TEMPERATURE-DEPENDENT EXAFS STUDY ON ORIENTED YBA2CU3O7-DELTA SUPERCONDUCTOR

The polarized Cu K-edge EXAFS measurements on oriented powder of YBa2C u3O7-delta (T-c = 93 K, 5 mu m grain size) are made as a function of t emperature from 20 to 300 K for the a-b plane and the c axis being par allel to the X-ray polarization vector epsilon. Here, we focus on the local structure of Cu-O bonds in the a-b planes. It is found that the average Cu-O (equatorial) distance and cumulants in the CuO4 square pl ane show anomalous behaviors around T-c.