Multiple antiferromagnetic phases and magnetic anisotropy in exfoliated CrBr$_3$ multilayers

TL;DR

This study reveals multiple magnetic phases in exfoliated CrBr3 multilayers, showing smaller uniaxial anisotropy than CrI3, and demonstrates the potential for creating non-collinear magnetic textures through stacking control.

Contribution

It provides the first experimental observation of multiple magnetic phases in CrBr3 multilayers and links these phases to specific stacking configurations, supported by theoretical calculations.

Findings

Identified ferromagnetic and two antiferromagnetic phases in CrBr3 multilayers.

Smaller uniaxial anisotropy in CrBr3 compared to CrI3.

Stacking-dependent interlayer exchange energies confirmed by experiments and theory.

Abstract

In twisted two-dimensional (2D) magnets, the stacking dependence of the magnetic exchange interaction can lead to regions of ferromagnetic and antiferromagnetic interlayer order, separated by non-collinear, skyrmion-like spin textures. Recent experimental searches for these textures have focused on CrI$_3$, known to exhibit either ferromagnetic or antiferromagnetic interlayer order, depending on layer stacking. However, the very strong uniaxial anisotropy of CrI$_3$ disfavors smooth non-collinear phases in twisted bilayers. Here, we report the experimental observation of three distinct magnetic phases -- one ferromagnetic and two antiferromagnetic -- in exfoliated CrBr$_3$ multilayers, and reveal that the uniaxial anisotropy is significantly smaller than in CrI$_3$. These results are obtained by magnetoconductance measurements on CrBr$_3$ tunnel barriers and Raman spectroscopy, in conjunction with density functional theory calculations, which enable us to identify the stackings responsible for the different interlayer magnetic couplings. The detection of all locally stable magnetic states predicted to exist in CrBr$_3$ and the excellent agreement found between theory and experiments, provide complete information on the stacking-dependent interlayer exchange energy and establish twisted bilayer CrBr$_3$ as an ideal system to deterministically create non-collinear magnetic phases.