History dependence of directly observed magnetocaloric effects in (Mn, Fe)As

TL;DR

This study investigates the history dependence of the magnetocaloric effect in MnFeAs using direct calorimetric measurements, revealing no colossal effect and validating phase-fraction methods to correct Maxwell relation estimates.

Contribution

It provides direct calorimetric evidence that challenges previous reports of colossal MCE in MnFeAs and clarifies the role of phase fractions in the effect.

Findings

No colossal MCE observed in direct measurements

First order contribution scales linearly with phase fraction

Phase-fraction methods effectively correct Maxwell estimates

Abstract

We use a calorimetric technique operating in sweeping magnetic field to study the thermomagnetic history- dependence of the magnetocaloric effect (MCE) in Mn0.985Fe0.015As. We study the magnetization history for which a "colossal" MCE has been reported when inferred indirectly via a Maxwell relation. We observe no colossal effect in the direct calorimetric measurement. We further examine the impact of mixed-phase state on the MCE and show that the first order contribution scales linearly with the phase fraction. This validates various phase-fraction based methods developed to remove the colossal peak anomaly from Maxwell-based estimates.