Growth Dynamics of Photoinduced Phase Domain in Cyano-Complex Studied by Boundary Sensitive Raman Spectroscopy

Abstract

Rubidium manganese hexacyanoferrate exhibits charge transfer phase transition from high temperature phase to low temperature phase at 230 K. This phase transition can also be triggered by light irradiation resonantly inducing charge transfer from Mn to Fe. In the present study, boundary sensitive Raman spectroscopy was performed for Rb0.94Mn[Fe(CN)6]0.98·0.2H2O in both cases of photoinduced and thermal phase transition. Since the frequencies of C≡N stretching vibration modes are very sensitive to the valence states of the adjacent metal ions, we can quantify the distribution of not only high and low temperature phase but also boundary configurations from the observed spectra. We obtained the time evolution of the fraction ratios of the valence states from the observed peak areas. In the case of photoinduced situation, the boundary increases up to 15% when high temperature phase diminishes to 55% of the initial fraction. This is quite different from the result in thermal phase transition where the boundary is created only 0.8% at the same high temperature phase fraction value. We conclude that many small domains are preferably created in photoinduced phase transition since the ratio of boundary is large, while large domains grow in thermal phase transition.