THE DIMPLING IN THE CuO2 PLANES OF YBa2Cu3Ox (x=6.806–6.984, T=20–300K) MEASURED BY YTTRIUM EXAFS

Abstract The dimpling of the CuO2 planes (spacing between the O2,3 and Cu2 layers) in YBa2Cu3Ox has been measured as a function of oxygen concentration and temperature by yttrium X-ray extended-fine-structure spectroscopy (EXAFS). The relative variations of the dimpling with doping (x=6.806–6.984) and temperature (20–300K) are weak (within 0.05 A), and arise mainly from displacements of the Cu2 atoms off the O2,3 plane towards Ba. The dimpling appears to be connected with the transition from the underdoped to overdoped regimes at x=6.95, and with a characteristic temperature in the normal state, T*≃150K.