Wen-Gen Zheng, Victor Balédent, Claire V. Colin, Françoise Damay, Jean-Pascal Rueff, Anne Forget, Dorothée Colson and Pascale Foury-Leylekian
It has been recently observed that a superconducting phase emerges under pressure in the Fe-based spin-ladders BaFe2X3 (X = S, Se). The low dimensionality of the Fe spin-ladders, which simplifies the elaboration of theoretical models, should help to understand the mechanism of superconductivity. We investigate here the frontier between magnetic and superconducting (SC) phases in BaFe2Se3 by performing challenging powder neutron diffraction (PND) and Fe Kβ x-ray emission spectroscopy (XES) under high pressure. We show that the ambient pressure ground state with a block-like magnetic order is destabilized under pressure. A pressure-induced antiferromagnetic stripe-like spin order, similar to the magnetic order of the parent superconductor BaFe2S3, is observed above 3-4 GPa. Our discovery shows that the stripe magnetic order is a key phase close to the SC dome and its particular magnetic fluctuations could be involved in the stabilization of superconductivity in Fe-based spin ladders.