Investigation of the electrical and magnetic properties of Mn substituted magnetite

Abstract

Polycrystalline MnxFe3-xO4 (0.1≤x≤0.9) ferrites were prepared by the standard solid state reaction technique. The samples were sintered at various temperatures (1250ºC, 1300ºC and 1350ºC) in air for 5 hours. Structural and surface morphology were studied by Xray diffraction and optical microscopy respectively. The magnetic properties of these ferrites were characterized with high frequency (1 kHz-15 MHz) complex initial permeability. The effects of microstructure, composition and sintering temperatures on the complex initial permeability of MnxFe3-xO4 ferrites are discussed. A possible correlation of sintering temperature with grain size and density of the material is also discussed. Lattice parameter decreases with the increase of Mn+2 content for all compositions. The decrease in lattice parameter with increasing Mn+2 content can be explained on the basis of the ionic radii. The microstructural study shows that grain size increases with increasing Mn+2 content for a particular sintering temperature. Both the theoretical and experimental density of the samples increases and the corresponding porosity of the samples decreases with increasing of Mn+2content. The density of the polycrystalline MnxFe3-xO4 compositions increases as the sintering temperature increases from 1250ºC to 1300ºC and above 1300ºC the density decreases. On the other hand, porosity of the sample decreases with increasing of sintering temperature up to 1300ºC and above 1300ºC the porosity increases. The initial permeability value increases with increasing Mn+2 content, because the average grain size increases with increasing Mn+2 content for the polycrystalline MnxFe3-xO4 compositions. The real part of the initial permeability remains fairly constant in the frequency range up to some critical frequency characterized by the onset of resonance. At these frequencies, after a small rise, the curves drop rapidly. The relative quality factor (Q) is found to increase with increasing Mn+2content. The magnetization as a function of applied magnetic field, M(H) for various Polycrystalline MnxFe3-xO4 samples at room temperature (300K) were measured. DC electrical resistivities of the samples at room temperature as function of Mn+2 content were also measured.