FePt–Si–N nano-granular thin films with improved structure and magnetic properties for high-density recording medium

FePt–Si–N films consisting of FePt nanoparticles embedded in Si–N matrix were fabricated on Si(100) substrates by dc reactive magnetron sputtering followed by vacuum annealing. The effects of film thickness, Fe/Pt atomic ratio, and Si, N additions on the structure and magnetic properties were investigated. Perpendicular orientation can be obtained in the film with small thickness. Fe content also has an important effect on the film orientation. The ordering temperature for FePt–Si–N films is 100 °C higher than that of FePt films. Both FePt and FePt–Si–N films have the highest coercivity at Fe content of 55 at%. Doping Si and N can improve the coercivity of FePt film through weakening the exchange coupling and reducing the grain size. To achieve high coercivity in FePt–Si–N film, the Si/N atomic ratio has to be well controlled. - Highlights:: ► Small thickness and appropriate Fe content benefit perpendicular orientation. ► Ordering temperature for FePt–Si–N films is ∼100 °C higher than that of FePt films. ► Both FePt and FePt–Si–N films have the highest coercivity at Fe content of 55 at%. ► Doping Si–N improves coercivity by reducing exchange coupling and grain size. ► Si/N ratio has to be well controlled to achieve high coercivity in FePt–Si–N film