Influence of Thermal and Magnetic History on Direct Δ<i>T_ad</i> Measurements of Ni_49+xMn_36−xIn₁₅ Heusler Alloys

Abstract

In the present work, using Heusler Ni49+xMn36-xIn15 (with x = 0 and 0.5) alloys, it is shown that the choice of the appropriate measurement protocol (erasing the prior state of the sample in between experiments) in ∆Tad first shot characterization is crucial for obtaining reliable results. Unlike indirect measurements, for which incorrect protocols produce overestimates of the characteristics of the material, erroneous direct measurements underestimate ∆Tad in the region close to its first order phase transition. The error in ∆Tad is found to be dependent on the temperature step used, being up to ~40% underestimation, including a slight shift in its peak temperature.

Keywords

• magnetocaloric materials
• direct ∆<i>t_ad</i> measurement
• nimnin heusler alloys