NMR study of electronic state in CePt3Si

In this article, we report the temperature dependence of spin-lattice relaxation rates at two Pt sites and one Si site in CePt3Si with a non-centrosymmetric structure center. 1/T1 for both Pt sites between 2 K and 300 K and 1/T1 of Si above 3 K might be explained by the contributions from the low-lying crystal-electric-field level and the quasiparticle due to the hybridization between the ground state and conduction electrons. Just below Tc no remarkable enhancement in 1/T1 was observed. The estimated value of superconducting gap is about 2Delta = 3kBTc.Comment: 2 pages with 2 EPS figures. uses phb-proc4-auth.cls. Accepted for publication in Physica

Dispersion and damping of zone-boundary magnons in the noncentrosymmetric superconductor CePt3Si

Inelastic neutron scattering (INS) is employed to study damped spin-wave excitations in the noncentrosymmetric heavy-fermion superconductor CePt3Si along the antiferromagnetic Brillouin-zone boundary in the low-temperature magnetically ordered state. Measurements along the (1/2 1/2 L) and (H H 1/2-H) reciprocal-space directions reveal deviations in the spin-wave dispersion from the previously reported model. Broad asymmetric shape of the peaks in energy signifies strong spin-wave damping by interactions with the particle-hole continuum. Their energy width exhibits no evident anomalies as a function of momentum along the (1/2 1/2 L) direction, which could be attributed to Fermi-surface nesting effects, implying the absence of pronounced commensurate nesting vectors at the magnetic zone boundary. In agreement with a previous study, we find no signatures of the superconducting transition in the magnetic excitation spectrum, such as a magnetic resonant mode or a superconducting spin gap, either at the magnetic ordering wavevector (0 0 1/2) or at the zone boundary. However, the low superconducting transition temperature in this material still leaves the possibility of such features being weak and therefore hidden below the incoherent background at energies ~0.1 meV, precluding their detection by INS

Magnetic structure, phase diagram, and a new type of spin-flop transition dominated by higher order interaction in a localized 5f system U3Pd20Si6

The magnetic structure of the localized-5f uranium intermetallic compound U3Pd20Si6 has been determined by means of a neutron diffraction experiment. Our data demonstrate that this compound has a collinear coupling of the sublattice ordering of the uranium spins on the 4a and 8c sites. We conclude that higher-order exchange and/or quadrupole interactions are necessary to stabilize this unique collinear structure. We discovered a new type of spin-flop transition against the uniaxial anisotropy induced by this collinear coupling

Magnetic Properties of a Pressure-induced Superconductor UGe2_2

We performed the DC-magnetization and neutron scattering experiments under pressure {\it P} for a pressure-induced superconductor UGe$_2$. We found that the magnetic moment is enhanced at a characteristic temperature {\it T}$^{*}$ in the ferromagnetic state, where {\it T}$^{*}$ is smaller than a Curie temperature {\it T}$_{\rm C}$. This enhancement becomes remarkable in the vicinity of {\it P}$_{\rm C}^{*}$ = 1.20 GPa, where {\it T}$^{*}$ becomes 0 K and the superconducting transition temperature {\it T}$_{\rm SC}$ shows a maximum. The characteristic temperature {\it T}$^{*}$, which decreases with increasing pressure, also depends on the magnetic field.Comment: To be published in J.Phys.Soc.Jp

Suggestions for Safe Motorchair Football.

本研究は電動車椅子サッカーの岡山県における活動状況を把握し，このスポーツを安全に行う方法について検討することを目的とした。対象は脊髄損傷(A群)，脳性麻痺(B群)，筋ジストロフイー(C群)の選手各々4名， 5名および4名の計13名で，平成13年8月24日から平成13年12月23日までに行なわれた計8日の練習および試合をビデオカメラを用いて撮影し分析した。平成13年12月14日までの練習状況から電動車椅子同士の衝突により生じるスピン，身体接触，電動車椅子の浮揚の危険な衝突に着目し，平成13年12月23日に行なわれた3試合，計120分のなかで危険な衝突に関して分析を行った。その結果， A群では 危険な衝突が19回， BおよびC群でも計19回みられた。それらの内，衝突後の防御姿勢の有無に関してA群は認められた回数が17回，認められなかった回数が2回であった。B群およびC群では，認められた回数がl回，認められなかった回数が18回であった。A群とB・C群間での防御姿勢の有無に関する差異は有意(x2検定， p < 0.01) であった。以上より障害種別によるクラス分けの必要性が明らかになった。さらにヘルメットやプロテクターの着用の重要性に関しての指摘も行い，指導員の養成の必要性についても考察した

Magnetic Excitations in NpCoGa5

We report the results of inelastic neutron scattering experiments on NpCoGa$_{5}$, an isostructural analogue of the PuCoGa$_{5}$ superconductor. Two energy scales characterize the magnetic response in the antiferromagnetic phase. One is related to a non-dispersive excitation between two crystal field levels. The other at lower energies corresponds to dispersive fluctuations emanating from the magnetic zone center. The fluctuations persist in the paramagnetic phase also, although weaker in intensity. This supports the possibility that magnetic fluctuations are present in PuCoGa$_{5}$, where unconventional d-wave superconductivity is achieved in the absence of magnetic order.Comment: 4 pages, 5 figure