Department of Physics & The Applied Magnetics Laboratory of the Ministry of Education, Lanzhou University, 730000 Lanzhou, China;
Max-Planck-Institut fur Festkorperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany

In order to investigate the phase stability of equiatomic FeN compounds and the structure-dependent magnetic properties, the electronic structure and total energy of FeN with NaCl, ZnS and CsCl structures and various magnetic configurations are calculated using the first-principle TB-LMTO-ASA method. Among all the FeN phases considered, the antiferromagnetic (AFM) NaCl structure with q = (0,0,p) is found to have the lowest energy at the theoretical equilibrium volume. However, the ferromagnetic (FM) NaCl phase lies only 1mRy higher. The estimated equilibrium lattice constant a^th=4.36Å for nonmagnetic (NM) ZnS-type FeN agrees quite well with the experimental value of a^exp=4.33Å but for AFM NaCl phase the a^th =4.20Å is 6.7% smaller than the value observed experimentally. For ZnS-type FeN, metastable magnetic states are found for volumes larger than the equilibrium value. With the analysis of atom- and orbital-projected density of states (DOS) and orbital-resolved crystal orbital Hamilton population (COHP) the iron-nitrogen interactions in NM-ZnS, AFM-NaCl and FM-CsCl structures are discussed. The leading Fe-N interaction is due to the d-p iron-nitrogen hybridization while considerable s-p and p-p hybridizations are also observed in all three phases. The iron magnetic moment m_Fe in FeN is found to be highly sensitive to the nearest-neighboring Fe-N distance. In particular, the m_Fe in ZnS and CsCl structures show an abrupt drop from the value of about 2m_B to zero with the reduction of the Fe-N distance.
 

A reprint of this paper can be obtained here.

J Phys: Condens. Matter, 12 4161-73, 2000.