Origin of magnetic freezing in pyrochlore Y₂Mo₂O ₇

We investigated the nature of the spin-glass like phase transition in the geometrically frustrated pyrochlore lattices Y₂Mo₂O ₇ 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.