Impact of Gd3+ substitution on the structural, magnetic and electrical properties of cobalt ferrite nanoparticles

In this work, we have focused on the influence of Gd3+ substitution on the structural, magnetic and electrical properties of cobalt ferrite synthesized using a sol-gel auto-combustion method. The powder X-ray diffraction analysis reveals that the Gd-substituted cobalt ferrites crystallize in a single phase spinel structure for lower concentrations of Gd3+, while a trace of GdFeO3 appears as a minor phase for higher concentrations. Raman and Fourier transform infrared spectra confirm the formation of the spinel structure. Furthermore, Raman analysis shows that the inversion degree of cobalt ferrite decreases with Gd3+ doping. The field emission scanning electron microscopy images show that the substitution of small amounts of Gd3+ causes a considerable reduction of the grain size. Studies on the magnetic properties reveal that the coercivity of Gd-substituted cobalt ferrites enhances from 1265 Oe to 1635 Oe, the saturation magnetization decreases monotonically from 80 emu g(-1) to 53.8 emu g(-1) and the magnetocrystalline anisotropy constant increases from 5.8 x 10(5) erg cm(-3) to 2.23 x 10(6) erg cm(-3) at 300 K. The electrical properties show that the Gd3+ doped samples exhibit high dielectric constant (616 at 100 Hz) and ac conductivity (4.83 x 10(-5) S cm(-1) at 100 Hz) values at room temperature. The activation energy is found to decrease from 0.408 to 0.347 eV with the rise in Gd3+ content. The impedance study brings out the effect of the bulk grain and the grain boundary on the electrical resistance and capacitance of cobalt ferrite. Gd substitution and the nano-size of cobalt ferrite enhance the electrical and magnetic properties which could enable a higher memory storage capability.