Magnetic hardening mechanism study in FePt thin films

Fe100−xPtx alloy thin films with x=25–67 at. % were prepared by dc magnetron sputtering on naturally oxidized Si substrates. Effects of film composition, annealing temperature (300–650 °C), annealing time (5–120 min), and cooling rate (furnace cooling or ice water quench cooling) on the magnetic properties were investigated. Optimum conditions for saturation magnetization and coercivity of the Fe100−xPtx alloy films were found with x=50 at.%, annealed at 600 °C for 30 min and cooled by ice water quenching. Our experimental data suggests that the magnetic hardening in Fe100−xPtx alloy thin films is mainly due to the fct γ1-FePt phase and the domain wall pinning effect. The domain nucleation mechanism is dominated in samples with furnace cooling; the domain wall pinning mechanism dominates in samples cooled with ice water quenching.