Quantum Nano-Scale Magnetism Research Team

Various domain structures such as magnetic vortices and single domains are formed in nano-scale magnets, depending on their shape and size. The magnetic vortices, for example, have two degrees of freedom, i.e., polarity and chirality, and allow us to design an artificial magnetic lattice called "magnonic crystal" consisting of several magnetic vortices. These are expected to be next-generation magnetic memory and logic devices. We fabricate nano-scale magnets to experimentally study their fundamental static and dynamic magnetic properties. We also use nano-scale magnets to produce "pure spin current" which transfers no electric charges but only spin angular momentums. By injecting the pure spin current into non-magnetic metals and superconductors, we are able to observe various interesting phenomena such as the spin Hall effect, the spin injection induced magnetization reversal, and the spin accumulation. We aim to study and develop new types of spintronic devices using the spin injection techniques.

Research Fields

Physics / Engineering / Materials Sciences

Research Subjects

• Study on the static and dynamic magnetic properties of nano-scale magnets
• Study on the spin-injection induced magnetization reversal and magnetic phase transition
• Study on the basic properties of nano-spintronic devices using potential ratchets
• Development of highly-polarized spin sources
• Study on the properties and generation techniques of spin currents

Publications

1. Y. Niimi, D. H. Wei, H. Idzuchi, T. Wakamura, T. Kato, and Y. Otani:
   "Experimental verification of comparability between spin-orbit and spin-diffusion lengths"
   Phys. Rev. Lett. 110, 016805-1~5 (2013).
2. Y. Niimi, Y. Kawanishi, D. H. Wei, C. Deranlot, H. X. Yang, M. Chshiev, T. Valet, A. Fert, and Y. Otani:
   "Giant spin Hall effect induced by skew scattering from Bismuth impurities inside thin film CuBi alloys"
   Phys. Rev. Lett. 109, 156602-1~5 (2012).
3. D. H. Wei, Y. Niimi, B. Gu, T. Ziman, S. Maekawa, and Y. Otani:
   "The spin Hall effect as a probe of nonlinear spin fluctuations"
   Nature Commun. 3, 1058-1~5 (2012).
4. H. Idzuchi, Y. Fukuma, and Y. Otani:
   "Towards coherent spin precession in pure-spin current"
   Scientific Reports 2, 628-1~5 (2012).
5. Y. Fukuma, L. Wang, H. Idzuchi, S. Takahashi, S. Maekawa, and Y. Otani:
   "Giant enhancement of spin accumulation and long-distance spin precession in metallic lateral spin valves"
   Nature Mater. 10, 527~531 (2011).
6. S. Sugimoto, Y. Fukuma, S. Kasai, T. Kimura, A. Barman, and Y. Otani:
   "Dynamics of coupled vortices in a pair of ferromagnetic disks"
   Phys. Rev. Lett. 106, 197203-1~4 (2011).
7. Y. Niimi, M. Morota, D. H. Wei, C. Deranlot, M. Basletic, A. Hamzic, A. Fert, and Y. Otani:
   "Extrinsic spin Hall effect induced by Iridium impurities in Copper"
   Phys. Rev. Lett. 106, 126601-1~4 (2011).
8. T. Yang, T. Kimura, and Y. Otani:
   "Giant spin-accumulation signal and pure spin-current-induced reversible magnetization switching"
   Nature Physics 4, 851~4 (2008).
9. L. Vila, T. Kimura, and Y. Otani:
   "Evolution of the spin Hall effect in Pt nanowires: Size and temperature effects"
   Phys. Rev. Lett. 99, 226604-1~4 (2007).
10. T. Kimura, Y. Otani, T. Sato, S. Takahashi, and S. Maekawa:
    "Room temperature reversible spin Hall effect"
    Phys. Rev. Lett. 98, 156601-1~4 (2007).