Randomness and Frustration in a S = 1/2 Square-Lattice Heisenberg Antiferromagnet

TL;DR

This study investigates how randomness and magnetic frustration influence the ground state and excitations in a series of S=1/2 Heisenberg square-lattice compounds, revealing that quenched randomness dominates the physics over frustration.

Contribution

It introduces a bond-disorder model that accurately reproduces short-range spin correlations and neutron scattering data in mixed compounds, highlighting the primary role of randomness.

Findings

Quenched randomness governs the magnetic ground state.

Short-range spin correlations are predominant.

Model predictions align with experimental neutron data.

Abstract

We explore the interplay between randomness and magnetic frustration in the series of $S = 1/2$ Heisenberg square-lattice compounds Sr$_2$CuTe$_{1-x}$W$_x$O$_6$. Substituting W for Te alters the magnetic interactions dramatically, from strongly nearest-neighbor to next-nearest-neighbor antiferromagnetic coupling. We perform neutron scattering measurements to probe the magnetic ground state and excitations over a range of $x$. We propose a bond-disorder model that reproduces ground states with only short-ranged spin correlations in the mixed compounds. The calculated neutron diffraction patterns and powder spectra agree well with the measured data and allow detailed predictions for future measurements. We conclude that quenched randomness plays the major role in defining the physics of Sr$_2$CuTe$_{1-x}$W$_x$O$_6$ with frustration being less significant.