Optimal temperature range for determining magnetocaloric magnitudes from heat capacity

• Published in: Journal of physics. D, Applied physics Applied physics, 2016-12, Vol.49 (49), p.495001
• Main Authors: Moreno-Ramírez, L M, Blázquez, J S, Law, J Y, Franco, V, Conde, A
• Format: Article
• Language: English
• Subjects: adiabatic temperature change; heat capacity; magnetocaloric effect
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/49/49/495001

The determination of the magnetocaloric magnitudes (specific magnetic entropy change, ΔsM, and adiabatic temperature change, ΔTad) from heat capacity (cH) measurements requires measurements performed at very low temperatures (~0 K) or data extrapolation when the low temperature range is unavailable. In this work we analyze the influence on the calculated ΔsM and ΔTad of the usually employed linear extrapolation of cH from the initial measured temperature down to 0 K. Numerical simulations have been performed using the Brillouin equation of state, the Debye model and the Fermi electron statistics to reproduce the magnetic, lattice and electronic subsystems, respectively. It is demonstrated that it is not necessary to reach experimentally temperatures very close to 0 K due to the existence of certain starting temperatures of the experiments, the same for ΔsM and ΔTad, that minimize the error of the results. A procedure is proposed to obtain the experimental magnitudes of ΔsM and ΔTad with a minimum error from cH data limited in temperature. It has been successfully applied to a GdZn alloy and results are compared to those derived from magnetization measurements.