Strain-affected ferroelastic domain walls in RbMnFe charge-transfer materials undergoing collective Jahn–Teller distortion

Abstract

Many rubidium manganese hexacyanoferrate materials, with the general formula Rb_xMn[Fe(CN)₆]_(x+2)/3·zH₂O, exhibit diverse charge-transfer-based functionalities due to the bistability between a high temperature Mn^II(S = 5/2)Fe^III(S = 1/2) cubic phase and a low-temperature Mn^III(S = 2)Fe^II(S = 0) tetragonal phase. The collective Jahn–Teller distortion on the Mn sites is responsible for the cubic-to-tetragonal ferroelastic phase transition, which is associated with the appearance of ferroelastic domains. In this study, we use X-ray diffraction to reveal the coexistence of 3 types of ferroelastic tetragonal domains and estimate the spatial extension of the strain around the domain walls, which represents about 30% of the volume of the crystal.