Sequential Jahn_CTeller and tilting transitions in the mixed Ru Mn perovskite SrRu0.5Mn0.5O3

摘要

The temperature dependence of the structure of the mixed metal perovskite SrRu0.5Mn0.5O3 has beenstudied from room temperature to 800 C. Below 400 C, the structure is tetragonal in space groupI4/mcm. This structure is characterised by cooperative tilting of the (RuMn)O6 octahedra that also exhibita large JT type elongation. Heating reduces the magnitude of the tetragonal distortion and SrRu0.5Mn0.5O3undergoes two apparently continuous transitions. The first near 250 does not involve a change insymmetry but rather is due to orbital melting and the removal of the cooperative JT distortion of the(RuMn)O6 octahedra, and the second is associated with the removal of the cooperative tilting of theoctahedra, and results in an increase in symmetry to cubic in Pm3m.