Showing papers on "Magnetic anisotropy published in 1978"
TL;DR: In this article, the effect of strong random anisotropy in materials such as amorphous Tb•Fe and Dy•Fe at low temperature and also examine the role which weak random an isotropy might play in even ideally homogeneous soft materials.
Abstract: Random anisotropy is present in all amorphous magnetic materials, and depending on its strength, it can dramatically affect the magnetic behavior. We describe the effect of strong random anisotropy in materials such as amorphous Tb‐Fe and Dy‐Fe at low temperature and also examine the role which weak random anisotropy might play in even ideally homogeneous soft materials. Much of our analysis is based on the simple model proposed by Harris, Plischke and Zuckerman for a ferromagnet with random‐axis uniaxial anisotropy. We describe computer simulation results for this model and then develop scale length arguments which allow us to describe fluctuations in the magnetization direction. For a perfectly isotropic distribution of anisotropy axis we find that the conventional ferromagnetic ground state is unstable. The new ground state has large frozen in fluctuations but probably has a considerable moment and is, therefore, not spin glass‐like. This system does not support domain walls of the conventional type. For a system with both a macroscopic anisotropy axis and random anisotropy, we can have domain walls. We present a theory for the intrinsic coercivity which gives values of about 10−6 Oe for Fe‐metalloids and 0.2 Oe for Gd‐Co‐Mo. This indicates that inhomogeneities of larger than atomic scale are limiting the behavior of present materials. A model illustrating aspects of magnetic resonance behavior is also described.
659 citations
TL;DR: In this article, a review of the collinear and random magnetic structures which may be found in magnetically-concentrated amorphous solids is given, with an emphasis on non-collinear spin structures.
Abstract: A review is given of the collinear and random magnetic structures which may be found in magnetically‐concentrated amorphous solids General consequences of a non‐crystalline lattice on the atomic moments, exchange interactions and single‐ion anisotropy are presented Magnetic structures with one and two magnetic subnetworks are then described, taking examples from the literature of each type Some discussion is also given of the low energy excitations and the behavior at the spin freezing or ordering temperature What happens to the familiar forms of magnetic order—ferromagnetism, ferrimagnetism, antiferromagnetism—in the absence of a crystalline atomic lattice? This article sets out to give an overview of magnetic order in non‐crystalline solids in an attempt to answer the question The magnetism of two classes of disordered metals have received particular attention during the past five years; amorphous ferromagnets, notably the Metglas‐type alloys, and spin glasses, typically dilute solutions of transition‐metal impurities in a non‐magnetic crystalline matrix The subject‐matter here will be magnetically‐concentrated amorphous materials, with the accent on non‐collinear spin structures A coherent picture of amorphous magnetism will be presented, but it must be admitted that not all the magnetic structures discussed have been equally well established Some of them are directly analogous to those found in crystals Others are peculiar to amorphous (or disordered) solids, whereas one crystalline magnetic structure seems impossible in a noncrystalline lattice
338 citations
TL;DR: In this paper, a Co-Cr recording film with perpendicular anisotropy has been developed by an RF sputtering, which is found to show some suitable properties for high density recording such as a rectangular M-H loop, and fine grain structure.
Abstract: For a new perpendicular magnetic recording system, a Co-Cr recording film with perpendicular anisotropy has been developed by an RF sputtering. The Co-Cr films are found to show some suitable properties for high density recording such as perpendicular anisotropy, a rectangular M-H loop, and fine grain structure. An extremely high recording density of 100,000 bits/inch was realized by using the Co-Cr film. The crystal and microscopic structure of the films are also discussed, and the perpendicular anisotropy of the Co-Cr films is mainly originated from the uniaxial magneto-crystalline anisotropy.
298 citations
TL;DR: The regular arrangements of the peptide bonds in beta pleated sheet and collagen structures also produce substantial anisotropy, but less than for alpha helix.
Abstract: Magnetic anisotropy in proteins and polypeptides can be attributed to the diamagnetic anisotropy of the planar peptide bonds. The alpha helix in particular has large anisotropy due to the axial alignment of the peptide bonds. The regular arrangements of the peptide bonds in beta pleated sheet and collagen structures also produce substantial anisotropy, but less than for alpha helix. The anisotropy permits orientation of small structures of these types in magnetic fields of several kilogauss.
175 citations
IBM1
TL;DR: In this article, a new process for obtaining unidirectional anisotropy in 80:20 NiFe films is described and applied to the biasing of a magnetoresistive read head and no Barkhausen noise was observed in its output.
Abstract: A new process for obtaining unidirectional anisotropy in 80:20 NiFe films is described. This process was applied to the biasing of a magnetoresistive (MR) read head and no Barkhausen noise was observed in its output.
175 citations
TL;DR: Amorphous thin films of NdxCo1−x and NdxFe 1−x alloys were prepared over the compositional range 0.08⩽x ⩽0.71 by e −beam evaporation as discussed by the authors.
Abstract: Amorphous thin films of NdxCo1−x and NdxFe1−x alloys were prepared over the compositional range 0.08⩽x⩽0.71 by e‐beam evaporation. Magnetization and anisotropy of the samples were studied over a wide temperature range with the aid of a force balance magnetometer, Hall effect measurements, and Mossbauer spectroscopy. It was found that the magnetization of the alloys could not be accounted for by a completely collinear alignment (ferromagnetic) of the Nd and transition‐metal subnetworks. Mean field analysis of the magnetization data showed a large reduction of the Nd–transition‐metal exchange coupling as compared to their Gd analogs. A model was developed which requires that Nd be dispersed in a cone whose axis is parallel to that of the transition‐metal subnetwork by strong coupling to randomly oriented local crystal field axes. This dispersion reduces the Nd net moment to 77% of its free‐ion moment in NdxCo1−x alloys and to 25% of its free‐ion moment in NdxFe1−x alloys. There is evidence that some dispers...
135 citations
TL;DR: In this article, the anisotropy field as measured by resonance is calculated for a coherent assembly of small magnetic particles possessing both crystal and shape anisotropic properties, and the theoretical results are compared with experimental data on precipitated cobalt and magnesioferrite particles.
Abstract: The anisotropy field as measured by resonance is calculated for a coherent assembly of small magnetic particles possessing both crystal and shape anisotropy. The theoretical results are compared with experimental data on precipitated cobalt and magnesioferrite particles.
133 citations
TL;DR: In this article, the effects of local magnetic anisotropy (RMA) on the magnetic properties of amorphous rare earth alloys have been examined with a view to assessing the effect of RMA on their magnetic properties.
123 citations
TL;DR: The magnetic properties of stoichiometric Fe2P and non-stochastic Fe2-xP (0 < × ≤ 0.06) have been studied by means of magnetic susceptibility as mentioned in this paper.
Abstract: The magnetic properties of stoichiometric Fe2P and non-stoichiometric Fe2-xP (0 < × ≤ 0.06) have been studied by means of magnetic susceptibility. Measurements on pure stoichiometric Fe2P samples show that there is a first order magnetic phase transition from a ferro- to a paramagnetic state at 216 ± 1 K. The transition is accompanied by a discontinuous change in the dimensions of the hexagonal unit cell with a decrease in the a-axis of 0.06% and an increase in the c-axis of 0.08% for increasing temperature. The transition is interpreted to be of magnetoelastic origin with an exchange energy critically sensitive to the interatomic spacing. Measurements on single crystals show that the spins are directed along the hexagonal c-axis with an exceedingly high axial anisotropy. The saturation moment is 1.46 μB/iron atom and the anisotropy energy as estimated from low field data is ~ 2.5 × 106 J m-3 (2.5 × 107 erg cm-3). The transition behaviour is very sensitive to the magnitude of the external field as well as to the presence of impurities and deviations from the ideal stoichiometry in the samples.
94 citations
TL;DR: The anisotropy of magnetic susceptibility times membrane thickness was calculated from the data for several thin-walled vesicles and the resulting values were assigned to discrete numbers of bilayers.
88 citations
TL;DR: Saturation magnetizations were measured on single crystals of TbFe 2, DyFe 2, Tb 027 Dy 073 Fe 2 and TmFe 2 over most of the temperature ranges from 4 K to 300 K.
Abstract: Saturation magnetizations were measured on single crystals of TbFe 2 , DyFe 2 , Tb 027 Dy 073 Fe 2 and TmFe 2 Over most of the temperature rang from 4 K to 300 K, these values are substantially larger than those measured earlier on polycrystals The intrinsic magnetic anisotropies, K 1 (0)'s, as determined from magnetic fields required for saturation, are huge ( \sim5 \times 10^{8} erg/ cm3) For these highly magnetostrictive compounds, the magnetoelastic contribution to the anisotropy -\frac{1}{2}c_{44}\lambda\min{111}\max{2} is a significant fraction of the total anisotropy
TL;DR: The magnetic ordering of the anomalous antiferromagnet CeSb, which has a NaCl crystal structure, was determined in zero applied magnetic field by means of neutron diffraction investigations of single crystals and powder as mentioned in this paper.
Abstract: The magnetic ordering of the anomalous antiferromagnet CeSb, which has a NaCl crystal structure, was determined in zero applied magnetic field by means of neutron diffraction investigations of single crystals and powder. Below the Neel temperature TN of (16.1+or-0.1)K, there exist six partially disordered magnetic phases of antiphase domain type ((100) superstructures) with (100) orientation of the magnetic moments. At 4.4K, the ordered magnetic moment equals (2.10+or-0.04) mu B, which corresponds to the free-ion value of 2.14 mu mB for Ce3+. The temperature dependence of the ordered moment shows a first-order phase transition at TN. At approximately TN/2 there is a first-order phase transition to a FCC type IA low-temperature configuration. The unusual magnetic properties of CeSb, which result from anisotropic exchange and crystalline electric field effects, resemble those of certain actinide NaCl-type compounds.
TL;DR: In this paper, a model is presented to explain the bias voltage dependence of magnetic anisotropy in sputtered amorphous films of gadolinium cobalt alloys.
Abstract: A model will be presented to explain the bias voltage dependence of magnetic anisotropy in sputtered amorphous films of gadolinium cobalt alloys. It has been found that the magnetic anisotropy increases with bias voltage up to a critical bias voltage (∠150 V depending on the sputter gas) then decreases precipitously at higher voltages. The model used to explain this behavior is based on selective resputtering of atoms in different surface sites causing an anisotropic distribution of Gd and Co atoms with respect to the growth direction. For example, a Gd adatom in contact with three surface atom neighbors can have 0, 1, 2, or 3 cobalt neighbors. The sputtering threshold for each type of Gd adatom will be different so those with a low threshold will be selectively removed giving a structural anisotropy. This anisotropic atomic distributions can cause different kinds of anisotropy with respect to the growth direction depending on the type of amorphous film. For example, both easy‐axis (GdCo) and hard‐axis (G...
TL;DR: In this paper, a simple expression for magnetic anisotropy in amorphous ferrimagnetic alloys with slight structural anisotropies on either atomic or microstructural scales was derived.
Abstract: Classical magnetic dipolar interactions can make significant contributions to magnetic anisotropy in amorphous ferrimagnetic alloys with slight structural anisotropies on either atomic or microstructural scales. Simple expressions have been derived for this magnetic anisotropy in terms of structural anisotropy parameters, p, V, and Δx. For an alloy with atomic scale structural anisotropy (pair ordering), p is a measure of alignment of unlike nearest neighbor pairs. For an alloy with aligned, elongated composition inhomogeneities, V is the volume fraction of the inhomogeneities and Δx is the composition difference (atom fraction) between the inhomogeneities and their surroundings. Accounting for magnetic anisotropy observed experimentally in bias‐sputtered GdCo‐based alloy films solely in terms of pair ordering and classical dipolar interactions requires p∼0.015. Accounting for the anisotropy solely in terms of composition inhomogeneities requires V∼0.5 and Δx∼0.1. Although such atomic scale structural anisotropy will be very difficult to detect with currently available experimental techniques, composition inhomogeneities of this magnitude should be easily detectible in x‐ray, electron, or neutron small‐angle scattering experiments. No evidence for anisotropic composition inhomogeneities is seen in x‐ray scattering experiments on micron‐thick bias sputtered GdCo‐based alloy films, although such inhomogeneities may be present in oxygen‐doped, evaporated Gd‐Co films and in some annealed Gd‐Co films prepared by evaporation and by zero‐bias sputtering. Magnetic anisotropy in GdCo‐based films probably involves spin orbit interactions as well as classical magnetic dipolar interactions.
TL;DR: In this paper, the concentration dependence of the uniaxial magnetic anisotropy induced by magnetic annealing has been studied for rapidly quenched amorphous (Fe1-xCox)77Si10B13 (0x1) alloys by using a high sensitivity torque magnetometer.
Abstract: The concentration dependence of the uniaxial magnetic anisotropy induced by magnetic annealing has been studied for rapidly quenched amorphous (Fe1-xCox)77Si10B13 (0x1) alloys by using a high sensitivity torque magnetometer. The induced uniaxial magnetic anisotropy constant was found to be a maximum, 8×103 erg/cm3, around x=0.5 and a minimum, 2×103 erg/cm3, at x=0 and 1. The result could not be explained either by the directional strain or by the directional alignment of impurities or vacancies. The concentration dependence of the uniaxial magnetic anisotropy induced really by magnetic annealing could be explained by the directional pair model of the clustering type proposed by Iwata.
TL;DR: In this paper, the magnetoelastic contribution to the perpendicular anisotropy in sputtered amorphous GdCo and Gd-Fe films was investigated by measuring the coupling energy, internal planar stress and evaluation of the anisotropic due to the substrate constraint.
Abstract: The magnetoelastic contribution to the perpendicular anisotropy in rf sputtered amorphous Gd-Co and Gd-Fe films was investigated by the following three experiments: (1) Measurement of the magnetoelastic coupling energy, (2) measurement of the internal planar stress, and (3) the evaluation of the anisotropy due to the substrate constraint. In these experiments it was found that the magnetoelastic contribution to the perpendicular anisotropy is very sensitive to the preparation condition, especially to the substrate bias voltage V b during sputtering. The contribution of the magnetoelastic component to the perpendicular anisotropy is in an order of 104erg/cc, which corresponds to 10∼30% of the total perpendicular anisotropy.
Patent•
IBM1
TL;DR: A sputtered thin film of an amorphous material composed of a magnetic transition metal X and element Y plus possibly an element Z has low coercivity for domains in the plane, has a well defined and stable magnetic easy axis which is extremely stable without heating above the Curie point, with a high and flat value of permeability from low frequencies to greater than 10 megahertz as discussed by the authors.
Abstract: A sputtered thin film of an amorphous material composed of a magnetic transition metal X and element Y plus possibly an element Z has low coercivity for domains in the plane, has a well defined and stable magnetic easy axis which is extremely stable without heating above the Curie point, with a high and flat value of permeability from low frequencies to greater than 10 megahertz. Metal X can include at least one of Fe, Ni, and Co. Element Y can include at least one of Si and B. Element Z can be included composed of Cr, for example.
TL;DR: In this article, the defect populations in various MnAl permanent magnet materials have been studied by transmission electron microscopy and it is suggested that the good hard magnetic properties in the extruded materials are connected with the low density of antiphase boundaries and the relatively high density of defects such as grain boundaries.
Abstract: The defect populations in various MnAl permanent magnet materials have been studied by transmission electron microscopy. It is suggested by the observations that the good hard magnetic properties in the extruded materials are connected with the low density of antiphase boundaries and the relatively high density of defects such as grain boundaries. The relation between treatment, defect population and magnetic properties will be discussed.
TL;DR: In this article, the exact analytical forms of the low-temperature thermodynamic quantities and correlation functions are obtained for classical one-dimensional Heisenberg ferromagnets with single-site anisotropy including both the systems with an easy axis and with a easy plane.
Abstract: The exact analytical forms of the low-temperature thermodynamic quantities and correlation functions are obtained for classical one-dimensional Heisenberg ferromagnets with single-site anisotropy including both the systems with an easy axis and with an easy plane. The problem has been managed on the basis of the functional integral method. The calculated results have a few leading terms in series-expansion with respect to the reduced temperature, exhibiting the characteristic points borne out in the recent numerical studies. In particular, the longitudinal correlation function and susceptibility of the system with an easy axis show Ising-like behaviours and the transverse counterparts of the system with an easy plane show isotropic XY- or Heisenberg-like behaviours. Physical implications of the calculated results are also discussed.
TL;DR: In this article, the authors recalculated the Smit and Beljers FMR mode frequencies for thin multi-domain magnetic platelets (disks) with uniaxial magnetocrystalline anisotropy K taking the finite aspect ratio of the domains into account.
Abstract: We have recalculated the Smit and Beljers FMR mode frequencies for thin multi‐domain magnetic platelets (disks) with uniaxial magnetocrystalline anisotropy K taking the finite aspect ratio of the domains into account. The magnetic anisotropy axis (z‐axis) was taken to be perpendicular to the disk plane; the external magnetic field H was applied in the disk plane. The demagnetization energy coefficients of the periodic magnetic structures were found by the method of Kaczer and Murtinova. Below magnetic saturation the normalized FMR frequencies are: (a) for stripe domain arrays with H normal to the walls, Ω2+= (1−p)(1+2r−2p)−h2, Ω2−= (1−p)2−h2; (b) for bubble domain arrays, Ω2+= (1−p)(1+r−3p/2)−(1−r−p/2)(1−p)−1h2, Ω2−= (1+r−3p/2)[1−p−(1−p)−1h2], with HA=2K/M, Ω=ω/γHA,h=H/HA, r=2πM/HA and p=NzzM/HA. As the domain aspect (width/height) ratio tends toward zero, p→0 and the Ω2+, − expressions reduce respectively to (a) the stripe resonance expressions given by Smit and Beljers, (b) the first two bubble resonanc...
TL;DR: In this article, the magnetic anisotropy in an amorphous ribbon of Fe 40 Ni 40 P 14 B 6 has been studied using a powder technique, transmission electron microscopy and a torque method.
Abstract: Magnetic anisotropy in an amorphous ribbon of Fe 40 Ni 40 P 14 B 6 has been studied. Domain structures and the in-plane anisotropy were measured as a function of the depth from the ribbon surface by a powder technique, transmission electron microscopy and a torque method. Groups of fine domains diminish with depth. The maximum in-plane anisotropy exists at the surface and the anisotropy decreases one or two orders in magnitude at the center of the ribbon. The data have an obvious connection with the surface topography of the ribbon that is introduced in the melt and quench process.
TL;DR: In this article, the magnetic properties of a mixture A x B 1- x of two orthorhombic anisotropic antiferromagnets with different easy axes are investigated.
Abstract: Magnetic properties of a mixture A x B 1- x of two orthorhombic anisotropic antiferromagnets with different easy axes are investigated. The magnetic easy, intermediate, hard axes are x , z , y axes for the pure A antiferromagnet, while y , z , x axes for the pure B antiferromagnet, respectively. In the middle range of concentration, there appears a single kind of oblique antiferromagnetic phase (OAP) whose spins lie within x y plane in one case, or two different OAP within x z and y z planes, respectively, in the other case. In the latter case, z axis becomes the easy axis in some range of concentration. Applied magnetic field effect and the susceptibility at T =0 are calculated. It is predicted that a mixture Ni x Co 1- x Cl 2 ·2H 2 O would have the latter property.
Journal Article•
01 Jan 1978-Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy
TL;DR: In this article, the Mossbauer effect was applied to EuMn2Ge2 and GdM2Gd and the results showed that the easy axis of magnetization is close to the c-axis, while in the Gd compounds it is in the basal plane.
TL;DR: The magnetic properties of crystallographically ordered ferromagnetic materials are strongly dependent on the presence of crystal defects, because of the effect of defects on the domain structure as discussed by the authors, and therefore, electron microscopy enables the defects and domain walls to be imaged simultaneously and is therefore capable of giving detailed information about their interactions.
Abstract: The magnetic properties of crystallographically ordered ferromagnetic materials are strongly dependent on the presence of crystal defects, because of the effect of defects on the domain structure. Electron microscopy enables the defects and domain walls to be imaged simultaneously, and is therefore capable of giving detailed information about their interactions. In alloys containing Mn, antiphase boundaries (APBs) interact very strongly with domain walls, and tend to act as wall nucleation sites. In MnAl, a possible permanent magnet alloy, in addition to APBs, other defects are also present which tend to behave as wall pinning sites. In some ordered alloys, magnetic anisotropy can be induced by plastic deformation. The resulting changes in the domain structure can be studied by electron microscopy. In spinel ferrimagnets, stacking faults can interact with domain walls.
TL;DR: In this paper, the magnetic properties of uranium pnictides and chalcogenides depend on the orientation of the applied field, and an intermediate ferrimagnetic spin structure of UAs is put into evidence.
Abstract: The magnetic properties of uranium pnictides and chalcogenides depend on the orientation of the applied field. As an example the anisotropic magnetic moments of USe (a ferromagnet) and the anisotropic susceptibility of UAs (an antiferromagnet) are discussed. Furthermore the existence of an intermediate ferrimagnetic spin structure of UAs is put into evidence.
TL;DR: In this paper, the low-field magnetic properties of amorphous (Fe1−xNix)80P10B10 are examined by measuring the local magnetic reversal field and the pinning field as function of position.
Abstract: The low-field magnetic properties of amorphous (Fe1−xNix)80P10B10 are examined by measuring the local magnetic reversal field and the pinning field as function of position. Also measurements of magnetic anisotropy using FMR are reported. The observed magnetic behaviour is discussed generally. The magnetization reversal for the ideal parts of the wires may be described by the process of growth of nuclei present.
TL;DR: In this article, the magnetic properties of V 5 S 8 single crystals have been investigated by susceptibility and torque measurements, and the analysis of these torque curves suggests that spin flopping may occur at 43 kOe, a comparatively low critical field.
TL;DR: In this paper, the authors derived the 95% and 5% magnetic blocking temperatures in a cooling orogen when the spontaneous magnetization is allowed to vary realistically as a function of temperature.