Strong Correlation Materials Research Team

We aim to obtain the enhanced cross-correlation response at higher temperatures with weaker magnetic field in strongly correlated electron systems, such as transition-metal oxides, in a bulk form. For that purpose, we synthesize materials with various techniques including high pressure synthesis. In particular, we discovered a new magnetic ferroelectric Sr_0.5Ba_0.5MnO₃ with magnetic off-center B-site ion, and revealed that this material possesses both large polarization value and strong coupling between polarization and magnetism. Also, we successfully observed magnetically induced atomic displacement for the first time for an orthorhombic YMnO₃ in which electric polarization is induced by symmetric exchange striction associated with E-type antiferromagnetic order. We also revealed the multiferroic properties of a long-wavelength cycroidal magnet NiBr₂ on a triangular lattice.

Research Fields

Physics / Engineering / Materials Sciences

Research Subjects

• Magnetotransport phenomena in non-trivial spin texture
• Charge-spin-orbital-lattice coupled system
• Exploration of novel thermoelectric materials

Publications

1. Y. Tokunaga, Y. Taguchi, T. Arima, and Y. Tokura,
   "Electric field induced generation and reversal of ferromagnetic moment in ferrites",
   Nature Physics Vol. 8, 838-844, November 2012, DOI：10.1038/NPHYS2405
2. H. Sakai, J. Fujioka, T. Fukuda, D. Okuyama, D. Hashizume, F. Kagawa, H. Nakao, Y. Murakami, T. Arima, A. Q. R. Baron, Y. Taguchi, and Y. Tokura
   "Displacement-Type Ferroelectricity with Off-Center Magnetic Ions in Perovskite Sr1-xBaxMnO3"
   Phys. Rev. Lett. 107, 137601 (2011).
3. K. Shibuya, D. Okuyama, R. Kumai, Y. Yamasaki, H. Nakao, Y. Murakami, Y. Taguchi, T. Arima, M. Kawasaki, and Y. Tokura
   "X-ray induced insulator-metal transition in a thin film of electron-doped VO2"
   Phys. Rev. B 84, 165108 (2011)
4. Y. Tokunaga, D. Okuyama, T. Kurumaji, T. Arima, H. Nakao, Y. Murakami, Y. Taguchi, and Y. Tokura
   "Multiferroicity in NiBr2 with long-wavelength cycloidal spin structure on a triangular lattice"
   Phys. Rev. B 84, 060406 (2011)
5. D. Okuyama, S. Ishiwata, Y. Takahashi, K. Yamauchi, S. Picozzi, K. Sugimoto, H. Sakai, M. Takata, R. Shimano, Y. Taguchi, T. Arima, and Y. Tokura
   "Magnetically driven ferroelectric atomic displacements in orthorhombic YMnO3"
   Phys. Rev. B 84, 054440 (2011)
6. S. Ishiwata, M. Tokunaga, Y. Kaneko, D. Okuyama, Y. Tokunaga, S. Wakimoto, K. Kakurai, T. Arima, Y. Taguchi, and Y. Tokura
   "Versatile helimagnetic phases under magnetic fields in cubic perovskite SrFeO3"
   Phys. Rev. B 84, 054427 (2011)
7. T. Suzuki, M. S. Bahramy, R. Arita, Y. Taguchi, and Y. Tokura
   Doping control and thermoelectric properties of R1-xAxZnSbO(R=La, Ce; A=Ca, Sr)
   Physica Reivew B, January 2011, Vol. 83, 035204-1 -- 035204-7
8. Y. Tokunaga, Y. Kaneko, D. Okuyama, S. Ishiwata, T. Arima, S. Wakimoto, K. Kakurai, Y. Taguchi, and Y. Tokura
   Multiferroic M-type hexaferrites with a room-temperature conical state and magnetically controllable spin helicity
   Physical Review Letters, December 2010, Vol. 105, 257201-1 - 257201-4
9. Y. Tokunaga, N Furukawa, H. Sakai, Y. Taguchi, T. Arima, and Y. Tokura
   Composite domain walls in a multiferroic perovskite ferrite
   Nature Materials, July 2009, Vol.8, 558-562
10. Ishiwata, S., Taguchi, Y., Murakawa, H., Onose, Y., and Tokura, Y.:
    Low-magnetic-field control of electric polarization vector in a helimagnet
    Science, 319, 1643-1646 (2008)