Grain size reduction and magnetic properties improvement by in situ annealing of FePt epitaxial thin films

FePt thin films were epitaxially grown by RF sputtering on MgO (1 0 0) substrates at 550 °C, followed by in situ annealing at the same temperature. The in situ annealing was found to improve the magnetic characteristics: i.e., the increase in magnetic squareness up to 0.9 and increase in the ratio between anisotropy and coercivity (ε=anisotropy field/coercive field=35.9 for 115 min annealing). Remarkably, a decrease in grain size was also found to occur by increasing the annealing time.