Spin dynamics of the spin chain antiferromagnet RbFeS$_2$

TL;DR

This study investigates the spin dynamics and magnetic properties of RbFeS$_2$, revealing a spin gap, exchange interactions, and magnetic ordering, contributing to understanding quasi-one-dimensional antiferromagnetic systems.

Contribution

It provides detailed measurements and modeling of spin excitations in RbFeS$_2$, highlighting similarities with other Fe$^{3+}$ spin chain systems and iron pnictide superconductors.

Findings

Antiferromagnetic transition at 195 K.

Dispersive spin waves with a 5 meV gap.

Exchange interactions similar to other Fe$^{3+}$ systems.

Abstract

We report transport and inelastic neutron scattering studies on electronic properties and spin dynamics of the quasi-one-dimensional spin chain antiferromagnet RbFeS$_2$. An antiferromagnetic phase transition at $T_N\approx195$ 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 inter-chain exchange interactions are found to be $SJ_1=100(5)$ meV and $SJ_3=0.9(3)$ meV, respectively, together with a small single-ion anisotropy of $SD_{zz}=0.04(1)$ meV. Comparison with previous results for other materials in the same class of Fe$^{3+}$ spin chain systems reveals that although the magnetic order sizes show significant variation from 1.8 to 3.0$\mu_B$ 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.