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

• Main Authors: Luis M. Moreno-Ramírez, Antonio Delgado-Matarín, Jia Yan Law, Victorino FRANCO, Alejandro Conde, Anit K. Giri
• Format: Article
• Language: English
• Published: MDPI AG 2019-10-01
• Series: Metals
• Subjects: magnetocaloric materials; direct ∆<i>t_ad</i> measurement; nimnin heusler alloys
• Online Access: https://www.mdpi.com/2075-4701/9/11/1144
• ISSN: 2075-4701

In the present work, using Heusler Ni_49+xMn_36-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 ∆<i>T_ad</i> 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 ∆<i>T_ad</i> in the region close to its first order phase transition. The error in ∆<i>T_ad</i> is found to be dependent on the temperature step used, being up to ~40% underestimation, including a slight shift in its peak temperature.