Di Xiao Publishes in Nature; Article Subject of “News & Views”

In a joint experimental and theoretical study, Di Xiao and collaborators from several groups across the country and from China observed out-of-plane magnetism in a monolayer of chromium triiodide (CrI3). The study, entitled further described the dependence of the magnetic ordering on the number of layers in the material—bilayer CrI3 displays suppressed magnetization, whereas in trilayer CrI3 the interlayer ferromagnetism is restored. This thickness-dependent behavior is typical of van der Waals crystals. The findings are reported in an article entitled “Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit” that was published in this month’s issue of Nature. 

The article was also the subject of a “News & Views” piece, “Condensed-matter physics: Magnetism in flatland”, written by Nitin Samarth. Samarth explained how the authors of the article used the high-sensitivity polar magneto-optical Kerr effect microscopy technique to observe ferromagnetic behavior in atomically thin layers of the magnetic material CrI3. Indeed, an approach to studying truly two-dimensional ferromagnets had been lacking up to now. However, the breakthrough in the area was double: in addition to the study involving Di Xiao, a second article also published in Nature and commented upon in the News & News piece, reported intrinsic Heisenberg ferromagnetism in two-dimensional van der Waals crystals of Cr2Ge2Te6.

Both studies pave the way for exploring fundamental physics, such as topological effects in ferromagnetic van der Waals heterostructures as well as the engineering of new magneto-optoelectronic devices and for applications such as ultra-compact spintronics.

a, Polar MOKE signal for a CrI3 monolayer. The inset shows an optical image of an isolated monolayer (the scale bar is 2 μm). b, Power dependence of the MOKE signal taken at incident powers of 3 μW (blue), 10 μW (pink), and 30 μW (red). c, MOKE maps at μoH = 0 T, 0.15 T and 0.3 T on a different monolayer. The scale bar is 1 μm. dθK versus μ0H sweeps taken at four points marked by dots on the μoH = 0.3 T map in ce, Temperature dependence of MOKE signal with the sample initially cooled at μoH = 0 T (blue) and 0.15 T (red).