Effects of annealing processes on the crystallization and magnetic properties of nickel ferrite thin films

Abstract

Magnetic nickel ferrite (NFO), NiFe2O4, thin films were fabricated using the chemical solution deposition method on (100)-oriented silicon substrates. The effects of an annealing process on the crystallization and magnetic properties of NFO thin films were investigated. Two annealing methods were used, namely layer-by-layer multiple rapid-annealing process and single slow-annealing process. The results showed that the appropriate pyrolysis temperatures range from 400 to 500°C. NFO thin films crystallized well when they were annealed at 750°C or above. The NFO thin films fabricated using the single slow-annealing process (NFO-S) show better crystallinity compared to the films fabricated using the layer-by-layer multiple rapid-annealing process (NFO-R) when the annealing temperatures were low. NFO-R thin films show preferred (400) orientation growth and the relative intensity of the (400) peak raises with the annealing heating rate. Fine magnetic hysteresis loops and good magnetic properties were observed in both NFO-S and NFO-R thin films. A saturation magnetization of 277 emu cm−3 was derived for the NFO-S thin films, compared to a 230 emu cm−3 for the NFO-R thin films, which is a very high value compared with former reported values for NFO thin films.