Abstract
Magnetic skyrmions exhibit unique, technologically relevant pseudo-particle behaviors which arise from their topological protection, including well-defined, 3D dynamic modes that occur at microwave frequencies. During dynamic excitation, spin waves are ejected into the interstitial regions between skyrmions, creating the magnetic equivalent of a turbulent sea. However, since the spin waves in these systems have a well-defined length scale, and the skyrmions are on an ordered lattice, ordered structures from spin-wave interference can precipitate from the chaos. This work uses small-angle neutron scattering (SANS) to capture the dynamics in hybrid skyrmions and investigate the spin-wave structure. Performing simultaneous ferromagnetic resonance and SANS, the diffraction pattern shows a large increase in low-angle scattering intensity, which is present only in the resonance condition. This scattering pattern is best fit using a mass fractal model, which suggests the spin waves form a long-range fractal network. The fractal structure is constructed of fundamental units with a size that encodes the spin-wave emissions and are constrained by the skyrmion lattice. These results offer critical insights into the nanoscale dynamics of skyrmions, identify a new dynamic spin-wave fractal structure, and demonstrate SANS as a unique tool to probe high-speed dynamics.
Original language | English |
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Article number | 2300416 |
Journal | Advanced Materials |
Volume | 35 |
Issue number | 33 |
DOIs | |
State | Published - Aug 17 2023 |
Funding
Student support, travel, materials, and the high‐frequency equipment were supported by the U.S. Department of Energy, Office of Science, Office of Basic Research Early Career program under Award Number DE‐SC0021344. Work at UC San Diego was supported by the National Science Foundation, Division of Materials Research Award #: 2105400. The authors appreciate the assistance of the sample environment team at NIST, especially Alan Ye, the instrument team, notably John Barker, Jeff Krzywon, and Cedric Gagnon, and Dan Neumann for insightful discussion. Access to vSANS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR‐2010792 and DMR‐1508249. Support for L.J.Q. was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR‐2010792. S.A.M. acknowledges the support from the U. S. Office of Naval Research, In‐House Laboratory Independent Research. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Student support, travel, materials, and the high-frequency equipment were supported by the U.S. Department of Energy, Office of Science, Office of Basic Research Early Career program under Award Number DE-SC0021344. Work at UC San Diego was supported by the National Science Foundation, Division of Materials Research Award #: 2105400. The authors appreciate the assistance of the sample environment team at NIST, especially Alan Ye, the instrument team, notably John Barker, Jeff Krzywon, and Cedric Gagnon, and Dan Neumann for insightful discussion. Access to vSANS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-2010792 and DMR-1508249. Support for L.J.Q. was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-2010792. S.A.M. acknowledges the support from the U. S. Office of Naval Research, In-House Laboratory Independent Research. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.
Keywords
- magnetic dynamics
- skyrmions
- small-angle neutron scattering
- spin waves