Uniaxial-stress Effects on Helimagnetic Orders and Skyrmion Lattice in Cu2OSeO3

Uniaxial-stress effects on magnetic orders in Cu2OSeO3, which is a long-wavelength helimagnet hosting magnetic skyrmions, have been investigated by means of ac magnetic susceptibility and small angle neutron scattering measurements in magnetic fields. We applied uniaxial compressive stress and magnetic field along the [110] and \([1\bar{1}0]\) axes of the crystal, respectively, revealing that the application of the uniaxial stress enhances Dzyaloshinsky–Moriya interaction along the [001] axis. As a result, helical and skyrmion lattice (SkL) phases with modulation wave vectors parallel to the [001] axis were expanded in the H–T magnetic phase diagram. We have also found that field cooling under a moderate uniaxial stress of 51 MPa yields a metastable SkL state in a wide temperature range. This metastable state persists even after reducing uniaxial stress from 51 to 1 MPa at 40 K, which is far below the temperature range where the thermoequilibrium SkL exists (56–58 K), highlighting the topological stabilit...