Significance of Lanthanum Doping on Physical, Optical, Magnetic, and Dielectric Properties of CoAl2-xLaxO4 Nanoparticles

In the present work, the effects of La3+ substitution on structural, optical, dielectric, and magnetic properties of cobalt aluminates nanoparticles were investigated. (CoAl2-xLaxO4), in series 0.0 ≤ x ≤ 0.12, nanoparticles were successfully synthesized via co-precipitation method. X-ray powder diffraction was employed to verify the cubic spinel aluminate structure. Lattice parameter (a) was increased from 8.078 to 9.983 and X-ray density (x-ray) of the structure was increased from 4.489 to 4.532 with increasing the La3+ content. Transmission electron microscopy analysis showed homogenous formation of the nanoparticles in a spherical shape, while functional analysis via FTIR indicated the presence of two main absorption attributed to the spinel aluminate. Optical properties of cobalt aluminates nanoparticles were investigated from results of optical absorbance spectra. Moreover, the increase in La3+ content, is followed by an increase from 1.01eV to 1.60 eV in the optical energy gap Eopt and from 2.930 to 4.983 in the refractive index. This confirms the enhancement of density of the CoAl2O4 nanoparticles with rising La3+ content. Results show an increase in the ferromagnetic behavior (superparamagnetic) with addition of La+3 content which may be due to the formation of single domain particle of small particle size. The saturation magnetization increases from 0.736 to 2.314 emug-1 as the contents of La3+ increases in the spinal CoAl2O4.