Stability of magnetic and magneto-optic properties in TbCo sputtered films

Stability of magnetic and magnetooptic properties in TbCo sputtered films is investigated in air at room temperature. Various kinds of substrate bias voltage is applied during sputtering. Saturation magnetization changes fastest in the film with -200 V bias due to preferential oxidation of Tb. The rate limiting step of this change is diffusion. Faraday rotation angle for saturation magnetization does not change with time, but Kerr rotation angle increases with oxidation. Change in atomic density of the TbCo film with substrate bias is investigated by Rutherford backscattering experiment. Stability of the film is related to the film density.