Faculty of Physics
Magnetic Cooling
You can kill two birds with one stone if you use magnetic solid states to cool instead of the usual gases for condensing and re-expansion. Solid-state cooling avoids using gases that are harmful to the climate on the one hand, and on the other, has the magnetocaloric effect which is used for significantly higher effectiveness – it also assists with energy saving.
The idea behind this is to create spin moments in the solid state with a magnetic field. This heats up the solid states and this heat is emitted outwards in a conventional refrigerator. If you switch off the magnetic field, the spin moment randomly directs itself out once again, whereby the solid state cools. This is analogous to cooling the expanding gases in standard cooling processes.
A diverse material system for the application is La(FeSi)13, which has significant amounts of this type of magnetocaloric effect. This is based, as shown, on a complex interplay between magnetism, grid structure and electronic structure. In addition, members of the Wende research group, together with Dr. Markus Gruner and other scientists, have performed experiments and numerical calculations that deliver direct evidence of a strong link and the underlying microscopic mechanism. The results have been published in the prestigious ‘Physical Review Letters’ journal. The UDE researchers within the project 1599 ‘Ferroic Cooling’ of the German Research Association worked together with colleagues from TU Darmstadt on the project.