Electrical transport, magnetic, and electronic structure studies ofMg0.95Mn0.05Fe2−2xTi2xO4 ± δ (0≤x≤0.5) ferrites

Abstract

We present structural, electrical transport, magnetic, and electronic structure studies ofMg0.95Mn0.05Fe2−2xTi2xO4 ferrite using x-ray diffraction, dielectric spectroscopy, DC magnetization and near edgex-ray absorption fine structure (NEXAFS) measurements. The x-ray diffractionstudy shows a structural transition from cubic to tetragonal with Ti substitution.The dielectric constant and DC conductivity increase with Ti substitution up tox = 0.2. However, with further increase of substitution both the dielectric constant and DC conductivitydecrease. This electrical behavior indicates that at low values of substitution, hopping betweenFe3+ 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 Kand the saturation magnetization decreases with increase in Ti substitution.The NEXAFS measurements have been carried out at O K-, Fe L-, Fe K-, andTi L-edges to investigate the chemical states and the electronic structure of theMg0.95Mn0.05Fe2−2xTi2xO4 (0≤x≤0.5) system at room temperature. The O K-edge spectra indicate that the Fe3d orbitals are considerably modified with the substitution of Ti ions. Atx≥0.3, a new spectralfeature appears (∼532 eV) due to the transitions from oxygen 2p to Ti 3d orbitals whichstarts dominating the pre-edge spectra of the system. Both FeL3,2- and Fe K-edge spectra indicate that ironFe3+ ions convert intoFe2+ with the substitutionof Ti ions. The Ti L3,2-edge NEXAFS spectra reveal that the Ti remains in the4+ state for all the samples. The observed experimental results have been explained on thebasis of dilution of the magnetic sublattice by Ti substitution, which provides a stronginterplay between electrical and magnetic properties along with their electronicstructure.