Skyrmion lattice in the doped semiconductor Fe 1 − x Co x Si

We report a comprehensive small angle neutron scattering study of the magnetic phase diagram of the doped semiconductor ${\text{Fe}}_{1\ensuremath{-}x}{\text{Co}}_{x}\text{Si}$ for $x=0.2$. For magnetic field parallel to the neutron beam we observe a sixfold intensity pattern under field cooling. The regime of the skyrmion lattice is highly hysteretic and extents over a wide temperature range as may be expected due to the site disorder of the Fe and Co atoms. Our study identifies ${\text{Fe}}_{1\ensuremath{-}x}{\text{Co}}_{x}\text{Si}$ as the second material in which a skyrmion lattice forms and establishes that skyrmion lattices exist also in doped semiconductors.