Impedance spectroscopy of epitaxial multiferroic thin films

Abstract

Temperature dependent impedance spectroscopy enables the many contributions to the dielectric and resistive \nproperties of condensed matter to be deconvoluted and characterized separately. We have achieved this for \nmultiferroic epitaxial thin films of BiFeO3 BFO and BiMnO3 BMO, key examples of materials with strong \nmagnetoelectric coupling. We demonstrate that the true film capacitance of the epitaxial layers is similar to that \nof the electrode interface, making analysis of capacitance as a function of film thickness necessary to achieve \ndeconvolution. We modeled non-Debye impedance response using Gaussian distributions of relaxation times \nand reveal that conventional resistivity measurements on multiferroic layers may be dominated by interface \neffects. Thermally activated charge transport models yielded activation energies of 0.60±0.05 eV BFO and \n0.25±0.03 eV BMO, which is consistent with conduction dominated by oxygen vacancies BFO and electron \nhopping BMO. The intrinsic film dielectric constants were determined to be 320±75 BFO and \n450±100 BMO.