Strong ferromagnetic exchange interaction in the parent state of the superconductivity in BaFe$_2$S$_3$

TL;DR

This study uses inelastic neutron scattering to reveal strong ferromagnetic exchange interactions in BaFe$_2$S$_3$, a parent compound of iron-based superconductors, highlighting common spin excitation features across such materials.

Contribution

It provides the first detailed measurement of exchange interactions in BaFe$_2$S$_3$, showing strong ferromagnetic interactions along the rung, which is a novel insight into its magnetic properties.

Findings

Strong ferromagnetic exchange along the rung ($SJ_R=-71 ext{ meV}$)

Antiferromagnetic exchange along the leg ($SJ_L=49 ext{ meV}$)

Ferromagnetic exchange along the diagonal ($SJ_2=-15 ext{ meV}$)

Abstract

Inelastic neutron scattering measurements have been performed to investigate the spin waves of the quasi-one-dimensional antiferromagnetic ladder compound BaFe$_2$S$_3$, where a superconducting transition was observed under pressure [H. Takahashi {\it et al.}, Nat. Mater. 14, 1008-1012 (2015); T. Yamauchi {\it et al.}, Phys. Rev. Lett. 115, 246402 (2015)]. By fitting the spherically averaged experimental data collected on a powder sample to a Heisenberg Hamiltonian, we find that the one-dimensional antiferromagnetic ladder exhibits a strong nearest neighbor ferromagnetic exchange interaction ($SJ_R=-71\pm4$ meV) along the rung direction, an antiferromagnetic $SJ_L=49\pm3$ meV along the leg direction and a ferromagnetic $SJ_2=-15\pm2$ meV along the diagonal direction. Our data demonstrate that the antiferromagnetic spin excitations are a common characteristic for the iron-based superconductors, while specific relative values for the exchange interactions do not appear to be unique for the parent states of the superconducting materials.