We have studied magnetocaloric and elastocaloric properties of a Ni-Mn-Sn(Cu) metamagnetic shape-memory alloy undergoing a magneto-structural transition (martensitic type) close to room temperature. Changes of entropy have been induced by isothermally applying both mechanical (uniaxial stress) and magnetic fields. These entropy changes have been, respectively, estimated from dilatometric measurements giving the length of the sample as a function of temperature at selected applied forces and magnetic fields and from magnetization measurements as a function of temperature at selected applied magnetic fields. Our results indicate that the elastocaloric effect is conventional and occurs in two steps which reflect the interplay between the martensitic and the incipient magnetic transitions. By contrast, the magnetocaloric effect is inverse and occurs in a single step that encompasses the effect arising from both transitions.

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We present a cost-effective and robust set-up designed to measure directly the magnetic field-induced adiabatic temperature change. The system uses a piston to introduce/remove the sample to/from the magnetic field (μ0∆His up to 1.7T) created by an ordinary electromagnet. The temperature of the sample is controlled by a double pipe heat exchanger operating by the electrical heater and air flow circulation from a Dewar with liquid nitrogen to the sample holder assembly.We have measured the adiabatic temperature change, ΔTad, of two polycrystalline samples: Gd and Ni50Mn35In15Heusler alloy. At the second-order magnetic phase transitions (18oC for Gd and 42oC for Ni50Mn35In15), ΔTadunder μ0∆H=1.7T are 3.8±0.1oC for Gd and 1.9±0.1oC for Ni50Mn35In15. The Heusler alloy shows an inverse magnetocaloric effect: ΔTadis-1.5±0.1oC on cooling and-1.6±0.1oC on heating at the martensitic transformation temperatures of ~24oC and ~29oC, respectively.

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