Dependence of structure/morphology on electrical/magnetic properties of hydrothermally synthesised cobalt ferrite nanoparticles

Pure cobalt ferrite nanoparticles were synthesised by hydrothermal method. Cubic spinel structure and improved crystallinity was confirmed by X-ray diffraction analysis. Morphology and average particle size within thenanorange were identified by SEM and TEM. EDX confirmed the presence of Fe, Co, and O elements without any impurities. FT-IR analysis confirmed the presence of vibrational bands in the range of 581-590 cm(-1) and 424-468 cm(-1) ascribed to Fe-O and Co-O bonds, respectively. The presence of five Raman active modes confirmed the cubic spinel-type structure. Optical study revealed the influence of higher annealing temperature on the band gap; it decreases from 2.60 to 1.53 eV. The dielectric constant, dielectric loss and ac-conductivity were found to varywith increasing frequency range. The shifting of cations between tetrahedral (A) to octahedral (B) sites and vice versa was revealed by Mossbauer spectroscopy. The observed sextets proposed that CoFe2O4 nanoparticles are highly crystalline and magnetically ordered. With increasing annealing temperature, both saturation magnetization and remanence increased, while the coercivity was reduced, which is due to the transition from single domain to multidomain on crossing the critical size of similar to 40 nm. The Cyclic Voltammetry (CV) test of nanoparticles annealed at 800 degrees C (S3) revealed excellent specific capacitance at low scan rate.