The origin of persistent spin dynamics and residual entropy in the stuffed spin ice Ho2.3Ti1.7O7-δ

The so-called 'spin ices' form when exchange interactions, crystal fields, and dipolar interactions are in a delicate balance. This gives rise to a ground state which has a considerable amount of residual spin entropy, much like the proton entropy in water ice through the freezing transition. Recently, 'stuffed' spin ices have provided a means to probe how delicate a balance is needed to stabilize the disordered ground state. Surprisingly, it is found that an increase of the density of spins results in very little change in the residual entropy, which leads to the interesting idea that residual entropy states might be more common than once believed for magnetism. In this communication, we detail the crystal growth of stuffed spin ice Ho2.3Ti1.7O7-delta, and we complete neutron scattering experiments to observe how the spins order at low temperatures. It is found that even with this large perturbation, the system still has some key signatures of the spin ice state, but the spin dynamics is significantly altered. With this new data, an explanation emerges for the zero-point entropy in the stuffed spin ices.