Spin waves and magnetic ordering in the quasi-one-dimensional S

Elastic and inelastic neutron scattering were used to study the ordered phase of the quasi-one-dimensional spin-1/2 antiferromagnet BaCu2Si2O7. The previously proposed model for the low-temperature magnetic structure was confirmed. Spin-wave dispersion along several reciprocal-space directions was measured and interchain, as well as in-chain exchange constants were determined. A small gap in the spin-wave spectrum was observed and attributed to magnetic anisotropy effects. The results are discussed in comparison with existing theories for weakly coupled quantum spin chain antiferromagnets