Compositional gradient induced enhancement of Dzyaloshinskii-Moriya interaction in Pt/Co/Ta heterostructures modulated by Pt-Co alloy intralayers

The Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange in magnetic structures with broken inversion symmetry. In magnetic heterostructures, the bulk DMI may coexist with the conventional interfacial DMI contributing to the chiral magnetic behavior of the system. Here, we report the enhancement of DMI in Pt/Co heterostructures wherein Pt-Co alloy intralayers with compositional gradients are sandwiched between Pt and Co. Due to the composition gradient-induced bulk magnetic asymmetry and the face-centered cubic (fcc) (111) multilayer crystal structure, the DMI shows a complex behavior attributed to both the interfacial (i-DMI) and bulk-like (b-DMI) contributions. While the b-DMI is defined by the presence of composition differences and structure symmetry, the i-DMI hosts the interfacial contributions in the multilayer structure. Our approach allows the creation of graded magnetic thin films, where the structural inversion symmetry is broken solely due to the predefined compositional gradient of an intralayer, thereby giving rise to an `all-interface-bulk' DMI with the controllable spatial distribution. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.