Structural and magnetic properties of FePt film with Cu top layer diffusion

The top or bottom layer diffusion through grain boundary is believed to be one promising method for magnetic isolation. In the paper, the effects of the Cu top layer thickness and thus annealing time on the structural and magnetic properties of the FePt (001) film were investigated. The XPS in-depth profile shows that the diffusion is not through the whole film. The M-H loop slope decreased from 14.9 to 2.53 and the coercivity increased drastically from about 3100 to 6000Oe when a 4nm Cu capping layer was deposited, which indicates that the exchange coupling between the FePt grains was reduced. The magnetic anisotropy (Ku) firstly decreases from 1.54x107 to 1.12x107erg/cm3 after the deposition 2nm Cu top layer and remains almost constant with 4nm Cu top layer. But the long time annealing will cause the significant decrease of the Ku due to the bulk lattice diffusion. The magnetic reversal process without Cu top layer is dominated by domain wall motion and tends to be rotation mode related to nucleation with the increase of the Cu top layer