Abstract
Ca–Ni co-substituted samples of nanocrystalline spinel ferrites with chemical formula Mg1−xCaxNiyFe2−y O4 (x=0.0–0.6, y=0.0–1.2) were synthesized by the micro-emulsion method and were annealed at 700°C for 7h. The synthesized samples were characterized by x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM) and dielectric measurements. The XRD and FTIR analysis reveals that single phase samples can be achieved by substituting Ca and Ni ions at Mg and Fe sites respectively in cubic spinel nano-ferrites. The crystallite size of the synthesized samples was found in the range 29–45nm. The saturation magnetization (Ms) increases from 9.84 to 24.99emu/g up to x=0.2, y=0.4 and then decreases, while the coercivity (Hc) increases continuously from 94 to 153Oe with the increase in dopants concentration. The dielectric properties of these nano materials were also studied at room temperature in the frequency range 100MHz to 3GHz. The dielectric parameters were found to decrease with the increased Ca–Ni concentration. Further the peaking behavior was observed beyond 1.5GHz. The frequency dependent dielectric properties of all the samples have been explained qualitatively on the basis of the Maxwell–Wagner two-layer model according to Koop's phenomenological theory. The enhanced magnetic parameters and reduced dielectric properties make the synthesized materials suitable for switching and high frequency applications, respectively.