Simple Set-Up for Adiabatic Measurements of Magnetocaloric Effect

Abstract

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.