Magnetization reversal of FePt hard/soft stacked nanocomposite particle assembly

Microstructure and magnetic properties of interfacially disordered FePt nanoparticles with a diameter of about 10 nm were investigated. Sputter deposition of amorphous Al2 O3 overlayer caused the disordering of L 10 -FePt particles at the interface. The assembly of these partially disordered FePt nanoparticles is equivalent to the composite medium consisting of the exchange coupled soft and hard layers. Coercivity Hc of the interfacially disordered FePt nanoparticles significantly decreased with increasing thickness of the disordered layer. Comparison with theoretical calculations has shown that this reduction of Hc is attributed to the so-called spin flop state during the magnetization reversal. The interfacial disordering method has been demonstrated to be a promising technique for fabricating FePt-based soft/hard stacked composite media.