Domain Structure of Hexagonal Ferrimagnetic Oxides with High Anisotropy Field

Abstract

The changes in domain structure as a function of the thickness L of the single crystals of the SrO·(6−x)Fe₂O₃·xAl₂O₃ compositional series were investigated. On the strontium ferrite single crystals, the same four models of Bitter patterns as in the case of magnetoplumbite and barium ferrite were observed. For the other compositions the limits of appearance of these four models shift towards higher values of the thickness as x increases as a result of the increased anisotropy field/saturation magnetization ratio. The thickness dependence of the domain width D changes from a D∼L^⅔ dependence to a D∼L^½ one for x≥1.8. In the case of crystals with x=2, the Bloch walls are parallel to the hexagonal axis everywhere. The finite dimensions of the samples may considerably influence the domain structure, which makes it possible for structures with two or even one domain only to be obtained, regarding relatively large samples.