Surface and bulk magnetic anisotropy in amorphous TbFe/SiN trilayered films

Magnetic perpendicular anisotropy constants of RF-sputtered amorphous TbFe thin films are measured by VSM and magnetooptic techniques. Anisotropy depends heavily on film thickness. It is found that the spontaneous magnetization changes with thickness in the same fashion as in the presence of a very thin (1 nm) highly magnetized interface layer. Anisotropy measured from the top and bottom film surfaces reveals a very different dependence on the deposition parameters. Because the magnetization reversal is incoherent due to the different anisotropy fields in the surface layers and in the bulk, it is necessary to account for the reveal mechanism to evaluate the true value of intrinsic anisotropy of the amorphous alloy