Showing papers on "Magnetic anisotropy published in 1976"

Simple analysis of torque measurement of magnetic thin films

Abstract: In order to analyze experimental data of torque measurements for magnetic thin films, a (L/H)2‐vs‐L plot is proposed, where L represents the torque of a film in a field of H whose direction is 45° to the film plane. The saturation magnetization M and perpendicular anisotropy energy K⊥ are obtained without any approximation from the slope A and intercept B of this plot as follows: M= (2B)1/2/V, K⊥= (B/V) (1/A−4π/V), where V is the volume of the film.

Ring-current effects in the Nmr of nucleic acids: a graphical approach.

Abstract: The spatial dependence of the ring-current magnetic anisotropy of nucleic acid bases is presented in a series of graphs in cylindrical coordinates. The curves may be used to calculate the ring-current shift at a point in a cylinder of radius 10A extending 8 A above and below each ring of the base. These distance effects are found to influence considerably the predicted chemical shifts of nucleic acid protons, particularly in RNA duplexes. The contribution of polarization (electric field) effects and the diamagnetic anisotropy of individual atoms (local Δχ) are briefly discussed.

Magnetic Properties of SrRuO 3 Single Crystal

Abstract: Magnetic measurements on single-crystal specimens of SrRuO 3 having perovskite structure were made by a magnetic balance. It was found that the ferromagnetic moment in SrRuO 3 could be technically saturated in a finite magnetic field along an easy axis, . The spontaneous moment was estimated to be 1.10±0.09 µ B at 4.2 K. The thermomagnetic curve could be well reproduced by the one calculated in the molecular-field approximation for S =1/2. The χ -1 vs T curve measured obeys the Curie-Weiss law from 300 K to 700 K. SrRuO 3 has a fairly large amount of cubic magnetocrystalline anisotropy (\(K_{1}{\cong}-1.6{\times}10^{6}\) erg/cm 3 at 4.2 K.). It is concluded that the reduced ferromagnetic moment in this case is smaller than the one expected for the low-spin state of Ru ions at the octahedral sites, and that this can not be attributed to any technical magnetization processes.

Spin-order and magnetic properties of BaZn 2 Fe 16 O 27 (Zn 2 -W) hexagonal ferrite

Abstract: Mossbauer and magnetic measurements have been carried out both on single crystals and polycrystalline samples of BaZn2Fe16O27 (Zn2-W) hexagonal ferrite. The saturation magnetization at 0 K and at room temperature turns out to be very high, that is, 123 and 79 Gauss·cm3/g, respectively. The results have been interpreted by assuming a local reversal or a weakening of the Fe3+ magnetic moments due to the perturbing action of Zn2+ ions. The magnetic anisotropy is confirmed to be uniaxial with an anisotropy field at room temperature of 12.500 Oe.

Magnetic, seismic, and other anisotropic properties of rock fabrics

Abstract: Anisotropy in any physical property of a material implies that the response of the material to an applied field depends on the direction in which the field is applied. In single crystals anisotropy may be an intrinsic property (Nye I964), but in rocks it is usually determined by the integrated effects of many fabric elements, which may interact in complex ways. The specification of an anisotropic property necessarily implies that on the scale of interest the body may be treated as homogeneous. Anisotropic properties are important in geology in two distinct, though related, ways. Firstly, a knowledge of anisotropy is important for a full understanding of geological processes - the influence of rheological anisotropy in deformation is an obvious example. Secondly, measurement of anisotropy may be used to provide information about the fabric of rocks. In comparison with other methods of studying fabric, the relative usefulness of any anisotropic property is determined by a balance between the ease and speed with which it can be measured, the extent to which the contribution of different fabric elements can be resolved and the amount of information (necessarily limited by symmetry) which is carried by the anisotropic property. This paper is principally concerned with the usefulness of magnetic (?2) and seismic (?3) anisotropy in fabric studies; other anisotropic properties will be considered briefly in ?4. In many ways magnetic and seismic anisotropy represent opposite extremes. The former is limited to measurements on the scale of a hand sample and for such specimens measuring procedures are well established. Since magnetic anisotropy is one of the least complex of the anisotropic properties of rocks, in terms of the multiplicity of fabric elements involved, its analysis and its consequent applicability and limitations are relatively well understood. By contrast seismic anisotropy is, at the outset, a more complicated phenomenon. It too may be measured on the laboratory scale, but the possibility that excites greater interest is that of in situ determination of anisotropy on a much larger scale, on regions of the crust and upper mantle which are inaccessible to direct observation, but of great interest tectonically. The physical constraints

Magnetization and magnetic anisotropy in evaporated GdCo amorphous films

Abstract: Saturation magnetizations and magnetic anisotropy constants were determined for a series of amorphous GdCo films prepared by thermal evaporation. The films covered the composition range from Gd0.05Co0.95 to Gd0.40Co0.60 and were studied by means of ferromagnetic resonance and a force balance magnetometer. The films, in contrast to those prepared by sputtering, had a hard perpendicular direction of magnetization when Co was less than 91 at.%, and easy and moderate directions within the plane of the film. The anisotropy constant can be expressed in terms of sublattice magnetizations by Ku=0.660MCo2 +2.218MCoMGd+0.097MGd2. The results are explained based on a pair‐ordering mechanism. The composition and temperature dependence of saturation magnetization is essentially the same in evaporated and sputtered films.

Nonmajor cubic symmetry axes of easy magnetization in rare-earth-iron-laves compounds

Abstract: Unusual [$uuw$]- and [$uv0$]-type axes of easy magnetization have been observed in some cubic rare-earth-iron Laves compounds. The presence of these directions of spontaneous magnetization can be accounted for, within the phenomenological treatment of the magnetic anisotropy, by including eighth-power direction-cosine terms in the power expansion of the magnetic anisotropy energy. It will also be shown that the single-ion model predicts the existence of these directions. The conditions imposed on the bulk magnetic anisotropy constants are derived. Typical values of these constants in rare-earth-iron Laves phases are calculated using the single-ion model.

Magnetic properties of amorphous Tb‐Fe thin films prepared by rf sputtering

Abstract: The magnetic properties of amorphous TbxFe1−x films prepared by rf cosputtering were studied. For 0.15

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.

Magnetocrystalline anisotropy of rare earth intermetallics

Abstract: The peculiarities of the magnetocrystalline anisotropy of the rare earth intermetallics are discussed briefly. Only the part of the magnetic anisotropy energy related to the rare earth ion system is analyzed. This anisotropy in most cases can be satisfactorily described in terms of a single-ion model. Theory and experiment relating to magnetocrystalline anisotropy of RCo 5 compounds are reviewed as an example (R is one of the rare earths or yttrium).

Effects of deformation and annealing on magnetic amorphous alloys

Abstract: Effects of deformation and annealing on the magnetic anisotropy, stress relief rate, and fracture strain of amorphous alloys Fe 80 B 20 and Fe 40 Ni 40 P 14 B 6 were studied. It was found that deformation increases the anisotropy and the stress relief rate, while annealing reduces them. The results are shown to be consistent with the existence of structural defects in the amorphous alloys.

Magnetic properties of amorphous Gd-Fe films prepared by evaporation

Abstract: Amorphous GdxFe1−x films with 0.18

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.

Magnetic properties of amorphous Fe‐Si thin films

Abstract: Magnetic properties of Fe1−xSix sputtered films were investigated in the range 0⩽x⩽0.43. The films were found to be amorphous for the compositions x⩾0.20. The magnetic moment change upon crystallization depends on x. The magnetostriction seems to be a predominant factor in determing the hysteresis loops. The films in the amorphous state are magnetically soft. An in‐plane uniaxial anisotropy was observed. The direction of the easy axis depends upon x.

Advances in Ferromagnetic Metallic Glasses

Abstract: Recent developments in transition metal glasses have resulted in the synthesis of an iron‐rich glass (nominal composition, Fe80B20) in continuous ribbon form. The as‐quenched glass shows a saturation moment of 1.99 μB/Fe atom at 4.2 K, an induction of 16 kG at 300 K, a ferromagnetic Curie temperature of 650 K, a saturation magnetostriction of 30 × 10−6 and a coercivity Hc of about 100 mOe. Large domains, elongated parallel to the ribbon axis, are observed. Both Mossbauer and FMR data indicate that the magnetic anisotropy (K = 3 × 104 erg/cm3) is in the ribbon plane. Evidence is presented that boron donates less electrons to the d‐band of transition metal atoms compared with other glass‐forming metalloids such as phosphorous. Some of the low‐field properties include: the permeability at 20 G, μ(20) = 1,700, μmax = 102,000 and core‐loss, W ≃ 0.3 to 0.4 watts/kg at f=1 kHz and Bmax = 1 kG. Field annealing results in improvements in these properties: A typical field‐annealed toroid shows Hc∼40 mOe, μ(20) = 4,...

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.

Magnetocrystalline Anisotropy of SrRuO 3

Abstract: Magnetocrystalline anisotropy in SrRuO 3 is measured by a torque magnetometer using a single-crystal sample. It is found that it has a large amount of magnetic anisotropy. ( K 1 =6.35×10 6 , K 2 =(-)10.8 4 ×10 6 and K 3 =5.33×10 5 erg/cm 3 at 4.2 K.), where the anisotropy energy is expressed as, \begin{aligned} E_{\text{K}}{=}K_{1}\cos^{2}\theta+K_{2}\cos^{4}\theta+K_{3}\sin^{4}\theta\cos^{2}\phi\sin^{2}\phi. \end{aligned} The a - and b -axes of the crystal are two easy axes of magnetization, but the c -axis is only a stable direction of magnetization in a magnetic field. Torque curves observed (in the (010) and (110) planes) are rather unusual, but are analyzed by a `partially rotatable magnetization vector' model. Temperature variations of K 1 , K 2 , and K 3 were also investigated. Some possible origins of the large anisotropy in SrRuO 3 are suggested.

Magnetoresistive magnetic head

Abstract: A magnetic head for detecting information-representing magnetic fields on a magnetic recording medium and comprising an elongate magneto-resistive element of a magnetically anisotropic material which at its ends has contacts for connection to a current or voltage source. In order to linearize the playback characteristic of the element, the easy axis of magnetization coincides with the longitudinal direction of the element and means are present which force the current to travel at an angle of minimum 15° and maximum 75° with the longitudinal direction. These means consist in particular of equipotential strips provided on the element.

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.

Low‐field magnetic properties of Fe80B20 glass

Abstract: The low‐field magnetic properties of Fe80B20 glass are examined. Measurements are reported for straight strips, stressed and unstressed, for as‐cast/as‐wound toroids and for field‐annealed toroids. Due to the positive magnetostriction (λs=31×10−6) of the alloy, the low‐field magnetic properties of strips are improved by applied tensile stress. Similarly, toroids annealed to remove compressive stresses induced by winding (cooled in a magnetic field) are superior to unannealed toroids. Field‐annealed Fe80B20 toroids show a coercivity of ∼0.04 Oe, a permeability of 4000 at 20 G, and a remanence ratio of 0.77Bs(Bs=16 kG). The approach of the magnetization to saturation for field‐annealed toroids indicates a magnetic anisotropy energy density of about 5×103 erg/cm3. This low magnetic anisotropy, as well as the low coercivity and high resistivity (145 μΩ cm±10%) exhibited by Fe80B20 lead to low core loss under ac excitation, i.e., 0.10 W/kg (measured at 1 kHz and a maximum induction of 1 kG on a field‐annealed ...

Single crystal magnetization of ErAl2 and interpretation in terms of the crystalline field

Abstract: Measurements are reported of the magnetization of single crystals of ErAl2 between 4.2K and 16K for magnetic fields up to 150 kOe applied along the (111), (110) and (100) directions. The results are interpreted in terms of the crystal field using a two-dimensional molecular-field approach. Within this microscopic description of the magnetization and the related magnetocrystalline anisotropy the authors use only two temperature-independent crystal field parameters and the Curie temperature. A least-square fitting procedure gives B4=1.10*10-4 meV, B6=-1.34*10-6 meV and Tc=14K. With these parameters they obtain good agreement between calculated and measured magnetization curves.

Sublattice magnetization and anisotropy properties of Ba3Co2Fe24O41 hexagonal ferrite

Abstract: Mossbauer and magnetization measurements have been carried out in Co2-Z compound. The Mossbauer data have been correlated to measurements of magnetization and anisotropy constants. The temperature dependence of the second-order anisotropy constant K2 turn out to be of single-ion origin and essentially determined by the magnetization of the sublattices containing cobalt ions. Making use of these data, the behaviour of the anisotropy constants K1 and K2 and of the spin reorientation transitions occurring in Co2-Z have been analysed.

Magnetic properties of the nearly two‐dimensional ferromagnets [C6H5(CH2)nNH3]2CuCl4 with n=1,2,3

Abstract: Magnetic susceptibility and nuclear magnetic resonance of Cu and Cl nuclei have been studied in monocrystals of [C6H5(CH2)nNH3]2CuCl4 with n=1,2,3 below 4.2 K. These compounds are two‐dimensional ferromagnets with a dominant XY‐type anisotropy. For the compound with n=1, the Ising anisotropy is extremely small. The NMR measurements of the temperature and field dependence of the magnetization are consistent with a two‐dimensional spin‐wave model and allowed us to determine the value of the intralayer exchange integral.