Yutaka Ikedo

High Energy Accelerator Research Organization, Tsukuba, Ibaraki, Japan

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Publications (70)

  • Taihei Adachi · Yutaka Ikedo · Kusuo Nishiyama · [...] · Eiko Torikai
    Article · Sep 2015
  • Conference Paper · Sep 2015
  • [Show abstract] [Hide abstract] ABSTRACT: A diffusive behavior of Li+ ion in a garnet-type oxide, Li5+xLa3ZrxNb2−x012 with x=0–2, has been investigated by both a positive muon-spin relaxation (μ+SR) and quasi-elastic neutron scattering (QENS) technique using powder samples. The μ+SR results revealed that Li+ ions start to diffuse above ~150 K for the whole samples measured. The activation energy of Li diffusion (Ea) estimated from the μ+SR data was in good agreement with Ea obtained by the QENS measurements. However, both Eas were about a half of Ea of ionic conductivity of Li+ (σLi), whichwas evaluated by AC-impedance measurements on sintered pellets. This indicated the serious effect of grain boundary and/or surface on Ea. Furthermore, since the diffusion coefficient of Li+ estimated by μ+SR is roughly independent of x, the number of mobile Li+ in the garnet lattice was found to be the predominant parameter to determine σLi.
    Article · Jun 2014 · Solid State Ionics
  • Yutaka Ikedo · Yasuhiro Miyake · Koichiro Shimomura · [...] · Kazuhiko Ishida
    [Show abstract] [Hide abstract] ABSTRACT: The second muon beamline in the Materials and Life Science Experimental Facility (MLF) of the Japan Accelerator Research Complex (J-PARC) is under construction. Our beam commissioning for U-line revealed that the U-line was the highest pulsed muon source in the world. After the commissioning, we plan to upgrade and to modify the some components of U-line. Here, we report mainly on the plan for upgrade and modification of the U-line components.
    Conference Paper · Mar 2014
  • Conference Paper · Mar 2014
  • [Show abstract] [Hide abstract] ABSTRACT: At U-line/MUSE/J-PARC, thermal muonium generation and laser resonant ionization process are required to get Ultra Slow Muon Beam. Laser radiation sources for the laser resonant ionization have been developed at RIKEN, and installed in a laser cabin. The laser radiations are introduced to Muon U-line by a transport system of the laser pulses, which consists of a VUV steering chamber and a NO gas cell. Coherent VUV radiation can be separated from two “bright” fundamental radiations for wave mixing, and 355 nm radiation is guided to the muonium production chamber at nearly same angle as VUV radiation, at the VUV steering chamber which is an ultrahigh vacuum chamber. The NO gas cell consist of the parallel plate ionization chamber with nitrogen monoxide molecules for measuring intensity of the VUV radiation.
    Conference Paper · Mar 2014
  • Yasuhiro Miyake · Yutaka Ikedo · Koichiro Shimomura · [...] · Eiko Torikai
    [Show abstract] [Hide abstract] ABSTRACT: We have been proceeding the Ultra Slow Muon project at J-PARC MUSE(MUon Science Establishment). As a first mission, we constructed the U-Line and succeeded in extracting the world highest intensity pulsed surface muons, 2,500,000 muons per pulse (6.4 × 107/s at 212 kW proton beam intensity, corresponding to 3 × 108/s at 1 MW) to the U1 experimental area. As the second mission, we have installed a Mu chamber to stop such intense pulsed surface muons towards a hot tungsten target for generating an intense ultra slow muon beam, as well as a slow ion optics to accelerate and transport ultra slow muons to the U1A and U1B areas where μ+ SR spectrometers are located. We are standing on the stage we are ready to generate ultra slow muons, if J-PARC operation is approved.
    Conference Paper · Mar 2014
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: A diffusive behavior of Li+ ion in a garnet-type oxide, Li5+xLa3ZrxNb2-xO12 with x = 0-2, has been investigated by both a positive muon-spin relaxation (μ+SR) and quasi-elastic neutron scattering (QENS) technique using powder samples. The μ+SR results revealed that Li+ ions start to diffuse above ~150 K for the whole samples measured. The activation energy of Li diffusion (Ea) estimated from the μ+SR data was in good agreement with Ea obtained by the QENS measurements. However, both Eas were about a half of Ea of ionic conductivity of Li+ (sLi), which was evaluated by AC-impedance measurements on sintered pellets. This indicated the serious effect of grain boundary and/or surface on Ea. Furthermore, since the self-diffusion coefficient of Li+ estimated by μ+SR is roughly independent of x, the number of mobile Li+ in the garnet lattice was found to be the predominant parameter to determine sLi.
    Full-text Article · Mar 2014
  • Source
    Yasuhiro Makida · Yutaka Ikedo · Toru Ogitsu · [...] · Tomofumi Orikasa
    [Show abstract] [Hide abstract] ABSTRACT: A superconducting magnet system, which is composed of an 8 m long solenoid for transportation and 12 short solenoids for focusing, has been developed for Muon Science Establishment facility of J-PARC. The transport solenoid is composed of a 6 m straight section connected to a 45 degree curved section at each end. Muons of various momenta and of both electric charges are transported through the solenoid inner bore with an effective diameter of 0.3 m, where 2 T magnetic field is induced. There are 12 focusing solenoids with an effective bore diameter of 0.6 m and a length of 0.35 m arranged on a straight line at suitable intervals. The maximum central field of each focusing solenoid is 0.66 T. All solenoid coils are cooled by GM cryocoolers through their own conductions. The magnet system has been installed into the beam line in the summer of 2012, and its performance has been checked. Beam commissioning has been carried out since October 2012. During beam operation, temperature rise over 6 K in the transport solenoid due to a nuclear heating from the muon production target is observed at beam intensity of about 300 kW.
    Full-text Article · Dec 2013
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    Kazuhiko Mukai · Yutaka Ikedo · Kazuya Kamazawa · [...] · Jun Sugiyama
    [Show abstract] [Hide abstract] ABSTRACT: Cation-ordered Li[Ni1/2Mn3/2]O4 with a P4332 space group (CO-LNMO) and "cation-disordered" (CDO) LNMO are thought to be the state-of-the-art materials for lithium-ion batteries. However, in contrast to CO-LNMO, the crystal structure and electrochemical reaction scheme of CDO-LNMO are not fully understood. We have measured the muon-spin rotation and relaxation ([small mu ]SR) spectra for samples of both CO-LNMO and CDO-LNMO, in particular at their magnetic transition temperatures (TC) below 130 K. The weak transverse field (wTF) [small mu ]SR measurements reveal that the range of TC for the CDO-LNMO sample is very large ([capital Delta]TC [similar] 55 K) compared with that for the CO-LNMO sample ([capital Delta]TC < 5 K). This suggests an inhomogeneous cation distribution in the CDO-LNMO sample, because the sample consists of multiple phases with different TC. Based on the wTF-[small mu ]SR result for stoichiometric LiMn2O4, we have proposed that CDO-LNMO is a mixture of Li[Ni1/2-[small omega]Mn3/2+[small omega]]O4 and LiMn2O4.
    Full-text Article · Aug 2013 · RSC Advances
  • [Show abstract] [Hide abstract] ABSTRACT: The magnetic structure of the metallic antiferromagnet Ag2NiO2 with the Néel temperature TN = 56 K has been investigated by means of a neutron diffraction technique using a powder sample in the temperature range between 5 and 65 K. The antiferromagnetic (AF) diffraction peaks are clearly observed below TN and can be indexed with the propagation vector [Formula: see text]. Based on the results of both a representational analysis and a Rietveld refinement of the magnetic peaks, the AF spin structure is determined as an A-type AF structure with ml = m0cos(2πk ⋅l), where ml is the moment at the lth Ni(3+) site and m0 = (0.31,0,0.65) μB at 5 K.
    Article · Jun 2013 · Journal of Physics Condensed Matter
  • Source
    Kazuhiko Mukai · Daniel Andreica · Yutaka Ikedo · [...] · Jun Sugiyama
    [Show abstract] [Hide abstract] ABSTRACT: In order to study a change in electrochemical, structural, and magnetic properties for lithium manganese oxide spinels Li[LixMn2−x]O4 (LMO) with 0 ≤ x ≤ 1/3, muon-spin rotation and relaxation (μSR) spectra were recorded under pressure (P) up to 2.1 GPa. At ambient P, P = 0.1 MPa, the antiferromagnetic or spin-glass-like transition temperature (Tm) at P = 0.1 MPa monotonically decreases with increasing x. On the contrary, the slope of the Tm vs. P (dTm/dP) rapidly increases from 0.9(1) K/GPa at x = 0 to 1.4 K/GPa at x = 0.1, then drops to 0.7(1) K/GPa at x = 0.15, and finally keeps constant (∼0.4 K/GPa) with further increasing x. Considering the structural change of LMO with x, the decrease in the distance between Mn ions (dMn-Mn) is likely to play an essential role for determining Tm under P. According to cyclic voltammetry on LMO, the peak current at both anodic and cathodic directions shows the maximum at x = 0.1, indicating the highest diffusivity of Li+ ions (DLi) at x = 0.1.
    Full-text Article · Feb 2013 · Journal of Applied Physics
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Li diffusive behavior in garnet-type oxides has been investigated by quasi-elastic neutron scattering (QENS) and muon-spin relaxation (µSR) measurements. The QENS signal increased with temperature (T) above 300 K due to Li+ motion. The activation energy obtained from the relationship between the QENS intensities and T-1 was lower about a half of that estimated by electrochemical measurements. By combining QENS and µSR results, we found that a diffusion coefficient of Li+ strongly depends on the number of mobile Li+.
    Full-text Article · Jan 2013 · Journal of the Physical Society of Japan
  • [Show abstract] [Hide abstract] ABSTRACT: The magnetic structure of the metallic antiferromagnet Ag 2 NiO 2 with the Néel temperature T N = 56 K has been investigated by means of a neutron diffraction technique using a powder sample in the temperature range between 5 and 65 K. The antiferromagnetic (AF) diffraction peaks are clearly observed below T N and can be indexed with the propagation vector ##IMG## [http://ej.iop.org/images/0953-8984/25/28/286005/cm470956ieqn42.gif] {$boldsymbolk=(1,frac13,frac12})$ . Based on the results of both a representational analysis and a Rietveld refinement of the magnetic peaks, the AF spin structure is determined as an A-type AF structure with m l = m 0 cos(2π k ⋅ l ), where m l is the moment at the l th Ni 3+ site and m 0 = (0.31,0,0.65) μ B at 5 K.
    Article · Jan 2013
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Li diffusive behavior in garnet-type oxides has been investigated by quasi-elastic neutron scattering (QENS) and muon-spin relaxation (µSR) measurements. The QENS signal increased with temperature (T) above 300 K due to Li + motion. The activation energy obtained from the relationship between the QENS intensities and T −1 was lower about a half of that estimated by electrochemical measurements. By combining QENS and µSR results, we found that a diffusion coefficient of Li + strongly depends on the number of mobile Li + .
    Full-text Article · Jan 2013 · Journal of the Physical Society of Japan
  • Source
    Yutaka Ikedo · Yasuhiro Miyake · Koichiro Shimomura · [...] · Akira Sato
    [Show abstract] [Hide abstract] ABSTRACT: Superomega muon beamline is currently under construction at Experimental hall No. 2 of Materials and Life Science Facility at J-PARC in Tokai, Japan. The beamline has a large solid angle acceptance, and will produce the highest intensity pulsed muon beam in the world. The beamline is designed to capture both surface positive and cloud negative muons for simultaneous use in a variety of experiments. The expected rate of surface muons for this beamline is 4x10(8) mu(+)/s, and that for cloud muons is 10(7) mu(-)/s. The beamline consists of the normal-conducting capture solenoid, the superconducting curved transport solenoid and axial focusing solenoid. The construction of the capture solenoid has been completed and installed in March 2009, and the transport solenoid is now fabricated, and will be installed by the end of 2011. The conceptual design of the axial focusing solenoid is completed, and the mechanical design is underway. (C) 2012 Published by Elsevier B. V. Selection and/or peer-review under responsibility of the organizing committee of the mu sr2011 conference.
    Full-text Article · Dec 2012 · Physics Procedia
  • Source
    Jun Sugiyama · Yutaka Ikedo · Martin Mansson · [...] · Kazuyoshi Yoshimura
    [Show abstract] [Hide abstract] ABSTRACT: In order to clarify the carrier density dependence of the microscopic magnetic nature in NaxCoO2 * yH2O, we have performed a μ+SR study of H2O and D2O absorbed samples. Based on the ZF-μ+SR measurements, there was no clear difference between the two superconducting phases (SCI and SCII). This is also likely to exclude the exotic scenario for the superconductivity of the SCII phase, in which the superconducting state breaks the time-reversal symmetry of the Cooper pairs, resulting in the appearance of a weak internal magnetic field below Tc. Furthermore, the ZF-spectrum for the H2O absorbed sample exhibits a clear oscillation in the whole T range measured (1.4-100 K), suggesting the formation of “[H3O]+-like” H2μ+O ions in the sample. The absence of the oscillation in the D2O absorbed sample also evidences the presence of the H2μ+O complex. Considering the fraction of the H2μ+Osignal, we have demonstrated the coexistence of [H3O]+ions and H2O in this compound. Finally, the muonic Knight shift measurements suggested the change in electronic state around 10 K and 40 K for the SCI and SCII samples.
    Full-text Article · Dec 2012 · Physics Procedia
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    Jun Sugiyama · Yutaka Ikedo · Hiroshi Nozaki · [...] · Hiroshi Ikuta
    [Show abstract] [Hide abstract] ABSTRACT: The spin-state of RECoO3(RE = La, Pr, Nd, and PrxLa1−x)has been investigated by μ+SR experiments. In particular, the muonic Knight shift in a high TF of 10 kOe was studied at temperatures below 300 K. By combining these measurements with the dc-susceptibility data, the spin-state transition temperature(TSS)was found to increase monotonically as the average ionic radius of the RE ion is decreased. Our measurements demonstrate that TF-μ+SR is a unique technique to detect the spin-state transition in compounds regardless of coexistence of large magnetic moments through the change in microscopic magnetic environments at TSS.
    Full-text Article · Dec 2012 · Physics Procedia
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    [Show abstract] [Hide abstract] ABSTRACT: In order to elucidate the magnetism and Li diffusion in LiFePO4, we have measured muon-spin rotation and relaxation (μ+SR) spectra for a polycrystalline LiFePO4 sample in the temperature range between 1.8 and 500 K. Below TN ∼ 52 K, two oscillatory signals together with onefast relaxation signal were clearly found in the zero-field (ZF) μ+SR spectrum. The three signals are reasonably explained using an antiferromagnetic (AF) spin structure proposedby neutron measurements, because electrostatic potential calculations suggests multiple different muon sites in the LiFePO4 lattice. However, the AF ordered moment estimated from μ+SR was about 3/4 of that reported by neutron, probably due to a different time window between the two techniques. In the paramagnetic state, ZF-and longitudinal-field (LF-) μ+SR spectraexhibiteda dynamic nuclear field relaxation. From the temperature dependence of the field fluctuation rate, a diffusion coeffcient of Li+ ions (DLi) at300K was estimated about 3.6×10−10 cm2/s, assuming that diffusing Li+ ions jump between the regular site and interstitial sites.
    Full-text Article · Dec 2012 · Physics Procedia
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    [Show abstract] [Hide abstract] ABSTRACT: In order to study the diffusive nature of lithium transition-metal phospho-olivines, we measured muon-spin relaxation (μ+SR) spectra for the polycrystalline LiMPO4 samples with M=Mn, Fe, Co, or Ni in the temperature range between 50 and 500 K. The μ+SR spectra under zero applied field are strongly affected by the magnetic moments of the 3d electrons in the M2+ ions so that, for LiMnPO4, it was difficult to detect the relaxation change caused by the diffusion due to the large Mn2+(S=5/2) moments. However, diffusive behavior was clearly observed via the relaxation due to nuclear dipolar fields above ∼150 K for LiFePO4, LiCoPO4, and LiNiPO4 as S decreased from 2 to 1. From the temperature dependence of the nuclear field fluctuation rate, self-diffusion coefficients of Li+ ions (DLi) at 300 K and its activation energy (Ea) were estimated, respectively, as ∼3.6(2)×10−10 cm2/s and Ea=0.10(2) eV for LiFePO4, ∼1.6(1)×10−10 cm2/s and Ea=0.10(1) eV for LiCoPO4, and ∼2.7(4)×10−10 cm2/s and Ea=0.17(2) eV for LiNiPO4, assuming that the diffusing Li+ ions jump between the regular site and interstitial sites.
    Full-text Article · Feb 2012 · Physical Review B

Publication Stats

472 Citations

Institutions

  • 2006-2012
    • High Energy Accelerator Research Organization
      • • Muon Science Laboratory
      • • Institute of Materials Structure Science
      Tsukuba, Ibaraki, Japan
  • 2010
    • Toyota Central R & D Labs., Inc.
      Nagoya, Aichi, Japan