  The spin glass behavior of Y2Mo2O7 has puzzled physicists for nearly three
decades. Free of bulk disorder within the resolution of powder diffraction
methods, it is thought that this material is a rare realization of a spin glass
resulting from weak disorder such as bond disorder or local lattice
distortions. Here, we report on the single crystal growth of Y2Mo2O7. Using
neutron scattering, we present unique isotropic magnetic diffuse scattering
arising beneath the spin glass transition despite having a well-ordered
structure at the bulk level. Despite our attempts to model the diffuse
scattering using a computationally exhaustive search of a class of simple spin
Hamiltonians, we were unable to replicate the experimentally observed
energy-integrated (diffuse) neutron scattering. A T^2-temperature dependence in
the heat capacity and density functional theory calculations hint at
significant frozen degeneracy in both the spin and orbital degrees of freedom
resulting from spin-orbital coupling (Kugel-Khomskii type) and random
fluctuations in the Mo environment at the local level.
