Coexisting magnetic domains with distinct field-induced symmetries in the topological magnet EuIn₂As₂.

Hexagonal EuIn₂As₂ exhibits low-symmetry helical antiferromagnetic order that makes the compound a candidate stoichiometric magnetic topological-crystalline axion insulator with exotic surface states [1]. It is predicted that the surface states can be tuned by the direction and strength of an applied magnetic field [1]. We here report results from in-field single-crystal neutron diffraction experiments on EuIn₂As₂ with H||b, revealing successive field-induced changes to the magnetic order and discuss the implications to the system’s topology. With increasing field, magnetic domains displaying different symmetries are stabilized. Out of the three zero-field orthorhombic magnetic domains, one transitions to a canted A-type structure, while the other two both stabilize a fan-type structure. We find these domain related orders to coexist in our single crystal sample until full magnetic saturation is achieved at approximately 1 T. We predict that the presence of domains with differing magnetic symmetries has the potential to induce bulk topological edge modes at the magnetic domain boundaries.

[1] S. X. M. Riberolles et al., Nat Commun, 12, 999 (2021)