Magnetic transitions in dysprosium: A specific-heat study

The magnetic transitions of the heavy rare-earth metal dysprosium have been examined by specific-heat measurements using a small single crystal (0.6782 g) and a large polycrystalline sample (43.25 g). A value for the latent heat of 39.1±1.5 J ${\mathrm{mol}}^{\mathrm{-}1}$ is obtained at the discontinuous transition from ferromagnetism to helical antiferromagnetism, and a temperature hysteresis of 1.2±0.4 K is observed at this transition. The data around the continuous transition from helical antiferromagnetism to paramagnetism at the Néel temperature $T_N$=179.90±0.18 K have been analyzed in terms of the equation & &)+${\mathrm{B}}^{\pm }$+${\mathrm{D}}^{\pm }$t, where t=(T-$T_N$)/$T_N$. Agreement to within two standard errors was obtained for the critical parameters of the single-crystal and polycrystalline data. The value of the critical exponent α obtained from the data of the single crystal is 0.24±0.02, whereas that obtained from the data of the polycrystalline sample is 0.14±0.05. We find that the scaling law ${\alpha }^{+}$=${\alpha }^{\mathrm{-}}$ is valid for the dysprosium critical data. In order for the condition $B^{+}$=$B^{\mathrm{-}}$, predicted by theory, to be satisfied we found it necessary to include the confluent singular term in E in our fit. The values of α that we obtain are not close to the predictions of renormalization-group theory for magnetic systems with short-range exchange interactions.