Title: Elucidation of the helical spin structure of FeAs,
Abstract: We present the results of resonant x-ray scattering measurements and
electronic structure calculations on the monoarsenide FeAs. We elucidate
details of the magnetic structure, showing the ratio of ellipticity of the spin
helix is larger than previously thought, at 2.58(3), and reveal both a
right-handed chirality and an out of plane component of the magnetic moments in
the spin helix. We find that electronic structure calculations and analysis of
the spin-orbit interaction are able to qualitatively account for this canting.