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Photo-induced phase switching dynamics in RbMn[Fe(CN)6] probed by accumulation free mid-infrared spectroscopy



Photo-induced phase switching dynamics in rubidium manganese hexacyanoferrate was investigated by visible pump mid-infrared probe transmittance spectroscopy between 2000 and 2250 cm−1. We monitored the CN stretching vibration modes, which are sensitive to the valence states of the adjacent metal ions, to observe the transient changes of the valences. Accumulation free method was applied to this measurement to remove the persistent phase transition and maintain the initial state constant for every pump pulse. At low temperature, the sample in low temperature phase (LTP) is irradiated with 532 nm light to stimulate intervalence charge transfer (Fe2+ → Mn3+) band, and photoinduced high temperature phase (PI-HTP), whose properties are similar to that of HTP, is created. The PI-HTP is reversed to LT phase by irradiating with 400 nm light which stimulates ligand-to-metal charge transfer (CN → Fe3+) band. In the photoinduced phase transition (PIPT) process from PI-HTP to LTP, increase of the valence pairs corresponding to the phase boundary state resulting from the charge transfer, CN to Fe3+, was clearly observed. The transient change has a rising time of shorter than 1 ps and a decay time longer than 100 ps. In the reverse process i.e., LTP to PI-HTP, reduction of LTP and production of boundary state induced by the charge transfer, Fe2+ to Mn3+, were observed. These changes appeared within 1 ps and survived more than 100 ps.