Pressure-induced electron transfer in ferrimagnetic Prussian blue analogs

M\"ossbauer and magnetic susceptibility measurements were performed under pressure on three Prussian blue analogs, K0.1Co₄[Fe(CN)₆]2.7·18H₂O, K0.28Co₄[Fe(CN)₆]2.76·18H₂O, and Cs0.7Co₄[Fe(CN)₆]2.9·16H₂O. A pressure-induced electron transfer Co²⁺(S=3/2)-Fe³⁺(S=1/2)→Co³⁺(S=0)-Fe²⁺(S=0) was found. The ``scanning'' of the ligand field strength by applying an external hydrostatic pressure allows the exploration of the distribution of CoNₙO_6-n(0<~n<~6) configurations. It reveals a narrow distribution of configurations centered around the most probable CoN₄O₂ configuration in K0.1Co₄[Fe(CN)₆]2.7·18H₂O and a broad CoNₙO_6-n distribution in K0.28Co₄[Fe(CN)₆]2.76·18H₂O and Cs0.7Co₄[Fe(CN)₆]2.9·16H₂O. This evolution of site distribution caused by alkali doping, explored here for the first time, to our knowledge is shown to play an important role in the photoinduced magnetization process.