Magnetic refrigeration: The promise and the problems

Magnetic refrigeration which uses the temperature and field dependence of the entropy of some magnetic materials to accomplish cooling was developed. The high efficiency of the magnetization and demagnetization process and the potential for excellent heat transfer between solids and fluids, magnetic refrigerators offers higher efficiency than existing gas cycle refrigerators. These devices give high reliability and low volume and mass per unit cooling power. The arguments for high efficiency and the problems that will need to be solved to achieve this goal are discussed.