Comparative XANES study on the two electron-doped high-T{sub c} superconductor systems, (Sr,La)CuO{sub 2} and (Nd,Ce){sub 2}CuO{sub 4}

Journal Article · Fri May 15 00:00:00 EDT 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.02.014· OSTI ID:21370401

Tanaka, Y ^[1]; Karppinen, M ^[1]; Chen, J M ^[2]; Liu, R S ^[3]; Yamauchi, H ^[1]

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1. Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan)
2. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China)
3. Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, ROC (China)

Here we employ high-quality samples of (Sr{sub 1-x}La{sub x})CuO{sub 2} and (Nd{sub 2-x}Ce{sub x})CuO{sub 4} and XANES spectroscopy at O-K, Cu-L{sub 2,3} and Ce-M{sub 4,5} edges to gain comprehensive understanding of the electronic structure and doping in n-type high-T{sub c} superconductors. Not only common but also slightly different features are revealed for the two systems. From O-K-edge spectra, the UHB is found essentially independent of the electron-doping level for both the systems, in line with our understanding that the doped electrons do not go to the O site in n-type copper-oxide superconductors. Another common observation is that the main Cu{sup II} peak at the Cu-L{sub 3} edge (due to transitions to the Cu{sup II}-3d orbitals) systematically decreases in intensity upon electron doping, hence verifying the fact that the doped electrons go to the Cu site. The difference then between the two systems is that in (Sr{sub 1-x}La{sub x})CuO{sub 2} the weaker Cu{sup II} peak due to transitions to the Cu{sup II}-4s orbital depends on the degree of doping. Moreover, it was found that with increasing x, electron density increases much faster in (Sr{sub 1-x}La{sub x})CuO{sub 2} than in (Nd{sub 2-x}Ce{sub x})CuO{sub 4}. This is a consequence of two phenomena: a tiny increase in oxygen content concomitant to the Ce{sup IV}-for-Nd{sup III} substitution and the somewhat lower Ce-valence value of +3.8 compared to the nominal tetravalent state. - Graphical abstract: High-quality samples with systematically varied substitution levels of the two electron-doped copper-oxide systems, (Sr{sub 1-x}La{sub x})CuO{sub 2} and (Nd{sub 2-x}Ce{sub x})CuO{sub 4}, have been synthesized and thoroughly characterized by means of XANES spectroscopy at O-K, Cu-L{sub 2,3} and Ce-M{sub 4,5} edges to gain comprehensive understanding of the electronic structure and doping in n-type high-T{sub c} superconductors. Not only common but also slightly different features are revealed for the two systems.

• OSTI ID: 21370401
• Journal Information: Journal of Solid State Chemistry, Vol. 182, Issue 5; Other Information: DOI: 10.1016/j.jssc.2009.02.014; PII: S0022-4596(09)00073-5; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
37 INORGANIC
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DOPED MATERIALS
ELECTRON DENSITY
ELECTRONIC STRUCTURE
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ELEMENTARY PARTICLES
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