On entropy determination from magnetic and calorimetric experiments in conventional giant magnetocaloric materials
In this work, we discuss measurement protocols for the determination of the magnetic entropy change associated with first-order magneto-structural transitions from both magnetization and calorimetric experiments. The Cu-doped Ni2MnGa Heusler alloy with a first-order magneto-structural phase transition is used as a case study to illustrate how commonly-used magnetization measurement protocols result in spurious entropy evaluations. Two magnetization measurement protocols which allow for the accurate assessment of the magnetic entropy change across first-order magneto-structural transitions are presented. In addition, calorimetric measurements were performed to validate the results from the magnetization measurements. Self-consistent results between the magnetization and calorimetric measurements were obtained when the non-equilibrium thermodynamic state was carefully handled. Such methods could be applicable to other systems displaying giant magnetocaloric effects caused by first-order phase transitions with magnetic and thermal hysteresis.
Publication Source (Journal or Book title)
Journal of Applied Physics
Chen, J., Us Saleheen, A., Adams, P., Young, D., Ali, N., & Stadler, S. (2018). On entropy determination from magnetic and calorimetric experiments in conventional giant magnetocaloric materials. Journal of Applied Physics, 123 (14) https://doi.org/10.1063/1.5016858