The “colossal” magnetocaloric effect in Mn1−xFexAs: What are we really measuring?

Abstract

Recently, a so-called “colossal” magnetocaloric effect (MCE) was reported in Mn1−xFexAs [A. de Campos et al., Nat. Mater. 5, 802 (2006)]. However, the value of ΔS that was determined appears markedly overestimated since it results from the inadequate use of the Maxwell relation. Here, we report on recent measurements of ΔS in Mn1−xFexAs from which a correct MCE value is deduced by using the Clausius–Clapeyron equation. This result is asserted by careful use of the Maxwell relation.