From FePt–Fe3O4 to L10-FePt–Fe nanocomposite magnets with a gradient interface

Abstract

We report a novel approach for the fabrication of exchange-coupling L1₀-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 L1₀-FePt phase. Then Fe₃O₄ in FePt–Fe₃O₄ dumbbell shaped NPs is reduced to bcc-Fe by low temperature annealing in reducing gas, forming L1₀-FePt–Fe nanocomposites. The L1₀-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.