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

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.

10 pages, 7 figures