Polarization Switching and Photoinduced Dielectric and Ferroelectric Properties in YMnO₃/La_0.67Sr_0.33MnO₃ Heterostructure

YMnO 3 /La 0.67 Sr 0.33 MnO 3 heterostructure was fabricated on SrTiO 3 (110) substrate by pulse laser deposition technology. The photoinduced resistance is markedly decreased in the low temperature region (20–300 K), especially arresting at the T′ C of o-YMnO 3 (∼30 K), the T′ N of o-YMnO 3 (∼40 K), and the T N of h-YMnO 3 (∼80 K). The variance tendency of the dielectric constant anomaly near the T′ N of o-YMnO 3 progressively decreases as the frequency increases, while the anomaly near the T N of h-YMnO 3 is not observed in the same frequency region. Additionally, the dielectric constant is suppressed under photo excitation, and the variation increases with the rise in temperature and frequency. A distinct photoinduced suppression in the ferroelectric hysteresis loops is observed, maybe the trapping of photoinduced electrons to incur the reorientation of domain or increase the leakage current density. The obvious polarization switching in phase and amplitude images are observed when poling at ±8 V DC bias by the piezoresponse force microscopy technique at room temperature.