Magnetic properties of nanocrystalline N-NFO thin films

Abstract

The pure as well as nitrogen incorporated nickel ferrite (NFO and N-NFO) thin films were grown by radio frequency magnetron sputtering technique. The structural investigations of as-grown N-NFO films using GIXRD and Raman spectroscopy revealed nanocrystalline nature of the films. The microstructural and surface studies of the films using SEM and atomic force microscope micrographs showed increase in crystallite size and decrease in surface roughness with increase of sputtering power. The magnetization (M-H) measurements at 20 and 300 K revealed an increase in magnetization and decrease in coercivity values with increase of sputtering power. However, no saturation of magnetization ( $M_{s}$ ) was visible for the thin film samples, indicating superparamagnetic behavior due to nanocrystallinity. The comparison of in-plane and out-of-plane magnetizations of the N-NFO film (both at 20 and 300 K) showed that the easy magnetization direction lied in the plane of the film. The optical transmission spectra revealed decrease of direct band gap with increase of sputtering power.