Effect of Er substitution on the magnetic, Mössbauer spectroscopy and dielectric properties of CoFe2−xErxO4 (x = 0.00, 0.01, 0.03, 0.05) nanoparticles

Abstract

The effect of Er content on sol-gel derived CoFe2−xErxO4, (x = 0.00, 0.01, 0.03, 0.05) nanoparticles was investigated by XRD, FTIR, SEM, Mössbauer spectroscopy, magnetic and dielectric measurements. The formation of cubic spinel structure and the presence of molecular bonding of functional groups were confirmed by XRD and FTIR spectroscopy. The average crystallite size is reduced from 61 to 18 nm with the increase of Er content. The decrease in crystallite size is due to the suppression of grain growth upon Er3+ occupation at the octahedral site. SEM study revealed the formation of nano size particles which dispersed uniformly. Mössbauer spectra, taken at room temperature (RT) confirmed the presence of ferromagnetic sextets demonstrating the existence of Fe both in the tetrahedral and octahedral sites. The magnetic properties were measured at 300 K, 100 K and 5 K using a Physical Properties Measurements System (PPMS). The saturation magnetization (Ms) of CoFe2O4 was found to be 95.92 emu/g which is much higher than the bulk ferrite (80.8 emu/g) and the maximum Ms 120 emu/g was found for 0.01 Er content. The coercivity increases with the increase of Er content which has a direct relationship with crystallite size and single-domain behavior of nanoparticles. The maximum coercivity is found to be 855 KA/m at 5 K which is the highest compared to the rare earth doped ferrites. The impedance analysis fallouts the relative permittivity and dielectric loss decrease while AC conductivity increases with increasing frequency for all samples. The obtained results signify CoFe2−xErxO4 as a potential candidate for magneto-electric sensors and high frequency electromagnetic devices application.