Enhancement of magnetic properties of bismuth-substituted Mn-Mg-Cu-Zn ferrite prepared by sol-gel route

Microstructural, optical, and magnetic properties of Mn_0.15Mg_0.15Cu_0.2Zn_0.5Fe_2-xBi_xO₄ (x = 0, 0.015, 0.03, 0.045, 0.06, 0.075, 0.090) ferrite nanoparticles synthesized by sol-gel technique were investigated. Rietveld refinement of X-ray diffraction patterns of the samples indicates the formation of a cubic spinel structure with \({Fd}\bar{3}m\) $\mathit{Fd}\bar{3}m$ space group, which was also confirmed by Fourier transform infrared spectroscopy. The morphology of the samples was investigated by field-emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy coupled with FE-SEM. The optical bandgap increases from 2.01 to 2.42 eV by the Bi³⁺ substitution. Saturation magnetization increases by increased substitution of the Bi³⁺ cation from 32.12 emu/g for x = 0.0 to 37.63 emu/g for x = 0.075 and finally decreases to 33.98 emu/g for x = 0.090.