Heat normally follows strict rules. A material that efficiently absorbs heat from a particular direction and wavelength will also emit heat the same way. This fundamental principle, known as reciprocity, has long prevented scientists from independently controlling how heat is absorbed and released.
Breaking that link could unlock an entirely new class of technologies. If materials could absorb heat from one direction while emitting it in another, engineers could steer thermal energy with unprecedented precision, leading to advances in thermal management, energy conversion, infrared sensing, and thermal communication.
To make that possible, an international research team led by Professor Koichi Okamoto and Dr. Shunsuke Murai of Osaka Metropolitan University’s Graduate School of Engineering turned to magneto-optical materials. These materials change the way they interact with light when exposed to a magnetic field.
The researchers paired a magneto-optical material with a phase change material known as GST to create a device that can control the direction of thermal radiation. The device can also switch this behavior on or off and retain its selected state even after power is removed, allowing heat to be programmed much like data stored in a microchip.
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