Optical Manipulation of Multiferroic Phases in BiFeO ₃ Thin Films

ABSTRACT Employing light as a means of actively tuning material properties unlocks the potential for non‐invasive, remote, and macroscopic control over technology‐relevant functionalities. Here, we demonstrate optical control over multiferroic phases in prototypical magnetoelectric thin films, utilizing above‐bandgap UV light illumination. Taking advantage of the enhanced response at the strain‐driven morphotropic phase boundary, we show that by modifying the electrostatic boundary conditions with photoinduced charge carriers, the rhombohedral‐like (R‐like) phase of can be selectively suppressed within the tetragonal‐like (T‐like) phase matrix. Furthermore, the electronic origin of such an optical response permits a pronounced polarization‐dependent R‐to‐T‐phase conversion. Finally, using scanning nitrogen vacancy magnetometry, we correlate optically induced ferroelectric phase conversion with a change from uncompensated magnetic ordering to G‐type antiferromagnetic ordering. Our work thus presents a novel approach to writing multiferroic states, which is key to magnetoelectric oxide electronics.