Effect of high spin Mn2+ /Mn3+ ions on microstructural, optical, magnetic and electrical properties of hydrothermally prepared Ni–Mg nanoferrites
Résumé
A nanoferrite series of composition Ni0.5−xMnxMg0.5Fe2O4 with x=0,0.1,0.2,0.3 and 0.4 has been prepared by a hydrothermal method. X-ray diffraction (XRD) confirmed the formation of cubic spinel structure. The average crystallite size is found to be in the range of 28–48 nm. The lattice parameter is found to increase linearly with an increase in Mn2+ content. Field Emission Scanning Electron Microscopy micrographs indicate that the samples have almost uniform sized crystallites with uniform grain growth. Fourier Transform Infrared (FTIR) Spectroscopy studies showed two absorption bands close to 603 and 400cm−1 for the tetrahedral and octahedral sites respectively. Saturation magnetization attained a maximum value of 34.15 emu/g at x=0.3 and then decreases for higher concentrations of Mn2+ ions. Activation energy for compositions Ni0.3Mn0.2Mg0.5Fe2O4 and Ni0.2Mn0.3Mg0.5Fe2O4 are found to be 0.371 eV and 0.471 eV, respectively. For composition Ni0.2Mn0.3Mg0.5Fe2O4, maximum value of observed density, minimum porosity, maximum value of saturation magnetization, maximum initial permeability and minimum value of coercivity is obtained. DC resistivity is found to be of the order of 108Ωcm. The obtained results have been explained based on possible mechanisms, models and theories.