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

TL;DR

This study directly measures the magnetocaloric effect in a Heusler alloy using pulsed magnetic fields, revealing saturation behavior and the importance of considering hysteresis for cooling applications.

Contribution

First direct measurement of the magnetocaloric effect in Ni$_{50}$Mn$_{35}$In$_{15}$ using pulsed fields, analyzing dynamic response and hysteresis effects relevant for cooling devices.

Findings

Maximum adiabatic temperature change of -7 K at 250 K

Saturation of inverse MCE related to martensitic transition

Hysteresis effects significantly impact cooling performance

Abstract

We have studied the magnetocaloric effect (MCE) in the shape-memory Heusler alloy Ni$_{50}$Mn$_{35}$In$_{15}$ by direct measurements in pulsed magnetic fields up to 6 and 20 T. The results in 6 T are compared with data obtained from heat-capacity experiments. We find a saturation of the inverse MCE, related to the first-order martensitic transition, with a maximum adiabatic temperature change of $\Delta T_{ad} = -7$ K at 250 K and a conventional field-dependent MCE near the second-order ferromagnetic transition in the austenitic phase. The pulsed magnetic field data allow for an analysis of the temperature 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 (10 to 100 Hz) of magnetocaloric cooling devices. Our results disclose that in shape-memory alloys the different contributions to the MCE and hysteresis effects around the martensitic transition have to be carefully considered for future cooling applications.