Structural and magnetic properties of NiZn-ferrite thin films prepared by radio frequency magnetron sputtering

Polycrystalline NiZn-ferrite thin films were deposited on Si(100) substrate by rf magnetron sputtering, using targets with a nominal composition of Ni0.5Zn0.5Fe2O4. The effects of substrate condition, sputtering pressure, and postannealing on the structure and magnetic properties of thin films have been investigated. Our results show that the preferred orientation of the NiZn spinel film changed from (311) to (400) with increasing the Ar pressure from 0.8 to 1.6 Pa, meanwhile, the grain size also increased. Atomic force microscopy analysis indicates that perfect surface morphology of the film can be obtained at a relatively lower sputtering pressure of 1.0 Pa. The relative percentage of residual oxygen increases significantly on a condition of lower sputtering pressure, and plays an important role in film structure due to the strong molecular adsorption tendency of oxygen on the film surface during the deposition process. A thin film with a typical thickness of 1 μm, a saturation magnetization of 150 emu/cm3, and a coercivity of 8.8 kA/m has been obtained after annealing at 800 deg. C, which has the potential application in magnetic integrated circuits.