Magnetic excitations and electronic interactions in Sr$_2$CuTeO$_6$: a spin-1/2 square lattice Heisenberg antiferromagnet

TL;DR

This study combines ab initio calculations and neutron scattering to analyze magnetic excitations and electronic interactions in Sr$_2$CuTeO$_6$, revealing it as a near-ideal spin-1/2 square lattice Heisenberg antiferromagnet with weak coupling.

Contribution

It introduces a general methodology combining ab initio and neutron scattering analyses to accurately determine exchange interactions in low-dimensional magnetic materials.

Findings

Sr$_2$CuTeO$_6$ is an almost perfect realization of a nearest-neighbor Heisenberg antiferromagnet.

The exchange coupling in Sr$_2$CuTeO$_6$ is measured to be approximately 7.18 meV.

The combined approach validates the magnetic model with quantum corrections.

Abstract

Sr$_2$CuTeO$_6$ presents an opportunity for exploring low-dimensional magnetism on a square lattice of $S=1/2$ Cu$^{2+}$ ions. We employ ab initio multi-reference configuration interaction calculations to unravel the Cu$^{2+}$ electronic structure and to evaluate exchange interactions in Sr$_2$CuTeO$_6$. The latter results are validated by inelastic neutron scattering using linear spin-wave theory and series-expansion corrections for quantum effects to extract true coupling parameters. Using this methodology, which is quite general, we demonstrate that Sr$_2$CuTeO$_6$ is an almost realization of a nearest-neighbor Heisenberg antiferromagnet but with relatively weak coupling of 7.18(5) meV.