Evolution of interlayer and intralayer magnetism in three atomically thin chromium trihalides

TL;DR

This study investigates how interlayer and intralayer magnetism evolve in three atomically thin chromium trihalides, revealing systematic changes in magnetic properties and extending 2D magnetism understanding across different spin classes.

Contribution

It provides a comprehensive analysis of magnetic evolution in CrI3, CrBr3, and CrCl3, introducing a unified spin Hamiltonian and demonstrating ferromagnetism stabilization in monolayer CrBr3.

Findings

Interlayer magnetic ordering varies systematically with halogen atom.

A simple spin Hamiltonian describes all three chromium trihalides.

Ferromagnetism persists down to monolayer CrBr3 with high transition temperature.

Abstract

We conduct a comprehensive study of three different magnetic semiconductors, CrI$_3$, CrBr$_3$, and CrCl$_3$, by incorporating both few- and bi-layer samples in van der Waals tunnel junctions. We find that the interlayer magnetic ordering, exchange gap, magnetic anisotropy, as well as magnon excitations evolve systematically with changing halogen atom. By fitting to a spin wave theory that accounts for nearest neighbor exchange interactions, we are able to further determine a simple spin Hamiltonian describing all three systems. These results extend the 2D magnetism platform to Ising, Heisenberg, and XY spin classes in a single material family. Using magneto-optical measurements, we additionally demonstrate that ferromagnetism can be stabilized down to monolayer in more isotropic CrBr$_3$, with transition temperature still close to that of the bulk.