Probing magnetism in 2D materials at the nanoscale with single-spin microscopy

Abstract

A detailed look into 2D magnetism The van der Waals material chromium triiodide (CrI 3 ) is a ferromagnet in the bulk but appears to become antiferromagnetic when thinned to a few atomic layers. Thiel et al. used a local magnetometry technique based on diamond nitrogen-vacancy centers to study the magnetism of these thin films at the nanoscale (see the Perspective by Fernández-Rossier). In agreement with previous results, films with odd numbers of layers had magnetization values consistent with that of a single layer, indicating antiferromagnetic coupling. But when the researchers' probe caused an accidental puncture, the magnetization of a nine-layer film increased approximately ninefold to a value expected in a ferromagnetic material. Further characterization suggested that the puncture had caused a structural transition, linking the structural and magnetic properties of this enigmatic system. Science , this issue p. 973 ; see also p. 935