Effect of Cr3+ substitution on the magnetic and dielectric properties of cobalt ferrites

Abstract

Co(Fe1-xCrx)2O4 (x = 0.02, 0.10, 0.15, 0.30, 0.50) samples are synthesized by the sol-gel method. The XRD patterns and subsequent Rietveld refinement provided structural analysis and confirmation of the samples' single-phase formation. XPS measurement reveals the existence of the elements Co, Cr and Fe in 2+ and 3+ oxidation states. The saturation magnetization (Ms), coercivity (Hc) and magnetocrystalline anisotropy (K1) are observed to decline to as low as 10 emu/g, 35 Oe and 0.50 (106 erg/cm3) following Cr substitution, which indicated that the samples transform to a soft magnetic material. Cr substitution also lowers the ferrimagnetic (FiM) to paramagnetic (PM) transition temperature, Tc, from 752 K for x = 0.02 to 307 K for x = 0.50. With Cr replacement, the dielectric constant and dielectric loss values decrease, indicating it to be a potential contender for high frequency applications. The dielectric constant for x = 0.30 and x = 0.50 samples rises sharply around 1 MHz owing to the LC resonance effect between the samples and the measurement leads. The ac conductivity plots are found to be in conformity with Jonscher's single power law, and the conduction process is revealed to be attributable to the small polaron hopping mechanism.