Full electric control of exchange bias.

We report the creation of a multiferroic field effect device with a BiFeO(3) (BFO) (antiferromagnetic-ferroelectric) gate dielectric and a La(0.7)Sr(0.3)MnO(3) (LSMO) (ferromagnetic) conducting channel that exhibits direct, bipolar electrical control of exchange bias. We show that exchange bias is reversibly switched between two stable states with opposite exchange bias polarities upon ferroelectric poling of the BFO. No field cooling, temperature cycling, or additional applied magnetic or electric field beyond the initial BFO polarization is needed for this bipolar modulation effect. Based on these results and the current understanding of exchange bias, we propose a model to explain the control of exchange bias. In this model the coupled antiferromagnetic-ferroelectric order in BFO along with the modulation of interfacial exchange interactions due to ionic displacement of Fe(3+) in BFO relative to Mn(3+/4+) in LSMO cause bipolar modulation.