Ultrathin, High-Aspect Ratio, and Free-Standing Magnetic Nanowires by Exfoliation of Ferromagnetic Quasi-One-Dimensional van der Waals Lattices.

Driven by numerous discoveries of novel physical properties and integration into functional devices, interest in one-dimensional (1D) magnetic nanostructures has grown tremendously. Traditionally, such structures are accessed with bottom-up techniques, but these require increasing sophistication to allow precise control over crystallinity, branching, aspect ratio, and surface termination, especially when approaching the subnanometer regime in magnetic phases. Here, we show that mechanical exfoliation of bulk quasi-one-dimensional crystals, a method similar to those popularized for two-dimensional van der Waals (vdW) lattices, serves as an efficient top-down method to produce ultrathin freestanding nanowires that are both magnetic and semiconducting. We use CrSbSe as a representative quasi-1D vdW crystal with strong magnetocrystalline anisotropy and show that it can be exfoliated into nanowires with an average cross-section of 10 ± 2.8 nm. The CrSbSe nanowires display reduced Curie-Weiss temperature but higher coercivity and remanence than the bulk phase. The methodology developed here for CrSbSe, a representative for a vast class of 1D vdW lattices, serves as a blueprint for investigating confinement effects for 1D materials and accessing functional nanowires that are difficult to produce via traditional bottom-up methods.