J. Phys. IV France 7 (1997) C2-1119-C2-1120
Temperature Dependent Re L3-Edge X-Ray Absorption Study of Crystalline Rhenium Trioxide ReO3A. Kuzmin1, J. Purans1, G. Dalba2, P. Fornasini2 and F. Rocca3
1 Institute of Solid State Physics, 8 Kengaraga str., 1063 Riga, Latvia
2 INFM, Università di Trento, 38050 Povo (Trento), Italy
3 Centro CNR-ITC di Fisica degli Stati Aggregati ed Impianto Ionico, 38050 Povo (Trento), Italy
X-ray absorption spectroscopy study of crystalline ReO3 was performed at the Re L3-edge in the temperature interval from 77 to 670 K. The analysis of both XANES and EXAFS regions shows that in ReO3, a progressive localization of the 5d states following the temperature increase is accompanied at T > 350 K by a distortion of the ReO6 octahedra. The distortion increases continuously up to the ReO3 decomposition temperature Td≈ 673 K and leads to the lowering of the rheniurn site symmetry from Oh(T≤350K) →D4h(T≈513K)→C4v(T≈668K). The observed distortion is explained by (i) the strong electron-phonon coupling of the 5d electron with the M3 and M'z3 phonons and (ii) the Jahn-Teller-like effect caused by the rhenium 5d1 electron which becomes localized at high temperature.
© EDP Sciences 1997