Interface-driven magnetic anisotropy of epitaxial Fe4N thin films

Abstract

The effect of film-substrate interface on the magnetic anisotropy (MA) of epitaxial Fe4N thin films grown on single crystalline MgO (100) and MgO (111) substrates has been studied in this work. Both samples were grown simultaneously using a reactive dc magnetron sputtering process at a substrate temperature of 250°C. Single phase Fe4N samples were found to grow epitaxially on (100) and (111) oriented MgO substrates as confirmed from out-of-plane x-ray diffraction and in-plane ϕ-scan measurements. The MA of (100) and (111) oriented Fe4N samples was measured using longitudinal magneto-optical Kerr effect (MOKE). In spite of being grown simultaneously, the MA of both these samples was found to be different. Secondary ion mass spectroscopy and x-ray reflectivity measurements revealed the formation of a dense layer at the film-substrate interface. The MA of this dense layer along with the MA of Fe4N has a dramatic effect on magnetic reversal depending on the orientation of the substrate. Further, from the MOKE measurements, the difference in the magnetization switching processes was found to depend on the microstructure and orientation of Fe4N thin films.