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.

We report pressure-dependent neutron diffraction and muon spin relaxation/rotation measurements combined with first-principles calculations to investigate the structural, magnetic, and electronic properties of BaFe₂S₃ under pressure. The experimental results reveal a gradual enhancement of the stripe-type ordering temperature with increasing pressure up to 2.6 GPa and no observable change in the size of the ordered moment. The ab initio calculations suggest that the magnetism is highly sensitive to the Fe-S bond lengths and angles, clarifying discrepancies with previously published results. In contrast to our experimental observations, the calculations predict a monotonic reduction of the ordered moment with pressure. We suggest that the robustness of the stripe-type antiferromagnetism is due to strong electron correlations not fully considered in the calculations.