Showing papers on "Magnetic anisotropy published in 1994"
TL;DR: In this paper, the magnetic anisotropy energy constant increases with decreasing particle size, presumably because of the influence of surface anisotropic properties, such as magnetic hyperfine fields.
Abstract: Nanoparticles of metallic iron on carbon supports have been studied insitu by use of M\"ossbauer spectroscopy. The magnetic anisotropy energy constant increases with decreasing particle size, presumably because of the influence of surface anisotropy. Chemisorption of oxygen results in formation of a surface layer with magnetic hyperfine fields similar to those of thicker passivation layers, and with a ferromagnetic coupling to the spins in the core of the particles. In contrast, thicker passivation layers have a noncollinear spin structure.
648 citations
TL;DR: In this article, a simple model accounts for the time-scale dependence of coercivity in terms of the thermally assisted crossing of an energy barrier whose height is reduced by the applied field.
Abstract: Coercivity and other experimental measures of switching field depend upon the time scale of interest. This time‐scale dependence has practical importance in magnetic recording, because the effective time scales of writing and storage are very different. A simple model accounts for the time‐scale dependence of coercivity in terms of the thermally assisted crossing of an energy barrier whose height is reduced by the applied field. Fitting this barrier‐crossing model to data provides an estimate of the volume that must switch magnetization direction in overcoming the barrier. The assumption of Stoner–Wohlfarth reversal is used to obtain an initial estimate of the dependence of the barrier height on the field. With some adjustment of the resulting energy expression, the model gives good agreement between calculated switching volume and actual particle volume for advanced recording particles of three types: acicular oxide, acicular metal, and barium ferrite platelets. The model can be used to estimate minimum ...
465 citations
TL;DR: The properties of spin-1/2 antiferromagnetic chains with various types of random exchange coupling are studied via an asymptotically exact decimation renormalization-group transformation, which is a generalization of that introduced by Dasgupta and Ma.
Abstract: The properties of spin-1/2 antiferromagnetic chains with various types of random exchange coupling are studied via an asymptotically exact decimation renormalization-group transformation, which is a generalization of that introduced by Dasgupta and Ma. Random-singlet phases occur in which each spin is paired with one other spin that may be very far away; more exotic phases also occur. The behavior of typical and mean correlation functions is analyzed and found to be very different, with very small sets of spins dominating the latter at long distances as well as the low-temperature thermodynamics. Some of the phase transitions that occur between antiferromagnetically ordered phases and random singlet or other antiferromagnetic phases are also analyzed. For example, if a small uniaxial anisotropy perturbation is added to a random Heisenberg antiferromagnetic chain, a transition occurs from a random-singlet phase to an Ising antiferromagnetic phase, as the anisotropy changes sign from easy plane to easy axis. The staggered magnetization vanishes at the transition with critical exponent \ensuremath{\beta}=8/(1+ \ensuremath{\surd}7 ). Possible implications for the properties of random quantum magnetic systems in higher dimensions are briefly discussed.
453 citations
TL;DR: The easy axis of magnetization in Ni/Cu(001) films exhibits a crossover from in-plane to perpendicular orientation with increasing film thickness, which can be extrapolated from thin-film data.
Abstract: The easy axis of magnetization in Ni/Cu(001) films exhibits a crossover from in-plane to perpendicular orientation with increasing film thickness. This reorientation at \ensuremath{\approxeq}7 monolayers, observed by ferromagnetic resonance, is substantially different from previous findings for Fe and Co films and can be extrapolated from thin-film data. The artificial lattice structure of Ni on Cu yields within magnetoelasticity theory a volume anisotropy of 29 \ensuremath{\mu}eV/atom agreeing perfectly with experiment. In thinner films the surface anisotropy of -77 \ensuremath{\mu}eV/atom dominates.
331 citations
TL;DR: In this article, the magnetotransport properties of five binary metallic systems (Co-Ag, Fe-Ag and Fe-Pt) were systematically investigated using a combination of structural analysis involving transmission electron microscopy, x-ray diffraction, and magnetic characterization.
Abstract: We have systematically investigated the magnetotransport properties of five binary metallic systems (Co-Ag, Fe-Ag, Fe-Cu, Fe-Au, and Fe-Pt). Except for Fe-Pt, which forms a solid-solution in sputtering synthesis, all other systems exhibit giant magnetoresistance (GMR) effects and are immiscible or almost immiscible alloys. Using a combination of structural analysis involving transmission electron microscopy, x-ray diffraction, and magnetic characterization, we have revealed the microstructure for some of the granular alloys where the magnetic particles are embedded in a nonmagnetic matrix. Across the whole particle volume fraction range (0\ensuremath{\le}x\ensuremath{\le}100 %), a universal peak of GMR at x=0.15\ensuremath{\sim}0.25 is uncovered in every granular system. The suppression of GMR in the high-x region is attributed to the percolation effect, which also causes a concurrent reduction in magnetic coercivity. Magnetic particle size, a variable under thermal annealing, is another important factor affecting GMR. We have observed correlations between transport properties and particle size, supporting the view that magnetic scattering occurs predominantly on the surface of the particles. Quantitatively, both the field and temperature dependence of the GMR effect can be well accounted for by a modified exchange interaction model. Spin-wave excitation and electron-phonon interaction at finite temperatures are detrimental to GMR. Superparamagnetism and large magnetic anisotropy impede the saturation process of GMR, but have no effect on the saturated value of GMR.
212 citations
TL;DR: In this article, the template effects in molecular beam epitaxy (MBE) of ferromagnetic MnAs thin films on (001) GaAs substrates were studied, and it was shown that the growth direction of the thin film grown on this surface is [1100] and the easy magnetization axis was along the [1120] of MnAs and the [110] of GaAs, 90° different with respect to the substrate.
Abstract: We have studied template effects in molecular beam epitaxy (MBE) of ferromagnetic MnAs thin films on (001) GaAs substrates. When As2 flux was first supplied without Mn flux on the (001) GaAs prior to the MnAs growth, the surface reconstruction was disordered c(4×4), a more As‐rich surface than c(4×4). The growth direction of the MnAs thin film grown on this surface is [1100] and the easy magnetization axis was found to be along the [1120] of MnAs and the [110] of GaAs. In contrast, when one monolayer of Mn was first deposited on the c(4×4) GaAs surface and then As2 flux was supplied to grow MnAs, the growth direction of the MnAs thin film was found to be mainly [1101], and the easy magnetization axis was along the [1120] of MnAs and the [110] of GaAs, 90° different with respect to the substrate. These results indicate the importance of the very first monolayer in controlling the epitaxial orientation and magnetic properties of epitaxial ferromagnetic MnAs thin films.
174 citations
Abstract: The spin-polarized band calculations including spin-orbit interaction for L1 0 -FePt and CoPt ordered alloys have been performed with LMTO-ASA method in the frame of local spin density functional approximation. It has been shown that strong uniaxial magnetic anisotropy of both alloys is brought about by a large spin-orbit coupling of Pt atom and a strong hybridization of Pt d bands with highly polarized Fe (Co) d bands. The obtained magnetocrystalline anisotropy energy (MAE) is about 16×10 6 J/m 3 for FePt and 9×10 6 J/m 3 for CoPt. It is also found that both MAE's have a trend of increase with increasing axial ratio c / a in the vicinity of measured c / a . This can be regarded as being associated with the behavior that the MAE's decrease with increasing band filling.
173 citations
TL;DR: In this article, the basic physical and magnetic properties of Fe and Co based amorphous wires are summarised, together with post-production treatments used to modify the properties of the as-quenched alloys.
172 citations
TL;DR: The magnetocrystalline anisotropy energy of a free-standing Co monolayer has been calculated by means of the linear mufBn-tin orbital method in the atomic-spheres approximation and the results are used to analyze those obtained previously for Co&/Pdz and Coq/Ag2 multilayers.
Abstract: The magnetocrystalline anisotropy energy of a free-standing [111]Co monolayer has been calculated &om Srst principles by means of the linear mufBn-tin orbital method in the atomic-spheres approximation. The results are used to analyze those obtained previously for [111]Co&/Pdz and Coq/Ag2 multilayers. Although the magnetization of both mnltilayers is predicted to be oriented perpendicular to the plane of the multilayers, the easy axis of the Co monolayer is predicted to lie in plane. These results can be understood in terms of the energy bands at the high-symmetry points of the Brillouin zone only. Co&/Pdz is found to have a perpendicular anisotropy because the Fermi energy is located much closer to states which have mainly Co d ~ „~ and d „character than it does in the free-standing monolayer. These states are degenerate in the absence of spin-orbit coupling as a consequence of the threefold symmetry. The anisotropy energy is enhanced by the hybridization of the Pd d and Co d states and the large value of the Pd d spin-orbit coupling parameter. The smaller perpendicular magnetic anisotropy of a Co&/Agz multilayer can be attributed to the increased band 6lling of the Co d band structure, as well as to a smaller hybridization between Ag and Co d states.
164 citations
TL;DR: In this article, a phase diagram is presented to explain the transition from a magnetically split spectrum to a doublet or singlet when the temperature is varied, and zero-field-cooled magnetization measurements show a maximum at a certain temperature.
Abstract: Mossbauer spectra of samples containing nano-sized magnetic particles exhibit a transition from a magnetically split spectrum to a doublet or singlet when the temperature is varied, and zero-field-cooled magnetization measurements show a maximum at a certain temperature. When the interactions are weak these features can be explained by superparamagnetic blocking, but in the case of strong interactions they can be explained by ordering of the magnetic moments. A phase diagram, which elucidates these possibilities, is presented.
159 citations
TL;DR: In this paper, a model based on quadrupolar ordering of localized $f$ electrons was proposed to explain the 17.5 K phase transition of U${\mathrm{Ru}}_{2}$${Si}}
Abstract: We propose a model based on quadrupolar ordering of localized $f$ electrons to explain the 17.5 K phase transition of U${\mathrm{Ru}}_{2}$${\mathrm{Si}}_{2}$. The tiny staggered magnetic moment observed by neutron scattering is interpreted as a weak secondary effect associated to the symmetry-breaking perturbation. The model is able to account for the observed behavior of the linear and nonlinear susceptibilities throughout the transition. A connection with the quadrupolar Kondo theory is proposed.
TL;DR: In this paper, the magnetic moment and susceptibility of diamond, graphite along and perpendicular to the c axis, and carbon nanotubes are reported as a function of magnetic field (0H55 kOe) and temperature (4.5 KT310 K).
Abstract: Measurements of the magnetic moment and susceptibility of diamond, graphite along and perpendicular to the c axis, ${\mathrm{C}}_{60}$, and carbon nanotubes are reported as a function of magnetic field (0H55 kOe) and temperature (4.5 KT310 K). The data on ${\mathrm{C}}_{60}$ are diamagnetic, confirm previous results, and show the influence of the phase transition near 260 K. The data on the nanotubes were taken on a sample containing a distribution of tubes with diameters in the 2--10 nm range, and reveal a mostly diamagnetic behavior with a magnetic field and temperature dependence different from graphite.
TL;DR: In this paper, the authors discuss two methods that quantify the contribution of different groups to the AMS: (1) comparative measurements of the magnetic susceptibility in low fields and high fields and (2) heating curves from 77 K to room temperature (low temperature magnetic susceptibility, LTMS).
TL;DR: In this article, magnetic anisotropies and misfit strain relaxations have been investigated in Cu/Ni-wedge/Cu (100) and (111) sandwiches deposited by molecular beam epitaxy on singlecrystal Cu substrates.
Abstract: Magnetic anisotropies and misfit strain relaxations have been investigated in Cu/Ni‐wedge/Cu (100) and (111) sandwiches deposited by molecular beam epitaxy on single‐crystal Cu substrates. Our results reveal a clear distinction in the nature of the measured anisotropy at Ni thicknesses below and above the critical value tc, where the growth becomes incoherent. Below tc, coherent lattice strain modifies only the volume anisotropy, while interface anisotropy is Neel type; above tc, magnetoelastic effects are found to contribute to the interface anisotropy.
TL;DR: In this paper, the magnetic properties of high anisotropy Sm(Co1−xCux)5 phases were determined experimentally at 300 K in the range x < 0.6.
Abstract: The magnetic characteristics of high‐anisotropy Sm(Co1−xCux)5 phases are determined experimentally at 300 K in the range x<0.6. The saturation magnetization Ms decreases and vanishes for SmCo2Cu3. Identical behaviors of Ms and Curie temperature TC versus x are observed in the range x<0.6. For significant Cu substitution rate (x≳0.35), the decrease of the anisotropy field (HA) when x increases is strong. For lower Cu contents, huge values of anisotropy fields make difficult the accurate determination of the substitution effect. The first anisotropy constant K1 is calculated using the available values of HA and Ms. A linear decrease of K1 is observed from SmCo5 to SmCo2Cu3.
TL;DR: In this article, the role of induced anisotropy in the axial, circumferential, and helical directions on magneto-impedance was investigated in CoFeSiB amorphous wires.
Abstract: Changes in the impedance, ≊600%/Oe, at axial fields less than 1 Oe have been observed in the presence of a 90 kHz, few mA current through a soft, nearly zero magnetostrictive wire. In this 125 μm diameter CoFeSiB amorphous wire we observe a total change of 160% at the maxima of the impedance in dc fields less than 2 Oe. A systematic study of the role of induced anisotropy in the axial, circumferential, and helical directions on the magneto‐impedance shows that the largest effect is seen in the wire annealed to obtain circumferential easy axis using a 15 mA ac current passing through it. Both the axial hysteresis loops and the observed I‐V characteristics reflect the induced anisotropies. The observed dependence of the inductance change on the type of the anisotropy induced in these wires can be modeled in terms of an interplay between the induced anisotropy, reversing ac field, and the axial dc field.
TL;DR: The interlayer exchange coupling in several Co/Ru multilayers and bilayers prepared by sputtering has been investigated from magnetization and ferromagnetic resonance experiments and the peak-to-peak-distance has been found to be smaller at thinner Ru layers indicating a preasymptotic or multiperiodic behavior in the coupling.
Abstract: The interlayer exchange coupling in several Co/Ru multilayers and bilayers prepared by sputtering has been investigated from magnetization and ferromagnetic resonance experiments. The hysteresis loops have been discussed in detail, particularly regarding their dependence on the number of layers and the effect of an easy axis direction perpendicular to the film plane. Ferromagnetic as well as antiferromagnetic coupling strengths have been determined in an extended range of Ru thicknesses up to 44 \AA{}. The analysis yields an oscillatory magnetic coupling as a function of the Ru thickness having a period of approximately 12 \AA{}. The peak-to-peak-distance has been found to be smaller at thinner Ru layers indicating a preasymptotic or multiperiodic behavior in the coupling. The envelope function of the coupling was found to decrease, initially as ${\mathit{t}}_{\mathrm{Ru}}^{\mathrm{\ensuremath{-}}2}$ but considerably faster above a Ru thickness of 20 \AA{}. The latter is discussed in terms of mean-free-path effects and of Fermi surface smearing effects both of which are active as a result of structural defects and of the finite measuring temperatures.
TL;DR: In this paper, the authors measured the magnetic susceptibility, anisotropy of susceptibility and hysteresis of single microcrystals of chlorite, biotite, phlogopite, muscovite, zinnwaldite and fuchsite.
TL;DR: The N\'eel model properly accounts for the preferred direction of magnetization parallel to the steps in Co/Cu(1 1 13) and predicts this anisotropy for a bcc Fe film provided the magnetization lies in the film plane, not in the (001) plane.
Abstract: Cu(11n) surfaces vicinal to Cu(001) are characterized by (001) terraces separated by monoatomic steps. Growth of thin epitaxial magnetic films on such terraced substrates, e.g., Co/Cu(1 1 13), leads to unexpected magnetic anisotropy associated with the surface steps. This anisotropy remains largely unexplained, and is of potential technological importance. We have studied the anisotropy of fcc Co/Cu (1 1 13) films using in-situ magneto-optical Kerr effect (MOKE), and find an in-plane uniaxial anisotropy favoring magnetization parallel to the steps. The strength of this anisotropy decreases with increasing film thickness. In this paper we focus on the interpretation of this anisotropy in terms of the N\'eel model. The N\'eel anisotropy energy for such a film has the form ${\mathit{E}}_{\mathrm{film}}$= ${\mathit{E}}_{\mathrm{bulk}}$-2${\mathit{E}}_{\mathrm{surface}}$/t-2${\mathit{E}}_{\mathrm{step}}$/(td), where t and d are film thickness and terrace width, respectively. The last term includes contributions from sites at both the upper edge and inner corner of the step and makes the dominant contribution to the step-induced anisotropy. This model properly accounts for the preferred direction of magnetization parallel to the steps in Co/Cu(1 1 13). bcc Fe/W vicinal to (001) shows a preference for in-plane magnetization perpendicular to the steps for t2.5 monolayers. The N\'eel model also predicts this anisotropy for a bcc Fe film provided the magnetization lies in the film plane, not in the (001) plane.
TL;DR: In this article, the degree of alignment of the magnetic moments of Fe3+ ions in ultrafine maghemite particles has been studied in samples with induced magnetic texture, and it was shown that the lack of full alignment is not an effect of large magnetic anisotropy, as suggested recently, but that the effect is rather due to canting of individual spins.
Abstract: The degree of alignment of the magnetic moments of Fe3+ ions in ultrafine maghemite particles has been studied in samples with induced magnetic texture The textured samples were prepared by freezing ferrofluids, containing 75 nm maghemite particles, in a magnetic field Mossbauer spectroscopy studies of the textured samples in large magnetic fields demonstrate that the lack of full alignment is not an effect of large magnetic anisotropy, as suggested recently, but that the effect is rather due to canting of individual spins
TL;DR: In this article, two simple models involving either lines or planes of interacting spherical particles are used to show that non-uniform distributions of spherical particles can give rise to large anisotropies.
TL;DR: In this article, it was shown that the magneto-elastic anisotropy energy correlates linearly with the saturation magnetostriction of precipitated BCC-FeSi grains.
Abstract: Amorphous Fe-Cu-Nb-Si-B ribbons have been nanocrystallized under tensile stress applied along the ribbon axis. This results in a strong magnetic, creep-induced anisotropy with an easy ribbon axis for low and, a hard ribbon axis for high Si-concentrations, respectively. The analysis of the compositional dependence shows that the anisotropy energy correlates linearly with the saturation magnetostriction of the precipitated BCC-FeSi grains. It is therefore proposed that the induced anisotropy mainly originates from the magneto-elastic anisotropy of the BCC grains due tensile back stresses exerted by the anelastically deformed amorphous matrix. >
TL;DR: In this paper, the effective magnetoelastic coupling coefficients, Beff, of polycrystalline NiFe/Ag/Si (NiFe/Cu/Si), and Ni/SiO2/Si films in situ as functions of magnetic layer thickness over the range from 1.5 to 50 nm using magneto-optic Kerr effect and applied static strain.
Abstract: We have measured the effective magnetoelastic coupling coefficients, Beff, of polycrystalline NiFe/Ag/Si, NiFe/Cu/Si, and Ni/SiO2/Si films in situ as functions of magnetic layer thickness over the range from 1.5 to 50 nm using magneto‐optic Kerr effect and applied static strain. The Beff’s agree well with bulk values at large thicknesses but take on anomalously large values for thicknesses below about 5 nm. The data are well fit by a Neel model, Beff=Bbulk+Bsurf/(t−t0), where t0 may be related to intermixing at the interface with the substrate (verified by Auger depth profiling). These data suggest that the surface conditions are of enhanced importance in controlling magnetic properties, particularly anisotropy, permeability, and noise, even in films whose compositions are nominally of zero magnetostriction.
TL;DR: Experimental and theoretical studies of the magnetization curves of Fe/Cr(211) superlattices with antiferromagnetic interlayer coupling and uniaxial in-plane anisotropy show substantial differences between structures with an even and an even number of Fe layers, when the magnetic field is applied along the easy axis.
Abstract: We report experimental and theoretical studies of the magnetization curves of Fe/Cr(211) superlattices with antiferromagnetic interlayer coupling and uniaxial in-plane anisotropy. There are substantial differences between structures with an even and an odd number of Fe layers, when the magnetic field is applied along the easy axis. For even layered superlattices, the inequivalence of the terminal Fe layers gives rise to a surface spin-flop transition that evolves into a bulk spin-flop arrangement with increasing magnetic field, as originally envisioned by Keffer and Chow [Phys. Rev. Lett. 31, 1061 (1973)].
TL;DR: In this paper, the influence of internal stress on the magnetic anisotropy and the magnetostriction was investigated in sputterdeposited amorphous (Tb0.27Dy0.73)0.42Fe0.58 films.
Abstract: The influence of internal stress on the magnetic anisotropy and the magnetostriction was investigated in sputter‐deposited amorphous (Tb0.27Dy0.73)0.42Fe0.58 films. Films with tensile stress show in‐plane anisotropy and giant magnetostriction of λ∥=400×10−6 at 1 T measured in a field parallel to the film plane at room temperature. The magnetostriction rises rapidly to λ∥=200×10−6 at 0.05 T and the coercivity is less than 0.01 T. On the other hand films with compressive stress show perpendicular anisotropy and still higher magnetostriction of λ∥=540×10−6 at 1 T; however, this is by far a slower increase of magnetostriction at small fields. This different behavior is explained by considering the nature of magnetization processes, i.e., domain‐wall motion and spin rotation.
TL;DR: In this paper, the growth direction of the MnAs thin films was found to be [100] on (001) GaAs, and the epitaxial relationship was [0001] MnAs //[10] GaAs and [110] NMAs // [110 ] GaAs.
Abstract: We have successfully grown single‐crystalline ferromagnetic MnAs thin films on (001) GaAs substrates by molecular beam epitaxy. By reflection high energy electron diffraction and x‐ray measurements, the growth direction of the MnAs thin films was found to be [100] on (001) GaAs, and the epitaxial relationship was [0001] MnAs //[10] GaAs and [110] MnAs // [110] GaAs. Magnetization measurements at room temperature have revealed that the epitaxial MnAs thin films have strong magnetic anisotropy, and that the easy magnetization direction is in‐plane, along the [110] axis of the MnAs thin films which is parallel to the [110] axis of the GaAs substrate, with almost perfect square hysteresis loops, relatively high remanent magnetization, and low coercive field.
TL;DR: In this paper, the S = 1/2 two-channel Kondo model is used to explain the non-Fermi-liquid behavior of dilute tetragonal heavy-electron compounds.
Abstract: Specific heat C , electrical resistivity ρ , magnetization M and magnetic susceptibility χ have been measured for the dilute tetragonal heavy-electron compounds U x Th 1- x Ru 2 Si 2 ( x ≤0.07), in the temperature range 100 mK≤ T ≤360 K and in the magnetic fields H up to 55 kOe. Non-Fermi-liquid behavior with unusual lnT dependence of C , ρ and χ has been observed at the low temperatures: as the temperature is lowered below about 10 K, C / T and χ increase logarithmically, and ρ decreases logarithmically. Systematical variations of these quantities with uranium concentration indicate that the observed non-Fermi-liquid behavior is ascribed to the properties of a single U ion embedded in the Th site of the ThRu 2 Si 2 metal. The magnetization curves M vs H / T indicate a strong uniaxial magnetic anisotropy along the tetragonal c -axis as well as a strong reduction of the 5 f moment of U ions. A possible interpretation based on the recent developments of the S =1/2 two-channel Kondo model is given.
TL;DR: It is shown that some features of magnetization reversal are associated with spins at the surface of fine particles as well as the bulk random axis and surface anisotropy.
Abstract: We solve numerically the dissipative Landau-Lifshitz-Gilbert equations to consider hysteresis in fine magnetic particles. Finite-size effects are studied for two models with uniaxial anisotropy---bulk random axis and surface anisotropy only. It is demonstrated that the latter model introduces considerable effects for small enough particles when the coupling to the anisotropy is equal or greater than the coupling to the isotropic Heisenberg exchange. We show that some features of magnetization reversal are associated with spins at the surface of fine particles.
TL;DR: In this paper, a magnetic thin-film inductor using rotation magnetization was proposed, which has a sandwich structure consisting of a double-rectangular spiral coil between top and bottom CoZrNb amorphous thin films.
Abstract: The authors propose a novel structured magnetic thin film inductor using rotation magnetization only. The thin film inductor has a sandwich structure, which consists of a double-rectangular spiral coil between top and bottom CoZrNb amorphous thin films. The sputtered CoZrNb amorphous magnetic thin films have uniaxial magnetic anisotropy induced by direct current field annealing. The easy magnetization axis is directed to the main axis of the rectangular spiral coil. Hence, only the rotation magnetization process dominates in this device. The typical specifications are as follows; 3.5/spl times/5.5 mm in size, inductance of 1 /spl mu/H constant up to 10 MHz, and a quality factor of 10 at 10 MHz. A MHz switching chopper dc-dc converter has been developed by using this thin film inductor, bare-chip semiconductor devices (a power MOSFET and a Schottky barrier diode), and a multilayer ceramic capacitor. This converter with a 0.1 cc volume has an output power over 1 W at 5 MHz switching, and the power density exceeds 10 W/cc (160 W/in/sup 3/). >
TL;DR: In this paper, a total energy function is used to describe a theory of hysteresis effects in crystalline, ferromagnetic materials, which is applied on the cubic structure of FeSi crystals, which are oriented in a (110)[001] texture.
Abstract: Calculations of a total energy function are used to describe a theory of hysteresis effects in crystalline, ferromagnetic materials. This model is applied on the cubic structure of FeSi crystals, which are oriented in a (110)[001] texture. The magnetic energy of the crystal is separated in reversible and irreversible parts: The reversible energy is expressed by magnetocrystalline anisotropy and shape anisotropy. They are responsible for the rotation of the domain magnetization at strong fields. At weak fields the reversible interaction of the domain wall motion with the stray fields of pinning centers (nonmagnetic inclusions, grain boundaries or inner strains) is described by a probability function of statistic domain behavior. The irreversible energy is caused by these pinning centers, too, and can be explained by the interaction losses of the magnetic moments in the Bloch wall with the crystal lattice during an irreversible Barkhausen jump. The energy of the applied field is added to these two parts and the magnetic state of the material is represented by the minima of the total energy function. The results show all features of hysteresis such as initial magnetization curve and major and minor hysteresis loops in good agreement with measurements on grain oriented 3,5% silicon‐steel with Goss texture.