One-dimensional CrI3 encapsulated within multi-walled carbon nanotubes

The production of single-walled inorganic nanotubes is challenging due to the energetic favorability of multi-walled structures during synthesis. CrI3, a layered ferromagnetic insulator, has gained significant attention as the first stand-alone monolayer ferromagnet, sparking interest in two-dimensional magnetic materials. Here, we report the synthesis of high-quality, monolayer CrI3 nanotubes encapsulated within multiwalled carbon nanotubes (MWCNTs), ranging from 2 to 10 nm with an average diameter of 5.3 nm, as well as a smaller amount of CrI3 nanorods. Through aberration-corrected transmission electron microscopy, X-ray magnetic circular dichroism (XMCD) spectroscopy, and first-principles calculations, we explored the fundamental physics and magnetism of these 1D van der Waals heterostructures. These findings pave the way towards the exploration of non-collinear magnetic states in tubular geometries, driven by the interplay of magnetic anisotropy and curvature. Producing single-walled inorganic nanotubes is challenging because their multi-walled counterparts are favored during synthesis. Here, the authors produce one-dimensional single-walled CrI3 encapsulated within multi-walled carbon nanotubes and explore their magnetic properties.