Temperature dependence of the first constant for the crystallographic magnetic anisotropy for polycrystalline lithium-aluminum ferrites

Measurements by approach to saturation are reported for specimens of composition witha = 0; 0. 2; 0. 4; 0. 5; 0. 6, over the range 170 ° to 530 ° K. Modulated fields are used to examine the approach to saturation.     

Ferromagnetic resonance and magnetic crystallographic anisotropy of monocrystalline lithium ferrite films

The crystallographic anisotropy constant K₁ of monociystalline lithium ferrite films was measured by the methods of ferromagnetic resonance and rotational moments. The presence of uniaxial anisotropy in the plane of a film with the constant K_u 10₃ erg · cm^–3 is established experimentally. The nature of the uniaxial anisotropy is explained by the anisotropy of the stresses in the plane of the film, a formula is obtained to compute the angle of deflection of the easy magnetization axis from the crystallographic direction. An estimate is made of the difference in the stresses along the axes (_x–_z) 10¹⁰ dyne · cm^–2.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 9, pp. 86–89, September, 1973.     

Magnetic anisotropy of lithium aluminum ferrites

The temperature dependence of the first magnetic-anisotropy constant of Li_0.5Fe_2.5–xAl_xO₄ (x = 0, 0.2, 0.4) ferrites is calculated on the basis of the single-ion model with an account of biquadratic indirect exchange. The coefficients governing the splitting caused in the levels of Fe³⁺ in tetrahedral and octahedral positions by the lattice field are found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 8, pp. 7–11, August, 1969.The author thanks A. I. Perveeva for programming the computer solution for the temperature dependences of the sublattice magnetizations, and E. P. Naiden for discussion of some of these results.     

The magnetic anisotropy of manganate ferrites

The anisotropy constants K₁ for systems Mn_xFe_3–xO₄, with 1x 1·8, are calculated on the basis of the one-ion model and it is shown that the anomalous temperature dependence of the constant K₁ can be explained by the presence of Mn³⁺ ions in octahedral positions. The influence of the spin order on the magnetic anisotropy and the uniaxial anisotropy in systems Mn_xFe_3–xO₄ are discussed.     

Ferromagnetic resonance in polycrystalline ferrites with high magnetic anisotropy

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.Translated from Izvestiya VUZ. Fizika, No. 1, pp. 9–16, January, 1972.     

Structural and some magnetic properties of manganese-substituted lithium ferrites

The structural and magnetic properties of Mn-substituted lithium ferrites having the general formula Li_0.5−0.5xMn_xFe_2.5−0.5xO₄ (where x=0.0–1.0) prepared by the standard ceramic technique have been studied. Single phase cubic structure is confirmed by X-ray diffractometer. This result demonstrates that the samples are homogeneous, and the sharp peaks reveal that the samples are in crystalline form. The lattice parameter ‘a’ and average grain diameter ‘D’ increase with increasing Mn²⁺ ion substitution. The saturation magnetization and the experimental magnetic moment are found to increase with manganese up to x=0.5 and then tends to decrease for x>0.5. The increase in magnetic moment with manganese is attributed to Neel's two sublattice model according to which the magnetic moment is the vector sum of lattice magnetic moment. The decrease in magnetization for x>0.5 obeys the Yafet–Kittel (Y–K) model. The increase in Y–K angles for x≥0.5 indicates the increased favor for triangle spin arrangements on B-sites. This suggests the existence of canted spin structure in the ferrite system with higher content of Mn. Hystersis loops were measured. The initial permeability μ_i was measured as a function of temperature.     

Losses from rotational hysteresis and magnetic anisotropy in single crystals of barium and barium-cobalt hexaferrites

The rotational-hysteresis loss as a function of field has been examined for single crystals of the hexaferrites BaM and Co₂W. Curves for K₁(T) for BaM and K₃(T) for Co₂W have been recorded. The domain structure has been examined on specimens with residual magnetization. The rotational-hysteresis loss for BaM is of the type usual for ferrites, having a negative temperature coefficient below 120 °C, but above this there is an anomalous positive coefficient, which is due to diffusion of Co ions in the rotating field. The initial increase in the loss is related to the dynamics of the domain structure. Heat treatment influences the temperature dependence of the anisotropy constants and hence the rotational hysteresis loss.     

Temperature dependence of the elastic constants and Debye temperatures of NaCl and KCl single crystals

A pulsed ultrasonic method has been used to measure the temperature dependences of the elastic moduli, the constants C_ik and S_ik , the anisotropy factors, the bulk moduli, and the Poisson ratios over the temperature range 300-120 ° K for NaCl and over the range 300-80 ° K for KCl. The Debye temperatures of these compounds are calculated from the elastic constants extrapolated to 0 ° K.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 22–28, June, 1970.     

Effect of the surface crystallographic orientation and thickness of Fe-3 wt%Si single crystals on magnetic losses in rotating magnetic fields

The response of magnetic losses to rotation-induced magnetization reversal in single-crystal Fe-3 wt%Si disks is studied as a function of the disk thickness and magnetic induction. It is shown that the loss power varies nonmonotonically with disk thickness d, exhibiting a minimum at d = 0.15 mm. The crystallographic orientation of the disk surface significantly influences the amount of the losses. The variation of the losses is discussed with regard to the effect a rotating magnetic field has on the domain structure.     

Elastic constants of iron-silicon alloy single crystals

The adiabatic elastic constants of single crystals of Fe-Si alloys in the composition range from 6.3 at.% Si to 25 at.% Si have been determined by the ultrasonic pulse echo method at room temperature. The values of the elastic constants depend significantly on the silicon content, and their composition dependences are influenced by ordering.     

Temperature dependence of anisotropy in monocrystalline lithium ferrite films

A study of crystallographic and uniaxial anisotropy in monocrystalline Li-ferrite films in the temperature range 4.2–550°K is presented. The experimental results K₁(T) agree well with calculations based on the one ion model with crystalline field coefficients of a_A=–2.77 ·10^–2 cm^–1, a_B=3.34 · 10^–2 cm^–1. An experimental function K_u(T) is obtained which does not contradict the assumption that anisotropic stresses are responsible for the development of uniaxial anisotropy in Li-ferrite films.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 113–116, August, 1973.     

The determination of magnetic anisotropy constants from torque curves

The procedures by which magnetic anisotropy constants are evaluated from torque curves are examined with reference to some calculated torque curves for an ideal uniaxial crystal. The results are compared with some torque measurements on a crystal of cobalt.     

Large magnetic anisotropy in single crystal us

It is shown for ferromagnetic US that an extremely large anisotropy restrains magnetic moments to 〈111〉 easy axes, resulting in a near cos θ angular dependence of the magnetization away from the 〈111〉 axes. This is further confirmed by torque measurements, which in addition show large hysteresis effects upon rotation through the hard axes. It is illustrated through torque and magnetization measurements that a near stable domain configuration can be established by field rotation through decreasing angular amplitude around a hard 〈001〉 direction. The anisotropy constant K₁(T) is estimated by computing the small angle through which the magnetization deviates from the 〈111〉 axes when a field is applied along the [001] direction.