Magnetic properties of epsilon-iron nitride

Abstract

The magnetic properties of epsilon-iron nitride were investigated in order to determine the magnetic structure of the material, and to determine what influence, if any, the nitrogen atoms have on the magnetic moment of the iron atoms. A sample of composition Fe 3N 1.17 was studied both by neutron diffraction at room temperature and by measuring the bulk magnetization between room temperature and liquid nitrogen temperature. The neutron diffraction data can be interpreted on the basis of a simple model with the spin vectors of the iron atoms ferromagnetically aligned parallel to the hexagonal c axis and with an average moment of 1.5microB per iron atom. This value is in good agreement with that of 1.33microB obtained by extrapolating the magnetization curve to 0°K. Taking 1.26 Å as the radius of the iron atoms, the atomic radius of the nitrogen atoms is calculated to be 0.66 Å, a considerable contraction as compared to the normal covalent nitrogen radius of 0.77 Å. The observed decrease in the moment of the iron atoms and the decrease in the atomic radius of the nitrogen atoms both indicate that nitrogen does not act as an electron acceptor in this material. These results indicate that the electronic exchange process between the nitrogen and the iron atoms in Fe 3N is similar to that postulated by W iener and B erger (1) between the nitrogen and the three face centered iron atoms in Fe 4N.