Synthesis of α”-Fe16N2 foils with an ultralow temperature coefficient of coercivity for rare-earth-free magnets

Abstract Magnets with a low-temperature coefficient of coercivity (TCC) have various applications in a varying temperature environment. Rare-earth magnets like NdFeB are widely used, but they usually have a large negative TCC. Here, it is first experimentally demonstrated that α”-Fe16N2 foils, as a candidate for rare-earth-free magnets, have an ultralow positive TCC (0.4 Oe/K) from 300 K to 425 K. It is two orders of magnitude smaller than that of the commercial NdFeB magnets in this temperature range. The α”-Fe16N2 foils are made from as-rolled iron foils (25 μm) by a low-temperature nitridation process (