Rapid ordering of Zr-doped FePt alloy films

The magnetic properties and microstructural evolution of Zr-doped FePt alloy films prepared by dc-magnetron sputtering were investigated. Compared to an undoped ${\mathrm{Fe}}_{\mathrm{59}}{\mathrm{Pt}}_{\mathrm{41}}$ binary film, Zr-doped FePt alloy films showed accelerated ordering transformation kinetics accompanying smaller grains: we were able to fabricate a Zr-doped FePt film [e.g., $({\mathrm{Fe}}_{\mathrm{59}}{\mathrm{Pt}}_{\mathrm{41}}{\mathrm{)}}_{\mathrm{97}}{\mathrm{Zr}}_{\mathrm{3}}$ ] possessing very fine grain size (5 nm in average) and high coercivity (7.3 kOe) within 10 min annealing at 500 °C. It is thought that the point defects and lattice strain introduced by Zr-doping activated the nucleation rate of the ordered phase. In particular, for Zr-doped FePt films containing less than 45 at. % Pt, the ordered ${\mathrm{L1}}_{\mathrm{0}}$ phase was decomposed into a disordered phase after excessive annealing due to the formation of a Pt–Zr compound, most likely ${\mathrm{Pt}}_{\mathrm{3}}\mathrm{Zr},$ that reduces the effective Pt content in the ordered phase.