Enhanced electrical conductivity at Fe₃O₄ grain boundaries

Clarifying how grain boundaries (GBs) in materials affect the electrical property is critical to the design and application of electronic nanodevices. A common physical scenario is that GBs have lower electrical conductivity than bulk materials due to intense electrons scattering. In this work, we demonstrate that Σ5 and Σ13 GBs in Fe₃O₄ bicrystal thin films exhibit substantially enhanced electrical conductivity compared to the grain interior based on nano- to macroscale electrical measurements. The atomic and electronic structures of the GBs have been systematically investigated by combining aberration-corrected scanning transmission electron microscopy and first-principles calculations. It has been revealed that the enhanced electrical conductivity at the Fe₃O₄ GBs arises from a half-metallic-to-metallic transition, which is attributed to the spin-up conduction channel provided by tetrahedrally coordinated Fe sublattice. This study reveals the atomistic mechanism of GB-enhanced conductivity, thereby deepening the understanding of GB electrical property.