Magnetization reversal in CoPt-based hard–soft homocomposites

CoPt-based hard–soft sputtered bilayers with (1 1 1) texture have been produced by appropriate heat treatment of the bottom layer. Two samples with different degrees of chemical ordering of the hard layer are compared. The anisotropy of the hard layer determines its robustness against destabilization from the soft one. Detailed measurements of the soft layer minor hysteresis loop features as a function of the magnetic state of the hard layer are proposed as a means to study the nature of interfacial exchange interactions and the mechanism of magnetization reversal. When hard layer anisotropy is not robust enough, the reversed soft layer can induce irreversible changes to the magnetic structure at the interface leading to a decoupling of exchange field from the magnetic state of the hard layer.