Magnetic Excitations and Electronic Interactions in Sr 2 CuTeO 6 : A Spin- 1 / 2 Square Lattice Heisenberg Antiferromagnet

International audienceSr2CuTeO6 presents an opportunity for exploring low-dimensional magnetism on a square lattice ofS ¼ 1=2 Cu2þ ions. We employ ab initio multireference configuration interaction calculations to unravelthe Cu2þ electronic structure and to evaluate exchange interactions in Sr2CuTeO6. The latter results arevalidated by inelastic neutron scattering using linear spin-wave theory and series-expansion corrections forquantum effects to extract true coupling parameters. Using this methodology, which is quite general, wedemonstrate that Sr2CuTeO6 is an almost ideal realization of a nearest-neighbor Heisenberg antiferromagnetbut with relatively weak coupling of 7.18(5) meV