New method to improve the structure and magneto-optical properties of bismuth garnet films

A new method to improve the structure and the magnetic-optical (MO) properties of sputtered bismuth garnet films for MO storage has been studied. The method employs high temperature ramp-up rate recurrent annealing as well as quenching in air environment. It results in small grain size (43.0 nm to approximately 30.0 nm), smooth surface, and less bubbles in the garnet film than those with conventional annealing. We discovered that the sample with more recurrent annealing only appeared in garnet phase, and its counterpart with fewer recurrent annealing appeared in garnet phase as well as DyFeO3 phase. Meanwhile the Farady angle and the coercivity increase with the recurrent number due to the increase of volume transitional rate of crystal phase in the film. Using this new method, garnet film has been successfully crystallized with a grain size of about 30.0 nm with excellent magnetic and MO properties.