Low temperature dynamic freezing and the fragility of ordering in   Tb2Sn2O7
  We have probed the low temperature magnetic behavior of the ordered spin ice material Tb2Sn2O7 through ac magnetic susceptibility measurements of both the pure material and samples with small percentages of Ti substituted on the Sn sublattice. We observe a clear signature for the previously reported ordering transition at TC = 850 mK, as well as evidence for dynamic freezing at temperatures well below TC, confirming the persistence of significant magnetic fluctuations deep in the spin-ordered regime. The long range ordering transition was completely suppressed with as little as 5% Ti for Sn substitution, and 10% Ti substitution resulted in a spin-glass-like spin freezing transition near 250 mK. The results demonstrate that the long range magnetic ordering is surprisingly fragile in this system. 
M. L. Dahlberg, M. J. Matthews, P. Jiramongkolchai, R. J. Cava, P.   Schiffer
cond-mat.str-el cond-mat.mtrl-sci