Absent pinch points and emergent clusters: further neighbour interactions in the pyrochlore Heisenberg antiferromagnet

TL;DR

This paper explains how weak further neighbour interactions in pyrochlore Heisenberg antiferromagnets can account for observed neutron scattering features, including emergent clusters and the absence of pinch points, challenging previous interpretations.

Contribution

It demonstrates through large-$n$ calculations and Monte Carlo simulations that weak further neighbour exchanges explain experimental spin correlations in frustrated pyrochlore systems.

Findings

Weak further neighbour interactions suppress pinch points.

Emergent spin clusters can arise from these weak interactions.

Theoretical results match neutron scattering observations.

Abstract

We discuss the origin of spin correlations observed in neutron scattering experiments on the paramagnetic phase of a number of frustrated spinel compounds, most notably ZnCr2O4. These correlations are striking for two reasons. First, they have been interpreted as evidence for the formation of weakly interacting hexagonal clusters of spins. Second, they are very different from those calculated for the nearest neighbour Heisenberg pyrochlore antiferromagnet, in which Coulomb phase correlations generate sharp scattering features known as pinch points. Using large-$n$ calculations and Monte Carlo simulations, we show that very weak further neighbour exchange interactions can account for both the apparent formation of clusters and the suppression of pinch points.