Magnetic transitions in dysprosium: A specific-heat study

Abstract

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 mol-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 N�el temperature TN=179.90�0.18 K have been analyzed in terms of the equation & &)+B�+D�t, where t=(T-TN)/TN. 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 ? 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 ?+=?- is valid for the dysprosium critical data. In order for the condition B+=B-, predicted by theory, to be satisfied we found it necessary to include the confluent singular term in E in our fit. The values of ? that we obtain are not close to the predictions of renormalization-group theory for magnetic systems with short-range exchange interactions.