Observation of phase transition of cesium manganese hexacyanoferrates by X-ray absorption spectroscopy

Cesium manganese hexacyanoferrates exhibit an interesting phenomenon of temperature-induced phase transition accompanied by a variation in the magnetic susceptibility. We observed the variation in the electronic state of Mn during the phase transition by using X-ray absorption spectroscopy. The results of the analyses showed that the content ratio of FeII–CN–MnIII and FeIII–CN–MnII systematically varied during the phase transition. However, the ratio of FeII–CN–MnII remained constant at almost all temperatures. These results suggest that the charge transfer between Fe and Mn ions in the FeIII–CN–MnII or the FeII–CN–MnIII bond produces the phase transition.