Scientists at the Massachusetts Institute of Technology (MIT) have recently discovered that when exposed to a varying magnetic field, magnons can travel from one end of a magnet to the other, drawing away heat and producing a cooling effect. The researchers believe magnets could one day act as refrigerants in household refrigerators.

In ferromagnets, local magnetic moments rotate and align in various directions. At absolute zero, the alignment of magnetic moments generates the strongest magnetic force. As the temperature rises, more magnetic moments spin out of sync, causing the magnetic force to weaken. Magnons emerge alongside this temperature increase. As quasiparticles within magnets formed by the collective rotation of magnetic moments, magnons are also known as spinons.

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The research team built a model using common magnetic insulators and input existing material data into the new simulation. The results show that a gentle magnetic field gradient produces a slight cooling effect, which becomes far more pronounced at low temperatures.

Magnons share many similarities with electrons. Electrons carry electric charge and conduct heat simultaneously, moving under the influence of electric fields or temperature differences — a principle known as the thermoelectric effect. Scientists have long studied thermoelectric technologies, such as thermoelectric generators that convert heat directly into electricity and solid-state cooling systems with no moving parts. Similarly, magnons move in response to two driving forces: temperature gradients and magnetic fields.

The researchers expanded the Boltzmann transport equation, which describes electron motion in thermoelectrics, and derived two new equations to characterize magnon transport. These formulas can accurately predict the magnon cooling effect, which operates in a comparable way to thermoelectric cooling. When magnons are placed in a non-uniform magnetic field, they transport thermal energy across the magnet from one side to the other.

According to the Head of the Department of Mechanical Engineering at MIT, the earliest practical applications of magnon cooling will likely focus on research scenarios requiring wireless cooling at extremely low temperatures.“For now, initial applications will lie in cryogenic fields, such as cooling infrared detectors. However, further experiments are needed to verify the theory and identify high-performance materials. We hope these findings will drive follow‑up experimental research.”