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What is the magnetocaloric effect and what materials exhibit this effect the most?
Asked by: Tim Michnick
Some magnetic materials heat up when they are placed in a magnetic field and cool down when they are removed from a magnetic field. This is known as the magnetocaloric effect.
This effect was discovered by E. Warburg in 1881 in pure iron. The size of the effect has been around .5 to 2°C per Tesla change in magnetic field. One Tesla is about 20,000 times the earth's magnetic field.
Recently, alloys of gadolinium, germanium and silicon have produces a much larger effect size of 3 to 4°C per Tesla change. The general equation for this material is; Gd_5(Si_xGe_1-x)_4, where x=0.5.
Experimental refrigerators based on the magnetocaloric effect have been tested in laboratories using magnetic fields of around 5T produced by superconducting magnets. http://www.cfs.me.uvic.ca/PAGES/amr.html
Answered by: Scott Wilber, President, ComScire - Quantum World Corporation