Showing papers on "Magnetic anisotropy published in 1986"
TL;DR: In this paper, a mathematical model of the hysteresis mechanisms in ferromagnets is presented based on existing ideas of domain wall motion including both bending and translation, which gives rise to a frictional force opposing the movement of domain walls.
1,989 citations
TL;DR: In this article, the temperature dependence of the saturation magnetization and the magnetocrystalline anisotropy field have been measured on single-crystal samples of the R2Fe14B compounds for R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm.
Abstract: The temperature dependence of the saturation magnetization and the magnetocrystalline anisotropy field have been measured on single‐crystal samples of the R2Fe14B compounds for R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm from 4.2 K to the magnetic ordering temperatures. A spin reorientation transition of the Nd2Fe14B type has been found in Ho2Fe14B at 57.6 K in zero field. Another type of spin reorientation caused by anisotropy compensation between the Fe and the R sublattices exists in Er2Fe14B and Tm2Fe14B. The temperature dependence of the angle of the easy direction of magnetization from the c axis has been measured for R=Nd, Ho, Er, and Tm. The relation between the magnetocrystalline anisotropy and the sublattice magnetization is investigated by employing a simplified two‐sublattice molecular field model.
779 citations
TL;DR: The temperature dependence of the (single-ion) random anisotropy strength can provide a plausible explanation for certain classes of reentrant phenomena and susceptibility cusps observed in magnetization studies.
Abstract: We summarize and extend our study (using real-space response and correlation functions) of the properties of a continuous-symmetry ferromagnet with random anisotropy, distinguishing between the cases of weak and strong random anisotropy. For the weak-anisotropy case we find three different magnetic regimes, according to the strength of the external magnetic field H. In zero H, the net magnetization is zero, although the ferromagnetic correlation length (FCL) is large. We call a ferromagnet in this first regime a correlated spin glass (CSG). It has a very large magnetic susceptibility, and hence a relatively small coherent anisotropy converts it into a nearly typical ferromagnetic domain structure. Also, a relatively small magnetic field nearly aligns the CSG, producing the second regime, which we call a ferromagnet with wandering axis (FWA). The FWA is a slightly noncollinear structure in which the tipping of the magnetization with respect to the field varies over the system. The tipping angle is correlated over a (field-dependent) correlation length which is smaller than the FCL of the CSG. As the field increases the correlation length in the FWA decreases, until the third regime is reached, wherein the tipping angles (which are smaller than in the FWA) are completely uncorrelated from site to site. We obtain the magnetization or susceptibility (as appropriate) for each of these three regimes. We also show that the temperature dependence of the (single-ion) random anisotropy strength can provide a plausible explanation for certain classes of reentrant phenomena and susceptibility cusps observed in magnetization studies. Neutron scattering studies appear to be consistent with the predicted ${H}^{\mathrm{\ensuremath{-}}1/2}$ dependence of the FCL in the FWA regime, and display the expected rise of the FCL in the CSG regime as the random anisotropy strength decreases with increasing temperature.
359 citations
TL;DR: In this paper, the spin anisotropy of ferromagnetic monolayers of Fe, Ni, and V was calculated and it was shown that the easy direction of magnetization is perpendicular to the plane of the monolayer for Fe and V, but in the plane for Ni.
Abstract: We calculate the spin anisotropy of ferromagnetic monolayers of Fe, Ni, and V. We find that the easy direction of magnetization is perpendicular to the plane of the monolayer for Fe and V, but in the plane for Ni. The result for Fe explains why spin splitting but no spin polarization is observed in recent photoemission experiments on Fe overlayers.
315 citations
TL;DR: Ferromagnetic resonance measurements in Co films of 11.3, 20, and 80 A\r{} thickness sandwiched by Au have been made as a function of the dc magnetic field orientation in a plane perpendicular to the film.
Abstract: Ferromagnetic resonance measurements in Co films of 11.3, 20, and 80 A\r{} thickness sandwiched by Au have been made as a function of the dc magnetic field orientation in a plane perpendicular to the film. These polycrystalline films were measured to have the hcp structure with the c axis perpendicular to the film plane within a few degrees. The experimental results are well explained by a theoretical model where an axial magnetic anisotropy up to the second-order term is included.
285 citations
TL;DR: In this paper, the authors used low-field IRM measurements to determine whether anisotropic rocks contain uniaxial single-domain particles or whether the particles are essentially multidomain.
Abstract: Summary. Susceptibility, thermo-remanent magnetization (TRM) and isothermal remanent magnetization (IRM) anisotropy ellipsoids have been determined for several rock samples. The results indicate that the ellipsoid of initial susceptibility is less anisotropic than the TRM and low field IRM ellipsoids which are found experimentally to be of identical shape. This suggests that palaeomagnetic data for anisotropic rocks may be corrected by using the anisotropy ellipsoid determined from magnetically non-destructive low field IRM measurements. Such IRM measurements can also be used to obtain anisotropy axes of samples which are inherently anisotropic but which have a susceptibility which is too weak to be accurately measured. The results for a series of artificial anisotropic samples containing magnetite particles of different sizes (in the range 0.2–90 μm) were very similar to those for the rocks. In contrast, a comparison of the susceptibility and IRM ellipsoids for anisotropic samples containing particles from a magnetic tape gave very different results in accordance with theory. Such results imply that susceptibility and IRM ellipsoids could be used to determine whether anisotropic rocks contain uniaxial single-domain particles (magnetization confined to the easy axis) or whether the particles are essentially multidomain.
280 citations
TL;DR: In this paper, the basic properties of rare-earth compounds of the type R 2 Fe 14 B, R 2 Co 14 B and several related intermetallic compounds are discussed in terms of magnetic exchange interaction and crystal field theory.
207 citations
TL;DR: In this paper, the magnetic anisotropy constants of Nd 2 Fe 14 B have been determined in the temperature range between 4.2 and 575 K using aligned sintered Nd 15 Fe 77 B 8 magnets.
205 citations
TL;DR: An alternating terbium-iron (Tb•Fe) multilayer structure artificially made in amorphous Tb-Fe thin films gives rise to excellent magnetic properties of large perpendicular uniaxial anisotropy, large saturation magnetization, and large coercivity over a wide range of Tb composition in the films as mentioned in this paper.
Abstract: An alternating terbium‐iron (Tb‐Fe) multilayer structure artificially made in amorphous Tb‐Fe thin films gives rise to excellent magnetic properties of large perpendicular uniaxial anisotropy, large saturation magnetization, and large coercivity over a wide range of Tb composition in the films. The films are superior to amorphous Tb‐Fe alloy thin films, especially when they are piled up with a monatomic layer of Tb and several atomic layers of Fe in an alternating fashion. Small‐angle x‐ray diffraction analysis confirmed the layering of monatomic layers of Tb and Fe, where the periodicity of the layers was found to be about 5.9 A. Direct evidence for an artificially layered structure was obtained by transmission electron microscopic and Auger electron spectroscopic observations. Together with magnetic measurements of hysteresis loops and torque curves, it has been concluded that the most important origin of the large magnetic uniaxial anisotropy can be attributed to the Tb‐Fe pairs aligned perpendicular t...
181 citations
TL;DR: In this paper, a review on experimental methods to determine magnetic surface anisotropies is given, and experimental results for well-defined single-crystal surfaces, both for out-of-plane and in-plane anisotropic properties are compared with Neel's phenomenological theory.
175 citations
TL;DR: In this article, a wave-guiding theory for multilayer magnetic crystalline structures is proposed. But it is limited to the case where the optical response of the structures is linear in the amplitude of the incident wave.
Abstract: Through the extension of the Yeh's formalism (Surf. Sci.96 (1980) 41) to magnetic crystalline media the formulas of the magneto-optic ellipsometry and the dispersion relations for wave-guiding in multilayer magnetic crystalline structures are obtained. The theory covers most of the situations considered so far in the magneto-optics in which the optical response of the structures is linear in the amplitude of the incident wave. It is capable of treating the interfaces between two magnetic media and the structures containing such interfaces with no restrictions on the orientation of the magnetizations and crystalline axes at an arbitrary angle of incidence. The polar, longitudinal and transversal magnetizations in the structures are considered as special cases. Possible applications of the theory are in the analysis of the planar multilayer magneto-optic systems in the integrated optics and magneto-optic memory technology, in the study of profiles of magnetic surfaces subjected to mechanical wear, ion implantation, etc.
TL;DR: In this paper, the magnetic properties of amorphous Fe78Si9B13 have been determined from cross-sectional micrographs, i.e. perpendicular anisotropy, remanence to saturation ratio and coercivity.
TL;DR: In this paper, the experimental results concerning the magnetic anisotropic induced by transverse field annealing were presented, where the magnetic field has been created by an electrical current flowing along the amorphous ribbon.
TL;DR: It is shown that the time-dependent phenomena are well characterized by an algebraic function with the exponent described by an exponential function of temperature, and the existence of a thermodynamic equilibrium state in magnetic fields is suggested.
Abstract: Magnetization measurements have been made on an insulating random mixture, ${\mathrm{Fe}}_{0.5}$${\mathrm{Mn}}_{0.5}$Ti${\mathrm{O}}_{3}$. An Ising spin-glass behavior has been observed below ${T}_{g}=21.1$ K. It is shown that the time-dependent phenomena are well characterized by an algebraic function with the exponent described by an exponential function of temperature. The results are compared with the computer-simulation results obtained by Ogielski. In addition, we suggest the existence of a thermodynamic equilibrium state in magnetic fields.
TL;DR: In this article, the temperature dependence of the anisotropy field was determined in various R 2 Fe 14 B compounds (R = Y, La, Ce, Pr, Nd, Gd, Ho, Lu and Th).
TL;DR: The magnetic susceptibility of quartz single crystals is diamagnetic (−14×10−6 in SI units) and exhibits only very small anisotropy (mostly less than 1%); thus the susceptibility of the quartz matrix in quartzite can be regarded as virtually isotropic as mentioned in this paper.
Abstract: The magnetic susceptibility of quartz single crystals is diamagnetic (−14×10−6 in SI units) and exhibits only very small anisotropy (mostly less than 1%); thus the susceptibility of the quartz matrix in quartzite can be regarded as virtually isotropic. Owing to the influence of the negative and isotropic susceptibility of the quartz matrix, the degree of anisotropy of quartzite, as inferred from model calculations, is higher than that of the ferrimagnetic fraction. This influence is very strong if the mean susceptibility of quartzite is in the vicinity of zero.
TL;DR: The magnetocrystalline anisotropy of MnAl and MnAlC alloys, in the range of existence of the ferromagnetic τ phase, has been studied by using the singular point detection technique as mentioned in this paper.
Abstract: The magnetocrystalline anisotropy of MnAl and MnAlC alloys, in the range of existence of the ferromagnetic τ phase, has been studied by using the singular point detection technique. The anisotropy field value at 293 K varies from 39 kOe for low manganese and high carbon content to 55 kOe for high manganese and carbon‐free samples. The anisotropy of the MnAl τ phase is well described by using only the K1 anisotropy constant. The temperature dependence of the calculated anisotropy constant indicates that a single ion mechanism is the origin of the magnetocrystalline anisotropy in these alloys.
TL;DR: Amorphous Tb-Fe thin films prepared by dual magnetron cosputtering were exposed to air at 200 °C in order to investigate the evolution of the films as they oxidize as mentioned in this paper.
Abstract: Amorphous Tb‐Fe thin films prepared by dual magnetron cosputtering were exposed to air at 200 °C in order to investigate the evolution of the films as they oxidize. Magnetic properties of the films were measured using a vibrating‐sample magnetometer and torque magnetometer and are interpreted in light of the structure of the films as revealed by Auger electron spectroscopy and composition‐depth profiling. This leads to a detailed and self‐consistent description of the oxidation process. At first a uniform and homogeneous oxidation layer grows from the surface toward the substrate. This layer has a high magnetization and low intrinsic anisotropy and consists of an intimate mixture of oxidized Tb and metallic TbxFe(1−x). The initially high intrinsic anisotropy of the unoxidized region decreases relatively quickly, while the composition changes only slowly as this region shrinks. When the oxidation layer reaches the substrate, two oxide phases (Fe2O3 and Tb2O3) begin to grow at the surface exposed to air.
TL;DR: In this article, the effects of Fe substitution by Co on the saturation magnetization, Curie temperature and anisotropy of R 2 (Fe, Co) 14 B compounds were investigated over the temperature range 4 to 300 K.
TL;DR: In this paper, the authors investigated the dependence of intrinsic coercivity of R-Fe-B permanent magnets (R = rare earths) on the anistropy field of R 2 Fe 14 B.
TL;DR: The anomalous anisotropic magnetic interactions and the spin dynamics of the fcc type-I or -IA antiferromagnetic cerium and uranium monopnictides CeAs, CeSb, and USb have been studied by inelastic and diffuse critical neutron scattering experiments and evidence for important effects of higher-order magnetic interactions is found.
Abstract: The anomalous anisotropic magnetic interactions and the spin dynamics of the fcc type-I or -IA antiferromagnetic cerium and uranium monopnictides CeAs, CeSb, and USb have been studied by inelastic and diffuse critical neutron scattering experiments. The diffuse scattering above the antiferromagnetic ordering temperature largely corresponds to longitudinal spin fluctuations which are highly anisotropic. In the ordered state the dispersion curves of the spin-wave excitations strongly depend on the actually realized spin structure. For the antiferromagnets the spin waves split into transverse modes with different polarizations due to the exchange anisotropy. In CeAs one of these modes exhibits nearly zero energy gap and quadratic dispersion which has not previously been observed in antiferromagnets. The wave-vector-dependent susceptibility tensor has been calculated within the random-phase-approximation (RPA) by taking account of crystal-field, anisotropic bilinear exchange, and isotropic quadrupolar interactions. General expressions including all levels of the ground-state multiplet are derived for single-q and triple-q type-I as well as for type-IA antiferromagnets, and detailed formulas of the magnetic excitation spectrum are given for the particularly interesting case of effective two-level systems which are often realized in f-electron magnets. The RPA formalism consistently describes the transverse magnetic excitations for T${T}_{N}$ as well as the longitudinal spin fluctuations for Tg${T}_{N}$ for all compounds under study. For CeAs and CeSb the bilinear exchange interactions turn out to be similar, and evidence for important effects of higher-order magnetic interactions is found. The latter are shown to be the driving mechanism for the realization of the various magnetic phases in CeSb. For CeAs the magnetic excitation spectrum unambiguously demonstrates that a collinear single-q type-I spin structure is realized, whereas for USb a noncollinear triple-q type-I spin structure emerges from the observed magnetic excitations.
TL;DR: In this paper, the authors measured the temperature dependence of the anisotropy field of Nd 2 Fe 14 − x -Co x B using the singular point detection (SPD) technique.
Abstract: The temperature dependence of the anisotropy field of Nd 2 Fe 14 − x -Co x B has been measured between 77 K and the Curie temperature, using the singular point detection (SPD) technique. The anisotropy field at room temperature is found to decrease with increasing cobalt content. Measurements of the temperature dependence of the initial susceptibility show that at a temperature T 1 , which is below room temperature, the easy magnetization direction changes. The origin of the change is attributed to the neodymium-sublattice anisotropy. For the cobalt-rich samples ( x ⩾ 5) it is found that at temperatures T 2 higher than ambient temperatures a second spin reorientation takes place, which is attributed to the competing effect of the neodymium sublattice anisotropy and the 3d sublattice anisotropy.
TL;DR: The easy axis of magnetization was perpendicular to the film plane which correlated with a preferential texturing of the c-axis out of the film planes as observed by x-ray diffraction.
Abstract: Film samples of Nd 2 Fe 14 B which exhibit perpendicular anisotropy have been synthesized by selectively thermalized sputtering onto heated substrates. Minor hysteresis loops measured with fields up to 20 kOe perpendicular to the film plane exhibited a remanent moment of 9.3 kG and an intrinsic coercive force, i H c , of 14.8 kOe at room temperature. The easy axis of magnetization was perpendicular to the film plane which correlated with a preferential texturing of the c-axis out of the film plane as observed by x-ray diffraction. Effective large perpendicular anisotropy constants of 1.2 × 107erg/cc have been observed. Films sputtered at deposition rates lower than 1.8 A/sec exhibited perpendicular anisotropy while those deposited at rates greater than this exhibited in the plane anisotropy.
TL;DR: In this article, the effect of deformation on the remanent magnetization vector was investigated using passive marker theory, and the results showed that the remanence distribution was dominated by the shortening axis directions of the magnetic anisotropy ellipsoid.
Abstract: Paleomagnetic investigations have usually been impossible in deformed rocks because of the effects of distortion on the remanent magnetization vector. Deformation produces a magnetic anisotropy in rocks which can deflect the remanence away from the minimum susceptibility axis. However, the assumption that the intersection points of great circles joining these two directions represent an improved estimate of the undisturbed remanence is invalid because the amount of the deflection of each remanence is not really known. Anisotropy of magnetic susceptibility (AMS) provides a quantitative basis for strain determination. The principal axes of the magnetic anisotropy ellipsoid have the same directions as those of the strain ellipsoid. A linear relationship between the normalized principal susceptibility differences and the logarithmic strains has been found in several rock types. If the correlation method used is valid, AMS observations can be used to establish the magnitudes and directions of the principal strains. Strain modifies bedding planes and realigns the grains that carry magnetic remanence. Compensation for deformation requires application of a modified bedding tilt correction and correction of the remanent vector for distortional strain. The effects of strain on bedding can be corrected using passive marker theory. Attempts to compensate for distortional strain by treating the remanent vector as a passive marker have proved inconclusive. During deformation linear and planar elements deflect away from the axis of maximum shortening. The passive marker correction shifts the remanent vectors toward the local shortening axis for the site and reduces the directional scatter. Tests of the passive marker method in strongly deformed rocks resulted in a remanence distribution dominated by the shortening axis directions. The passive marker model becomes inapplicable when the deformation results in recrystallization of the rock matrix.
TL;DR: In this paper, it was shown that in ferromagnetic crystals with uniaxial symmetry the critical field for domain nucleation can be strongly determined by the second anisotropy constant K 2.
TL;DR: In this article, the structural and magnetic parameters of Nd2Fe14−xTxB with T =Cr, Mn, Co, Ni, Al, and Al substitution are discussed.
Abstract: Trends in structural and magnetic parameters are presented and discussed for Nd2Fe14−xTxB with T=Cr, Mn, Co, Ni, Al. Some data are also included on the Y analog systems. Partial Al substitution strongly increases c/a. We show that this has to do with preferential occupation of the larger atom (Al) in the σFe layer. Co and Ni substitutions increase Curie temperature (TC) while all others decrease it. Anisotropy constants K for 300 K decrease in all cases investigated compared to Nd2Fe14B. Some discussion is given to the general mode of preferential substitution and the concomitant effects on magnetic anisotropy.
Patent•
24 Apr 1986
TL;DR: In this article, an overwritable photomagnetic recording method was obtained by impressing an initial auxiliary magnetic field to a photOMagnetic recording medium, collecting only a magnetization of a recording auxiliary layer to one of the upper or lower direction, modulating pulsatively a beam intensity by binary-coded information to be recorded, and forming a bit in accordance with intensity and weakness of a beam.
Abstract: PURPOSE: To obtain an overwritable photomagnetic recording method, by impressing an initial auxiliary magnetic field to a photomagnetic recording medium, collecting only a magnetization of a recording auxiliary layer to one of the upper or the lower direction, modulating pulsatively a beam intensity by binary-coded information to be recorded, impressing a recording magnetic field to a beam irradiated part, and forming a bit in accordance with intensity and weakness of a beam CONSTITUTION: A multi-layer photomagnetic recording medium in which the first layer having a vertical magnetic anisotropy is a recording and reproducing layer and the second layer having a vertical magnetic anisotropy is a recording auxiliary layer is used as a medium Before recording only a magnetization of a recording auxiliary layer by moving this medium, and applying an initial auxiliary magnetic filed, it is collected to one of the upper or the lower direction Subsequently, a laser beam which has modulated pulsatively a beam intensity in accordance with binary-coded information to be recorded is irradiated, and a recording magnetic field is applied to a medium part to which the beam has been irradiated When a pulsative beam has an intensity of a high level, one bit of a bit having a magnetization in the upper direction and a bit having a magnetization in the lower direction is formed, and when the intensity of the beam is a low level, the other bit is formed COPYRIGHT: (C)1987,JPO&Japio
TL;DR: In this paper, anisotropy induced signal waveform modulation was observed through the use of a disk certifier and verified with vibrating sample magnetometer (VSM) orientation measurements and electron microscopic observation of grain structure.
Abstract: Thin films of Co-alloy, intended for use in longitudinal recording, were deposited onto variously prepared substrates by in-line DC magnetron sputtering. An anisotropy induced signal waveform modulation was observed through the use of a disk certifier and verified with vibrating sample magnetometer (VSM) orientation measurements and electron microscopic observation of grain structure. The partial low angle of incidence which can occur in in-line sputtering, the magnetic field generated from the magnetron target, the surface topography of substrates and the sputtering conditions, all affected the extent of preferred anisotropy in the films. By minimizing low angle of incidence sputtering, texturing the substrate surface circumferentially, and adjusting the processing conditions, we can eliminate not only the signal waveform modulation but also enhance the magnetic properties.
TL;DR: In this article, the dependence on composition and temperature of the saturation magnetization Ms, the uniaxial anisotropy constant Ku, the Faraday rotation θF, and the faraday ellipticity ψF, have been investigated.
Abstract: Garnet films of composition R3−x−yPrxBiyFe5O12 with R=Lu, Y, and 0≤x≤1.8, 0≤y≤1.7 have been grown from different melt compositions and under various growth conditions onto substituted gadolinium gallium garnet substrates with (100), (110), (111), and (211) orientation. The dependence on composition and temperature of the saturation magnetization Ms, the uniaxial anisotropy constant Ku, the Faraday rotation θF, and the Faraday ellipticity ψF, have been investigated. The change of Ms as compared to that of Y3Fe5O12 is essentially associated with the alignment of the Pr moment parallel to the net iron moment and the increase of the Curie temperature originating mainly from the bismuth. However, both contributions are negligible in the room‐temperature range. The uniaxial anisotropy is strongly affected by both Pr and Bi. The anisotropy contributions ΔKu /x 0 turn out to be approximately additive. Both Pr and Bi give rise to a pronounced enhancement of the magneto‐optical effects. At λ=633 nm θF increases linearly with x and y yielding at T=295 K the contributions ΔθF/x =−3.8×105 deg m−1 and ΔθF/y=−20.6×105 deg m−1, respectively. The bismuth contribution compares well with that observed for various other Bi‐substituted rare earth iron garnets.
Patent•
08 May 1986
TL;DR: In this paper, the magnetic layers 1, 2 are laminated, and the magnetic interlayer bonding effect generated between the two layers is exerted on the magnetic layer 1. The magnetic layer 2 has a high magneto-optical effect at a short wavelength and small perpendicular magnetic anisotropy.
Abstract: PURPOSE: To attain high-density recording by laminating at least one layer each of a first magnetic layer and second magnetic layer consisting of rare earth-transition metal amorphous films on a substrate and increasing the intensity of the magnetic anisotropy in the direction perpendicular to the film plane. CONSTITUTION: This magneto-optical recording medium is formed by laminating at least one layer each of the first magnetic layer 1 and second magnetic layer 2 consisting of the rare earthtransition metal amorphous films on the substrate 3. The magnetic layer 1 is the one element selected from an element group consisting of Nd and Pr. The magnetic layer 2 contains only one element selected from an element group consisting of Tb and Dyb. The magnetic layer 1 has a high magneto-optical effect at a short wavelength and small perpendicular magnetic anisotropy. The magnetic layer is conversely small in the magnet optical effect and large in the perpendicular magnetic anisotropy. When the magnetic layers 1, 2 are laminated, the magnetic interlayer bonding effect generated between the two layers is exerted on the magnetic layer 1. The medium of the perpendicularly magnetized films having the high magneto-optical effect even at a short wavelength over the entire part of the laminated layers is then obtd. and high-density recording is made possible.