Compositionally modulated Gd-Co amorphous films by bias sputtering

The new sputtering technique was developed in which film deposition and ion bombardments were performed alternately and independently. By the technique, amorphous Gd-Co films were prepared with various thickness of the periodically deposited layers (t
d
). It was confirmed that ion bombardments by applying the bias of
-100 \sim-200
V change the composition within only about two atomic layers near the surface. The films with the compositional modulation of amplitude of a few at.% were synthesized in the range of t
d
larger than about 0.6 nm. A large anisotropy perpendicular to the film plane appeared abruptly at t
d
larger than 2.0 nm and the anisotropy decreased as t
d
increased. The results obtained may be interpreted qualitatively by the improved pair-ordering model.