Oxygen-vacancy and charge hopping related dielectric relaxation and conduction process in orthorhombic Gd doped YFe0.6Mn0.4O3 multiferroics

The temperature dependent dielectric relaxation and conduction mechanism of multiferroic Y1−xGdxFe0.6Mn0.4O3 (0 ⩽ x ⩽ 0.8) systems have been investigated by dielectric measurements and impedance spectroscopy study in the temperature range of 150-550 K. We have observed that the charge carrier hopping (with activation energy of 0.18-0.4 eV) and doubly ionized oxygen vacancy VO (activation energy of 0.4-0.6 eV) are mainly responsible for conduction mechanism in the systems. Conducting charge-relaxation-mode interaction may be the plausible reason for high dielectric constant in the samples. The XPS analysis reveals that the valence states of the Mn and Fe ions are tuned between Mn3+/Mn4+ and Fe3+/Fe2+ states depending upon the change in oxygen vacancy with different Gd concentrations. The activation energy increases with increase in Gd content revealing the increased oxygen vacancy concentration with increasing Gd content in high temperature region. The relaxation process is dominated by the short range hopping of charge carriers resulting in a departure from ideal Debye-like behavior. The samples possess two different conduction mechanisms that have different activation energies above and below their spin reorientation transition temperature.