Huge room temperature negative magneto capacitance in La0.7Pb0.3Mn0.4Fe0.6O3-δ and positive magneto capacitance in La0.7Pb0.3Mn0.4Ti0.6O3-δ

Abstract

In this study, we report room temperature negative magneto capacitance due to 60% Fe doping and positive magneto capacitance due to 60% Ti doping at Mn site in La0.7Pb0.3MnO3. We have studied the structural, mixed valence studies using synchrotron X-ray absorption spectroscopy (XAS), magnetic and magneto capacitance properties of La0.7Pb0.3Mn0.4Fe0.6O3-δ and La0.7Pb0.3Mn0.4Ti0.6O3-δ. La0.7Pb0.3Mn0.4Fe0.6O3-δ and La0.7Pb0.3Mn0.4Ti0.6O3-δ were synthesized by solid state method. The x-ray diffraction (XRD) patterns show (i) successful substitution of Fe and Ti at Mn site and (ii) change in lattice parameters of La0.7Pb0.3Mn0.4Fe0.6O3-δ and La0.7Pb0.3Mn0.4Ti0.6O3-δ. L edge absorption studies using synchrotron XAS show the presence of mixed valence states in these compositions. La0.7Pb0.3Mn0.4Fe0.6O3-δ show maximum ~64 % negative magneto capacitance at 500 gauss(G) magnetic field, ~60 % at 5kG magnetic field and -56 % at 10 kG magnetic field at 300 K. La0.7Pb0.3Mn0.4Fe0.6O3-δ show ~51% negative magneto capacitance at 15 kG magnetic field while La0.7Pb0.3Mn0.4Ti0.6O3-δ show ~ 12 % positive magneto capacitance at 15 kG magnetic field. Magneto capacitance values in these compositions at room temperature in accordance with the Maxwell Wagner effect, which was explained by Catalan et al. Interaction between Mn+3 and Mn+4 via oxygen atom in the lattice originates the local magnetic region in the middle of non magnetic regions which originated negative magneto capacitance while Ti doped samples show positive magneto capacitance due to the presence quantum interference and coulombic interaction effects. Presence of unpaired electrons in the d orbitals of Fe, Mn and Ti dictates the magneto capacitance properties of these materials. **