Uniaxial Pressure Dependence of Magnetic Order in MnSi.

We report comprehensive small angle neutron scattering measurements complemented by ac susceptibility data of the helical order, conical phase, and Skyrmion lattice phase (SLP) in MnSi under uniaxial pressures. For all crystallographic orientations uniaxial pressure favors the phase for which a spatial modulation of the magnetization is closest to the pressure axis. Uniaxial pressures as low as 1 kbar applied perpendicular to the magnetic field axis enhance the Skyrmion lattice phase substantially, whereas the Skyrmion lattice phase is suppressed for pressure parallel to the field. Taken together we present quantitative microscopic information on how strain couples to magnetic order in the chiral magnet MnSi.