Magnetic properties of sputtered Bi sub(3)Fe sub(5)O sub(12)

A series of Bi substituted yttrium iron garnet films has been grown including its end members, YIG and BiIG, by an r.f.-diode sputtering method. The low temperature magnetization of highly Bi substitute garnet is much lower than expected from the linear expansion of the lattice. The temperature dependence of the magnetization of these materials is described by a molecular field model in which some of the moment on the tetrahedral site Fe ion is assumed to be transferred to the Bi ion on the dodecahedral site. Reasonable agreement between the model and the data is obtained for BiIG. The large values of the uniaxial anisotropy energy, the crystalline anisotropy energy and the linewidths measured by FMR are complementary to this result.