Low temperature specific heat of geometrically frustrated Gd$_2$Sn$_2$O$_7$

Previous measurements of the specific heat of Gd$_2$Sn$_2$O$_7$ showed a $T^2$ power law below a strongly first-order phase transition, though there was some indication of a deviation from this power law below 500 mK\footnote{P. Bonville \emph{et al.} J. Phys.: Cond. Mat. {\bf 15}, 7777 (2003).}. Theory has predicted that anisotropy due to the dipolar interaction leads to a gapped spin wave spectrum resulting in an exponential specific heat as $T$ approaches 0.\footnote{A. G. Del Maestro and M. J. P. Gingras, J. Phys.: Cond. Mat. {\bf 16}, 3339 (2004).} We will present specific heat measurements to below 100 mK. Preliminary results show a deviation from the $T^2$ law which supports the above theoretical model.