Magnetothermal

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J. Appl. Phys. 107, 043907 (2010) doi:10.1063/1.3309769 (3 pages)

Cooling induced by parametric resonance in a magnetic quadrupole trap

Source: http://www.opticsinfobase.org/col/abstract.cfm?uri=col-6-2-87
Chinese Optics Letters, Vol. 6, Issue 2, pp. 87-89 (2008)
It is demonstrated experimentally that the anharmonic property of the quadrupole trap can be exploited to cool trapped atoms by modulating the trap potential anisotropically. This cooling effect arises from the energy-selective removal of the most energetic trapped atoms and the thermal equilibrium of the remaining atoms. The frequency dependences of the temperature and the fraction of the atoms left in the trap after the modulation are explored. It is also demonstrated that the cooling induced by parametric resonance can also increase the phase space density of the trapped atoms.


The maximum possible magnetocaloric ΔT effect

Source: http://jap.aip.org/resource/1/japiau/v107/i4/p043907_s1
The current boom of research activity in magnetocaloric materials science is fuelled by the expectation that new advanced refrigerants may be found whose ΔT will significantly surpass that of gadolinium (Gd) metal (2.6–2.9 K/T). Because of this expectation, the main effort in the field has been diverted from the important issues of refrigerator design to the routine characterization of magnetic materials. Estimating the maximum adiabatic temperature change that can be achieved in principle by applying a certain magnetic field, say 1 T, is a matter of priority. In this work the problem of maximum ΔT is approached from general principles. According to the most optimistic estimates, ΔT can never exceed ∼ 18 K/T, the more realistic upper limit lying somewhere in high single figures. We therefore deem it most unlikely that a refrigerant much better than Gd, in respect of the ΔT value, will ever be found.
© 2010 American Institute of Physics