SPICE Workshop on Nanomagnetism in 3D, April 30th - May 2nd 2024
Shinichiro Seki
Magnetic skyrmion, i.e., a topologically stable swirling spin configuration, has recently attracted attention as a potential candidate for high-density information bits. In two-dimensional systems, magnetic skyrmion behaves as a particle-object, and it is usually stabilized by Dzyaloshinskii-Moriya interaction in noncentrosymmetric systems.
In this talk, I will introduce two recent advancements in this field.
First, I overview the experimental discovery of extremely small diameter (less than 5 nm) of skyrmions in centrosymmetric systems, which probably originate from the competition of RKKY and four-spin interactions. In particular, I focus on a series of centrosymmetric tetragonal magnets such as GdRu2Si2[1,2], EuAl4[3] and GdRu2Ge2[4], where a rich variety of topological magnetic quasi-particles (such as circular skyrmion, elliptic skyrmion and meron/anti-meron pair) are found to form a periodic lattice. Some other relevant materials with three-dimensional non-coplanar topological spin texture will also be introduced[5].
Second, I discuss the three-dimensional structure and dynamics of magnetic skyrmions. By employing the magnetic X-ray tomography technique, the direct experimental observation of three-dimensional shape of skyrmion strings has successfully been demonstrated[6]. The propagation character of excitation modes in such skyrmion strings has also been investigated by the propagating spin wave spectroscopy technique, which suggests that skyrmion strings may be utilized as a flexible information transmission line [7].
[1] N. D. Khanh, S. Seki et al., Nature Nanotechnology 15, 444 (2020).[2] Y. Yasui, S. Seki et al., Nature Communications 11, 5925 (2020).
[3] R. Takagi, S. Seki et al., Nature Communications 13, 1472 (2022).
[4] H. Yoshimochi, S. Seki et al., Nature Physics (in press). (arXiv:2402.13751)
[5] H. Takagi, S. Seki et al., Nature Physics 19, 961 (2023).
[6] S. Seki et al., Nature Materials 21, 181 (2022).
[7] S. Seki et al., Nature Communications 11, 256 (2020).