https://doi.org/10.1140/epjb/e2004-00290-x
Local structure around Ce in the Nd2-xCexCuO4±δ superconductor probed by EXAFS
1
INSTM, C.S.T.E./CNR, and Dipartimento di Chimica Fisica, Università di
Pavia, Viale Taramelli 16, I 27100, Pavia, Italy
2
CNR Istituto Struttura della Materia, Via Fosso del Cavaliere 100, 00133
Roma, Italy
3
Istituto Nazionale di Fisica Nucleare & Dipartimento di Fisica,
Università di Roma III, Via della Vasca Navale 84, 00146 Roma, Italy
4
Dipartimento di Chimica Fisica ed Elettrochimica, Università di Milano,
via C. Golgi, 19, 20133 Milano, Italy
5
Istituto CNR di Scienze e Tecnologie Molecolari ISTM, via C. Golgi, 19,
20133 Milano, Italy
Corresponding author: a paolo.ghigna@unipv.it
Received:
30
October
2002
Revised:
19
February
2004
Published online:
30
September
2004
The local structure around the Ce substitutional defects has been
investigated by Ce and Nd K-edge EXAFS on Nd2-xCexCuO samples with different dopant concentrations (x = 0.05, 0.10, 0.15
and 0.20) and oxygen amounts.
The lattice distortion around the Ce
can be
described as a shrinkage of the oxygen cuboid along the z crystallographic
direction. Moreover, the CuO4 planes become corrugated. The lattice
distortion is well localized and is largely independent of temperature and
Ce and oxygen content.
EXAFS measurements made at the Nd-K edge indicate that the local
chemical environment of Nd is not distorted.
The difference electron density maps, obtained from low temperature single
crystal X-ray diffraction data, revealed three strong positive residuals
which have been ascribed to cerium (at 0, 0,
) and to two non
equivalent oxygen apical positions O3 (at 0, 0,
) and O4 (at 0,
0
). The electron population of O4 site, which is closer to
cerium (
Å), is 3-4 times the O3 one.
PACS: 61.10.Ht – X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc. / 74.72.Jt – Other cuprates, including Tl and Hg-based cuprates / 61.72.Ji – Point defects (vacancies, interstitials, color centers, etc.) and defect clusters
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2004