Research Interests

Fig.1. Ferroelectricity is induced by a helical magnetic structure for CuO2 ribbon chains.(multiferroic behavior)

The discovery of new physical phenomena and new materials is on the frontier of condensed matter physics, which provides an important basis for current electronic and information technology research. The search for new materials with interesting physical properties is one of the most exciting and important projects. I am exploring the physical properties of strongly correlated electron systems, including transition metal oxides and rare earth ones. My research interest lies in the wide variety of physical phenomena in strongly correlated electron systems: new quantum phenomena, Mott metal-insulator transition, superconductors, magnetic frustration, quantum spin magnets, non-trivial magnetic structure, and multiferroic behavior (magnetic and ferroelectric transitions coexist: see Fig.1). Yasui group experimentally investigates these fields by means of the following methods. (i) Synthesize the polycrystalline and single crystal samples of transition metal and rare earth oxides (ceramic). (ii) Measure the magnetic, transport, heat, and dielectric properties in wide-temperature and magnetic-field regions. (iii) Identify the magnetic structure by neutron diffraction, directly observe the microscopic dynamics by inelastic neutron scattering, and analyze the crystal structure by synchrotron radiation X-ray diffraction.

Selected Publications

1. Y. Yasui, M. Sato, and I. Terasaki, “Multiferroic behavior in the quasi one-dimensional frustrated spin-1/2 system PbCuSO₄(OH)₂ with CuO₂ ribbon chains”, J. Phys. Soc. Jpn. 80 No. 3, 033707 (1-4), (2011).
2. Y. Yasui, K. Sato, Y. Kobayashi, and M. Sato, “Studies of Multiferroic System LiCu₂O₂: I. Sample Characterization and Relationship between Magnetic Properties and Multiferroic Nature”, J. Phys. Soc. Jpn. 78, No. 8, 084720 (1-5), (2009).
3. Y. Yasui, Y. Naito, K. Sato, T. Moyoshi, M. Sato and K. Kakurai, “Relationship between Magnetic Structure and Ferroelectricity of LiVCuO₄”, J. Phys. Soc. Jpn. 77, No. 2, 023712 (1-4), (2008).
4. Y. Yasui, Y. Kobayashi, M. Soda, T. Moyoshi, M. Sato, N. Igawa and K. Kakurai, “Successive Magnetic Transition of the Kagomé Staircase Compound Co₃V₂O₈ Studied in Various Magnetic Fields”, J. Phys. Soc. Jpn. 76, No. 3, 034706 (1-8), (2007).
5. Y. Yasui, T. Kageyama, T. Moyoshi, M. Soda, M. Sato and K. Kakurai, “Studies of the Anomalous Hall Effect and Magnetic Structure of Nd₂Mo₂O₇ –Test of the Chirality Mechanism–”, J. Phys. Soc. Jpn. 75, No. 8, 084711 (1-11), (2006).
6. Y. Yasui, M. Kanada, M. Ito, H. Harashina, M. Sato, H. Okumura, K. Kakurai and H. Kadowaki, “Static Correlation and Dynamical Properties of Tb³⁺-moments in Tb₂Ti₂O₇ –Neutron Scattering Study–”, J. Phys. Soc. Jpn. 71, No.2 599-606, (2002).
7. Y. Yasui, H. Sasaki, M. Sato, M. Ohashi, Y. Sekine, C. Murayama and N. Mori, “Studies of Pressure-Induced Mott Metal-Insulator Transition of BaCoS₂”, J. Phys. Soc. Jpn. 68, No.4, 1313-1320, (1999).