The temperature dependence of the domain structure of uniaxial single crystals with high-anisotropy field

The temperature dependence of the domain structure of single crystals of uniaxial ferrimagnetic oxides with high-anisotropy field in the SrO(
6 - x
)Fe
2
O
3
x
Al
2
O
3
compositional series, with
x = 1.8
and 2.4, was investigated. The domain configurations of thermally and/or ac field demagnetized states and the changes in dc and ac fields were observed by means of the colloid technique using a suspension in paraffine oil. The temperature dependence of the wall energy density between room temperature and the Curie point (270°C) of the compound with
x = 1.8
was computed using the temperature dependence of the saturation magnetization and the domain width for the Kittel-like domain structure. It has been found that the room temperature domain structure of the compound with
x = 2.4
depends upon the mode of demagnetization, i.e., thermally or in the ac field. The ac demagnetized states are more stable than the thermally demagnetized ones. The samples exhibit a room temperature memory of the previous magnetization, which decreases with rising temperature. This memory is completely lost after heating at 400°C. The peculiarities of the temperature dependence of the domain structure and magnetic behavior on thermal cycling are explained by considering the existence of magnetic inhomogeneities within the crystal.