Impact of transition metal (Co and Mn) substitution on the structural and magnetic properties of BaFe12O19 nanoparticles towards permanent magnet application

Given the enormous and rising global need for permanent magnet supply, even minor enhancements to the magnetic characteristics and economic viability of permanent magnet materials could result in significant energy and financial savings. In this work, the experimental conditions were optimized in order to produce barium hexaferrite (BaFe12O19) substituted with transition elements (Co and Mn) through chemical co-precipitation method. Powder X-ray Diffraction (XRD), Transmission Electron Microscope (TEM) and Fourier Transform Infra-red (FTIR) were used to reveal the structure, morphology and vibrational spectrum of the sample. The site preference for cobalt and manganese was estimated using Rietveld refinement of the XRD spectrum. It is obvious that Co and Mn occupied two crystallographic inequivalent sites, 4f(2) and 4f(1) respectively. Investigation of magnetic properties (VSM) at room temperature showed that as Co and Mn concentrations increase, saturation magnetization and retentivity increase, but coercivity decreases. At higher substitution concentrations, the behavior is the inverse. The possible reasons for these behaviors were discussed. The close correlation between site selection by the dopant and magnetic properties is also demonstrated.