E. A. Stepanova

Effect of electrolytic oxidation and hydrogenation on the magnetization distribution and magnetic properties of ribbons of amorphous soft magnetic iron-based alloys

The effect of electrolytic oxidation and hydrogenation on the magnetization distribution and magnetic properties of ribbons of amorphous soft magnetic iron-based alloys has been investigated on the example of the Fe77Ni1Si9B13 and Fe81B13Si4C2 alloys. The results of the investigation showed that hydrogenation and oxidation of the surface of the ribbon lead to changes in the magnetic properties, which agree with changes in its magnetic state. A decrease in the volume of domains with orthogonal magnetization observed upon oxidation is caused by the large effective diameter of oxygen atoms inducing a higher level of planar tensile stresses upon incorporation into the ribbon surface. A reduction (observed in both cases) in the volume fraction of domains with a planar magnetization oriented along the ribbon axis is connected with the appearance of pseudo-uniaxial tension in the plane of the ribbon across its axis, since the concentration of atoms incorporated into the surface is enchanced in this direction. The interaction of the surface of the ribbon at room temperature with vapor leads to identical changes in the magnetic characteristics and redistribution of magnetization in its plane.

Magnetic anisotropy of Tb-Co amorphous films

A systematic investigation of the magnetic properties of Tb-Co amorphous films prepared using radio-frequency ion sputtering in a uniform magnetic field has been carried out. The main regularities of the change in the magnetic anisotropy parameters as a function of the composition (8–43 at % Tb), measurement temperature (5–350 K), and annealing temperature (up to 200°C) have been established. It has been shown that their interpretation can be performed within the framework of the model that takes into account the fluctuating local magnetic anisotropy of the terbium ions, columnar microstructure, and anisotropy of elastic stresses.

Magnetization reversal of Tb-Co/Fe19Ni81 films with a unidirectional anisotropy

Conditions have been found for the realization of induced in-plane uniaxial anisotropy of the amorphous Tb31Co69 films and of unidirectional anisotropy in the Permalloy layers in the composite two-layered Tb31Co69/Fe19Ni81 films. The mechanisms of magnetization reversal in such film structures have been studied in a temperature range of 5–300 K. It has been found that a decrease in temperature leads to a transformation of hysteresis loops, a significant increase in the field of unidirectional anisotropy, and a nonmonotonic change in the coercive force of the Permalloy layer. The regularities found are interpreted taking into account the variation in the properties of the amorphous layer Tb31Co69 with temperature under the assumption on a temperature-induced change in the localization of the interlayer magnetic boundary, which is formed upon a layer-by-layer magnetization reversal of the film structure.

Magnetic losses and their components in rapidly quenched magnetically soft Fe-based alloys

Studying the dependence of the specific magnetic losses on the frequency and induction of magnetically soft electricotechnical materials has shown the inefficiency of the conventional method of separation of the specific magnetic losses into components. For example, according to the conventional technique, one can find that there are ranges of frequencies where the total magnetic losses are smaller than the hysteresis component; besides, at comparatively high inductions it is possible to reduce the dynamic component of magnetic losses to virtually zero. The investigation carried out allowed us to suggest a new method of separation of magnetic losses into components taking into account a frequency dependence of the hysteresis losses. The results of the analysis of the magnetic-loss components in the context of the suggested method for ribbons of rapidly quenched soft magnetic alloys allowed us to eliminate the contradictions revealed. Besides, they have shown that the formation of a low-frequency resonance peak of absorption in the region of displacement of 180° domain walls is mainly caused by the frequency-dependent component of the hysteresis losses, whereas in the interval of inductions where the processes of displacement of 90° domain walls are active, this formation is caused by both the dynamic and frequency-dependent hysteresis components of magnetic losses.