Effect of bias sputtering on magnetic properties and structure of compositionally modulated Tb32Fe68 films

Amorphous Tb₃₂Fe₆₈ compositionally modulated films were prepared in a multitarget RF diode sputtering system. Independent control of the RF voltage ratios of both the Tb and the Fe target allowed the composition of the film to be held constant as the substrate bias was changed. Cross-sectional transmission electron microscopy showed that small-scale atomic clusters were aligned in layers. Bias sputtering appeared to enhance the magnetic and magnetooptical properties and modified the film structure from a columnar void to a dense, featureless morphology. The surface magnetic properties and magnetooptical responses of the unbiased films were dominated by selective oxidation of Tb. Films deposited with 70-V bias, however, exhibited stable magnetic properties and uniform magnetooptical responses throughout the film thickness