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中性子科学について
Neutron Science Lab.
中性子科学研究施設の紹介
トップ  >  Neutron Science Lab.  >  施設の研究室

Link to Laboratory HPs

In NSL, 4 laboratories run with educating master and doctor course students as the collaborative courses such as Depts. of Physics and Chemistry, Grad. School of Science, Dept. of Applied Physics, Grad. School of Engineering and Dept. of Advanced Materials Science, School of Frontier Science, UTokyo.

 

Yoshizawa Lab.

Metal-insulator transition in transition-metal oxides has drawn much attention because such a phenomenon reflects interplay among spin, charge, lattice, and orbital degrees of freedom. Our group has been studying their behavior by neutron scattering technique with use of pulse and steady-source neutron beams, and the triple axis neutron spectrometer owned by the ISSP is shown in the below figure.

The hole-doping dependences of the incommensurability and the transition temperature of the stripe ordering for the hole concentration x up to x = 0.5 have been observed in the highly-doped La2-xSrxNiO4 which is one of the isomorphic compounds of the High-T&size(10){c} cuprate superconductors. The ordering temperatures of the stripe charge as well as spin orderings have the maxima at x= 1/3, and they decrease beyond x = 1/3. Beyond x=1/2, the Ni system gradually becomes metallic and shows the insulator to metal transition at x~0.9. Recent pulse neutron studies on Ni and Co systems revealed that the unusual hour-glass type spin excitations exist in these 2 dimensional transition metal oxides, and our group is studying such unusual spin dynamics and their relation to the transport properties with using pulse and reactor-source inelastic neutron spectrometers.

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(top) Triple-axis spectrometer installed at the JRR-3 in the Japan Atomic Energy Agency, Tokai, Ibaraki.


(right) Doping dependence of the stripe ordering in highlydoped La2-xSrxNiO4, which is an isomorphic compounds of one of High Tc cuprate superconductors La2-xSrxCuO4. Unlike the expectation from the previous studies, the transition temperatures of the stripe charge and spin orderings exhibit the maximums at x = 1/3, and decreases above x=1/3. The periodicity of the stripe order is approximately linear in x, but levels off beyond x=1/2. The system gradually becomes metallic and shows the insulator to metal transition near x~0.9.

 

Shibayama Lab.

Soft matter undergoes various transitions in response to a slight change of an environmental variable. We investigate the relationship of the structure and dynamics of soft matter, such as polymer gels, nanoemulsion, and micelles. The aims of our research are systematization of “molecular-bond correlated systems”. Concurrently, we explore various applications of soft matter on the basis of the physics of soft matter. Recently, we are developing various types of super-tough gels on the basis of findings on the structure-property relationship unveiled by neutron scattering.

Nano-order structure investigations and studies on dynamics of soft matter are carried out with state-of-the-art equipments, SANS-U, a small-angle neutron scattering instrument (upgraded in 2010). Other techniques, such as dynamic/static light scattering, microscopy, mechanical/thermal analyses, and rheological studies, are also employed if necessary. Current interests cover (1) inhomogeneities in polymer gels, (2) structural characterization and studies on deformation mechanisms of high-performance polymer gels, (3) rheo-SANS of nanoemulsion and micelles, and (4) development of ion-gel and structural analyses.

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Variation of SANS proles for star-type trimeric surfactant in aqueous solution with varying volume fractions. With increasing surfactant concentration, micelles are transformed from spherical to wormlike micelles, followed by entangled rodlike micelles.Temperature dependence of SANS profiles of pNIPAm/ionic liquid solutions. By lowering temperature, the system undergoes phase separation (UCST type behavior), which is opposite to pNIPAm/water systems (LCST).

 

Yamamuro Lab.

We are studying chemical physics of complex condensed matters, especially glasses and supercooled liquids, water and related materials, ionic liquids, hydrogen storage solids and single molecule magnets (SMMs). Glass transition is a mysterious phenomenon in which liquids solidify without structural change. This is one of big and long-standing issues in physics. Water, which is the most familiar material for us, exhibits various unique phenomena caused by hydrogen bonds. Ionic liquids have many interesting properties originating from competing electrostatic and van der Waals interactions. Hydrogen in solids exhibits classical and/or quantum (tunneling) diffusion dependently on potential energy surfaces. SMMs are significant not only for applications but also for basic physical properties such as quantum effects on magnetization reversal. These substances are investigated from neutron scattering, x-ray diffraction, heat capacity, and dielectric measurements. Our aim is to find simple (?) rules involved in complex systems from the three different points of view, i.e., structure, dynamics, and thermodynamic.

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Heat capacities of palladium hydrides. Glass transitions due to the freezing of hydrogen motions appeared. Upper-right and lower-right figures represent the composition dependence of Tg and the crystal structure, respectively.Quasielastic neutron scattering spectra due to the magnetic reversal of a rare-earth based molecule magnet. The relaxation times are obtained by fitting the data to Lorentz functions. The inset shows the molecular structure.

 

Masuda Lab.

One of the research goals in our group is to find a novel quantum phenomenon and to reveal its mechanism in low-dimensional spin magnets and frustrated magnets. Strong quantum fluctuation or geometrical frustration disturbs the development of trivial magnetic states and induces a non-trivial quantum state. Furthermore such a state is sensitive to a small perturbation and, thus, the area is frontier of quantum phenomena. Our research topic includes spin liquid, RVB, Cuboc structure, skyrmion lattice, etc. Another goal is to observe a new magnetoelectric effect in multiferroic compounds and/or relaxor magnets. Particularly we focus on the microscopic mechanism in the system where the macroscopic thermodynamic quantities are controlled by non-conjugate field. Figure is an example of our study identifying the existence of antiferronematic interaction in a multiferroic compound by combination of neutron scattering technique and magnetization measurement.

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a. Crystal structure of Ba2CoGe2O7.

b. Structures of spin dipoles, spin nematic operator OXY, and electric polarizations in Ba2CoGe2O7. Red arrows are spin dipoles and open circles with crosses and small filled circles indicate the directions of electric polarization calculated by using the relation between spin nematic operator and electric polarization. Two-tone clovers are nematic operators.

c. Inelastic neutron scattering spectrum. Anisotropy gap of 0.1 meV is explained by antiferro-nematic interaction.

d. Angular dependence of magnetic susceptibility dM/dH. Calculation including antiferro-nematic interaction and experimental data are consistent.