Experimental observation of Bethe strings.

Almost a century ago, string states-complex bound states of magnetic excitations-were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg-Ising chain SrCoVO in strong longitudinal magnetic fields.

Structural and Magnetic Properties of the Trirutile-type 1D-Heisenberg Anti-Ferromagnet CuTaO.

We prepared trirutile-type polycrystalline samples of CuTaO by low-temperature decomposition of a Cu-Ta-oxalate precursor. Diffraction studies at room temperature identified a slight monoclinic distortion of the hitherto surmised tetragonal trirutile crystal structure. Detailed high-temperature X-ray and neutron powder diffraction investigations as well as Raman scattering spectroscopy revealed a structural phase transition at 503(3) K from the monoclinic structure to the tetragonal trirutile structure.

Crystal structure and magnetic properties of FeSeO(3)F--alternating antiferromagnetic S = 5/2 chains.

The new oxofluoride FeSeO3F, which is isostructural with FeTeO3F and GaTeO3F, was prepared by hydrothermal synthesis, and its structure was determined by X-ray diffraction. The magnetic properties of FeSeO3F were characterized by magnetic susceptibility and specific heat measurements, by evaluating its spin exchanges on the basis of density functional theory (DFT) calculations, and by performing a quantum Monte Carlo simulation of the magnetic susceptibility. FeSeO3F crystallizes in the monoclinic space group P21/n and has one unique Se(4+) ion and one unique Fe(3+) ion.