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

A method to control the grain size of FePt Ll₀ thin films by means of an Ar-ion etched Pt seed is presented. The etching results in structures on the surface of the Pt seed layer, whose feature size can be controlled by etching time and ion energy. The grain size for 25 nm thick FePt films grown at 450°C can be reduced from about 29 nm on as-grown seed layers to 15 nm with a reduced grain size dispersion on etched seed layers. The coercivity of these films changes from 2 kOe to 11 kOe, respectively. To reduce the coercivity to a range suitable for writing with currently available recording heads, i.e., <4 kOe, up to 15 at.% Cr was added to the FePt alloy