Extremely Fast Optical and Nonvolatile Control of Mixed‐Phase Multiferroic BiFeO3 via Instantaneous Strain Perturbation

Multiferroics—materials that exhibit coupled ferroic orders—are considered to be one of the most promising candidate material systems for next‐generation spintronics, memory, low‐power nanoelectronics and so on. To advance potential applications, approaches that lead to persistent and extremely fast functional property changes are in demand. Herein, it is revealed that the phase transition and the correlated ferroic orders in multiferroic BiFeO3 (BFO) can be modulated via illumination of single short/ultrashort light pulses. Heat transport simulations and ultrafast optical pump‐probe spectroscopy reveal that the transient strain induced by light pulses plays a key role in determining the persistent final states. Having identified the diffusionless phase transformation features via scanning transmission electron microscopy, sequential laser pulse illumination is further demonstrated to perform large‐area phase and domain manipulation in a deterministic way. The work contributes to all‐optical and rapid nonvolatile control of multiferroicity, offering different routes while designing novel optoelectronics. All‐optical manipulation of the complex phases and domain structures in multiferroic BiFeO3 thin films on ultrafast timescale is demonstrated by adoption of extremely short light pulses. The configuration of large‐area optically written domains can be controlled by tuning the competing elastic and electrostatic energies. These results offer a novel route for the development of all‐optical switchable devices and high‐speed multifunctional optoelectronics.