Evidence of local structural order and spin-lattice coupling in the frustrated pyrochlore Y2Ru2O7

We present an extended x-ray absorption fine structure study of the pyrochlore Y2Ru2O7 (8–298 K). We find evidence, on a local scale, of a significant magnetoelastic coupling at the Neel temperature TN ∼ 77 K pointed out by a huge Debye-Waller σ2 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.