White-Light-Controlled Magnetic and Ferroelectric Properties in Multiferroic BiFeO3 Square Nanosheets

Multiferroic materials exhibiting magnetism and ferroelectricity are promising multifunctional materials, especially for spin electronic applications. The magnetoelectric effect was observed in many multiferroic materials, which couples magnetism and ferroelecticity. However, until now, the coupling of light with magnetism and ferroelectricity in multiferroic materials has not been reported yet. Herein we report on the observation of the remarkable white-light-controlled ferromagnetism and ferroelectricity in multiferroic BiFeO3 nanosheets at room temperature (300 K). The relative white-light-induced reduction of the ferromagnetic polarization is about 30%, and the relative white-light-induced change of the ferroelectric polarization is more than 225%. Furthermore, the BiFeO3 nanosheets show substantial ferromagnetism (0.2 mu B/Fe) at room temperature (300 K). Our result presented in this paper opens a new route for multifunctionality where magnetic polarization and ferroelectric polarization can be controlled simultaneously by light and magnetic field and electric field.