Tokunaga, Masashi
Associate Professor
International MegaGauss Science Laboratory
University of Tokyo
Japan
Biography
Magnetic fields have been extensively used in broad research fields of solid state physics because they can directly tune the spins, orbitals and phases of electrons in materials. We study various kinds of phase transitions in high magnetic fields with using non-destructive pulse magnets and developing/up-grading various experimental techniques; e.g. magnetization, magnetoresistance, electric polarization, polarizing optical microscopy, and so on. As one of our recent projects, we focus on the electronic states in the quantum limit state. Since charge carriers are confined in the smallest cyclotron orbit, Coulomb interaction dominates over the kinetic energy. Therefore, we can realize strongly correlated electron systems in the quantum limit states. In particular, we have been focusing on the semimetals having even number of electrons and holes, and found a novel field-induced phase in graphite and anomalous quantum transport properties in black phosphorus under multiple extreme conditions. We are also studying multiferroic materials using high precision experiments realized in pulsed-fields. We found a field-induced novel multiferroic phase in a triangular lattice chiral antiferromagnet CsCuCl3 and bipolar resistive memory effects in a room temperature multiferroic material BiFeO3. In addition to these in-house studies, we accept about 40 joint research projects per year and study various localized/itinerant magnets and topological materials in high magnetic fields.
Research Interest
Field-induced transitions in multiferroic materials Electronic phase transitions in the quantum limit state High-speed polarizing microscope imaging in pulsed-high magnetic fields High-field study of topological materials
Publications
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Rich magnetoelectric phase diagrams of multiferroic single-crystal α−NaFeO2: N. Terada, Y. Ikedo, H. Sato, D. D. Khalyavin, P. Manuel, A. Miyake, A. Matsuo, M. Tokunaga and K. Kindo, Phys. Rev. B 96 (2017) 035128(1-14).
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Magnetic transitions under ultrahigh magnetic fields of up to 130 T in the breathing pyrochlore antiferromagnet LiInCr4O8: Y. Okamoto, D. Nakamura, A. Miyake, S. Takeyama, M. Tokunaga, A. Matsuo, K. Kindo and Z. Hiroi, Phys. Rev. B 95 (2017) 134438(1-5).
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Electric Polarization Induced by Spin Ordering under Magnetic Fields in Distorted Triangular Lattice Antiferromagnet RbCoBr3: Y. Nishiwaki, M. Tokunaga, R. Sakakura, S. Takeyama, T. Kato and K. Iio, J. Phys. Soc. Jpn. 86 (2017) 044701(1-7).
