Magnetocaloric effect

The magnetocaloric effect (MCE, from magnet and calorie) is a scientific phenomenon in which certain materials warm up when a magnetic field is applied. The warming is due to changes in the internal state of the material, which releases heat. When the magnetic field is removed, the material returns to its original state, reabsorbing the heat, and returning to original temperature. This can be used to achieve refrigeration, by allowing the material to radiate away its heat while in the magnetized hot state. Removing the magnetism, the material then cools to below its original temperature.

The effect was first observed in 1881 by German physicist Emil Warburg, followed by French and Swiss physicists Pierre Weiss and Auguste Piccard in 1917. The fundamental principle was suggested by American chemists Peter Debye (1926) and William Giauque (1927). The first working magnetic refrigerators were constructed by several groups beginning in 1933. Magnetic refrigeration was the first method developed for cooling below about 0.3 K (the lowest temperature attainable before magnetic refrigeration, by pumping on 3
He vapors).

The magnetocaloric effect can be used to attain extremely low temperatures, as well as the ranges used in common refrigerators.

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