Effect of Cr3+ substitution on magnetic and electrical properties of (Ni0.3Cu0.7) Fe2O4 spinel ferrites

Chromium substituted copper base spinel ferrites (Ni 0.3 Cu 0.7 )Cr x Fe 2-x O 4 were prepared by Sol-gel method. Structural, magnetic and electrical properties were studied by utilizing X-ray diffractometer, Vibrating sample magnetometer, and precision LCR-meter using lab-tracer software. The X-ray diffraction analysis confirmed the formation of single phase fcc structure of the samples. The lattice constant and crystallite size decreased from 8.37-8.23A and 53.09-35.36nm respectively with increasing content of Cr 3+ ions. From MH loops it was observed that the saturation magnetization decreased and coercivity increased with increasing content of Cr 3+ ions. Dc resistivity increased with increase of Cr 3+ concentration and decreased with increase in temperature which shows the semiconducting behavior of ferrites. The dielectric constant, dielectric loss and tangent loss decreased with increase of Cr 3+ concentration. The dielectric constant follows bilayer Maxwell Wagner model and Koop’s phenomenological theory while ac conductivity increased with increasing frequency following Jonscher’s power law.