  The glassy behavior observed in the pyrochlore magnet Y2Mo2O7, where the
magnetic Mo^{4+} ions interact predominantly via isotropic nearest neighbor
antiferromagnetic exchange, possibly with additional weak disorder, is a
distinct class of spin glass systems where frustration is mostly geometrical. A
model proposed to describe such a spin glass behavior is the Heisenberg model
on a pyrochlore lattice with random but strictly antiferromagnetic exchange
disorder. In this paper, we provide compelling numerical evidence from
extensive Monte Carlo simulations which show that the model exhibits a finite
temperature spin glass transition and thus is a realization of a spin glass
induced by random weak disorder from spin liquid. From our results, we are led
to suggest that the spin glass state of Y2Mo2O7 is driven by effective strong
disorder.
