Local structure of the charge ordered La0.5Ca0.5MnO3

Local lattice of the charge ordered La0.5Ca0.5MnO3 has been studied by temp erature dependent Mn K-edge x-ray absorption measurements, using fluorescen ce detection method, to explore how the local lattice distortions are assoc iated with the charge ordering in this system. The x-ray absorption near ed ge structure (XANES) reveals an abrupt change in the local MnO6 octahedral geometry, across the charge ordering temperature. The extended x-ray absorp tion fine structure (EXAFS) analysis shows largely distorted MnO6 octahedra with coexisting Q(3)-type and Q(2)-type of Jahn=Teller (JT) modes at low t emperature in the commensurate charge ordered phase. We find that small JT distortions persist also in the charge disordered phase at high temperature .