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 T_g∼22.5K. 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−T_g. For T<T_g low energy spin fluctuations are replaced by static antiferromagnetic short range order with a frozen staggered magnetization |⟨S⟩|/S≈0.67(2). Locally the frozen spin structure corresponds to four sublattice ordering with zero magnetization.