Aldrich Materials Science, in partnership with the Ames Labratory, offers a series of materials exhibiting large conventional and giant magnetocaloric effects, which are suitable for magnetic refrigeration applications. The materials were developed at the Ames Laboratory U.S. Department of Energy (DOE) under support of the Office of Basic Energy Sciences, US. They are available as coarse powders or ingots (Table 1).
Table 1. Materials for Magnetic Refrigeration
|coarse powder, 99% trace metals basis||693510|
|coarse powder, 99% trace metals basis||693502|
|Gadolinium||ingot, 99.99% (REM)||691771|
Magnetic refrigeration is a cooling technology based on the magnetocaloric effect,1 i.e. the magneto-thermodynamic phenomenon resulting in reversible temperature changes in the magnetic material when exposed to a varying magnetic field.
When a magnetic material is exposed to a periodically changing magnetic field, its magnetic moments cyclically order and disorder, thus releasing and absorbing energy. Usually, the material releases energy if its magnetic moments become aligned upon the application of a magnetic field, and absorbs energy once the magnetic field is removed and the magnetic moments randomize.
The magnetocaloric effect becomes even more profound if the magnetic transitions are accompanied by structural changes. This occurs in Gd5(SixGe4-x)-type alloys2-4 (Figure 1), which demonstrate an exceptionally strong (giant) magnetocaloric effect. For a magnetic field change of 5 Tesla, the magnetocaloric effect in Gd5Si2Ge2 reaches 15 K near room temperature, which exceeds by 25 to 30% that observed in the best conventional material, i.e. metallic Gd.
Figure 1. Crystal structure changes in Gd5(SixGe4-x) alloys in a magnetic field, which are responsible for their giant magnetocaloric effect.
Thus, the magnetocaloric effect permits designing refrigeration systems that operate similarly to conventional CFC-, HFC-, CO2-, or ammonia-based refrigerators with the only difference being that in the traditional compression-expansion cycles are substituted by magnetization and demagnetization of a solid magnetic metal or alloy.
To view complete list of our metal based products please access our Interactive Periodic Table at sigma-aldrich.com/periodic.