Influence of hydrogen on the growth of FePt thin films

FePt films have been prepared by pulsed laser deposition on MgO(100) in a forming gas atmosphere of 5% hydrogen in argon. At a pressure and temperature combination of 0.1 mbar and 800 °C, smooth continuous and well ordered L 10 phase films can be obtained. The anisotropy field is close to the bulk value, while the coercivity is comparatively low at 0.15 T. This is in contrast to films deposited in vacuum, which are granular in nature and show huge coercivity. It is proposed that nucleation centers for island growth introduced by hydrogen on the MgO surface are responsible for this difference in growth mode. The temperature and pressure dependence of the surface morphology are explained by this assumption.