Observation of photoinduced phase transition in phase-separated Pr0.55 (Ca1-y Sry) 0.45 Mn O3 thin films via x-ray photoemission spectroscopy

Perovskite manganite thin films, Pr0.55 (Ca1-y Sry) 0.45 Mn O3, have been studied using x-ray photoemission spectroscopy in order to clarify the consequence of the competition between ferromagnetic metal (FM) and charge-orbital-ordered insulator (COOI). Films with y=0.40 undergo a uniform paramagnetic insulator to FM transition. On the other hand, in films with y=0.25, the composition near the bicritical point, phase separation of COOI and FM domains is indicated by the spectral change below 125 K. Interestingly, between 50 K and 70 K, the visible laser illumination transfers the COOI-like spectra obtained in cooling process to the FM-like spectra obtained in warming process. This indicates that the photoinduced insulator to metal transition is governed by the increase of the FM volume fraction and is deeply related to the phase separation between the FM and COOI states.