Shinichiro Yano

Chiral Magnetic Ordering and Commensurate-to-Incommensurate Transition in CuB2O4

We measured the anisotropic magnetization processes of copper metaborate CuB 2 O 4 in detail. We propose an interpretation of the magnetization anomaly observed under the magnetic field applied perpendicular to the tetragonal axis, based on the field- and temperature-induced commensurate-to-incommensurate (C–IC) transition (Freedericksz transition) accompanied by the chiral soliton lattice formation.

Quantum Renormalization Effect in One-Dimensional Heisenberg Antiferromagnets

The dispersion relations of the lowest magnetic excitations at low temperatures and the temperature dependence of the inverse magnetic correlation length were determined using inelastic pulsed neutron scattering experiments on the following one-dimensional Heisenberg antiferromagnets: CsVCl 3 ( S = 3/2), CsVBr 3 ( S = 3/2), CsCrCl 3 ( S = 2), and CsNiCl 3 ( S = 1). From studying the exchange constant, J , it has been found that the observed energies of the magnetic excitations require a quantum renormalization factor that is dependent on the spin quantum number, S . The values of J were determined from the temperature dependence of the inverse magnetic correlation length, which describes the static correlation function that can be deduced from the energy-integrated dynamical structure factor. We demonstrated that the S -dependent quantum renormalization effect was detected by only inelastic pulsed neutron scattering experiments, and that the effect was consistent with quantum Monte Carlo calculations.

Science from the Initial Operation of HRC

Shinichi Itoh1, Tetsuya Yokoo1, Takatsugu Masuda2, Hideki Yoshizawa2, Minoru Soda2, Yoichi Ikeda2, Soshi Ibuka1, Daichi Kawana1, Taku J. Sato3, Yusuke Nambu3, Keitaro Kuwahara4, Shin-ichiro Yano5, Jun Akimitsu5, Yoshio Kaneko6, Yoshinori Tokura6,7, Masaki Fujita8, Masashi Hase9, Kazuaki Iwasa10, Haruhiro Hiraka1, Tatsuo Fukuda11, Kazuhiko Ikeuchi12, Koji Yoshida13 Toshio Yamaguchi13, Kanta Ono1, Yasuo Endoh1,6,8 1Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan 2The Institute for Solid State Physics, The University of Tokyo, Tokai 319-1106, Japan 3Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan 4Institute of Applied Beam Science, Ibaraki University, Mito 310-8512, Japan 5Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara 252-5258, Japan 6RIKEN Center for Emergent Matter of Science, Wako 351-0198, Japan 7Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan 8Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan 9National Institute for Materials Science, Tsukuba 305-0047, Japan 10Department of Physics, Tohoku University, Sendai 980-8578, Japan 11Quantum Beam Science Center, Japan Atomic Energy Agency, Sayo 679-5148, Japan 12Comprehensive Research Organization for Science and Society, Tokai 319-1106, Japan 13Department of Chemistry, Fukuoka University, Fukuoka 814-0180, Japan

Intertwining of Frustration with Magneto-Elastic Coupling in the Multiferroic LuMnO3

Residual magnetic frustration in the multiferroic LuMnO3 may be key towards understanding magneto-elastic coupling in hexagonal manganites. Critical magnetic scattering present well above the magnetic ordering temperature TN persists below, as observed by inelastic neutron scattering. The magnetic fluctuations are confined in two dimensions implied by the characteristic wavevector dependence of the magnetic structure factor that changes from symmetric to asymmetric across TN. The low dimensionality of the magnetic structure is also evident in the temperature dependence of the commensurate antiferromagnetic intensity which follows a mean field exponent of β ∼ 0.2.

Magnetic excitations in MnP

We performed inelastic neutron scattering experiments on a three-dimensional magnetic system MnP, which is a ferromagnetic inter-metallic compound below TC = 291 K and transitions into a screw state at T* = 47 K. Using newly developed high resolution chopper spectrometer (HRC) and triple axis spectrometer LTAS (for E = 0?2 meV), 6G (for E = 2?8 meV) TAS1 (for E = 10-35 meV), we succeeded in observing the excitations from low energy to Brillouin zone center. We assumed isotropic 6 exchange parameters, and calculated dispersion relation using Heisenberg model for 2-sub lattices. We confirm that nearest neighbor (n.n) exchange parameters Jm are J > 0 (ferromagnetic interaction), the next nearest neighbor (n.n.n) exchange parameters are J < 0 (anti-ferromagnetic interaction), We conclude that the competition between n.n and n.n.n would be the cause of helimagnetic structure in MnP.

Magnetic structure of Ba2Mg2Fe12O22 under the magnetic field

Ba2Mg2Fe12O22 has a strong coupling between electric polarization P and magnetization M. To understand the multiferroic properties of the system, we performed crystal structural and precise magnetic structural analyses of Ba2 Mg2Fe12O22 under a magnetic field (T = 4K, H = 0.3T) using 4 circle neutron diffractometer (FONDER) at JRR-3M Tokai. We collected 105 points of magnetic scattering for q = (0,0, 3/2) and over 150 points of fundamental scattering which contains ferri magnetic component. Using the part of these data, we reinvestigate magnetic struture of Ba2Mg2Fe12O22, in which 14 (Mg,Fe) sites have been included.