Electric-field-induced charge-transfer phase transition: A promising approach toward electrically switchable devices

Much research has been directed toward the development of electrically switchable optical materials for applications in memory and display devices. Here we present experimental evidence for an electric-field-induced charge-transfer phase transition in two cyanometalate complexes: Rb 0.8Mn-[Fe(CN)6]0.93·1.62H2O and Co3[W(CN)8]2(pyrimidine) 4·6H2O, involving changes in their magnetic, optical, and electronic properties as well. Application of an electric field above a threshold value and within the thermal hysteresis region leads to a transition from the high- to the low-temperature phase in these compounds. A model is proposed to explain the main observations on the basis of a para-ferroelectric transition. Our observations suggest that this new concept of electrical switching, based on materials exhibiting charge-transfer phase transitions with large thermal hysteresis loops, may open up doors for novel electro-optical devices. © 2009 American Chemical Society.