DC Electrical Resistivity, Dielectric, and Magnetic Studies of Rare-Earth (Ho3+) Substituted Nano-Sized CoFe2O4

The effect of Fe substitution by rare-earth (Holmium; Ho3+) ions in CoFe2O4 (CFO) prepared by glycine nitrate process is investigated from electrical, dielectric, magnetic, and Mossbauer perspectives. The anticipated spinel cubic phase structure is confirmed by X-ray diffractometry and Fourier transform infrared (FTIR) analysis which support the presence of a secondary phase of HoFe2O3 at higher Ho content. Field emission scanning electron microscope (FESEM) and transmission electron microscopic (TEM) micrographs confirmed that the incorporation of Ho3+ significantly reduced the grain size of the samples from 50 nm to 20 nm. The complex impedance and modulus spectroscopy are investigated as a function of frequency in the regime of 10(2)-10(6)Hz in the temperature range of 30-300 degrees C. The conduction mechanism is attributed to the hopping of both electrons and holes. Activation energies (E-a) obtained from the Arrhenius plots of the grain and the grain boundary conductions are ascribed to the hopping of charge carriers. Electrical modulus results specify the existence of the non-Debye type of dielectric relaxation. A massive reduction in loss factor is successfully achieved. Room temperature magnetization measurements indicate a reduction in saturation magnetization and coercivity (hysteresis losses) with increasing Ho3+ content, which entails these materials to be used for magnetic data storage and magneto recording devices.