Annealing and substrate bias effects on perpendicular magnetic anisotropy in GdFe and TbFe sputtered films.

GdFe and TbFe films sputtered with substrate bias voltage (VB) have been annealed both in air and in vacuum at temperatures up to 300°C In the case of annealing in air the oxidation occurs at the film surface and forms an oxidized layer that has in-plane magnetization,and therefore, the perpendicular anisotropy (Ku) decreases. Crystallographic structure of the films changes from the amorphous state into crystal-like one with increasing VB. The amorphous films sputtered with low VB oxidize more readily than the crystal-like films. Consequently the films sputtered with low VB show a larger decrease in Ku than those with high VB. Annealing in vacuum does not seem to change the film properties.