Observation of photoinduced phase transition in phase-separated Pr$_{0.55}$(Ca$_{1-y}$Sr$_{y}$)$_{0.45}$MnO$_3$ thin films via x-ray photoemission spectroscopy

TL;DR

This study uses x-ray photoemission spectroscopy to observe how laser illumination induces a phase transition from charge-orbital ordered insulator to ferromagnetic metal in phase-separated Pr$_{0.55}$(Ca$_{1-y}$Sr$_{y}$)$_{0.45}$MnO$_3$ thin films, revealing the role of phase separation.

Contribution

It demonstrates the photoinduced insulator-metal transition in phase-separated manganite thin films and links it to the increase of ferromagnetic phase volume, a novel insight into phase control.

Findings

Laser illumination induces a transition from COOI to FM spectra.

Phase separation is confirmed near the bicritical composition.

Photoinduced transition is temperature-dependent, occurring between 50 K and 70 K.

Abstract

Perovskite manganite thin films, $Pr_{0.55}(Ca_{1-y}Sr_y)_{0.45}MnO_3$, 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 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 IMT is governed by the increase of the FM volume fraction and is deeply related to the phase separation between the FM and COOI states.