Optical-controlled magnon transport based on spin crossover switched molecular magnets

Molecule-based devices that combine the advantages of fast time response and extremely low manipulation/transmission energy consumption of light, as well as the non-volatile properties of magnetic storage, could potentially be the ideal choice for future information processing. The key to achieving this vision lies in the bridge between light and magnetism, which refers to the innovative magneto-optical functional materials. The discovery of molecular magnets with spin-crossover features provides a new inspiration for realizing magneto-optical fusion information technology. Here, we demonstrate that light can reversibly modulate the propagation of magnons in cyanide bridged alternating W(V)-Fe(II) coordination polymer chains, wherein the paramagnetic high-spin and diamagnetic low-spin states of Fe(II) ions can be interconverted by alternating 808- and 473-nm light irradiations. Our experiments exploit microwaves for spin injection and detection, revealing that characteristic signal peaks at 8.28-8.60 GHz can be modulated by alternating light irradiation. The experimental results relate this phenomenon to the difference in magnon excitation between different spin states resulting from photo-induced spin-state switching. This photo-modulated spin transport device, which exhibits the properties of nonvolatility and reproducibility, provides a revolutionary strategy for modulating magnons and paving the way for optically tunable, ultrafast, low-power, and organic-insulator-based spin-logic devices.