The crystal structure of the spin-glass pyrochlore, Y2Mo2O7

The crystal structure of the spin-glass material, Y2Mo2O7, has been determined from powder neutron diffraction data using profile (Rietveld) methods. The data are consistent with the fully ordered cubic pyrochlore structure, a0 = 10.230(1) Å with Y in 16d, Mo in 16c, O in 48f(x = 0.3382(1)), and O′ in 8b of Fd3m. Attempts to refine models with O′ disordered over the 32e sites or between the 8a and 8b sites resulted in convergence to the 8b positions. Derived YO and MoO distances are in excellent agreement with those found in isostructural materials giving indirect evidence for YMo ordering over the cation sites.