZnO-ZnS nanocomposites exhibited tunable emission that was dependent on the ratio of ZnO to ZnS. These composites were evaluated for application in different types of light emitting devices.

  18. On the preparation, structural and magnetic properties of ZnO:Co nanoparticles

    NASA Astrophysics Data System (ADS)

    Varadhaseshan, Radhakrishnan; Meenakshi Sundar, Sankarasubramanian; Prema, Chidambaram

    2014-04-01

    Cobalt doped ZnO nanoparticles were synthesized by microwave irradiation technique for their structural and magnetic properties. Initially the samples were exhibit single phase standard ZnO wurtzite structure (x ≤ 0.1) further Co concentration increase Co3O4 phase was confirmed by X-ray diffraction analysis. The average crystallite sizes of cobalt doped ZnO particles were calculated by Debye-Scherrer formula and are nearly 25 nm. The hexagonal wurtzite structure of ZnO and destroyed cubical Co3O4 were identified in the TEM images. The presence of metal oxide was confirmed by Fourier transform infrared spectral analysis result. The micro-Raman analysis confirmed the existence of Co3O4 phase. Magnetization measurements performed by using vibrating sample magnetometer determine the paramagnetic behavior for the synthesized samples.

  19. Investigation of magnetic sensor properties of magnetic tunnel junctions with superparamagnetic free layer at low frequencies for biomedical imaging applications

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kyohei; Oogane, Mikihiko; Fujiwara, Kousuke; Jono, Junichi; Tsuchida, Masaaki; Ando, Yasuo

    2016-12-01

    The magnetic sensor properties of magnetic tunnel junctions (MTJs) with a superparamagnetic (SP) free layer were systematically investigated at low frequencies (<10 Hz). We prepared four varieties of MTJs with various SP properties by changing the annealing temperature. The temperature dependence of magnetoresistance curves and the signal/noise property at 285 K were evaluated. We found that the SP free layer has the advantage of detecting very small and low-frequency AC magnetic fields compared with a ferromagnetic free layer. The SP free layer strongly suppressed magnetic 1/f noise at low frequencies and expressed a very linear response to a small magnetic field. The obtained properties in MTJs with the SP free layer are suitable for detecting biomagnetic fields. The detectivity was 111 nT at low frequencies (from 0.1 to 10 Hz), which is one of the highest values in single-MTJ sensors.

  20. Enhanced dielectric and magnetic properties of polystyrene added CoFe2O4 magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Vadivel, M.; Babu, R. Ramesh; Ramamurthi, K.; Arivanandhan, M.

    2017-03-01

    In this work, a facile chemical synthesis of polystyrene (PS) added cobalt ferrite (CoFe2O4) magnetic nanoparticles by co-precipitation method is reported and the role of PS concentrations (1, 2, 3, 4 and 5 wt%) on the structural, morphological, dielectric and magnetic properties of CoFe2O4 nanoparticles is investigated. Formation of single phase cubic inverse spinel structure is confirmed by X-ray diffraction and Raman spectral analyses. Transmission electron microscopy studies show that the size of CoFe2O4 nanoparticles can be controlled by varying of PS concentration. Dielectric constant is enhanced due to increase in the PS concentrations in CoFe2O4 nanoparticles. Vibrating sample magnetometer measurements elucidate the enhanced saturation magnetization, coercivity and remanent magnetization in 1, 2 and 3 wt% of PS added CoFe2O4 nanoparticles. Hence the results obtained in this work evidently show that the addition of PS as a surfactant in the synthesis of CoFe2O4 nanoparticles remarkably modify the size of the particles.

  1. Magnetic properties and magnetic domain structure of grain-oriented Fe-3%Si steel under compression

    NASA Astrophysics Data System (ADS)

    Perevertov, O.; Schäfer, R.

    2016-09-01

    The influence of an applied compressive stress on the magnetic properties and domain structure in Goss-textured (110) [001] Fe-3%Si steel is studied. The magnetic domains and magnetization processes were observed by longitudinal Kerr microscopy at different levels of compressive stress. With stress increase the domain structure without applied field evolves from 180° slab-like domains along the surface-parallel easy axis first into stress pattern I, then into the checkerboard pattern and finally into stress pattern II, in which all internal domains are oriented along the transverse axes. The magnetization process under compression is realized by surface closure [001] domains that grow into the bulk at the expense of transverse domains. The domain evolution by these three stress patterns is not practically noticeable in hysteresis curves above 10 MPa—they change continuously with the same effective field being valid for curves from 10 to 67 MPa. The comparison with previous measurements under different stress/cutting angle combinations shows that for the prediction of a constricted hysteresis loop it is sufficient to consider the energy difference between surface-parallel and transverse easy axes neglecting details of the spatial organization of transverse domains.

  2. Two dysprosium-incorporated tungstoarsenates: synthesis, structures and magnetic properties.

    PubMed

    Li, Fengyan; Guo, Weihua; Xu, Lin; Ma, Lifang; Wang, Yuchao

    2012-08-14

    Two dysprosium-containing tungstoarsenates [C(NH(2))(3)](11)[Dy(2)(Hcit)(2)(AsW(10)O(38))]·9H(2)O (1) and K(8-n)H(3-n)[Dy(3-n)K(n)(H(2)O)(3)(CO(3))(A-α-AsW(9)O(34))(A-β-AsW(9)O(34))]·22H(2)O (n = 0 or 1) (2) have been synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, thermogravimetric analyses and infrared spectroscopy. Compound 1 is a citrate-decorated Keggin type di-substituted Ln/POM derivative with the two non-adjacent substituted sites occupied. Compound 2 is composed of two different trivacant Keggin unit isomers [A-α-AsW(9)O(34)](9-) and [A-β-AsW(9)O(34)](9-), linked to each other via one {Dy(3-n)K(n)(H(2)O)(3)(CO(3))}((7 - 2n)+) (n = 0 or 1) unit, where CO(3)(2-) is encapsulated in the triangle plane, resulting in a stable dysprosium carbonate-containing sandwich-type polyoxoanion with D(2h) symmetry. The investigation on both static and dynamic magnetic properties of 1 and 2 show that the magnetic relaxation behavior of 2 appear in a static magnetic field of 5000 Oe, while 1 shows no positive out-of-phase ac susceptibility.

  3. Magnetic properties for cobalt nanorings: Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Ye, Qingying; Chen, Shuiyuan; Zhong, Kehua; Huang, Zhigao

    2012-02-01

    In this paper, two structure models of cobalt nanoring cells (double-nanorings and four-nanorings, named as D-rings and F-rings, respectively) have been considered. Base on Monte Carlo simulation, the magnetic properties of the D-rings and F-rings, such as hysteresis loops, spin configuration, coercivity, etc., have been studied. The simulated results indicate that both D-rings and F-rings with different inner radius ( r) and separation of ring centers ( d) display interesting magnetization behavior and spin configurations (onion-, vortex- and crescent shape vortex-type states) in magnetization process. Moreover, it is found that the overlap between the nearest single nanorings connect can result in the deviation of the vortex-type states in the connected regions. Therefore, the appropriate d should be well considered in the design of nanoring device. The simulated results can be explained by the competition between exchange energy and dipolar energy in Co nanorings system. Furthermore, it is found that the simulated temperature dependence of the coercivity for the D-rings with different d can be well described by Hc= H0 exp[-( T/ T0) p].

  4. Synthesis and Magnetic Properties of Cobalt Ferrite with Different Morphologies

    NASA Astrophysics Data System (ADS)

    Nayak, Bibhuti B.; Nayak, Nadiya Bihary; Mallik, Rahul Kumar; Mondal, Aparna

    Different morphologies (spherical, flake and rod) of cobalt ferrite were synthesized using cobalt salt, iron salts, hydrazine hydrate (as a precipitating agent) and CTAB (surfactant) in water as well as ethylene glycol solvents. Four different synthesis ways (HIS, SIH, HISCO and HISG) were adopted to synthesize cobalt ferrite nanopowders using precipitation method. The as-prepared powders obtained after different synthesis ways were calcined at 800°C and structure, microstructure as well as magnetic properties are studied. X-ray diffraction (XRD), scanning electron microscope (SEM) and magnetization studies using pulsed field loop tracer were employed to characterize these cobalt ferrite powders, prepared using different precipitation ways. All the samples are identified with single phase cobalt ferrite and the crystallite size was found to be around 40 nm. Nearly spherical (multifaceted), rod with flake-like, nearly spherical and rod-like morphologies are obtained while synthesizing using HIS, SIH, HISCO and HISG ways, respectively. Rod with flake-like (SIH sample) and rod-like morphologies (HISG sample) show higher coercivity, than the spherical-like (SIH and HISCO smaples) morphology. The highest coericivty was found to be around 925 Oe for HISG sample and highest magnetization is 67 emu/g for HISCO sample.

  5. Gold and gold-iron oxide magnetic glyconanoparticles: synthesis, characterization and magnetic properties.

    PubMed

    de la Fuente, Jesús M; Alcántara, David; Eaton, Peter; Crespo, Patricia; Rojas, Teresa C; Fernandez, Asunción; Hernando, Antonio; Penadés, Soledad

    2006-07-06

    The preparation, characterization and the magnetic properties of gold and gold-iron oxide glyconanoparticles (GNPs) are described. Glyconanoparticles were prepared in a single step procedure in the presence of aqueous solution of thiol functionalized neoglycoconjugates and either gold salts or both gold and iron salts. Neoglycoconjugates of lactose and maltose disaccharides with different linkers were used. Iron-free gold or gold-iron oxide GNPs with controlled gold-iron ratios were obtained. The average core-size diameters are in the range of 1.5-2.5 nm. The GNPs are fully characterized by (1)H NMR spectrometry, transmission electron microscopy (TEM), and UV-vis and X-ray absorption (XAS) spectroscopies. Inductive plasma-atomic emission spectrometry (ICP) and elemental analysis gave the average number of neoglycoconjugates per cluster. The magnetic properties were measured in a SQUID magnetometer. The most remarkable results was the observation of a permanent magnetism up to room temperature in the iron-free gold GNPs, that was not present in the corresponding gold-iron oxide GNPs.

  6. Magnetic properties and loss separation in iron-silicone-MnZn ferrite soft magnetic composites

    SciTech Connect

    Wu, Shen; Sun, Aizhi; Xu, Wenhuan; Zou, Chao; Yang, Jun; Dong, Juan

    2013-12-16

    This paper investigates the magnetic and structural properties of iron-based soft magnetic composites coated with silicone-MnZn ferrite hybrid. The organic silicone resin was added to improve the flexibility of the insulated iron powder and causes better adhesion between particles to increase the mechanical properties. Scanning electron microscopy and distribution maps show that the iron particle surface is covered with a thin layer of silicone-MnZn ferrite. Silicone-MnZn ferrite coated samples have higher permeability when compared with the non-magnetic silicone resin coated compacts. The real part of permeability increases by 34.18% when compared with the silicone resin coated samples at 20 kHz. In this work, a formula for calculating the total loss component by loss separation method is presented and finally the different parts of total losses are calculated. The results show that the eddy current loss coefficient is close to each other for the silicone-MnZn ferrite, silicone resin and MnZn ferrite coated samples (0.0078

  7. Synthesization and magnetic properties of Ba1-xYxFe12O19 hexaferrites prepared by solid-state reaction method

    NASA Astrophysics Data System (ADS)

    Rehman, Khalid Mehmood Ur; Liu, Xiansong; Li, Mingling; Jiang, Shuai; Wu, Yingchun; Zhang, Cong; Liu, Chaocheng; Meng, Xiangyu; Li, Haohao

    2017-03-01

    M-type hexaferrite Ba(1-x)YxFe12O19 (x=0.00, 0.02, 0.05, 0.08, 0.10, 0.13) magnetic powder and magnets existed to ready according to the conventional ceramic reaction method. X-ray difractometer was used to study the phase compositions of the calcites powder samples. There was a single magnetoplumbite segment in the calcanei magnetic powder with the intensification of x=0.00, 0.02, 0.05, 0.08, 0.10, 0.13. The influence of yttrium aggregation on attractive possessions of the magnets was studied scientifically. The magnetic properties of the magnets were measured by a magnetic properties test instrument (VSM). The saturation magnetization (σs) and coercivity (Hcj) of the Ba(1-x)YxFe12O19 (x=0.00, 0.02, 0.05, 0.08, 0.10, 0.13) magnetic powders with different Yttrium aggregation (x) were determined. The saturation magnetization (σs) was decreased whereas coercivity (Hcj) was increased. The magnetic properties of the magnet at x=0.13 reached the maximum values.

  8. Transport properties of high-temperature air in a magnetic field

    SciTech Connect

    Bruno, D.; Capitelli, M.; Catalfamo, C.; Giordano, D.

    2011-01-15

    Transport properties of equilibrium air plasmas in a magnetic field are calculated with the Chapman-Enskog method. The range considered for the temperature is [50-50 000] K and for the magnetic induction is [0-300] T.

  9. Magnetic and Structural Properties of Chemically Synthesized Ni and

    NASA Astrophysics Data System (ADS)

    Bonder, Michael; Leslie-Pelecky, Diandra L.; Zhang, X. Q.; Rieke, R. D.

    1996-03-01

    The reduction of nickel salts using a technique developed by Rieke and co-workers produces highly chemically reactive particles with enhanced magnetic properties due to their nanoscale size. As-synthesized particles are 2-5 nm in diameter and range from superparamagnetic to ferromagnetic, depending on synthesis details. Grain sizes from 5 nm to 1000 nm have been produced by subsequent vacuum annealing. The maximum coercivities and remanence ratios are obtained during the first half-hour to hour of annealing. Coercivities in these systems may be up to ten times the value of bulk nickel, with remanence ratios approaching 0.5. Transmission electron microscopy shows that the nickel grains are square and sometimes embedded in a lithium halide matrix. Under appropriate synthesis and annealing conditions, the as-synthesized particles can be transformed into the metastable Ni_3C phase, which has important implications in catalysis. Comparison with Stoner-Wohlfarth and Holz-Scherrer predictions of the magnetic properties will be made.

  10. Structural and magnetic properties of chromium doped zinc ferrite

    SciTech Connect

    Sebastian, Rintu Mary; Thankachan, Smitha; Xavier, Sheena; Mohammed, E. M.; Joseph, Shaji

    2014-01-28

    Zinc chromium ferrites with chemical formula ZnCr{sub x}Fe{sub 2−x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125 nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM)

  11. Magnetic properties of ZnFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Guskos, Niko; Glenis, Spiros; Typek, Janusz; Zolnierkiewicz, Grzegorz; Berczynski, Pawel; Wardal, Kamil; Guskos, Aleksander; Sibera, Daniel; Moszyński, Dariusz; Lojkowski, Witold; Narkiewicz, Urszula

    2012-04-01

    Fine particles of ZnFe2O4 were synthesized by a wet chemical method in the (80 wt.% Fe2O3 + 20 wt.% ZnO) system. The morphological and structural properties of the mixed system were investigated by scanning electron microscopy, X-ray diffraction, inductively coupled plasma atomic emission, and X-ray photoelectron spectroscopy. The major phase was determined to be the ZnFe2O4 spinel with particle size of 11 nm. The magnetic properties of the material were investigated by ferromagnetic resonance (FMR) in the temperature range from liquid helium to room temperature. A very intense, asymmetric FMR signal from ZnFe2O4 nanoparticles was recorded, which has been analyzed in terms of two Callen-lineshape lines. Temperature dependence of the FMR parameters was obtained from fitting the experimental lines with two component lines. Analysis of the FMR spectra in terms of two separate components indicates the presence of strongly anisotropic magnetic interactions.

  12. Mimicking the magnetic properties of rare earth elements using superatoms.

    PubMed

    Cheng, Shi-Bo; Berkdemir, Cuneyt; Castleman, A W

    2015-04-21

    Rare earth elements (REs) consist of a very important group in the periodic table that is vital to many modern technologies. The mining process, however, is extremely damaging to the environment, making them low yield and very expensive. Therefore, mimicking the properties of REs in a superatom framework is especially valuable but at the same time, technically challenging and requiring advanced concepts about manipulating properties of atom/molecular complexes. Herein, by using photoelectron imaging spectroscopy, we provide original idea and direct experimental evidence that chosen boron-doped clusters could mimic the magnetic characteristics of REs. Specifically, the neutral LaB and NdB clusters are found to have similar unpaired electrons and magnetic moments as their isovalent REs (namely Nd and Eu, respectively), opening up the great possibility in accomplishing rare earth mimicry. Extension of the superatom concept into the rare earth group not only further shows the power and advance of this concept but also, will stimulate more efforts to explore new superatomic clusters to mimic the chemistry of these heavy atoms, which will be of great importance in designing novel building blocks in the application of cluster-assembled nanomaterials. Additionally, based on these experimental findings, a novel "magic boron" counting rule is proposed to estimate the numbers of unpaired electrons in diatomic LnB clusters.

  13. Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

    SciTech Connect

    Kumar, Sumeet; Ojha, Animesh K.; Srivastava, Manish E-mail: manish-mani84@rediffmail.com; Singh, Jay; Layek, Samar; Yashpal, Madhu; Materny, Arnulf

    2015-02-15

    In the present study, monodispersed CeO{sub 2} nanoparticles (NPs) of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM) measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce{sup 4+} into Ce{sup 3+} at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm{sup -1} for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce{sup 3+} ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce) ions located around oxygen vacancies, which causes ferromagnetism in pure CeO{sub 2} samples.

  14. Homometallic and Heterometallic Antiferromagnetic Rings: Magnetic Properties Studied by Nuclear Magnetic Resonance

    SciTech Connect

    Casadei, Cecilia

    2011-01-01

    The aim of the present thesis is to investigate the local magnetic properties of homometallic Cr8 antiferromagnetic (AFM) ring and the changes occurring by replacing one Cr3+ ion with diamagnetic Cd2+ (Cr7Cd) and with Ni2+ (Cr7Ni). In the heterometallic ring a redistribution of the local magnetic moment is expected in the low temperature ground state. We have investigated those changes by both 53Cr-NMR and 19F-NMR. We have determined the order of magnitude of the transferred hyperfine coupling constant 19F - M+ where M+ = Cr3+, Ni2+ in the different rings. This latter result gives useful information about the overlapping of the electronic wavefunctions involved in the coordinative bond.

  15. Magnetic Properties of Fe Oxide Nanoparticles Produced by Laser Pyrolysis for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    García, M. A.; Bouzas, V.; Costo, R.; Veintemillas, S.; Morales, P.; García-Hernández, M.; Alexandrescu, R.; Morjan, I.; Gasco, P.

    2010-10-01

    We report on the magnetic characterization of Fe oxide nanoparticles by laser pyrolysis and the relationship between the preparation conditions and the magnetic response. It is shown that controlling the preparation conditions during the pyrolisis allows tuning the nanoparticles morphology and structure and consequently the magnetic properties of the nanoparticles. The nanoparticles are loaded into solid lipid nanoparticles without degradation nor significant modification of the magnetic properties.

  16. AC Magnetic Properties of Large Volume of Water — Susceptibility Measurement in Unshielded Environment

    NASA Astrophysics Data System (ADS)

    Tsukada, Keiji; Kiwa, Toshihiko; Masuda, Yuuki

    2006-10-01

    To investigate the effect of low-frequency magnetic-field exposure of a human body, the low-frequency AC magnetic property of a large volume of water was measured by low-frequency magnetic field exposure (from 50 Hz to 1.2 kHz). The results indicate that the AC magnetic property of water is due to diamagnetism in the low-frequency range. The phase between the main magnetic field and the generated magnetic field remained constant at about 180°. Results were not affected by conductivity or pH. Moreover, the magnetic-field strength from water showed a susceptibility frequency dependence proportional to the frequency above approximately 400 Hz. Because of the incremental effects of susceptibility, the magnetic field from water was measured using a conventional magnetic sensor (magnetic resistive; MR) in an unshielded environment.

  17. Magnetism as a distortion of a pre-existent primordial energy field and the possibility of extraction of electrical energy directly from space

    NASA Astrophysics Data System (ADS)

    Depalma, Bruce

    The spatial distortion induced into the homogeneous primordial energy field (PEF) by the anisotropy of the magnet is what is called magnetism. It is the thesis here that the distortion of the PEF occasioned by the magnet is the operative principle in the class of machinery known as induction machines. The PEF is also distorted as a consequence of the spatial reaction to the centripetal force field existing within the rotating magnetized conductor. Based on an effect first discovered by Michael Faraday in 1831, the N machine/space power generator is an electrical machine which has the possibility of producing electrical energy with significantly less mechanical power input than the presently used induction machines.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  19. Magneto-optical and catalytic properties of Fe3O4@HA@Ag magnetic nanocomposite

    NASA Astrophysics Data System (ADS)

    Amir, Md.; Güner, S.; Yıldız, A.; Baykal, A.

    2017-01-01

    Fe3O4@HA@Ag magnetic nanocomposites (MNCs) were successfully synthesized by the simple reflux method for the removal of azo dyes from the industrial aqueous media. Fe3O4@HA@AgMNCs exhibited high catalytic activity to reduce MB within 20 min from the waste water. The obtained materials were characterized by the means of different techniques. Powder X-ray diffraction (XRD) analysis confirmed the single-phase of Fe3O4 spinel structure. SEM and TEM analysis indicated that Fe3O4@HA@AgMNCs were nanoparticles like structure with small agglomeration. TG result showed that the products contained 9% of HA. The characteristic peaks of HA at 1601 cm-1 and 1703 cm-1 was observed by the means of FT-IR spectra of Fe3O4@HA@AgMNCs. The hysteresis (σ-H) curves revealed Fe3O4@HA@Ag MNCs exhibit a typical superparamagnetic characteristic with a saturation magnetization of 59.11 emu/g and measured magnetic moment is 2.45 μB. The average magnetic particle dimension (Dmag) is 13.25 nm. In accordance, the average crystallite and particle dimensions were obtained as 11.50 nm and 13.10 nm from XRD and TEM measurements, respectively. Magnetocrystalline anisotropy was offered as uniaxial and calculated effective anisotropy constant (Keff) is 2.96×105 Erg/g. The blocking temperature was estimated as 522 K. The size-dependent saturation magnetization suggests the existence of a magnetically dead layer as 0.793 nm for Fe3O4@HA@Ag MNCs. The UV-vis diffuse reflectance spectroscopy (DRS) and Kubelka-Munk theory were applied to determine the optical properties of powder samples. The direct optical energy band gap (Eg) values were estimated from Tauc plots between 1.62 eV and 2.12 eV.

  20. Structural, electrical and magnetic properties of Sc3+ doped Mn-Zn ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Angadi, V. Jagdeesha; Choudhury, Leema; Sadhana, K.; Liu, Hsiang-Lin; Sandhya, R.; Matteppanavar, Shidaling; Rudraswamy, B.; Pattar, Vinayak; Anavekar, R. V.; Praveena, K.

    2017-02-01

    Sc3+ doped Mn0.5Zn0.5ScyFe2-yO4 (y=0.00, 0.01, 0.03 and 0.05) nanoparticles were synthesized by solution combustion method using mixture of fuels were reported for the first time. The mixture of fuels plays an important role in obtaining nano crystalline, single phase present without any heat treatment. X-ray diffraction (XRD) results confirm the formation of the single-phase ferrites which crystallize in cubic spinel structure. The Fourier transform infrared spectra (FTIR) exhibit two prominent bands around 360 cm-1 and 540 cm-1 which are characteristic feature of spinel ferrite. The transmission electron microscope (TEM) micrographs revealed the nanoparticles to be nearly spherical in shape and of fairly uniform size. The room temperature impedance spectra (IS) and vibrating sample magnetometry (VSM) measurements were carried out in order to study the effect of doping (Sc3+) on the characteristic properties of Mn-Zn ferrites. Further, the frequency dependent dielectric constant and dielectric loss were found to decrease with increasing multiple Sc3+ concentration. Nyquist plot in the complex impedance spectra suggest the existence of multiple electrical responses. Magnetic measurements reveals that saturation magnetization (Ms), remnant magnetization (Mr), magnetic moment (ηB) and magnetic particle size (Dm) increase with Sc3+ ion concentration up to x=0.03 and then decrease. The values of spin canting angle (αY-K) and the magnetic particle size (Dm) are found to be in the range of 68-75° and 10-19 nm respectively with Sc3+ concentration. The room temperature Mössbauer spectra were fitted with two sextets corresponding to ions at tetrahedral (A-) and octahedral (B-) sites confirms the spinel lattice. The ferromagnetic resonance (FMR) spectra's has shown that high concentration of scandium doping leads to an increase in dipolar interaction and decrease in super exchange interaction.

  1. The effect of Cr substitution on the structural, electronic and magnetic properties of pulsed laser deposited NiFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Panwar, Kalpana; Tiwari, Shailja; Bapna, Komal; Heda, N. L.; Choudhary, R. J.; Phase, D. M.; Ahuja, B. L.

    2017-01-01

    We have studied the structural, electronic and magnetic properties of pulsed laser deposited thin films of Ni1-xCrxFe2O4 (x=0.02 and 0.05) on Si (111) and Si (100) substrates. The films reveal single phase, polycrystalline structure with larger grain size on Si (111) substrate than that on Si (100) substrate. Contrary to the expected inverse spinel structure, x-ray photoemission (XPS) studies reveal the mixed spinel structure. XPS results suggest that Ni and Fe ions exist in 2+ and 3+ states, respectively, and they exist in tetrahedral as well as octahedral sites. The deviation from the inverse spinel leads to modified magnetic properties. It is observed that saturation magnetization drastically drops compared to the expected saturation value for inverse spinel structure. Strain in the films and lattice distortion produced by the Cr doping also appear to influence the magnetic properties.

  2. Effect of the synthesis conditions on the magnetic and electrical properties of the BaFeO{sub 3-x} oxide: A metamagnetic behavior

    SciTech Connect

    Gil de Muro, Izaskun . E-mail: qiproapt@lg.ehu.es

    2005-05-15

    The BaFeO{sub 2.95} oxide has been obtained from thermal decomposition of the [BaFe(C{sub 3}H{sub 2}O{sub 4}){sub 2}(H{sub 2}O){sub 4}] metallo-organic precursor at 800 deg. C under atmospheric oxygen pressure as small and homogeneous particles. From electronic paramagnetic resonance data, a metallic behavior in the 230-130K temperature range has been observed. Magnetic measurements confirm the existence of a ferro-antiferromagnetic transition at 178K. The magnetic properties of the BaFeO{sub 2.95} oxide are strongly dependent on both temperature and magnetic field with a metamagnetic behavior. The synthesis conditions play an important role on the morphology and the electrical and magnetic properties. The syntherization of the sample produces a dramatic change in the transport properties and the existence of conductivity disappears.

  3. Chromium removal by combining the magnetic properties of iron oxide with adsorption properties of carbon nanotubes.

    PubMed

    Gupta, V K; Agarwal, Shilpi; Saleh, Tawfik A

    2011-03-01

    The adsorption features of multiwall carbon nanotubes (MWCNTs) with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. Composites of MWCNT/nano-iron oxide were prepared, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR). XRD suggests that the magnetic phase formed is maghemite and/or magnetite. FESEM image shows nano-iron oxides attached to a network of MWCNTs. The adsorption capability of the composites was tested in batch and fixed bed modes. The composites have demonstrated a superior adsorption capability to that of activated carbon. The results also show that the adsorptions of Cr(III) on the composites is strongly dependent on contact time, agitation speed and pH, in the batch mode; and on flow rate and the bed thickness in the fixed bed mode. Along with the high surface area of the MWCNTs, the advantage of the magnetic composite is that it can be used as adsorbent for contaminants in water and can be subsequently controlled and removed from the medium by a simple magnetic process.

  4. Magnetic properties of Ni substituted Y-type barium ferrite

    NASA Astrophysics Data System (ADS)

    Won, Mi Hee; Kim, Chul Sung

    2014-05-01

    Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type hexaferrites have higher magnetic ordering temperature than other Y-type. We have investigated macroscopic and microscopic properties of Y-type barium hexaferrite. Ba2Co2-xNixFe12O22 (x = 0, 0.5, 1.0, 1.5, and 2.0) samples are prepared by solid-state reaction method and studied by X-ray diffraction (XRD), vibrating sample magnetometer, and Mössbauer spectroscopy, as well as a network analyzer for high frequency characteristics. The XRD pattern is analyzed by Rietveld refinement method and confirms the hexagonal structure with R-3m. The hysteresis curve shows ferrimagnetic behavior. Saturation magnetization (Ms) decreases with Ni contents. Ni2+, which preferentially occupies the octahedral site with up-spin sub-lattice, has smaller spin value S of 1 than Co2+ having S = 3/2. The zero-field-cooled (ZFC) measurement of Ba2Co1.5Ni0.5Fe12O22 shows that Curie and spin transition temperatures are found to be 718 K and 209 K, respectively. The Curie temperature TC is increased with Ni contents, while TS is decreased with Ni. The Mössbauer spectra were measured at various temperatures and fitted by using a least-squares method with six sextet of six Lorentzian lines for Fe sites, corresponding to the 3bVI, 6cIV*, 6cVI, 18hVI, 6cIV, and 3aIV sites at below TC. From Mössbauer measurements, we confirmed the spin state of Fe ion to be Fe3+ and obtained the isomer shift (δ), magnetic hyperfine field (Hhf), and the occupancy ratio of Fe ions at six sub-lattices. The complex permeability and permittivity are measured between 100 MHz and 4 GHz, suggesting that Y-type barium hexaferrite is promising for antenna applications in UHF band.

  5. Magnetic properties of Ni substituted Y-type barium ferrite

    SciTech Connect

    Won, Mi Hee; Kim, Chul Sung

    2014-05-07

    Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type hexaferrites have higher magnetic ordering temperature than other Y-type. We have investigated macroscopic and microscopic properties of Y-type barium hexaferrite. Ba{sub 2}Co{sub 2−x}Ni{sub x}Fe{sub 12}O{sub 22} (x = 0, 0.5, 1.0, 1.5, and 2.0) samples are prepared by solid-state reaction method and studied by X-ray diffraction (XRD), vibrating sample magnetometer, and Mössbauer spectroscopy, as well as a network analyzer for high frequency characteristics. The XRD pattern is analyzed by Rietveld refinement method and confirms the hexagonal structure with R-3m. The hysteresis curve shows ferrimagnetic behavior. Saturation magnetization (M{sub s}) decreases with Ni contents. Ni{sup 2+}, which preferentially occupies the octahedral site with up-spin sub-lattice, has smaller spin value S of 1 than Co{sup 2+} having S = 3/2. The zero-field-cooled (ZFC) measurement of Ba{sub 2}Co{sub 1.5}Ni{sub 0.5}Fe{sub 12}O{sub 22} shows that Curie and spin transition temperatures are found to be 718 K and 209 K, respectively. The Curie temperature T{sub C} is increased with Ni contents, while T{sub S} is decreased with Ni. The Mössbauer spectra were measured at various temperatures and fitted by using a least-squares method with six sextet of six Lorentzian lines for Fe sites, corresponding to the 3b{sub VI}, 6c{sub IV}*, 6c{sub VI}, 18h{sub VI}, 6c{sub IV}, and 3a{sub IV} sites at below T{sub C}. From Mössbauer measurements, we confirmed the spin state of Fe ion to be Fe{sup 3+} and obtained the isomer shift (δ), magnetic hyperfine field (H{sub hf}), and the occupancy ratio of Fe ions at six sub-lattices. The complex permeability and permittivity are measured between 100 MHz and 4 GHz, suggesting that Y-type barium hexaferrite is promising for antenna

  6. Fe-based magnetic nanomaterials: Wet chemical synthesis, magnetic properties and exploration on applications

    NASA Astrophysics Data System (ADS)

    Xiaoliang, Hong

    Even though the start of research based on Fe-based magnetic nanomaterials could be dated back to hundreds years ago, the considerably large amount of emerging fields for their applications, including spintronic structures in information storage, biomedical and environmental applications, magnetic sensors, magnetic energy harvesters, has spurred renewed interest on the application-related properties of Fe-based nanomaterial in both the nanoparticle and film forms. Besides, an exploration of a simple, wide, effective technique that can be used for growth of high-quality Fe-based magnetic nanoparticles and films is of great importance for better materialization of these potential Fe-based devices. This thesis mainly focuses on fabricating different magnetic Fe-based materials (ferrites and ferrous alloys, nanoparticle and film) with wet chemical method, investigating their growth mechanism and magnetic and electrical properties. In addition, the possible applications of as-fabricated Fe-based nanoparticles and films are studied. The contribution of the work is summarized as below: (1) Investigation indicated that the external magnetic field plays an important role in determining the microstructure, magnetic properties of the Fe3O4 nanoparticles. The magnetic field can promote the change of Fe3O4 nanocuboctahedrons to nanocubes. Compared the hyperthermia property of as-fabricated nanocuboctahedrons and nanocubes Fe3O4, the intrinsic loss power (ILP) of the Fe3O4 nanocubes was much higher than that of nanocuboctahedrons due to the surface magnetic effect. (2) A general and facile method for broadly deposition of thick Fe 3O4 film and other ferrites has been demonstrated. It had been found that the epitaxial high-quality Fe3O4 film could be deposited either on MgO substrates directly or Si substrates with Fe3O4 seed layer deposited by PLD. As-deposited Fe 3O4 film could be easily patterned and shows potential applications for microwave and MEMS supercapacitor. Besides

  7. Magnetic Properties of Obsidians from the Southwestern U.S

    NASA Astrophysics Data System (ADS)

    Sternberg, R. S.; Gilder, S.; Renne, P. R.; Shackley, S.

    2010-12-01

    Geochemical signatures of Southwestern U.S. obsidians have been intensively studied, in part to use as a provenance method for archaeological obsidians (Shackley, 2005). We have examined magnetic properties of unoriented samples from 10 geologic obsidian sources in Arizona, Nevada, and New Mexico. Five samples from each source were used, and each sample was cut into two specimens. Magnetic susceptibilities of all 100 specimens were measured on a susceptometer at F&M; alternating field demagnetizations of all 100 specimens were done on a cryogenic magnetometer at the BGC; and hysteresis curves, back-field IRMs, and thermomagnetic curves were done for nine specimens on a VFTB at LMU. The overall mean and interquartile range for susceptibilities of all 100 specimens are 56 and 9-85 x10-8 m3/kg. The overall mean and interquartile range for the NRM of all 100 specimens are 3.4 and 0.40-8.5 x10-4 A m2/kg. Variability within source groups is considerably smaller, so that a scatter plot of NRM against susceptibility (Figure 1) shows that several of the sites can be discriminated based on these two properties. AF demagnetization shows that in the large majority of cases a characteristic magnetic direction is isolated by 150 mT peak field. The overall mean and interquartile range for the median destructive fields for all 100 specimens are 96 and 52-117 mT. For the nine specimens used to measure hysteresis curves, seven of these plot in the middle of the pseudosingle domain field on a Day plot, while the other two plot on the boundary between the pseudosingle and the multidomain fields. All of these samples have a Curie temperature component just below 580°C. Eight of these nine samples have a low-temperature Curie temperature component lower than 200°C. We plan to further examine this component using low temperatures, and to consider statistical discrimination of these different sources using multivariate statistics applied to these various properties.

  8. A facile route to synthesize core/shell structured carbon/magnetic nanoparticles hybrid and their magnetic properties

    SciTech Connect

    Qi, Xiaosi; Xu, Jianle; Zhong, Wei; Du, Youwei

    2015-07-15

    Graphical abstract: Controllable synthesis of core/shell structured carbon/magnetic nanoparticles hybrid and their tunable magnetic properties. - Highlights: • The paper reports a simple route for core/shell structured carbon/magnetic nanoparticles hybrid. • By controlling the temperature, Fe{sub 3}O{sub 4}@CNCs, Fe@HCNTs and Fe@LCNTs were produced selectively. • The magnetic properties of the obtained core/shell structured hybrid could be tuned effectively. - Abstract: By controlling the pyrolysis temperature, core/shell structured Fe{sub 3}O{sub 4}/carbon nanocages, Fe/helical carbon nanotubes and Fe/low helicity of carbon nanotubes could be synthesized selectively over Fe{sub 2}O{sub 3} nanotubes generated by a hydrothermal method. The transmission electron microscopic and scanning electron microscopic investigations revealed that the efficiency of generating core/shell structured hybrid was high, exceeding 90%. Because of the magnetic nanoparticles tightly wrapped in graphitic layers, the obtained core/shell structured hybrids showed high stability and good magnetic properties. And the magnetic properties of the obtained core/shell structured hybrid could be tuned by the decomposition temperature and time. Therefore, a simple, inexpensive and environment-benign route was proposed to produce magnetism-tunable core/shell structured hybrid in large quantities.

  9. Magnetic grain-size variations through an ash flow sheet - Influence on magnetic properties and implications for cooling history

    NASA Astrophysics Data System (ADS)

    Rosenbaum, J. G.

    1993-07-01

    The effect of the magnetic grain size on magnetic properties was examined in a section through a Miocene rhyolitic ash flow sheet, the Tiva Canyon Member of the Paintbrush Tuff. Measurements included determinations of NRM, in-phase magnetic susceptibility, quadrature magnetic susceptibility, saturation isothermal remanent magnetization, and coercivity of remanence. It was found that cubic Fe-oxide microcrystals, which include both magnetite and maghemite, are important contributors to magnetic susceptibility and remanent magnetization in two approximately 15-m-thick zones at the top and the bottom of an 84-m-thick section of the ash flow sheet. The intervening 50 m are dominated by coarser titanomagnetite phenocrystals, which are the remanence carriers.

  10. Magnetic resonance electric property imaging of brain tissues.

    PubMed

    Zhang, Xiaotong; Zhu, Shanan; He, Bin

    2009-01-01

    The electric properties (EPs) of brain tissues, i.e., the electric conductivity and permittivity, can provide important information for diagnosis of various brain disorders. A high-field MRI system is accompanied by significant wave propagation effects, and the radio frequency (RF) radiation is dependent on EPs of the biological tissue. Based on the measurement of the active transverse magnetic component of the applied RF field (known as B1-mapping technique), we have developed a dual-excitation algorithm, which uses two sets of measured B1 data, to noninvasively reconstruct the biological tissue's electric properties. A series of computer simulations were conducted to evaluate the feasibility and performance of the proposed method on a 3-D head model within a birdcage coil and a transverse electromagnetic coil. Compared with other B1-mapping based reconstruction algorithms, our approach provides superior performance without the need for iterative computations. The present simulation results indicate good reconstruction of electric properties of brain tissues from noninvasive MRI B1 mapping.

  11. Magnetic properties of Fe-Mn-Pt for heat assisted magnetic recording applications

    NASA Astrophysics Data System (ADS)

    Park, Jihoon; Hong, Yang-Ki; Kim, Seong-Gon; Gao, Li; Thiele, Jan-Ulrich

    2015-02-01

    We calculate the electronic structures of FePt and Fe0.5Mn0.5Pt using first-principles calculations based on density functional theory within the local-spin-density approximation. The Curie temperature (Tc) was calculated by mean field approximation. Composition dependence of the Cure temperature (Tc(x)) of Fe1-xMnxPt was used to identify a composition to meet the desired Tc in the range of 600-650 K. The identified composition (0.0294 ≤ x ≤ 0.0713) gives saturation magnetization (Ms) in the range of 1041-919 emu/cm3 and magnetocrystalline anisotropy constant (K) in the range of 9.96-8.36 × 106 J/m3 at 0 K. Temperature dependent M(T) and K(T) of Fe1-xMnxPt (0.0294 ≤ x ≤ 0.0713) were calculated using the Brillouin function and Callen-Callen experimental relation, respectively. Fe1-xMnxPt (0.0294 ≤ x ≤ 0.0713) shows 930-800 emu/cm3 of Ms and 7.18-5.61 × 106 J/m3 of K at 300 K, thereby satisfying desired magnetic properties for heat-assisted magnetic recording media to achieve 4 Tb/in.2 areal density.

  12. Structural and magnetic properties of electrospun FeCoNi magnetic nanofibers with nanogranular phases

    NASA Astrophysics Data System (ADS)

    Park, Ji Hea; Kweon, Soon C.; Kim, Sang Woo

    2012-02-01

    Structural and magnetic properties of silicon/aluminum-added and -free FeCoNi magnetic alloy nanofibers with nanogranular phases prepared by electrospinning and subsequent annealing of the PVP-blended ternary metal precursors in hydrogen atmosphere were investigated. The FeCoNi magnetic alloy nanofibers with evenly distributed nanocrystalline phases were formed, which are identified as γ-Fe1- x Ni x binary phase with face-centered cubic structure and α-CoFe phase with body-centered cubic structure. At elevated temperature, the α → γ structural martensitic transformation in the FeCoNi ternary alloys occurred due to the inhomogeneities in composition of the matrix during annealing of the alloy with metastable α-phase. In the Si/Al-added FeCoNi nanofibers, more than two phases with complicated-boundaries of the grains in and/or outside the nanofibers were formed as crystalline phases and amorphous phase. The amorphous phase consisted of Si and/or Al acted as an inhibitor diminishing α → γ transformation as well as an interparticle insulation layer. At low annealing temperature of 450 °C, the Si/Al-added nanofiber mainly consisted of metastable α-phase with a low-crystallinity surface structure and very small diameter of 13 nm was formed and showed an unexpectedly high coercivity, which attributed to the surface effects and/or high surface/volume ratio.

  13. Magnetic and mineralogical properties of salt rocks from the Zechstein of the Northern German Basin

    NASA Astrophysics Data System (ADS)

    Heinrich, Frances C.; Schmidt, Volkmar; Schramm, Michael; Mertineit, Michael

    2017-01-01

    Magnetic properties of rocks are often studied to characterize composition and fabric of rocks. For salt rocks, the basic relationships between their magnetic properties and composition, which are necessary to interpret rock magnetic data, are not yet established. Therefore, we studied different types of natural salt rock and pure salt minerals. We measured their magnetic properties (magnetic susceptibility, IRM acquisition curves, FORC diagrams, temperature-dependent magnetic susceptibility) and used analytical methods such as microscopy, XRD and ICP-OES to understand the relationship between magnetic properties and mineralogy. Salt rocks mainly consist of the diamagnetic minerals halite, carnallite, sylvine and anhydrite with negative magnetic susceptibilities. The magnetic susceptibilities of pure synthetic NaCl and KCl single crystals, show values of -14.5 × 10-6 SI and -13.5 × 10-6 SI, respectively. In contrast, in natural salt rocks higher magnetic susceptibility values were measured. The magnetic susceptibility of the samples investigated in this study shows a general increase from light rock salt (max. -10 × 10-6 SI) over carnallitite (max. 134 × 10-6 SI) to red sylvinite (max. 270 × 10-6 SI). Whole rock analyses suggests that increased magnetic susceptibility can be attributed to paramagnetic and ferromagnetic minerals that are contained within the insoluble residue. The magnetic susceptibility is mainly controlled by magnetite and phyllosilicates. Its measurement can therefore be used to detect subtle changes in the content of these minerals.

  14. Tuning microstructure and magnetic properties of electrodeposited CoNiP films by high magnetic field annealing

    NASA Astrophysics Data System (ADS)

    Wu, Chun; Wang, Kai; Li, Donggang; Lou, Changsheng; Zhao, Yue; Gao, Yang; Wang, Qiang

    2016-10-01

    A high magnetic field (up to 12 T) has been used to anneal 2.6-μm-thick Co50Ni40P10 films formed by pulse electrodeposition. The effects of high magnetic field annealing on the microstructure and magnetic properties of CoNiP thin films have been investigated. It was found that a high magnetic field accelerated a phase transformation from fcc to hcp and enhanced the preferred hcp-(002) orientation during annealing. Compared with the films annealed without a magnetic field, annealing at 12 T decreased the surface particle size, roughness, and coercivity, but increased the saturation magnetization and remanent magnetization of CoNiP films. The out-of-plane coercivity was higher than that the in-plane for the as-deposited films. After annealing without a magnetic field, the out-of-plane coercivity was equal to that of the in-plane. However, the out-of-plane coercivity was higher than that of the in-plane when annealing at 12 T. These results indicate that high magnetic field annealing is an effective method for tuning the microstructure and magnetic properties of thin films.

  15. Magnetic Properties of Hydrothermalized A-type Red Granites

    NASA Astrophysics Data System (ADS)

    Trindade, R. I. F.; Nédélec, A.; Peschler, A.; Archanjo, C. J.; Poitrasson, F.; Bouchez, J. L.

    Hydrothermalized A-type granites are commonly identified by their pink to red-brick colour attributed to tiny flakes of hematite in the alkali feldspars. These inclusions can be of interest in magnetic studies, but their timing and process of formation are still unclear. Formation of chlorite after biotite is the commonest effect of hydrother- malization and may occur quite early after crystallization due to late-magmatic or externally-derived fluids. The reddish colour appears at a later stage. Five cases of A-type granites were investigated for their magnetic mineralogy and properties. The selected cases range from nearly unmodified granites (Panafrican stratoid granites of Madagascar) to strongly hydrothermalized ones (Meruoca, Brazil; Tana, Corsica); in- termediate cases are : Mount Scott (Oklahoma), Bushveld (granitic core kindly pro- vided by R.G. Cawthorn) and. Hydrothermal alteration is often associated to a de- crease of the magnetic susceptibility magnitude (K) and of the anisotropy degree (P). It also strongly affects the rockt's bulk coercivity parameters, since alteration changes the relative amounts of coarse-grained primary magnetite, fine-grained PSD to SD sec- ondary magnetite, and hematite. Correspondingly, most samples plot away from the magnetite trend in the Dayt's diagram, but the different groups identified after coer- civity parameters do not directly correlate with whole-rock colour. In addition, IRM- acquisition curves and thermal demagnetization of tri-axial IRM show that hematite occurs in almost all analysed samples despite their colour. Various hematite coercivity ranges are also evidenced. In fact, hematite can be formed either in feldspar crys- tals or after magnetite. Tiny hematite within feldspars can appear either by exsolu- tion process or, more likely, by precipitation from a fluid phase. For these reasons, hematite inclusions may carry a remanence acquired shortly after granite crystalliza- tion or, conversely, a recent

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

    PubMed Central

    Kleibert, Armin; Rosellen, Wolfgang; Getzlaff, Mathias

    2011-01-01

    not strained. Thus, strain is most likely not the origin of the enhanced orbital moments as supposed before. Moreover, RHEED uncovers the existence of a spontaneous process for epitaxial alignment of particles below a critical size of about 4 nm. STM basically confirms the shape conservation of the larger particles but shows first indications for an unexpected reshaping occurring at the onset of self-alignment. Conclusion: The magnetic and structural properties of nanoparticles are strongly affected by the deposition kinetics even when soft landing conditions are provided. The orientation of the deposited particles and thus their interface with the substrate strongly depend on the particle size with consequences regarding particularly the magnetic behavior. Spontaneous and epitaxial self-alignment can occur below a certain critical size. This may enable the obtainment of samples with controlled, uniform interfaces and crystallographic orientations even in a random deposition process. However, such a reorientation process might be accompanied by a complex reshaping of the particles. PMID:21977415

  17. Microstructure and Magnetic Properties of Electrodeposited Cobalt Film

    SciTech Connect

    Bhuiyan, Md S; Taylor, B. J.; Paranthaman, Mariappan Parans; Thompson, James R; Sinclair, J.

    2008-01-01

    Cobalt films were electrodeposited onto both iron and copper substrates from an aqueous solution containing a mixture of cobalt sulfate, boric acid, sodium citrate, and vanadyl sulfate. The structural, intermetallic diffusion and magnetic properties of the electrodeposited films were studied. Cobalt electrodeposition was carried out in a passively divided cell aided by addition of vanadyl sulfate to keep the counter electrode clean. The divided electrolytic cell with very negative current densities cause the electrodeposited Co to adopt a face-centered cubic (fcc) structure, which is more magnetically reversible than the hexagonally close-packed (hcp) structured Co. The coercive field is also significantly less in the fcc-electrodeposited cobalt than in the hcp. SEM images show dense, uniform Co films without any cracks or porosity. Beside the deposition current, thickness of the film was also found to affect the crystal orientation particularly on iron substrates. Diffusion of cobalt film into the iron substrate was studied under reduced environment and a fast process was observed.

  18. FeNi-based magnetic layered nanostructures: Magnetic properties and giant magnetoimpedance

    NASA Astrophysics Data System (ADS)

    Kurlyandskaya, G. V.; Svalov, A. V.; Fernandez, E.; Garcia-Arribas, A.; Barandiaran, J. M.

    2010-05-01

    Magnetic properties and the magnetoimpedance (MI) effect were studied for a series of [Fe20Ni80/Ti]n/Fe20Ni80 (n=0 to 5) nanostructures, prepared by dc magnetron sputtering. The thickness of the FeNi layers was selected as 170 nm in order to avoid the appearance of the "transcritical" state that takes place for thicker layers. First, the influence of the Ti layer thickness was determined for n=1 trilayers, with Ti layers ranging from 2 to 20 nm. The minimum coercivity corresponded to a Ti layer of about 6 nm. Second, the magnetic properties and MI responses were studied for different [FeNi/Ti]n/FeNi structures at a fixed Ti layer thickness of 6 nm. The complex impedance was measured for a frequency range of 1-300 MHz. The highest value of the MI was obtained in the sample [FeNi/Ti]5/FeNi with the largest total thickness.

  19. Magnetic nanoparticles for power absorption: Optimizing size, shape and magnetic properties

    SciTech Connect

    Gonzalez-Fernandez, M.A.; Torres, T.E.; Andres-Verges, M.; Costo, R.; Presa, P. de la; Serna, C.J.; Morales, M.P.; Marquina, C.; Ibarra, M.R.; Goya, G.F.

    2009-10-15

    We present a study on the magnetic properties of naked and silica-coated Fe{sub 3}O{sub 4} nanoparticles with sizes between 5 and 110 nm. Their efficiency as heating agents was assessed through specific power absorption (SPA) measurements as a function of particle size and shape. The results show a strong dependence of the SPA with the particle size, with a maximum around 30 nm, as expected for a Neel relaxation mechanism in single-domain particles. The SiO{sub 2} shell thickness was found to play an important role in the SPA mechanism by hindering the heat outflow, thus decreasing the heating efficiency. It is concluded that a compromise between good heating efficiency and surface functionality for biomedical purposes can be attained by making the SiO{sub 2} functional coating as thin as possible. - Graphical Abstract: The magnetic properties of Fe{sub 3}O{sub 4} nanoparticles from 5 to 110 nm are presented, and their efficiency as heating agents discussed as a function of particle size, shape and surface functionalization.

  20. Magnetic properties of Co Cu nanoparticles dispersed in silica matrix

    NASA Astrophysics Data System (ADS)

    de Julián Fernández, C.; Mattei, G.; Maurizio, C.; Cattaruzza, E.; Padovani, S.; Battaglin, G.; Gonella, F.; D'Acapito, F.; Mazzoldi, P.

    2005-04-01

    The magnetic properties of Co-Cu/silica nanocomposites prepared by sequential ion implantation have been investigated. The nanostructure is formed of 4 nm average size particles dispersed in silica matrix and with mainly FCC structure. The hysteresis loops at 3 K indicate that the nanoparticles have uniaxial anisotropy with values smaller than that of single Cobalt implants. The samples are characterized by a superparamagnetic behavior with blocking temperatures that depend on the Co/Cu implanted ratio, and the blocking temperature distributions are narrower than those obtained by taking into account only the particle size distribution. Results are discussed considering size effects and that the nanoparticles are formed of a Co-Cu solid solution or only of Co.

  1. Exchange-Coupling in Magnetic Nanoparticles to Enhance Magnetostrictive Properties

    SciTech Connect

    Radousky, H; McElfresh, M; Berkowitz, A; Carman, G P

    2002-01-31

    Spark erosion is a versatile and economical method for producing particles of virtually any type of material that has a nominal conductivity: particles can be prepared in sizes ranging from a few nm to tens of {micro}m. The purpose of this feasibility study was to demonstrate the capability of making spherical particles of specific magnetic materials. We chose (Tb Dy)Fe{sub 2} (Terfenol-D) due to its potential use as the magnetostrictive component in magneto-elastomer composites. We also chose to work with pure Ni as a model system. Improvements in the properties of magneto-elastomer composites have broad applications in the areas of sensor development, enhanced actuators and damping systems.

  2. Temperature-sensitive hybrid microgels with magnetic properties.

    PubMed

    Pich, Andrij; Bhattacharya, Sanchita; Lu, Yan; Boyko, Volodymyr; Adler, Hans-Juergen P

    2004-11-23

    In the present paper, we report the preparation of hybrid temperature-sensitive microgels which include magnetite nanoparticles in their structure. Polymeric microgels have been prepared by surfactant-free emulsion copolymerization of acetoacetoxyethyl methacrylate (AAEM) and N-vinylcaprolactam (VCL) in water with a water-soluble azo-initiator. The obtained microgels possess a low critical solution temperature (LCST) in water solutions, with a rapid decrease of the particle size being observed at elevated temperatures. Magnetite was deposited directly into microgels, leading to the formation of composite particles which combine both temperature-sensitive and magnetic properties. The influence of magnetite load on microgel size, morphology, swelling-deswelling behavior, and stability is discussed.

  3. Magnetic Properties of W-Type Hexaferrite Powders

    NASA Astrophysics Data System (ADS)

    Kojima, Hiroshi; Miyakawa, Choji; Sato, Takafumi; Goto, Kimiyoshi

    1985-01-01

    An investigation was undertaken to elucidate the preparation conditions and magnetic properties of W-type hexaferrite powders with the formula AM2Fe16O27 (A=Ba or Sr, M=Fe2+, Zn+Cu, Zn+Cd, Zn+Mg). A pure W-phase was formed by firing a mixture of carbonates and oxides in the appropriate molar ratio at 1200°˜1400°C in an atmosphere of PO2/(PO2+PN2){=}10-2˜ 10-6 or in air. The values σs{=}70˜ 79 emu/g, Hc{=}400˜ 2000 Oe, σr/σs˜ 0.90 and Tc{=}350°˜500°C were obtained for the oxide powders, aligned along the c axis.

  4. Magnetic properties of Pm in NdNi

    SciTech Connect

    Nishimura, K.; Mori, K.; Ohya, S.; Muto, S.; Isikawa, Y.

    1996-06-01

    Magnetic properties of Pm as an impurity in NdNi single crystal were investigated by means of low-temperature nuclear orientation of the {sup 144}Pm isotope. The angular distribution of {gamma}-ray anisotropy revealed that the direction of the hyperfine field experienced by the nuclei was in the ({ital a},{ital c}) plane and made an angle of 29(10){degree} and/or 209(10){degree} with the {ital a} axis. The strength of the field was deduced to be 395(48) T with a full-field site fraction of 76(3){percent} from the temperature dependence of the anisotropy. The {beta} decay of {sup 144}Pm was found to proceed mainly via the {Delta}{ital J}{sub {beta}}=1 matrix element. A brief discussion of crystal electric field effects and exchange interactions is given. {copyright} {ital 1996 The American Physical Society.}

  5. Electrical properties and magnetic response of cobalt germanosilicide nanowires.

    PubMed

    Tsai, Chun-I; Wang, Chiu-Yen; Tang, Jianshi; Hung, Min-Hsiu; Wang, Kang L; Chen, Lih-Juann

    2011-12-27

    The effects of partial substitution of Ge for Si in cobalt germanosilicide (CoSi(1-x)Ge(x) and Co(2)Si(1-x)Ge(x)) nanowires (NWs) on the electrical transport, magnetic properties, and magnetoresistance (MR) have been investigated. Cobalt germanosilicide NWs were synthesized by a spontaneous chemical vapor transport growth method. The Ge concentration can be selectively controlled from 0 to 15% and 0-50% for CoSi(1-x)Ge(x) and Co(2)Si(1-x)Ge(x) NWs, respectively, by varying the reaction temperature. Electrical measurements showed that the resistivities of CoSi(1-x)Ge(x) NWs are 90, 60, 30, and 23 μΩ-cm for x = 0, 0.01, 0.05, and 0.15, respectively. Therefore, the electrical resistivity of CoSi(1-x)Ge(x) NWs was found to decrease significantly with an increasing Ge concentration, which is believed to be a result of the band gap narrowing. On the other hand, the Co(2)Si(1-x)Ge(x) (x ≤ 0.5) NWs exhibited ferromagnetism at 300 K, which is attributed to the uncoordinated Co atoms on the NW surface and spin-glass behavior at low temperature. The highest MR response of Co(2)Si(1-x)Ge(x) NWs occurred at x = 0.5, where a MR ratio of 11.7% can be obtained at 10-25 K with a magnetic field of 8 T. The enhanced physical properties of cobalt germanosilicide NWs with Ge substitution shall lead to promising application in the fabrication of nanodevices, including spintronics and serving as the gate and interconnect material.

  6. Magnetic properties of Mn1-xAl1-yNi alloys in the B2 (CsCl-type) structure

    NASA Astrophysics Data System (ADS)

    Paduani, C.; Schaf, J.; Ardisson, J. D.; Takeuchi, A. Y.

    2010-02-01

    In this work is investigated structural and magnetic properties of ferromagnetic Mn1-xAl1-yNi alloys in the κ phase which has a B2 (CsCl-type) structure. The Curie temperatures are above room temperature and decrease with the substitution of Ni for Mn. The magnetic measurements indicate the existence of ferrimagnetism originated from Mn atoms which carry unequal and opposite magnetic moments in different sublattices. A larger average magnetic moment is observed in the Ni-doped system, as compared to the Fe-system, which is due to the formation of larger moment on Mn atoms at the cube corners.

  7. Effect of Soft Phase on Magnetic Properties of Bulk Sm-Co/alpha-Fe Nanocomposite Magnets (Postprint)

    DTIC Science & Technology

    2012-11-01

    plasma sintering , and warm compaction [4][5]–[9]. In our previous study [10], bulk Sm–Co –Fe nanocomposite magnets were fabricated by hot pressing of...no. 5, pp. 2974–2976, Jul. 2003. [8] T. Saito and H. Miyoshi, “Magnetic properties of Sm5Fe17/Fe com- posite magnets produces by spark plasma ...Fe and Fe-Co. Bulk composite magnets have been prepared using compaction techniques such as hot pressing/deforma- tion, dynamic shock compaction, spark

  8. Correlation Between Domain Behavior and Magnetic Properties of Materials

    SciTech Connect

    Leib, Jeffrey Scott

    2003-01-01

    Correlation between length scales in the field of magnetism has long been a topic of intensive study. The long-term desire is simple: to determine one theory that completely describes the magnetic behavior of matter from an individual atomic particle all the way up to large masses of material. One key piece to this puzzle is connecting the behavior of a material's domains on the nanometer scale with the magnetic properties of an entire large sample or device on the centimeter scale. In the first case study involving the FeSiAl thin films, contrast and spacing of domain patterns are clearly related to microstructure and stress. Case study 2 most clearly demonstrates localized, incoherent domain wall motion switching with field applied along an easy axis for a square hysteresis loop. In case study 3, axis-specific images of the complex Gd-Si-Ge material clearly show the influence of uniaxial anisotropy. Case study 4, the only study with the sole intent of creating domain structures for imaging, also demonstrated in fairly simple terms the effects of increasing stress on domain patterns. In case study 5, it was proven that the width of magnetoresistance loops could be quantitatively predicted using only MFM. When all of the case studies are considered together, a dominating factor seems to be that of anisotropy, both magneticrostaylline and stress induced. Any quantitative bulk measurements heavily reliant on K coefficients, such as the saturation fields for the FeSiAl films, Hc in cases 1, 3, and 5, and the uniaxial character of the Gd5(Si2Ge2), transferred to and from the domain scale quite well. In-situ measurements of domain rotation and switching, could also be strongly correlated with bulk magnetic properties, including coercivity, Ms, and hysteresis loop shape. In most cases, the qualitative nature of the domain structures, when properly considered, matched quite well to what might have been expected from

  9. Evaluating the influence of residual stresses on the magnetic properties of electrical steel

    SciTech Connect

    Korzunin, G.S.; Chistyakov, V.K.

    1995-04-01

    The method described for evaluating the influence of residual stresses on the magnetic properties of coiled cold-rolled electrical steel consists in measuring the ratio of the magnetic characteristics that are and are not sensitive to the effect of residual stresses. The evaluation is made from the value of the ratio, using the correlations between its value and the magnetic characteristics studied.

  10. Magnetic properties of nearly stoichiometric CeAuBi{sub 2} heavy fermion compound

    SciTech Connect

    Adriano, C.; Jesus, C. B. R.; Pagliuso, P. G.; Rosa, P. F. S.; Grant, T.; Fisk, Z.; Garcia, D. J.

    2015-05-07

    Motivated by the interesting magnetic anisotropy found in the heavy fermion family CeTX{sub 2} (T = transition metal and X = pnictogen), here, we study the novel parent compound CeAu{sub 1−x}Bi{sub 2−y} by combining magnetization, pressure dependent electrical resistivity, and heat-capacity measurements. The magnetic properties of our nearly stoichiometric single crystal sample of CeAu{sub 1−x}Bi{sub 2−y} (x = 0.92 and y = 1.6) revealed an antiferromagnetic ordering at T{sub N} = 12 K with an easy axis along the c-direction. The field dependent magnetization data at low temperatures reveal the existence of a spin-flop transition when the field is applied along the c-axis (H{sub c} ∼ 7.5 T and T = 5 K). The heat capacity and pressure dependent resistivity data suggest that CeAu{sub 0.92}Bi{sub 1.6} exhibits a weak heavy fermion behavior with strongly localized Ce{sup 3+} 4f electrons. Furthermore, the systematic analysis using a mean field model including anisotropic nearest-neighbors interactions and the tetragonal crystalline electric field (CEF) Hamiltonian allows us to extract a CEF scheme and two different values for the anisotropic J{sub RKKY} exchange parameters between the Ce{sup 3+} ions in this compound. Thus, we discuss a scenario, considering both the anisotropic magnetic interactions and the tetragonal CEF effects, in the CeAu{sub 1−x}Bi{sub 2−y} compounds, and we compare our results with the isostructural compound CeCuBi{sub 2}.

  11. The relationship between microstructure and magnetic properties in high-energy permanent magnets characterized by polytwinned structures

    NASA Astrophysics Data System (ADS)

    This report summarizes the results of a study of the relationship between microstructure and magnetic properties in a unique genre of ferromagnetic material characterized by a polysynthetically twinned structure which arises during solid state transformation. These results stem from the work over a period of approximately 27 months of a nominal 3 year grant period. The report also contains a proposal to extend the research project for an additional 3 years. The polytwinned structures produce an inhomogeneous magnetic medium in which the easy axis of magnetization varies quasi-periodically giving rise to special domain configurations which are expected to markedly influence the mechanism of magnetization reversal and hysteresis behavior of these materials in bulk or thin films. The extraordinary permanent magnet properties exhibited by the well-known Co-Pt alloys as well as the Fe-Pt and Fe-Pd systems near the equiatomic composition derive from the formation of a polytwinned microstructure.

  12. Magnetic properties and structures of fibrous R11Ni4In9 intermetallics (R = heavy rare earths)

    NASA Astrophysics Data System (ADS)

    Provino, Alessia; Ritter, Clemens; Gschneidner, Karl A.; Manfrinetti, Pietro; Dhar, Sudesh K.; Pecharsky, Vitalij K.

    2015-03-01

    The existence and the unusual self-assembled nano/microfibrous morphology of the R11T4In9 (R = rare earth, T = Ni, Pd, Pt) phases has been recently studied [1,2,3]. All the rare earths (but Sc, Eu, Yb) form this ternary compound (orthorhombic Nd11Pd4In9-type, oC48, Cmmm). The bundles of fibers grow parallel to the temperature gradient and along the short c-axis. In this presentation we describe the results of a detailed investigation of the physical properties (electrical resistivity, heat capacity, magnetization measurements) of Tb11Ni4In9, Dy11Ni4In9andHo11Ni4In9 by orienting the fibers parallel and orthogonal, respectively, to the electric current and magnetic field. The unusual fibrous microstructure of these compounds leads to a strong anisotropy in their physical properties, with the c-axis of the orthorhombic cell being the easy magnetization and high electrical-conductivity direction. The magnetic structures of Tb11Ni4In9andHo11Ni4In9, which have multiple magnetic orderings, have been investigated by neutron diffraction. The complex magnetic behavior found in these phases is a result of the competing ferrimagnetic (along the c-axis) and antiferromagnetic (on the a - b plane) orderings of the five R sublattices.

  13. Magnetic and magnetocaloric properties of amorphous Y3Fe5O12 compound

    NASA Astrophysics Data System (ADS)

    Nóbrega, E. P.; Costa, S. S.; Alvarenga, T. S. T.; Alho, B. P.; Caldas, A.; Ribeiro, P. O.; de Sousa, V. S. R.; de Oliveira, N. A.; von Ranke, P. J.

    2017-01-01

    We report a theoretical model formed by two coupled magnetic sublattices of localized spins in the presence of an applied magnetic field to investigate the magnetic characteristics and magnetocaloric properties of amorphous yttrium iron garnet. The magnetic state equation is based on Handrich-Kobe´s theory, where the amorphization is taken into account by introducing fluctuations in the exchange parameters. Experimental results report that Y3Fe5O12 presents a structural phase transition from crystalline to amorphous caused by a variation of external pressure. This phase transition on Y3Fe5O12 leads to interesting results in the magnetic properties and magnetocaloric quantities.

  14. Intrinsic ferromagnetic properties in Cr-doped ZnO diluted magnetic semiconductors

    SciTech Connect

    Liu Yang; Yang Yanting; Yang Jinghai; Guan Qingfeng; Liu Huilian; Yang Lili; Zhang Yongjun; Wang Yaxin; Wei Maobin; Liu Xiaoyan; Fei Lianhua; Cheng Xin

    2011-05-15

    The Cr-doped zinc oxide (Zn{sub 1-x}Cr{sub x}O, 0{<=}x{<=}0.08) diluted magnetic semiconductors have been synthesized successfully by the sol-gel method. Investigations on magnetic, optical and structural properties of the produced samples have been done. Energy dispersive spectroscopy (EDS) shows the existence of Cr ion in the Cr-doped ZnO. The results of X-ray diffraction (XRD), the transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) indicate that the Cr ions are at least partially substitutionally incorporated into the crystal lattice of ZnO. The produced samples show good high-T{sub c} (Curie temperature) ferromagnetism (FM) in Cr-doped ZnO nanoparticles with Cr concentration of less than 5 at%. The results of photoluminescence (PL) further testify that FM is an intrinsic property of the Cr-doped ZnO nanoparticles. And the occurrence of FM should mainly contribute to the Cr doping. -- Graphical Abstract: As can be seen from the magnetic hysteresis loops of Zn{sub 1-x}Cr{sub x}O (x=0.01, 0.03, 0.05, and 0.08) at room temperature under 10 KOe, the samples show good high-T{sub c} ferromagnetism with Cr concentration of less than 5 at%. Display Omitted Highlights: {yields} Zn{sub 1-x}Cr{sub x}O(0{<=}x{<=}0.08) nanoparticles are successfully synthesized by sol-gel method. {yields} The Cr ions are substitutionally incorporated into the crystal lattice of ZnO. {yields} The Cr-doped ZnO nanoparticles show good high-T{sub c} ferromagnetism. {yields} The ferromagnetism is an intrinsic property of the Cr-doped ZnO nanoparticles.

  15. The magnetic and chemical structural property of the epitaxially-grown multilayered thin film

    NASA Astrophysics Data System (ADS)

    Lee, Hwachol

    L10 FePt- and Fe-related alloys such as FePtRh, FeRh and FeRhPd have been studied for the high magnetocrystalline anisotropy and magnetic phase transition property for the future application. In this work, the thin film structural and magnetic property is investigated for the selected FePtRh and FeRhPd alloys. The compositionally-modulated L10 FePtRh multilayered structure is grown epitaxially on a-plane Al2O3 with Cr and Pt buffer layer at 600degC growth temperature by DC sputtering technique and examined for the structural, interfacial and magnetic property. For the epitaxially grown L10 [Fe50Pt45Rh5 (FM) (10nm) / Fe50Pt25Rh25 (AFM) (20nm)]x8 superlattice, the magnetically and chemically sharp interface formation between layers was observed in X-ray diffraction, transmission electron microscopy and polarized neutron reflectivity measurements with the negligible exchange bias at room and a slight coupling effect at lower temperature regime. For FeRhPd, the magnetic phase transition of epitaxially-grown 111-oriented Fe46Rh48Pd6 thin film is studied. The applied Rhodium buffer layer on a-plane Al2O3 (11 20) at 600degC shows the extraordinarily high quality of epitaxial film in (111) orientation, where two broad and coherent peak in rocking curve, and Laue oscillations are observed. The epitaxially-grown Pd-doped FeRh on Pt (111) grown at 600degC, 700degC exhibits the co-existing stable L10 (111) and B2 (110) structures and magnetic phase transition around 300degC. On the other hand, the partially-ordered FeRhPd structure grown at 400degC, 500degC shows background high ferromagnetic state over 5K˜350K temperature. For the reduced thickness of Fe46Rh48Pd 6, the ferromagnetic state becomes dominant with a reduced portion of the film undergoing a magnetic phase transition. For some epitaxial FeRhPd film, the spin-glass-like disordered state is also observed in field dependent SQUID measurement. For the tri-layered FeRhPd with thin Pt spacer, the background

  16. Magnetic Property Measurements on Single Wall Carbon Nanotube-Polyimide Composites

    NASA Technical Reports Server (NTRS)

    Sun, Keun J.; Wincheski, Russell A.; Park, Cheol

    2008-01-01

    Temperature and magnetic field dependent magnetization measurements were performed on polyimide nanocomposite samples, synthesized with various weight percentages of single wall carbon nanotubes. It was found that the magnetization of the composite, normalized to the mass of nanotube material in the sample, decreased with increasing weight percentage of nanotubes. It is possible that the interfacial coupling between the carbon nanotube (CNT) fillers and the polyimide matrix promotes the diamagnetic response from CNTs and reduces the total magnetization of the composite. The coercivity of the samples, believed to originate from the residual magnetic catalyst particles, was enhanced and had a stronger temperature dependence as a result of the composite synthesis. These changes in magnetic properties can form the basis of a new approach to investigate the interfacial properties in the CNT nanocomposites through magnetic property measurements.

  17. Magnetorheological and deformation properties of magnetically controlled elastomers with hard magnetic filler

    NASA Astrophysics Data System (ADS)

    Stepanov, G. V.; Chertovich, A. V.; Kramarenko, E. Yu.

    2012-10-01

    Viscoelastic and deformational behavior of soft magnetic elastomers with hard magnetic fillers under the influence of a magnetic field is studied by different experimental techniques. The magnetic elastomers used in this work were synthesized on the basis of silicone rubber filled with FeNdB particles and were magnetized in a field of 3 and 15 kOe. We have shown that due to high residual magnetization the materials demonstrate well pronounced non-elastic behavior already in the absence of any external magnetic field. In particular, in contrast to magnetic elastomers based on soft magnetic fillers their elastic modulus is strain-dependent. Under the influence of external magnetic field the storage and loss moduli of magnetic elastomers with hard magnetic filler can both increase and decrease tremendously.

  18. Electronic, magnetic and topological properties of transition metal oxides

    NASA Astrophysics Data System (ADS)

    Quan, Yundi

    Transition metal oxides have been the ideal platform for designing materials with exotic properties due to the complex interplay between spin, charge, and orbital degrees of freedom which can be fine-tuned by varying pressure, temperature, and external magnetic field to give rise to novel phases. Transition metal oxides are also a challenge from the theoretical point of view. The (semi)local density approximation for the exchange correlation functional that is often used in density functional calculations fails to adequately describe the many-body effects of 3d and 4f electrons thereby leading to underestimated band gaps. Several techniques, such as hybrid functionals, dynamical mean field theory, and DFT+U, have been developed over the past few decades to account for the many-body effects of 3d and 4f electrons. The DFT+U method, which will be used extensively throughout this thesis, has proved to be very successful in modeling gap opening, structure optimization and predicting transport properties. Rare earth nickelates have attracted a lot of attention in recent years due to their complex phase diagram that arises from the competition between spin, charge, and orbital degrees of freedom. Of particular interest is the metal-insulator transition that occurs upon cooling for RNiO3 (R=rare earth, except for La) which was found to be accompanied by symmetry lowering, later theorized as the evidence for charge ordering. By using first principles calculations, we found that the charge difference between Ni ions in the "charge-ordered" phase is negligibly small, while various aspects such as core energy levels, spectral weight immediately above and below the Fermi level, and magnetic moments do differ. Using Wannier function analysis, the charge states of Ni ions in the lower symmetry structure are systematically studied and found to correlated to the number of Wannier charge centers at the Ni site. The same approach was applied to study the charge states of Ag I and Ag

  19. Effects of wear on structure-sensitive magnetic properties of ceramic ferrite in contact with magnetic tape

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.; Tanaka, K.

    1985-01-01

    Wear experiments and electron microscopy and diffraction studies were conducted to examine the wear and deformed layers in single-crystal Mn-Zn (ceramic) ferrite magnetic head material in contact with magnetic tape and the effects of that contact on magnetic properties. The crystalline state of the single-crystal magnetic head was changed drastically during the sliding process. A nearly amorphous structure was produced on its wear surface. Deformation in the surficial layer of the magnetic head was a critical factor in readback signal loss above 2.5 dB. The signal output level was reduced as applied normal load was increased. Considerable plastic flow occurred on the magnetic tape surface with sliding, and the signal loss due to the tape wear was approximately 1 dB.

  20. Magnetic properties of Dy2Ti2O7

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1973-01-01

    Measurements were made of the magnetization, differential magnetic susceptibility, and magnetic entropy of powered samples of Dy2Ti2O7. The saturation magnetic moment is 4.7 + or - 0.2 Bohr magnetons per Dy ion, instead of 10 as predicted by Hund's rules. A temperature-independent magnetization is observed in the saturation region. Absolute values of magnetic entropy have been obtained for temperatures from 1.25 to 20 K, in applied fields up to 10.4 tesla. The magnetic entropy approaches a maximum value consistent with a ground-state multiplicity of 2. Low field magnetization and differential susceptibility data show a transition to antiferromagnetism near 1.35 K. A construction of the magnetic specific heat from the zero field entropy shows an anomaly near the same temperature.

  1. Structural and magnetic properties of self assembled Fe-doped Cu{sub 2}O nanorods

    SciTech Connect

    Ahmed, Asar; Gajbhiye, Namdeo S.; Kurian, S.

    2010-09-15

    Cuprous oxide (Cu{sub 2}O) nanorods doped with iron impurities have been synthesized by the polyol method using sodium dodecyl sulfate as the surfactant. The X-ray diffraction measurement reveals the pure phase of simple cubic Cu{sub 2}O and the electron microscopy displays its one dimensional morphology. Ferromagnetism was observed at room temperature in the magnetic measurements of the doped samples while undoped sample exhibits only diamagnetism. Room temperature Moessbauer spectra for the samples exhibited only doublets but no sextet, which corresponds to the presence of paramagnetic iron sites. As magnetic moment contribution of the doped ions was insignificant for the observed magnetism, ferromagnetic property in the doped samples could have been originated from the defects as cation vacancies. Existence of the defects was supported by the room temperature photoluminescence spectra of the doped samples in reference to the undoped sample. - Ferromagnetism at room temperature was observed in the Fe doped Cu{sub 2}O nanorods. The origin seems to be the defects of cation vacancies created by the dopant ions.

  2. Magnetic properties of a Kramers doublet. An univocal bridge between experimental results and theoretical predictions.

    PubMed

    Alonso, P J; Martínez, J I

    2015-06-01

    The magnetic response of a Kramers doublet is analyzed in a general case taking into account only the formal properties derived from time reversal operation. It leads to a definition of a matrix G (gyromagnetic matrix) whose expression depends on the chosen reference frame and on the Kramers conjugate basis used to describe the physical system. It is shown that there exists a reference frame and a suitable Kramers conjugate basis that gives a diagonal form for the G-matrix with all non-null elements having the same sign. A detailed procedure for obtaining this canonical expression of G is presented when the electronic structure of the KD is known regardless the level of the used theory. This procedure provides a univocal way to compare the theoretical predictions with the experimental results obtained from a complete set of magnetic experiments. In this way the problems arising from ambiguities in the g-tensor definition are overcome. This procedure is extended to find a spin-Hamiltonian suitable for describing the magnetic behavior of a pair of weakly coupled Kramers systems in the multispin scheme when the interaction between the two moieties as well as the individual Zeeman interaction are small enough as compared with ligand field splitting. Explicit relations between the physical interaction and the parameters of such a spin-Hamiltonian are also obtained.

  3. Endowing carbon nanotubes with superparamagnetic properties: applications for cell labeling, MRI cell tracking and magnetic manipulations.

    PubMed

    Lamanna, Giuseppe; Garofalo, Antonio; Popa, Gabriela; Wilhelm, Claire; Bégin-Colin, Sylvie; Felder-Flesch, Delphine; Bianco, Alberto; Gazeau, Florence; Ménard-Moyon, Cécilia

    2013-05-21

    Coating of carbon nanotubes (CNTs) with magnetic nanoparticles (NPs) imparts novel magnetic, optical, and thermal properties with potential applications in the biomedical domain. Multi-walled CNTs have been decorated with iron oxide superparamagnetic NPs. Two different approaches have been investigated based on ligand exchange or "click chemistry". The presence of the NPs on the nanotube surface allows conferring magnetic properties to CNTs. We have evaluated the potential of the NP/CNT hybrids as a contrast agent for magnetic resonance imaging (MRI) and their interactions with cells. The capacity of the hybrids to magnetically monitor and manipulate cells has also been investigated. The NP/CNTs can be manipulated by a remote magnetic field with enhanced contrast in MRI. They are internalized into tumor cells without showing cytotoxicity. The labeled cells can be magnetically manipulated as they display magnetic mobility and are detected at a single cell level through high resolution MRI.

  4. Syntheses, structure, magnetic and thermodynamics property of novel lanthanide complexes with nitronyl nitroxide radical

    NASA Astrophysics Data System (ADS)

    Song, Mei-Ying; Hou, Yi-Fang; Wen, Long-Mei; Wang, Shu-Ping; Yang, Shu-Tao; Zhang, Jian-Jun; Geng, Li-Na; Shi, Shi-Kao

    2016-03-01

    Four new nitronyl nitroxide radical-Ln(III) complexes, Ln(hfac)3(NITPhSCF3)2 (Ln(III) = Sm(1), Gd(2), Tb(3), Dy(4); NITPhSCF3 = 2-(4-trifluoromethylthiophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl- 3-oxide; hfac = hexafluoroacetylacetonate), have been synthesized and characterized. They are isostructural, which show mononuclear tri-spin structures. The central Ln(III) ion is eight-coordinated by three hfac anions and two NITPhSCF3 molecules. Direct-current magnetic study shows that there exist ferromagnetic interactions between Gd(III) ion and radicals (NITPhSCF3) with JGd-Rad = 1.61 cm-1, and antiferromagnetic interactions between radicals with JRad-Rad = -2.83 cm-1 in complex 2. The magnetic analysis with the rough approximate model show that a ferromagnetic coupling exists between Tb(III) and radical in 3, while a antiferromagnetic coupling between Dy(III) and radical in 4. The thermodynamics properties of four complexes were studied with differential scanning calorimetry (DSC), such as heat capacity, thermodynamic functions (HT-H298.15K), (ST-S298.15K), and (GT-G298.15K).

  5. Magnetic Properties of Lunar Samples: an Exhaustive Survey of the Apollo Collection

    NASA Astrophysics Data System (ADS)

    Gattacceca, J.; Andrade Lima, E.; Rochette, P.; Weiss, B. P.; Uehara, M.; Quesnel, Y.; Baratchart, L.; Leblond, J.; Chevillard, S.

    2014-12-01

    Detailed paleomagnetic studies of lunar samples shed light on the existence and timing of the ancient lunar dynamo, with insights to the inner structure and thermal evolution of the Moon, as well as constraints for the lunar dynamo models [e.g., 1-6]. However these studies are usually performed on small cm-scale samples, typically below 100 mg. Such a small size, combined with anisotropy and other spurious effects have been shown to be the source of additional complexity [7]. We measured the natural remanent magnetization and magnetic susceptibility of 105 large Apollo samples (mass range 40 g to 2.9 kg, median mass 350 g). For this, following the approach utilized for the initial paleomagnetic evaluation of Apollo 11 samples [8], we developed a dedicated magnetometer using a fluxgate sensor and a rotating stage, which allowed measuring the bulk samples in their original Teflon and aluminum packaging under nitrogen atmosphere. Despite a number of caveats (no demagnetization steps, existence of viscous magnetization and other soft secondary magnetization), the ratio of natural remanent magnetization to susceptibility gives a rough estimate of the paleointensity. The evolution of the paleointensity with the estimated age of the samples will provide a broad picture of the evolution of the lunar dynamo. Susceptibility, as a proxy to the bulk metal content in lunar rocks [9], is also a valuable source of information per se but is currently available only for a small fraction of the Apollo collection. Our survey will allow identification of rocks with unusual magnetic properties, and therefore potentially unusual petrogenesis. References: [1] Fuller & Cisowski 1987. In Jacobs (Ed.) Geomagnetism, 307-455 [2] Garrick-Bethell et al. 2009. Science 323:356-359 [3] Cournède et al. 2012. EPSL 33:31-42 [4] Shea et al. 2012. Science 335:453-456 [5] Suavet et al. 2013. PNAS 110:8453-8456 [6] Tikoo et al. 2014. EPSL in press [7] Tikoo et al. 2012. EPSL 337:93-103 [8] Doell & Gromm

  6. Magnetic Transitions and Domain Properties in Terbium, Dysprosium and Gadolinium.

    NASA Astrophysics Data System (ADS)

    McKenna, Timothy John

    The magnetic behaviour of the heavy rare earth metals Tb and Dy has been examined by a variety of ac techniques based on phase sensitive detection methods. Measurements of the ac magnetic susceptibility (chi), the transient enhancement of (chi), its temperature modulation signal. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). and ac specific heat have been made on a high purity Tb single crystal (99.98 (wt)% pure) and polycrystalline Tb and Dy samples over the temperature range 4.2 - 300 K. In particular the ferromagnetic (T < T(,c)) and antiferromagnetic (T(,c) < T < T(,N)) regions of both materials (Tb: Tc = 221 K, T(,N) = 229 K; Dy: T(,c) (TURN) 85 K, T(,N) = 178 K) have been studied in low applied ac magnetic fields (< 1000 Am('-1)). The results provide strong evidence for the existence of spiral spin antiferromagnetic (AF) domains in the AF region of rare earth helical antiferromagnets. A discontinuous change in (chi) was observed at the ferromagnetic-AF transition in the Tb single crystal. Hysteresis in this transition temperature (T(,+) (warming) (TURNEQ) T(,-) (cooling) + 0.2 K), indicated by the susceptibility measurements, was confirmed by ac and dc specific heat results. The susceptibility and specific heat results confirmed the first order nature of the ferromagnetic-AF transition in Tb. A latent heat value of L = 13 (+OR-) 3 J mole('-1) was derived from the dc specific heat measurements of this study. A theoretical examination of the effects of a distribution of T(,c) values on the high temperature critical susceptibility exponent (gamma) was undertaken. Both analytical and numerical solutions for (gamma) were derived for the fitting of broadened susceptibility data to the simple critical equation. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). An experimental situation was simulated by fitting (chi) data which was broadened by a distribution of T(,c) values. It was concluded that, if a (gamma) value deduced from fitting. experimental

  7. The magnetic properties of aligned M hexa-ferrite fibres

    NASA Astrophysics Data System (ADS)

    Pullar, R. C.; Bhattacharya, A. K.

    2006-05-01

    Aligned and random fibres of strontium hexaferrite (SrM, SrFe 12O 19) and barium hexaferrite (BaM, BaFe 12O 19) were manufactured by blow spinning from an aqueous inorganic sol-gel precursor, which was then fired to give the hexagonal ferrite fibre. Their magnetic properties were studied by VSM, investigating the evolution of these properties with firing and measurement temperature, and in particular the effects of fibre alignment. It has been predicted that aligned ferrite fibres will demonstrate an enhanced magnetisation along the axis of alignment with respect to perpendicular to the axis, and this has been demonstrated here for the first time. The optimum firing temperature was 1000 °C, at which point they still had submicron grains. In BaM random fibres Ms=63.8 emu g -1 and Hc=428.1 kA m -1, and in SrM random fibres Ms=63.3 emu g -1 and Hc=452.8 kA m -1, high values for polycrystalline materials. Fibres aligned parallel to the applied field had saturation magnetisation ( Ms) values equal to those of the random fibres, whilst fibres aligned perpendicular to the field had Ms values 62% and 75% lower, for BaM and SrM, respectively. There was no change in coercivity ( Hc) between random or aligned fibres of any orientation, and fibres aligned 45° and parallel to H appeared identical. Therefore, properties along the axis of alignment were superior when compared to measurements perpendicular to the axis of alignment, giving a directionality to the magnetisation in an otherwise randomly oriented ferrite material.

  8. Assembly and magnetic properties of nickel nanoparticles on silicon nanowires

    SciTech Connect

    Picraux, Samuel T; Manandhar, Pradeep; Nazaretski, E; Thompson, J

    2009-01-01

    The directed assembly of magnetic Ni nanoparticles at the tips of silicon nanowires is reported. Using electrodeposition Ni shells of thickness from 10 to 100 nm were selectively deposited on Au catalytic seeds at the ends of nanowires. Magnetic characterization confirms a low coercivity ({approx}115 Oe) ferromagnetic behavior at 300 K. This approach to multifunctional magnetic-semiconducting nanostructure assembly could be extended to electrodeposition of other materials on the nanowire ends, opening up novel ways of device integration. Such magnetically functionalized nanowires offer a new approach to developing novel highly localized magnetic probes for high resolution magnetic resonance force microscopy.

  9. Strain-Magnetization Properties and Domain Structures of Silicon Steel Sheets

    NASA Astrophysics Data System (ADS)

    Notoji, Atsushi; Saito, Akihiko; Hayakawa, Motozo

    The effects of tensile stress and strain on magnetization and magnetic domains in silicon steel sheets were investigated. The magnetization of elastic deformation regions decreased with increase of strain and the strain-magnetization properties of plastic deformation regions under stress showed peculiar characteristics. The magnetization increased with decreasing strain. We observed Lancet and other domains in a sample, especially around the boundary of crystal, after removing stress applied to a plastic deformation region. This phenomenon can be explained by changes in the domain structures, which were partly observed. This results obtained in this investigation can be applied to the nondestructive detection of fatigue in metallic magnetic materials.

  10. Endowing carbon nanotubes with superparamagnetic properties: applications for cell labeling, MRI cell tracking and magnetic manipulations

    NASA Astrophysics Data System (ADS)

    Lamanna, Giuseppe; Garofalo, Antonio; Popa, Gabriela; Wilhelm, Claire; Bégin-Colin, Sylvie; Felder-Flesch, Delphine; Bianco, Alberto; Gazeau, Florence; Ménard-Moyon, Cécilia

    2013-05-01

    Coating of carbon nanotubes (CNTs) with magnetic nanoparticles (NPs) imparts novel magnetic, optical, and thermal properties with potential applications in the biomedical domain. Multi-walled CNTs have been decorated with iron oxide superparamagnetic NPs. Two different approaches have been investigated based on ligand exchange or ``click chemistry''. The presence of the NPs on the nanotube surface allows conferring magnetic properties to CNTs. We have evaluated the potential of the NP/CNT hybrids as a contrast agent for magnetic resonance imaging (MRI) and their interactions with cells. The capacity of the hybrids to magnetically monitor and manipulate cells has also been investigated. The NP/CNTs can be manipulated by a remote magnetic field with enhanced contrast in MRI. They are internalized into tumor cells without showing cytotoxicity. The labeled cells can be magnetically manipulated as they display magnetic mobility and are detected at a single cell level through high resolution MRI.Coating of carbon nanotubes (CNTs) with magnetic nanoparticles (NPs) imparts novel magnetic, optical, and thermal properties with potential applications in the biomedical domain. Multi-walled CNTs have been decorated with iron oxide superparamagnetic NPs. Two different approaches have been investigated based on ligand exchange or ``click chemistry''. The presence of the NPs on the nanotube surface allows conferring magnetic properties to CNTs. We have evaluated the potential of the NP/CNT hybrids as a contrast agent for magnetic resonance imaging (MRI) and their interactions with cells. The capacity of the hybrids to magnetically monitor and manipulate cells has also been investigated. The NP/CNTs can be manipulated by a remote magnetic field with enhanced contrast in MRI. They are internalized into tumor cells without showing cytotoxicity. The labeled cells can be magnetically manipulated as they display magnetic mobility and are detected at a single cell level through high

  11. Technique to quantitatively measure magnetic properties of thin structures at <10 NM spatial resolution

    DOEpatents

    Bajt, Sasa

    2003-07-08

    A highly sensitive and high resolution magnetic microscope images magnetic properties quantitatively. Imaging is done with a modified transmission electron microscope that allows imaging of the sample in a zero magnetic field. Two images from closely spaced planes, one in focus and one slightly out of focus, are sufficient to calculate the absolute values of the phase change imparted to the electrons, and hence obtain the magnetization vector field distribution.

  12. Magnetic properties of nanocomposites based on opal matrices with embedded ferrite-spinel nanoparticles

    NASA Astrophysics Data System (ADS)

    Rinkevich, A. B.; Korolev, A. V.; Samoylovich, M. I.; Klescheva, S. M.; Perov, D. V.

    2016-02-01

    Magnetic properties of nanocomposites based on opal matrices with ferrite-spinel nanoparticles embedded have been investigated in temperature range from 2 to 300 K. The magnetization curves and hysteresis loops as well as the temperature dependence of magnetic moment and the temperature and frequency dependences of AC susceptibility have been measured. The results of magnetic measurements are compared to X-ray analysis and electron microscopy investigations.

  13. Fe and Co nanostructures embedded into the Cu(100) surface: Self-Organization and magnetic properties

    SciTech Connect

    Kolesnikov, S. V. Klavsyuk, A. L.; Saletsky, A. M.

    2015-10-15

    The self-organization and magnetic properties of small iron and cobalt nanostructures embedded into the first layer of a Cu(100) surface are investigated using the self-learning kinetic Monte Carlo method and density functional theory. The similarities and differences between the Fe/Cu(100) and the Co/Cu(100) are underlined. The time evolution of magnetic properties of a copper monolayer with embedded magnetic atoms at 380 K is discussed.

  14. Final Report for Grant of Properties of Magnetic Multilayer and Microstructures

    DTIC Science & Technology

    2007-11-02

    Properties of Magnetic Multilayer and Microstructures 5. FUNDING NUMBERS Proposal Number 375277-PH DAAG55-98-0294 6. AUTHOR(S...report describes research done on the basic physics of magnetic multilayers and microstructures. Among the problems studied were...1998 to 01-04-2002 4. TITLE AND SUBTITLE Final Report for grant of Properties of Magnetic Multilayer and Microstructures Unclassified 5a. CONTRACT

  15. Magnetic properties of Fe-Mn-Pt for heat assisted magnetic recording applications

    SciTech Connect

    Park, Jihoon; Hong, Yang-Ki; Kim, Seong-Gon; Gao, Li; Thiele, Jan-Ulrich

    2015-02-07

    We calculate the electronic structures of FePt and Fe{sub 0.5}Mn{sub 0.5}Pt using first-principles calculations based on density functional theory within the local-spin-density approximation. The Curie temperature (T{sub c}) was calculated by mean field approximation. Composition dependence of the Cure temperature (T{sub c}(x)) of Fe{sub 1−x}Mn{sub x}Pt was used to identify a composition to meet the desired T{sub c} in the range of 600–650 K. The identified composition (0.0294 ≤ x ≤ 0.0713) gives saturation magnetization (M{sub s}) in the range of 1041–919 emu/cm{sup 3} and magnetocrystalline anisotropy constant (K) in the range of 9.96–8.36 × 10{sup 6 }J/m{sup 3} at 0 K. Temperature dependent M(T) and K(T) of Fe{sub 1−x}Mn{sub x}Pt (0.0294 ≤ x ≤ 0.0713) were calculated using the Brillouin function and Callen-Callen experimental relation, respectively. Fe{sub 1−x}Mn{sub x}Pt (0.0294 ≤ x ≤ 0.0713) shows 930–800 emu/cm{sup 3} of M{sub s} and 7.18–5.61 × 10{sup 6 }J/m{sup 3} of K at 300 K, thereby satisfying desired magnetic properties for heat-assisted magnetic recording media to achieve 4 Tb/in.{sup 2} areal density.

  16. On The Constitutive Properties Of Strongly Magnetized Matter Observed In A Class Of Solar Ejecta

    NASA Astrophysics Data System (ADS)

    Berdichevsky, D. B.

    2013-12-01

    Several studies of the transient events known as magnetic clouds at 1 AU suggest that they possess the ';1/2' anomalous value for its adiabatic, polytropic index, i.e., γ= 1/2, which implies that the temperature of the plasma decreases with increased density[1-3]. Coronal mass ejections commonly observed by missions like The Solar Terrestrial Relations Observatory (STEREO) have been successfully modeled previously by Berdichevsky Stenborg and Vourlidas[4] as magnetic flux-ropes which propagate from the Sun with uniform velocity. Building on this existing analytical three-dimensional magnetohydrodynamic (MHD) model of a magnetic flux-rope, we present an interpretation of the anomalous and somewhat counterintuitive dynamic property mentioned above. Using plasma and magnetic field observations by the Wind spacecraft for the magnetic cloud of June 2, 1998, we argue that this anomalous polytropic index is indeed a consequence of thermodynamic processes in this strongly magnetized matter. We show that the derived models of Berdichevsky et al.[5, 6] easily accommodate a familiar thermodynamic explanation of this property. Such an explanation may shed light also on the evolution of other astrophysical observations such as remnants in nebulae of past super-novae, as well other transient interstellar events. This MHD solution may be a good way to go beyond gas-dynamics in the development of a coherent picture of shock and its driver, as they are becoming a current interpretation. 1Osherovich, V.A., 1997, Proc. 31st, ESLAB Symp. Correlated Phenomena at the Sun, in the Heliosphere and in Geospace. 2Sittler, E.C., and L.F., Burlaga, 1998, J. Geophys. Res., 103, 17447. 3Nieves-Chinchilla T., and A., Figueroa-Viñas, 2008, J. Geophys. Res., 113, DOI: 10.1029/2007JA012703 4Berdichevsky, Stenborg, and Vourlidas, 2011, ApJ, 741, 47. 5Berdichevsky, D.B., R.L., Lepping, C.J., Farrugia, 2003, Phys.Rev. E, 67, DOI: 10.1103/PhysRevE036405. 6Berdichevsky, D.B. , 2012, Sol. Phys., 284

  17. Layered Metal Thiophosphite Materials: Magnetic, Electrochemical, and Electronic Properties.

    PubMed

    Mayorga-Martinez, Carmen C; Sofer, Zdeněk; Sedmidubský, David; Huber, Štěpán; Eng, Alex Yong Sheng; Pumera, Martin

    2017-03-29

    Beyond graphene, transitional metal dichalcogenides, and black phosphorus, there are other layered materials called metal thiophosphites (MPSx), which are recently attracting the attention of scientists. Here we present the synthesis, structural and morphological characterization, magnetic properties, electrochemical performance, and the calculated density of states of different layered metal thiophosphite materials with a general formula MPSx, and as a result of varying the metal component, we obtain CrPS4, MnPS3, FePS3, CoPS3, NiPS3, ZnPS3, CdPS3, GaPS4, SnPS3, and BiPS4. SnPS3, ZnPS3, CdPS3, GaPS4, and BiPS4 exhibit only diamagnetic behavior due to core electrons. By contrast, trisulfides with M = Mn, Fe, Co, and Ni, as well as CrPS4, are paramagnetic at high temperatures and undergo a transition to antiferromagnetic state on cooling. Within the trisulfides series the Néel temperature characterizing the transition from paramagnetic to antiferromagnetic phase increases with the increasing atomic number and the orbital component enhancing the total effective magnetic moment. Interestingly, in terms of catalysis NiPS3, CoPS3, and BiPS4 show the highest efficiency for hydrogen evolution reaction (HER), while for the oxygen evolution reaction (OER) the highest performance is observed for CoPS3. Finally, MnPS3 presents the highest oxygen reduction reaction (ORR) activity compared to the other MPSx studied here. This great catalytic performance reported for these MPSx demonstrates their promising capabilities in energy applications.

  18. Spindly cobalt ferrite nanocrystals: preparation, characterization and magnetic properties.

    PubMed

    Cao, Xuebo; Gu, Li

    2005-02-01

    In this paper we describe the preparation of homogeneously needle-shaped cobalt ferrite (CoFe(2)O(4)) nanocrystals on a large scale through the smooth decomposition of urea and the resulting co-precipitation of Co(2+) and Fe(3+) in oleic acid micelles. Furthermore, we found that other ferrite nanocrystals with a needle-like shape, such as zinc ferrite (ZnFe(2)O(4)) and nickel ferrite (NiFe(2)O(4)), can be prepared by the same process. Needle-shaped CoFe(2)O(4) nanocrystals dispersed in an aqueous solution containing oleic acid exhibit excellent stability and the formed colloid does not produce any precipitations after two months, which is of prime importance if these materials are applied in magnetic fluids. X-ray diffraction (XRD) measurements were used to characterize the phase and component of the co-precipitation products, and demonstrate that they are spinel ferrite with a cubic symmetry. Transmission electron microscopy (TEM) observation showed that all the nanocrystals present a needle-like shape with a 22 nm short axis and an aspect ratio of around 6. Varying the concentration of oleic acid did not bring about any obvious influence on the size distribution and shapes of CoFe(2)O(4). The magnetic properties of the needle-shaped CoFe(2)O(4) nanocrystals were evaluated by using a vibrating sample magnetometer (VSM), electron paramagnetic resonance (EPR), and a Mössbauer spectrometer, and the results all demonstrated that CoFe(2)O(4) nanocrystals were superparamagnetic at room temperature.

  19. Magnetic and microstructural properties of Fe3O4-coated Fe powder soft magnetic composites

    NASA Astrophysics Data System (ADS)

    Jo Sunday, Katie; Hanejko, Francis G.; Taheri, Mitra L.

    2017-02-01

    Soft magnetic composites (SMCs) comprised of ferrite-coated ferrous powder permit isotropic magnetic flux capabilities, lower core losses, and complex designs through the use of traditional powder metallurgy techniques. Current coating materials and methods are vastly limited by the nonmagnetic properties of organic and some inorganic coatings and their inability to withstand high heat treatments for proper stress relief of core powder after compaction. Ferrite-based coatings are ferrimagnetic, highly resistive, and possess high melting temperatures, thus providing adequate electrical barriers between metallic particles. In this work, iron powder was coated with Fe3O4 particles via mechanical milling, then compacted and cured in an inert gas environment. We find density and coercivity to improve with increasing temperatures; however, core loss greatly increases, which is attributed to the formation of a more conductive iron-oxide phase and less resistive Fe volume. Our work begins to exemplify the unique qualities and potential for ferrite-based coatings using traditional powder metallurgy techniques and higher curing temperatures for electromagnetic devices.

  20. Psychometric Properties of the Existence Subscale of the Purpose in Life Questionnaire for Chinese Adolescents in Hong Kong

    PubMed Central

    Law, Ben M. F.

    2012-01-01

    The current study aims to test the psychometric properties of the Existence Subscale of the Purpose in Life Questionnaire (EPIL) for early adolescence. The Purpose in Life Questionnaire (PIL), originally created by Craumbaugh and Maholick, is a 20-item scale measuring different dimensions of life purposes. The current study selected seven items representative of the existence dimension to form another scale, the EPIL. The analysis was based on 2842 early adolescents, ranging from 11 to 14 years old. Principal axis factoring found one factor, with 60% variance being explained. Cronbach's alpha for the EPIL was 0.89, which was high. The factor structure was stable across genders. Criterion-related validity was determined when the scale was used to differentiate volunteers and nonvolunteers. Construct validity was found when the scale was associated with life satisfaction. The results give support to the fact that the EPIL could be used alone to measure the psychological well-being of early adolescents and the appropriateness of the EPIL in adolescent research. PMID:22927785

  1. Regulated magnetic domains and high-frequency property in magnetic materials with columnar structure

    NASA Astrophysics Data System (ADS)

    Zhou, Cai; Wei, Wenwen; Jiang, Changjun

    2015-10-01

    The regulation of magnetic domains and high-frequency property in Fe20Ni80 thin films sputtered on anodic aluminum oxide (AAO) substrates with different apertures and a Si substrate were investigated. The obvious stripe domain structure was observed in FeNi thin film sputtered on AAO (pore in diameter d ~ 20 nm) substrate. The distinct cross-sectional columnar structures prepared on three different substrates and measured by scanning electron microscope were shown, which arose from different growth mechanisms on various kinds of substrates. The structure of AAO substrate could modulate the growth mechanism of thin films and the appearance of stripe domains structure. In addition, the resonant frequency was enhanced in FeNi thin film prepared on AAO ( d ~ 20 nm) substrate.

  2. Probing the existing magnetic phases in Pr0.5Ca0.5MnO3 (PCMO) nanowires and nanoparticles: magnetization and magneto-transport investigations

    NASA Astrophysics Data System (ADS)

    Rao, S. S.; Bhat, S. V.

    2010-03-01

    We show from conventional magnetization measurements that the charge order (CO) is completely suppressed in 10 nm Pr0.5Ca0.5MnO3(PCMO 10) nanoparticles. Novel magnetization measurements, designed by a special high field measurement protocol, show that the dominant ground state magnetic phase is ferromagnetic-metallic (FM-M), which is an equilibrium phase, which coexists with the residual charge ordered anti-ferromagnetic phase (CO AFM) (an arrested phase) and exhibits the characteristic features of a 'magnetic glassy state' at low temperatures. It is observed that there is a drastic reduction in the field required to induce the AFM to FM transition (~5-6 T) compared to their bulk counterpart (~27 T) this phase transition is of first order in nature, broad, irreversible and the coexisting phases are tunable with the cooling field. Temperature-dependent magneto-transport data indicate the occurrence of a size-induced insulator-metal transition (TM - I) and anomalous resistive hysteresis (R-H) loops, pointing out the presence of a mixture of the FM-M phase and AFM-I phase.

  3. Grain Texture, Nd Content and Processing Condition Effects on Magnetic Properties of NdFeB Composite Magnets

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoya; Hu, Lianxi; Li, Yuping; Deng, Taiqing

    2013-07-01

    The effects of grain texture, Nd content, processing conditions on magnetic properties and behavior of NdFeB nanocomposite magnet were investigated. The results demonstrate that mechanically activated disproportionation and desorption-recombination combined with plastic deformation process (M-HDDR & D) is an effective way to produce anisotropic NdFeB-type magnet. Magnetic anisotropy significantly enhances the magnetic properties of Nd16Fe76B8 nanocomposite magnet, with the intrinsic coercivity (Hci), magnetic induction (Br), and the energy product (BH)max achieving 0.88 T, 676.8 kA/m, and 135.2 kJ/m3, respectively. Decrease in Nd content improves the remanence but deteriorates the coercivity of NdFeB ternary composites. A low annealing temperature or short annealing time leads to an incomplete recombination, while a high temperature or long annealing time may result in grain overgrowth, and the optimum processing condition is found to be 780°C × 30 min. Pinning mechanism dominates in the magnetic hardening mechanism of Nd16Fe76B8 composites prepared by both complete and incomplete recombination process, and particularly reversal nucleation process is also responsible for the latter case.

  4. Local Magnetic Properties in Non-oriented Electrical Steel and Their Dependence on Magnetic Easy Axis and Misorientation Parameters

    NASA Astrophysics Data System (ADS)

    Gallaugher, Matthew; Samimi, Arash; Krause, Thomas W.; Clapham, Lynann C.; Chromik, Richard R.

    2015-03-01

    An understanding of how material parameters, especially orientation and misorientation, influence the magnetic properties of non-oriented electrical steel (NOES) is important for improving the efficiency of the material in service. In this study, the local magnetic properties were measured using magnetic Barkhausen noise (MBN) on different test locations on different strips of NOES material. Local variations in magnetic properties, texture, and misorientation were revealed. A new interpretation for misorientation, called the easy axis misorientation (EAM), was created to describe the alignment of the magnetic easy axes between neighboring grains. This new EAM, visualized as a single value parameter or graphed as a distribution, was shown to be more effective at predicting the isotropic magnetic properties than previously used texture parameters based on standard orientation/misorientation definitions. It was found that a larger EAM value, especially when associated with a lower small angle EAM intensity distribution, was associated with a larger MBN energy. A larger MBN energy has been previously associated with lower losses, and therefore a greater material efficiency.

  5. Luminescence, Plasmonic and Magnetic Properties of Doped Semiconductor Nanocrystals: Current Developments and Future Prospects.

    PubMed

    Pradhan, Narayan; Adhikari, Samrat Das; Nag, Angshuman; Sarma, D D

    2017-02-02

    Introducing few atoms of impurities or dopants in semiconductor nanocrystals can drastically alter the existing or even introduce new properties. For example, mid-gap states created by doping tremendously affect photocatalytic activities and surface controlled redox reactions, generate new emission centres, show thermometric optical switching, make suitable FRET donors by enhancing the excited state lifetime and also create localized surface plasmon resonance induced low energy absorption. In addition, researchers have more recently started focusing their attention on doped nanocrystals as an important and alternative material for solar energy conversion in order to meet the current demand for renewable energy. Moreover, electrical as well as magnetic properties of the host are also strongly altered on doping. These dopant-induced beneficial changes in material properties suggest that doped nanocrystals with proper selections of dopant-host pairs may be helpful for generating designer materials for a wide range of current technological needs. Such exciting properties related to various aspects of doping a variety of semiconductor nanocrystals are summarized and reported in this mini review.

  6. Multifunctional wood materials with magnetic, superhydrophobic and anti-ultraviolet properties

    NASA Astrophysics Data System (ADS)

    Gan, Wentao; Gao, Likun; Sun, Qingfeng; Jin, Chunde; Lu, Yun; Li, Jian

    2015-03-01

    Multifunctional wood materials with magnetic, superhydrophobic and anti-ultraviolet properties were obtained successfully by precipitated CoFe2O4 nanoparticles on the wood surface and then treated with a layer of octadecyltrichlorosilane (OTS). The as-fabricated wood composites exhibited excellent magnetic property and the water contact angle of the OTS-modified magnetic wood surface reached as high as 150°, revealed the superhydrophobic property. Moreover, accelerated aging tests suggested that the treated wood composites also have an excellent anti-ultraviolet property.

  7. Effect of the existing form of Cu element on the mechanical properties, bio-corrosion and antibacterial properties of Ti-Cu alloys for biomedical application.

    PubMed

    Zhang, Erlin; Wang, Xiaoyan; Chen, Mian; Hou, Bing

    2016-12-01

    Ti-Cu alloys have exhibited strong antibacterial ability, but Ti-Cu alloys prepared by different processes showed different antibacterial ability. In order to reveal the controlling mechanism, Ti-Cu alloys with different existing forms of Cu element were prepared in this paper. The effects of the Cu existing form on the microstructure, mechanical, corrosion and antibacterial properties of Ti-Cu alloys have been systematically investigated. Results have shown that the as-cast Ti-Cu alloys showed a higher hardness and mechanical strength as well as a higher antibacterial rate (51-64%) but a relatively lower corrosion resistance than pure titanium. Treatment at 900°C/2h (T4) significantly increased the hardness and the strength, improved the corrosion resistance but had little effect on the antibacterial property. Treatment at 900°C/2h+400°C/12h (T6) increased further the hardness and the mechanical strength, improved the corrosion resistance and but also enhanced the antibacterial rate (>90%) significantly. It was demonstrated that the Cu element in solid solution state showed high strengthening ability but low antibacterial property while Cu element in Ti2Cu phase exhibited strong strengthening ability and strong antibacterial property. Ti2Cu phase played a key role in the antibacterial mechanism. The antibacterial ability of Ti-Cu alloy was strongly proportional to the Cu content and the surface area of Ti2Cu phase. High Cu content and fine Ti2Cu phase would contribute to a high strength and a strong antibacterial ability.

  8. Complexity in the structural and magnetic properties of almost multiferroic EuTi O3

    NASA Astrophysics Data System (ADS)

    Guguchia, Z.; Salman, Z.; Keller, H.; Roleder, K.; Köhler, J.; Bussmann-Holder, A.

    2016-12-01

    In a number of recent publications hidden magnetic properties at high temperatures have been reported for EuTi O3 (ETO), which orders antiferromagnetically below TN=5.7 K . In addition, structural phase transitions have been discovered which correlate with the magnetic responses and can be tuned by a magnetic field. In order to identify the magnetic properties of ETO at temperatures well above TN, low-energy muon-spin rotation (μSR) experiments have been performed on thin films of ETO which exhibit all properties observed in bulk materials and are thus well suited to conclude about the magnetic order of the bulk. The μSR data reveal anomalies at 282 and 200 K related to the structural phase transitions in accordance with birefringence results. In addition, a transition to some kind of magnetic order below 100 K was observed as previously indirectly deduced from conductivity and dielectric constant measurements.

  9. Magnetoelastic properties of antiferromagnetically coupled magnetic composite media

    NASA Astrophysics Data System (ADS)

    Valencia-Cardona, Juan J.; Leo, Perry H.

    2016-08-01

    We study the magnetic response of a ferromagnetic bilayer with antiferromagnetic coupling, where the layers experience magnetostrictive strains and epitaxial misfit strains. These strains cause the layers to stretch and bend as the magnetic spins of the layers rotate, resulting in elastic energy that adds to the magnetic energy of the system. The magnetic and elastic energies are computed as a function of spin direction in each layer for a given set of material and geometric parameters. By finding the rotations that minimize the total energy, we compute magnetic hysteresis loops for different combinations of magnetic and elastic parameters. The elastic contribution is reflected in the transitions at the corners of the hysteresis curves as well as in the coercive field of the main loop. The details of the elastic contribution depend in a complicated way on the magnetostriction of the layers, the epitaxial strain, the magnetic anisotropies, and the system geometry.

  10. Self-consistent model of a solid for the description of lattice and magnetic properties

    NASA Astrophysics Data System (ADS)

    Balcerzak, T.; Szałowski, K.; Jaščur, M.

    2017-03-01

    In the paper a self-consistent theoretical description of the lattice and magnetic properties of a model system with magnetoelastic interaction is presented. The dependence of magnetic exchange integrals on the distance between interacting spins is assumed, which couples the magnetic and the lattice subsystem. The framework is based on summation of the Gibbs free energies for the lattice subsystem and magnetic subsystem. On the basis of minimization principle for the Gibbs energy, a set of equations of state for the system is derived. These equations of state combine the parameters describing the elastic properties (relative volume deformation) and the magnetic properties (magnetization changes). The formalism is extensively illustrated with the numerical calculations performed for a system of ferromagnetically coupled spins S=1/2 localized at the sites of simple cubic lattice. In particular, the significant influence of the magnetic subsystem on the elastic properties is demonstrated. It manifests itself in significant modification of such quantities as the relative volume deformation, thermal expansion coefficient or isothermal compressibility, in particular, in the vicinity of the magnetic phase transition. On the other hand, the influence of lattice subsystem on the magnetic one is also evident. It takes, for example, the form of dependence of the critical (Curie) temperature and magnetization itself on the external pressure, which is thoroughly investigated.

  11. Magnetoliposomes with high USPIO entrapping efficiency, stability and magnetic properties.

    PubMed

    Skouras, Athanasios; Mourtas, Spyridon; Markoutsa, Eleni; De Goltstein, Marie-Christine; Wallon, Claire; Catoen, Sarah; Antimisiaris, Sophia G

    2011-10-01

    The DRV technique (followed by extrusion) was used for construction of hydrophilic-USPIO encapsulating liposomes. Magnetoliposomes (ML) were characterized for size, surface charge, entrapment, physical stability and magnetic properties (relaxivity). Results show that nanosized extruded-DRV MLs encapsulate higher amounts of USPIOs in comparison with sonicated vesicles. Fe (III) encapsulation efficiency (EE) is 12%, the highest reported to date for nanosized MLs. EE of MLs is influenced by ML membrane composition and polyethyleneglycol (PEG) coating. PEG-coating increases ML EE and stability; however, r(2)-to-r(1) ratios decrease (in comparison with non-PEGylated MLs). Most ML-types are efficient T2 contrast agents (because r(2)-to-r(1) ratios are higher than that of free USPIOs). Targeted MLs were formed by successfully immobilizing OX-26 monoclonal antibody on ML surface (biotin-streptavidin ligation), without significant loss of USPIOs. Targeted MLs retained their nanosize and integrity during storage for 1 month at 4 °C and up to 2 weeks at 37 °C.

  12. Tuning of magnetic properties in cobalt ferrite nanocrystals

    SciTech Connect

    Cedeno-Mattei, Y.; Roman, F.; Perales-Perez, O.; Tomar, M. S.; Voyles, P. M.; Stratton, W. G.

    2008-04-01

    Cobalt ferrite (CoFe{sub 2}O{sub 4}) possesses excellent chemical stability, good mechanical hardness, and a large positive first order crystalline anisotropy constant, making it a promising candidate for magneto-optical recording media. In addition to precise control of the composition and structure of CoFe{sub 2}O{sub 4}, its practical application will require the capability to control particle size at the nanoscale. The results of a synthesis approach in which size control is achieved by modifying the oversaturation conditions during ferrite formation in water through a modified coprecipitation approach are reported. X-ray diffraction, transmission electron microscopy (TEM) diffraction, and TEM energy-dispersive x-ray spectroscopy analyses confirmed the formation of the nanoscale cobalt ferrite. M-H measurements verified the strong influence of synthesis conditions on crystal size and hence, on the magnetic properties of ferrite nanocrystals. The room-temperature coercivity values increased from 460 up to 4626 Oe under optimum synthesis conditions determined from a 2{sup 3} factorial design.

  13. In vivo brain viscoelastic properties measured by magnetic resonance elastography.

    PubMed

    Green, Michael A; Bilston, Lynne E; Sinkus, Ralph

    2008-08-01

    Magnetic resonance elastography (MRE) is a non-invasive imaging technique used to visualise and quantify mechanical properties of tissue, providing information beyond what can be currently achieved with standard MR sequences and could, for instance, provide new insight into pathological processes in the brain. This study uses the MRE technique at 3 T to extract the complex shear modulus for in vivo brain tissue utilizing a full three-dimensional approach to reconstruction, removing contributions of the dilatational wave by application of the curl operator. A calibrated phantom is used to benchmark the MRE measurements, and in vivo results are presented for healthy volunteers. The results provide data for in vivo brain storage modulus (G'), finding grey matter (3.1 kPa) to be significantly stiffer than white matter (2.7 kPa). The first in vivo loss modulus (G'') measurements show no significant difference between grey matter (2.5 kPa) and white matter (2.5 kPa).

  14. Effect of Electronic and Magnetic Valences on Phase Transition and Magnetic Properties in Co-Ni-Al-RE (RE = Gd, Dy and Er) Alloys

    NASA Astrophysics Data System (ADS)

    Ju, Jia; Lou, Shuting; Yang, Liu; Li, Tao; Hao, Shuai; Yan, Chen

    2017-02-01

    The effect of the electronic and magnetic valence state on the phase transition and magnetic properties of several Co-Ni-Al-RE (RE = Gd, Dy and Er) ferromagnetic shape memory alloys were investigated. The martensitic transformation temperature showed a distinct increase with increasing the valence electron concentration, but no obvious change in the magnetic properties of the alloys was observed with increasing the valence electron concentration. On the other hand, the magnetic properties of the sample increased with the magnetic valence number of the alloy, while no change was observed in the phase transformation temperature with the magnetic valence number.

  15. Fabrication, morphological, structural and magnetic properties of electrodeposited Fe3Pt nanowires and nanotubes

    NASA Astrophysics Data System (ADS)

    Khan, U.; Adeela, N.; Li, Wenjing; Irfan, M.; Javed, K.; Riaz, S.; Han, X. F.

    2017-02-01

    Highly ordered Fe3Pt nanowires (NWs) and nanotubes (NTs) embedded in anodic aluminum oxide (AAO) template have been fabricated by dc electrodeposition method. Response of heat treatment on structural and magnetic properties of the samples has been studied with and without the presence of magnetic field (1 T). X-Ray Diffraction analysis shows chemically ordered L12 face centered cubic (FCC) as the dominant phase for Fe3Pt NWs and heat treatment improves crystallinity with retained its phase. Whereas, Fe3Pt NTs show amorphous behavior with and without magnetic field annealing. Furthermore, magnetic properties of the samples have been investigated by vibrating sample magnetometer (VSM). Magnetic parameters of Fe3Pt including magnetic coercivity, saturation magnetization, squareness and shape of MH-loops have been investigated as a result of simple and MF annealing.

  16. Intrinsic magnetic properties of bimetallic nanoparticles elaborated by cluster beam deposition.

    PubMed

    Dupuis, V; Khadra, G; Hillion, A; Tamion, A; Tuaillon-Combes, J; Bardotti, L; Tournus, F

    2015-11-14

    In this paper, we present some specific chemical and magnetic order obtained very recently on characteristic bimetallic nanoalloys prepared by mass-selected Low Energy Cluster Beam Deposition (LECBD). We study how the competition between d-atom hybridization, complex structure, morphology and chemical affinity affects their intrinsic magnetic properties at the nanoscale. The structural and magnetic properties of these nanoalloys were investigated using various experimental techniques that include High Resolution Transmission Electron Microscopy (HRTEM), Superconducting Quantum Interference Device (SQUID) magnetometry, as well as synchrotron techniques such as Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Magnetic Circular Dichroism (XMCD). Depending on the chemical nature of the nanoalloys we observe different magnetic responses compared to their bulk counterparts. In particular, we show how specific relaxation in nanoalloys impacts their magnetic anisotropy; and how finite size effects (size reduction) inversely enhance their magnetic moment.

  17. Magnetic properties of RCo2 compounds in the exchange-striction model of ferrimagnets

    NASA Astrophysics Data System (ADS)

    Valiev, E. Z.; Teplykh, A. E.

    2017-01-01

    The original version of the exchange-striction model of a ferrimagnet has been employed for calculating a number of magnetic properties of RCo2 ferrimagnets, where R = Er, Ho, Dy, Tb, and Gd are rareearth ions. The following magnetic properties are calculated: pressure dependence of the Curie temperature ( T C), temperature dependences of magnetization in sublattices of cobalt and rare-earth atoms, and isotherms of magnetization of these lattices at T > T C. For an ErCo2 sample, the H-T phase diagram has been constructed and the magnetization in the magnetic fields H = 0-70 T has been calculated. The calculated and experimental results have been compared. Based on the exchange-striction model, the qualitative explanation of the difference in the type of the magnetic phase transformation in the intermetallic compounds with R = Tb and Gd and R = Er, Ho, and Dy is given.

  18. Studies on magnetic properties of unique molecular magnet {[FeII(pyrazole)4]2[NbIV(CN)8]•4H2O}n

    NASA Astrophysics Data System (ADS)

    Konieczny, P.; Pełka, R.; Zieliński, P. M.; Wasiutyński, T.; Pinkowicz, D.; Sieklucka, B.

    2013-01-01

    In this paper magnetic properties of hybrid inorganic-organic compound {[FeII(pyrazole)4]2[NbIV(CN)8]•4H2O}n are presented. This is a three dimensional molecular magnet with well localized magnetic moments, which make it a suitable candidate for testing magnetic models. In order to characterize the magnetic properties of the above compound we performed the AC/DC magnetometry in the range 0-5 T. The special attention was paid to the phase transition at 7.9 K. The study in magnetic field supports magnetic ordering below 7.9 K.

  19. Preliminary Results of the Magnetic Properties Experiments on the Mars Exploration Rovers, Spirit and Opportunity

    NASA Technical Reports Server (NTRS)

    Hviid, S. F.; Bertelsen, P.; Goetz, W.; Kinch, K. M.; Knudsen, J. M.; Madsen, M. B.; Squyres, S. W.; Bell, J. F., III; Yen, A.; Johnson, M. J.

    2004-01-01

    The Mars Exploration Rovers each carry a set of Magnetic Properties Experiments designed to investigate the properties of the air-borne dust in the Martian atmosphere. It is a preferred interpretation of previous experiments (Viking 1 & 2, 1976 and Mars Pathfinder, 1997) that the airborne dust in the Martian atmosphere is primarily composed by composite silicate particles containing one or more highly magnetic minerals as a minor constituent, this minor constituent probably being dominated by the mineral maghemite (gamma-Fe2O3). The ultimate goal of the magnetic properties experiments on the Mars Exploration Rover mission is to provide some information/constraints on whether the dust is formed by volcanic, meteoritic, aqueous, or other processes. In detail, the objectives are: a) To identify the magnetic mineral(s) in the dust, soil and rocks on Mars. b) To establish if the magnetic material is present in the form of nanosized (d < 10 nm) superparamagnetic crystallites embedded in the micrometer sized airborne dust part icles. c) To establish if the magnets are culling a subset of strongly magnetic particles or if essentially all particles of the airborne dust are sufficiently magnetic to be attracted by the magnets. d) Detect compositional differences between the airborne dust and the soil and rock sites which are investigated at two landing sites. To accomplish these goals the Mars Exploration Rovers each carry a set of permanent magnets of several different strengths and sizes. Each magnet has its own specific objective.

  20. Magnetic properties and coercivity mechanism of isotropic HDDR NdFeB bonded magnets with Co and Dy addition

    NASA Astrophysics Data System (ADS)

    Chen, W.; Gao, R. W.; Zhu, M. G.; Pan, W.; Li, W.; Li, X. M.; Han, G. B.; Feng, W. C.; Wang, B.

    2003-04-01

    Isotropic NdDyFeCoB bonded magnets with high coercivity of 1.59 MA/m and low temperature coefficient of remanence of -0.056%/ K (in the temperature range 298-428 K) were prepared successfully by controlling the HDDR process and adjusting the compositions. The influence of Co and Dy additions on the magnetic properties and the magnetization reversal process in magnet was investigated. The high coercivity in (Nd 0.8Dy 0.2) 13(Fe 0.875Co 0.125) 81B 6 HDDR magnet can be attributed to its unique microstructure and the enhancement of anisotropy field of 2:14:1 phase by substitution of Nd by Dy.

  1. Near-surface magnetic properties of Co-based amorphous ribbons

    NASA Astrophysics Data System (ADS)

    Shalyguina, E. E.; Ganshina, E. A.; Rheem, Young-Woo; Kim, Cheol Gi; Kim, Chong-Oh

    2003-04-01

    The near-surface magnetic properties of as-cast and annealed (for various times in open air at a temperature T=380°C) Co 66Fe 4B 15Si 15 amorphous ribbons were studied by using a magneto-optical magnetometer. The effect of etching of the annealed samples on their near-surface magnetic properties was investigated. The annealed samples exhibit the presence of a hard near-surface magnetic layer. The hysteresis loops of the etched ribbons change strongly. For etching times ( tetch) larger than 50 s, an influence of the ribbon core on the near-surface magnetic properties of the sample was observed. For tetch>120 s, the hysteresis loops and other magnetic properties of the etched and as-cast samples were practically identical.

  2. Intrinsic magnetic properties of ZnO nanoislands: Insight from first-principles study

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Wu, Zhi-Feng; Gao, Peng-Fei; Zhang, Er-Hu; Zhang, Sheng-Li

    2016-03-01

    First-principles calculations have been employed to investigate magnetic and electronic properties of monolayer and multi-layer ZnO nanoislands which are hexagonal BN (h-BN) prototype structures with zigzag edges and a triangular form. Two types of the zigzag edges, that is, O-terminated and Zn-terminated ones are considered. It has been found that monolayer ZnO nanoislands with the O-terminated edges exhibit magnetic properties, regardless of the nanoislands size. However, the nanoislands with Zn-terminated edges are semiconductors, and the magnetic properties are observed just for some specific sizes. Charge transfer according to Bader charge analysis is introduced to elucidate the magnetic properties of the monolayer ZnO nanoislands. Besides, multi-layer ZnO nanoislands exhibit magnetic features when their layers are odd, while those of even layers are nonmagnetic.

  3. Innovative methodology for recovering titanium and chromium from a raw ilmenite concentrate by magnetic separation after modifying magnetic properties.

    PubMed

    Lv, Jin-Fang; Zhang, Han-Ping; Tong, Xiong; Fan, Chun-Lin; Yang, Wen-Tao; Zheng, Yong-Xing

    2017-03-05

    Raw ilmenite concentrate containing Cr can be either as a resource or as one kind of the most hazardous solid waste. In order to recover titanium and chromium from the raw concentrate which was separated from the Promenade deposit, Gaza province, Mozambique, an innovative technology using modification of magnetic property followed by magnetic separation was proposed. Magnetic property, phase and surface morphology of the sample before and after oxidizing roasting were firstly characterized by magnetism, chemistry, XRD and MLA analyses to interpret the mechanism of oxidizing roasting of the ilmenite. Then, these factors such as oxidizing roasting temperature, residence time and magnetic induction affecting on magnetic separation performance were examined and the optimum process parameters were determined. A commercial concentrate containing 47.94% TiO2 and 0.23% Cr2O3 was obtained and the recovery of TiO2 and Cr2O3 was 78.52% and 5.42%, respectively. The tailing obtained was preliminarily concentrated by a high-intensity magnetic separator and a rough chromite concentrate was gained. In order to further purify the rough one, reducing roasting was carried out to transform the minerals containing hematite into the minerals containing magnetite, followed by a low-intensity magnetic separation. The effects of these parameters such as temperature, carbon powder dosage, holding time and magnetic induction on magnetic separation performance were investigated and the optimal conditions were determined. A concentrate containing 28.65% Cr2O3 was obtained and the total recovery of Cr2O3 was 84.18%.

  4. Magnetic and magnetocaloric properties of DyMn2Si2 compound with multiple magnetic phase transition

    NASA Astrophysics Data System (ADS)

    dos Reis, D. C.; França, E. L. T.; de Paula, V. G.; dos Santos, A. O.; Coelho, A. A.; Cardoso, L. P.; da Silva, L. M.

    2017-02-01

    Structural, magnetic and magnetocaloric properties of the ternary intermetallic compound DyMn2Si2 are studied by X-ray diffraction and magnetization measurements. It is found that DyMn2Si2 crystalizes with tetragonal ThCr2S2-type structure and exhibits four successive magnetic transitions at low temperature, around 20 K, 31 K, 38 K and 82 K, named respectively as T1, T2, T3 and T4 transitions. Large values of magnetic field (>35 kOe) favor antiferromagnetic clusters and give rise to exchange bias effect. The different responses of T2 and T3 to field change, induces two non-identical isothermal entropy change (-ΔSM) peaks. The maximum values of -ΔSM occur in temperatures around T3 and reaches 8.2 J/kgK, for a magnetic field change of 50 kOe. Also, the presence of transitions T2 and T3 close to each other induces a table-like magnetocaloric effect (MCE) in a wide temperature range. Thus, the peculiar magnetic properties observed for DyMn2Si2 compound are interesting for low temperature magnetic refrigeration.

  5. Magnetic properties of Sm5Fe17/Fe composite magnets produced by spark plasma sintering method

    NASA Astrophysics Data System (ADS)

    Saito, Tetsuji; Miyoshi, Hiroya

    2012-04-01

    Mixtures of powdered Sm5Fe17 melt-spun ribbon and Fe powder were consolidated into bulk magnets by the spark plasma sintering (SPS) method. Although these bulk magnets consisted of the hard magnetic Sm5Fe17 and soft magnetic α-Fe phases, they had a smooth hysteresis loop and exhibited coercivity. Among the magnets studied, the Sm5Fe17/Fe composite magnet with 30%Fe showed a remanence of 94 emu/g with a coercivity of 2.9 kOe.

  6. Magnetic surfactants as molecular based-magnets with spin glass-like properties.

    PubMed

    Brown, Paul; Smith, Gregory N; Hernández, Eduardo Padrón; James, Craig; Eastoe, Julian; Nunes, Wallace C; Settens, Charles M; Hatton, T Alan; Baker, Peter J

    2016-05-05

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets.

  7. Enhancement of thermoelectric properties in benzene molecule junction by the magnetic flux

    NASA Astrophysics Data System (ADS)

    Li, Haidong; Wang, Yuan; kang, Xiubao; Liu, Shaohui; Li, Ruixue

    2017-02-01

    The thermoelectric properties through a benzene molecule with two metal leads are theoretically studied. The results reveal that the thermoelectric properties are strongly influenced by the magnetic flux. The reason for such a behavior is that the quantum interference caused by the magnetic field leads to the anti-resonance effect, which results in obvious thermoelectric effects. The value of Z T with a period of 1 for the magnetic flux and the magnitude of Z T may exceed 2 under some specific magnetic flux and onsite Coulomb interaction.

  8. Fe-DOPED Ga12N12 CLUSTERS: ELECTRONIC AND MAGNETIC PROPERTIES

    NASA Astrophysics Data System (ADS)

    Lu, Pengfei; Wu, Chengjie; Cong, Zixiang; Li, Yiluan; Zhang, Xianlong; Yu, Zhongyuan; Cao, Huawei

    2013-12-01

    In this paper, we have investigated the structural, electronic and magnetic properties of Ga12N12 cluster doped with monodoped and bidoped Fe atoms within the density functional theory (DFT). Substitutional, exohedral and endohedral doping are considered. It is observed that both monodoped and bidoped clusters tend to be in exohedral doping. Mulliken population analysis is performed to obtain the charge transfer and magnetic moment. The magnetic moment is mainly derived from 3d orbitals of Fe atom for all isomers, while the magnetic properties would rely on the Fe-Fe distance.

  9. Magnetic Properties of Surface Sediments in Small Temperate Lakes: Modern Analogues for Paleolimnologic Research

    NASA Astrophysics Data System (ADS)

    Lascu, I.; Plank, C.

    2007-12-01

    Magnetic properties of lake sediments are routinely measured as part of paleolimnological and paleoclimatic research. Basic parameters such as magnetic susceptibility (MS), anhysteretic remanent magnetization (ARM), and isothermal remanent magnetization (IRM) are used for correlating cores from different sites in the same basin, tracking erosion history and lake level changes, or investigating eutrophication and microbial processes. However, a detailed investigation of the syn-depositional processes that control the distribution of magnetic minerals across lake basins is lacking for most types of lake systems. In order to understand the main controls on environmental magnetic records, we systematically investigated the magnetic properties of surface sediments collected along transects in nine Minnesota lakes. The lakes are small (<1 sq. km), have simple morphologies, are hydrologically closed, and are distributed across an east-west moisture gradient, as well as a north-south temperature gradient. The structure of lake water columns was investigated by measuring temperature, specific conductivity, dissolved oxygen, and pH. Sediment composition was determined via loss on ignition (LOI). The magnetic properties of the sediments reflect the change in depositional environments from shallow to deep water, as defined in sedimentological context by LOI and sediment granulometry. All lake basins exhibit a characteristic pattern in terms of concentration (MS and IRM) and grain size (ARM/IRM) of magnetic minerals. Sediments above wave base (0.5 m) have high concentrations of coarse grained magnetic minerals. Below wave base, but in the thermally mixed layer, magnetic particles are finer-grained and present in lower concentrations. Profundal slope sediments are characterized by variable magnetic and compositional parameters, indicative of a dynamic sedimentological and geochemical environment. In the deep, anoxic regions, magnetic concentration increases again, associated

  10. Structural and magnetic properties of Mn50Fe50-xSnx (x=10, 15 and 20) alloys

    NASA Astrophysics Data System (ADS)

    Ghosh, Tanmoy; Agarwal, Sandeep; Mukhopadhyay, P. K.

    2016-11-01

    In this work we report measurements and comparisons of the structural, magnetic and transport properties of a series of Mn50Fe50-xSnx alloys (x=10, 15 and 20). We found that while the lower Sn composition sample stabilized in β-Mn-type crystallographic phase, the higher Sn composition alloys contained both β-Mn-type as well as Mn3Sn-type hexagonal DO19 phases. Through d.c. and a.c. magnetic property measurements we have established the existence of a ferromagnetic transition near room temperature followed by a spin reorientation at lower temperature in the Mn3Sn-type crystallographic phase of the alloys. Our resistivity study also revealed an interesting behavior with negative temperature coefficient (TCR) in these alloys.

  11. Modification and development of electrical and magnetic properties of PVA/PEO incorporated with MnCl2

    NASA Astrophysics Data System (ADS)

    Elashmawi, I. S.; Abdelrazek, E. M.; Hezma, A. M.; Rajeh, A.

    2014-02-01

    The electrical and magnetic properties PVA/PEO films incorporated with different weight percentage of MnCl2 prepared by casting technique were studied. The Magnetic properties were investigated by electron spin resonance (ESR) and vibrating sample magnetometer (VSM). The electrical conductivity was enhanced depends on both frequencies and temperatures indicate the existence of charge carriers transported by hopping through defect sites attributed to increase in the number of mobile charge carriers of Mn+2. The AC conduction mechanism and conduction parameters have been calculated according to the Correlated barrier hopping (CBH) model. ESR spectra reveals aggregated forms of Mn2+ ions are formed at higher concentration and isolated forms at lower concentration. VSM shows paramagnetic nature for pure MnCl2 and anti-ferromagnetic nature for doped samples due to overlapping of Mn d-states with valence band.

  12. Magnetic properties on the surface of FeAl stripes induced by nanosecond pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Kaiju, H.; Yoshida, Y.; Watanabe, S.; Kondo, K.; Ishibashi, A.; Yoshimi, K.

    2014-05-01

    We demonstrate the formation of magnetic nanostripes on the surface of Fe52Al48 induced by nanosecond pulsed laser irradiation and investigate their magnetic properties. The magnetic stripe consists of a disordered A2 phase of Fe-Al alloys with Al-oxide along the [110] direction on the (111)-oriented plane. According to the focused magneto-optical Kerr effect measurement, the coercive force of the magnetic stripe obeys the 1/cos θ law, where θ is the field rotation angle estimated from the stripe direction. Also, the jump field can be observed in the magnetic hysteresis loop. These results indicate that the magnetization reversal in the magnetic stripe originates from the domain pinning, showing that the magnetization rotates incoherently.

  13. Preparation and properties of the magnetic absorbent polymer via the chemical transformation process

    NASA Astrophysics Data System (ADS)

    Liu, Shengyu; Zhang, Suhong; Guo, Jianying; Wen, Jing; Qiao, Yan

    2017-01-01

    Magnetic polyacrylic acid sodium polymer (MPAAS) was prepared by chemical transformation method. Key parameters were investigated in the synthesis process of the magnetic polymer and an optimum preparation condition was gained. The structure of the magnetic polymer was characterized by X-ray diffraction (XRD), Fourier transform infrared spectrosocopy (FTIR) and scanning electron microscope (SEM). Magnetic property of the magnetic polymer was measured by the magnet and superconducting quantum interference device (SQUID). Both the swelling ratio and kinetics and the water retention ratio and kinetics were investigated. Based on the results, it can be gained that both swelling rate and equilibrium swelling rate were lowered after magnetization while the water retention ability of the magnetic polymer is stronger than that of the polymer.

  14. Magnetic properties and electronic structure of Mn-Ni-Ga magnetic shape memory alloys.

    PubMed

    D'Souza, Sunil Wilfred; Roy, Tufan; Barman, Sudipta Roy; Chakrabarti, Aparna

    2014-12-17

    Influence of disorder, antisite defects, martensite transition and compositional variation on the magnetic properties and electronic structure of Mn(2)NiGa and Mn(1+x)Ni(2-x)Ga magnetic shape memory alloys have been studied by using full potential spin-polarized scalar relativistic Korringa-Kohn-Rostocker (FP-SPRKKR) method. Mn(2)NiGa is ferrimagnetic and its total spin moment increases when disorder in the occupancy of MnNi (Mn atom in Ni position) is considered. The moment further increases when Mn-Ga antisite defect [1] is included in the calculation. A reasonable estimate of TC for Mn(2)NiGa is obtained from the exchange parameters for the disordered structure. Disorder influences the electronic structure of Mn(2)NiGa through overall broadening of the density of states and a decrease in the exchange splitting. Inclusion of antisite defects marginally broaden the minority spin partial DOS (PDOS), while the majority spin PDOS is hardly affected. For Mn(1+x)Ni(2-x)Ga where 1 ⩾ x ⩾ 0, as x decreases, Mn(Mn) moment increases while Mn(Ni) moment decreases in both austenite and martensite phases. For x ⩾ 0.25, the total moment of the martensite phase is smaller compared to the austenite phase, which indicates possible occurrence of inverse magnetocaloric effect. We find that the redistribution of Ni 3d- Mn(Ni) 3d minority spin electron states close to the Fermi level is primarily responsible for the stability of the martensite phase in Mn-Ni-Ga.

  15. Influence of hydrogen patterning gas on electric and magnetic properties of perpendicular magnetic tunnel junctions

    SciTech Connect

    Jeong, J. H.; Endoh, T.; Kim, Y.; Kim, W. K.; Park, S. O.

    2014-05-07

    To identify the degradation mechanism in magnetic tunnel junctions (MTJs) using hydrogen, the properties of the MTJs were measured by applying an additional hydrogen etch process and a hydrogen plasma process to the patterned MTJs. In these studies, an additional 50 s hydrogen etch process caused the magnetoresistance (MR) to decrease from 103% to 14.7% and the resistance (R) to increase from 6.5 kΩ to 39 kΩ. Moreover, an additional 500 s hydrogen plasma process decreased the MR from 103% to 74% and increased R from 6.5 kΩ to 13.9 kΩ. These results show that MTJs can be damaged by the hydrogen plasma process as well as by the hydrogen etch process, as the atomic bonds in MgO may break and react with the exposed hydrogen gas. Compounds such as MgO hydrate very easily. We also calculated the damaged layer width (DLW) of the patterned MTJs after the hydrogen etching and plasma processes, to evaluate the downscaling limitations of spin-transfer-torque magnetic random-access memory (STT-MRAM) devices. With these calculations, the maximum DLWs at each side of the MTJ, generated by the etching and plasma processes, were 23.8 nm and 12.8 nm, respectively. This result validates that the hydrogen-based MTJ patterning processes cannot be used exclusively in STT-MRAMs beyond 20 nm.

  16. Magnetic, magnetocaloric properties and phenomenological model in amorphous Fe60Ru20B20 alloy

    NASA Astrophysics Data System (ADS)

    Boutahar, A.; Lassri, H.; Hlil, E. K.

    2015-11-01

    Magnetic, magnetocaloric properties and phenomenological model of amorphous Fe60Ru20B20 alloy are investigated in detail. The amorphous alloy has been synthesized using melt spinning method. The magnetic transition nature undergoes a second-order magnetic phase transition from ferromagnetic to paramagnetic states with a Curie temperature of 254 K. Basis on the thermodynamic Maxwell's relation, magnetic entropy change (-ΔSM) is calculated. Further, we also report a theoretical investigation of the magnetocaloric effect using a phenomenological model. The best model parameters and their variation with temperature and the magnetic field were determined. The theoretical predictions are found to agree closely with experimental measurements.

  17. Some Peculiar Properties of Magnetic Clouds as Observed by the WIND Spacecraft

    NASA Technical Reports Server (NTRS)

    Berdichevsky, D.; Lepping, R. P.; Szabo, A.; Burlaga, L. F.; Thompson, B. J.; Lazarus, A. J.; Steinburg, J. T.; Mariani, F.

    1999-01-01

    We aimed at understanding the common characteristics of magnetic clouds, relevant to solar-interplanetary connections, but exceptional ones were noted and are stressed here through a short compendium. The study is based on analyses of 28 good or better events (Out of 33 candidates) as identified in WIND magnetic field and plasma data. These cloud intervals are provided by WIND-MFI's Website under the URL (http://lepmfi.gsfc.nasa.gov/mfi/mag_cloud_publ.html#table). The period covered is from early 1995 to November 1998. A force free, cylindrically symmetric, magnetic field model has been applied to the field data in usually 1-hour averaged form for the cloud analyses. Some of the findings are: (1) one small duration event turned out to have an approximately normal size which was due to a distant almost "skimming" passage by the spacecraft; (2) One truly small event was observed, where 10 min averages had to be used in the model fitting; it had an excellent model fit and the usual properties of a magnetic cloud, except it possessed a small axial magnetic flux; (3) One cloud ha a dual axial-field-polarity, in the sense that the "core" had one polarity and the annular region around it had an opposite polarity. This event also satisfied the model and with a ve3ry good chi-squared value. Some others show a hint of this dual polarity; (4) The temporal distribution of occurrence clouds over the 4 years show a dip in 1996; (5) About 50 % of the clouds had upstream shocks; any others had upstream pressure pulses; (6) The overall average speed (390 km/s) of the best 28 events is less than the normally quoted for the average solar wind speed (420 km/s) The average of central cloud speed to the upstream solar wind speed was not much greater than one (1.08), even though many of these clouds were drivers of interplanetary shocks. Cloud expansion is partly the reason for the existence of upstream shocks; (7) The cloud axes often (about 50 % of the time) revealed reasonable

  18. Large-scale properties of the interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Schatten, K. H.

    1972-01-01

    Early theoretical work of Parker is presented along with the observational evidence supporting his Archimedes spiral model. Variations present in the interplanetary magnetic field from the spiral angle are related to structures in the solar wind. The causes of these structures are found to be either nonuniform radial solar wind flow or the time evolution of the photospheric field. Coronal magnetic models are related to the connection between the solar magnetic field and the interplanetary magnetic field. Direct extension of the solar field-magnetic nozzle controversy is discussed along with the coronal magnetic models. Effects of active regions on the interplanetary magnetic field is discussed with particular reference to the evolution of interplanetary sectors. Interplanetary magnetic field magnitude variations are shown throughout the solar cycle. The percentage of time the field magnitude is greater than 10 gamma is shown to closely parallel sunspot number. The sun's polar field influence on the interplanetary field and alternative views of the magnetic field structure out of the ecliptic plane are presented. In addition, a variety of significantly different interplanetary field structures are discussed.

  19. Tunable Magnetic Properties of Heterogeneous Nanobrush: From Nanowire to Nanofilm

    PubMed Central

    2010-01-01

    With a bottom-up assemble technology, heterogeneous magnetic nanobrushes, consisting of Co nanowire arrays and ferromagnetic Fe70Co30 nanofilm, have been fabricated using an anodic aluminum oxide template method combining with sputtering technology. Magnetic measurement suggests that the magnetic anisotropy of nanobrush depends on the thickness of Fe70Co30 layer, and its total anisotropy originates from the competition between the shape anisotropy of nanowire arrays and nanofilm. Micromagnetic simulation result indicates that the switching field of nanobrush is 1900 Oe, while that of nanowire array is 2700 Oe. These suggest that the nanobrush film can promote the magnetization reversal processes of nanowire arrays in nanobrush. PMID:20672098

  20. Magnetic microstructure and magnetic properties of uniaxial itinerant ferromagnet Fe3GeTe2

    SciTech Connect

    León-Brito, Neliza; Bauer, Eric Dietzgen; Ronning, Filip; Thompson, Joe David; Movshovich, Roman

    2016-08-28

    Here, magnetic force microscopy was used to observe the magnetic microstructure of Fe3GeTe2 at 4 K on the (001) surface. The surface magnetic structure consists of a two-phase domain branching pattern that is characteristic for highly uniaxial magnets in the plane perpendicular to the magnetic easy axis. The average surface magnetic domain width Ds = 1.3 μm determined from this pattern, in combination with intrinsic properties calculated from bulk magnetization data (the saturation magnetization Ms = 376 emu/cm3 and the uniaxial magnetocrystalline anisotropy constant Ku = 1.46 × 107 erg/cm3), was used to determine the following micromagnetic parameters for Fe3GeTe2 from phenomenological models: the domain wall energy γw = 4.7 erg/cm2, the domain wall thickness δw = 2.5 nm, the exchange stiffness constant Aex = 0.95 × 10–7 erg/cm, the exchange length lex = 2.3 nm, and the critical single domain particle diameter dc = 470 nm.

  1. Preparation and magnetic properties of nickel nanowires by reduction in ethylene glycol medium under the influence of magnetic field

    NASA Astrophysics Data System (ADS)

    Sun, Wanshuo; Cheng, Junsheng; Li, Lankai; Chen, Shunzhong; Chang, Kun

    2017-01-01

    Nickel nanowires have successfully been fabricated through a simple liquid reduction in ethylene glycol medium with a 0.3T magnetic field applied. The effect of uniform magnetic field and solvent on the morphology and the crystal structure of magnetic nickel were studied. Scanning electron microscope images and transmission electron scope images s how that the effect of the external magnetic field on the morphology of nickel nanowires. X-ray diffraction shows the crystal structure of as-prepared products. And a energy disperse spectroscopy and a vibrating sample magnetometer are used to analyze the composition and static magnetic properties. The results show that the straight wires with an average diameter of about 100 nm and a length of several microns were obtained and mainly composed by fcc structure in the solvent of ethylene glycol. Magnetic measurements show that the saturation magnetization of the as-obtained products in a 0.3 T external magnetic field is 36 emu/g, less than that of bulk nickel crystal, and the coercivity of them is 186 emu/g, larger than that of bulk crystal with the mole ratio of sodium borohydride to nickel sulfate is 1:1000. This kind of nanowires array has potential applications with the special one-dimensional structures.

  2. Electronic and magnetic properties of manganite thin films with different compositions and its correlation with transport properties: An X-ray resonant magnetic scattering study

    DOE PAGES

    Singh, Surendra; Freeland, J. W.; Fitzsimmons, M. R.; ...

    2014-12-08

    Here, we present x-ray resonant magnetic dichroism and x-ray resonant magnetic scattering measurements of the temperature dependence of magnetism in Pr-doped La-Ca-Mn-O films grown on (110) NdGaO3 substrates. We observed thermal hysteresis of the ferromagnetism in one film that also showed large thermal hysteresis of ~18K in transport measurements. While in a second film of a different nominal chemistry, which showed very small thermal hysteresis ~3K in transport measurements, no thermal hysteresis of the ferromagnetism was observed. As a result, these macroscopic properties are correlated with evolution of surface magnetization across metal insulator transition for these films as observed bymore » soft x-ray resonant magnetic scattering measurements.« less

  3. Electronic and magnetic properties of manganite thin films with different compositions and its correlation with transport properties: An X-ray resonant magnetic scattering study

    SciTech Connect

    Singh, Surendra; Freeland, J. W.; Fitzsimmons, M. R.; Jeen, H.; Biswas, A.

    2014-12-08

    Here, we present x-ray resonant magnetic dichroism and x-ray resonant magnetic scattering measurements of the temperature dependence of magnetism in Pr-doped La-Ca-Mn-O films grown on (110) NdGaO3 substrates. We observed thermal hysteresis of the ferromagnetism in one film that also showed large thermal hysteresis of ~18K in transport measurements. While in a second film of a different nominal chemistry, which showed very small thermal hysteresis ~3K in transport measurements, no thermal hysteresis of the ferromagnetism was observed. As a result, these macroscopic properties are correlated with evolution of surface magnetization across metal insulator transition for these films as observed by soft x-ray resonant magnetic scattering measurements.

  4. Electronic and magnetic properties of manganite thin films with different compositions and its correlation with transport properties: An X-ray resonant magnetic scattering study

    SciTech Connect

    Singh, Surendra; Freeland, J. W.; Fitzsimmons, M. R.; Jeen, H.; Biswas, A.

    2014-12-14

    Here, we present x-ray resonant magnetic dichroism and x-ray resonant magnetic scattering measurements of the temperature dependence of magnetism in Pr-doped La-Ca-Mn-O films grown on (110) NdGaO{sub 3} substrates. We observed thermal hysteresis of the ferromagnetism in one film that also showed large thermal hysteresis of ∼18 K in transport measurements. While in a second film of a different nominal chemistry, which showed very small thermal hysteresis ∼3 K in transport measurements, no thermal hysteresis of the ferromagnetism was observed. These macroscopic properties are correlated with evolution of surface magnetization across metal insulator transition for these films as observed by soft x-ray resonant magnetic scattering measurements.

  5. The effect of nanocrystalline silicon host on magnetic properties of encapsulated iron oxide nanoparticles.

    PubMed

    Granitzer, P; Rumpf, K; Gonzalez-Rodriguez, R; Coffer, J L; Reissner, M

    2015-12-21

    The purpose of this work is a detailed comparison of the fundamental magnetic properties of nanocomposite systems consisting of Fe3O4 nanoparticle-loaded porous silicon as well as silicon nanotubes. Such composite structures are of potential merit in the area of magnetically guided drug delivery. For magnetic systems to be utilized in biomedical applications, there are certain magnetic properties that must be fulfilled. Therefore magnetic properties of embedded Fe3O4-nanoparticles in these nanostructured silicon host matrices, porous silicon and silicon nanotubes, are investigated. Temperature-dependent magnetic investigations have been carried out for four types of iron oxide particle sizes (4, 5, 8 and 10 nm). The silicon host, in interplay with the iron oxide nanoparticle size, plays a sensitive role. It is shown that Fe3O4 loaded porous silicon and SiNTs differ significantly in their magnetic behavior, especially the transition between superparamagnetic behavior and blocked state, due to host morphology-dependent magnetic interactions. Importantly, it is found that all investigated samples meet the magnetic precondition of possible biomedical applications of exhibiting a negligible magnetic remanence at room temperature.

  6. Electronic and magnetic properties of Mn-doped WSe2 monolayer under strain

    NASA Astrophysics Data System (ADS)

    Xin, Qianqian; Zhao, Xu; Wang, Tianxing

    2017-04-01

    Electronic and magnetic properties of Mn-doped WSe2 monolyer subject to isotropic strain are investigated using the first-principles methods based on the density functional theory. Our results indicate that Mn-doped WSe2 monolayer is a magnetic semiconductor nanomaterial with strong spontaneous magnetism without strain and the total magnetic moment of Mn-doped system is 1.038μB. We applied strain to Mn-doped WSe2 monolayer from -10% to 10%. The doped system transforms from magnetic semiconductor to half-metallic material from -10% to -2% compressive strain and from 2% to 6% tensile strain. The largest half-metallic gap is 0.450 eV at -2% compressive strain. The doped system shows metal property from 7% to 10%. Its maximum magnetic moment comes to 1.181μB at 6% tensile strain. However, the magnetic moment of system decreases to zero sharply when tensile strain arrived at 7%. Strain changes the redistribution of charges and arises to the magnetic effect. The coupling between the 3d orbital of Mn atom, 5d orbital of W atom and 4p orbital of Se atom is analyzed to explain the strong strain effect on the magnetic properties. Our studies predict Mn-doped WSe2 monolayers under strain to be candidates for thin dilute magnetic semiconductors, which is important for application in semiconductor spintronics.

  7. Preliminary Results of the Magnetic Properties Experiments on the Mars Exploration Rovers, Spirit and Opportunity

    NASA Astrophysics Data System (ADS)

    Goetz, W.; Athena Science Team

    Spirit and Opportunity each carry a set of Magnetic Properties Experiments to investigate the properties of the air-borne dust in the Martian atmosphere. The goal of the magnetic properties experiments is to provide information on how the dust once formed. The objectives are: a) To identify the magnetic mineral(s) in the dust, soil and rocks on Mars. b) To establish if the magnetic material is present in the form of nanosized possibly superparamagnetic crystallites embedded in the micrometer sized airborne dust particles. c) To establish if the magnets are culling a subset of strongly magnetic particles or if essentially all particles of the airborne dust are sufficiently magnetic to be attracted by the magnets. d) Detect compositional differences between the airborne dust and the soil and rock sites which are investigated at two landing sites. Two large magnets (called Capture and Filter magnet) are located such that the attracted dust can be studied by the Panoramic Camera (Pancam), the Mössbauer Spectrometer, the Alpha Particle X-ray Spectrometer (APXS), and the Microscopic Imager (MI). The dust settles on a circular surface of high purity aluminium (45 mm in diameter), where the central part (25 mm in diameter) is magnetically active. The Capture magnet was designed to be as strong as possible, whereas the strength of the Filter magnet was chosen such that it attracts mainly dust particles with high magnetic susceptibility (hence the name ``filter magnet''). A so-called Sweep Magnet experiment is placed near the Pancam Calibration Target. The purpose of the Sweep Magnet experiment is twofold: 1) to try to detect if any non-magnetic minerals are present in the atmospheric dust in any significant amount. 2) to provide a magnetically attracted dust layer suitable for spectroscopic investigation by the Pancam spectroscopy band pass filters. Each rover carries a Rock Abrasion Tool (RAT) on the robotic arm (IDD), which can be used to remove dust (by brushing) and

  8. Effect of La3+ Substitution on Electric, Dielectric and Magnetic Properties of Cobalt Nano-Ferrite

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Singh, M.

    2011-07-01

    Ultrafine particles of CoLaxFe2-xO4 (x = 0, 0.20) were prepared by using co-precipitation method. X-ray diffraction studies show that the samples have cubic spinel structure and average crystallite size of x = 0 and x = 0.2 are 49.84 nm and 27.73 nm respectively. Dielectric and magnetic properties have been studied by impedance analyzer and magnetic properties of the ferrite system were studied using VSM respectively. La3+ ions modulate significantly the electric, dielectric and magnetic properties of cobalt spinel ferrites.

  9. Microstructural, mechanical and magnetic properties of high-strength low-alloy steel

    NASA Astrophysics Data System (ADS)

    Narayan, S. Prakash; Rao, V.; Mohanty, O. N.

    1991-06-01

    Studies have been carried out on commercial grade high-strength low-alloy steel, microalloyed with Nb, V and Ti with a view to developing high-strength material with moderate soft magnetic properties. In order to obtain a suitable microstructure necessary for achieving the desired mechanical strength and magnetic properties, spheroidisation annealing (SA) as well as quenching and tempering (QT) treatments have been employed. At longer annealing or tempering time (⩾ 30 h), both the SA and QT samples have shown ample spheroidisation of carbides resulting in considerable improvement in the magnetic properties without much deterioration in mechanical strength.

  10. Magnetic and luminescent properties of vanadium-doped ZnSe crystals

    NASA Astrophysics Data System (ADS)

    Radevici, Ivan; Nedeoglo, Natalia; Sushkevich, Konstantin; Huhtinen, Hannu; Nedeoglo, Dmitrii; Paturi, Petriina

    2016-12-01

    Magnetic and photoluminescence properties of vanadium-doped ZnSe crystals with impurity concentrations varied by changing the V amount in the source material from 0.03 to 0.30 at% are studied in 5-300 K temperature range. Investigation of magnetic properties shows that the studied concentrations of vanadium impurity that should not disturb crystal lattice are insignificant for observing ferromagnetic behaviour even at low temperatures. The contribution of V impurity to edge emission and its influence on infra-red emission are discussed. Similarities of magnetic and luminescent properties induced by vanadium and other transition metal impurities are discussed.

  11. Influence of the structural properties on the pseudocritical magnetic behavior of single-wall ferromagnetic nanotubes

    NASA Astrophysics Data System (ADS)

    Salazar-Enríquez, C. D.; Restrepo-Parra, E.; Restrepo, J.

    2012-04-01

    In this work we address the influence of the crystalline structure, concretely when the system under study is formed by square or hexagonal unit cells, upon the magnetic properties and pseudocritical behavior of single-wall ferromagnetic nanotubes. We focus not only on the effect of the geometrical shape of the unit cell but also on their dimensions. The model employed is based on the Monte Carlo method, the Metropolis dynamics and a nearest neighbors classical Heisenberg Hamiltonian. Magnetization per magnetic site, magnetic susceptibility, specific heat and magnetic energy were computed. These properties were computed varying the system size, unit cell dimension and temperature. The dependence of the nearest neighbor exchange integral on the nanotubes geometrical characteristics is also discussed. Results revealed a strong influence of the system topology on the magnetic properties caused by the difference in the coordination number between square and hexagonal unit cell. Moreover, the nanotubes diameter influence on magnetic properties is only observed at very low values, when the distance between atoms is less than it, presented by the 2D sheet. On the other hand, it was concluded that the surface-related finite-size effects do not influence the magnetic nanotubes properties, contrary to the case of other nano-systems as thin films and nanoparticles among others.

  12. Magnetic properties, microstructure and mineralogical phases of technogenic magnetic particles (TMPs) in urban soils: Their source identification and environmental implications.

    PubMed

    Lu, Shenggao; Yu, Xiuling; Chen, Yuyin

    2016-02-01

    Magnetic measurement is an effective method to determine spatial distribution and the degree of heavy metal pollution and to identify various anthropogenic sources of heavy metals. The objectives of this investigation are to characterize the magnetic properties, microstructure and mineralogical phases of technogenic magnetic particles (TMPs) in urban soils and to discuss their potential environmental implications. The TMPs are separated from the urban topsoils of Luoyang city, China. The magnetic properties, morphology, and mineral phase of TMPs are studied using mineral magnetic measurement, scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction, and synchrotron-radiation-based microprobe. The content of TMPs in urban topsoils ranges from 0.05 to 1.95% (on average 0.32%). The magnetic susceptibility of TMPs ranges from 4559×10(-8) to 23,661×10(-8) m(3) kg(-1) (on average 13,637×10(-8) m(3) kg(-1)). Thermomagnetic and bulk X-ray diffraction analyses indicate that main magnetic minerals of TMPs are magnetite (Fe3O4) and hematite (α-Fe2O3). The morphology of TMPs observed by SEM includes three shape types: spherule, irregular-shaped, and aggregate particles. The size of spherical TMPs ranges from 30 to about 200 μm, with the largest percentage of 30-50 μm. Synchrotron-radiation-based microprobe (μ-XRF and μ-XRD) indicates that TMPs are enriched with heavy metals Pb, Cd, Zn, Cu, and Cr, which are incorporated into lattice or adsorbed on the surface of magnetite/hematite. The content of TMPs significantly relates with the Tomlinson Pollution Load Index (PLI) (R(2)=0.467), suggesting that it can be used as proxy indicator of degree of heavy metal contamination in urban soils. The magnetic properties, microstructure and mineralogical phases of TMPs can serve as the identification of pollution sources in urban soils.

  13. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Electronic and Magnetic Properties of Double Perovskite Ca2CrSbO6

    NASA Astrophysics Data System (ADS)

    Zhao, Yuan; Ni, Guang-Xin; Liu, Hui-Ping; Yi, Lin

    2010-01-01

    First-principles calculations have been performed for the study of the electronic hand structure and ferromagnetic properties of double perovskite Ca2CrSbO6. The density of states, total energy, spin magnetic moment, and charge density were calculated and analyzed in details. It is found that Ca2CrSbO6 has a stable ferromagnetic ground state and the spin magnetic moment per molecule is about 2.99μB. The chromium contributes the most in the total magnetic moments. The results indicate that Ca2CrSbO6 is half-metallic.

  14. Correlation of dielectric, electrical and magnetic properties near the magnetic phase transition temperature of cobalt zinc ferrite.

    PubMed

    Pradhan, Dhiren K; Kumari, Shalini; Puli, Venkata S; Das, Proloy T; Pradhan, Dillip K; Kumar, Ashok; Scott, J F; Katiyar, Ram S

    2016-12-21

    Multiferroic composite structures, i.e., composites of magnetostrictive and piezoelectric materials, can be envisioned to achieve the goal of strong room-temperature ME coupling for real practical device applications. Magnetic materials with high magnetostriction, high Néel temperature (TN), high resistivity and large magnetization are required to observe high ME coupling in composite structures. In continuation of our investigations on suitable magnetic candidates for multiferroic composite structures, we have studied the crystal structure, dielectric, transport, and magnetic properties of Co0.65Zn0.35Fe2O4 (CZFO). Rietveld refinement of X-ray diffraction patterns confirms the phase purity with a cubic crystal structure with the (Fd3[combining macron]m) space group; however, we have found a surprisingly large magneto-dielectric anomaly at the Néel temperature, unexpected for a cubic structure. The presence of mixed valences of Fe(2+)/Fe(3+) cations is probed by X-ray photoelectron spectroscopy (XPS), which supports the catonic ordering-mediated large dielectric response. Large dielectric permittivity dispersion with a broad anomaly is observed in the vicinity of the magnetic phase transition temperature (TN) of CZFO suggesting a strong correlation between dielectric and magnetic properties. The evidence of strong spin-polaron coupling has been established from temperature dependent dielectric, ac conductivity and magnetization studies. The ferrimagnetic-paramagnetic phase transition of CZFO has been found at ∼640 K, which is well above room temperature. CZFO exhibits low loss tangent, a high dielectric constant, large magnetization with soft magnetic behavior and magnetodielectric coupling above room temperature, elucidating the possible potential candidates for multiferroic composite structures as well as for multifunctional and spintronics device applications.

  15. Magnetic Properties of Restacked 2D Spin 1/2 honeycomb RuCl3 Nanosheets.

    PubMed

    Weber, Daniel; Schoop, Leslie M; Duppel, Viola; Lippmann, Judith M; Nuss, Jürgen; Lotsch, Bettina V

    2016-06-08

    Spin 1/2 honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still in demand. Here, we report the exfoliation of the magnetic semiconductor α-RuCl3 into the first halide monolayers and the magnetic characterization of the spin 1/2 honeycomb arrangement of turbostratically stacked RuCl3 monolayers. The exfoliation is based on a reductive lithiation/hydration approach, which gives rise to a loss of cooperative magnetism due to the disruption of the spin 1/2 state by electron injection into the layers. The restacked, macroscopic pellets of RuCl3 layers lack symmetry along the stacking direction. After an oxidative treatment, cooperative magnetism similar to the bulk is restored. The oxidized pellets of restacked single layers feature a magnetic transition at TN = 7 K if the field is aligned parallel to the ab-plane, while the magnetic properties differ from bulk α-RuCl3 if the field is aligned perpendicular to the ab-plane. The deliberate introduction of turbostratic disorder to manipulate the magnetic properties of RuCl3 is of interest for research in frustrated magnetism and complex magnetic order as predicted by the Kitaev-Heisenberg model.

  16. Optical and electronic properties of quantum dots with magnetic impurities

    NASA Astrophysics Data System (ADS)

    Govorov, Alexander O.

    2008-10-01

    The article discusses some of the recent results on semiconductor quantum dots with magnetic impurities. A single Mn impurity incorporated in a quantum dot strongly changes the optical response of a quantum-dot system. A character of Mn-carrier interaction is very different for II-VI and III-V quantum dots (QDs). In the II-VI QDs, a Mn impurity influences mostly the spin-structure of an exciton. In the III-V dots, a spatial localization of hole by a Mn impurity can be very important, and ultimately yields a totally different spin structure. A Mn-doped QD with a variable number of mobile carriers represents an artificial magnetic atom. Due to the Mn-carrier interaction, the order of filling of electronic shells in the magnetic QDs can be very different to the case of the real atoms. The "periodic" table of the artificial magnetic atoms can be realized in voltage-tunable transistor structures. For the electron numbers corresponding to the regime of Hund's rule, the magnetic Mn-carrier coupling is especially strong and the magnetic-polaron states are very robust. Magnetic QD molecules are also very different to the real molecules. QD molecules can demonstrate spontaneous breaking of symmetry and phase transitions. Single QDs and QD molecules can be viewed as voltage-tunable nanoscale memory cells where information is stored in the form of robust magnetic-polaron states. To cite this article: A.O. Govorov, C. R. Physique 9 (2008).

  17. Electronic and magnetic properties of Si substituted Fe3Ge

    DOE PAGES

    Shanavas, Kavungal Veedu; McGuire, Michael A.; Parker, David S.

    2015-09-23

    Using first principles calculations we studied the effect of Si substitution in the hexagonal Fe3Ge. We find the low temperature magnetic anisotropy in this system to be planar and originating mostly from the spin-orbit coupling in Fe-d states. Reduction of the unitcell volume reduces the in-plane magnetic anisotropy, eventually turning it positive which reorients the magnetic moments to the axial direction. We find that substituting Ge with the smaller Si ions also reduces the anisotropy, potentially enhancing the region of stability of the axial magnetization, which is beneficial for magnetic applications. Thus our experimental measurements on samples of Fe3Ge1–xSix confirmmore » these predictions and show that substitution of about 6% of the Ge with Si increases by approximately 35 K the temperature range over which anisotropy is uniaxial.« less

  18. Impact of low level praseodymium substitution on the magnetic properties of YCrO3 orthochromites

    NASA Astrophysics Data System (ADS)

    Kumar, Surendra; Coondoo, Indrani; Rao, Ashok; Lu, Bo-Han; Kuo, Yung-Kang; Kholkin, Andrei L.; Panwar, Neeraj

    2017-04-01

    Praseodymium (Pr) modified yttrium orthochromites (YCrO3 with Pr =0% and 5% at Y-sites) have been investigated with the aim of exploring the impact of low level Pr substitution on the magnetic properties including magnetization reversal, spin reorientation, and exchange bias of YCrO3 compound. The samples exhibit a distorted orthorhombic structure with Pnma space group. A negative magnetization (or magnetization reversal) was observed under zero-field cooled (ZFC) mode for the pristine YCrO3 sample, whereas such a feature disappeared with a 5% Pr substitution. In addition, the Pr-doped samples exhibited a spin reorientation behaviour which was absent in the pristine sample. Most interestingly, the ZFC magnetic hysteresis loops revealed a left and upward shift, resembling a negative exchange bias effect. These results indicate the effectiveness of low level doping in tailoring the magnetic properties of orthochromites.

  19. Magnetic properties of double perovskite La2BMnO6 (B = Ni or Co) nanoparticles

    SciTech Connect

    Mao, Yuanbing; Parsons, Jason; McCloy, John S.

    2013-03-31

    Double perovskite La2BMnO6 (B = Ni and Co) nanoparticles with average particle size of ~50 nm were synthesized using a facile, environmentally friendly, scalable molten-salt reaction at 700 °C in air. Their structural and morphological properties were characterized by x-ray diffraction and transmission electron microscopy. Magnetic properties were evaluated using dc magnetic M-T and M-H, and ac magnetic susceptibility versus frequency, temperature, and field. The magnetization curve shows a paramagnetic-ferromagnetic transition at TC ~275 and 220 K for La2NiMnO6 (LNMO) and La2CoMnO6 (LCMO) nanoparticles, respectively. ac susceptibility revealed that the LCMO had a single magnetic transition indicative of Co2+-O2--Mn4+ ordering, whereas the LNMO showed more complex magnetic behavior suggesting a re-entrant spin glass.

  20. Magnetic properties of double perovskite La2BMnO6 (B = Ni or Co) nanoparticles.

    PubMed

    Mao, Yuanbing; Parsons, Jason; McCloy, John S

    2013-06-07

    Double perovskite La2BMnO6 (B = Ni and Co) nanoparticles with average particle size of ~50 nm were synthesized using a facile, environmentally friendly, and scalable molten-salt reaction at 700 °C in air. Their structural and morphological properties were characterized by X-ray diffraction and transmission electron microscopy. Their magnetic properties were evaluated and compared using dc magnetic M-T and M-H, and ac magnetic susceptibility versus frequency, temperature, and field for the first time. The dc magnetization curves show paramagnetic-ferromagnetic transitions at TC∼ 275 and 220 K for La2NiMnO6 (LNMO) and La2CoMnO6 (LCMO) nanoparticles, respectively. ac susceptibility revealed that the LCMO nanoparticles had a single magnetic transition indicative of Co(2+)-O(2-)-Mn(4+) ordering, whereas the LNMO nanoparticles showed more complex magnetic behaviors suggesting a re-entrant spin glass.

  1. Magnetic properties of bcc-Fe(001)/C₆₀ interfaces for organic spintronics.

    PubMed

    Tran, T Lan Anh; Cakır, Deniz; Wong, P K Johnny; Preobrajenski, Alexei B; Brocks, Geert; van der Wiel, Wilfred G; de Jong, Michel P

    2013-02-01

    The magnetic structure of the interfaces between organic semiconductors and ferromagnetic contacts plays a key role in the spin injection and extraction processes in organic spintronic devices. We present a combined computational (density functional theory) and experimental (X-ray magnetic circular dichroism) study on the magnetic properties of interfaces between bcc-Fe(001) and C(60) molecules. C(60) is an interesting candidate for application in organic spintronics due to the absence of hydrogen atoms and the associated hyperfine fields. Adsorption of C(60) on Fe(001) reduces the magnetic moments on the top Fe layers by ∼6%, while inducing an antiparrallel magnetic moment of ∼-0.2 μ(B) on C(60). Adsorption of C(60) on a model ferromagnetic substrate consisting of three Fe monolayers on W(001) leads to a different structure but to very similar interface magnetic properties.

  2. Magnetic properties of Apollo 14 breccias and their correlation with metamorphism.

    NASA Technical Reports Server (NTRS)

    Gose, W. A.; Pearce, G. W.; Strangway, D. W.; Larson, E. E.

    1972-01-01

    The magnetic properties of Apollo 14 breccias can be explained in terms of the grain size distribution of the interstitial iron which is directly related to the metamorphic grade of the sample. In samples 14049 and 14313 iron grains less than 500 A in diameter are dominant as evidenced by a Richter-type magnetic aftereffect and hysteresis measurements. Both samples are of lowest metamorphic grade. The medium metamorphic-grade sample 14321 and the high-grade sample 14312 both show a logarithmic time-dependence of the magnetization indicative of a wide range of relaxation times and thus grain sizes, but sample 14321 contains a stable remanent magnetization whereas sample 14312 does not. This suggests that small multidomain particles (less than 1 micron) are most abundant in sample 14321 while sample 14312 is magnetically controlled by grains greater than 1 micron. The higher the metamorphic grade, the larger the grain size of the iron controlling the magnetic properties.

  3. Magnetic and magnetocaloric properties of Er-Co-Al thin-film alloys

    NASA Astrophysics Data System (ADS)

    Kim, Miri; Kim, Jong-Woo; Lim, Sang Ho

    2015-11-01

    Er-Co-Al thin films with the compositions of ErCo1.52Al0.36, ErCo1.69Al0.76, and ErCo1.87Al0.16 were fabricated by magnetron-sputtering, and their magnetic and magnetocaloric properties were characterized in the asdeposited state and post-annealed state at 1073 K. The X-ray diffraction results indicate that the microstructure in the as-deposited state consists of an amorphous phase, which then transforms into a cubic Laves phase with C15 symmetry on annealing. The phase transformation, however, is incomplete, evidenced by the existence of Co precipitates and some oxides of Er and Al in the annealed samples. A compensation-like behavior is observed in the as-deposited samples, probably due to the sperimagnetic structure, but it disappears after annealing. The magnetic entropy change is largest for the annealed ErCo1.87Al0.16 sample, in which the composition is closest to the pseudo-binary Er(Co,Al)2 compound. The observed value, however, is rather small (3.2 J/kg K in a field sweep of 0-50 kOe), due the incomplete phase transformation from the amorphous to the cubic Laves phase during annealing.

  4. Tuning electronic properties of bilayer Bernal graphene nanoribbon by magnetic modulation

    NASA Astrophysics Data System (ADS)

    Li, T. S.; Hsieh, C. T.; Chang, S. C.

    2014-12-01

    This study shows that the electronic properties of bilayer Bernal graphene nanoribbon can be effectively tuned by a spatially modulated magnetic field. The electronic structures are significantly influenced by varying the field strength or the period of the modulated field. In addition, there exists competition between the magnetic confinement effect and the quantum confinement effect. The density of states (DOS) exhibits many asymmetric square-root divergent peaks due to the oscillatory parabolic subbands. These peaks can be classified into primary and secondary ones. The number, height, and energy of the peaks depend sensitively on the strength and the period of the modulated field. The evolution of the DOS peak energy with the field strength and the period is explored. The energies of primary peaks first exhibit linear, then square-root dependence on the field strength. On the other hand, the field strength dependence of the secondary peaks is purely square root. These theoretical predictions can be validated by STS or magneto-transmission measurements.

  5. Effect of Mg-Zr substitution and microwave processing on magnetic properties of barium hexaferrite

    NASA Astrophysics Data System (ADS)

    Sharma, Manju; Kashyap, Subhash C.; Gupta, H. C.

    2014-09-01

    The effect of substitution of Mg-Zr for Fe in M-type barium hexaferrite (BHF) and of processing technique on the magnetic properties and microstructure has been reported in the present paper. Significant changes in magnetic properties have been observed on substituting Fe ions by Mg and Zr ions in M-type barium hexaferrite, i.e. BaFe12O19 as well as by single mode microwave processing. The single mode microwave processing of the undoped sample reduced the coercivity to nearly 25% of the value for the sintered sample along with the enhancement in magnetization, thereby making it suitable for memory devices. The improvement in magnetic properties is explained on the basis of microstructure. The addition of substituents, though assisted in the formation of single phase, it, however, degraded the magnetization besides decreasing the coercivity, possibly due to substitution at the octahedral sites.

  6. Magnetic properties of bcc Iron surfaces and the influence of the chemical environment: electronic structure calculations.

    PubMed

    Fischer, Guntram; Gerber, Iann C

    2015-01-14

    We have investigated the magnetic properties of low-indexed iron surfaces and the influence of the chemical environment on these properties. We have considered the (1 0 0), (1 1 0), (1 1 1), (2 1 1) and (3 1 0) surfaces, both, bare and with the presence of adsorbates. These were chosen to mimic realistic chemical synthesis environments, being H, Cl, HCl, NH3, NH4Cl, or CH3COOH. We have found an increased magnetization at all bare surfaces. Upon H adsorption the magnetization is generally reduced, but still above the bulk value. All other ligands and their dissociated parts alter the magnetic properties of the surfaces only weakly. Our calculations do not indicate that ligands are responsible for experimental observations of Fe nanoparticles with average magnetizations below the bulk value.

  7. Magnetic properties of bcc Iron surfaces and the influence of the chemical environment: electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Fischer, Guntram; Gerber, Iann C.

    2015-01-01

    We have investigated the magnetic properties of low-indexed iron surfaces and the influence of the chemical environment on these properties. We have considered the (1 0 0), (1 1 0), (1 1 1), (2 1 1) and (3 1 0) surfaces, both, bare and with the presence of adsorbates. These were chosen to mimic realistic chemical synthesis environments, being H, Cl, HCl, NH3, NH4Cl, or CH3COOH. We have found an increased magnetization at all bare surfaces. Upon H adsorption the magnetization is generally reduced, but still above the bulk value. All other ligands and their dissociated parts alter the magnetic properties of the surfaces only weakly. Our calculations do not indicate that ligands are responsible for experimental observations of Fe nanoparticles with average magnetizations below the bulk value.

  8. Composition dependence of magnetic properties in perpendicularly magnetized epitaxial thin films of Mn-Ga alloys

    NASA Astrophysics Data System (ADS)

    Mizukami, S.; Kubota, T.; Wu, F.; Zhang, X.; Miyazaki, T.; Naganuma, H.; Oogane, M.; Sakuma, A.; Ando, Y.

    2012-01-01

    Mn-Ga binary alloys show strong magnetism and large uniaxial magnetic anisotropy even though these alloys do not contain any noble, rare-earth metals or magnetic elements. We investigate the composition dependence of saturation magnetization MS and uniaxial magnetic anisotropy Ku in epitaxial films of MnxGa1-x alloys (x˜0.5-0.75) grown by magnetron sputtering. The MS values decrease linearly from approximately 600 to 200 emu/cm3 with increasing x, whereas the Ku values decrease slightly from approximately 15 to 10 Merg/cm3 with increasing x. These trends are distinct from those for known tetragonal hard magnets obtained in a limited composition range in Mn-Al and Fe-Pt binary alloys. These data are analyzed using a localized magnetic moment model.

  9. Preparation and Magnetic Properties of MnBi-based Hard/Soft Composite Magnets

    SciTech Connect

    Ma, Yilong; Liu, Xubo; Gandha, Kinjal; Vuong, Nguyen V.; Yang, Y. B.; Yang, Jinbo; Poudyal, Narayan; Cui, Jun; Liu, J.Ping

    2014-05-07

    Bulk anisotropic composite magnets based on MnBi/Co(Fe) exhibiting the different morphology of the soft magnetic phase were prepared by powder metallurgy processing. First, single-phase MnBi bulk magnets were produced using a maximum energy product [(BH)m] of 6.3 MGOe at room temperature. The nanoscale soft phase with the different morphology was then added to form a composite magnet. It was observed that addition of magnetic soft-phase nanoparticles and nanoflakes causes a dramatic coercivity reduction. However, the addition of soft magnetic phase nanowires enhanced the composite magnetization without sacrificing the coercivity. Nevertheless, a kink was still observed on the demagnetization curves and the coercivity decreased when the soft-phase content was larger than 10 wt. %, which was caused by the agglomeration of the soft phase nanowires that also led to a decreased degree of texture.

  10. Quantifying the motion of magnetic particles in excised tissue: Effect of particle properties and applied magnetic field

    NASA Astrophysics Data System (ADS)

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-11-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 μm diameter) with four different coatings (starch, chitosan, lipid, and PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields.

  11. QUANTIFYING THE MOTION OF MAGNETIC PARTICLES IN EXCISED TISSUE: EFFECT OF PARTICLE PROPERTIES AND APPLIED MAGNETIC FIELD

    PubMed Central

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-01-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 µm diameter) with four different coatings (starch, chitosan, lipid, PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields. PMID:26120240

  12. QUANTIFYING THE MOTION OF MAGNETIC PARTICLES IN EXCISED TISSUE: EFFECT OF PARTICLE PROPERTIES AND APPLIED MAGNETIC FIELD.

    PubMed

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-11-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 µm diameter) with four different coatings (starch, chitosan, lipid, PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields.

  13. Study of magnetic, structural and magnetocaloric properties of La0.6Pr0.4Mn2Si2 under high pressures and magnetic field

    NASA Astrophysics Data System (ADS)

    Kaštil, J.; Arnold, Z.; Isnard, O.; Skourski, Y.; Kamarád, J.; Itié, J. P.

    2017-02-01

    The structural, magnetic and magnetocaloric properties of La0.6Pr0.4Mn2Si2 compound were measured in wide range of temperature, magnetic field and hydrostatic pressure. The structural study up to 10 GPa confirmed the existence of critical Mn-Mn distance 0.2883 nm for the ferromagnetic to antiferromagnetic transition at room temperature. The results demonstrated the crucial role of the volume in the suppression of the ferromagnetic phase above the transition temperature T1=168 K under pressure. The huge pressure shift of the transition temperature T1, dT1/dp=230 K/GPa, was observed. Based on our magnetization measurement the low temperature transition at T2=30 K is connected with reorientation of Mn moment and the rare-earth sublattice is not ordered in this case. The direct magnetocaloric measurement showed moderate values of the adiabatic temperature change connected with the magnetic transition at Tc and T1 and confirmed the first order character of the transition at T1 and second order character of the transition at Tc.

  14. Synthesis and magnetic properties of hard/soft SrFe12O19/Ni0.7Zn0.3Fe2O4 nanocomposite magnets

    NASA Astrophysics Data System (ADS)

    Radmanesh, M. A.; Seyyed Ebrahimi, S. A.

    2012-09-01

    Magnetic nanocomposite SrFe12O19/Ni0.7Zn0.3Fe2O4 powders with different weight fractions of the Ni0.7Zn0.3Fe2O4 soft ferrite were synthesized by a combination of the sol-gel self-propagation and glyoxilate precursor methods. The results of magnetic measurements revealed the higher Mr/Ms ratio for the nanocomposites than that for the single phase SrFe12O19 which proves the existence of the intergrain exchange coupling between hard and soft magnetic phases with the exchange spring behavior. The highest Mr/Ms ratio of 0.63 was obtained in the composite consisting of 80 wt% of SrFe12O19 and 20 wt% Ni0.7Zn0.3Fe2O4. The microstructural studies of this sample exhibited the average dimensions of hard and soft phases about 20 nm and 15 nm, respectively which are small enough for strong exchange coupling according to the theoretical studies. The variations of the reduced remanence (Mr/Ms) with increasing the weight fraction of the soft phase could be also explained by the role of the exchange and dipolar interactions in tuning the magnetic properties of the nanocomposites.

  15. Magnetic properties of cherts from the Basque-Cantabrian basin and surrounding regions: archeological implications

    NASA Astrophysics Data System (ADS)

    Larrasoaña, Juan; Beamud, Elisabet; Olivares, Maitane; Murelaga, Xabier; Tarriño, Andoni; Baceta, Juan; Etxebarria, Nestor

    2016-04-01

    We present the first rock magnetic study of archeologically-relevant chert samples from the Basque-Cantabrian basin (BCB) and surrounding regions, which was conducted in order to test the usefulness of non-destructive magnetic properties for assessing chert quality, distinguishing source areas, and identifying heated samples in the archeological record. Our results indicate that the studied BCB cherts are diamagnetic and have very low amounts of magnetic minerals. The only exception is the chert of Artxilondo, which has a mean positive magnetic susceptibility associated with larger concentrations of magnetic minerals. But even in this case, the magnetic susceptibility is within the lower range of other archeologically-relevant cherts elsewhere, which indicates that the studied BCB cherts can be considered as flint. The similar mean values for all magnetic properties, along with their associated large standard deviations, indicates that rock magnetic methods are of limited use for sourcing different types of flint except in some specific contexts involving the Artxilondo flint. With regards to the identification of chert heating in the archeological record, our results indicate only a minor magnetic enhancement of BCB natural flint samples upon heating, which we attribute to the low amount of non-silica impurities. In any case, the diamagnetic behavior of most BCB natural flints, along with the local use only of the Artxilondo type, suggests that any flint tool within the core of the BCB with positive magnetic susceptibility values is likely to have been subjected to heating for improving its knapping properties. Further studies are necessary to better identify the type, origin and grain size of magnetic minerals in BCB natural flints, and to apply non-destructive magnetic properties to flint tools in order to identify the use of heat treatment in the BCB archeological record.

  16. Modulation of homochiral Dy(III) complexes: single-molecule magnets with ferroelectric properties.

    PubMed

    Li, Xi-Li; Chen, Chun-Lai; Gao, Yu-Liang; Liu, Cai-Ming; Feng, Xiang-Li; Gui, Yang-Hai; Fang, Shao-Ming

    2012-11-12

    Homochiral Dy(III) complexes: by changing the ligand-to-metal ratio, enantiomeric pairs of a Dy(III) complex of different nuclearity could be obtained. The mono- and dinuclear complexes exhibit characteristics of single-molecule magnets and different slow magnetic relaxation processes. In addition, the dinuclear complexes exhibit ferroelectric behavior, thus representing the first chiral polynuclear lanthanide-based single-molecule magnets with ferroelectric properties.

  17. Magnetic properties of a new intermetallic compound Ho2Ni2Pb

    NASA Astrophysics Data System (ADS)

    Muñoz-Sandoval, E.; Chinchure, A. D.; Hendrikx, R. W. A.; Mydosh, J. A.

    2001-10-01

    Single-phase, textured samples of a new orthorhombic intermetallic compound Ho2Ni2Pb have been fabricated (space group Cmmm). Here the bulk magnetic properties are presented as determined via magnetization, susceptibility, heat capacity and resistivity measurements. The results exhibit two distinct magnetic transitions and large metamagnetic effects. Such behaviour is related to the unusual rare-earth symmetry of the highly anisotropic crystal structure.

  18. Magnetic and Magnetooptical Properties of Co-Al Alloy Thin Films on a Nanostructured Substrate

    NASA Astrophysics Data System (ADS)

    Nakatani, Morio; Suzuki, Yoshihisa; Sumi, Satoshi; Tanemura, Sakae

    2005-01-01

    We investigated magnetic and magnetooptical properties of Co-Al magnetic thin films on a nanostructured substrate. The nanostructured substrate was made of polycarbonate by injection molding. The stamper was made by electron beam cutting. The nanostructured substrate contributed a perpendicular magnetic anisotropy component to the film and decreased the reflectance of the film. The Kerr rotation angle on the nanostructured substrate was greater than that on a glass substrate.

  19. Magnetic Anomalies and Rock Magnetic Properties Related to Deep Crustal Rocks of the Athabasca Granulite Terrane, Northern Canada

    NASA Astrophysics Data System (ADS)

    Brown, L. L.; Williams, M. L.

    2010-12-01

    The Athabasca granulite terrane in northernmost Saskatchewan, Canada is an exceptional exposure of lower crustal rocks having experienced several high temperature events (ca 800C) during a prolonged period of deep-crustal residence (ca 1.0 GPa) followed by uplift and exhumation. With little alteration since 1.8 Ga these rocks allow us to study ancient lower crustal lithologies. Aeromagnetic anomalies over this region are distinct and complex, and along with other geophysical measurements, define the Snowbird Tectonic zone, stretching NE-SW across northwestern Canada, separating the Churchill province into the Hearne (mid-crustal rocks, amphibolite facies) from the Rae (lower crust rocks, granulite facies). Distinct magnetic highs and lows appear to relate roughly to specific rock units, and are cut by mapped shear zones. Over fifty samples from this region, collected from the major rock types, mafic granulites, felsic granulites, granites, and dike swarms, as well as from regions of both high and low magnetic anomalies, are being used to investigate magnetic properties. The intention is to investigate what is magnetic in the lower crust and how it produces the anomalies observed from satellite measurements. The samples studied reveal a wide range of magnetic properties with natural remanent magnetization ranging from an isolated high of 38 A/m to lows of 1 mA/m. Susceptibilities also range over several orders of magnitude, from 1 to 1 x10-4 SI. Magnetite is identified in nearly all samples using both low and high temperature measurements, but concentrations are generally very low. Hysteresis properties on 41 samples reveal nearly equal numbers of samples represented by PSD and MD grains, with a few samples (N=6) plotting in or close to the SD region. Low temperature measurements indicate that most samples contain magnetite, showing a marked Verway transition around 120K. Also identified in nearly half of the samples is pyrrhotite, noted by low temperature

  20. The formation of sunspot penumbra. Magnetic field properties

    NASA Astrophysics Data System (ADS)

    Rezaei, R.; Bello González, N.; Schlichenmaier, R.

    2012-01-01

    Aims: We study the magnetic flux emergence and formation of a sunspot penumbra in the active region NOAA 11024. Methods: We simultaneously observed the Stokes parameters of the photospheric iron lines at 1089.6 nm with the TIP and 617.3 nm with the GFPI spectropolarimeters along with broad-band images using G-band and Ca ii K filters at the German VTT. The photospheric magnetic field vector was reconstructed from an inversion of the measured Stokes profiles. Using the AZAM code, we converted the inclination from line-of-sight (LOS) to the local reference frame (LRF). Results: Individual filaments are resolved in maps of magnetic parameters. The formation of the penumbra is intimately related to the inclined magnetic field. No penumbra forms in areas with strong magnetic field strength and small inclination. Within 4.5 h observing time, the LRF magnetic flux of the penumbra increases from 9.7 × 1020 to 18.2 × 1020 Mx, while the magnetic flux of the umbra remains constant at ~3.8 × 1020 Mx. Magnetic flux in the immediate surroundings is incorporated into the spot, and new flux is supplied via small flux patches (SFPs), which on average have a flux of 2-3 × 1018 Mx. The spot's flux increase rate of 4.2 × 1016 Mx s-1 corresponds to the merging of one SFP per minute. We also find that, during the formation of the spot penumbra, a) the maximum magnetic field strength of the umbra does not change; b) the magnetic neutral line keeps the same position relative to the umbra; c) the new flux arrives on the emergence side of the spot while the penumbra forms on the opposite side; d) the average LRF inclination of the light bridges decreases from 50° to 37°; and e) as the penumbra develops, the mean magnetic field strength at the spot border decreases from 1.0 to 0.8 kG. Conclusions: The SFPs associated with elongated granules are the building blocks of structure formation in active regions. During the sunspot formation, their contribution is comparable to the

  1. Magnetic properties, Lyapunov exponent and superstability of the spin-{1}/{2} Ising-Heisenberg model on a diamond chain

    NASA Astrophysics Data System (ADS)

    Ananikian, N.; Hovhannisyan, V.

    2013-05-01

    The exactly solvable spin-{1}/{2} Ising-Heisenberg model on a diamond chain has been considered. We have found the exact results for the magnetization using the recursion relation method. The existence of the magnetization plateau has been observed at one third of the saturation magnetization in the antiferromagnetic case. Some ground-state properties of the model are examined. At low temperatures, the system has two ferrimagnetic (FRI1 and FRI2) phases and one paramagnetic (PRM) phase. Lyapunov exponents for the various values of the exchange parameters and temperatures have been analyzed. It has also been shown that the maximal Lyapunov exponent exhibits plateau. Lyapunov exponents exhibit different behavior for two ferrimagnetic phases. We have found the existence of the supercritical point for the multi-dimensional rational mapping of the spin-{1}/{2} Ising-Heisenberg model on a diamond chain for the first time in the absence of the external magnetic field and T→0 in the antiferromagnetic case.

  2. Porous Silicon Nanocomposites with Combined Hard and Soft Magnetic Properties

    NASA Astrophysics Data System (ADS)

    Rumpf, Klemens; Granitzer, Petra; Michor, Herwig

    2016-09-01

    Magnetic nanostructures of two ferromagnetic metals have been combined within porous silicon, and the magnetic switching behavior of the resulting porous silicon/metal nanocomposite has been modified by varying the arrangement. The two magnetic materials are Ni and Co, whereas Co is the magnetic harder one. These "hard/soft" magnetic nanocomposites have been achieved by two different routes. On the one hand, double-sided porous silicon has been used whereas one side has been filled with Ni nanostructures and the other one with Co nanostructures. On the other hand, Ni and Co have been deposited within one porous layer alternatingly. The filling of the pores has been carried out by electrodeposition with varying the deposition parameters. In systems which offer two distinct slopes of the hysteresis curves due to the different saturation behavior of the two types of deposited metal, magnetic exchange coupling is not present. For samples which show smooth hysteresis curves exchange, coupling between the Ni and Co nanostructures seems to be present. The aim is to control especially the structure size of the soft and the hard magnetic materials and the distance between them at the nanoscale to optimize exchange coupling resulting in a maximum energy product.

  3. Complex Nano-objects Displaying Both Magnetic and Catalytic Properties: A Proof of Concept for Magnetically Induced Heterogeneous Catalysis.

    PubMed

    Meffre, Anca; Mehdaoui, Boubker; Connord, Vincent; Carrey, Julian; Fazzini, Pier Francesco; Lachaize, Sébastien; Respaud, Marc; Chaudret, Bruno

    2015-05-13

    Addition of Co2(Co)9 and Ru3(CO)12 on preformed monodisperse iron(0) nanoparticles (Fe(0) NPs) at 150 °C under H2 leads to monodisperse core-shell Fe@FeCo NPs and to a thin discontinuous Ru(0) layer supported on the initial Fe(0) NPs. The new complex NPs were studied by state-of-the-art transmission electron microscopy techniques as well as X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. These particles display large heating powers (SAR) when placed in an alternating magnetic field. The combination of magnetic and surface catalytic properties of these novel objects were used to demonstrate a new concept: the possibility of performing Fischer-Tropsch syntheses by heating the catalytic nanoparticles with an external alternating magnetic field.

  4. The magnetic properties of one-dimensional spin-1 ferromagnetic Heisenberg model in a magnetic field within Callen approximation

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Wei; Chen, Yuan; Song, Chuang-Chuang; Wu, You; Ding, Hai-Ling

    2011-03-01

    The effect of magnetic field h on the magnetic properties of the one-dimensional spin-1 ferromagnetic Heisenberg model is studied by the double-time Green's function method. The magnetization and susceptibility are obtained within the Callen approximation. The zero-field susceptibility is as a decreasing function of the temperature T. The magnetization m increases in the whole field region, but the susceptibility maximum χ(Tm) decreases. The position Tm of the susceptibility maximum is both solved analytically and fits well to be a power law Tm∼hγ at low fields and to be linear increasing at high fields. The height χ(Tm) decreases as a power law χ(Tm)∼h with h increasing. The exponents (γ,β) obtained in our results agree with the other theoretical results. Our results are roughly in agreement with the results obtained in the experiment of Ni(OH)(NO3)H2O.

  5. Microstructure and magnetic properties of backward extruded NdFeB ring magnets by the CAPA process

    NASA Astrophysics Data System (ADS)

    Kim, Hyoung-Tae; Kim, Yoon-Bae

    2004-06-01

    The inhomogeneity in microstructure and magnetic properties of a ring magnet prepared by backward extrusion with a current-applied pressure-assisted process has been investigated. The initial part (top part) of a ring magnet prepared by back extrusion shows a high coercivity which is comparable to the raw powder. It exhibits isotropic characteristics along the three orthogonal directions probably due to small deformation. The last part (bottom part) of the ring magnet has a a low coercivity with large grains because high current flows through the pressurized punches during the whole deformation process as to increase the temperature and grain growth. The middle part is under an appropriate deformation with short time exposure at high temperature, therefore it maintains a relatively high remanent polarization with high coercivity.

  6. Rock Magnetic Properties and Magnetic Petrology of Hawaiian and Icelandic Basalts: a key for the Understanding of high Crustal Magnetizations on Earth and Earth-like Planets?

    NASA Astrophysics Data System (ADS)

    Kontny, A.

    2007-05-01

    The rock magnetic behavior and Fe-Ti oxide petrology of subaerial and submarine basalts have been extensively studied over the last decades because of their importance in understanding Earth's magnetic anomalies. Combined rock magnetic and magneto-mineralogic investigations on different basalt lithologies from scientific drillings on Hawaii and Iceland have shown that multiple processes, related to the geodynamic setting, the emplacement and cooling history and the alteration history affected the texture and composition of the originally homogeneous titanomagnetite and caused significant variation in rock magnetic properties like magnetic susceptibility, Curie temperature, coercivity force or natural remanent magnetization (NRM). Hawaiian basalts from the scientific drillings HSDP-2, SOH-1 and SOH-4 have e.g. NRM intensities between <1 and 13 A/m, which is distinctly lower than those measured on several localities on Iceland. Surface samples from fissure eruptions of the Reykjanes peninsula show 4 - 32 A/m and drill cores from the Stardalur central volcano (subaerial basaltic lava flows) show very high values up to 120 A/m. Although the main controlling factors for these high NRM values seem to be the primary magma composition and cooling history, secondary processes like high-temperature decomposition reactions and hydrothermal alteration can also play a role. During the latter process, titanomagnetite is altered to titanomaghemite and furthermore to (cation-deficient) magnetite. Secondary magnetite can be additionally formed due to hydrothermal activity increasing the total magnetization. Modifications of rock magnetic properties related to these magnetic petrology changes will be discussed for basalts of different strong magnetization in relation to geologic processes.

  7. The effects of 10 to >160 GPa shock on the magnetic properties of basalt and diabase

    NASA Astrophysics Data System (ADS)

    Bezaeva, N. S.; Swanson-Hysell, N. L.; Tikoo, S. M.; Badyukov, D. D.; Kars, M.; Egli, R.; Chareev, D. A.; Fairchild, L. M.; Khakhalova, E.; Strauss, B. E.; Lindquist, A. K.

    2016-11-01

    Hypervelocity impacts within the solar system affect both the magnetic remanence and bulk magnetic properties of planetary materials. Spherical shock experiments are a novel way to simulate shock events that enable materials to reach high shock pressures with a variable pressure profile across a single sample (ranging between ˜10 and >160 GPa). Here we present spherical shock experiments on basaltic lava flow and diabase dike samples from the Osler Volcanic Group whose ferromagnetic mineralogy is dominated by pseudo-single-domain (titano)magnetite. Our experiments reveal shock-induced changes in rock magnetic properties including a significant increase in remanent coercivity. Electron and magnetic force microscopy support the interpretation that this coercivity increase is the result of grain fracturing and associated domain wall pinning in multidomain grains. We introduce a method to discriminate between mechanical and thermal effects of shock on magnetic properties. Our approach involves conducting vacuum-heating experiments on untreated specimens and comparing the hysteresis properties of heated and shocked specimens. First-order reversal curve (FORC) experiments on untreated, heated, and shocked specimens demonstrate that shock and heating effects are fundamentally different for these samples: shock has a magnetic hardening effect that does not alter the intrinsic shape of FORC distributions, while heating alters the magnetic mineralogy as evident from significant changes in the shape of FORC contours. These experiments contextualize paleomagnetic and rock magnetic data of naturally shocked materials from terrestrial and extraterrestrial impact craters.

  8. (110) grain growth and magnetic properties of thin grain-oriented 3% silicon steel sheets

    SciTech Connect

    Nakano, Masaki; Fukunaga, Hirotoshi; Ishiyama, Kazushi; Arai, Ken Ichi

    1999-09-01

    (110) grain growth and magnetic properties in thin grain-oriented silicon sheets with ultimately low loss were investigated. A final-annealing at 1150 C for 20 min enables us to obtain the thin sheets covered with only (110) grains and consequently the magnetic induction at 800 A/m, B{sub 8} reached 1.9 T.

  9. Ab initio calculations on the magnetic properties of transition metal complexes

    SciTech Connect

    Bodenstein, Tilmann; Fink, Karin

    2015-12-31

    We present a protocol for the ab initio determination of the magnetic properties of mono- and polynuclear transition metal compounds. First, we obtain the low lying electronic states by multireference methods. Then, we include spin-orbit coupling and an external magnetic field for the determination of zero-field splitting and g-tensors. For the polynuclear complexes the magnetic exchange coupling constants are determined by a modified complete active space self consistent field method. Based on the results of the ab initio calculations, magnetic data such as magnetic susceptibility or magnetization are simulated and compared to experimental data. The results obtained for the polynuclear complexes are further analysed by calculations on model complexes where part of the magnetic centers are substituted by diamagnetic ions. The methods are applied to different Co and Ni containing transition metal complexes.

  10. The magnetic and multiferroic properties in BiMnO3

    NASA Astrophysics Data System (ADS)

    Zhai, Liang-Jun; Wang, Huai-Yu

    2017-03-01

    In this paper, the magnetic and multiferroic properties in the multiferroic material BiMnO3 are studied. A Heisenberg type Hamiltonian for BiMnO3 is proposed, in which the nearest and farther neighbors are considered. Thermodynamic quantities such as magnetization and magnetic susceptibility for different magnetic orderings under high pressure or magnetic field are calculated, and the simulation results fit the experimental results. Farther neighboring exchanges can result in the coexistence of the ferromagnetic ordering and certain antiferromagnetic ordering with no centrosymmetry. Our study demonstrates that the BiMnO3 should be the type-II multiferroic, and the ferromagnetic and ferroelectric orderings could coexist. The magnetic field control of ferroelectric polarization is also studied. The ferroelectric polarization is always suppressed by the external magnetic field.

  11. Surface morphology and magnetic property of wrinkled FeGa thin films fabricated on elastic polydimethylsiloxane

    NASA Astrophysics Data System (ADS)

    Zhang, Shuanglan; Zhan, Qingfeng; Yu, Ying; Liu, Luping; Li, Huihui; Yang, Huali; Xie, Yali; Wang, Baomin; Xie, Shuhong; Li, Run-Wei

    2016-03-01

    We investigated the surface morphology and the magnetic property of wrinkled Fe81Ga19 (FeGa) thin films fabricated in two different processes onto elastic polydimethylsiloxane (PDMS) substrates. The films obtained by directly depositing Ta and FeGa layers on a pre-strained PDMS substrate display a sinusoidally wrinkled surface and a weak magnetic anisotropy. The wavelength and amplitude of the sinusoidal morphology linearly increase with the metallic layer thickness, while the magnetic anisotropy decreases with increasing FeGa thickness. The other films grown by depositing FeGa layer on a wrinkled Ta/PDMS surface show a remarkable uniaxial magnetic anisotropy. The strength of magnetic anisotropy increases with increasing FeGa thickness. The magnetic anisotropy can be ascribed to the surface anisotropy, the magnetostrictive anisotropy, and the shape anisotropy caused, respectively, by the magnetic charges on wavy morphology, the residual mechanical stress, and the inhomogeneous thickness of FeGa films.

  12. Magnetic properties of spin-1/2 Fermi gases with ferromagnetic interaction

    NASA Astrophysics Data System (ADS)

    Wang, Baobao; Qin, Jihong; Guo, Huaiming

    2015-10-01

    We investigate the magnetic properties of spin-1/2 charged Fermi gases with ferromagnetic coupling via mean-field theory, and find the interplay among the paramagnetism, diamagnetism and ferromagnetism. Paramagnetism and diamagnetism compete with each other. When increasing the ferromagnetic coupling the spontaneous magnetization occurs in a weak magnetic field. The critical ferromagnetic coupling constant of the paramagnetic phase to ferromagnetic phase transition increases linearly with the temperature. Both the paramagnetism and diamagnetism increase when the magnetic field increases. It reveals the magnetization density bar M increases firstly as the temperature increases, and then reaches a maximum. Finally the magnetization density bar M decreases smoothly in the high temperature region. The domed shape of the magnetization density bar M variation is different from the behavior of Bose gas with ferromagnetic coupling. We also find the curve of susceptibility follows the Curie-Weiss law, and for a given temperature the susceptibility is directly proportional to the Landé factor.

  13. Magnetic properties and large magnetocaloric effect in Laves phase metallic compound

    NASA Astrophysics Data System (ADS)

    Gao, Tian; Qi, Ningning; Zhang, Yufeng; Zhou, Tao

    2014-12-01

    We investigated the magnetic properties and magnetocaloric effect of C15 Laves phase TbMn1.6Fe0.4 by magnetization and heat capacity measurements. A sharp second-order magnetic Tb-Tb ordering transition at Curie temperature TC ~ 120 K and a short-range Fe-Fe ordering transition at ~230 K are observed. Around TC, the compound shows a large magnetocaloric effect with no obvious thermal and magnetic hysteresis loss. The maximum value of magnetic entropy change reaches 8.72 J kg-1 K-1 for a magnetic field change ΔH = 7 T over a wide temperature range. The obtained relative cooling power reaches 184, 560, and 803 J kg-1 for ΔH = 2, 5 and 7 T, respectively. Large reversible magnetocaloric effect and the wide operating temperature range indicate that TbMn1.6Fe0.4 could be a promising candidate for magnetic refrigeration.

  14. Magnetic properties driven by local structure in quasi-1D Ising chain system cobaltate system

    NASA Astrophysics Data System (ADS)

    Kim, Bongjae; Kim, Beom Hyun; Kim, Kyoo; Choi, Hong Chul; Park, Sang-Yeon; Jeong, Y.-H.; Min, B. I.

    2012-02-01

    Using ab-initio band structure method and the microscopic model calculation, the origins of the large orbital magnetic moment and unique magnetic anisotropy in the quasi-1D magnetic cobaltate, α-CoV2O6, is investigated. Unique crystal electric field effect in α-CoV2O6 is combined with the strong spin-orbit coupling, results in intriguing magnetic properties of the system. Based on the estimated strengths of the intra- and the inter-chain exchange interaction, experimentally found 1/3 magnetization plateau in the MH curve can be attributed to spin-flop mechanism. Origin of the reduced magnetic entropy behavior is found to be the strong uniaxial magnetic anisotropy in the quasi-1D Ising chain system.

  15. Gebel Kamil Iron Meteorite: 57Fe Mössbauer Spectroscopy and Magnetic Properties Data

    NASA Astrophysics Data System (ADS)

    Dos Santos, E.; Munayco, P.; Gattacceca, J.; Rochette, P.; Scorzelli, R. B.; Folco, L.

    2014-09-01

    In this work, we present magnetic properties data along with mineralogical characterization by 57Fe Mössbauer spectroscopy for a shrapnel of Gebel Kamil meteorite, in order to evaluate the thermal/shock history revealed by these techniques.

  16. Electronic and magnetic properties of Fe and Mn doped two dimensional hexagonal germanium sheets

    SciTech Connect

    Soni, Himadri R. Jha, Prafulla K.

    2014-04-24

    Using first principles density functional theory calculations, the present paper reports systematic total energy calculations of the electronic properties such as density of states and magnetic moment of pristine and iron and manganese doped two dimensional hexagonal germanium sheets.

  17. Magnetic Cellulose Nanocrystal Based Anisotropic Polylactic Acid Nanocomposite Films: Influence on Electrical, Magnetic, Thermal, and Mechanical Properties.

    PubMed

    Dhar, Prodyut; Kumar, Amit; Katiyar, Vimal

    2016-07-20

    This paper reports a single-step co-precipitation method for the fabrication of magnetic cellulose nanocrystals (MGCNCs) with high iron oxide nanoparticle content (∼51 wt % loading) adsorbed onto cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopic studies confirmed that the hydroxyl groups on the surface of CNCs (derived from the bamboo pulp) acted as anchor points for the adsorption of Fe3O4 nanoparticles. The fabricated MGCNCs have a high magnetic moment, which is utilized to orient the magnetoresponsive nanofillers in parallel or perpendicular orientations inside the polylactic acid (PLA) matrix. Magnetic-field-assisted directional alignment of MGCNCs led to the incorporation of anisotropic mechanical, thermal, and electrical properties in the fabricated PLA-MGCNC nanocomposites. Thermomechanical studies showed significant improvement in the elastic modulus and glass-transition temperature for the magnetically oriented samples. Differential scanning calorimetry (DSC) and XRD studies confirmed that the alignment of MGCNCs led to the improvement in the percentage crystallinity and, with the absence of the cold-crystallization phenomenon, finds a potential application in polymer processing in the presence of magnetic field. The tensile strength and percentage elongation for the parallel-oriented samples improved by ∼70 and 240%, respectively, and for perpendicular-oriented samples, by ∼58 and 172%, respectively, in comparison to the unoriented samples. Furthermore, its anisotropically induced electrical and magnetic properties are desirable for fabricating self-biased electronics products. We also demonstrate that the fabricated anisotropic PLA-MGCNC nanocomposites could be laminated into films with the incorporation of directionally tunable mechanical properties. Therefore, the current study provides a novel noninvasive approach of orienting nontoxic bioderived CNCs in the presence of low

  18. Magnetic properties of the Bay of Islands ophiolite suite and implications for the magnetization of oceanic crust

    USGS Publications Warehouse

    Swift, B. Ann; Johnson, H. Paul

    1984-01-01

    Rock magnetic properties, opaque mineralogy, and degree of metamorphism were determined for 101 unoriented samples from the North Arm and Blow-Me-Down massifs of the Bay of Islands ophiolite complex, Newfoundland. The weathered and metamorphosed extrusive basalt samples have a weak, secondary magnetization arising from oxidation and exsolution of ilmenite of unknown origin. The initial magnetization of the underlying sheeted dike complex appears to have been destroyed by hydrothermal alteration soon after formation. The magnetic intensity of the gabbroic samples increases as the degree of alteration increases, with the highly altered upper metagabbros having an average intensity of 3×10−3 emu/c3. Because magnetization of the metagabbro samples is related to nonpervasive, variable alteration, these crustal units are unlikely to make a significant contribution to lineated magnetic anomalies. A compilation of our results and other studies suggests a model in which oceanic crust magnetization results from an upper extrusive basalt source layer, roughly 600 m thick, with no contribution from a deeper source layer recognizable from these Bay of Islands data.

  19. Effect of milling time on magnetic properties and structures of bulk Sm-Co/{alpha}-(Fe, Co) nanocomposite magnets

    SciTech Connect

    Shen, Y.; Huang, M. Q.; Turgut, Z.; Lucas, M. S.; Michel, E.; Horwath, J. C.

    2012-04-01

    Bulk Sm-Co/{alpha}-(Fe,Co) nanocomposite magnets were fabricated by hot pressing composite powders prepared by high-energy ball milling of magnetically hard SmCo{sub 5} powder and magnetically soft Fe powder. The bulk magnets had a nanocomposite structure consisting of Sm-Co matrix (1:5 H and 1:7 H phases) and {alpha}-(Fe,Co) phases. The Fe-Co particles were distributed uniformly in the Sm-Co matrix. The milling time strongly affects the structures and the magnetic properties of the bulk magnets. Increasing milling time led to a decrease of the amount of 1:5 H phase, an increase in the phase fraction of the 1:7 H phase, and a decrease in the amount of soft phase, which resulted in an increase in magnetization and a decrease in coercivity. Scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) analyses revealed that inter-diffusion took place between the Sm-Co matrix and Fe particles during the processing.

  20. Effect of milling time on magnetic properties and structures of bulk Sm-Co/α-(Fe, Co) nanocomposite magnets

    NASA Astrophysics Data System (ADS)

    Shen, Y.; Huang, M. Q.; Turgut, Z.; Lucas, M. S.; Michel, E.; Horwath, J. C.

    2012-04-01

    Bulk Sm-Co/α-(Fe,Co) nanocomposite magnets were fabricated by hot pressing composite powders prepared by high-energy ball milling of magnetically hard SmCo5 powder and magnetically soft Fe powder. The bulk magnets had a nanocomposite structure consisting of Sm-Co matrix (1:5 H and 1:7 H phases) and α-(Fe,Co) phases. The Fe-Co particles were distributed uniformly in the Sm-Co matrix. The milling time strongly affects the structures and the magnetic properties of the bulk magnets. Increasing milling time led to a decrease of the amount of 1:5 H phase, an increase in the phase fraction of the 1:7 H phase, and a decrease in the amount of soft phase, which resulted in an increase in magnetization and a decrease in coercivity. Scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) analyses revealed that inter-diffusion took place between the Sm-Co matrix and Fe particles during the processing.