An EXAFS study of RuSr2GdCu2O8: Evidence of magnetoelastic coupling

The EXAFS spectrum of two samples of RuSr2GdCu2O8 prepared by means of slightly different procedures was measured in the temperature range from 10 up to 300 K on the K-edge of Cu. Both the basal and the apical Cu-O distances are not influenced by the magnetic and the superconducting transitions. Moreover the temperature dependence of the Debye-Waller factors of the R(Cu-Obasal) distance for both samples is in agreement with the Debye model for thermal disorder. On the contrary, σ2(Cu-Oapical) shows a clear peak around the magnetic transition. This effect is attributed to magnetoelastic coupling.