Magnetic structures and spin dynamics in S=1/2 one-dimensional Heisenberg antiferromagnetic systems

Shinya Takaishi

Antonio S. T. Pires, M. E. Gouvêa

Mahalingam Mohan, Gerhard H. Muller

Recent low-temperature inelastic neutron scattering data on the quasi-one-dimensional (1D) Heisenberg-Ising antiferromagnet (AFM) CsCo${\mathrm{Cl}}_{3}$ call for new theoretical efforts, for the available theories fail to explain the observed line shapes. In this paper we initiate a detailed study of the dynamical properties of the 1D spin-\textonehalf{} anisotropic $\mathrm{XYZ}$ AFM with emphasis on the dynamic structure factor ${S}_{\ensuremath{\mu}\ensuremath{\mu}}(q,\ensuremath{\omega})$ at $T=0$. The structure of ${S}_{\ensuremath{\mu}\ensuremath{\mu}}(q,\ensuremath{\omega})$ is determined by the combined effects of the density of states and the matrix elements. Both effects are discussed for selected cases: the $\mathrm{XY}$-Heisenberg AFM (planar system), the Heisenberg-Ising AFM (uniaxial system), and the $\mathrm{XY}$-Ising AFM (biaxial system). The exact solution for ${S}_{\mathrm{zz}}(q,\ensuremath{\omega})$ of the $\mathrm{XY}$-Ising AFM has already many features in common with the experimental data on CsCo${\mathrm{Cl}}_{3}$. It is an ideal starting point for a perturbation approach to the Heisenberg-Ising AFM.

Alf Sjölander

H.-J. Mikeska, W. Pesch

The authors have evaluated an expression obtained previously for the dynamical spin correlation function of a linear Heisenberg antiferromagnet. The authors discuss the results in relation to both recent neutron scattering experiments and recent computations for finite chains with S= 1 / 2 . It is concluded that contributions to the dynamical structure factor from many accumulating low-frequency excitations provide the high-frequency strength required from sum rule arguments for small wavevectors.

Xiaolong Ma