• Chillal, S.; Islam, A. T. M. N.; Steffens, P.; Bewley, R.; Lake, B.: Weak three-dimensional coupling of Heisenberg quantum spin chains in SrCuTe2O6. Physical Review B 104 (2021), p. 144402/1-8

10.1103/PhysRevB.104.144402
Open Accesn Version

Abstract:
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 and 2 K. The high-temperature spectra reveal a characteristic diffuse scattering corresponding to a multispinon continuum, confirming the dominant quantum spin chain behavior due to the third neighbor interaction Jintra=4.22~meV (49 K). The low-temperature spectra exhibit sharper excitations at energies <1.25 meV, which can be explained by considering a combination of weak antiferromagnetic first nearest neighbor interchain coupling J1=0.17~meV (1.9 K) and even weaker ferromagnetic second nearest neighbor 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 isostructural quantum spin liquid candidate PbCuTe2O6.