Microstructure of bismuth doped yttrium iron garnets thin films

Complex structural studies of nanosized bismuth-doped yttrium iron garnet (BYIG) films were performed using X-ray diagnostics, scanning/transmission electron microscopy, and energy-dispersive X-ray microanalysis. The crystal structure of the film-substrate interface, the near-surface layers together with change in interplanar distances along the film thickness were determined. The features of the film microstructure were revealed: the presence of pores, the absence of misfit dislocations at the interface, the formation of maghemite (γ-Fe2O3) particles on the film surface and a decrease in the Bi content towards the film surface. Assumptions were made about the change in the Bi content depending on the film thickness, which can serve as an explanation for the mechanism of decreasing the magnitude of magneto-optical effects in these films with decreasing thickness.