Showing papers on "Magnetic domain published in 1972"
304 citations
TL;DR: Ferromagnetic material is defined by the spontaneous parallel alignment of atomic magnetic moments over relatively large regions of a solid as discussed by the authors, which can be of the ferro-, ferri-, antiferro-, or metamagnetic kind.
Abstract: Magnetism has been a topic of study since the ancient times of science. Judging by the number of papers appearing each year, the group of scientists concerned with the properties of magnetic materials is vastly expanding. The reason for the great interest in this field is not only the wide application which these materials have found in technology, but also the chance to contribute to the understanding of basic physics. The term “magnetic material” in this article refers to a substance which spontaneously exhibits magnetic order below a certain temperature. This magnetic order can be of the ferro-, ferri-, antiferro-, or metamagnetic kind. However, within these magnetic structures ferromagnetism appears to be the most important one. Ferromagnetism is defined by the spontaneous parallel alignment of atomic magnetic moments over relatively large regions of a solid. Magnetic order is limited to compounds which contain elements with incompletely filled electron shells, as for example, the transition ...
193 citations
TL;DR: In this article, a technique for measuring the velocity of a circular magnetic domain in a magnetic field gradient is described, which has been applied to epitaxial garnet films, and results are presented for a film of nominal composition Eu1Er2Ga0.7Fe4.3O12.
Abstract: A technique for measuring the velocity of a circular magnetic domain in a magnetic field gradient is described. The method has been applied to epitaxial garnet films, and results are presented for a film of nominal composition Eu1Er2Ga0.7Fe4.3O12. The technique is compared with other methods of measuring domain wall mobility.
113 citations
83 citations
TL;DR: In this paper, the authors derived an equation of motion for a flexed domain wall in the limit of small damping and small field, and a general method of evaluating the nonlinear mobility of a wall with small dampness and small fields is given.
Abstract: Equations of motion for a flexed domain wall are derived. Velocity dependence of wall thickness is neglected. The orientation angle of the wall‐moment is canonically conjugate to the wall position. Walker's uniform‐motion solution is stable. At higher fields, the wall oscillates. A general method of evaluating the non‐linear mobility in the limit of small damping and small field is given.
75 citations
TL;DR: Hard bubbles are cylindrical magnetic domains which differ from normal bubbles in their static and dynamic properties as mentioned in this paper, and they have a component of motion either to the right or to the left rather than straight down the gradient.
Abstract: Hard bubbles are cylindrical magnetic domains which differ from normal bubbles in their static and dynamic properties.1–3 They form and collapse at fields considerably higher than normal bubble domains (hence the name “hard bubbles”) and, under the action of a gradient in the perpendicularly directed magnetic field, they have a component of motion either to the right or to the left rather than straight down the gradient (right- and left-handed hard bubbles). Under the influence of a small alternating field superimposed on the dc bias field, normal bubbles oscillate in size or strip out in a random manner, whereas hard bubbles tend to strip out in an S-shape and rotate in either a counterclockwise direction for the normal S-shape or clockwise for the reverse S-shape. It has been found that high-speed propagation using permalloy overlay circuits is impossible in materials which are prone to hard bubble formation.
73 citations
TL;DR: In this paper, the authors used polarized light metallography to study magnetic domain configurations in Co5Sm, Co5Y, CO5Ce, and Co5Pr as a function of crystal thickness, and estimated the domain energy in these compounds to be 85, 35, 25, and 40 erg/cm2, respectively.
Abstract: We have used polarized light metallography to study magnetic domain configurations in Co5Sm, Co5Y, Co5Ce, and Co5Pr as a function of crystal thickness. From measurements of equilibrium domain widths on thin crystals, we estimate the domain‐wall energy in these compounds to be 85, 35, 25, and 40 erg/cm2, respectively. From surface domain observations on bulk crystals, we have also made crude estimates of wall energy for Co5Nd, Co5La, and Co5Gd. From these wall energies and published anisotropy constants, we have calculated exchange constants, domain‐wall thicknesses, and critical single‐domain particle sizes. We find this critical particle size to be larger for Co5Sm and Co5Gd than for the other compounds, and suggest that this may partly explain why high coercive forces are more easily attained in powders of these two compounds.
67 citations
64 citations
TL;DR: In this paper, a method for determining the magnetization and intrinsic length of thin magnetic films which support magnetic bubble domains was described, based on a calculation of the energy of the stripe domain configuration and Thiele's curves for circular domain collapse conditions.
Abstract: A method is described for determining the magnetization and intrinsic length of thin magnetic films which support magnetic bubble domains. It is shown that from a calculation of the energy of the stripe domain configuration and Thiele's curves for circular domain collapse conditions, the magnetization and intrinsic length may be determined from the measurements of the film thickness, the domain period, and the bubble collapse field.
64 citations
TL;DR: In this paper, the authors describe a new type of cylindrical domain that can coexist in many of the materials that support NB's, which they call "hard" bubbles.
Abstract: Cylindrical magnetic domains (bubbles) are, by now, well known. Their device applications1 and theoretical description2 have been adequately described. We shall call these bubbles “normal” (NB). In this B.S.T.J. Brief we wish to describe a new type of cylindrical domain that can coexist in many of the materials that support NB's. They were first observed by R. F. Fischer and R. H. Morrow of Bell Laboratories while testing a Y-Bar shift register using a platelet cut from bulk GdTblG. These domains, which we shall call “hard” bubbles (HB), have properties that can be substantially different from NB's.
64 citations
TL;DR: In this article, two types of cylindrical domains are identified by the presence or not of constituent Bloch lines, and the comparative energies of the two kinds of bubbles are calculated including a detailed theoretical treatment of the Bloch line.
Abstract: Arrays of cylindrical domains, “bubbles”, in basal foils of cobalt may be produced by the application of magnetic fields along the c-axis. The bubbles are observed directly in the electron microscope and coexist with plate domains in fields up to 15 kOe. Two types of bubbles exist identified by the presence or not of constituent Bloch lines. The comparative energies of the two types of bubbles are calculated including a detailed theoretical treatment of the Bloch lines. Possible nucleation mechanisms responsible for the formation of both sorts of bubbles are discussed.
Anordnungen von zylindrischen Domanen, „bubbles”, in ebenen Kobaltschichten lassen sich durch Anlegen eines Magnetfeldes in Richtung der c-Achse erzeugen. Die „bubbles” werden direkt im Elektronenmikroskop beobachtet und existieren zusammen mit Tafeldomanen bis zu Feldern von 15 kOe. Zwei Typen von „bubbles” existieren, die durch die Anwesenheit oder Nichtanwesenheit von Teil-Blochlinien identifiziert wurden. Die Energien der beiden Typen von „bubbles” werden berechnet, wobei eine detaillierte theoretische Behandlung der Blochlinien eingeschlossen ist. Mogliche Keimbildungsmechanismen, die fur die Bildung der beiden Sorten von „bubbles” verantwortlich sind, werden diskutiert.
TL;DR: In this paper, the pseudobinary systems are constituted of broad homogeneous regions of cubic and hexagonal Laves phase type and ordering tendencies on crystallographic sites between Al and the transition metal are studied in the hexagonal type.
Abstract: Both pseudobinary systems are constituted of broad homogeneous regions of cubic and hexagonal Laves phase type. Ordering tendencies on crystallographic sites between Al and the transition metal are studied in the hexagonal type. Magnetic investigations have been carried out only in the ordered regime. It is found that electron transfer from Al to the transition metals quenches their moments to the effect that they become nonmagnetic at high Al concentrations. At cryogenic temperatures the magnetization behavior of powdered specimens is complex in the intermediate region of concentration. Considerable magnetic hardness and anisotropy develops, and in DyFe2–DyAl2 pronounced spontaneous increases in magnetization with field occur as a result of the presence of highly energetic domain walls. The complex interplay of effects from disordered magnetic components, the crystalline electric field, and domain‐wall effects is discussed and compared with findings in related systems.
IBM1
TL;DR: In this paper, the Mossbauer effect and nuclear magnetic resonance were used to examine the temperature dependence of the domain and wall hyperfine fields in ferromagnetic iron, and it was shown that an intrinsic temperature dependence exists and may be qualitatively explained by three mechanisms: (i) phonon admixture of the $s$ and $d$ wave functions, (ii) Stoner-like excitations combined with a strongly energy-dependent hyperfine coupling constant, and (iii) changes in the intrinsic $s\ensuremath{-}d$ hybridization
Abstract: The M\"ossbauer effect and nuclear magnetic resonance are used to examine the temperature dependence of the domain and wall hyperfine fields in ferromagnetic iron. The difference between them is attributed to demagnetizing fields and exhibits a temperature dependence different than predicted from consideration of domain and wall spin-wave excitations. It is proposed that this temperature dependence arises from distortion of domain shapes with temperature. After correction to constant volume, the temperature dependence of the hyperfine field is compared with that of new magnetization measurements. It is shown that an intrinsic temperature dependence of the effective hyperfine coupling constant exists and may be qualitatively explained by three mechanisms: (i) phonon admixture of the $s$ and $d$ wave functions, (ii) Stoner-like excitations combined with a strongly energy-dependent hyperfine coupling constant, and (iii) changes in the intrinsic $s\ensuremath{-}d$ hybridization due to the changing magnetization. It is concluded that differentiation of the three mechanisms is not possible by the present type of experiment but requires reliable theoretical estimates of the magnitudes of the various effects.
TL;DR: In this article, the effect of lattice vibrations can explain the observed explicit temperature dependence of the hyperfine field at constant volume and that the deviation of the latter from the temperature dependence at constant pressure is well described by considering the thermal expansion also.
Abstract: The temperature dependences of the magnetization and of the hyperfine field in ferromagnetic metals such as Fe or Ni are different even after transformation to constant volume. It is suggested that the effect of lattice vibrations can explain the observed explicit temperature dependence of the hyperfine field at constant volume and that the deviation of the latter from the temperature dependence of the magnetization at constant pressure is well described by considering the thermal expansion also. Some applications of this model to related problems are discussed.
TL;DR: In this paper, it was shown that the repulsive force of a magnet is proportional to the product of the magnetization of the opposing magnet, which depends on the magnetisation versus demagnetizing field (M versus H ) characteristics of the magnets.
Abstract: Magnetic repulsion is currently under active consideration as a means for providing quiet, frictionless suspension for future tracked ground transportation vehicles and for providing high-reliability, long-lived, friction-free bearings for unique new devices and components. Analytical and experimental results indicate that the superior intrinsic magnetic properties of certain members of a new class of permanent magnet materials, the rare-earth-cobalts (including PrCo 5 and SmCo5), have intrinsic magnetic properties that make them outstanding candidates for such applications. Experimental results verify analytical predictions that repulsive force characteristics of permanent magnet pairs are critically dependent on intrinsic magnetic properties. The repulsive force is shown to be proportional to the product of the magnetizations MM' of the opposing magnets, which, in turn, depend on the magnetization versus demagnetizing field ( M versus H ) characteristics of the magnets. It is predicted that magnets will produce repulsive force in total demagnetizing fields less than their intrinsic coercive force |H T | M H c ; i.e., their intrinsic coercive force can be considered the limiting field value for repulsion operation. Permanent magnet materials suitable for repulsion applications include the barium ferrites and platinum cobalt as well as the rare-earth-cobalts. The intrinsic characteristics of the Alnicos make them unsuitable for repulsion applications. Experiments show that PrCo 5 magnets having twice the residual magnetization M r of oriented barium ferrite magnets of similar size and shape produce four times the repulsive force. PrCo 5 magnets with maximum theoretical magnetization would provide about eleven times the repulsive force of similar barium ferrite magnets.
TL;DR: In this paper, the phase distribution of the transmitted electron wave just behind the film has the information of the magnetization, so one can measure the magnetisation from the interference pattern (hologram) between object wave and reference wave.
Abstract: The electron interference method is discussed which enables to measure the distribution of magnetization in a magnetic thin film. The phase distribution of the transmitted electron wave just behind the film has the information of the magnetization, so one can measure the magnetization from the interference pattern (hologram) between object wave and reference wave. Interference patterns are calculated when 180° domain walls in a ferromagnetic thin film are crossed with the electron biprism. The phase change of transmitted wave corresponding to the magnetization distribution of 180° domain walls was experimentally detected by this method, and the observed interference patterns agreed qualitatively with those calculated.
TL;DR: Saturation magnetization, X-ray and neutron diffraction measurements were made on ferromagnetic alloys in the compositions Ni2MnSb, Ni2mnSn, and Co2mnsSn as discussed by the authors.
Abstract: Saturation magnetization, X-ray and neutron diffraction measurements were made on ferromagnetic alloys in the compositions Ni2MnSb, Ni2MnSn, and Co2MnSn. The compounds investigated have a crystallo-chemical structure of L21 type, with a partial disorder among NiSb atoms in the case of Ni2MnSb and Ni(Co)‒Mn atoms in that of Ni2MnSn and Co2MnSn. It was also found that in Heusler alloys the Ni atoms have zero magnetic moment, but the Co atom has a magnetic moment different from zero. The values of the magnetic moment of Mn and Co atoms were also calculated at 80 °K and found to be μMn = 3.60 to 3.75 μB, μCo = 0.7 μB.
[Russian text ignored]
TL;DR: In this article, it was shown that thin-film permalloy elements often exhibit pole distributions which depend on the applied field and geometry of the element and approximate relations were derived from numerical solutions of a number of specific cases to aid the design and understanding of these circuits.
Abstract: Small thin‐film elements of permalloy are being used in circuits for propagating circular magnetic domains in an adjacent uniaxial wafer. This paper shows that these elements often are not magnetically saturated and, therefore, exhibit pole distributions which depend on the applied field and geometry of the element. Approximate relations are derived from numerical solutions of a number of specific cases to aid the design and understanding of these circuits.
TL;DR: In this paper, a steady-state solution for wall velocity in a magnetic material with orthorhombic anisotropy is used to obtain the conventional expression for the domain wall mobility.
Abstract: Motion of magnetic domain walls in magnetic bubble domain materials is discussed in this paper. A steady‐state solution for wall velocity in a magnetic material with orthorhombic anisotropy is used to obtain the conventional expression for the domain wall mobility. After reviewing the experimental situation, it is concluded that the mobility depends in a predictable way on wall width but that its detailed behavior otherwise is not well understood. Limiting wall velocities, nonlinear velocity‐field behavior, and wall inertial effects are considered, and important consequences of the orthorhombic anisotropy appear here; supporting experimental results for these effects are reviewed. Wall motion damping due to anisotropic energy levels in several of the magnetic rare earths is shown to be a limiting factor in obtaining high mobility materials. Other factors which have been shown to be significant, such as surface smoothness, thermal annealing, and irradiation with X‐rays, are also discussed. Finally, express...
Patent•
28 Jan 1972
TL;DR: In this paper, a cylindrical magnetic domain memory has a plurality of storage channels which can be written into via one domain generating source and read out from via a one domain detecting means without any relative time loss due to the distance of the storage channel from the detecting or generating means.
Abstract: A cylindrical magnetic domain memory having a plurality of storage channels which can be written into via one domain generating source and read-out from via one domain detecting means without any relative time loss due to the distance of the storage channel from the detecting or generating means. Each storage channel circulates the bubbles therein continuously along a closed path. A magnetic switch, when actuated, forces an alteration in said closed path so that a circulating bubble comes near enough to a string of closely packed bubbles in a read-out channel of a magnetic domain transfer line. This creates a repulsive force on the string of bubbles causing the bubble at the very end of the read-out channel to be forced into the bubble detector. A separate string of closely packed bubbles appears in the write-in channel of the magnetic domain transfer line. New information is written into a selected storage channel by closing a magnetic switch associated with the selected channel and forcing the nearest of said string of bubbles through said switch into said storage channel. The force required is provided by generating a bubble and inserting it at one end of said write-in channel, thereby causing sequential repulsion between adjacent bubbles in said string.
TL;DR: In this article, the magnetic recording heads made from nonlinear magnetic materials were used to calculate the magnetic fields for magnetic recording head made from ferrite magnetization curves and showed that as the head drive fields are increased, the resolution of the head deteriorates.
Abstract: Numerical methods are used to calculate the fields for magnetic recording heads made from nonlinear magnetic materials. The nonlinear model used in the study fits ferrite magnetization curves well and requires little computer time for evaluation. Results show that as the head drive fields are increased, the resolution of the head deteriorates.
TL;DR: In this article, it was shown that the flow stress and the stress relaxation of Ni and Ni-Co alloy single crystals in a plastic region are affected significantly by applying an alternating magnetic field.
Abstract: It is shown that the flow stress and the stress relaxation of Ni and Ni-Co alloy single crystals in a plastic region are affected significantly by applying an alternating magnetic field This “magneto-plastic effect” can be interpreted in terms of a concept that oscillating magnetic domain walls give a force on the dislocation The magnitude of the shear stress drop caused by this effect depends upon the plastic strain, total strain rate, magnetostriction constants, total volume swept out by the oscillating domain walls and frequency of the alternating magnetic field The activation volume of the glide dislocation in thermally activated process is reduced to about one half of its original value by this effect Further, on the basis of the experimental results obtained through this effect, a role of the short range stress to the flow stress is discussed in some detail
TL;DR: In this paper, a serial access memory is proposed based on the propagation of cross-tie walls and Bloch lines along domain walls in thin magnetic films, which shows promise because of the speed and density, the polycrystalline material, the large temperature range, and easy detection with a loop.
Abstract: A serial access memory is proposed based on the propagation of cross-tie walls and Bloch lines along domain walls in thin magnetic films. The techniques used to propagate bubbles may be applied to cross-tie walls and Bloch lines. This method shows promise because of the speed and density, the polycrystalline material, the large temperature range, and easy detection with a loop. The expected speed makes possible cheap detection, and as a result the need for magnetic logic is decreased. With propagation velocities within the range of domain tip velocities, a 100 MHz stepping rate can be expected. At this rate a 0.5 millivolt signal can be obtained from a loop as a Bloch line passes beneath it.
TL;DR: In this paper, a review of the magnetoelectric effect is given, which includes thermodynamic formulation, magnetic symmetry and magneto-lectricity, experimental considerations and known magnetolectric materials, atomic mechanisms responsible for magnetoelectricity and the temperature dependence of the ME susceptibility.
Abstract: A review is given of the magnetoelectric (ME) effect. Topics covered include thermodynamic formulation, magnetic symmetry and magnetoelectricity, experimental considerations and known ME materials, atomic mechanisms responsible for magnetoelectricity and the temperature dependence of the ME susceptibility, and present and potential applications in materials research and devices. It is pointed out that ME measurements can be useful in magnetic structure and Neel temperature determinations, studies of critical behavior, changes in magnetic symmetry induced by external fields, and studies of the motion of antiferromagnet domain walls. Among potential device applications of ME materials are a realization of the gyrator and read-only memories with subnanosecond retrival times.
Patent•
02 Feb 1972
TL;DR: In this paper, the authors proposed a circular magnetic domain device which includes a layer of uniaxial magnetic material formed on or in a surface of a magnetic member having at least one easy magnetization direction substantially parallel to the surface thereof, the layer material having a single unique easy magnetisation direction substantially normal to the said surface.
Abstract: A circular magnetic domain device which includes a layer of uniaxial magnetic material formed on or in a surface of a magnetic member having at least one easy magnetization direction substantially parallel to the said surface thereof, the layer material having a single unique easy magnetization direction substantially normal to the said surface. A first pattern of a soft magnetic material is interposed between the uniaxial magnetic layer and the magnetic member, and a pattern of an electrically conductive material is formed on the upper surface of the uniaxial magnetic layer. The magnetic member can be formed on the surface of a non-magnetic substrate, and a second soft magnetic pattern can be formed on the upper surface of the uniaxial magnetic layer. The second soft magnetic pattern can be complimentary to, and in register with, the first pattern in order to obtain higher propagation rates for the circular magnetic domains.
TL;DR: In this paper, a review of thin magnetic-film magnetometers used for magnetic field measurement is presented, and a summary of the magnetometer properties and their performance is provided, as well as a comparison of different types of magnetometers.
Abstract: Thin magnetic-film magnetometers used for magnetic-field measurement are reviewed and compared. A large variety of magnetic thin-film magnetometers have been constructed, and in some cases their properties are unique. A summary of thin-film magnetometers and their performance is provided.
TL;DR: Magnetization measurements at low and high fields are presented and analyzed, using a simple model, in this paper, where the high field susceptibility has a strong maximum at 57 at. % Cu.
TL;DR: In this article, the authors computed the ferromagnetic resonance absorption line in polycrystalline ferrites in the independent grain approximation taking account of the magnetic crystallographic and magnetostriction anisotropies.
Abstract: The ferromagnetic resonance absorption line is computed in polycrystalline ferrites in the “independent grain” approximation taking account of the magnetic crystallographic and magnetostriction anisotropies. The results obtained show that the influence of elastic stresses on the shape of the absorption line is analogous to the effect of the magnetic crystallographic anisotropy.
Patent•
27 Jun 1972TL;DR: In this paper, the authors proposed a magnetic domain device in which T-bar patterns made of permalloy, etc. are formed on a magnetic film for producing magnetic single wall domains and a rotating magnetic field is generated in said magetic film to transfer magnetic domain.
Abstract: In a magnetic domain device in which T-bar patterns made of permalloy, etc. are formed on a magnetic film for producing magnetic single wall domains and a rotating magnetic field is generated in said magetic film to transfer a magnetic domain, a driving system includes the connections of resonating capacitors and X and Y coils for forming a rotating magnetic field. The driving power for the device is much reduced by resonating the circuits comprising the coils and the capacitor at the frequency of the power source.