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.