UC Berkeley

We report transport and inelastic neutron scattering studies on electronic properties and spin dynamics of the quasi-one-dimensional spin-chain antiferromagnet RbFeS2. An antiferromagnetic phase transition at TN≈195 K and dispersive spin waves with a spin gap of 5 meV are observed. By modeling the spin excitation spectra using linear spin wave theory, intra and interchain exchange interactions are found to be SJ1=100(5) meV and SJ3=0.9(3) meV, respectively, together with a small single-ion anisotropy of SDzz=0.04(1) meV. Comparison with previous results for other materials in the same class of Fe3+ spin-chain systems reveals that although the magnetic order sizes show significant variation from 1.8 to 3.0μB within the family of materials, the exchange interactions SJ are nevertheless quite similar, analogous to the iron pnictide superconductors where both localized and delocalized electrons contribute to the spin dynamics.