Determination of the local structure in FeSe_0.25Te_0.75 single crystal by polarized EXAFS

A. Iadecola¹, B. Joseph¹, L. Simonelli², Y. Mizuguchi^3,4, Y. Takano^3,4 and N. L. Saini¹

¹ Dipartimento di Fisica, Università di Roma “La Sapienza” - P.le Aldo Moro 2, 00185 Roma, Italy, EU
² European Synchrotron Radiation Facility - 6 rue Jules Horowitz, BP 220, 38043 Grenoble Cedex 9, France, EU
³ National Institute for Materials Science - 1-2-1 Sengen, Tsukuba 305-0047, Japan
⁴ JST-TRIP - 1-2-1 Sengen, Tsukuba 305-0047, Japan

naurang.saini@roma1.infn.it

Received: 12 February 2010
Accepted: 15 June 2010

Abstract

Temperature-dependent polarized extended X-ray absorption fine-structure (EXAFS) measurements are made on the superconducting FeSe_0.25Te_0.75 single crystal. The Fe-Se bond length is found to be significantly shorter than the average crystallographic Fe-Se/Te distance, and almost equal to the one for the system without Te. On the other hand, the Fe-Te bond length is nearly equal to the one known for a binary FeTe system. This suggests that the Se and Te occupy distinct sites in the ternary FeSe_0.25Te_0.75, indicating the breaking of the average crystal symmetry with locally inhomogeneous atomic distribution.