Influence of cobalt substitution in CoFe2O4 nanoparticles on structural, morphological, cation distribution, optical and magnetic properties

This paper presents the first-time synthesis of CoFe <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow></mml:mrow> <mml:mrow><mml:mn>2</mml:mn> <mml:mo>-</mml:mo> <mml:mi>x</mml:mi></mml:mrow> </mml:msub> </mml:math> Co _<i>x</i> O₄ nanoparticles (where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) through hydrothermal methods utilizing metal chloride precursors. X-ray diffraction (XRD) analysis confirms the formation of a cubic spinel structure characterized by the Fd <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover><mml:mrow><mml:mn>3</mml:mn></mml:mrow> <mml:mrow><mml:mo>¯</mml:mo></mml:mrow> </mml:mover> </mml:math> m space group. Field Emission Scanning Electron Microscopy (FE-SEM) images reveal that the average grain size of the nanoparticles lies between 50 nm and 90 nm. Notably, the optical band gap of the Co³⁺-doped samples exhibits a gradual increase from 1.7 eV to 2.5 eV. Furthermore, a reduction in saturation magnetization was noted with increasing doping content at both 5 K and 300 K. The observed decrease in saturation magnetization in the doped samples can be attributed to the migration of Co²⁺ ions from the B site to the A site, as well as the substitution of Fe³⁺ ions with Co³⁺ ions in the B site. Additionally, the influence of annealing temperature on the structure, morphology, and magnetic properties of the nanoparticles was examined.