Bismuth- and aluminium-substituted YIG single-crystal films on modified gadolinium gallium garnet single-crystal substrates

Bismuth- and aluminum-substituted yttrium iron garnet single-crystal films with the nominal composition of Y1.5Bi1.5Fe4.2Al0.8O12 (Bi,Al:YIG) were prepared by spin coating a gel on the (111) plane of (GdCa)3(GaMgZn)5O12 single-crystal garnet plates. Crystallinity of the films varies with temperature and time of heat treatment in air after gel coating. Single-crystal films were obtained at Ta=650 °C for 4 h. The onset temperature for crystal growth is about 560 °C, which is about 400 °C lower than that of liquid-phase epitaxy. The crystal-growth process of single-crystal Bi,Al:YIG films was examined by measuring crystallographic structures as well as the magneto-optical Faraday effect. The internal stress giving rise to magnetic uniaxial anisotropy to align the magnetization normal to the film plane plays an important role for completion of single-crystal growth throughout the film.