Dielectric and magnetic properties of Cu-doped Ni0.65Zn0.35Fe2O4 thin films prepared by using a sol-gel method

Abstract

Ni_(0.65)Zn_(0.35)Cu_xFe_(2-x)O₄ thin films were prepared by using a sol-gel method. Their crystallographic, dielectric and magnetic properties were investigated as a function of Cu contents by means of an X-ray diffractometer (XRD), X-ray reflectivity, LCZ meter (NF2232), a vibrating sample magnetometer (VSM), and an atomic force microscope (AFM). From typical C-V measurements for Ni_(0.65)Zn_(0.35)Cu_xFe_(2-x)O₄ thin films on p-type silicon substrate, the surface charge density was calculated as 1.4 μC/㎡. The dielectric constant evaluated from the capacitance at the accumulation state was 28. The high Hc and low Msat at x=0.0 and 0.1 were due to the growth of the α- Fe₂O₃ phase having antiferromagnetic properties. The rapidly decreased Hc and increased Msat at x=0.2 and 0.3 can be explained that the α- Fe₂O₃ phases have completely disappeared at x=0.3 and so, non-magnetic defects are minimized. The Msat was slightly decreased and the Hc was increased above at x=0.3 because the increase of grain boundary due to smaller grain size acts as defects during magnetization process