SYNTHESIS AND PROPERTIES OF NI-ZN FERRITE THIN-FILMS

We have investigated the magnetic and structural properties of polycry stalline Ni-Zn ferrite thin films with thicknesses of about 1000 Angst rom. The films were prepared by R F sputtering deposition in 1.5x10(-3 ) mbar argon atmosphere, using targets with nominal composition Ni0.7Z n0.3Fe2O4. The effects of substrate temperature and post deposition he at treatment of thin films were examined. The X-ray spectra of Fe-Ni-Z n oxides deposits reveal the formation of spinel phase of Ni-Zn ferrit e. that is characteristic for these materials. only for temperatures h igher than 500 degrees C. TEM and ED indicate that the initially amorp hous thin films. deposited at 100 degrees C, become polycrystalline by heat treatment. The grain size of the crystallites is 800 Angstrom to 1000 Angstrom for Ni-Zn ferrite thin films annealed at 900 degrees C. V.S.M. measurements show coercive fields of 12 kA/m for thin films an nealed at 900 degrees C. which are larger than those found for Ni-Zn f errite targets. This value of coercive field is related to the shape a nisotropy originated by the film microstructure and with the increase in the number of low angle grain boundaries, which act as pinning site s for domain walls. Saturation magnetization values of 220-250mT for N i-Zn ferrite thin films are higher than half of bulk values.