Towards Stabilization of L1_0-type FeNi Compounds for Permanent Magnet Applications

摘要

Magnetic compounds comprised of FeNi with the tetragonal L1_0 structure are reported to possess the high magnetization and significant magnetocrystalline anisotropy, derived from the lower-symmetry crystal structure, necessary for advanced permanent magnet applications that can enable transformational clean energy technologies. This compound has only been observed to form naturally as tetrataenite, a component of many stony, stony-iron, and iron meteorites with a crystallite size that is a function of the cooling rate of the meteorite within its parent asteroidal body. Typical cooling rates vary from 0.2 K/Myr to 2,000 K/Myr and foster long-range chemical ordering at the low temperatures (< 300 °C) where the tetrataenite phase forms. While tetrataenite possesses a high magnetization and high anisotropy, its low chemical ordering temperature of 320 °C indicates that the disorder→order transformation in L1_0 FeNi is kinetically limited by low atomic mobilities at these temperatures.