Strong Correlation Quantum Structure Research Group

Principal Investigator

PI Name Takahisa Arima
Degree Ph.D.
Title Group Director
Brief Resume
1988 TORAY Co. Ltd.
1991 Research Associate, Faculty of Science, University of Tokyo
1994 Ph.D. (Science), University of Tokyo
1995 Research Associate, Graduate School of Engineering, University of Tokyo
1995 Associate Professor, Institute of Materials Science, University of Tsukuba
2001 Group Leader, ERATO Tokura Spin Super Structure Project (-2006)
2004 Professor, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
2011 Professor, Graduate School of Frontier Sciences, University of Tokyo (-present)
2007 Team Leader, Spin Order Research Team, RIKEN SPring-8 Center (-2014)
2013 Team Leader, Strong Correlation Quantum Structure Research Team, RIKEN Center for Emergent Matter Science
2023 Deputy Director, RIKEN Center for Emergent Matter Science (CEMS)
2023 Group Director, Strong Correlation Quantum Structure Research Group, RIKEN Center for Emergent Matter Science (-present)
2024 Director, RIKEN Center for Emergent Matter Science (CEMS) (-present)


Strongly correlated electron systems may exhibit various interesting emergent phenomena such as superconductivity, colossal magneto-resistance, and giant magneto-electric effects. These emergent phenomena are directly associated with the spatial distributions as well as the spatial and temporal fluctuations of atoms, electron density, and spin density. To reveal these phenomena, we perform crystallographic and magnetic structure analyses, spectroscopies, and microscopies by using synchrotron x-rays, neutrons, and high-energy electron beams.

Research Fields

Materials Science, Physics


X-ray scattering
Neutron scattering
Electron diffraction
Structure science


Spin-driven Ferroelectricity and Electromagnon in Multiferroic Y-type Hexaferrite Compounds

Y-type hexaferrite compounds are composed of an alternate stacking of spinel block layers and hexagonal perovskite block layers.  The magnetic anisotropy of each layer and effective exchange interaction are dependent on the composition.  As a consequence, various magnetic orders appears in the temperature-magnetic field plane.  It is predicted that two kinds of magnetic orders, transverse cone and double fan, can host electric polarization via the inverse Dzyalloshinsky-Moriya interaction.  We performed measurements of magnetization, electric polarization, and spin-polarized neutron scattering in BaSrCo2Fe11AlO22.  It has been found that the alternate longitudinal cone first appears by cooling from a high temperature at zero magnetic field.  If a magnetic field is once applied perpendicular to the c-axis at low temperatures, the double fan replaces and survives even after the magnetic field is turned off.  The electric polarization is also induced along the axis perpendicular both to the c-axis and to the magnetic field.  The electric polarization is reversed by switching the magnetic field direction.  Inelastic spin-polarized neutron scattering has predicted that both the double fan and alternative longitudinal cone may host an electromagnon (magnon excited by THz electric field).


Magnetic-field induced reversal of electric polarization and possible change in magnetic structure in a Y-type hexaferrite BaSrCo2Fe11AlO22.


Takahisa Arima

Group Director takahisa.arima[at]

Masaki Gen

Special Postdoctoral Researcher

Kamini Gautam

Postdoctoral Researcher


  1. M. Gen, H. Ishikawa, A. Miyake, T. Yajima, H. O. Jeschke, H. Sagayama, A. Ikeda, Y. H. Matsuda, K. Kindo, M. Tokunaga, Y. Kohama, T. Kurumaji, Y. Tokunaga, T. Arima

    Breathing pyrochlore magnet CuGaCr4S8: Magnetic, thermodynamic, and dielectric properties

    Phys. Rev. Mater. 7, 104404 (2023)
  2. S. Kitou, M. Gen, Y. Nakamura, K. Sugimoto, Y. Tokunaga, S. Ishiwata, and T.-h. Arima

    Real-Space Observation of Ligand Hole State in Cubic Perovskite SrFeO3

    Adv. Sci. 10, 2302839 (2023)
  3. T. Nakajima, T. Oda, M. Hino, H. Endo, K. Ohishi, K. Kakurai, A. Kikkawa, Y. Taguchi, Y. Tokura, T. Arima

    Crystallization of magnetic skyrmions in MnSi investigated by neutron spin echo spectroscopy

    Phys. Rev. Research 2, 043393 (2020)
  4. V. Ukleev, Y. Yamasaki, O. Utesov, K. Shibata, N. Kanazawa, N. Jaouen, H. Nakao, Y. Tokura, and T.-h. Arima

    Metastable solitonic states in the strained itinerant helimagnet FeGe

    Phys. Rev. B 102, 014416 (2020)
  5. S. Gao, D. Hirai, H. Sagayama, H. Ohsumi, Z. Hiroi, and T.-h. Arima

    Antiferromagnetic long-range order in the 5d1 double-perovskite Sr2MgReO6

    Phys. Rev. B 101, 220412 (2020)



2-1 Hirosawa, Wako, Saitama 351-0198 Japan