Conduction mechanism in BiFeO$_{3}$-CoFe$_{2}$O$_{4}$ columnar nanostructure

Multiferroic materials, which possess interaction between more than one ferroic ordering parameters, had attracted great scientific and technological interests. Among the bi-phase magneto-electric nanostructures, BiFeO$_{3}$-CoFe$_{2}$O$_{4}$ (BFO-CFO) is a model system with ferroelectricity and ferrimagnetism coupling to each other through stress mediation. In this study, we investigated the electron transport behavior and the leakage-current mechanism in high quality nano-composite BFO-CFO thin films. The CFO nanopillars were heteroepitaxially embedded in a BFO matrix grown on SrTiO$_{3}$ substrates. Macroscopic vertical transport result showed the interface limit model was the dominant mechanism of the large leakage. Local conduction in epitaxial BFO-CFO nanostructures was studied by conducting atomic force microscope (C-AFM) while the nature of band structure variation was demonstrated by scanning tunneling microscope (STM). This study provides a basic explanation of leakage mechanism in self-assembled composite material system.