Unraveling the Complexity of the Dzyaloshinskii-Moriya Interaction in Layered Magnets: The Full Magnitude and Chirality Control.

Chirality is one of the inherent characteristics of some objects in nature. In magnetism, chiral magnetic textures can be formed in systems with broken inversion symmetry and due to an antisymmetric magnetic interaction, known as Dzyaloshinskii-Moriya interaction (DMI). Here, aiming for a fundamental understanding of this chiral interaction on the atomic scale, several synthetic layered structures composed of alternating atomic layers of 3d ferromagnetic metals epitaxially grown on the Ir(001) surface are designed. It is demonstrated both experimentally and theoretically that the atomistic DMI depends critically not only on the orbital occupancy of the interface magnetic layer but also on the sequence of the atomic layers. It is shown that even large atomistic DMI values can result in a small effective DMI, and conversely. Furthermore, the dependence of the effective DMI on the number of atomic layers deviates from a simple scaling law. These observations are attributed to the complexity of the electronic structure and the contributions of different orbitals to the hybridization and DMI. The results are anticipated to provide guidelines for achieving full control over both the chirality and the magnitude of the atomistic DMI in layered materials.