  The quantum spin ice model applied to Tb2Ti2O7 predicts that magnetic fields
applied along the [111] axis will induce a partial magnetization plateau [H. R.
Molavian and M. J. P. Gingras, J. Phys.: Condens. Matter 21, 172201 (2009)]. We
test this hypothesis using ac magnetic susceptibility and muon-spin relaxation
measurements, finding features at 15 and 65 mT agreeing with the predicted
boundaries of the magnetization plateau. This suggests that Tb2Ti2O7 is well
described by a quantum spin ice model with an effective exchange constant of
Jeff = 0.17(1) K.
