Angular Dependence of Demagnetization Processes in Fe-FePt Perpendicular Bilayers

The angular dependence of hysteresis loops of exchange-spring (ES) bilayers constituted by a Fe layer as the soft phase and a hard layer of L10 Fe53Pt47 is presented. FePt thin films of nominal thickness 10 nm have been prepared by RF sputtering on MgO (1 0 0) substrates in order to achieve the epitaxial growth with the c-axis perpendicular to the film plane. The Fe soft layers have been deposited at RT with various thicknesses (from 2 to 10 nm). The angular dependence of the bilayers’ magnetic properties is studied by SQUID magnetometry varying the angle between the easy axis of the hard phase and the direction of the applied field from 0 to π/2. The magnetic behavior at different angles is analyzed by a one-dimensional micromagnetic model specifically extended to the case of perpendicular magnetic anisotropy (PMA).