We report heat capacity $\left(C_p\right)$ measurements on high-quality single crystals of hexagonal $\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_3$, a ferroelectric and frustrated triangular antiferromagnetic (AF) compound. The obtained values of the critical exponent $\alpha$ and amplitude ratio $A^{+}∕A^{-}$ for the AF transition are in good agreement with the standard three-dimensional Heisenberg universality class, and not with a chiral universality class associated with the 120° spin structure. The low-temperature $C_p$ deviation from the Debye law can be adequately fitted with a single Einstein contribution, indicating that there is no evidence of the anomalous magnetic contributions reported earlier. We also suggest that there is no intrinsic linear term in the low-temperature $C_p$. These results are consistent with conventional long-range AF ordering in $\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_3$.

• Received 14 May 2005

DOI:https://doi.org/10.1103/PhysRevB.72.064434