TY - JOUR KW - Electrical and Electronic Engineering KW - Condensed Matter Physics KW - General Materials Science KW - Biomedical Engineering KW - Atomic and Molecular Physics, and Optics KW - Bioengineering AU - Arjun Rana AU - Chen-Ting Liao AU - Ezio Iacocca AU - Ji Zou AU - Minh Pham AU - Xingyuan Lu AU - Emma-Elizabeth Subramanian AU - Yuan Lo AU - Sinéad Ryan AU - Charles Bevis AU - Robert Karl AU - Andrew Glaid AU - Jeffrey Rable AU - Pratibha Mahale AU - Joel Hirst AU - Thomas Ostler AU - William Liu AU - Colum O’Leary AU - Young-Sang Yu AU - Karen Bustillo AU - Hendrik Ohldag AU - David Shapiro AU - Sadegh Yazdi AU - Thomas Mallouk AU - Stanley Osher AU - Henry Kapteyn AU - Vincent Crespi AU - John Badding AU - Yaroslav Tserkovnyak AU - Margaret Murnane AU - Jianwei Miao AB -

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.

BT - Nature Nanotechnology DA - 2023-01 DO - 10.1038/s41565-022-01311-0 N2 -

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.

PB - Springer Science and Business Media LLC PY - 2023 EP - 227 T2 - Nature Nanotechnology TI - Three-dimensional topological magnetic monopoles and their interactions in a ferromagnetic meta-lattice VL - 18 SN - 1748-3387, 1748-3395 ER -