Bloch Point Quadrupole Constituting Hybrid Topological Strings Revealed with Electron Holographic Vector Field Tomography

Fehmi Sami Yasin, Jan Masell, Yoshio Takahashi, Tetsuya Akashi, Norio Baba, Kosuke Karube, Daisuke Shindo, Takahisa Arima, Yasujiro Taguchi, Yoshinori Tokura, Toshiaki Tanigaki, Xiuzhen Yu

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Topological magnetic (anti)skyrmions are robust string-like objects heralded as potential components in next-generation topological spintronics devices due to their low-energy manipulability via stimuli such as magnetic fields, heat, and electric/thermal current. While these 2D topological objects are widely studied, intrinsically 3D electron-spin real-space topology remains less explored despite its prevalence in bulky magnets. 2D-imaging studies reveal peculiar vortex-like contrast in the core regions of spin textures present in antiskyrmion-hosting thin plate magnets with S4 crystal symmetry, suggesting a more complex 3D real-space structure than the 2D model suggests. Here, holographic vector field electron tomography captures the 3D structure of antiskyrmions in a single-crystal, precision-doped (Fe0.63Ni0.3Pd0.07)3P (FNPP) lamellae at room temperature and zero field. These measurements reveal hybrid string-like solitons composed of skyrmions with topological number W = −1 on the lamellae's surfaces and an antiskyrmion (W = + 1) connecting them. High-resolution images uncover a Bloch point quadrupole (four magnetic (anti)monopoles that are undetectable in 2D imaging) which enables the observed lengthwise topological transitions. Numerical calculations corroborate the stability of hybrid strings over their conventional (anti)skyrmion counterparts. Hybrid strings result in topological tuning, a tunable topological Hall effect, and the suppression of skyrmion Hall motion, disrupting existing paradigms within spintronics.

Original languageEnglish
Article number2311737
JournalAdvanced Materials
Volume36
Issue number16
DOIs
StatePublished - Apr 18 2024
Externally publishedYes

Funding

The authors were very grateful to Tomoko Kikitsu (Materials Characterization Support Team in the RIKEN Center for Emergent Matter Science) for technical support on the TEM (JEM\u20102100F), as well as Ilya Belopolski, Max Hirschberger, Max Birch, and Naoto Nagaosa for helpful discussions. Y.T. acknowledges the support of the Japan Science and Technology Agency (JST) CREST program (Grant Number JPMJCR1874). X.Z.Y. acknowledges the support of Grants\u2010In\u2010Aid for Scientific Research (A) (Grant No. 19H00660) from JSPS and the JST\u2010CREST program (Grant No. JPMJCR20T1). J.M. was supported by the Alexander von Humboldt Foundation as a Feodor Lynen Return Fellow. The authors were very grateful to Tomoko Kikitsu (Materials Characterization Support Team in the RIKEN Center for Emergent Matter Science) for technical support on the TEM (JEM-2100F), as well as Ilya Belopolski, Max Hirschberger, Max Birch, and Naoto Nagaosa for helpful discussions. Y.T. acknowledges the support of the Japan Science and Technology Agency (JST) CREST program (Grant Number JPMJCR1874).\u00A0X.Z.Y. acknowledges the support of Grants-In-Aid for Scientific Research (A) (Grant No. 19H00660) from JSPS and the JST-CREST program (Grant No. JPMJCR20T1). J.M. was supported by the Alexander von Humboldt Foundation as a Feodor Lynen Return Fellow.

Keywords

  • 3D topology
  • Bloch points
  • Lorentz transmission electron microscopy
  • antiskyrmions
  • electron holography
  • hybrid strings
  • skyrmions

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