Photo-induced charge-transfer phase transition of rubidium manganese hexacyanoferrate in ferromagnetic and paramagnetic states

Abstract

A charge transfer phase transition with thermal hysteresis loop is observed in a series of rubidium manganese hexacyanoferrates, RbMn[Fe(CN) 6] ( 1), Rb 0.88Mn[Fe(CN) 6] 0.96·0.6H 2O ( 2), and Rb 0.97Mn[Fe(CN) 6] 0.99·0.2H 2O ( 3). This phase transition is accompanied by a structural change from cubic (F4¯3m) to tetragonal (I4¯m2). Its high-temperature (HT) and low-temperature (LT) phases are composed of Mn II ( S = 2 / 5 ) NC – Fe III ( S = 1 / 2 ) and Mn III ( S = 2 ) – NC – Fe II ( S = 0 ) , respectively. The phase transition is caused by a metal-to-metal charge transfer from Mn II to Fe III and a Jahn–Teller distortion of the produced Mn III ion. At the ferromagnetic state in LT phase of 2, the photo-induced phase transition is observed, i.e., magnetization is quenched by the irradiation with only one shot of laser pulse. This phenomenon is caused by a photo-induced phase transition from the LT phase to the HT phase. In 3, optical switching between LT and HT phases at room temperature in paramagnetic region is observed.