Highly coercive Sm2Fe15Ga2C2 magnets made by intense ball milling

Abstract

Thermodynamically stable nanocrystalline Sm2Fe15Ga2C2 powders were prepared by intense ball milling of homogenized and coarsely ground ingots, and a subsequent annealing of the powders in an argon atmosphere. Such processing results in magnetically isotropic material with a room-temperature coercivity μ0JHc of up to 1.2 T. Scanning electron microscopy observations suggest a homogeneous microstructure, and combined with Scherrer formula estimations, an average grain size of <100 nm has been determined. The coercivity can be preserved at high annealing temperatures when the process is performed at an argon pressure of about 800 mbar. The attempt of a hot-pressing procedure resulted in a magnet with a density of 86% (6.7 g/cm3) of the theoretical density (7.8 g/cm3) and a coercivity of 1.3 T.