Grain size control in FePt thin films by Ar-ion etched Pt seed layers

A method to control the grain size of FePt L1(o) thin films by means of an Ar-ion etched Pt seed is presented. The etching results in structures on th e surface of the Pt seed layer, whose feature size can be controlled by etc hing time and ion energy. The grain size for 25 nm thick FePt films grown a t 450 degreesC can be reduced from about 29 nm on as-grown seed layers to 1 5 nm with a reduced grain size dispersion on etched seed layers. The coerci vity of these films. changes from 2 kOe to 11 kOe, respectively. To reduce the coercivity to a range suitable for writing with currently available rec ording heads, i.e., <4 kOe, up to 15 at.% Cr were added to the FePt alloy.