Exchange Interactions and Fluctuations in CeB6

We report measurements of the low-temperature specific heat of Ce${\mathrm{B}}_6$ and discuss their significance in the light of earlier studies of this compound. The large specific heat above the antiferromagnetic ordering at 2.31 K is interpreted with the aid of a decorated Ising model. This model permits us to combine exchange and crystal field interactions in a simplified, but exact, calculation of the thermodynamic properties of a magnetic system including the effects of fluctuations. The analysis gives independent support to the proposal by Nickerson and White that the exchange in the crystal field excited state is substantially stronger than the ground-state exchange in Ce${\mathrm{B}}_6$. We also comment on the possibility of extending such an analysis to other magnetic rare-earth hexaborides.