In-plane epitaxy strain tuning intralayer and interlayer magnetic couplings in CrSe2 and CrTe2 mono- and bi-layers

TL;DR

This study uses density-functional-theory calculations to explore how in-plane epitaxy strain affects magnetic interactions in CrSe2 and CrTe2 mono- and bi-layers, revealing strain-induced tunability of intra- and inter-layer magnetism.

Contribution

It provides detailed magnetic phase diagrams under epitaxy-strain and explains the strain effects on magnetic couplings in these layered materials, including practical validation with a graphene substrate.

Findings

Epitaxy-strain manipulates intra- and inter-layer magnetism.

Interlayer distance variation influences inter-layer magnetism.

Strain affects magnetic properties differently depending on in-plane magnetism.

Abstract

Mismatched lattice-constants at a van-der-Waals epitaxy interface often introduce in-plane strains to the lattice of the epitaxial layer, termed epitaxy-strain, where the strains do not follow the intra-layer Poisson's relation. Here, we presented the magnetic phase diagrams of the CrSe2 and CrTe2 mono- and bi-layers under epitaxy-strain up to 8 %, as predicted using density-functional-theory calculations. They show that the in-plane epitaxy-strain manipulates either the intra- or inter-layer magnetism of them. The in-plane strain varies the interlayer distance, defined using an inter-layer Poisson's ratio, which governs the inter-layer magnetism in two opposite ways depending on the in-plane magnetism. The tunability of the intra-layer magnetism is a result of competing intra-layer Cr-Cr super-exchange interactions. A graphene substrate was introduced to examine the validity of our diagrams in practice. Our work also gives a tentative explanation on the controversially reported magnetizations in CrSe2 and CrTe2 epitaxial mono- or bi-layers under epitaxy-strains.