Physical, electrical and magnetic properties of nanocrystalline Zr-Ni doped Mn-ferrite synthesized by the co-precipitation method

Nanosized cobalt-manganese ferrites with nominal compositions, Co0.5Mn0.5Fe2-2xZrxNixO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8) have been synthesized by the co-precipitation method. The samples are characterized by X-ray diffraction (XRD), dc electrical resistivity and magnetic hysteresis loops measurements. The XRD data showed that all the samples are of single phase and the crystallite size is found to be in the range of 16-18 nm. The lattice constant (a), X-ray density (ρx), porosity (P) and bulk density (ρm) are also calculated from XRD data. The dc electrical resistivity of all the samples is measured in temperature range of 303-723 K and is found to decrease with temperature indicating the semiconductor nature of the synthesized materials. The room temperature electrical resistivity of the samples is found to increase from 0.22 x 107 to 14.5 x 107 Ω cm and the activation energy from 0.34 to 0.40 eV, respectively, the drift mobility, however decreases from 21.3 x 10-11 to 1.41 x 10-11 cm2 V-1 S-1 with dopant concentration. This variation in electrical resistivity, drift mobility and activation energy is explained on the basis of the site occupation of the dopants. The saturation magnetization (Ms) increases from 18.33 to 50.63 emu/g up to x = 0.4 and then decreases, while the coercivity (Hc) decreases. The increase in the dc electrical resistivity and saturation magnetization suggest that the synthesized materials are suitable for their applications in high density recording media and microwave devices.