Rod motifs in neutron scattering in spin ice

Neutron scattering is a technique of choice to study magnetic correlations in real materials. Discerning topological contributions therein is, however, a tall order. Bow-tie features are a notable exception in that they provide a diagnostic of topological magnetism. Accordingly, the fate of bow ties is remarkably universal. The authors explain why they blur into characteristic rod-like features in a number of pyrochlore oxides. They find that these rods do not indicate correlations of reduced dimensionality as one would naively expect from Fourier analysis. Rather, they present an additional item in the collection of motifs characteristic of topological magnetism. The researchers present two very simple models which explain their appearance, and elucidate the role played by monopole excitations.