Growth-induced uniaxial anisotropy of bismuth-substituted iron-garnet films

The temperature dependence of the growth-induced uniaxial anisotropy constant Kgu of epitaxially grown bismuth-substituted garnet films of composition R3−xBixFe5O12 with R=Y, Lu has been measured in the temperature range 4.2 K≤T≤TC. Films with (100), (110), (112), and (111) orientation have ben investigated and exhibit a very different temperature variation of Kgu. The experimental data are compared with theoretical results based on a recently reported single-ion theory applying to bismuth-induced uniaxial anisotropies. Kgu is calculated in terms of the actual sublattice magnetizations inferred from the fit of the molecular field theory to the measured saturation magnetization.