Compositional Gradient Induced Enhancement of Dzyaloshinskii–Moriya Interaction in Pt/Co/Ta Heterostructures Modulated by Pt–Co Alloy Intralayers

Abstract

The Dzyaloshinskii–Moriya interaction (DMI) is an antisymmetric exchange in magnetic structures with broken inversion symmetry. In magnetic heterostructures, the bulk DMI co-exists 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 multiple graded interfaces and the face-centered cubic (fcc) (111) structure symmetry, the DMI shows a complex behavior attributed to both interlayer (i-DMI) and intralayer or bulk (b-DMI) contributions. While the b-DMI is defined by the crystal symmetry only, the i-DMI depends on the intermixing degree of the Pt-Co graded alloy. Our approach allows creating 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.

Keywords: Pt-Co alloy layer, microstructure, Interface, Dzyaloshinskii-Moriya interaction