Deterministic optical control of room temperature multiferroicity in BiFeO₃ thin films

Controlling ferroic orders (ferroelectricity, ferromagnetism and ferroelasticity) by optical methods is a significant challenge due to the large mismatch in energy scales between the order parameter coupling strengths and the incident photons. Here, we demonstrate an approach to manipulate multiple ferroic orders in an epitaxial mixed-phase BiFeO₃ thin film at ambient temperature via laser illumination. Phase-field simulations indicate that a light-driven flexoelectric effect allows the targeted formation of ordered domains. We also achieved precise sequential laser writing and erasure of different domain patterns, which demonstrates a deterministic optical control of multiferroicity at room temperature. As ferroic orders directly influence susceptibility and conductivity in complex materials, our results not only shed light on the optical control of multiple functionalities, but also suggest possible developments for optoelectronics and related applications.