Reducing crystal symmetry to generate out-of-plane Dzyaloshinskii-Moriya interaction

Abstract

The Dzyaloshinskii-Moriya antisymmetric exchange interaction (DMI) stabilises topological spin textures with promising future spintronics applications. According to crystal symmetry, the DMI can be categorized as four different types that favour different chiral textures. Unlike the other three extensively-investigated types, out-of-plane DMI, as the last type that favours in-plane chirality, remained missing so far. Here we apply point-group-dependent DMI matrix analysis to show that out-of-plane DMI exists under reduced crystal symmetry. Through strain and structure engineering, we show how Cs symmetry is realized in ultrathin magnets and observe the out-of-plane DMI stabilised in-plane chirality using spin-polarized electron microscopy. Our results show that extremely low out-of-plane DMI strengths at mu eV/atom are sufficient to stabilise topological spin textures, including merons and bimerons. We also demonstrate field-induced reversible control of the in-plane chirality and merons. Our findings open up untapped paths on topological magnetic textures and their potential applications. Antisymmetric exchange, or the Dzyaloshinskii-Moriya interaction, has been a topic intense study in recent years, due to its critical role in stabilizing topological spin-textures such as Skyrmions. Here, using a combination of point group analysis and spin polarized electron microscopy Niu et al demonstrate the existence of an out-of-plane Dzyaloshinskii-Moriya interaction, which was hitherto unobserved.