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 × 105 erg cm−3 to 2.23 × 106 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 × 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.

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

Magnetic and structural properties of RE doped Co-ferrite (REåNd, Eu, and Gd) nano-particles synthesized by co-precipitation

Synthesis and characterization of gadolinium doped cobalt ferrite nanoparticles with enhanced adsorption capability for Congo Red

Magnetic and structural properties of nano sized Dy-doped cobalt ferrite synthesized by co-precipitation

https://iopscience.iop.org/article/10.1088/2043-6254/aa853a/pdf

Impact of grain size and structural changes on magnetic, dielectric, electrical, impedance and modulus spectroscopic characteristics of CoFe2O4 nanoparticles synthesized by honey mediated sol-gel combustion method

The superparamagnetic properties of the doped cobalt ferrite nanocrystals have been demonstrated. The significance of the sol–gel autocombustion method in yielding the as obtained doped cobalt ferrite oxide powder in the nano-range has been very well complemented with structural, dimensional and morphological analytical techniques such as X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), particle size analysis and Scanning Electron Microscopy (SEM). The lattice strain and lattice parameters have been calculated by making use of the Williamson–Hall extrapolation. The valence states of the metal ions and single phase formation of the polycrystalline oxides have been confirmed with the help of X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. The magnetic measurements M–H and M–T have been carried out demonstrating a change in the magnetic moment and a superparamagnetic–ferrimagnetic transition in the ferrite system. The influence of the distribution of the metal ions in the crystal lattice and the dimensions of the ferrite oxides on the resultant magnetic properties has been demonstrated. The contribution of the spin–orbit coupling generating from the Co2+ ions in the octahedral lattice towards higher magnetic anisotropy and hence the magnetic properties is investigated. The results provide an insight into the inter-relationship of the particle dimension, the spin–orbit coupling and the resulting superparamagnetic property.

A. V. Salker

Papers

Change in the magnetostructural properties of rare earth doped cobalt ferrites relative to the magnetic anisotropy