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

Abstract

The magnetic order induced by the pressure was studied in FeSe by means of muon spin rotation ($\ensuremath{\mu}\mathrm{SR}$) technique. By following the evolution of the oscillatory part of the $\ensuremath{\mu}\mathrm{SR}$ 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 ${45}^{\mathrm{o}}$ within the $ab$ plane. The value of the magnetic moment per Fe atom was estimated to be $\ensuremath{\simeq}0.13--0.14\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$ at $p\ensuremath{\simeq}1.9$ GPa.