High-resolution neutron scattering study of Tb2Mo2O7: A geometrically frustrated spin glass

The low-temperature magnetic properties of Tb2Mo2O7 have been studied with bulk susceptibility measurements and with elastic and high-resolution inelastic neutron scattering. This system is a spin glass with a freezing temperature Tg∼25 K. A reverse Monte Carlo simulation of the neutron diffraction data shows weak ferromagnetic near-neighbor spatial correlations that do not extend beyond ≲10 Å. Neutron measurements of the spin dynamics reveal a slowing down with decreasing temperature without an anomaly at the glass transition. A low-lying Q-independent mode is seen at ℏω0∼0.28 meV. This dispersionless crystal electric field transition is measurable up to 60 K.