EXAFS AND XANES STUDY ON RARE-EARTH CHROMITES OF Gd_1-xSr_xCrO₃

Abstract
EXAFS and XANES measurements are made for Gd_1-xSr_xCrO₃ system (x=0,0.2,0.5) at 60 K and 300 K for Sr K-edge and Gd L₃-edge respectively, and for Cr K-edge at 300 K to elucidate their oxygen defect structure and their electric conduction mechanism. It is found that the coordination number of oxygen around the Sr ion in Gd_0.5Sr_0.5-CrO₃ is extremely decreased at 300 K as compared with one of that compound at 60 K. Similar tendency is found in Gd_0.8Sr_0.2CrO₃. The result is consistent with that the threshold eneregy of Sr K-edge in Gd_0.5Sr_0.5CrO₃ at 300 K is shifted to low energy side as compared with one at 60 K. Similar tendency is also found in Gd_0.8Sr_0.2-CrO₃. These results imply that mobility of oxygen ion around Sr ion is increased with elevating temperature even in such low temperature region. Oxygen coordination numbers around Gd ions in Gd_1-xSr_xCrO₃ (x=0.2 and 0.5) are also found to be small as compared with one of GdCrO₃.