Structure and properties of cobalt ferrite Nanoparticles bulk and Thin Films

Abstract

Abstract newlineA great need for developing new multi-functional materials operating at high frequency (radio frequency) applications is demanding a better understanding of ferrimagnetic materials. In the present study, cobalt ferrite materials were synthesized in nanoparticles, bulk and thin film form by co-precipitation method and RF magnetron sputtering, respectively. The materials of choice, Cobalt ferrite (CoFe2O4), copper doped cobalt ferrites, Co1and#8722;xCuxFe2O4 (x = 0, 0.2, 0.25, and 0.4) and cobalt-copper ferrites, Co1and#8722;xCuxFe2O4 (x =0.0, 0.2, 0.25, 0.4, 0.9 and 1.0) nanoparticles were synthesized using co-precipitation method. The synthesized samples were heat treated at various temperatures to understand its effect on structure and properties of materials. The magnetization and dielectric measurements on the samples heat treated at various temperatures were carried out to optimize these properties of the materials. The crystal structure was verified by X-ray diffraction and Rietveld refined XRD patterns show single phase spinel structure with Fd-3m space group. Surface morphology and microstructure was studied by employing FE-Scanning Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Unusual features in magnetic hysteresis loops of nanoparticles and bulk materials were observed. The dielectric constant and the loss tangent decreases rapidly with increasing frequency, and then reaches almost constant value at high frequencies. CoFe2O4 nanoparticles of size 18 nm heated at 600 °C for 3 hours gives high saturation magnetization (Ms) of 137 emu/g and coercivity ( Hc) of 582 G. CoFe2O4 pellets heated at 1200 oC for 4 h show very high Ms of 175 emu/g. The nanoparticles of (Co0.8Cu0.2Fe2O4) annealed at 600 oC exhibit high Hc of 1217 G and Ms of 119 emu/g. CuFe2O4 pellets heated at 1200 oC exhibit high dielectric constant of 1015 at 40 MHz with low loss tangent of 0.112. This can be used as a filling material in capacitors. As-prepared CoFe2O4 nanoparticles of size 17 nm show a high Hc of 2875 G at RT which