Developments of magnetic refrigerants for cryogenic temperatures

Abstract

Magnetic refrigeration is a reliable cooling method capable of achieving temperatures below 1 K by employing magnetic materials and magnets. Recently, various cryogenic magnetic refrigerants, including rare-earth ions, have been discovered. The effectiveness of these refrigerants, assessed through specialized measurements below 2 K, relies on the properties of the 4f electrons in the rare-earth ions. In this review, the approach for studying cryogenic magnetic refrigerants is outlined, based on the thermodynamic measurements and the condensed-matter physics of the 4f electronic system aimed at identifying high-performance magnetic refrigerants.