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  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 Access 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 J_intra=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.