Skyrmion lattice in the doped semiconductor Fe_1-xCo _xSi

We report a comprehensive small angle neutron scattering study of the magnetic phase diagram of the doped semiconductor Fe1-x Cox 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 Fe1-x Cox Si as the second material in which a skyrmion lattice forms and establishes that skyrmion lattices exist also in doped semiconductors.