Bismuth effect in the structural, magnetic and dielectric properties of CoZn ferrite

Nano particles of Co_0.5Zn_0.5Bi_xFe_(2−x)O₄, with x varying from 0.0 to 0.3 in steps of 0.1 were synthesized using the chemical co-precipitation method. The powder X-Ray diffraction pattern confirms the formation of spinel phase for all prepared samples. The lattice parameters are calculated by powder X-Ray diffraction, and it is observed that the values of the lattice parameter are less than those of bulk materials. The saturation magnetization is found to decrease with the increase of concentration of Bi ion up to x = 0.2 and then increases for x = 0.3. The hysteresis loop for concentration x = 0.0, 0.1 and 0.3 shows almost zero coercivity and remanance at 300 K, implying that the samples behave as superparamagnetic at this temperature; whereas for the concentration at x = 0.2 the coercivity was found to be 32 Oe at 300 K. The dielectric measurements were carried out in the Co_0.5Zn_0.5Bi_xFe_(2−x)O₄ system over the temperature range from 300 to 700 K as a function of frequency, from 5 to 5 MHz. The variation of dielectric constant and dielectric loss factor for the prepared samples are explained on the basis of Maxwell–Wagner interfacial polarization.