Electrical transport, magnetic, and electronic structure studies of Mg(0.95)Mn(0.05)Fe(2-2x)Ti2xO4 +/-delta (0 <= x <= 0.5) ferrites

Abstract

We present structural, electrical transport, magnetic, and electronic structure studies of Mg(0.95)Mn(0.05)Fe(2-2)xTi(2x)O(4) ferrite using x-ray diffraction, dielectric spectroscopy, DC magnetization and near edge x-ray absorption fine structure (NEXAFS) measurements. The x-ray diffraction study shows a structural transition from cubic to tetragonal with Ti substitution. The dielectric constant and DC conductivity increase with Ti substitution up to x = 0.2. However, with further increase of substitution both the dielectric constant and DC conductivity decrease. This electrical behavior indicates that at low values of substitution, hopping between Fe3+ and Fe2+ increases whereas at higher concentrations the total content of Fe ions decreases. It is observed that all the samples exhibit ferrimagnetic behavior at 300 K and the saturationmagnetization decreases with increase in Ti substitution. The NEXAFS measurements have been carried out at O K-, Fe L-, Fe K-, and Ti L- edges to investigate the chemical states and the electronic structure of the Mg0.95Mn0.05Fe2-2xTi2xO4 ( 0 <= x <= 0.5) system at room temperature. The O K- edge spectra indicate that the Fe 3d orbitals are considerably modified with the substitution of Ti ions. At x >= 0.3, a new spectral feature appears ( similar to 532 eV) due to the transitions from oxygen 2p to Ti 3d orbitals which starts dominating the pre-edge spectra of the system. Both Fe L-3,L-2- and Fe K-edge spectra indicate that iron Fe3+ ions convert into Fe2+ with the substitution of Ti ions. The Ti L-3,L-2- edge NEXAFS spectra reveal that the Ti remains in the 4+ state for all the samples. The observed experimental results have been explained on the basis of dilution of the magnetic sublattice by Ti substitution, which provides a strong interplay between electrical and magnetic properties along with their electronic structure.