Charge-Transfer-Induced Interfacial Exchange Coupling at the Co/BiFeO3 Interface

The interplay between ferroelectricity and magnetism in multiferroic materials is of great scientific and technological interest, allowing magnetic control of ferroelectric properties and electric control of magnetic properties through the magnetoelectric coupling from interfacial strain, exchange bias, or charge-transfer process. We report the charge transfer at the Co/BiFeO3 interface from which the interfacial exchange coupling is achieved with the formation of Fe2+. The x-ray linear dichroism and x-ray magnetic circular dichroism results reveal that the strain as well as the exchange coupling J(ex) in BiFeO3 (BFO) with periodic 109 degrees domains are stronger than that in BFO with 71 degrees domains, resulting in the higher coercive field of Co/BFO with 109 degrees domain samples. The possible electric field control of the charge-transfer process at the Co/BFO interface enables an alternative class of electrically controllable magnetization, exchange bias, and giant magnetoresistive response of spintronic devices.