In most materials, the way heat is absorbed and the way it is emitted are inseparable. If a surface absorbs heat efficiently from a particular direction or wavelength, it also emits heat the same way. This long established principle, known as reciprocity, has made it difficult for scientists to independently control how thermal energy enters and leaves a material.
If those two processes could be separated, however, engineers could direct heat much more precisely. A material could absorb thermal energy from one direction while releasing it in another, potentially improving thermal management, energy conversion, infrared sensing, and thermal communication technologies.
To overcome this limitation, an international team led by Professor Koichi Okamoto and Dr. Shunsuke Murai of Osaka Metropolitan University's Graduate School of Engineering developed a new type of device using magneto-optical materials. These materials change the way they interact with light when exposed to a magnetic field, making it possible to alter their thermal behavior.
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