Large Lattice Responses in a Mixed‐Valence Prussian Blue Analogue Owing to Electronic and Spin Transitions Induced by X‐ray Irradiation

Illuminating phase changes: Absorption of X-ray photons induces reversible internal charge-transfer processes in the mixed-valence Mn/Fe cyanide Rb0.7MnII1.15[FeIII(CN)6]⋅2 H2O over a broad temperature range. Both continuous and abrupt phase transformations can be triggered (see scheme; HS=high spin, LS=low spin) and because the X-rays simultaneously probe the structural properties of the material, the resulting phase diagram can be elucidated in detail.