Binding a Hopfion in Chiral Magnet Nanodisk

TL;DR

This paper demonstrates the creation and control of stable 3D topological hopfion spin textures in chiral magnet nanodisks, revealing new possibilities for 3D spintronics applications.

Contribution

It presents the first realization of a stable, zero-field hopfion in a chiral magnet nanodisk and explores its topological transitions with monopole-antimonopole pairs.

Findings

Stable hopfion with Q_H=1 realized in nanodisk.

Switching between hopfion and MAP states with magnetic field.

Topological transition involves MAP creation and preimage twisting.

Abstract

Hopfions are three-dimensional (3D) topological textures characterized by the integer Hopf invariant $Q_H$. Here, we present the realization of a zero--field, stable hopfion spin texture in a magnetic system consisting of a chiral magnet nanodisk sandwiched by two films with perpendicular magnetic anisotropy. The preimages of the spin texture and numerical calculations of $Q_H$ show that the hopfion has $Q_H=1$. Furthermore, another non-trivial state that includes a monopole--antimonopole pair (MAP) is also stabilized in this system. By applying an external magnetic field, hopfion and MAP states with the same polarization can be switched between each other. The topological transition between the hopfion and the MAP state involves a creation (annihilation) of the MAP and twist of the preimages. Our work paves the way to study non-trivial 3D topological spin textures and stimulates more investigations in the field of 3D spintronics.