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Yusuke Tokunaga / Associate Professor / Division of Transdisciplinary Sciences
Department of Advanced Materials Science / / Strongly correlated electron system, Condensed-matter physics
http://symm.k.u-tokyo.ac.jp/

Career Summary
2000: B. Eng., Department of Applied Physics, Faculty of Engineering (University of Tokyo)
2005: Ph.D. (Eng.) (University of Tokyo)
2005: Researcher, ERATO Tokura Spin Superstructure Project, JST
2007: Researcher, ERATO Tokura Multiferroics Project, JST
2011: ASI Research Scientist, Advanced Science Institute (ASI), RIKEN
2013: Senior Research Scientist, RIKEN Center for Emergent Matter Science (CEMS)
2014: Associate Professor (Department of Advanced Materials Science, University of Tokyo)


Educational Activities

Research Activities
We are studying strongly correlated electron systems that show gigantic cross-correlated responses, including magnetoelectric multiferroics.
We are also searching for new magnetic materials that host magnetic skyrmions and examining the emergent electromagnetic responses.

Literature
1) "Rotation of orbital stripes and the consequent charge-polarized state in bilayer manganites", Y. Tokunaga, Th. Lottermoser, Y. S. Lee, R. Kumai, M. Uchida, T. Arima, and Y. Tokura, Nat. Mater. 5, 937 (2006).
2) "Change in optical anisotropy with rotation of orbital stripe in a half-doped bilayer manganite", Y. S. Lee, Y. Tokunaga, T. Arima, and Y. Tokura, Phys. Rev. B 75, 174406 (2007).
3) "Versatile and competing spin-charge-orbital orders in the bilayered manganite system Pr(Sr1-yCay)2Mn2O7", Y. Tokunaga, T. J. Sato, M. Uchida, R. Kumai, Y. Matsui, T. Arima, and Y. Tokura, Phys. Rev. B 77, 064428 (2008).
4) "Effects of uniaxial stress on orbital stripe direction in half doped layered manganites: Eu0.5Ca1.5MnO4 and Pr(Sr, Ca)2Mn2O7", Y. Tokunaga, R. Kumai, N. Takeshita, Y. Kaneko, J. P. He, T. Arima, and Y. Tokura, Phys. Rev. B 78, 155105 (2008).
5) "Lattice-form-dependent orbital shape and charge disproportionation in charge- and orbital-ordered manganites", D. Okuyama, Y. Tokunaga, R. Kumai, Y. Taguchi, T. Arima, and Y. Tokura, Phys. Rev. B 80, 064402 (2009).
6) "Charge-ordering-induced polar domains and domain walls in a bilayered manganite Pr(Sr0.15Ca0.85)2Mn2O7", H. Itoh, Y. Tokunaga, N. Kida, R. Shimano, and Y. Tokura, Appl. Phys. Lett. 96, 032902 (2010).
7) "Magnetic-Field-Induced Ferroelectric State in DyFeO3", Y. Tokunaga, S. Iguchi, T. Arima, and Y. Tokura, Phys. Rev. Lett. 101, 097205 (2008).
8) "Composite domain walls in a multiferroic perovskite ferrite", Y. Tokunaga, N. Furukawa, H. Sakai, Y. Taguchi, T. Arima, and Y. Tokura, Nat. Mater. 8, 558 (2009).
9) "Above-room-temperature ferroelectricity in a single-component molecular crystal", S. Horiuchi, Y. Tokunaga, G. Giovannetti, S. Picozzi, H. Itoh, R. Shimano, R. Kumai, and Y. Tokura, Nature 463, 789 (2010).
10) "Multiferroic M-type hexaferrites with a room-temperature conical state and magnetically controllable spin helicity", Y. Tokunaga, Y. Kaneko, D. Okuyama, S. Ishiwata, T. Arima, S. Wakimoto, K. Kakurai, Y. Taguchi, and Y. Tokura, Phys. Rev. Lett. 105, 257201 (2010).
11) "High-Pressure Hydrothermal Crystal Growth and Multiferroic Properties of a Perovskite YMnO3", S. Ishiwata, Y. Tokunaga, Y. Taguchi, and Y. Tokura, J. Am. Chem. Soc. 133, 13818 (2011).
12) "Multiferroicity in an orthorhombic YMnO3 single-crystal film", M. Nakamura, Y. Tokunaga, M. Kawasaki, and Y. Tokura, Appl. Phys. Lett. 98, 082902 (2011).
13) "Electric-field-induced generation and reversal of ferromagnetic moment in ferrites", Y. Tokunaga, Y. Taguchi, T. Arima, and Y. Tokura, Nat. Phys. 8, 838 (2012).
14) "Magnetic Biasing of a Ferroelectric Hysteresis Loop in a Multiferroic Orthoferrite", Y. Tokunaga, Y. Taguchi, T. Arima, and Y. Tokura, Phys. Rev. Lett. 112, 037203 (2014).
15)gUniaxial-Stress Control of Spin-Driven Ferroelectricity in Multiferroic Ba2CoGe2O7h, T. Nakajima, Y. Tokunaga, Y. Taguchi, Y. Tokura, and T. Arima, Phys, Rev. Lett. 114, 167201 (2015).
16) "Magnetic stripes and skyrmions with helicity reversals", X. Yu, M. Mostovoy, Y. Tokunaga, W. Zhang, K. Kimoto, Y. Matsui, Y. Kaneko, N. Nagaosa, and Y. Tokura, Proc. Nat. Acad. Sci. 109, 8856 (2012).
17) "Biskyrmion states and their current-driven motion in a layered manganite", X. Z. Yu, Y. Tokunaga, Y. Kaneko, W. Z. Zhang, K. Kimoto, Y. Matsui, Y. Taguchi and Y. Tokura, Nat. Commun. 5, 3198 (2014).

Other Activities
Member of the American Physical Society and the Physical Society of Japan
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Future Plan
To search for new functional materials.
Messages to Students
Every failure is a stepping stone to success. Let's just do it.
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