Magnetic, dielectric and thermal study of CoNiFe2O4 nanoparticles

Abstract

CoxNi1-xFe2O4 (x = 0.2–0.8) (CNFO) nanoparticles have been prepared using a low temperature hydrothermal technique. X-ray diffraction confirmed the cubic spinel structure of the nanoparticles, offering an increasing trend of lattice parameters from 8330 to 0.8345 nm as a function of Co-content. The microstructures were analysed using FESEM and TEM. The average grain size determined using FESEM images for x = 0.2–0.8 was found in the range from 110 to 183.7 nm. The TEM images show asymmetrical sphere-like particles, with the particle size changing from 69.4 to 82.1 nm as a function of ‘x’. The hysteresis curves were recorded for x = 0.2–0.8 to understand the ferrimagnetic behavior. The saturation magnetization (Ms) varies unsystematically between 35.3 and 43.3 emu/g with ‘x’, while a high magnetic moment of 1.819 μB/f.u. is found at a high Co-content. The paramagnetic term (χ x 10−5) goes on increasing from 125 to 148 emu/g.Oe with ‘x’. The zero-field cooled (ZFC) and field cooled (FC) curves provide the decreasing trend of variation blocking temperature (TB) from 270 to 260 for x = 0.2–0.6, whilst for x = 0.8, it is increased to 280 K. The high real part of the permittivity of ∼ 12.42 and low imaginary part of the permittivity of ∼0.638 are recorded at 8 MHz for x = 0.2, indicting energy storage applications. The power law fit was applied to log σac-log ω plots and the dc-electrical conductivity was evaluated. The TG-DTG and DSC curves revealed mass loss and transition temperatures for x = 0.2–0.8 as a function of temperature.