Influence of the materials magnetic state on the accurate determination of the magnetocaloric effect

¹ University of Applied Sciences of Western Switzerland, Institute of Thermal Sciences and Engineering, CH-1401 Yverdon-les-Bains, Switzerland
² Clean Cool Systems Company, C/O ADNV, place de la tannerie 1400 Yverdon-Les-Bains, Switzerland
³ Néel Institute, département MCMF, CNRS, Avenue des Martyrs 25, Grenoble, France

^a e-mail: mohamed.balli@heig-vd.ch

Abstract

In this paper, we report a detailed study of the magnetocaloric effect (MCE) in different first order magnetic transition (FOMT) materials with different situation of the magnetic state (magnetic order). For this purpose, R-Co₂, MnAs based compounds were considered in this study. The MCE is discussed in terms of Maxwell relation (MR) and Clausius-Clapeyron (C-C) equation. The deviation observed between both methods is discussed and analyzed. On the other hand, practically all the reported data of the MCE in the literature are associated to the applied external magnetic field and have not been corrected taking into account the demagnetization effect related to the materials shape. The obtained results demonstrate that this phenomenon can alter drastically the MCE values by cancelling out a large part of the external field, resulting in spurious values of the measured MCE. The effect of the demagnetization field on the magnetocaloric performances is also the subject of this paper.