Abstract
belongs to a new family of alloys, similar to MnAs, showing a magnetostructural first-order transition near room temperature with large latent heat and magnetocaloric effect (MCE). From isothermal magnetization, remarkable values of the entropy change have been reported, such as J/kg K at 290 K for the small field change of 1 T, or J/kg K for 5 T on a slightly different composition. Strangely, this last value almost doubles that obtained from the Clausius-Clapeyron equation. Therefore, a very detailed set of calorimetric determinations have been made including heat capacity by adiabatic and differential scanning calorimetry (DSC), and direct measurement of the heat absorbed on isothermal demagnetization for several magnetothermal histories of the sample. We found high values of J/kg K at 289.4 K for a field change of 7 T, for a sample previously cooled to a low temperature and then heated under magnetic field to the target temperature. This value is high but very far from previously reported data, which happened to be nonphysical but obtained from a very frequently used, but incorrect, experimental protocol to determine from magnetization, via the Maxwell relation. The spurious contribution has been analyzed and computed, explaining the nonphysical reported values. The strong thermal and magnetic hysteresis of 8.4 K and 8.3 T, respectively, make this alloy useless for magnetic refrigeration, but the results encourage searching for other derivatives with lower hysteresis which could have even higher .
- Received 3 January 2021
- Accepted 18 February 2021
- Corrected 26 March 2021
DOI:https://doi.org/10.1103/PhysRevB.103.104402
©2021 American Physical Society
Physics Subject Headings (PhySH)
Corrections
26 March 2021
Correction: The fourth sentence of the abstract and the second sentence of the first paragraph of Sec. II contained errors in wording and have been fixed. The last two column headings in Table I contained errors and have been fixed. New Reference [13] was added and subsequent references have been renumbered.