Crystal chirality and skyrmion helicity in MnSi and (Fe, Co)Si as determined by transmission electron microscopy

The magnetic skyrmions as derived from the proper screw spin state in chiral-lattice magnets (e.g., MnSi) show the intrinsic spin swirling direction or the magnetic helicity. The crystal chirality (Γc) and skyrmion helicity (γₛ) were simultaneously determined at the identical specimen areas of MnSi and Fe_1-xCoₓSi ($x=0.2,0.5$) by using convergent-beam electron diffraction and Lorentz transmission electron microscopy techniques, respectively. The reversal of the Γc-γₛ correlation is observed between MnSi and Fe_1-xCoₓSi and ascribed to the different sign of the Dzyaloshinskii-Moriya interaction between both compounds.