Novel MnP thin films with integrated thermoelectric and thermomagnetic functionalities for energy-efficient solid state refrigeration

Abstract

A novel magnetic cooling device (MCD) that comprises thermoelectric (TE) and magnetocaloric (MC) materials is proposed, partially based on the previous work [1]. A sandwich structure, as shown in Fig. 1, has a MC material (MCM) in the center and two TE materials at the outer parts. The presence of the TE materials in the MCD guides the heat flow direction and enhances heat pulsation. In this case, the usage of a TE material that combines large TE with small MC responses within a similar temperature region enhances not only magnetic flux density but also heat exchange efficiency. In this study, we demonstrate that MnP thin films with integrated TE and MC functionalities are an excellent candidate for the proposed MCD. The MnP films were grown on Si substrates at 300, 400 and 500°C [2], and both the MC and TE effects were investigated systematically. The 400 oC sample shows the optimal TE and MC responses. A large TE effect is observed in the temperature region 250 – 400 K. The large power factor of 24.06 μW m-1 K-2 is achieved at room temperature. In this temperature region, the film shows a small MC effect (~1.23 J/kgK at 5T) but a strong magnetic response that gives rise to the enhanced TE effect. These properties would enable the MCD to operate at high frequency.