Microstructural investigations of Bi doped Fe garnet thin films for magneto-optical recording

Gd1.6Bi1.4Fe3.8Ga1.2O12 garnet films for short wavelength magneto-optical recording are investigated. These films have high Faraday rotation (up to 1.3 °/μm), good corrosion resistance and good magnetic properties (Hc≳1 kOe with hysteresis loop squareness of 1) but poor noise performance. This paper shows that the noise is a result of the grain size being of the order of the recorded domain size and that the grain size and distribution are determined by the initial density of garnet nuclei. In the course of this study, it was discovered that these films contain a high density of Bi globules which precipitate out of the garnet matrix. It is believed that these globules contribute to the high coercivity of sputtered garnet films.