Kerr effect of ordered and disordered Fe1-xPtx(001) alloy films

The (001) oriented Fe1-xPtx alloy films have been grown on Pt seeding layer s on MgO (001) substrates by MBE. At growth temperature of 500 degreesC, ra ther ordered structures were formed for FePt, FePt2, and FePt3 films, which exhibit large perpendicular magnetic anisotropy and Kerr rotations. In con trast, Fe2Pt and Fe3Pt films were poorly ordered and did not display perpen dicular magnetization for similar growth conditions. The optimal growth tem perature of the FePt (x = 0.5) alloys occurs at about 500 degreesC, and the surface order-disorder transition occurs above 650 degreesC. We demonstrat e that chemical ordering is important for perpendicular magnetic anisotropy and Kerr effects for Fe1-xPtx alloy films, which in turn depend strongly o n the alloy composition and growth temperature.