Full Electric Control of Exchange Bias

TLDR

The study reports a multiferroic field‑effect device that enables direct, bipolar electrical control of exchange bias and proposes a model explaining this control. The device uses a BiFeO₃ gate dielectric and a La₀.₇Sr₀.₃MnO₃ channel, with exchange bias modulated by ferroelectric poling that displaces Fe³⁺ ions relative to Mn ions, altering interfacial exchange interactions. Exchange bias can be reversibly switched between two stable, opposite‑polarity states by ferroelectric poling of BFO, without requiring field cooling, temperature cycling, or additional magnetic or electric fields.

Abstract

We report the creation of a multiferroic field effect device with a ${\mathrm{BiFeO}}_{3}$ (BFO) (antiferromagnetic-ferroelectric) gate dielectric and a ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ (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 ${\mathrm{Fe}}^{3+}$ in BFO relative to ${\mathrm{Mn}}^{3+/4+}$ in LSMO cause bipolar modulation.