EFFECTS OF RAPID RECURRENT ANNEALING ON STRUCTURE AND MAGNETOOPTICAL PROPERTIES OF GARNET-FILMS

A new method to improve the morphology and the microstructure of sputtered bismuth-substituted garnet films for optical storage is discussed. The method employs a high ramp up rate and recurrent annealing as well as quenching in an air environment, which results in smaller grain size, smoother surface, and less void volume in the garnet films than that from a conventional oven annealing. We have discovered that samples prepared with a more recurrent annealing only appeared as a single garnet phase, and the samples with a less recurrent annealing appeared as a garnet phase as well as DyFeO3 phase. We observed the microstructure of the annealed films with scanning electron microscopy (SEM). By applying the new method, the as-deposited films had been successfully crystallized to the (BiDy)3(FeGa)5O12 garnet phase with the grain size of about 300-400 angstrom. They exhibited excellent magneto-optical properties with a high coercive force about 1300 Oe and an effective Kerr angle of 1.5-degrees. The crystallization process of as-deposited amorphous films as well as the structure, composition, and magnetic and magneto-optical properties of the crystallized garnet films were examined.