Earlier this year two groups observed the first signs of intrinsic ferromagnetism in few-layer two-dimensional materials. (See Physics Today, July 2017, page 16.) The discovery was hardly inevitable. Phase transitions, including the transition to long-range magnetic order, behave differently when the number of dimensions is reduced. Until just a few months ago, it wasn’t clear that ferromagnetic order could exist in an isolated 2D system.
In a different respect, though, magnetism is widely viewed as a fundamentally 2D phenomenon. Magnetic spin textures—walls separating domains of uniform magnetization, skyrmions, vortices, and other inhomogeneous configurations—are almost always studied in thin magnetic films where the magnetization varies in only two dimensions and is mostly uniform over the film thickness. The films are tens of nanometers thick, an order of magnitude thicker than the 2D materials where the reduced dimensionality disrupts the magnetism itself.
In a bulk material, there’s more room for...
