ADIABATIC DEMAGNETIZATION. Introduction. One way to cool a gas is as follows. First compress it isothermally. This means compress it in a vessel that. One of these techniques is Adiabatic Demagnetization Refrigeration (ADR). This technique takes advantage of the fact that the entropy of. Ex Cooling by adiabatic demagnetization. Submitted by: Zion Hazan and Yair Yifrach. The problem: Consider a system of N spins on a lattice at.
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Adiabatic demagnetizationprocess by which the removal of a magnetic field from certain materials serves to lower their temperature.
This procedure, proposed by chemists Peter Debye and William Francis Giauque independently,provides a means for cooling an already cold material at about 1 K to a small fraction of 1 K.
The mechanism involves a material in which some aspect of disorder of its constituent particles exists at 4 K xdiabatic below liquid helium temperatures. Under these conditions the dipoles occupy these levels equally, corresponding to being randomly oriented in space. When a magnetic field is applied, these levels become separated adiabatci i. If the magnetic field is applied while the paramagnetic salt is in contact with the liquid helium bath an isothermal process in which a constant temperature is maintainedmany more dipoles will become aligned, with a resultant transfer of thermal adiabatlc to the bath.
Magnetic Cooling: Adiabatic Demagnetization
If the magnetic field is decreased after contact with the bath has been removed, no heat can flow back in an adiabatic processand the sample will cool. Such cooling corresponds to the dipoles remaining trapped in the lower energy states i. Much lower temperatures can be attained by an analogous means called adiabatic nuclear demagnetization. This process relies on ordering aligning nuclear dipoles arising from nuclear spinswhich are at least 1, times smaller than those of atoms.
With this process, temperatures of the ordered nuclei as low as 16 microdegrees 0. We welcome suggested improvements to any of our articles.
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Learn More in these related Britannica articles: Magnetic fielda vector field in the neighbourhood of a magnet, electric current, or changing electric field, in which magnetic forces are observable. Magnetic fields such as that of Earth cause magnetic compass needles and other permanent magnets to line up in the direction of the field. Peter Debyephysical chemist whose investigations of dipole moments, X-rays, and light scattering in gases brought him the Nobel Prize for Chemistry.
After receiving a Ph. William Francis GiauqueCanadian-born American physical chemist and winner of the Nobel Prize for Chemistry in for his studies of the properties of matter at temperatures close to absolute zero.
After earning his Ph.
Cryogenicsproduction and application of low-temperature phenomena. Help us improve this article!
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Magnetic refrigeration – Wikipedia
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