A Setup for Direct Measurement of the Adiabatic Temperature Change in Magnetocaloric Materials

In order to find a highly efficient, environmentally-friendly magnetic refrigerant, direct measurements of the adiabatic temperature change
$\Delta T_{\text {adb}}$
are required. Here, in this work, a simple setup for the
$\Delta T_{\text {adb}}$
measurement is presented. Using a permanent magnet Halbach array with a maximum magnetic field of 1.8 T and a rate of magnetic field change of 5 T/s, accurate determination of
$\Delta T_{\text {adb}}$
is possible in this system. The operating temperature range of the system is from 100 to 400 K, designed for the characterization of materials with potential for room temperature magnetic refrigeration applications. Using the setup,
$\Delta T_{\text {adb}}$
of a first-order and two second-order compounds have been studied. Results from the direct measurement for the first-order compound have been compared with
$\Delta T_{\text {adb}}$
calculated from the temperature and magnetic field-dependent specific heat data. By comparing results from direct and indirect measurements, it is concluded that for a reliable characterization of the magnetocaloric effect (MCE), direct measurement of
$\Delta T_{\text {adb}}$
should be adopted.