Electronic structures and magnetic properties of the rare-earth-free permanent magnet α′′-Fe16N2: first-principles calculations

Abstract

There are challenges in the production and application of rare-earth permanent magnet (PM) materials due to resource distribution, cost, environmental unfriendliness, and recycling difficulties. Thereby, the demand for high-performance rare-earth-free PMs has increased rapidly over the past decade. Body-centered tetragonal α′′-Fe₁₆N₂ is a promising candidate for future rare-earth-free PMs due to the low cost of Fe, environmental friendliness and high energy. In this work, the electronic structures and magnetic properties of body-centered tetragonal α′′-Fe₁₆N₂ are investigated by first-principles calculations. The total magnetic moments of α′′-Fe₁₆N₂ are 38.59μ_B per cell, equivalent to 2.41μ_B/Fe atoms. Through band and density of state analysis, α′′-Fe₁₆N₂ is found to present metallic and ferromagnetic character. The magnetocrystalline anisotropy energy (E_MCA) of α′′-Fe₁₆N₂ is −0.66 J cm⁻³, showing perpendicular magnetic anisotropy (PMA). PMA can be mainly ascribed to the spin–orbit-coupling between (d_z², d_yz) and (d_xz, d_yz) orbitals at the Fe(8h) site. The Curie temperature of α′′-Fe₁₆N₂ is 1369 K, which is larger than that of pure bcc-Fe (1023 K). Therefore, α′′-Fe₁₆N₂ possessing PMA and high Curie temperature is a potential rare-earth-free PM candidate material, which has application prospects in high temperature data storage devices, traction motors, wind turbines and power generating machines.