Materials that can be programmed to manage heat in precise ways mark a step forward in the search for better ways to handle thermal energy. A team at Osaka Metropolitan University has built a device that separates absorption from emission of thermal radiation, allowing directional control, on-off switching via magnetic fields and non-volatile memory that holds its state without constant energy input.
The core innovation lies in pairing magneto-optical materials with GST, a phase-change material. By layering a GST grating on a magneto-optical waveguide within a metagrating structure, the researchers produced strong nonreciprocal absorption even at near-normal incidence angles around three degrees. This breaks from the long-standing reciprocity principle, first formalised in Kirchhoff's law of thermal radiation in 1860, which normally demands symmetry between what a surface absorbs and what it emits.
The device can toggle its nonreciprocal behaviour on and off with a magnetic field. Once switched, the GST phase-change properties latch the configuration in place, much like non-volatile memory in electronics. Such retention without continuous power distinguishes the work from earlier approaches that often demanded steep angles or steady energy to maintain effect.
We made heat radiation behave in a smarter way. Achieving these capabilities in a working model could enable a new generation of efficient infrared emitters, thermal-energy devices, sensors and photonic memory technologies.
Shunsuke Murai, a researcher at Osaka Metropolitan University, described the result in those terms. The practical implications extend to infrared emitters, thermal management systems, sensors and photonic memory devices. Each rests on the ability to manipulate heat radiation with the same disciplined precision engineers already apply to electricity.
The paper detailing the device, titled Reconfigurable Giant Nonreciprocity at Near-Normal Incidence via Phase-Change Magneto-Optical Metagratings, appeared in Laser & Photonics Reviews on 25 June 2026. Lead authors include Ye Ming Qing, Yi Shen, Jun Wu, Shunsuke Murai, Zhaogang Dong and Koichi Okamoto. Osaka Metropolitan University followed with a press release on 7 July 2026.
Koichi Okamoto, professor at the same institution, framed the longer-term ambition clearly.
