Coexistence of the electric polarization and conductive current in the bismuth-neodymium ferrite garnet films

The Nd₁Bi₂Fe₅O₁₂/Nd₂Bi₁Fe₄Ga₁O₁₂ polycrystalline films on the glass substrate and the Nd_0.5Bi_2.5Fe₅O₁₂ epitaxial films on the single-crystal gadolinium gallium garnet substrate have been investigated by impedance and dielectric spectroscopy. The inductive contribution to the impedance and two relaxation channels related to ferroelectric domains and migration polarization have been established. The magnetocapacitance and magnetoimpedance have been determined. The conductive and polarization currents and the phase difference between them for the films of two types have been determined. The critical temperatures of the polarization disappearance and hysteresis I–V have been found. A model of the polarization caused by the piezoelectric effect and flexoelectric interaction has been proposed. I–V hysteresis is explained by the presence of ferroelectric domains near the interface and is associated with the hysteresis of the electric polarization.