Microstructure and magnetic properties of Ni-Zn ferrite thin film synthesized using sol-gel and spin-coating technique

The nanocrystalline Ni-Zn ferrite thin film with the chemical formula Ni0.3Zn0.7Fe2O4 were deposited on glass substrate using sol-gel synthesis of metal nitrate aqueous solutions and spin-coating technique. Thin films of nickel-zinc ferrite have been prepared using spin-coating technique onto the ITO glass substrates. As-deposited films are annealed at 400, 500, 600 and 700 °C for 1 h. The Ni-Zn ferrite thin film with crystallite size of 20 nm has been successfully synthesized. The thickness of deposited films was below 300 nm and crystallite size was below 20 nm. The X-ray diffraction (XRD) analysis found the Ni-Zn thin films nanoferrite has a spinel cubic structure and lattice parameter of Fd3m. The crystallinity of the prepared Ni-Zn ferrite films increases as increase substrate temperature of a film deposition. Microstructures and chemical analysis by scanning electron microscopy and energy-dispersive spectroscopy showed that nanosized nickel-zinc ferrite particles with a diameter of 18.6 to 41.3 nm exist in the thin film. Magnetic properties of the Ni-Zn films have been characterised at room temperature, whereas the saturation magnetization Ms. of the Ni-Zn films increase with increasing grain sizes. Maximum saturation magnetization Ms. and coercivity Hc are 3.42 emu/g and 16.54 Oe for thin films annealed at 500 and 700 °C, respectively. The Ms. of the films shows a trend increasing and the Hc value decreasing as increase the annealed temperature and the grain size of the Ni-Zn ferrite thin films. The conductivity decreases with increasing annealed temperature. It has been shown that the DC resistivity, saturation magnetization and coercivity of deposited films are influenced by annealing temperatures. The magnetic properties of Ni-Zn thin film with grain size of 18.6–41.3 nm shown a superparamagnetic behaviour were observed.