Physics Colloquium: Christoforos Moutafis (University of Manchester) - Towards Skyrmion-based Electronics
|When:||Th 15-02-2018 16:00 - 17:00|
Magnetic skyrmions are particle-like magnetic spin textures with a topology characterised by their Skyrmion number. They can arise due to the exchange, anisotropy and dipolar energy in the case of skyrmion bubbles and an additional Dzyaloshinskii-Moriya interaction (DMi) in the case of chiral skyrmions [1,2]. Skyrmionic structures can exhibit rich dynamical behaviour governed by their topology [1-3]. At the same time the ultra small size of the chiral skyrmions and their robustness makes them ideal candidates for a new generation of magnetoelectronic devices [1,2]. The recent demonstrations of room temperature chiral skyrmions are the first necessary step in order to control their dynamical behaviour and introduce them in devices. In previous work, nanoscale subnanosecond X-ray pump-probe imaging was used to demonstrate, for the first time, the gyrotropic mode of a single skyrmion bubble in the gigahertz regime (see Fig.1) and ii) the breathing-like behaviour of a pair of skyrmionic configurations.
The observed dynamics confirmed the skyrmion topology and showed the existence of an unexpectedly large inertia that is key for describing skyrmion dynamics . We have recently demonstrated by high resolution scanning transmission X-ray microscopy imaging the discovery of room temperature nanoscale (sub-100nm) individual chiral skyrmions in a technologically relevant material (see Fig.2) . We tailor-design cobalt-based multilayer thin films in order to engineer additive interfacial Dzyaloshinskii– Moriya interactions (DMIs) and achieve a high value of |D|=~2 mJ m–2. The recent observations of R.T. chiral skyrmions can serve as a basis for the development of skyrmion-based memory and logic devices and enable further fundamental studies on the very rich physics of skyrmions . We will also be presenting recent results with technological relevance on bound skyrmions in synthetic ferri–magnets confined in nanostructures, as well as results on skyrmion lattice melting in films.
1. N. Nagaosa and Y. Tokura, Nature Nanotech. 8, 899 (2013).
2. A. Fert, V. Cros, J. Sampaio, Nature Nanotech. 8, 152 (2013).
3. C. Moutafis, S. Komineas, J.A.C Bland, Phys. Rev. B 79, 224429 (2009).
4. F. Büttner, C. Moutafis, et al., Nature Physics 11, 225 (2015).
5. C. Moreau-Luchaire, Moutafis C., M Schneider, et al., Nature Nanotechnology 11, 444 (2016).
6. W. Legrand, D. Maccariello, et al., Nano Letters, 17 (4), 2703–2712 (2017).
7. P. E. Roy, Ruben M. Otxoa, C. Moutafis, 2018.
8. M. Charilaou, L. Pierobon, J. F. Loeffler, C. Moutafis, manuscript, 2018.