Direct measurement of the magnetocaloric effect on micrometric Ni-Mn-(In,Sn) ribbons by the mirage effect under pulsed magnetic field

In this work we report on the direct measurement of magnetocaloric effect in a series of Ni-Mn-In-Sn micrometric thick ribbons performed with an innovative experimental technique based on the thermo-optical mirage effect. The adiabatic temperature change is induced in the sample by a pulsed magnetic field with an amplitude of 1 T and a period of a few milliseconds. The temperature change is collected by detecting the deflection of a laser beam grazing the sample surface. The very fast measurement time and the absence of a sensor in contact with the sample allow the direct measurement of the magnetocaloric effect on very thin samples with a thickness down to a few micrometers. The studied samples are Heusler alloys that show interesting values of magnetocaloric effect at the Curie transition of the austenitic phase near room temperature. This work demonstrates the possibility to directly measure the magnetocaloric response on thin samples to fast magnetic field changes with an amplitude really used in prototypes of magnetic cooling systems. The direct test of the magnetocaloric effect is fundamental for the development of refrigerant elements with a large heat-transfer coefficient and for the design of solid state micro devices for cooling and energy harvesting.