Bi-Substituted Garnet Films Sputtered in Ar+H2 for Magneto-Optic Memory

To investigate properties of Bi-substituted garnet film with many oxygen deficiencies, Bi, Ga:DyIG films were prepared by sputtering in Ar+H₂ gas (H₂ partial pressure 0 to 5%), and then annealed to promote crystallization. When the H₂ concentration in the sputtering gas was raised, the Bi content of the film decreased. The film sputtered in Ar+H₂ crystallized as a single garnet phase at relatively low temperatures (560°C for Bi = 1.5), even when the Bi content was low under non-stoichiometric conditions. The optical homogeneity of the film improved remarkably when the H₂ concentration was raised; optical scattering due to crystal grain boundaries was reduced below that of film sputtered in pure Ar gas. This result is related to the many defects remaining in the crystal grains even after annealing. This was confirmed by the broad linewidths observed in X-ray diffraction studies. The magnetization and Faraday rotation hysteresis of films sputtered in Ar+H₂ showed anomalies, which may have been caused by an impurity phase undetectable by X-ray diffraction measurements.