Effects of magnetic ordering and electron correlations on the stability of FeN

Abstract

Iron mononitride has attracted much interest because of its interesting magnetoelectric properties. However, whether the ground state of FeN has a rock-salt (rs) or a zinc-blende (zb) structure is still controversial. Clarification of this issue has been impeded by the complex magnetic ordering and strong electron correlation effects. Here, we study the relative stability of rs and zb FeN toward different spin orderings (ferromagnetic, antiferromagnetic, and paramagnetic) at pressures of 0–100 GPa, with the GGA-PBE, LDA+U, and HSE hybrid exchange–correlation functionals. We find that the competition between direct and indirect exchange interactions can drive magnetic structure phase transitions for rs-FeN at high pressures, whereas zb-FeN is still nonmagnetic. Strikingly, the energy difference between rs and zb FeN decreases and finally vanishes as the occupied minority-spin t_2g orbitals of rs-FeN are depleted when 3d electron correlations are considered. These results demonstrate that an appropriate treatment of electron correlations is important for determining the stability and properties of 3d transition metal nitrides.