Leakage through the conductive channels appearing at the grain boundaries of multiferroic gallium ferrite

Multiferroic materials having good magneto-electric coupling are of great interest due to their enormous variety of applications in the field of spintronic devices. Despite having good magneto-electric coupling and multiferroic properties, gallium ferrite (GaFeO₃) is plagued for having a very high leakage current compared to other multiferroic materials, which shadows the possibility of its application in device fabrication. The conduction mechanism behind this exceptionally high leakage current in GaFeO₃ is still not identified properly. Here, we have carefully investigated the variation of leakage conduction with the change in morphologies, especially at the grain boundaries due to heat treatment temperature during sample preparation. A connected conductive network is detected along the fused grain boundaries, which provides the pathway for the leakage electrons to propagate through the material. Interestingly, the conductive atomic force microscopy image shows that oxygen vacancies at the near grain boundaries produce poor conductive regions. Small polaron hopping could be an effective transport mechanism present in the conductive ridges at the grain boundaries. Therefore, modification of grain boundaries could produce more effective results for the reduction in leakage current of GaFeO₃. (paper)