Application of the Principle of Adiabatic Demagnetization

Application of the Principle of Adiabatic Demagnetization

The principle of cooling by adiabatic demagnetization was suggested by P. Debye (1926) and W. F. Giauque (1927). When a substance is placed in a strong magnetic field, the magnetic dipoles are oriented or ordered. If the substance is insulated and the magnetic field is removed, the magnetic dipoles return to a random arrangement. Since the system is insulated the energy necessary for the return to the random state is taken from the system itself.

Adiabatic demagnetization is a process of cooling. It occurs in magneto-caloric materials. The principle is that these materials heat up when placed in a magnetic field and cool down when removed from the magnetic field.

As a result the temperature falls. At ordinary temperatures the cooling effect of adiabatic demagnetization is not observed. But when the temperature is 1°K or less, the cooling effect becomes prominent. Salts of rare-earths, e.g. gadolinium, cerium and dysprosium, and ferric ammonium alum, potassium chrome alum etc. have been used in the cooling by adiabatic demagnetization process. Temperature as low as 0.0030 K has been achieved.

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