Fe-Ni-N based alloys as rare-earth free high-performance permanent magnet across α to L10 phase transition: A theoretical insight

Over the years, simultaneous enhancement of the energy density product and thermal stability of 3d-only metals, without including heavy metals or rare-earth elements, has been a tremendous challenge in the field of permanent magnetism. In this study, we investigate the structural stability and intrinsic magnetic properties of (Fe1-xNix)(16)N-2 (x = 0-1) across the alpha '' to L1(0) phase transition using the systematic density-functional theory and Monte Carlo simulations. We theoretically demonstrated an extremely large enhancement in the uniaxial magnetic anisotropy (Ku), up to 1.8 MJ.m(-3) in the L1(0)-type (Fe0.5Ni0.5) N-16(2) , a value roughly three times those of alpha ''-Fe16N2(0.6 MJ.m(-3)) and L1(0)-FeNi (0.68 MJ.m(-3)). Simultaneously, it is predicted that the resulting L1(0)-type (Fe0.5Ni0.5) N-16(2) phase is energetically more stable than the alpha ''-Fe16N2 phase. Further calculations reveal that in L1(0) -type (Fe0.5Ni0.5) N-16(2) , K-u can increase up to nearly 3.9 MJ.m(-3) with additional interstitial N atoms. In conclusion, we predict that the Fe16N2-based compounds can be effectively used as efficient rare-earth free permanent magnets by simultaneously enhancing their structural stability and energy product (BH)max. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study focuses on enhancing the magnetic anisotropy Ku and thermal stability in Fe16N2-based permanent magnets using density-functional theory and Monte Carlo simulations. Results show that adding N atoms can increase Ku and Fe16N2-based compounds have the potential to be efficient rare-earth free permanent magnets.