Direct optical visualization and field switching of magnetic chirality

Chirality, a property that describes an object that cannot be superimposed on its mirror image, has long been a highly interdisciplinary focus across the natural sciences. So far, chirality has been primarily understood in structural forms. However, structural chirality is challenging to manipulate. In quantum materials, chirality can emerge through novel quantum states, such as charge-density-wave (CDW) or helical spin textures. Magnetic chirality, which arises from helical spin arrangements, presents exciting opportunities for external control of chirality. On the other hand, the search for intrinsic magnetic topological materials has attracted considerable interest in the condensed matter community. EuIn₂As₂ has been proposed to host a topological Axion insulator state characterized by broken-helix magnetic order, making it an ideal platform to explore magnetic chirality in topological systems. Here, we directly visualize the magnetic chirality in helimagnet EuIn2As2 with optical scanning circular dichroism (CD) and second harmonic generation (SHG) microscopy. Through SHG anisotropy, we also confirm the presence of three additional distinct helimagnetic domains from broken-helix order. Furthermore, we achieve direct magnetic field switching of magnetic chirality, due to the locking between relativistic orbital magnetization and magnetic chirality in this system. Our findings open a new pathway for controlling magnetic chirality, holds great potential for future developments in spintronics.