Spin Correlations in the Dipolar Pyrochlore Antiferromagnet Gd2Sn2O7

TL;DR

This study uses neutron scattering and Monte Carlo simulations to analyze spin correlations in Gd2Sn2O7, revealing weak further-neighbour interactions, anisotropic correlations, and diffuse scattering patterns indicative of complex magnetic behavior.

Contribution

It provides new insights into the weak exchange interactions and anisotropic spin correlations in Gd2Sn2O7, connecting experimental data with theoretical models.

Findings

Detection of weak further-neighbour exchange interactions (~0.5%)

Observation of rods of diffuse scattering along [111] directions

Identification of highly anisotropic spin correlations sensitive to critical fluctuations

Abstract

We investigate spin correlations in the dipolar Heisenberg antiferromagnet Gd2Sn2O7 using polarised neutron-scattering measurements in the correlated paramagnetic regime. Using Monte Carlo methods, we show that our data are sensitive to weak further-neighbour exchange interactions of magnitude ~0.5% of the nearest-neighbour interaction, and are compatible with either antiferromagnetic next-nearest neighbour interactions, or ferromagnetic third-neighbour interactions that connect spins across hexagonal loops. Calculations of the magnetic scattering intensity reveal rods of diffuse scattering along [111] reciprocal-space directions, which we explain in terms of strong antiferromagnetic correlations parallel to the set of <110> directions that connect a given spin with its nearest neighbours. Finally, we demonstrate that the spin correlations in Gd2Sn2O7 are highly anisotropic, and correlations parallel to third-neighbour separations are particularly sensitive to critical fluctuations associated with incipient long-range order.