Non-volatile nanosecond phase change in BiFeO₃ thin films induced by pulse laser

Nowadays, increasing technology interest has focused on the optical control of non-volatile functional units based on ferroic materials, especially those with ultrafast tunabilities. Despite the fact that various light sources can be used to alter the ferroelectricity and magnetization of ferromagnets via means of light, this usually requires low-temperature or high-energy flux to fulfill significant changes. In this work, we reveal nanosecond non-volatile phase alteration in multiferroic BiFeO₃ (BFO) thin films.
This approach utilizes the delicate combination of thermal effect and strain pulse triggered by pulsed laser illumination. Taking advantage of the low phase transition barrier in the mixed phase BFO, we successfully demonstrate an effective optical approach to alter the phase distribition and corresponding ferroic properties in BFO. The application of single laser pulse results in the preferred phase transition from mixed phase to tetragonal phase. The fast phase change is attributed to the martensitic phase transformation induced by laser pulse, as evidenced by HAADF-STEM. We further show that the changes results from laser illumination are reversible, demonstrating new pathways to control the ferroic systems in ultrafast time scale through optical stimulus.