L1(0)-FePt particles disorder at the interface when an amorphous Al2O3 layer is capped on an ordered FePt particulate film at room temperature. The coercivity decreases drastically as a result. Interfacial disordering does not progress when the capped layer is deposited at elevated temperature, indicating that the disordering is driven by the strain at the interface. The FePt particulate film becomes magnetized more easily by the Al2O3 capping. (C) 2004 American Institute of Physics.