Specific-heat critical behavior of the Ising stacked triangular lattice antiferromagnet CsCoBr3

We have measured the specific-heat critical behavior of the Ising stacked triangular lattice antiferromagnet CsCoBr3, an excellent example of a fully frustrated three-dimensional second-order phase transition. For the transition near T=28 K, α=-0.025±0.004 and A+/A-=1.07±0.02 are consistent both with predicted d=3 XY criticality and Monte Carlo simulations which indicate critical behavior close to, but distinct from XY universality. No latent heat is observed, consistent with a second-order transition. No specific-heat peak is observed at the transitions reported at lower temperatures.