EXPERIMENTAL RESULTS ON MAGNETIC AND THERMAL PROPERTIES OF EUROPIUM SULFIDE RELEVANT TO MAGNETIC REFRIGERATION

We report on an experimental programme aimed at testing magnetic and thermal properties of EuS that are relevant to the use of this material as magnetic refrigerant in the vicinity of its ferromagnetic ordering temperature, i.e. between 5 and 25 K. The programme included measurements of the specific heat at magnetic fields of up to 2.5 T, a static magnetization experiment and measurements of the thermal conductivity. All experiments were carried out on sintered samples. The results on specific heat were used to construct an entropy diagram which fully confirmed the theoretically predicted advantage of EuS over paramagnetic materials like gadolinium gallium garnet (GGG). The magnetization loop revealed negligible hysteresis. Finally, the results on specific heat and thermal conductivity were combined to give the thermal diffusivity which is an important parameter for the design of the core structure in magnetic refrigerators.