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)/ In_0.2Ga_0.8As (001) and on In_0.2 Ga_0.8As (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 3.1μ_B to 3.3μ_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.