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 Al2O3 overlayer caused the disordering of L1(0)-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 H-c 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 H-c 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. (c) 2006 American Institute of Physics.