The emergence of novel magnetic properties in ternary iron nitrides toward spintronics: first-principles calculations

Fe₄N with a high Curie temperature, large saturation magnetization and good stability has been widely used in spintronic devices. However, the in-plane magnetic anisotropy of Fe₄N limits its further developments in next-generation spintronic devices. Elemental substitution is an effective method to improve the magnetic properties of Fe₄N. Here, the electronic structures and magnetic properties of ternary iron nitrides MFe_4-N (x = 1 and 3, M = paramagnetic, antiferromagnetic, ferromagnetic, or heavy metal elements) are investigated using first-principles calculations. The magnetic moments of Gd₃Fe^fN (21.22μ_B) is 2.14 times larger than that of Fe₄N (9.89μ_B). Due to the antiferromagnetic coupling or low spin state, the total magnetic moments of 0μ_B occur in Cr₃Fe^fN, Y^cFe₃N, and Y₃Fe^fN. The spin polarization values of Cu₃Fe^cN (76.1%), Pt^fFe₃N (68.4%), and Pt^cFe₃N (65.5%) are 1.59 and 1.42, and 1.37 times larger than that of Fe₄N (47.9%). In addition, the tendency from perpendicular magnetic anisotropy (PMA) to in-plane magnetic anisotropy (IMA) in M^fFe₃N and from IMA to PMA in M₃Fe^fN is dependent on the increase in the number of M. These novel magnetic properties provide a new avenue for Fe₄N in next-generation spintronic devices with high density, low energy consumption, and high speed.