Origin of magnetic freezing in pyrochlore Y2Mo2O7

We investigated the nature of the spin-glass like phase transition in the geometrically frustrated pyrochlore lattices Y2Mo2O7 using the local probes nuclear and muon magnetic resonances, and the field-dependent long-range probes x-ray and neutron scatterings. The long-range probes indicated that Y2Mo2O7 does not undergo any global symmetry changes, even in a field of 6 T. In contrast, the local signal indicates a lattice distortion close to the critical temperature. The nuclei show at least two inequivalent Y sites, and the muons show sublinear line broadening as a function of moment size, over a wide temperature range. The conclusion from all the measurements is that even in high field, the distortion of Y2Mo2O7 takes place within the unit cell while its global cubic symmetry is preserved. Moreover, the muon result clearly indicates the presence of magnetoelastic coupling.