Magnetism and magnetocaloric effect of rare earth RET 2 X 2 compounds

Magnetic refrigeration (MR) technology is considered to be an energy-saving alternative to the commonly used gas compression/expressing refrigeration technology. Currently, searching or designing magnetic solids with an excellent magnetocaloric effect (MCE) that works at different temperature regions is one of the most important targets. Therefore, the investigation of magnetism and MCE of rare-earth-based compounds is a prominent topic in the field of refrigeration. Among them, the ternary rare-earth compounds of RET 2 X 2 ( T = 3d, 4d, or 5d transition elements; X = B, P, Si, and Ge) with a ThCr2Si2-type crystal structure have attracted considerable attention owing to their unique physical and chemical properties. In this study, the crystal structure, magnetism, and MCE of RE Mn2(Si, Ge)2, RE Ru2(Si, Ge)2, RE Co2B2 and related compounds are briefly reviewed. Some of these compounds show excellent magnetocaloric properties with potential application in the field of active cryogenic MR.