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Layered-specific hole concentrations in Bi2Sr2(Y1-xCax)Cu2O8+d as probed by XANES spectroscopy and coulometric redox analysis

M. Karppinen·M. Kotiranta·T. Nakane·H. Yamauchi·S. C. Chang·R. S. Liu·J. M. Chen
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Abstract

Induction of holes not only in the superconductive CuO2 plane but also in the Bi2O2+d charge reservoir of the Bi2Sr2(Y1-xCax)Cu2O8+d superconductor upon CaII-for-YIII substitution is evidenced by means of two independent techniques, i.e., high-resolution x-ray-absorption near-edge structure (XANES) spectroscopy measurements and coulometric redox titrations. The absolute values derived for the CuO2-plane hole concentration from the Cu L2,3-edge XANES spectra are in good agreement with those obtained from the coulometric redox analysis. The CuO2-plane hole concentration is found to increase from 0.03 to 0.14 concomitantly with the increase in the BiO1+d/2-layer hole concentration from 0.00 to 0.13 as the Ca-substitution level, x, increases from 0 to 1. The threshold CuO2-plane hole concentration for the appearance of superconductivity is determined at 0.06, while the highest Tc is obtained at the hole concentration of 0.12. In the O K-edge XANES spectrum, the increases in the CuO2-plane and BiO1+d/2-layer hole concentrations with increasing x are seen as enhancement in the relative intensities of the pre-edge peaks at ~528.3 and \~530.5 eV, respectively.

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M. Karppinen, M. Kotiranta, T. Nakane, H. Yamauchi, S. C. Chang, R. S. Liu, J. M. Chen. 2003-02-24. Layered-specific hole concentrations in Bi2Sr2(Y1-xCax)Cu2O8+d as probed by XANES spectroscopy and coulometric redox analysis. https://doi.org/10.1103/physrevb.67.134522

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