Dielectric spectra and magnetization hysteresis loops were used to investigate the grain size effect with temperature on the electrical and magnetic response of co-precipitation derived spinel (Ni0.5Zn0.5)Fe2O4 (NZFO) ceramics. Remarkable dielectric relaxation phenomena of non-Debye type have been observed in each NZFO ceramics as confirmed by two kinds of Cole-Cole plots of the 1100 °C sintered samples, mainly due to the electron-hopping mechanism between n-type and p-type carriers and interfacial ion effect when applied an increase of temperature. The high and low response of grain and grain-boundary regions were determined by modeling the impedance experimental results on two equivalent RC circuits taking into account grain deep trap states. By employing the modified Arrhenius equation, activation energy values of different sintering temperatures were calculated and analyzed in combination with oxygen vacancy. In addition, the magnetization of various sintering temperature samples is dominated by cation distribution and surface effect in different particle ranges.

No abstract

No abstract

The influence of nickel doping on the electrical properties and dielectric relaxation in Zn[Formula: see text]Ni[Formula: see text]Fe2O4 (ZNFO, [Formula: see text]) ceramics has been investigated via the dielectric and complex impedance spectra measurements. According to the modified Curie–Weiss law, the diffusivity factor of the ZNFO ceramics from 1.69 to 2.02 with [Formula: see text] increasing from 0.2 to 0.5, respectively. Two relaxation peaks are observed in the nickel doped samples, by employing the modified Arrhenius equation, two activation energy values of different sintering temperatures were calculated and analyzed in combination with oxygen vacancy. The Cole–Cole plots showed that the semicircular arcs which are nonideal Debye type, and the grain boundaries resistance increases with increasing Ni concentration.

Ni 0.5 Zn 0.5 Fe 2 O 4 (NZFO) thin films grown on LaNiO 3 (LNO) buffered Si (100) substrates were prepared by chemical solution deposition. The sample annealed rapidly at 600 • C in oxygen atmosphere. X-ray diffraction result showed that, the sample annealed in oxygen atmosphere is polycrystalline thin film. Field-emission scanning electron microscopy result revealed that the average grain size of the sample is about 20 nm. The magnetic measurement gave a typical value of the saturation magnetization of 0.767 emu/cm 3 . The chemical states and chemical composition of the film was also determined by X-ray photoelectron spectroscopy (XPS).