A surface-confined spiral state with the double period in the cubic chiral helimagnet Cu2OSeO3
The chiral magnetoelectric insulator Cu 2 OSeO 3 hosts a rich and anisotropic magnetic phase diagram that includes helical, conical, field-polarised, tilted conical, and skyrmion lattice phases. Using resonant elastic x-ray scattering (REXS), we uncover a new spiral state confined to the surface of Cu 2 OSeO 3 . This surface-confined spiral state (SSS) displays a real-space pitch of ~ 120 nm, which remarkably is twice the length of the incommensurate structures observed to-date in Cu 2 OSeO 3 . The SSS phase emerges at temperatures below 30 K when the magnetic field is applied between 3 ∘ to 18 ∘ away from the 〈110〉 crystallographic axes. Its surface localisation is demonstrated through a combination of REXS in reflection and transmission geometries, with complementary small-angle neutron scattering measurements suggesting its absence from the bulk. We attribute the stabilisation of the SSS to competing anisotropic interactions at the crystal surface. The discovery of a robust, surface-confined spiral paves the way for engineering energy-efficient, nanoscale spin-texture platforms for next-generation devices.
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Baral, P. R., Utesov, O. I., Moody, S. H., Littlehales, M. T., Gargiani, P., Valvidares, M., Cubitt, R., Steinke, N.-J., Luo, C., Radu, F., Magrez, A., White, J., & Ukleev, V. (2026). A surface-confined spiral state with the double period in the cubic chiral helimagnet Cu2OSeO3. Npj Quantum Materials. https://doi.org/10.1038/s41535-026-00892-6
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