![]() ![]() In recent years, scientists have investigated this effect for applications such as thermoelectric generators, which can be used to convert heat directly into electricity, or to deliver cooling without any moving parts. Electrons move in response to either an electric field or a temperature gradient - a phenomenon known as the thermoelectric effect. ![]() In many ways, magnons are similar to electrons, which can simultaneously carry electrical charge and conduct heat. As temperature increases, a magnet becomes weaker as more local magnetic moments spin away from the shared alignment a magnon population is created with this elevated temperature. At a temperature of absolute zero, the local magnetic moments align to produce the strongest possible magnetic force in a magnet. In a ferromagnet, the local magnetic moments can rotate and align in various directions. “These equations are pretty fundamental for magnon transport.” ![]() “People now have a new theoretical playground to study how magnons move under coexisting field and temperature gradients,” Liao says. Liao, along with graduate student Jiawei Zhou and Department of Mechanical Engineering head Gang Chen, have published a paper detailing the magnon cooling theory in Physical Review Letters. In theory, Liao says, such a magnetically driven refrigerator would require no moving parts, unlike conventional iceboxes that pump fluid through a set of pipes to keep things cool. “You can envision wireless cooling where you apply a magnetic field to a magnet one or two meters away to, say, cool your laptop.” “You can pump heat from one side to the other, so you can essentially use a magnet as a refrigerator,” says Bolin Liao, a graduate student in MIT’s Department of Mechanical Engineering. The theory describes the motion of magnons - quasi-particles in magnets that are collective rotations of magnetic moments, or “spins.” In addition to the magnetic moments, magnons also conduct heat from their equations, the MIT researchers found that when exposed to a magnetic field gradient, magnons may be driven to move from one end of a magnet to another, carrying heat with them and producing a cooling effect. The magnets cluttering the face of your refrigerator may one day be used as cooling agents, according to a new theory formulated by MIT researchers. ![]()
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