Chiral Molecular Magnet Superstructures with Light Control.

Chiral magnets are crucial for magneto-optical coupling to advance spin-optoelectronics. Chirality breaks spatial inversion symmetry, while magnetism breaks time-reversal symmetry. However, understanding and controlling the interplay between chirality and magnetism remain fundamental challenges. Here we report chiral helical magnetic superstructures with spin tunability and the Faraday effect by circularly polarized photons. By controlling the supramolecular assembly of chiral molecules, we demonstrate the superstructure transition of molecular magnets from vortex to helical nanowire structures through circular dichroism and electron microscopy. The chiral magnets exhibit circularly polarized light controlled ferromagnetic magnetic resonance and magnetic anisotropy. The enhancement of the Faraday effect by chiral structures is comparable to the effect produced by a 3 kOe magnetic field. This approach shows potential for low-power magneto-optical devices, and additionally, it lays the groundwork for chiral light-related noncontact optical magnetics.