Tunable topological magnetism in superlattices of nonmagnetic B20 systems

TL;DR

This paper predicts and analyzes tunable topological magnetic textures, including skyrmions and antiskyrmions, in atomically thin B20 superlattices, revealing complex asymmetric Dzyaloshinskii-Moriya interactions and potential for experimental realization.

Contribution

It introduces a novel approach to engineer and predict diverse topological magnetic states in B20 multilayers through atomistic simulations and structural design.

Findings

Antiskyrmions, skyrmions, and Bloch skyrmions are predicted in different B20 multilayer configurations.

Skyrmion sizes range from 7 nm to 37 nm depending on the system.

Structural engineering enables stabilization of both FM and AFM skyrmions, including zero Hall effect variants.

Abstract

We predict topological magnetic properties of B20 systems, that are organized in atomically thin multilayers. In particular we focus on FeSi/CoSi and FeSi/FeGe superlattices with different number of layers and interface structure. We demonstrate that absence of long range magnetic order, previously observed in bulk FeSi and CoSi, is broken near the FeSi/CoSi interface, where a magnetic state with non-trivial topology appears. Using electronic structure calculations in combination with the magnetic force theorem, we calculate the Heisenberg and Dzyaloshinskii-Moriya (DM) interactions in these systems. With this information, we perform atomistic spin dynamics simulations at finite temperature and applied magnetic field for large supercells with up to $2\cdot10^6$ spins to capture the complexity of non-collinear textures induced by the DM interaction. The spin dynamics simulations predict the formation of antiskyrmions in a [001]-oriented FeSi/CoSi multilayer, intermediate skyrmions in a [111]-oriented FeSi/CoSi system and Bloch skyrmions in the FeSi/FeGe (001) system. The size of different types of skyrmions is found to vary between 7 nm and 37 nm. The varying topological magnetic texture in these systems can be attributed to the complex asymmetric structure of the DM micromagnetic matrix, which is different from previously known topological magnets. Furthermore, through structural engineering, we demonstrate that both FM and AFM skyrmions can be stabilized, where the latter are especially appealing for applications due to the zero skyrmion Hall effect. The proposed B20 multilayers show potential for further exploration and call for experimental confirmation.