Influence of the starting temperature of calorimetric measurements on the accuracy of determined magnetocaloric effect

Moreno-Ramirez, L. M.; Franco, V.; Conde, A.; Neves Bez, H.; Mudryk, Y.; Pecharsky, V. K.

doi:10.1016/j.jmmm.2018.02.083

Title: Influence of the starting temperature of calorimetric measurements on the accuracy of determined magnetocaloric effect

Journal Article · Tue Feb 27 00:00:00 EST 2018 · Journal of Magnetism and Magnetic Materials

DOI:https://doi.org/10.1016/j.jmmm.2018.02.083· OSTI ID:1434310

Moreno-Ramirez, L. M. ^[1]; Franco, V. ^[1]; Conde, A. ^[1]; Neves Bez, H. ^[2]; Mudryk, Y. ^[2]; Pecharsky, V. K. ^[2]

Univ. de Sevilla, Sevilla (Spain)
Ames Lab. and Iowa State Univ., Ames, IA (United States)

Availability of a restricted heat capacity data range has a clear influence on the accuracy of calculated magnetocaloric effect, as confirmed by both numerical simulations and experimental measurements. Simulations using the Bean-Rodbell model show that, in general, the approximated magnetocaloric effect curves calculated using a linear extrapolation of the data starting from a selected temperature point down to zero kelvin deviate in a non-monotonic way from those correctly calculated by fully integrating the data from near zero temperatures. However, we discovered that a particular temperature range exists where the approximated magnetocaloric calculation provides the same result as the fully integrated one. These specific truncated intervals exist for both first and second order phase transitions and are the same for the adiabatic temperature change and magnetic entropy change curves. Here, the effect of this truncated integration in real samples was confirmed using heat capacity data of Gd metal and Gd₅Si₂Ge₂ compound measured from near zero temperatures.

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