Multiple antiferromagnetic phases and magnetic anisotropy in exfoliated CrBr3 multilayers

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 CrI3, known to exhibit either ferromagnetic or antiferromagnetic interlayer order, depending on layer stacking. However, the very strong uniaxial anisotropy of CrI3 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 CrBr3 multilayers, and reveal that the uniaxial anisotropy is significantly smaller than in CrI3. These results are obtained by magnetoconductance measurements on CrBr3 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 CrBr3 and the excellent agreement found between theory and experiments, provide complete information on the stacking-dependent interlayer exchange energy and establish twisted bilayer CrBr3 as an ideal system to deterministically create non-collinear magnetic phases. Van der Waals materials often exhibit different metastable structures, with the constituent layers shifted by small, atomic scale distances. If the material is magnetic, the resulting different layer stackings can cause drastic changes in magnetic ordering. Here, Yao et al. observe all three locally stable magnetic orderings predicted to occur in CrBr3 multilayers, two antiferromagnetic and one ferromagnetic.

Automated summary

This study reports the observation of three distinct magnetic phases in exfoliated CrBr3 multilayers and reveals that the uniaxial anisotropy in CrBr3 is significantly smaller than in CrI3. These findings provide important information on the stacking-dependent interlayer exchange energy and establish CrBr3 as an ideal system for creating non-collinear magnetic phases.