Heat capacity of EuO near the Curie temperature

Precision measurements of the heat capacity Cₚ of the Heisenberg ferromagnet EuO near the Curie temperature Tc≈69.3 K are reported. The data are for 64≤T≤73 K. When they are analyzed in terms of pure-power-law singularities over the range 0.003≤|t|≡|1-TTc|≤0.07, they permit equal exponents α and α^' above and below the transition, and a continuous specific heat at Tc. They yield α=α^'=-0.044±0.01 and an amplitude ratio AA^'=1.22±0.06 when Cₚ is assumed to be continuous. Although these results are consistent with scaling predictions, they disagree with estimates based on renormalization-group calculations for isotropic ferromagnets with dipolar interactions. When, in addition to the leading power-law term, singular correction terms are also included in the analysis and Cₚ is assumed to be continous at Tc, one finds α=α^'=-0.10±0.05, AA^'=1.50±0.2, and a correction exponent x=0.56±0.2. These latter results are consistent with all theoretical predictions.