Showing papers on "Magnetic domain published in 1976"

Different contributions of the two cobalt sites to the magnetocrystalline anisotropy of YCo 5 and related compounds

Abstract: The properties of permanent magnets based on RCo 5 compounds arise from their strong uniaxial anisotropy. The anisotropy field at 4.2 K in YCo 5 is about 200 kOe. A polarized neutron study of YCo 5 revealed a very large orbital contribution to the magnetic moment on the Co I (2c) site, which indicates that the major part of the cobalt anisotropy originates from this site. The variations of the magnetic anisotropy of YCo 5 which occur when different substitutional atoms (Ni, Fe, Co pairs) modify the ideal structure, are in agreement with this view.

Magnetization, magnetic anisotropy, and domain patterns of Fe80B20 glass

Abstract: The thermomagnetization behavior, magnetic anisotropy, and magnetic domain patterns of ribbons of the newly synthesized Fe80B20 glass have been examined. This glass exhibits a saturation moment of 1.99 μB/Fe atom, a ferromagnetic Curie temperature of 647 K, and a crystallization temperature of ∼660 K. The direction of magnetic anisotropy lies at ∼60° to the ribbon axis in the plane of the ribbon. Large domains, elongated parallel to the ribbon axis, are observed.

Bubble domain memory materials

Abstract: The selection and preparation of bubble domain materials is discussed in the light of materials requirements for bubble domain memories. The history of bubble domain materials development is outlined with emphasis on the discovery and exploitation of two types of materials, magnetic garnets and amorphous magnetic alloys. It is shown how the great compositional flexibility of the garnet system has led to many garnet choices for device use without imposing undue hardship on the materials developer and supplier, and how liquid phase epitaxy of garnet films is a simple way of providing reproducibly films that meet device requirements. Amorphous magnetic alloys are discussed with emphasis on Gd-Co-Mo compositions. In the search for small bubble materials, it is pointed out that both garnets and amorphous alloys have limitations. In the former case, q will usually be too low and in the latter case, the drift of properties with temperature may be unacceptable.

The use of domain observations in understanding and improving the magnetic properties of transformer steels

Abstract: The observation of the domain pattern of 3% grain-oriented silicon-iron (transformer steel) by the Kerr magneto-optic effect has enabled a greater understanding of the basic magnetization processes of this material to be obtained. In this review paper, an attempt is made to describe recent progress in this field of study. The principal commercial criterion of transformer steel is the power loss and therefore many attempts have been made to correlate the domain observations with measured loss. The increased knowledge of the shape of the loss per cycle against frequency characteristic has shown that the anomalous loss is responsible for approximately 50% of the total loss. Experimental results are described which attribute the anomalous loss to many causes such as the occurrence of domain walls, domain wall angles and configuration, variation of wall spacing with lamination thickness, non-uniform and non-repetitive wall motion (pinning), grain size effects, lack of flux penetration (wall bowing) and domain nucleation. In addition, experimental domain observations are described which explain the optimum thickness of transformer steel for minimum loss and the variation of power loss with applied stress.

Magnetic Domain Structure of an Amorphous Fe-P-C Alloy

Abstract: The domain structure of an amorphous Fe80P13C7 alloy ribbon produced by the centrifugal solidification technique was investigated using the magnetic powder pattern technique. Two different types of domains (a maze domain and a 180°-domain) were observed on the specimen surface. The relationship between the domain structure and the magnetization process was also investigated. The results showed that some of the 180°-walls, which ran nearly parallel to the long axis of the ribbon, caused the hysteresis in the magnetization curve, while the maze domain was responsible for the difficulty in obtaining the saturation in magnetization. The maze domain arises probably from the uniaxial magnetic anisotropy having the direction of easy magnetization perpendicular to the surface. This anisotropy seems to be caused by the magnetoelastic coupling between positive magnetostriction and internal stress in the specimen.

Anisotropy and coercivity in SmCo 5 -based compounds

Abstract: The anisotropy of the RCo 5 -based compounds depends not only on the local anisotropies but also on exchange interactions of the Sm and Co sublattices. This result allows an accurate determination of the Sm3+anisotropy in SmCo 5 and SmCo 3.5 Cu 1.5 ; the anisotropic properties of these compounds are discussed in terms of crystal field. The mechanism of domain wall displacement has been studied on a single crystal of SmCo 3.5 Cu 1.5 by means of Kerr effect and high field magnetization measurements. Domain walls are trapped in copper rich regions where exchange and anisotropy are lower. Magnetic aftereffect measurements show that in fact the trapping effect is in competition with a kink creation mechanism. On this basis, the thermal variation of the coercive field of the SmCo 5 -based compound is explained.

Magnetic Domain Structure of an Amorphous Fe-P-C Alloy

Abstract: The domain structure of an amorphous Fe80P13C7 alloy ribbon produced by the centrifugal solidification technique was investigated using the magnetic powder pattern technique. Two different types of domains (a maze domain and a 180°-domain) were observed on the specimen surface. The relationship between the domain structure and the magnetization process was also investigated. The results showed that some of the 180°-walls, which ran nearly parallel to the long axis of the ribbon, caused the hysteresis in the magnetization curve, while the maze domain was responsible for the difficulty in obtaining the saturation in magnetization. The maze domain arises probably from the uniaxial magnetic anisotropy having the direction of easy magnetization perpendicular to the surface. This anisotropy seems to be caused by the magnetoelastic coupling between positive magnetostriction and internal stress in the specimen.

Asphericity in the magnetization distribution of holmium

Abstract: In a spiral magnetic structure an aspherical magnetic moment distribution around the ions gives rise to a new set of diffraction lines indexed as third-order satellites. Neutron-diffraction measurements have been made on single crystals of holmium and a ${\mathrm{Ho}}_{0.9}$${\mathrm{Sc}}_{0.1}$ alloy to determine the magnetic structures as a function of temperature, and measure the intensities of the third-order satellites. From these intensities the experimental asphericity of the magnetization density is compared to that calculated with a single-ion model. The agreement between theory and experiment is qualitative; the experimental intensities being larger by a factor of \ensuremath{\sim} 1.5. The temperature dependence of the third-order satellite is in good agreement with a simple model proposing exchange splitting of the free-ion multiplet, with a negligible crystal-field interaction.

Magnetic domain wall bowing in a perfect metallic crystal

Abstract: From the equation of motion for a domain wall in a perfect crystalline sheet, expressions for the steady‐state mobility, power loss, and wall profile are calculated in terms of the magnetic eddy current field acting on the wall. An exact expression for the eddy current field for a given wall shape is derived, and an iteration procedure is used to obtain approximate results. At low wall velocity (0.16MsHAd/e somewhat smaller than unity, where Ms is the saturation magnetization, HA is the applied field, d is the sheet thickness and e is the wall energy per unit area) the equation for the wall profile, x=xw(y), is approximately xw= (MsHAd2/πe) [(Jm=1,3,5... 1/m3)−1 Jm=1,3,5... [sin(mπ/2) m−4](1−cosmπy/d) −(πy2/d2)], where the x axis is normal to the wall and the y axis is normal to the sheet, with the origin at the middle of the sheet. At some critical velocity, or applied field, which in rough approximation is given by 0.16MsHAd/e equal to unity, no steady‐state solution exists. Severe wall bowing cannot oc...

Theoretical study of vector magnetization distribution using rotational magnetization model

Abstract: In magnetic recording, the recording fields are essentially vectorial, and the magnetization process in the recording medium has to be analyzed using vector magnetization. From this fact, a vector magnetization distribution in the recording medium must be evaluated by both magnitude and direction of magnetization. This paper describes the vector magnetization distributions obtained by a new method, using reversible and irreversible rotational magnetization model of single domain acicular particles with uniaxial anisotropy. Calculations are done self-consistently at an instant when the head field is applied and after it is removed. Although the results are, at present, limited to the case where the recording medium is standing still, they show quite good agreement with the results of scaled up model experiments, and can clearly explain the demagnetization mechanism in terms of the vector rotation. This new calculation method will, in principle, display its real power in analyzing the dynamical recording process when the recording medium is moving along the head or the head field is changing.

Soft Ferromagnetic Properties of Some Amorphous Alloys

Abstract: In rapidly quenched amorphous alloys (Fe 1 − x Co x ) 80 P 13 C 7 and (Fe 1 − x Co x 75 Si 15 B 10 , the zero magnetostrictive alloys are remarkably soft magnetic materials, while the magnetostrictive alloys have rather large coercive forces [1]. To investigate the effect of magnetostriction on the properties of the BH loop, some fundamental magnetic properties of these alloys were studied. The magnetic domain pattern observed by Bitter's method shows a periodic domain structure consisting of 180° and maze domain walls in all the magnetostrictive alloys, suggesting the existence of a magnetic anisotropy with an easy axis that varies locally. The estimated value of the anisotropy energy varies with x similarly to the concentration dependence of the magnetostriction. The coercive force also varies with x and is nearly proportional to the ratio of the magnetostriction to magnetization. It is, therefore, considered that the anisotropy is caused by the anisotropic internal stress field, and that the stress fluctuation which inevitably exists is responsible for the large coercive force.

On the Resistive State of Current-Carrying Rods of Type 2 Superconductors in Longitudinal Magnetic Fields

Abstract: The resistive state of the current-carrying type 2 superconducting rod in a longitudinal magnetic field was studied for Pb-T l alloys. The herical structure composed of two kinds of domains was found from the measurement of the potential distribution on the sample surface. The larger domain was confirmed directly to be in a flux flow state and the other domain was estimated to be in a normal state by some theoretical considerations. The direction of the boundary between these domains was dependent only on the direction of magnetic field at the surface.

Magnetic moments for mixed substituted rare earth iron garnets

Abstract: The molecular field coefficients for the individual rare earth iron garnets have been determined by a trial and error procedure using the phenomenological molecular field theory of Neel and the experimental curves for each rare-earth iron garnet. These results were then used to calculate magnetic moment-temperature curves for various film compositions subject to the conditions that the lattice parameter of the film and λ

Magnetic domain contrast in backscattered electron images obtained with a scanning electron microscope

Abstract: Magnetic domain contrast in backscattered electron images of an iron-3% silicon specimen has been measured at 50–200 kV by using a high-voltage scanning electron microscope, and a detailed study has been made of the dependence of the contrast on detection direction and accelerating voltage. The contrast is maximum at a take-off angle of about 60° for both 45° and 60° specimen tilts. The contrast is approximately proportional to the 3/2 power of the accelerating voltage, as shown by Newbury, Yakowitz and Myklebust (1973) and by Fathers, Jakubovics, Joy, Newbury and Yakowitz (1973 b, 1974). The resolution of domain images and the material depth effective for the magnetic contrast have been studied. They are also dependent on the detection direction: the resolution is high and the depth is small at a lower take-off angle than that corresponding to the mirror-symmetrical direction, whereas they are low and large, respectively, at a higher take-off angle. The contrast mechanism is also discussed on th...

Bubble domain field access device modeling part I: The magnetization problem

Abstract: A continuum magnetostatic energy model for describing field access bubble domain devices is introduced and a prescription for solving the modeling problem is given. Minimization of the magnetostatic energy yields an integral equation defining the magnetization in the permalloy and the solution of this magnetization problem is described in detail. Application of the formalism to the calculation of demagnetizing fields for uniformly magnetized patterns is discussed as are the solutions of the magnetization problem for simple geometries. Techniques for improving the speed and convergence of the calculations are suggested based upon the proposed interpolation scheme and are compared to other computational methods such as Fourier series expansion. In a second paper (Part II) the solution of the magnetization problem is used to calculate the drive fields acting on the bubble as well as to calculate the magnetoresistance of a chevron stretcher detector under various in-plane drive field conditions.

An analytical design theory for field-access bubble domain devices

Abstract: This paper describes the derivation and applications of an analytical model for magnetic bubble domain propagation. A fleld-access bubble device is treated as a magnetic circuit, emphasizing fluxes rather than fields as in most previous treatments. The energy changes are calculated within the bubble domain rather than in the propagation pattern, making possible a simple analytical-graphical process for predicting device operating margins. Agreement with a large number of device experiments is shown to be good. Closed-form expressions are derived which relate the essential features of the operating margin to device geometry and bubble material magnetic properties. The application of this model to device diagnosis, optimization, and scale down is discussed.

Traction force on paramagnetic particles in magnetic separators

Abstract: The magnetic force, which attracts paramagnetic particles towards a magnetized ferromagnetic wire, is calculated for the geometry which is most likely to be used for magnetic separation. It is demonstrated that the magnetic field problem has an analytic solution, from which the maximum force is obtained analytically as a very simple expression. The choice of optimum wire diameter becomes less critical than in the estimation of Oberteuffer, since the maximum is flatter, but the position of this maximum is not changed significantly, and is the same for all practical purposes.

Magnetic Structure of TbCu1-XZnX

Abstract: Magnetic structure of TbCu 1- X Zn X system with the cubic CsCl type structure has been studied by neutron diffraction and magnetic measurements. In Cu-rich region ( X <0.5). the antiferromagnetic structure is conserved, which is TbCu type with (π π 0) mode. When X increases further, the magnetic state suddenly transforms to a ferromagnetic state with canted spin arrangement of which antiferromagnetic mode is (π π 0). In the region with the canted spin arrangement (0.5< X <0.7), the magnetic state approaches to a simple ferromagnetic state with increasing temperature, and transforms not only to a complete ferromagnetic state with increasing temperature, and transforms not only to a complete ferromagnetic state, but also directly to a paramagneticstate. This magnetic phase diagram and properties are fairly well explained by the theory based on the s-f exchange interaction with the low density 4s-electrons, assuming the electronic band structure of YZn.

Interaction between local magnetic moments in metals. I

Abstract: For pt.I see ibid., vol.6, p.233 (1976). An improved version of the Caroli-Blandin (1966) form of the effective interaction between local magnetic moments in metals is discussed. It is shown to explain some aspects of the magnetic properties of the Heusler alloy Pd2MnSn and the dilute magnetic alloys CuFe and CuMn. In this context the ordered alloy Cu3Mn is also discussed.

Magnetic properties, magnetic structure and crystal field in equiatomic rare earth-magnesium compounds

Abstract: The magnetic properties and magnetic structure of some equiatomic rare earth-magnesium compounds RMg (R=Tb, Dy, Ho, Er) have been investigated by magnetization measurements on single crystals and neutron diffraction. The magnetic structures are all different and intermediate between the ferromagnetic and antiferromagnetic (00 pi )-type structures. The magnetization anisotropy in high fields allows a determination of crystal field parameters. The fourth-order parameter A4(r4) is positive in RMg compounds contrary to isomorphous compounds with transition metals.

Magnetic separation of the second kind: Magnetogravimetric, magnetohydrostatic, and magnetohydrodynamic separations

Abstract: Magnetogravimetric, magnetohydrostatic, and magnetohydrodynamic separation techniques can be classified as magnetic separations of the second kind. Magnetic separation of the first kind (ordinary magnetic separation) relies on the inherent magnetic susceptibility of the material to be separated. When the medium of separation rather than the separated particles is made magnetizable, a new system of gravity separations can result (magnetic separation of the second kind). In magnetogravimetry, a colloidal solution of a ferro- or ferrimagnetic substance (magnetic fluid) acts as the separation medium. Magnetohydrostatic separations are conducted in an aqueous solution (or melt) of a strongly paramagnetic salt. Magnetohydrodynamics applies the Faraday effect (mutual orthogonality of the force thrust, electric, and magnetic fields) on suspended conducting minerals in an electrolytic solution placed in crossed electric and magnetic fields. The first technique was pioneered mainly in the United States, while the last two techniques were pioneered by Bunin and Andres in the Soviet Union and introduced to the West by Andres. The principles underlying the three separation techniques will be discussed.

The motion of small paramagnetic particles in a high gradient magnetic separator

Abstract: The force balance equation describing the motion of a small paramagnetic particle near a cylindrical ferromagnetic collector is presented in general form. The capture cross-section for a particle approaching a bare wire is found to be a function of the coefficient of magnetic force and the magnetization of the cylinder. Calculations show that the assumption of potential flow versus creeping flow is a critical one which can change the capture cross-section by as much as a factor of three.

Increased domain wall velocities due to an orthorhombic anisotropy in garnet epitaxial films

Abstract: Magnetic domain wall velocities are compared for (Eu,Lu)3 (Fe,Al)5O12 films grown on (110) and (111) Gd3Ga5O12 substrates. The (110) films have an orthorhombic anisotropy which is partly stress induced and partly growth induced; the (111) films are uniaxial. Wall velocities approaching 500 m/sec have been measured in the orthorhombic films while the (111) films exhibit a maximum velocity of ∼5 m/sec. The results are compared with theoretical limiting velocities.

Magnetic Properties of Fe and Co Based Amorphous Alloys

Abstract: Detailed magnetic measurements were carried out on amorphous alloys: Fe‐Co‐P‐C, Fe‐Cr‐P‐C and Co‐Fe‐SI‐B. The saturation magnetizations (Ms) are obtained for these alloys using the formula dM/dH = Ms(a/H2) + Xo. The spin‐wave dispersion coefficients (D) are also obtained from the low temperature magnetization measurements. The contribution of the structural disorder to the magnetic properties is found directly by comparing the results for the amorphous Fe80P13C7 and Co75Si15B10 with those for the corresponding single‐phase crystalline bcc Fe‐P‐C and hcp Co‐Si‐B, which were obtained by careful thermal treatments. The results show that the structural disorder has influence on the magnetic excitations rather than the magnetic moment.