Pressure-induced magnetic order in FeSe: A muon spin rotation study

The magnetic order induced by the pressure was studied in FeSe by means of muon spin rotation (μSR) technique. By following the evolution of the oscillatory part of the μSR signal as a function of angle between the initial muon spin polarization and 101 axis of the studied FeSe sample, it was found that the pressure-induced magnetic order in FeSe corresponds either to the collinear (single-stripe) antiferromagnetic order as observed in parent compounds of various FeAs-based superconductors or to the bi-collinear order as obtained in the FeTe system, but with the Fe spins turned by 45° within the ab plane. The value of the magnetic moment per Fe atom was estimated to be ≅0.13–0.14 μ_B at p ≅ 1.9 GPa.