In most ferromagnets the magnetization rotates from one domain to the next with no preferred handedness. However, broken inversion symmetry can lift the chiral degeneracy, leading to topologically rich spin textures such as spin spirals1,2 and skyrmions3,4,5 through the Dzyaloshinskii–Moriya interaction6 (DMI). Here we show that in ultrathin metallic ferromagnets sandwiched between a heavy metal and an oxide, the DMI stabilizes chiral domain walls2,7 (DWs) whose spin texture enables extremely efficient current-driven motion8,9,10,11. We show that spin torque from the spin Hall effect12,13,14,15 drives DWs in opposite directions in Pt/CoFe/MgO and Ta/CoFe/MgO, which can be explained only if the DWs assume a Néel configuration7,16 with left-handed chirality. We directly confirm the DW chirality and rigidity by examining current-driven DW dynamics with magnetic fields applied perpendicular and parallel to the spin spiral. This work resolves the origin of controversial experimental results10,17,18 and highlights a new path towards interfacial design of spintronic devices.
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This work was supported in part by the National Science Foundation under NSF-ECCS-1128439. Technical support from D. Bono is gratefully acknowledged. Devices were fabricated using instruments in the MIT Nanostructures Laboratory, the Scanning Electron-Beam Lithography facility at the Research Laboratory of Electronics, and the Center for Materials Science and Engineering at MIT. S.E. acknowledges financial support by the NSF Graduate Research Fellowship Program. The work by E.M. was supported by projects MAT2011-28532-C03-01 from the Spanish government and SA163A12 from Junta de Castilla y Leon.
The authors declare no competing financial interests.
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Emori, S., Bauer, U., Ahn, SM. et al. Current-driven dynamics of chiral ferromagnetic domain walls. Nature Mater 12, 611–616 (2013). https://doi.org/10.1038/nmat3675
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