From FePt-Fe3O4 to L1(0)-FePt-Fe nanocomposite magnets with a gradient interface

摘要

We report a novel approach for the fabrication of exchange-coupling L1(0)-FePt-bcc-Fe nanocomposites with a gradient interface between hard and soft phases from FePt nanoparticles (NPs) and FePt-Fe3O4 dumbbell shaped NPs, which are prepared by a facile one-pot synthesis method. High temperature annealing in argon is first used to convert FePt in FePt-Fe3O4 dumbbell shaped NPs to the L1(0)-FePt phase. Then Fe3O4 in FePt-Fe3O4 dumbbell shaped NPs is reduced to bcc-Fe by low temperature annealing in reducing gas, forming L1(0)-FePt-Fe nanocomposites. The L1(0)-FePt-Fe nanocomposites exhibit both large coercivity and high magnetic moment. The work demonstrates that creating a nanoscale gradient interface between magnetically hard and soft phases is a promising approach for the fabrication of high performance permanent magnets.