MT08
84
-Interaction of propagating spin waves with a skyrmion in
perpendicularly magnetized thin-film nanostripes
Junhoe Kim*, Jaehak Yang, Bosung Kim, Young-Jun Cho and Sang-Koog Kim
National Creative Research Initiative Center for Spin Dynamics and Spin-Wave Devices, Nanospinics Laboratory, Department of Materials. Science and Engineering, Seoul National University, Seoul 151-744, South Korea
1. Introduction
Magnetic skyrmions, topological solitons with an integer topological charge, have been found in magnetic bulk materials of non-centrosymmetry as well as in magnetic thin films with large spin-orbit coupling at inversion- symmetry-broken interfaces [1,2]. It is known that this anti-symmetric coupling, known as Dzyaloshinskii-Moriya interaction (DMI), plays a crucial role in stabilizing skyrmion formation. Skyrmions’ topological stability is advantageous in applications to memory devices, owing to both their nano-scale dimensions and ultra-low critical current density. In this light, reliable manipulation of magnetic skyrmions by electric currents or magnetic fields has attracted great interest. Very recently, skyrmion motions also have been found to be driven by spin waves (SWs) propagation in nanostrips [3, 4]. This alternative approach is of special interest in terms of the promise of all-magnetic control of skyrmions in geometrically constricted elements. However, the underlying physics of SW-skyrmion interactions are still lacking.
2. Methods and Results
In the present study, we employed micromagnetic numerical simulations to examine SW-driven skyrmion motions and elucidate their underlying physics. We found interactions between propagating spin waves (SWs) and a single skyrmion in perpendicularly magnetized nanostrips with DMI. Incident SWs from one end interact with the skyrmion located at the center, giving rise to considerable forward skyrmion motions for specific SW frequencies.
3. Discussion
The frequency-dependent interaction originated from the robust coupling of the SWs with the internal modes of the skyrmion. Here we present correlations of the SW propagation and skyrmion modes. This work provides further understanding of the interactions between magnons and topological solitons in constricted geometries.
4. Conclusion
We studied the propagations of spin waves in W/CoFeB/MgO thin-film nanostrips and their interactions with a skyrmion in the waveguides. It was found that propagating spin waves lead to the rotation and linear motions of the skyrmion. In addition, the rotation sense of the skyrmion and the speed of its linear motion depend on the excitation frequency of spin waves. As reported in Refs [5,6], DMI leads to asymmetric spin waves propagations in the spin-wave guides, thus this effect seems to affect such skyrmion motions as found from this work.
85
-5. References
[1] S. Heinze, K. V. Bergmann, M. Menzel, J. Brede, A. Kubetzka, R. Wiesendager, G. Bihlmayer, and S. Blügel, Nature Phys. 7, 713 (2011).
[2] A. Fert, V. Cros, and J. Sampaio, Nature Nanotech. 8, 152 (2013).
[3] X. Zhang, M. Ezawa, D. Xiao, G. P. Zhao, Y. Liu, and Y. Zhou, Nanotechnol. 26, 225701 (2015). [4] J. Ding, X. Yang, and T. Zhu, IEEE Trans. Magn. 51, 1500504 (2015).
[5] J. Moon, S.-M. Seo, K.-J. Lee, K.-W. Kim, J. Ryu, H.-W. Lee, R. D. McMichael, and M. D. Stiles, Phys. Rev. B 88, 184404 (2013).
[6] F. Garcia-Sanchez, P. Borys, A. Vansteenkiste, J.-V. Kim, and R. L. Stamps, Phys. Rev. B 89, 224408 (2014).
