DFT calculation and experimental investigation of Mn doping effect in Fe16N2

An effective dopant to improve the thermal stability of a Fe16N2 permanent magnet is proposed in this paper. It is demonstrated both theoretically and experimentally that manganese is a promising candidate as dopant in Fe16N2 magnet to improve the thermal stability. Firstly, the atomic moments of the Fe ions with respect to N is investigated by using first-principles DFT calculation. Two possible candidates of elements, including Co and Mn, are compared in terms of its preferred position and magnetic coupling mode. It is found that Mn prefers Fe1 position and ferromagnetic coupling in the Fe16N2 lattice. So Mn is considered as a promising dopant in Fe16N2 magnet to improve its thermal stability. Based on theoretical results, experiments are conducted by a cold-crucible method to prepare (Fe1-xMnx) N bulk samples. The samples are thermal treated at different temperatures to observe their thermal stabilities. X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) are characterized on the samples.