Role of growth parameters on structural and magnetic properties of Fe4N thin films grown by reactive magnetron sputtering

Abstract

We studied the effect of growth parameters on the phase formation of Fe4N in a reactive sputtering process. The Fe4N phase formation was found to be extremely sensitive to N2 gas flow and sputter rate but not so much on the substrate temperature. But post-deposition annealing (PDA) time was found to be a critical parameter to get single phase Fe4N. As PDA time increases, the anti-bonding states characteristic of Fe4N start to diminish due to N out-diffusion. Signatures of such N diffusion process can also be seen from the Fe and N depth profiles. We found that the residual resistivity ratio was maximum for the optimized Fe4N films. Magnetization measurements were performed using bulk magnetization as well as polarized neutron reflectivity. We found that the magnetic moment of optimized Fe4N film was about 2.3 μB/atom at 15 K. Magnetic anisotropy measurements carried out using magneto optical-Kerr effect exhibit a rotatable anisotropy.