Influence of Bi3+-doping on the magnetic and Mössbauer properties of spinel cobalt ferrite

Abstract

The influence of Bi³⁺-doping on the magnetic and Mössbauer properties of cobalt ferrite (CoFe₂O₄), wherein the Fe³⁺ ions are replaced by the Bi³⁺ ions to form CoBi_xFe_2−xO₄ ferrites, where x = 0.0, 0.05, 0.1, 0.15 or 0.2, has been investigated. The structural and morphological properties of undoped and doped ferrites, synthesized chemically through a self-igniting sol–gel method, are initially screened using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy measurements. The changes in magnetic moment of ions, their coupling with neighboring ions and cation exchange interactions are confirmed from the Mössbauer spectroscopy analysis. The effect of Bi³⁺-doping on the magnetic properties of CoFe₂O₄ ferrite is examined from the vibrating sample magnetometry spectra. Saturation magnetization and coercivity values are increased initially and then decreased, as result of Bi³⁺-doping. The obtained results with improved saturation magnetization (from 26.36 to 44.96 emu g⁻¹), coercivity (from 1457 to 1863 Oe) and remanence magnetization (from 14.48 to 24.63 emu g⁻¹) on 0.1–0.15 mol Bi³⁺-doping of CoBi_xFe_2−xO₄ demonstrate the usefulness for magnetic recording and memory devices.