Specific heat of gadolinium garnets

Specific heat measurements on two different geometrically frustrated, Heisenberg, garnet lattices will be presented.  The specific heat of an isotopically pure, single crystal sample of Gd$_3$Ga$_5$O$_{12}$, or GGG, is found to be consistent with previous measurements of the specific heat of GGG \footnote{Schiffer et al. Phys. Rev. Lett. 74, 2379 (1995).} and shows no signs of a standard ordering anomaly despite sharp Bragg peaks that were seen in neutron diffraction experiments.  A first measurement of the specific heat of polycrystalline Gd$_3$Li$_2$Te$_3$O$_{12}$, in contrast, shows a sharp first-order phase transition at 240 mK.   We will discuss possible explanations for such diverse behavior in very similar systems.