ALTERED SR ATOMIC ENVIRONMENT IN LA2-XSRXCUO4

The Sr local atomic environment in the high T-c superconductor La2-xSr xCuO4 was probed by polarized XAFS measurements at the Sr K-edge on or iented powder samples with x=0.075, 0.1 at T=20K. We confirmed that Sr indeed substitutes at the La site in this compound, but alters the fi rst neighbor oxygen environment. This was found by determining the loc ation of the neighboring metal atoms up to the fifth shell distances t hrough fitting the Sr XAFS, and comparing with La It-edge polarized XA FS in the same samples and with diffraction results. The significant d istortions in the immediate oxygen environment of the Sr atoms can be an important factor contributing to the mechanism of the structural an d high T-c phase transitions in these cuprates.