Soft-magnetic skyrmions induced by surface-state coupling in an intrinsic ferromagnetic topological insulator sandwich structure

TL;DR

This paper reports the first observation of skyrmions in an intrinsic magnetic topological insulator sandwich structure, where surface-state coupling stabilizes skyrmions, opening new possibilities for topological magnetic memory.

Contribution

It demonstrates the fabrication and observation of skyrmions in a novel ferromagnetic topological insulator sandwich structure with controlled surface-state coupling.

Findings

Skyrmions observed via topological Hall effect.

Spacer layer thickness controls skyrmion stabilization.

Skyrmions are 'soft magnetic' due to strong exchange interaction.

Abstract

A magnetic skyrmion induced on a ferromagnetic topological insulator (TI) is a real-space manifestation of the chiral spin texture in the momentum space, and can be a carrier for information processing by manipulating it in tailored structures. Here, we fabricate a sandwich structure containing two layers of a self-assembled ferromagnetic septuple-layer TI, Mn(Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{4}$ (MnBST), separated by quintuple layers of TI, (Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{3}$ (BST), and observe skyrmions through the topological Hall effect in an intrinsic magnetic topological insulator for the first time. The thickness of BST spacer layer is crucial in controlling the coupling between the gapped topological surface states in the two MnBST layers to stabilize the skyrmion formation. The homogeneous, highly-ordered arrangement of the Mn atoms in the septuple-layer MnBST leads to a strong exchange interaction therein, which makes the skyrmions "soft magnetic". This would open an avenue towards a topologically robust rewritable magnetic memory.