Strong Correlation Materials Research Group

Principal Investigator

PI Name Yasujiro Taguchi
Degree D.Eng.
Title Group Director
Brief Resume
1993Researcher, SONY Corporation
1997Research Associate, University of Tokyo
2002D.Eng., University of Tokyo
2002Associate Professor, Institute for Materials Research, Tohoku University
2007Team Leader, Exploratory Materials Team, RIKEN
2010Team Leader, Strong-Correlation Materials Research Team, RIKEN
2013Team Leader, Strong Correlation Materials Research Team, Strong Correlation Physics Division, RIKEN Center for Emergent Matter Science
2018Group Director, Strong Correlation Materials Research Group, Strong Correlation Physics Division, RIKEN Center for Emergent Matter Science (-present)
2018Director, Office of the Center Director, RIKEN Center for Emergent Matter Science (-present)

Outline

Our group aims at obtaining gigantic cross-correlation responses, understanding their mechanisms, and developing new functions in strongly-correlated-electron bulk materials, such as transition-metal oxides. To this end, we try to synthesize a wide range of materials using various methods, including high-pressure techniques, and investigate their physical properties. Specific targets are: (1) exploration of new skyrmion materials; (2) obtaining gigantic magnetoelectric responses in mutiferroic materials at high temperatures; (3) exploration of new magnetic semiconductors; (4) exploration of new thermoelectric materials; and (5) exploration of new superconductors.

Research Fields

Physics, Engineering, Materials Science

Keywords

Strongly correlated electron system
Skyrmion
Multiferroics
Thermoelectric effect
Superconductivity

Results

Discovery of new magnet hosting antiskyrmions at room temperature

Skyrmion is a nanometric magnetic vortex characterized by an integer topological number, which behaves as a stable particle, and anticipated to be applied to high-performance magnetic memory devices. Recently, a new magnetic vortex, antiskyrmion, with the opposite sign of the topological number has attracted much attention. However, antiskyrmions have thus far been observed only in Heusler compounds with D2d symmetry. This limitation has prevented intensive studies of topological properties of antiskyrmions and their applications. Our group discovered a Pd-doped Schreibersite, Fe1.9Ni0.9Pd0.2P, with S4 symmetry to host antiskyrmions over a wide temperature range including room temperature. It was also found that antiskyrmions and skyrmions are interconverted to each other by changing magnetic fields or sample thickness. Furthermore, sawtooth-like novel magnetic domain patterns with S4 symmetry were observed near the surface of thick crystals.

Schematics of (a) skyrmion, (b)antiskyrmion, and (c) symmetry of the crystal structures hosting antiskyrmions.

 

Room-temperature skymion and transformation of skymion-lattice in metastable state

Skyrmion is a magnetic vortex with a nano-meter size which behaves as a topologically protected stable particle, and anticipated to be applied to high-performance magnetic memory devices. However, chiral-skyrmion formation has been observed only below 280 K thus far, and new materials that exhibit skyrmions at higher temperatures have been desired from the viewpoint of applications. Recently, our team discovered a Co-Zn-Mn alloy system with a cubic and chiral, b-Mn type structure that exhibits skyrmion-lattice at and above room temperature. Furthermore, it was found that the skyrmion lattice persists as a metastable state in a very wide range of temperature and magnetic field when cooled down from the thermally equilibrium phase in the applied magnetic field. It was also discovered that the skyrmion lattice undergoes a transformation from a conventional triangular lattice to a novel square lattice during the field-cooling process.

Transformation of skyrmion-latice.

Members

Yasujiro Taguchi

Group Director y-taguchi[at]riken.jp R
Markus Wilhelm Bernhard Kriener Senior Research Scientist markus.kriener[at]riken.jp R
Kosuke Karube Research Scientist kosuke.karube[at]riken.jp R
Daisuke Nakamura Research Scientist daisuke.nakamura.rg[at]riken.jp R
Akiko Kikkawa Technical Scientist kikkawa[at]riken.jp R

Publications

  1. K. Karube, L. C. Peng, J. Masell, X. Z. Yu, F. Kagawa, Y. Tokura, and Y. Taguchi

    Room-temperature antiskyrmions and sawtooth surface textures in a non-centrosymmetric magnet with S4 symmetry

    Nat. Mater. 20, 335 (2021)
  2. M. Kriener, M. Sakano, M. Kamitani, M. S. Bahramy, R. Yukawa, K. Horiba, H. Kumigashira, K. Ishizaka, Y. Tokura, and Y. Taguchi

    Evolution of Electronic States and Emergence of Superconductivity in the Polar Semiconductor GeTe by Doping Valence-Skipping Indium

    Phys. Rev. Lett. 124, 047002 (2020)
  3. A. Doi, S. Shimano, D. Inoue, T. Kikitsu, T. Hirai, D. Hashizume, Y. Tokura, and Y. Taguchi

    Band engineering carrier density control and enhanced thermoelectric performance in multi-doped SnTe

    APL Mater. 7, 091107 (2019)
  4. V. Kocsis, T. Nakajima, M. Matsuda, A. Kikkawa, Y. Kaneko, J. Takashima, K. Kakurai, T. Arima, F. Kagawa, Y. Tokunaga, Y. Tokura, and Y. Taguchi

    Magnetization-polarization cross-control near room temperature in hexaferrite single Crystals

    Nat. Commun. 10, 1247 (2019)
  5. K. Karube, J. S. White, D. Morikawa, C. D. Dewhurst, R. Cubitt, A. Kikkawa, X. Yu, Y. Tokunaga, T.-h. Arima, H. M. Ronnow, Y. Tokura, and Y. Taguchi

    Disordered skyrmion phase stabilized by magnetic frustration in a chiral magnet

    Sci. Adv. 4, aar7043 (2018)

Articles

お問い合わせ

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

E-mail:
y-taguchi[at]riken.jp

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