Sm-incorporated CoCr₂O₄ nanoparticles: tunable structural, optical, and magnetic properties

In order to solve environmental challenges and fulfill the growing demand for renewable energy sources, researchers worldwide are looking for effective nanomaterials to cleanse wastewater and replace fossil fuels. In this study, doping of Sm³⁺ ions in nanocrystalline cobalt chromites and their effects on the structural, optical, and magnetic characteristics have been investigated thoroughly. Four Sm-doped nanosized cobalt chromites with a generic formula of CoSm_xCr_2-xO₄ (x = 0.0, 0.03, 0.06, and 0.09) were prepared using the conventional wet co-precipitation technique. Powder x-ray diffractograms were obtained to confirm the cubic spinel crystal structure formation. Average crystallite sizes were observed to reduce with increasing Sm percentage in CoCr₂O₄ nanoparticles. The mean particle sizes derived from HRTEM images also followed a similar trend. Indirect optical band gaps increased with increasing Sm content in the host nanosized chromites. Vibrational Raman spectra recorded at room temperature confirmed the lowering of crystal symmetry for higher Sm content chromite samples. The Néel temperature of doped chromite nanoparticles was noticed to reduce with increasing Sm concentration. A gradual increase of effective anisotropy constant at 5 K with increasing Sm dopants confirmed the presence of various surface effects in the doped chromite samples. The doped samples have various applications, including sensors, detectors, photocatalysis, solar cells, and hyperthermia.