Microstructure and coercivity of granular nanocomposite FePt-Ag multilayer films

The face-centered-tetragonal granular L1₀FePt nanoparticles with large in-plane coercivity (Hc_{//) of about 3923 Oe can be achieved by an Ag-capped layer of 5-nm thickness deposited onto the FePt magnetic layer, with thickness of 20 nm, after annealing at 400°C for 30 min. The perpendicular coercivity (Hc⊥) of the films is increased by increasing the annealing temperature (Ts), and the Hc⊥ value is about equal to the Hc// value when the annealing temperature is increased to 600°C. TEM-energy disperse spectrum analysis reveals that the Ag mainly distributed at the grain boundary of FePt and results in the isolation of the FePt grains as well as the increase of the grain boundary energy, which will enhance coercivity and change the preferred orientation of the FePt film.}