Irreversible electrical manipulation of magnetization on BiFeO3-based heterostructures

We prepared several heterostructures, Co/Bi0.90La0.10FeO3 on surface oxidized Si or (111) SrTiO3 and NiFe/Bi0.90La0.10FeO3 on (001) SrTiO3 substrates using LaNiO3 as bottom electrode. With different strategies of voltage application, the exchange bias field HE decreased with increasing voltage irreversibly for all the heterostructures at room temperature. The chemical state at the NiFe/Bi0.90La0.10FeO3 interface was studied by X-ray photoelectron spectroscopy before and after the electrical manipulation. The oxidization of the metallic ferromagnetic layer at interface after the electrical manipulation has been confirmed, which might explain the irreversibility.