Showing papers on "Saturation (magnetic) published in 1970"

Magnetic Properties of some Cubic Rare‐Earth‐Iron Compounds of the Type RFe2 and RxY1−xFe2

Abstract: Magnetic measurements in fields up to 30 kOe and for temperatures between 4.2° and 1000°K have been performed for cubic Laves phase compounds RFe2 (R=Gd, Tb, Dy, Ho, Er, and Y) and RxY1−xFe2 (R=Gd, Tb, and Er). The Curie temperatures and saturation moments at 4.2°K are given. A compensation in the temperature dependence of the magnetization is only observed for the various compounds in a certain range of x values. Conditions for the occurrence of a compensation point are derived. For the compounds RxY1−xFe2 the iron moment remains constant for 0≤x≤0.8. Above x=0.8 the iron moment increases strongly. The variation of the Fe moments with x is discussed in terms of a nonlocalized moment associated with the iron ions. The moments shown by Er and Tb in ErFe2 and TbFe2 are both 8.3 μB. For most of the compounds RFe2 the lattice constants are given.

Observation of Dynamic Domain Size Variation in a Silicon‐Iron Alloy

Abstract: It was recently noted that the dynamic domain structure in a ferromagnetic material may differ markedly from that observed under static conditions. In this investigation the dynamic size of magnetic domains in a rectangular single‐crystal specimen of an iron‐3% silicon alloy (2.5 cm×3.3 cm×0.22 mm with a (001) [100] orientation) was measured using the Kerr magneto‐optic effect together with high‐speed cinematography. Under dynamic conditions of a 100 Hz sinusoidal induction of saturation amplitude, the average domain width was reduced from the average static width of 2½ times the sheet thickness to about ½ this value. The finer dynamic domain structure could be ``frozen in'' by turning off the applied field during the middle of the magnetization cycle, but the original coarser structure always returned following an ac demagnetization. Measurements in the frequency range 20–100 Hz showed that above a threshold frequency domain width decreased with frequency as (f)−1/2. With a varying amplitude of induction...

Photoelectron Spin Polarization and Ferromagnetism of Crystalline and Amorphous Nickel

Abstract: We observe electron spin polarization in photoemission from nickel, undetected in earlier experimental investigations. The saturation electron spin polarization for films prepared on hot substrates is higher than for films on cold substrates and the preferential direction of the magnetic moment is parallel to the magnetization even for electrons excited from energy states near the Fermi level.

Helical Spin Arrangement in Cubic FeGe

Abstract: The magnetic properties of single crystals of the cubic B20 modification of the metallic compound FeGe have been investigated by means of a vibrating-sample magnetometer and a torsion balance. Transition to an ordered spin structure occurs at 280 K. Magnetization curves below this temperature shown an almost linear field dependence for the [100], [111] directions with a field of about 2 kOe required for saturation at low temperatures, indicating a small magnetocrystalline energy compared to the exchange energy. The saturation moment as extrapolated to zero Kelvin corresponds to 1.0μB. A model with the spins forming a helical screw propagating in the [111] direction at zero field is proposed to explain the observed magnetic properties.

Process for magnetic separation

Abstract: Process for separating colloidal and sub-colloidal ceramic magnetic components and paramagnetic components from a slurry (or other carrier) by passing the slurry through a column containing a magnetic material, as a magnetic grade stainless steel wool. The steel wool is subjected to a d-c magnetic field sufficient in magnitude to effect magnetization to saturation and above and provides a large number of regions of very high magnetic field and magnetic field gradient along the paths of travel of the slurry to attract and retain the magnetic components. It has been found that in order to provide removal of such components on an industrial scale at the high throughput rates required, a background field in the wool of at least about 12,000 gauss is required to overcome the forces of turbulence or the like in the slurry.

Saturation of infrared absorption in SF 6

Abstract: An analysis of the saturable absorption of SF 6 at 10.59 μ is presented. A model for the absorber is developed and experiments have been performed to determine the value of the saturation parameter. It is shown that at pressures above 0.1 torr, the saturation parameter varies linearly with the pressure and is governed by the relaxation time of the lowest level ν 6 . Effects of temperature on the absorption are discussed.

New Type Metamagnetism in Co(SxSe1-x)2: Exchange-Compensated Paramagnetism

Abstract: The magnetic phase diagram of Co(S x Se 1- x ) 2 , the solid solution between ferromagnetic CoS 2 and antiferromagnetic CoSe 2 , has been given by neutron diffraction experiment, where the paramagnetism at absolute zero was found in the range 0.5< x <0.88. This paramagnetic state is named “exchange-compensated paramagnetism”. A new type metamagnetism has been found in this paramagnetic state at x =0.86. This behavior had been already predicted theoretically by M. Hattori, K. Adachi and H. Nakano in J. Phys. Soc. Japan 26 (1969) 642. The metamagnetic properties have been measured under a strong magnetic field up to 75 kOe and in the temperature range 4.2°K to 800°K. The metamagnetism shows the hysteresis without remanence below 34°K and the saturation moment agrees with that of CoS 2 . The obtained results have been analyzed from the thermostatistical standpoint with an analogy of the condensation of imperfect gas and the critical indices have been determined. The origin of the exchange-compensated paramag...

Mössbauer study of hyperfine interactions in divalent europium compounds at ultra low temperatures

Abstract: The Mossbauer resonance of the 21.6 keV transition in151Eu has been used to investigate the magnetic properties of divalent ionic europium compounds at ultra low temperatures. The specimens were cooled by a3He/4He dilution refrigerator to a minimum temperature of 0.04 K. The following magnetic ordering temperatures were found: EuSO4, 0.43 K; EuF2, 1.0 K; EuCO3, 1.05 K; EuCl2, 1.1 K; EuC2O4, 1.9 K; EuC2O4 · H2O, 2.8 K. The absolute value of the saturation hyperfine fieldHeff of all these compounds is between 315 and 337 kOe. The temperature dependence ofHeff deviates somewhat from aS=7/2 Brillouin function. This behavior is probably due to relaxation phenomena.

Magnetic Properties of TbIn3, TbPt3 and HoIn3

Abstract: Neutron‐diffraction measurements made on powder samples of TbIn3, TbPt3, and HoIn3 show that all of these compounds exhibit antiferromagnetism below Neel temperatures of 37 ± 1°K, 20.5 ± 0.5°K, and 11.5 ± 0.5°K, respectively. The magnetic reflections from TbPt3 can be indexed on a doubled chemical cell of cubic symmetry. A possible magnetic model consists of an arrangement where the Tb moments are aligned in opposite directions in adjacent (111) magnetic planes. The magnetic reflections from TbIn3 and HoIn3 can be indexed on a doubled chemical cell of tetragonal symmetry. An appropriate magnetic arrangement is one in which the rare‐earth moments are aligned in opposite directions in adjacent (110) magnetic planes. For TbIn3 the moment direction makes an angle of 10 ± 5° with the unique or c axis of the magnetic cell; for HoIn3 the corresponding moment direction is 58 ± 5°. The saturation ordered moment on the rare‐earth atom sites in all three compounds is approximately 10% less than the calculated or expected values. The magnetic structures are compared with predictions of the indirect exchange theory.

High coercive force films of cobalt-nickel with additions of group VA and VIB elements

Abstract: This paper describes some of the structure-property relations for Co and CoNi films containing Group VIB additions, i.e., chromium, molybdenum, and tungsten and Group VA additions, i.e., phosphorus, arsenic, antimony, and bismuth. All films were prepared by electrodeposition. The magnetic properties and metallurgical structure of the films with tungsten cover the same range of parameters as produced with the phosphorus films. The quantity of the elements required to achieve the maximum in coercive force increases substantially in the sequence P, As, Sb, and Bi; and in the sequence W, Mo, and Cr. The saturation moment and coercive force both decrease with increase of the concentration of added element required to attain the maximum coercive force. The quantity of the elements required is believed to be related to the ability of the electrolyte to produce a refinement of the grain size of the deposit, and the ability of the element added to segregate to the grain boundaries. The saturation moments of Co with W and P agree with the results expected for solid solutions except at high concentrations. The structure sensitive magnetic properties obtained with CoNiW films are qualitatively interpreted in the same way as for the CoNiP films, i.e., on the basis of a strongly interacting array of fine particles. The alloys containing Cr, Mo, or W possess improved resistance to aging at elevated temperatures and in corrosive environments.

Dielectric behaviour of stiff polymers in solution when subjected to high voltage gradients

Abstract: We report measurements of dielectric saturation on solutions of poly-γ-benzyl-L-glutamate and ethyl cellulose. Saturation effects of considerable magnitude were observed, particularly with the former polymer. Measurements were made by the simultaneous application of high static and low alternating fields to these macromolecules in solution. When poly-γ-benzyl-L-glutamate was the solute, this technique has enabled us to observe, for the first time field-induced changes in the dielectric relaxation times. The influence of such variables as field strength, concentration, average molecular weight and average dipole moment on both the dielectric saturation and critical frequency shifts are reported. We present a unified theoretical approach to dielectric saturation which embraces some of the previous theories, and on the basis of this approach discuss the observed results. Complete agreement between experimental observations and theoretical predictions for the poly-γ-benzyl-L-glutamate system is only possible if the calculated dipole moment of the macromolecule under high field is considerably larger than its measured low-field value. Some possible implications of this conclusion are considered.

A study of rhodium iron and molybdenum iron alloys using the Mossbauer effect

Abstract: The mossbauer spectra of 57Fe in rhodium iron (1-25%) and some molybdenum iron alloys have been obtained at 300 K, 4.2 K and 1.4 K, and the magnetic ordering temperatures have been observed as a function of iron concentration. The 300 K and the 4.2 K results show that the iron impurities are well screened, and from the low temperature results the saturation hyperfine fields for iron in rhodium (176+or-3 kOe) and iron in molybdenum (116+or-5 kOe) have been obtained. The behaviour of the spectra of dilute samples in an applied field of 29 kOe at 4.2 K and 1.4 K have been interpreted using these saturation hyperfine fields to obtain distribution curves of effective moment. Effects attributable to interactions between moments, and to the Kondo effect have been observed. The plot of ordering temperature against concentration for iron in rhodium appears not to pass through the origin, presumably due to the compensation of the magnetic moment.

Reversible Susceptibility of an Assembly of Single‐Domain Particles and Their Magnetic Anisotropy

Abstract: The anisotropy properties of fine magnetic particles can be determined by measurements of the initial reversible susceptibility. The effects of magnetostatic interactions on the reversible magnetization in low magnetic fields near zero and saturation remanence are treated in detail with regard to packing fraction p and particle axes orientations. It is shown among other results that for any symmetrical orientation distribution, the reciprocal initial reversible susceptibility decreases linearly with p. Thus, by extrapolation to p=0 (the susceptibility without interaction effects) the effective anisotropy constant of the particles can be obtained. From the temperature dependence of the susceptibility it is conjectured that γ‐Fe2O3 has 〈110〉 easy directions of crystalline anisotropy. The corresponding anisotropy field as a function of temperature between 77° and 400°K was thus determined from susceptibility measurements. For CrO2 particles the anisotropy data are already known and are shown to be in good ag...

Surface‐Roughness‐Induced Demagnetizing Fields in Thin Films and Their Influence Upon the Approach to Saturation

Abstract: The magnetic field generated by the magnetization has been calculated for films with rough surfaces. At large magnetic fieldstrengths the film is uniformly magnetized. Simple formulas for the demagnetizing factors are given, which are applicable provided that the inclination of the local film surface relative to the mean surface is not too large. A rough estimate of the demagnetizing factor for a direction in the plane of the film is given by π〈p2〉/λd. Here 〈p2〉 is the mean‐square (linear) deviation of the actual film surface from the mean surface, λ the predominant wavelength of the surface roughness, and d the film thickness. A relatively small surface roughness, if distributed anisotropically, is sufficient to induce a significant uniaxial magnetic anisotropy. If the magnetic fieldstrength is only moderately high, the surface roughness gives rise to misalignment of the magnetization vector near the surface relative to the mean magnetization vector. The effect of this misalignment upon the average magne...

Magneto‐Optic Properties of CrTe Films Prepared by Sequential Evaporation

Abstract: A study was made of the magnetic properties of CrTe films relevant to magneto‐optic memory applications. Polar‐Faraday rotation measurements in the visible and near infrared were taken on CrTe films prepared by sequential deposition of layers of Cr–Te–Cr on cleaved mica substrates. The Faraday rotation and absorption decreased respectively from 0.5×105°/cm at 0.55 μm to 0.4×105°/cm at 1 μm and 2×105 cm−1 at 0.5 μm to 0.6×105 cm−1 at 2.5 μm. The rotation and coercive field decreased with the magnetization and vanished at the Curie temperature (∼70°C). The polar remanence ratio was 0.2. An in‐plane magnetization curve had a remanence ratio of 0.8, a saturation induction (4πMs) of 1015 G and a coercive field of 117 Oe. The measurements indicate significant advantages for CrTe films in memory applications if the epitaxial growth can be improved resulting in higher polar remanence.

The magnetic properties of dilute palladium-iron alloys

Abstract: The magnetizations of several PdFe alloys containing 0.05-0.15 at.% iron have been measured as functions of field (0.06-18.5 kG) and temperature (1.2-4.2 degrees K). The results are interpreted by assuming that the magnetizations for each alloy may be separated into contributions from the palladium matrix and 'giant' moments associated with the iron atoms. The latter show paramagnetic behaviour which can be represented by Brillouin functions with arguments incorporating an internal field proportional to the magnetization. The saturation magnetizations indicate that a moment of 9 Bohr magnetons is associated with each iron atom and the form of the Brillouin functions suggest that complexes of iron atoms are formed carrying considerably larger magnetic moments. The 0.15 at.% alloy was found to be ferromagnetic with a Curie temperature of 2.1+or-0.05 degrees K.

Magnetic Properties of the Intermetallic Compound with the Cu 3 Au-Type Structure in Cobalt-Titanium Alloy System

Abstract: X-ray and magnetic studies have been made on the intermetallic compound Co 3+ x Ti 1- x . X-ray study indicates that Co 3+ x Ti 1- x with the Cu 3 Au-type structure has the phase field ranging from about 20.5 to 25.0 at. % Ti( x =0.180∼0) below 1,000°C. According to magnetic measurements, Co 3 Ti( x =0) is a paramagnetic substance with a practically temperature independent magnetic susceptibility, whereas Co 3+ x Ti 1- x ( x >0) is ferromagnetic with Curie points lower than 80°K and saturation magnetizations less than 20.8 emu/g.

Transport properties of a memory-type chalcogenide glass☆

Abstract: Transport measurements have been performed on the conducting state of a memory-type chalcogenide glass, of composition Te81Ge15As4. DC resistivity was measured from 4°K to 300°K and indicates no carrier freeze-out occurs down to 4°K. The resistance ratio, ϱ(300°K)/ϱ(4°K), was found to be 2.5. AC conductivity measurements at room temperature showed only an 18% increase in σ(ω) up to 150 khz. Hall effect experiments at 100 Hz show no dependence of carrier concentration on temperature from 77°K to 300°K, and indicate a room temperature mobility of 85 cm2/V-sec. The sign of the Hall constant implies that the carriers are holes. Resistance was measured as a function of magnetic field from 0 to 140 kOe, at 1.6°K. The magnetoresistance was positive and proportional to H2 at low fields, with saturation beginning to set in above about 80 kOe. The results of these studies, taken in conjunction with the X-ray and NMR data, can be used to suggest a plausible model for memory behavior in chalcogenide glasses.

Permanent magnet system for a loudspeaker

Abstract: A permanent magnet system is made for a loudspeaker consisting of a rod or ring-formed axial magnetic magnets and soft iron parts. A portion of the ferromagnetic circuit in the system is made from a mechanically machinable, dense alloyed ferritic steel with higher electrical and lower magnetic resistance than soft iron and a saturation magnetism at least equal to the air gap induction required by the system.

Magnetothermodynamics of α‐MnCl2·4H2O. III. Heat Capacity, Entropy, Magnetic Moment, from 0.3 to 4.2°K with Fields to 90 kG along the [100] Crystal Axis

Abstract: The heat capacity and magnetic moment of a 3.934 cm diameter spherical single crystal of α‐MnCl2·4H2O have been measured with stabilized solenoid fields of 0, 1, 5, 10, 14, 22, 25, 40, 65, and 90 kG, along the [100] crystal axis. The magnetic saturation value, 27 999 G·cm3 mole−1, obtained at both 65 and 90 kG, and 0.46°K, indicates that the temperature independent susceptibility is zero and the saturation moment of the temperature‐dependent system is 27 999 G·cm3 mole−1, equivalent to g[100] = 2.005. At 90 kG the nuclear spins contributed a heat capacity term of 5.6 × 10−3 T−2gibbs mole−1. The amount of enthalpy required to remove quanta of angular momentum from the saturated condition at 90 kG was found to be 20.2 cal mole−1. This is less than gβH = 24.09 cal mole−1, the magnetic work, by 3.9 cal mole−1. This difference is the amount of stored internal energy contributed by the saturated condition to this limiting process, and is consistent with antiferromagnetic interactions. Extrapolation of the magne...

Effect of Longitudinal Magnetic Field on Acoustoelectric Amplification in n‐InSb

Abstract: Appreciable enhancement of the acoustoelectric gain by longitudinal magnetic fields is observed in the classical regime (ℏωc

Saturation Magnetization and Perpendicular Anisotropy of Nickel Films

Abstract: Polycrystalline nickel films between 26 and 296 A in thickness were obtained by evaporation at normal incidence from tungsten filaments onto microscope‐slide glass substrates maintained at 75°C, at pressures between 6×10−10 and 12×10−10 Torr. In the same vacuum the substrates with their films were arranged to be parts of an automated torsion magnetometer in which the sample rotated about an axis in its own plane perpendicular to the magnetic field. Measurements were made of the torque as a function of the magnetic field required to maintain the plane of the sample at various fixed angles θ0 ranging from 3° to 84° with respect to the magnetic field, at sample temperatures of about 300°, 77°, and 4.2°K. The torque data were analyzed by a new method which permits detailed investigation of models for the magnetization. It is shown that for a single‐domain model with an out‐of‐plane uniaxial anisotropy, the saturation magnetization MS and the total anisotropy field S can be calculated from the magnitude and sl...

Magnetization and remagnetization of anisotrophic magnetically hard ferrites

Abstract: Magnetization curves and hysteresis loops of anisotropic hard ferrites were analyzed after the specimens had been demagnetized either thermally or by an ac field parallel or perpendicular to the preferred axis (PA) between -196°C and Curie temperature, or by a dc field. Each demagnetization yields a specific magnetization curve; below saturation fields, asymmetrically positioned and noncentrosymmetrical loops develop, except after ac demagnetization at 20°C (=measuring temperature) parallel to PA. This is due to domain configurations differently arranged and of different stability. The asymmetry is caused by "frozen" unstable configurations, which undergo an irreversible change due to the action of the field. Therefore, with reversed field not all of the previous possibilities for remagnetization are still available.