Thermal properties and Ehrenfest relation in an ``ideal" spin glass.

In order to test whether the Ehrenfest relation is applicable to the spin glass ``transition,'' we report temperature-dependent heat capacity and thermal expansion measurements on an ``ideal'' spin glass material: single grain icosahedral Gd-Mg-Zn quasicrystal and its non-magnetic counterpart, Y-Mg-Zn. Spin-glass state related signatures are clearly seen in the Gd-Mg-Zn data sets. Directly measured pressure dependence of the freezing temperature in Gd-Mg-Zn is compared to its evaluation through the Ehrenfest relation.