Annealing effects and perpendicular magnetic properties of sputtered Co 2 FeSi alloy films

A series of Co 2 FeSi (CFS) films sandwiched by MgO and Pt layers are sputtered. For the as-deposited films, the magnetic easy axis lies in the sample plane. After annealing, perpendicular magnetic anisotropy (PMA) is shown to build in the stacks with CFS thickness ranged from 2.5 to 3.8 nm and is determined to be the order of 10 5 –10 6 erg/cm 3 in magnitude. The largest saturation magnetization of 1009 ± 41 emu/cm 3 , close to the bulk value of CFS, is obtained in the annealed stacks. The thickness of a magnetic dead layer is shown to monotonically increase with annealing temperature. This can be ascribed to the progress of the oxidation from the CFS/MgO interface with annealing temperature. No PMA is observed without Pt buffer or MgO top layers. The positive contributions to the PMA made by the Pt/CFS and CFS/MgO interfaces are experimentally verified. The strong PMA is shown to be maintained in the stacks with 4 nm Pt buffer and 0.5 nm MgO layers after high-temperature annealing. Our results provide some useful information on the design for the next generation of CFS-based spintronic devices.