LAUSR

The magnetic Hamiltonian of the Heisenberg quantum antiferromagnet SrCuTe2O6 is studied by inelastic neutron scattering technique on powder and single crystalline samples above and below the magnetic transition temperatures at 8 K and 2 K. The high temperature spectra reveal a characteristic diffuse scattering corresponding to a multi-spinon continuum confirming the dominant quantum spin-chain behavior due to the third neighbour interaction Jintra = 4.22 meV (49 K). The low temperature spectra exhibits sharper excitations at energies below 1.25 meV which can be explained by considering a combination of weak antiferromagnetic first nearest neighbour interchain coupling J1 = 0.17 meV (1.9 K) and even weaker ferromagnetic second nearest neighbour J2 = −0.037 meV (−0.4 K) or a weak ferromagnetic J2 = −0.11 meV (−1.3 K) and antiferromagnetic J6 = 0.16 meV (1.85 K) giving rise to the long-range magnetic order and spin-wave excitations at low energies. These results suggest that SrCuTe2O6 is a highly one-dimensional Heisenberg system with three mutually perpendicular spin-chains coupled by a weak ferromagnetic J2 in addition to the antiferromagnetic J1 or J6 presenting a contrasting scenario from the highly frustrated hyper-hyperkagome lattice (equally strong antiferromagnetic J1 and J2) found in the iso-structural PbCuTe2O6 .