Structure and magnetic properties of magnetron-sputtered FePt/Au superlattice films

Abstract

Using dc magnetron sputtering, FePt/Au multilayer films were prepared, and the effects of Au thickness and annealing temperature on structure and magnetic properties of the FePt/Au films were investigated. The as-deposited FePt/Au multilayer films with a thicker Au layer show a superlattice structure. The interatomic layer spacing d(2 2 0) in face centered cubic (fcc) FePt lattice increases with increase in Au thickness. Accordingly, the strain energy stored in the fcc FePt lattice increases. After annealing at 300 °C, ordered FePt films were obtained, and the in-plane and out-of-plane coercivities of the films were found to increase with the increase in the Au layer thickness. When the Au layer thickness is 3.5 nm, the in-plane and out-of-plane coercivities of the films can reach 2.08 kOe and 1.56 kOe, respectively. The strain energy stored in fcc FePt lattice is responsible for the lower temperature ordering of FePt phase. For the films annealed at high temperature, the thicker Au layer in the films restrained the ordering of the FePt phase, which leads to the decrease in the coercivities of the films with increasing Au thickness.