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Journal Articles

Local structure analysis of Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$

Yoneda, Yasuhiro; Nagata, Hajime*; Takenaka, Tadashi*

Journal of the Korean Physical Society, 66(9), p.1339 - 1343, 2015/05

 Times Cited Count:1 Percentile:81.9(Physics, Multidisciplinary)

The potential lead-free piezoelectric material bismuth sodium titanate, Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$ (BNT), was investigated by means of high-energy synchrotron X-ray diffraction. BNT has been assumed thus far to exhibit the rhombohedral space group $$R3c$$ at room temperature. Recently, the average structure of BNT was described by the monoclinic space group $$Cc$$. We performed local structure analysis of BNT using atomic pair-distribution function method. The ground state of BNT was found to be rhombohedral structure in which bismuth and sodium atoms were chemically ordered in the perovskite ${it A}$-site.

Journal Articles

High-power test of annular-ring coupled structures for the J-PARC linac energy upgrade

Tamura, Jun; Ao, Hiroyuki; Nemoto, Yasuo; Asano, Hiroyuki*; Suzuki, Takahiro*

Journal of the Korean Physical Society, 66(3), p.399 - 404, 2015/02

 Percentile:100(Physics, Multidisciplinary)

ACSs are going to increase the beam energy of the J-PARC linac from 181 to 400 MeV. The 2011 Tohoku earthquake damaged the J-PARC facilities and the cavity conditioning was interrupted for two years. After the restoration of the facility, the two ACS cavities (M01 and M11) were conditioned. They achieved to 15-20% above the designed accelerating field of 4.2 MV/m. Since M01 was conditioned six years ago, the conditioning time required for M01 was drastically reduced from that for the first time. During the high-power operation for M11, which is an unique cavity equipped with a capacitive iris in a waveguide, no significant increase of the temperature and the discharge rate around the capacitive iris was observed. The vacuum pressure was sufficiently low (4$times10$^{-6}$$ Pa) even from the view point of beam loss due to residual gas scattering. The more stable operation can be expected through one-month conditioning before beam commissioning.

Journal Articles

Design and delivery of beam monitors for the energy-upgraded linac in J-PARC

Miura, Akihiko; Ouchi, Nobuo; Oguri, Hidetomo; Hasegawa, Kazuo; Miyao, Tomoaki*; Ikegami, Masanori*

Journal of the Korean Physical Society, 66(3), p.364 - 372, 2015/02

 Times Cited Count:2 Percentile:68.27(Physics, Multidisciplinary)

In J-PARC Linac, an energy upgrade project has started to achieve the design beam power of 1 MW at the exit of downstream synchrotron. To meet with significant upgrades of the beam parameters, beam monitors used for the beam commissioning are modified and fabricated. We discuss how to design and assemble the beam monitors for the upgraded Linac. We delivered them for the new upgraded beam line periodically and newly fabricated monitors for the longitudinal matching are also delivered because of the frequency jump between original RF cavity and newly developed cavity. Finally we suppose the commissioning plans to support the monitor check.

Journal Articles

Present status and future prospects of the JT-60SA project

Ishida, Shinichi; Barabaschi, P.*; Kamada, Yutaka; JT-60SA Team

Journal of the Korean Physical Society, 65(8), p.1221 - 1226, 2014/10

 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Progress of beam commissioning and beam loss mitigation in the J-PARC linac after the Tohoku earthquake

Maruta, Tomofumi; Miura, Akihiko; Sako, Hiroyuki; Tamura, Jun; Ikegami, Masanori*; Futatsukawa, Kenta*; Fang, Z.*; Miyao, Tomoaki*; Liu, Y.*

Journal of the Korean Physical Society, 63(7), p.1274 - 1279, 2013/10

 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Recovery from the earthquake and operation of the J-PARC linac

Ito, Takashi

Journal of the Korean Physical Society, 63(7), p.1243 - 1248, 2013/10

 Times Cited Count:1 Percentile:84.55(Physics, Multidisciplinary)

The Japan Proton Accelerator Research Complex (J-PARC) facilities were extensively damaged by the March 2011 earthquake. At the linac facility, a large amount of groundwater leaked into the tunnel. Therefore, the accelerator components were exposed to high-humidity air for several weeks. Vacuum leaks occurred in ion source, MEBT1 and SDTL sections by destruction of vacuum port, beam monitors and bellows. An alignment of the linac was also damaged. There had been observed about 0.2 mm misalignment of the DT bore center in the DTL and the displacement more than 40 mm of the alignment of the cavity. After recovery efforts, we resumed the beam operation in December 2011 and user operation in January 2012. The beam power from the linac reached at 13.3 kW in March 2012, which is the same power as just before the earthquake. In this report, we will present the recovery works from the earthquake and the present operating status of the J-PARC linac.

Journal Articles

Novel field-induced quantum phase transition of the kagome-lattice antiferromagnet

Sakai, Toru; Nakano, Hiroki*

Journal of the Korean Physical Society, 63(2), p.601 - 604, 2013/08

 Times Cited Count:1 Percentile:84.55(Physics, Multidisciplinary)

The kagome-lattice antiferromagnet is investigated using the numerical exact diagonalization up to 42-spin clusters. From our investigation of the magnetization process, we found a novel field-induced quantum phase transition, called the "magnetization ramp", at 1/3 of the saturation magnetization. The finite-size scaling analysis of the critical exponents indicated a significant difference of the magnetization ramp from the magnetization plateau observed in the triangular-lattice antiferromagnet.

Journal Articles

$$^{29}$$Si-NMR study of antiferromagnet CeRh$$_2$$Si$$_2$$ using single crystals

Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Matsumoto, Yuji; Matsuda, Tatsuma; Haga, Yoshinori

Journal of the Korean Physical Society, 63(3), p.352 - 355, 2013/08

 Times Cited Count:2 Percentile:73.65(Physics, Multidisciplinary)

$$^{29}$$Si-NMR Study of antiferromagnet CeRh$$_2$$Si$$_2$$ with a tetragonal ThCr$$_2$$Si$$_2$$-type structure has been performed using single crystals. The Knight shifts along the $$a$$ and $$c$$ axes have been measured as a function of temperatures in the paramagnetic state. At ambient pressure, the Knight shifts show the Ising-type anisotropy along the $$c$$ axis, which is similar to the magnetic susceptibility. The hyperfine coupling constants for $$^{29}$$Si along the $$a$$ and $$c$$ axes have been determined from Knight shifts versus static susceptibility plots.

Journal Articles

Magnetic phase diagram of UCoAl

Matsuda, Tatsuma; Tateiwa, Naoyuki; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika; Aoki, Dai*; Flouquet, J.*; Fisk, Z.

Journal of the Korean Physical Society, 63(3), p.575 - 578, 2013/08

 Times Cited Count:4 Percentile:57.4(Physics, Multidisciplinary)

Journal Articles

Powder neutron diffraction study of HoCoGa$$_{5}$$

Kobayashi, Riki; Kaneko, Koji; Wakimoto, Shuichi; Chi, S.*; Sanada, Naoyuki*; Watanuki, Ryuta*; Suzuki, Kazuya*

Journal of the Korean Physical Society, 63(3), p.337 - 340, 2013/08

 Times Cited Count:2 Percentile:73.65(Physics, Multidisciplinary)

Journal Articles

Magnetic property in the ferromagnetic superconductor UGe$$_2$$ at pressures above the ferromagnetic critical pressure

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Yamamoto, Etsuji; Onuki, Yoshichika; Fisk, Z.

Journal of the Korean Physical Society, 63(3), p.627 - 631, 2013/08

 Percentile:100(Physics, Multidisciplinary)

UGe$$_2$$ is a ferromagnet with the Curie temperature of 54 K at ambient pressure. The superconductivity appears in the pressure region of 1.0-1.6 GPa where UGe$$_2$$ is in the ferromagnetic state. Ferromagnetic state disappears above $$P_c$$ =1.6 GPa. In this study, we have measured the dc-magnetization up to 4.1 GPa using the ceramic anvil high pressure cell. We confirmed the maximum at $$T_{max}$$ in the temperature dependence of the dc magnetic susceptibility. With increasing pressure, $$T_{max}$$ is increased from 24 K at 1.9 GPa to 32 K at 2.6 GPa. The peak structure around $$T_{max}$$ becomes broader with increasing pressure and disappears above 4 GPa. The metamagnetic transition field $$H_m$$ increases rapidly with increasing pressure. We discuss the experimental results with the phenomenological spin-fluctuation theory.

Journal Articles

Shubnikov-de Haas oscillation in PuIn$$_3$$

Haga, Yoshinori; Bauer, E. D.*; Tobash, P. H.*; Mitchell, J. N.*; Ayala-Valenzuela, O.*; McDonald, R. D.*; Mielke, C. H.*; Fisk, Z.

Journal of the Korean Physical Society, 63(3), p.380 - 382, 2013/08

 Times Cited Count:2 Percentile:73.65(Physics, Multidisciplinary)

Journal Articles

Single crystal growth and physical properties of UT$$_2$$Al$$_{20}$$ (T = transition metal)

Matsumoto, Yuji; Matsuda, Tatsuma; Tateiwa, Naoyuki; Yamamoto, Etsuji; Haga, Yoshinori; Fisk, Z.

Journal of the Korean Physical Society, 63(3), p.363 - 366, 2013/08

 Times Cited Count:6 Percentile:46.59(Physics, Multidisciplinary)

Journal Articles

Optical conductivity of antiferromagnetic metallic chromium; Mean-field calculation for the multi-orbital Hubbard model

Sugimoto, Kodai*; Toyama, Takami*; Kaneshita, Eiji*; Tsutsui, Kenji

Journal of the Korean Physical Society, 63(3), p.632 - 635, 2013/08

 Percentile:100(Physics, Multidisciplinary)

Cr is the representative material of multi-orbital antiferromagnetism. We numerically calculate the band structure and density of states in commensurate antiferromagnetic Cr by multi-orbital Hubbard model with mean-field approximation. The result is adopted to the calculation of optical conductivity. The spectra of the optical conductivity is consistent with experimental data, and this promises the validity of our model.

Journal Articles

Heavy fermions and unconventional superconductivity in high-quality single crystals of rare-earth and actinide compounds

Onuki, Yoshichika; Settai, Rikio*; Sugiyama, Kiyohiro*; Takeuchi, Tetsuya*; Honda, Fuminori*; Haga, Yoshinori; Yamamoto, Etsuji; Matsuda, Tatsuma; Tateiwa, Naoyuki; Aoki, Dai*; et al.

Journal of the Korean Physical Society, 63(3), p.409 - 415, 2013/08

 Times Cited Count:1 Percentile:84.55(Physics, Multidisciplinary)

Journal Articles

Heavy fermion superconductivity; 5f vs 4f

Fisk, Z.; Haga, Yoshinori

Journal of the Korean Physical Society, 63(3), p.795 - 799, 2013/08

 Times Cited Count:1 Percentile:84.55(Physics, Multidisciplinary)

Journal Articles

Pressure evolution of the metamagnetic transition in UCoAl As measured using $$^{59}$$Co NMR

Kotegawa, Hisashi*; Nohara, Hiroki*; To, Hideki*; Matsuda, Tatsuma; Yamamoto, Etsuji; Haga, Yoshinori; Fisk, Z.; Onuki, Yoshichika; Aoki, Dai*; Flouquet, J.*

Journal of the Korean Physical Society, 63(3), p.341 - 344, 2013/08

 Times Cited Count:1 Percentile:84.55(Physics, Multidisciplinary)

Journal Articles

Real-time analysis of the spinmotive force due to domain wall motion

Ieda, Junichi; Maekawa, Sadamichi; Yamane, Yuta

Journal of the Korean Physical Society, 62(12), p.1802 - 1806, 2013/06

 Times Cited Count:1 Percentile:84.55(Physics, Multidisciplinary)

Spinmotive force, which is induced by motion of a nonuniform magnetic nanostructure, reflects real time dynamics of the magnetization texture. Using numerical simulations we study the spinmotive force associated with domain wall motion and find that its dc component scales with an applied magnetic field even in a field range where the wall motion is no longer associated with periodic angular rotation of the wall magnetization. As the field is increased, spikes in the voltage signals start to appear, which are mainly associated with vortex core nucleation and annihilation. At high fields, the slope of the generated dc voltage with the applied field is expected to be only dependent on the spin polarization of conduction electrons and thus can be used to accurately determine the degree of spin polarization in various materials.

Journal Articles

Linear-response theory of the longitudinal spin Seebeck effect

Adachi, Hiroto; Maekawa, Sadamichi

Journal of the Korean Physical Society, 62(12), p.1753 - 1758, 2013/06

 Times Cited Count:10 Percentile:34.07(Physics, Multidisciplinary)

Journal Articles

Heat and spin

Maekawa, Sadamichi; Adachi, Hiroto

Journal of the Korean Physical Society, 62(12), p.1985 - 1989, 2013/06

 Percentile:100(Physics, Multidisciplinary)

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