Spin correlations in the geometrically frustrated pyrochlore Tb 2 Mo 2 O 7

We report neutron-scattering studies of the spin correlations of the geometrically frustrated pyrochlore ${\text{Tb}}_{2}{\text{Mo}}_{2}{\text{O}}_{7}$ using single-crystal samples. This material undergoes a spin-freezing transition below ${T}_{g}\ensuremath{\simeq}24\text{ }\text{K}$, similar to ${\text{Y}}_{2}{\text{Mo}}_{2}{\text{O}}_{7}$, and has little apparent chemical disorder. Diffuse elastic peaks are observed at low temperatures, indicating short-range ordering of the Tb moments in an arrangement where the Tb moments are slightly rotated from the preferred directions of the spin-ice structure. In addition, a $\stackrel{P\vec}{Q}$-independent signal is observed which likely originates from frozen but completely uncorrelated Tb moments. Inelastic measurements show the absence of sharp peaks due to crystal-field excitations. These data show how the physics of the Tb sublattice responds to the glassy behavior of the Mo sublattice with the associated effects of lattice disorder.