An indirect magnetic approach for determining entropy change in first-order magnetocaloric materials

TL;DR

This paper introduces an improved method based on the Clausius-Clapeyron equation for accurately determining entropy change in first-order magnetocaloric materials, especially those with phase transitions, reducing measurement costs and errors.

Contribution

The authors develop a new indirect approach using the CC equation that outperforms Maxwell-relation methods in accuracy and cost-effectiveness for certain magnetocaloric materials.

Findings

The method agrees well with Maxwell-relation results for Ni-Mn-Sn alloys.

It reduces overestimation of entropy change in Ni-Co-Mn-In and MnAs systems.

The approach eliminates spurious spikes and lowers measurement costs.

Abstract

Taking into account the phase fraction during transition for the first-order magnetocaloric materials, an improved isothermal entropy change determination has been put forward based on the Clausius-Clapeyron (CC) equation. It was found that the isothermal entropy change value evaluated by our method is in excellent agreement with those determined from the Maxwell-relation (MR) for Ni-Mn-Sn Heusler alloys, which usually presents a weak field-induced phase transforming behavior. In comparison with MR, this method could give rise to a favorable result derived from few thermomagnetic measurements. More importantly, we can eliminate the isothermal entropy change overestimation derived from MR, which always exists in the cases of Ni-Co-Mn-In and MnAs systems with a prominent field-induced transition. These results confirmed that such a CC-equation-based method is quite practical and superior to the MR-based ones in eliminating the spurious spike and reducing measuring cost.