Emergent and topological properties of 3D chiral gyroid nanostructures

2021 Fiscal Year Research-status Report

• Project/Area Number: 21K04816
• Research Institution: Tohoku University
• Principal Investigator: LLANDRO Justin 東北大学, 電気通信研究所, 助教 (90784140)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: gyroids / spin waves / spin transport / topology / chiral

Outline of Annual Research Achievements

Nanoscale 3D networks made by block co-polymer templating allow independent control of the topological and material properties, leading to novel properties strongly influenced by nanostructural ordering and orientation. We optimized polymer preparation protocols which produce well-ordered Ni gyroid films with domains of a single orientation large enough to perform polarised small-angle-neutron scattering, which hints at a spin-liquid-like ground state. Our theoretical and experimental study of spin-wave propagation through such samples revealed non-reciprocal transmission due to the chiral nature of single-gyroid networks and a spin-wave spectrum strongly dependent on the orientation of the gyroid, paving the way towards tailoring of spin transport properties via 3D nanostructuring.

Current Status of Research Progress

1: Research has progressed more than it was originally planned.

Reason

We have put in place the experimental and theoretical framework to understand the effects of the gyroid network on spin-wave transport, and achieved control of ordering of gyroid networks using controlled solvent removal (solvent evaporation annealing) and pre-patterned substrates which direct the self-assembly of the polymer template, as set out in the first objective of our workplan. We are currently analysing the orientation dependence of the spin-wave spectrum and its relation to the highly inhomogeneous magnetization distribution in the gyroid network. We also obtained ptychographic X-ray computed tomography data which enables us to reconstruct the full 3D real-space morphology of our samples, giving unprecedented detail on extended defects in nanoscale networks.

Strategy for Future Research Activity

In FY2022-3, we aim to study topological effects in well-ordered samples which vary material composition (Ni, Ni-Fe) and chiral-axis orientations via directed self-assembly for single-gyroid samples. Angle-dependent magnetotransport will probe effects on electron transport such as the magnetochiral anisotropy and micro-focused Brillouin light scattering and co-planar waveguide FMR will probe spin-wave transport to assess magnonic crystal behaviour and existence of chiral edge modes. A further step will be to assess the impact of large-scale topological defects such as those observed in liquid crystals, which we can induce via local modification of the pre-patterned substrate.

Causes of Carryover

Due to the coronavirus pandemic, it was not possible to use travel expenses for the planned research visits to collaborators or intended overseas conferences. Infection prevention regulations also created manufacturing delays at suppliers of typically 8-12 months, so planned purchases of connectors and resistivity pucks for the magnetotransport measurements had to be postponed until the next fiscal year.

Research Products

• [Int'l Joint Research] Technical University of Kaiserslautern(ドイツ)
  • Country Name: GERMANY
  • Counterpart Institution: Technical University of Kaiserslautern
• [Int'l Joint Research] Adolphe Merkle Institute (AMI)/Paul Scherrer Institute (PSI)(スイス)
  • Country Name: SWITZERLAND
  • Counterpart Institution: Adolphe Merkle Institute (AMI)/Paul Scherrer Institute (PSI)
• [Int'l Joint Research] European Synchrotron Radiation Facility(フランス)
  • Country Name: FRANCE
  • Counterpart Institution: European Synchrotron Radiation Facility
• [Presentation] Geometrical and Magnetic Configuration of Self-organized 3D Gyroid Nanostructures (2021)
  • Author(s): J. Llandro, D. M. Love, A. Kovacs, J. Caron, K. N. Vyas, A. Kakay, M. R. J. Scherer, U. Steiner, C. H. W. Barnes, R. E. Dunin-Borkowski, J. Fassbender, S. Fukami, H. Ohno
  • Organizer: Highly Frustrated Magnetism Virtual School and Conference (wHFM21)
  • Int'l Joint Research
• [Presentation] Intricate Magnetic Configuration of 3D Nanoscale Gyroid Networks (2021)
  • Author(s): J. Llandro, D. M. Love, A. Kovacs, J. Caron, K. N. Vyas, A. Kakay, M. R. J. Scherer, U. Steiner, C. H. W. Barnes, R. E. Dunin-Borkowski, J. Fassbender, S. Fukami, H. Ohno
  • Organizer: The 4th International Symposium for The Core Research Cluster for Spintronics
  • Invited
• [Presentation] Small-angle neutron scattering of nanomagnetic gyroid structures (2021)
  • Author(s): N. Leo, A. S. Koshikawa, J. Llandro
  • Organizer: WE-Heraeus Seminar on “Magnetic Small Angle Neutron Scattering - from Nanoscale Magnetism to Long-Range Magnetic Structures”
  • Int'l Joint Research
• [Presentation] Intricate Magnetic Configuration of Self-assembled 3D Gyroid Nanostructures (2021)
  • Author(s): J. Llandro, D. M. Love, A. Kovacs, J. Caron, K. N. Vyas, A. Kakay, M. R. J. Scherer, U. Steiner, C. H. W. Barnes, R. E. Dunin-Borkowski, J. Fassbender, S. Fukami, H. Ohno
  • Organizer: WE-Heraeus Seminar on “Curvilinear Condensed Matter: Fundamentals and Applications”
  • Int'l Joint Research
• [Presentation] Small-angle neutron scattering of nanomagnetic gyroid structures (2021)
  • Author(s): N. Leo, A. S. Koshikawa, J. Llandro
  • Organizer: WE-Heraeus Seminar on “Curvilinear Condensed Matter: Fundamentals and Applications”
  • Int'l Joint Research
• [Presentation] Burning cups and donuts: what coherent X-rays can reveal about topological defects (2021)
  • Author(s): D. Karpov, J. Llandro, E. Fohtung
  • Organizer: IUCR-XXV
  • Int'l Joint Research