@article{13103,
  keywords = {Electrical and Electronic Engineering, Condensed Matter Physics, General Materials Science, Biomedical Engineering, Atomic and Molecular Physics, and Optics, Bioengineering},
  author = {Arjun Rana and Chen-Ting Liao and Ezio Iacocca and Ji Zou and Minh Pham and Xingyuan Lu and Emma-Elizabeth Subramanian and Yuan Lo and Sinéad Ryan and Charles Bevis and Robert Karl and Andrew Glaid and Jeffrey Rable and Pratibha Mahale and Joel Hirst and Thomas Ostler and William Liu and Colum O’Leary and Young-Sang Yu and Karen Bustillo and Hendrik Ohldag and David Shapiro and Sadegh Yazdi and Thomas Mallouk and Stanley Osher and Henry Kapteyn and Vincent Crespi and John Badding and Yaroslav Tserkovnyak and Margaret Murnane and Jianwei Miao},
  title = {Three-dimensional topological magnetic monopoles and their interactions in a ferromagnetic meta-lattice},
  abstract = {<p>Topological magnetic monopoles (TMMs), also known as hedgehogs or Bloch points, are three-dimensional (3D) non-local spin textures that are robust to thermal and quantum fluctuations due to the topology protection. Although TMMs have been observed in skyrmion lattices spinor Bose–Einstein condensateschiral magnets8, vortex rings and vortex cores10, it has been difficult to directly measure the 3D magnetization vector field of TMMs and probe their interactions at the nanoscale. Here we report the creation of 138 stable TMMs at the specific sites of a ferromagnetic meta-lattice at room temperature. We further develop soft X-ray vector ptycho-tomography to determine the magnetization vector and emergent magnetic field of the TMMs with a 3D spatial resolution of 10 nm. This spatial resolution is comparable to the magnetic exchange length of transition metals11, enabling us to probe monopole–monopole interactions. We find that the TMM and anti-TMM pairs are separated by 18.3 ± 1.6 nm, while the TMM and TMM, and anti-TMM and anti-TMM pairs are stabilized at comparatively longer distances of 36.1 ± 2.4 nm and 43.1 ± 2.0 nm, respectively. We also observe virtual TMMs created by magnetic voids in the meta-lattice. This work demonstrates that ferromagnetic meta-lattices could be used as a platform to create and investigate the interactions and dynamics of TMMs. Furthermore, we expect that soft X-ray vector ptycho-tomography can be broadly applied to quantitatively image 3D vector fields in magnetic and anisotropic materials at the nanoscale.</p>
},
  year = {2023},
  journal = {Nature Nanotechnology},
  volume = {18},
  pages = {227},
  month = {2023-01},
  publisher = {Springer Science and Business Media LLC},
  issn = {1748-3387, 1748-3395},
  doi = {10.1038/s41565-022-01311-0},
}