Christopher Marrows

Affiliation

• School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom

Title

Chiral magnetic states driven by bulk and interfacial Dzyaloshinskii-Moriya interactions

Abstract

The Dzyaloshinskii-Moriya interaction (DMI) arises in situations where structural inversion symmetry is broken and favours chiral magnetic states. Whilst considered a curiosity for many decades, it has recently become a topic of intense interest due to its ability to stabilise spin textures with non-trivial topology, most notably skyrmion states [1,2]. In order to realise skyrmion-based spintronics, thin films showing strong DMI are needed [3]. Structural inversion symmetry is broken in bulk in the B20 lattice, which is possessed by the helimagnetic metal FeGe. We have grown epilayers of this material show interesting transport properties [4], can have their chiral states controlled by ferromagnetic capping layers [5], and show in inversion of the sign of the DMI on doping with Co. On the other hand, structural inversion asymmetry is slao naturally present at an intereface, and ultrathin (sub-nm) magnetic layers (which are often perpendicularly magnetised) will also show DMI [6]. We have shown that the DMI of sputtered Pt/Co/Pt layers can be inverted by the insertion of an Ir overlayer [7], that the sign and magnitude of the DMI in Pt/Co/Pt can be contolled by varying differences in interfacial roughness above and below the Pt, and that the DMI can be made to oscillate by varying the electron count of the top layer in Pt/Co/Pt_1-x-yIr_xAu_y trilayers.

References

• [1] S. Mühlbauer et al. Skyrmion lattice in a chiral magnet, Science 323, 915 (2009).
• [2] X. Z. Yu et al, Real-space observation of a two-dimensional skyrmion crystal, Nature 465, 901 (2010).
• [3] N. Nagaosa and Y. Tokura, Topological properties and dynamics of magnetic skyrmions, Nature Nanotechnology 8, 899 (2013).
• [4] N. A. Porter, J. C. Gartside, and C. H. Marrows, Scattering mechanisms in textured FeGe thin films: Magnetoresistance and the anomalous Hall effect, Phys. Rev. B 90, 024403 (2014).
• [5] N. A. Porter, C. S. Spencer, R. C. Temple, C. J. Kinane, T. R. Charlton, S. Langridge, and C. H. Marrows, Manipulation of the spin helix in FeGe thin films and FeGe/Fe multilayers, arXiv:1506.01575.
• [6] A. Fert, Magnetic and transport properties of metallic multilayers, Materials Science Forum 59, 439 (1991).
• [7] A. Hrabec, N. A. Porter, A. Wells, M. J. Benitez, G. Burnell, S. McVitie, D. McGrouther, T. A. Moore, and C. H. Marrows, Measuring and tailoring the Dzyaloshinskii-Moriya interaction in perpendicularly magnetized thin films, Phys. Rev. B 90, 020402 (2014).