Direct observation of van der Waals stacking–dependent interlayer magnetism

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Science  22 Nov 2019:
Vol. 366, Issue 6468, pp. 983-987
DOI: 10.1126/science.aav1937

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Stacking control

Recent searches for two-dimensional magnets have turned up a number of related van der Waals materials, such as chromium triiodide (CrI3) and chromium tribromide (CrBr3). Although their properties are expected to be similar, in bilayer form, the former is antiferromagnetic, whereas the latter appears to be a ferromagnet. Chen et al. used spin-polarized scanning tunneling microscopy to determine that the nature of the magnetic state in bilayer CrBr3 depends on the type of stacking of its monolayers. An antiferromagnetic state formed when the two monolayers were oriented in the same direction, whereas the opposite orientation led to ferromagnetism.

Science, this issue p. 983


Controlling the crystal structure is a powerful approach for manipulating the fundamental properties of solids. In van der Waals materials, this control can be achieved by modifying the stacking order through rotation and translation between the layers. Here, we observed stacking-dependent interlayer magnetism in the two-dimensional (2D) magnetic semiconductor chromium tribromide (CrBr3), which was enabled by the successful growth of its monolayer and bilayer through molecular beam epitaxy. Using in situ spin-polarized scanning tunneling microscopy and spectroscopy, we directly correlate the atomic lattice structure with the observed magnetic order. Although the individual monolayer CrBr3 is ferromagnetic, the interlayer coupling in bilayer depends on the stacking order and can be either ferromagnetic or antiferromagnetic. Our observations pave the way for manipulating 2D magnetism with layer twist angle control.

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