Study of atomic motions in EuBa2Cu3O7-δ by Mössbauer and EXAFS spectroscopies

We report the results of 151Eu Mössbauer and Eu K-edge EXAFS measurements on samples of EuBa2Cu3O7-δ. In particular, the ratios between the Eu Debye-Waller factors along the c and ab-plane directions, were obtained from the Mössbauer spectra in the temperature range 10-300 K. From these ratios, we obtained the differences between the corresponding mean square displacements. Moreover the motions of the first four coordination shells of the europium with respect to the latter, for T = 30-300 K, were studied by means of EXAFS spectroscopy. Combining the results obtained with the two techniques, we construct a qualitative picture of the collective atomic motions. In particular, we identify a substructure in the unit cell, around the central ion, formed by atoms performing correlate large amplitude anharmonic oscillations. © 2001 Plenum Publishing Corporation.