Soft-x-ray absorption spectroscopy of Nd1+xBa2-xCu3O7+delta (x=0-0.6)
Journal
Physical Review B
Journal Volume
55
Journal Issue
5
Pages
3186-3191
Date Issued
1997
Author(s)
Abstract
O K-edge and Cu (Formula presented) -edge x-ray-absorption near-edge-structure spectra for the series of (Formula presented) compounds (x=0-0.6) were measured using a bulk-sensitive x-ray fluorescence yield technique. Near the O 1s edge, pre-edge peaks at ∼527.5 and ∼528.2 eV are ascribed to the excitations of O 1s electrons to O 2p holes located in the (Formula presented) ribbons and (Formula presented) planes, respectively. The peak at ∼528.2 eV decreases in intensity with increasing the Nd doping, indicating the filling of holes in the (Formula presented) planes by the substitution of (Formula presented) for (Formula presented) in the (Formula presented) system. For low levels of Nd doping, the holes are located mainly in the (Formula presented) planes. At higher Nd doping, the holes are located predominantly in the (Formula presented) ribbons. The depression in (Formula presented) for the (Formula presented) system correlates closely with the hole concentration in the (Formula presented) planes and the number of disrupted fourfold-coordinated Cu on the chain sites. The high-energy shoulders in the Cu (Formula presented) -edge absorption spectra arise from (Formula presented) L defected states to (Formula presented) L excited states, where L denotes the ligand hole on the (Formula presented) ribbons and (Formula presented) planes. With increasing the Nd doping, the shoulders shift to higher energy ∼0.3 eV from x=0 to 0.6. © 1997 The American Physical Society.
Type
journal article