Magnetic hardening mechanism study in FePt thin films

${\mathrm{Fe}}_{\text{100−x}}{\mathrm{Pt}}_x$ alloy thin films with $\text{x=25–67\hspace{0.05em}}\mathrm{at.}\mathrm{ \%}$ 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 ${\mathrm{Fe}}_{\text{100−x}}{\mathrm{Pt}}_x$ alloy films were found with $\text{x=50\hspace{0.05em}}\mathrm{at.}\mathrm{\%,}$ annealed at 600 °C for 30 min and cooled by ice water quenching. Our experimental data suggests that the magnetic hardening in ${\mathrm{Fe}}_{\text{100−x}}{\mathrm{Pt}}_x$ alloy thin films is mainly due to the fct ${\gamma }_1-\mathrm{FePt}$ 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.