Determination of the magnetocaloric entropy change by field sweep using a heat flux setup

We report on a simple setup using a heat flux sensor adapted to a Quantum Design Physical Property Measurement System to determine the magnetocaloric entropy change (ΔS). The major differences for the existing setups are the simplicity of this assembly and the ease to obtain the isothermal entropy c...

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Bibliographic Details
Published in:Applied physics letters 2014-08, Vol.105 (7), p.74104
Main Authors: Monteiro, J. C. B., dos Reis, R. D., Mansanares, A. M., Gandra, F. G.
Format: Article
Language:English
Subjects:
Applied physics
CALORIMETRY
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
COOLING
ENTROPY
GADOLINIUM
GADOLINIUM COMPOUNDS
GERMANIUM COMPOUNDS
HEAT FLUX
Heat transfer
MAGNETIC PROPERTIES
REDUCTION
Refrigeration
SENSORS
SILICON COMPOUNDS
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Summary:We report on a simple setup using a heat flux sensor adapted to a Quantum Design Physical Property Measurement System to determine the magnetocaloric entropy change (ΔS). The major differences for the existing setups are the simplicity of this assembly and the ease to obtain the isothermal entropy change either by a field sweep or a temperature sweep process. We discuss the use of these two processes applied to Gd and Gd5Ge2Si2 samples. The results are compared to the temperature sweep measurements and they show the advantages of this setup and of the field sweep procedure. We found a significant reduction of ΔS and on the refrigerating cooling power (RCP) at low field changes in a field sweep process when the sample is not driven to the same initial state for each temperature. We show that the field sweep process without any measuring protocol is the only correct way to experimentally determine ΔS and RCP for a practical regenerative refrigerator.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4894004