Glassy Statics and Dynamics in the Chemically Ordered Pyrochlore Antiferromagnet Y2Mo2O7

Static and dynamic magnetic correlations in the geometrically frustrated pyrochlore antiferromagnet Y2Mo2O7 have been studied using neutron scattering. The material is chemically ordered but displays a spin-freezing transition at Tg∼22.5 K. We show that dynamic short range order develops below room temperature. Upon cooling the two-spin correlation length never exceeds 5 Å, yet the spin fluctuation rate vanishes in proportion to T-Tg. For T