Direct measurements of the magnetocaloric effect in pulsed magnetic fields: The example of the Heusler alloy Ni$_{50}$Mn$_{35}$In$_{15}$

摘要

We have studied the magnetocaloric effect (MCE) in the shape-memory Heusleralloy Ni$_{50}$Mn$_{35}$In$_{15}$ by direct measurements in pulsed magneticfields up to 6 and 20 T. The results in 6 T are compared with data obtainedfrom heat-capacity experiments. We find a saturation of the inverse MCE,related to the first-order martensitic transition, with a maximum adiabatictemperature change of $\Delta T_{ad} = -7$ K at 250 K and a conventionalfield-dependent MCE near the second-order ferromagnetic transition in theaustenitic phase. The pulsed magnetic field data allow for an analysis of thetemperature response of the sample to the magnetic field on a time scale of$\sim 10$ to 100 ms which is on the order of typical operation frequencies (10to 100 Hz) of magnetocaloric cooling devices. Our results disclose that inshape-memory alloys the different contributions to the MCE and hysteresiseffects around the martensitic transition have to be carefully considered forfuture cooling applications.