White-light-controlled ferromagnetic and ferroelectric properties of multiferroic single-crystalline BiFeO₃ nanoflowers at room temperature

Multiferroic materials, which synchronously exhibit magnetism and ferroelectricity, are promising multifunctional materials, especially for spin electronic applications. The magnetoelectric effect has been observed in many multiferroic materials and couples magnetism and ferroelectricity. However, until now, the coupling of light with magnetism and ferroelectricity in multiferroic materials has not been reported. Herein, we report the observation of remarkable white-light-controlled ferromagnetism and ferroelectricity in multiferroic single-crystalline BiFeO₃ nanoflowers at room temperature. The relative white-light-induced reduction in the ferromagnetic polarization is about 28% under white light illumination with a power density of 65 mW cm^-2 at the low magnetic field. At the same time, the relative white-light-induced enhancements of the saturated ferroelectric polarization and the remanent ferroelectric polarization are more than 200% under white light illumination with a power density of 65 mW cm^-2. Furthermore, the single-crystalline BiFeO₃ nanoflowers show substantial ferromagnetism (0.27 μB/Fe) at room temperature. Our results presented in this paper open a new route for multifunctionality where ferromagnetic polarization and ferroelectric polarization can be controlled simultaneously by light, a magnetic field and an electric field.