Acceleration of domain wall movement by photoirradiation in perovskite-type cobaltite

Abstract

Femtosecond reflection spectroscopy was performed on a perovskite-type cobalt oxide, namely, Pr${}_{0.5}$Ca${}_{0.5}$CoO${}_{3}$, that undergoes a photoinduced spin-state transition. After photoirradiation at 30 K, the time profile of the reflectance change shows a broad peak reflecting the propagation of the photodomain (about 60 Co sites per one photon). Analysis of the peak position indicates the sudden increase of the velocity of the propagation with increasing the excitation intensity. Such acceleration with increase in fluence originates from an abrupt sound velocity change driven by a cooperative photoinduced structural transition.