Magnets and light are everywhere and yet their combinations are not common at all. Light is the source of all life on Earth while magnets make everyday life much easier – they are the key components in washing machines, vacuum cleaners, electric vehicles, hard disk drives in our computers, even MRI scanners in hospitals. Moreover, the very sophisticated elements of synchrotron storage rings like undulators or wigglers incorporate magnets. Photomagnets – magnets responsive to light, on the other hand, remain completely unknown (internet search leads only to personalized fridge magnets with a choice of pictures/photos, hence – 'photomagnets'). Moreover, while the global permanent magnet market was worth 22.2 billion USD in 2023, the global photomagnet market was worth basically nothing (excluding the aforementioned 'fridge photomagnets'). Therefore, there is a lot of room for improvement and one of the long-term objectives of the proposed research is 'to bring the real photomagnets into the spotlight' and enable their way into home appliances or at least into sophisticated scientific equipment that would allow discovery of better materials in the future.
The terms 'photomagnetism' and 'photomagnetic effect', referring to the change of the magnetic moment in response to visible light in photomagnets, were coined by the pioneers in the field of molecular magnetism: Hashimoto, Miller, Verdaguer and Dei. Noteworthy, its discovery is a consequence of the seminal work of Hauser et al. on the light induced excited spin state trapping (LIESST) effect in octahedral iron(II) complexes showing spin crossover (SCO) behavior and the discovery of the first room temperature molecular magnets obtained via bottom-up approach. The term 'photomagnetic effect' applies to all types of magnetic systems responsive to light: diamagnetic, paramagnetic as well as magnetically ordered ones. It relies on the observation that absorption of a photon by a specific part of a molecular system (a photomagnetic chromophore) can lead to a series of physical events resulting in a spin state change. Construction of molecular materials based on photomagnetic chromophores will lead to photomagnets - compounds that get magnetized when exposed to visible light. Hence, the major objective of LUX-INVENTA is the design and synthesis of room-temperature photomagnets – paramagnetic compounds that upon exposure to visible light become reversibly magnetized.
Currently, photomagnets working at room temperature are unknown. Hence, their possible applications remain solely theoretical. However, one can easily think of the possible technologies based on photomagnets. One of the most appealing ones would be the construction of a motor that does not need electricity to run - only light. While this idea seems quite wild at the moment, it might come to fruition once suitable photomagnetic materials are discovered. Other concepts involve photomagnetic valves that could be operated completely remotely using visible light (e.g. lasers), in opposition to electromagnetic valves which require electrical contacts (physical connections). Finally, thin photomagnetic layers could be a perfect alternative in information storage devices based on conventional magnets, with the possibility of writing/reading data using the combination light and magnetic fields. The LUX-INVENTA research team aims to discover photmagnets working at room temperature. After achieving this extremely challenging goal, the possibility of constructing a proof-of-concept photomagnetic device will be investigated.
