23-03-2017, 11:31 AM
Magnetic cooling is a cooling technology based on the magnetocaloric effect. This technique can be used to achieve extremely low temperatures, as well as the ranges used in common refrigerators. Compared to traditional gas compression refrigeration, magnetic refrigeration is safer, quieter, more compact, has greater cooling efficiency and is more environmentally friendly because it does not use harmful and harmful ozone gases. The effect was first observed by a French physicist P. Weiss and the Swiss physicist A. Piccard in 1917. The fundamental principle was suggested by P. Debye (1926) and W. Giauque (1927). The first functional magnetic refrigerators were built by several groups from 1933.
The magnetocaloric effect
The magneto-caloric effect (MCE, magnet and calorie) is a magneto-thermodynamic phenomenon in which a change in temperature of a suitable material is caused by the exposure of the material to a changing magnetic field. This is also known by low temperature physicists as adiabatic demagnetization. In that part of the cooling process, a decrease in the force of an externally applied magnetic field allows the magnetic domains of a magnetocaloric material to be disoriented from the magnetic field by the agitation of the thermal energy (phonons) present in the material. If the material is isolated so that no energy is allowed to re-emigrate to the material during this time (ie, an adiabatic process), the temperature decreases as the domains absorb the thermal energy for reorientation. Randomization of domains occurs similarly to the randomization to the curie temperature of a ferromagnetic material, except that the magnetic dipoles overcome a decreasing external magnetic field while the energy remains constant, rather than magnetic domains that are broken from ferromagnetism Internal as power is added.
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