Spin waves and magnetic exchange interactions in the spin-ladder compound RbFe2Se3

We report an inelastic neutron scattering study of the spin waves of the one-dimensional antiferromagnetic spin ladder compound RbFe2Se3. The results reveal that the products, SJ's, of the spin S and the magnetic exchange interaction J along the antiferromagnetic (leg) direction and the ferromagnetic (rung) direction are comparable with those for the stripe ordered phase of the parent compounds of the iron-based superconductors. The universality of the SJ's implies nearly universal spin wave dynamics and the irrelevance of the fermiology for the existence of the stripe antiferromagnetic order among various Fe-based materials.