Magnetic Properties of Fe16N2 Films

Epitaxial growth of single-phase Fe16N2 single crystal films and the giant magnetic moment of such films are reviewed, along with partial formation of Fe16N2 by implantation of N ions into Fe films. Fe16N2 single crystal (110) and (001) films have been grown epitaxially on Fe (001)/ In0.2Ga0.8As (001) and on In0.2 Ga0.8As (001) substrates, respectively. Both films were found to have a saturation magnetic flux density Bs of from 2.8 T to 3.0 T (from 3.1¿B to 3.3¿B per Fe atom) at room temperature. This is in good agreement with the value (2.83 T) estimated by Kim and Takahashi from the Bs of polycrystalline Fe-N films consisting of Fe and Fe16N2 crystallites. The origin of the giant magnetic moment is discussed on the basis of Mossbauer spectroscopy and calculations using the local density functional approximations of Sakuma.