Purely antiferromagnetic frustrated Heisenberg model in the spin-ladder compound BaFe2Se3

The spin dynamics in the block magnetic phase of the iron-based ladder compound BaFe2Se3 has been studied by means of single-crystal inelastic neutron scattering. Using linear spin-wave theory and Monte Carlo simulations, our analysis points to a magnetic Heisenberg model with effective frustrated antiferromagnetic couplings only, able to describe both the exotic block order and its dynamics. This new and purely antiferromagnetic picture offers a fruitful perspective to describe multiferroic properties, but also understand the origin of the stripelike magnetic instability observed under pressure as well as in other parent compounds with similar crystalline structure.