Interfacilly Disordered FePt hard/soft Stacked Structures

L10-FePt is a promising material for ultra high density magnetic recording media due to its high magnetocrystalline anisotropy (Ku). However, the switching field (Hsw) of the L10-FePt particle is too large to write by the currently used write head. Hard/soft stacked media are proposed to solve this problem. Recently, we demonstrated that the coercivity of isolated FePt particles can be reduced by introducing a thin disordered layer on FePt particles by capping them with amorphous Al2O3. Since the Ku of the disordered FePt is much smaller than that of the L10 FePt, the interfacially disordered FePt particle is equivalent to the hard/soft stacked structure. In this study, we have investigated the magnetization reversal process using the partially disordered FePt particles that are smaller than the critical size for coherent rotation.