Thermal and Magnetic Field Switching in a Two‐Step Hysteretic MnIII Spin Crossover Compound Coupled to Symmetry Breakings

Abstract

AbstractA MnIII spin crossover complex with atypical two‐step hysteretic thermal switching at 74 K and 84 K shows rich structural–magnetic interplay and magnetic‐field‐induced spin state switching below 14 T with an onset below 5 T. The spin states, structures, and the nature of the phase transitions are elucidated via X‐ray and magnetization measurements. An unusual intermediate phase containing four individual sites, where are in a pure low spin state, is observed. The splitting of equivalent sites in the high temperature phase into four inequivalent sites is due to a structural reorganization involving a primary and a secondary symmetry‐breaking order parameter that induces a crystal system change from orthorhombic→monoclinic and a cell doubling. Further cooling leads to a reconstructive phase transition and a monoclinic low‐temperature phase with two inequivalent low‐spin sites. The coupling between the order parameters is identified in the framework of Landau theory.