Evidence of local structural order and spin-lattice coupling in the frustrated pyrochloreY2Ru2O7

We present an extended x-ray absorption fine structure study of the pyrochlore ${\mathrm{Y}}_{2}{\mathrm{Ru}}_{2}{\mathrm{O}}_{7}$ (8--298 K). We find evidence, on a local scale, of a significant magnetoelastic coupling at the N\'eel temperature ${T}_{\mathrm{N}}\ensuremath{\sim}77\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ pointed out by a huge Debye-Waller ${\ensuremath{\sigma}}^{2}$ factor deviation from a correlated temperature dependent Debye-like local order behavior plus a temperature independent static contribution. Moreover, we notice the occurrence of a potential local order-disorder structural phase transition at ${T}^{*}=150$ K. This anomalous behavior is consistent with the pyrochlore's predisposition towards structural disorder and with a strong spin-phonon correlation. Remarkably the low-temperature order competes with the tendency of magnetic frustration to induce a less symmetric local structure.