Spin waves in bilayers of transition-metal dichalcogenides

TL;DR

This paper provides a theoretical analysis of spin wave spectra in bilayers of transition-metal dichalcogenides, considering various magnetic phases and interlayer couplings, relevant for future nanoelectronic and spintronic applications.

Contribution

It introduces a comprehensive theoretical model for spin waves in bilayer transition-metal dichalcogenides, including multiple magnetic phases and anisotropies, which was not previously detailed.

Findings

Spin wave spectra differ significantly between ferromagnetic and antiferromagnetic bilayers.

The model predicts distinct spin wave modes in different magnetic phases.

Interlayer coupling influences the stability and characteristics of spin waves.

Abstract

Van der Waals magnetic materials are currently of great interest as materials for applications in future ultrathin nanoelectronics and nanospintronics. Due to weak coupling between individual monolayers, these materials can be easily obtained in the monolayer and bilayer forms. The latter are of specific interest as they may be considered as natural two-dimensional spin valves. In this paper, we study theoretically spin waves in bilayers of transition metal dichalcogenides. The considerations are carried within the general spin wave theory based on effective spin Hamiltonian and Hollstein-Primakoff-Bogolubov transformation. The spin Hamiltonian includes intra-layer as well as inter-layer nearest-neighbour exchange interactions, easy-plane anisotropy, and additionally a weak in-plane easy-axis anisotropy. The bilayer systems consist of two ferromagnetic (in-plane magnetization) monolayers that are coupled either ferromagnetically or antiferromagnetically. In the latter case, we analyse the spin wave spectra in all magnetic phases, i.e. in the antiferromagnetic, spin-flop, and ferromagnetic ones.