Microstructure and improved coercivity of Mn1.33Ga nanoflakes by surfactant-assisted ball milling

摘要

In recent years, MnGa alloys with tetragonal structure have attracted much attention because of the erratic fluctuation of rare earth supply and especially the tunable magnetic properties from fer-rimagnetic to ferromagnetic by varying Mn content. It is theoretically estimated that MnGa compound in L1 structure owes high anisotropy constant K of 26 Mergs/cm and magnetization Ms of 845 emu/cm, and thus can be regarded as a potential candidate for rare-earth-free permanent magnets. At present, surfactant-assisted high-energy ball milling (HEBM) method has been regarded as one of the effective ways to realize high coercivity for magnetic materials with large anisotropy. It was reported that high-aspect-ratio single-crystal or textured polynanocrystalline flakes of Sm-Co-based permanent magnetic materials with a submicron or nanosize thickness and high coercivity can be achieved. In this study, textured rare-earth-free MnGa polycrystalline nanoflakes were prepared by surfactant-assisted HEBM in heptane with 15wt. % oleic acid (OA), and the effects of milling time on structure and magnetic properties were also investigated.