Systematic Cu L-2,L-3-edge and OK-edge XANES spectroscopy study on the infinite-layer superconductor system, (Sr,La)CuO2
Journal
Solid State Communications
Journal Volume
147
Journal Issue
9-10
Pages
370-373
Date Issued
2008
Author(s)
Abstract
Our systematic O K-edge and Cu L2, 3-edge XANES study on the infinite-layer superconductor system, (Sr,La) CuO2, reveals both common and a little different features in the electronic structure with/from those reported for the other n-type copper-oxide superconductor system, (R, Ce)2 CuO4. The O K-edge features show no dependence of the La-substitution level in (Sr,La) CuO2 (in line with the observations made for (R, Ce)2 CuO4 upon Ce substitution). This indicates that in n-type copper-oxide superconductors the doped electrons are not driven to the O site with the resultant Fermi level being located at the bottom of the UHB. At the Cu L3-edge, upon electron-doping an additional absorption peak due to nominally monovalent Cu appears about 933.7 eV, and simultaneously the two peaks due to nominally divalent Cu about 931.4 and 936 eV are found to lose spectral weight. Here then the situation differs slightly from that observed for the (R, Ce)2 CuO4 system in which the latter peak (due to transitions to the 4 s orbital) remains unchanged. Based on the spectral features at the Cu L3-edge an accurate estimate is made for the average copper valence, V (Cu): a linear decrease of the V (Cu) value with increasing x is confirmed. Moreover, also revealed is that the highest Tc value and the largest superconductivity volume fraction correspond to V (Cu) = 1.90 in (Sr,La) CuO2 (in agreement with the case of (R, Ce)2 CuO4 with the optimum V (Cu) value about 1.88-1.89). © 2008 Elsevier Ltd. All rights reserved.
Type
journal article