STUDIES ON LOW-TEMPERATURE STRUCTURE OF INFINITE-LAYERED SUPERCONDUCTOR SR1-XLAXCUO2 ESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.12)

Low temperature structure was investigated on infinite-layered Sr1-xLa xCuO2 (0 less than or equal to x less than or equal to 0.12, La-IL) su perconductor by X-ray absorption fine structure (XAFS), X-ray diffract ion (XRD) and Raman spectroscopy. XAFS showed that Cu-O bond distance slightly expanded with lowering temperature down to 20 K, and the expa nsion was remarkable below T-c(onset) = 43 K. Tetragonal lattice param eters shrank with lowering temperature but the shrinkage of the a-para meter seemed to be almost saturated below T-c(onset). Resonance Raman peaks were observed at 151 cm(-1) and 304 cm(-1) in the La-doped sampl es, although the ideal IL structure should be Raman inactive. The peak intensities increased with lowering temperature. The variation may be related to the change observed with both XAFS and XRD in local struct ure with temperature. It is assumed that the CuO2 plane may buckle wit h shifting oxygen ion positions above and below the CuO2 plane, as rep orted in another electron-doped superconductor Nd2-xCexCuO4 (T'-214). (C) 1997 Elsevier Science B.V.