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Journal Articles

Distinct variation of electronic states due to annealing in $$T'$$-type La$$_{1.8}$$Eu$$_{0.2}$$CuO$$_{4}$$ and Nd$$_{2}$$CuO$$_{4}$$

Asano, Shun*; Ishii, Kenji*; Matsumura, Daiju; Tsuji, Takuya; Kudo, Kota*; Taniguchi, Takanori*; Saito, Shin*; Sunohara, Toshiki*; Kawamata, Takayuki*; Koike, Yoji*; et al.

Physical Review B, 104(21), p.214504_1 - 214504_7, 2021/12

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

One-dimensional spinon spin currents

Hirobe, Daichi*; Sato, Masahiro*; Kawamata, Takayuki*; Shiomi, Yuki*; Uchida, Kenichi*; Iguchi, Ryo*; Koike, Yoji*; Maekawa, Sadamichi; Saito, Eiji

Nature Physics, 13(1), p.30 - 34, 2017/01

 Times Cited Count:91 Percentile:96.69(Physics, Multidisciplinary)

Journal Articles

Observation of momentum-resolved charge fluctuations proximate to the charge-order phase using resonant inelastic X-ray scattering

Yoshida, Masahiro*; Ishii, Kenji; Naka, Makoto*; Ishihara, Sumio*; Jarrige, I.*; Ikeuchi, Kazuhiko*; Murakami, Yoichi*; Kudo, Kazutaka*; Koike, Yoji*; Nagata, Tomoko*; et al.

Scientific Reports (Internet), 6, p.23611_1 - 23611_8, 2016/03

 Times Cited Count:1 Percentile:11.55(Multidisciplinary Sciences)

Journal Articles

Momentum-resolved resonant inelastic X-ray scattering on a single crystal under high pressure

Yoshida, Masahiro*; Ishii, Kenji; Jarrige, I.*; Watanuki, Tetsu; Kudo, Kazutaka*; Koike, Yoji*; Kumagai, Kenichi*; Hiraoka, Nozomu*; Ishii, Hirofumi*; Tsuei, K.-D.*; et al.

Journal of Synchrotron Radiation, 21(1), p.131 - 135, 2014/01

 Times Cited Count:3 Percentile:19.11(Instruments & Instrumentation)

Journal Articles

Resonant inelastic X-ray scattering study of intraband charge excitations in hole-doped high-$$T_c$$ cuprates

Wakimoto, Shuichi; Ishii, Kenji; Kimura, Hiroyuki*; Ikeuchi, Kazuhiko*; Yoshida, Masahiro*; Adachi, Tadashi*; Casa, D.*; Fujita, Masaki*; Fukunaga, Yasushi*; Gog, T.*; et al.

Physical Review B, 87(10), p.104511_1 - 104511_7, 2013/03

 Times Cited Count:9 Percentile:43.58(Materials Science, Multidisciplinary)

Journal Articles

Temperature dependence of the electronic structure of Sr$$_{14}$$Cu$$_{24}$$O$$_{41}$$ studied by resonant inelastic X-ray scattering

Yoshida, Masahiro; Ishii, Kenji; Ikeuchi, Kazuhiko*; Jarrige, I.; Murakami, Yoichi*; Mizuki, Junichiro; Tsutsui, Kenji; Toyama, Takami*; Maekawa, Sadamichi*; Kudo, Kazutaka*; et al.

Physica C, 470(Suppl.1), p.S145 - S146, 2010/12

 Times Cited Count:4 Percentile:22.02(Physics, Applied)

Journal Articles

Linear polarization measurements with a new soft X-ray polarimeter and ellipsometer at a bending magnet beamline of a compact storage ring

Imazono, Takashi; Sano, Kazuo*; Suzuki, Yoji; Kawachi, Tetsuya; Koike, Masato

AIP Conference Proceedings 1234, p.347 - 350, 2010/06

 Times Cited Count:3 Percentile:75.92

Linear polarization measurements were carried out using a newly developed soft X-ray polarimeter and ellipsometer (SXPE) for complete polarization analysis at a soft X-ray beamline (BL-11) of the SR Center, Ritsumeikan University, Japan. A Mo/Si multilayer mirror was deposited on the surface of a Si(111) substrate by an ion beam sputtering method. It was cut into two pieces which were then used as reflection-type polarizers. When the incident wavelength was scanned from 12.4 nm to 14.8 nm by a Monk-Gillieson type varied-line-spacing grating monochromator of the BL-11, the angles of incidence of both the Mo/Si multilayer polarizers in the SXPE were also varied from 37.5$$^circ$$ to 52.3$$^circ$$. The polarizances depended strongly on the wavelength, and the best performance of over 99% was obtained in the vicinity of 14 nm. Using these polarizers, we assessed that the degree of linear polarization of the BL-11 was almost constant at 85-88% in the measured wavelength range.

Journal Articles

A New soft X-ray polarimeter and ellipsometer at BL-11

Imazono, Takashi; Sano, Kazuo*; Suzuki, Yoji; Kawachi, Tetsuya; Koike, Masato

Memoirs of the SR Center Ritsumeikan University, (12), p.87 - 100, 2010/05

A novel apparatus for polarimetric and ellipsometric measurements for the complete polarization analysis in the soft X-ray (SX) region, which is based on the rotating-analyzer ellipsometry by using six independently movable drive shafts, has been designed, constructed, and installed in BL-11. Linear polarization measurement has been demonstrated using two identical Mo/Si multilayer polarizers. The incident wavelength was scanned from 12.4 nm to 14.8 nm by a VLS-PGM of BL-11, and the angles of incidence of both polarizers were also varied from 37.5$$^circ$$ to 52.3$$^circ$$. The best performance of polarizers has been determined to be over 99% at 13.9 nm, and the degree of linear polarization has been assessed to be 85-88% in the measured wavelength range for the first time since the completion of the beamline. This means that BL-11 is upgraded as the comprehensive evaluation beamline for optical elements including polarizing elements for use in the SX region.

Journal Articles

Incommensurate spin correlations induced by magnetic Fe ions substituted into overdoped Bi$$_{1.75}$$Pb$$_{0.35}$$Sr$$_{1.90}$$CuO$$_{6+z}$$

Hiraka, Haruhiro*; Hayashi, Yoichiro*; Wakimoto, Shuichi; Takeda, Masayasu; Kakurai, Kazuhisa; Adachi, Tadashi*; Koike, Yoji*; Yamada, Ikuya*; Miyazaki, Masanori*; Hiraishi, Masatoshi*; et al.

Physical Review B, 81(14), p.144501_1 - 144501_6, 2010/04

 Times Cited Count:15 Percentile:55.1(Materials Science, Multidisciplinary)

Journal Articles

Design of an apparatus for polarization measurement in soft X-ray region

Imazono, Takashi; Suzuki, Yoji; Sano, Kazuo*; Koike, Masato

Spectrochimica Acta, Part B, 65(2), p.147 - 151, 2010/02

 Times Cited Count:2 Percentile:14.6(Spectroscopy)

To meet the needs we have been developing an apparatus to evaluate polarization abilities of multilayer- and crystal-types polarizing elements and determine the polarization state of light in 1 keV region. The 8-axis goniometer called the polarization analysis-unit is equipped in this apparatus and consists of a phase shifter-unit and an analyzer-unit. All axes can be driven with HV compatible stepping motors. Both reflection- and transmission-types samples are available on P and A. Therefore, this apparatus makes it possible to carry out not only conventional reflection and transmission measurements but also four scanning modes which are double- reflections and transmissions, and transmission-reflection and vice versa.

Journal Articles

Development and performance test of a soft X-ray polarimeter and ellipsometer for complete polarization analysis

Imazono, Takashi; Sano, Kazuo*; Suzuki, Yoji; Kawachi, Tetsuya; Koike, Masato

Review of Scientific Instruments, 80(8), p.085109_1 - 085109_8, 2009/08

 Times Cited Count:18 Percentile:60.25(Instruments & Instrumentation)

A new apparatus for polarimetric and ellipsometric measurements based on the rotating-analyzer method in the soft X-ray region has been designed, constructed, and installed in the soft X-ray beamline BL-11 at the SR Center of Ritsumeikan University, Shiga, Japan. It can realize the optical configurations for the complete polarization analysis by using six independently movable drive shafts. A demonstration of the capabilities of the apparatus has been performed using Mo/Si multilayer polarizers deposited by an ion beam sputtering method. It is for the first time shown that the degree of linear polarization of monochromatized light from the BL-11 is approximately 87% at 92 eV since the beamline has been constructed.

Journal Articles

Charge excitations in the stripe-ordered La$$_{5/3}$$Sr$$_{1/3}$$NiO$$_{4}$$ and La$$_{2-x}$$(Ba,Sr)$$_{x}$$CuO$$_{4}$$ superconducting compounds

Wakimoto, Shuichi; Kimura, Hiroyuki*; Ishii, Kenji; Ikeuchi, Kazuhiko; Adachi, Tadashi*; Fujita, Masaki*; Kakurai, Kazuhisa; Koike, Yoji*; Mizuki, Junichiro; Noda, Yukio*; et al.

Physical Review Letters, 102(15), p.157001_1 - 157001_4, 2009/04

 Times Cited Count:25 Percentile:75.04(Physics, Multidisciplinary)

Journal Articles

$$mu$$SR study of impurity effects on the Cu-spin fluctuations in the overdoped regime of La$$_{2-x}$$Sr$$_x$$Cu$$_{1-y}$$Zn$$_y$$O$$_4$$

Risdiana*; Adachi, Tadashi*; Oki, Naoki*; Yairi, Satoshi*; Tanabe, Yoichi*; Omori, Keisuke*; Suzuki, Takao*; Watanabe, Isao*; Koda, Akihiro*; Higemoto, Wataru; et al.

Physica C, 460-462(2), p.874 - 875, 2007/09

 Times Cited Count:3 Percentile:17.92(Physics, Applied)

Zero-field muon-spin-relaxation measurements have been carried out for La$$_{2-x}$$Sr$$_x$$Cu$$_{1-y}$$Zn$$_y$$O$$_4$$ (LSCO)with $$y$$ = 0-0.10 in the overdoped regime up to $$x$$ = 0.30, in order to investigate whether the dynamical stripe correlations are pinned and stabilized even for the overdoped LSCO or not. It has been found that the Zn-induced slowing down of the Cu-spin fluctuations is weakened with increasing $$x$$ but takes place in the overdoped regime and disappears at $$x$$ = 0.30. This suggests that the stripe-pinning model holds good in the whole superconducting regime of LSCO and that there is no quantum critical point at $$x$$ $$sim$$ 0.19.

Journal Articles

Momentum-dependent charge excitations of a two-leg ladder; Resonant inelastic X-ray scattering of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$

Ishii, Kenji; Tsutsui, Kenji*; Toyama, Takami*; Inami, Toshiya; Mizuki, Junichiro; Murakami, Yoichi*; Endo, Yasuo*; Maekawa, Sadamichi*; Kudo, Kazutaka*; Koike, Yoji*; et al.

Physical Review B, 76(4), p.045124_1 - 045124_7, 2007/07

 Times Cited Count:20 Percentile:63.5(Materials Science, Multidisciplinary)

(La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ is an attractive material in connection with high-$$T_{rm c}$$ superconductivity because Sr$$_{0.4}$$Ca$$_{13.6}$$Cu$$_{24}$$O$$_{41}$$ becomes a superconductor under high pressure without the CuO$$_2$$ planes. We present RIXS at the Cu $$K$$-edge of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ focusing on the momentum dependence of interband excitation across the Mott gap and the intraband excitation below the gap as a function of hole concentration. The experimental results are consistent with the theoretical predictions.

Journal Articles

Effects of hole doping on magnetic ground and excited states in the edge-sharing CuO$$_2$$ chains of Ca$$_{2+x}$$Y$$_{2-x}$$Cu$$_5$$O$$_{10}$$

Matsuda, Masaaki; Kakurai, Kazuhisa; Kurogi, Shogo*; Kudo, Kazutaka*; Koike, Yoji*; Yamaguchi, Hirotaka*; Ito, Toshimitsu*; Oka, Kunihiko*

Physical Review B, 71(10), p.104414_1 - 104414_8, 2005/03

 Times Cited Count:13 Percentile:50.02(Materials Science, Multidisciplinary)

no abstracts in English

Oral presentation

Charge excitations in (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ studied by resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Toyama, Takami*; Mizuki, Junichiro; Endo, Yasuo; Maekawa, Sadamichi*; Kudo, Kazutaka*; Koike, Yoji*; Kumagai, Kenichi*

no journal, , 

(La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ is an attractive material in connection with high-$$T_{rm c}$$ superconductivity because Sr$$_{0.4}$$Ca$$_{13.6}$$Cu$$_{24}$$O$$_{41}$$ becomes a superconductor under high pressure without the CuO$$_2$$ planes. We present RIXS at the Cu $$K$$-edge of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ focusing on the momentum dependence of interband excitation across the Mott gap and the intraband excitation below the gap as a function of hole concentration. The experimental results are consistent with the theoretical predictions.

Oral presentation

Resonant inelastic X-ray scattering study of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$

Ishii, Kenji; Tsutsui, Kenji*; Toyama, Takami*; Inami, Toshiya; Mizuki, Junichiro; Murakami, Yoichi*; Endo, Yasuo*; Maekawa, Sadamichi*; Kudo, Kazutaka*; Koike, Yoji*; et al.

no journal, , 

(La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ is an attractive material in connection with high-$$T_{rm c}$$ superconductivity because Sr$$_{0.4}$$Ca$$_{13.6}$$Cu$$_{24}$$O$$_{41}$$ becomes a superconductor under high pressure without the CuO$$_2$$ planes. We present RIXS at the Cu $$K$$-edge of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ focusing on the momentum dependence of interband excitation across the Mott gap and the intraband excitation below the gap as a function of hole concentration. The experimental results are consistent with the theoretical predictions.

Oral presentation

Resonant inelastic X-ray scattering of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$

Ishii, Kenji; Tsutsui, Kenji*; Toyama, Takami*; Inami, Toshiya; Mizuki, Junichiro; Murakami, Yoichi*; Endo, Yasuo*; Maekawa, Sadamichi*; Kudo, Kazutaka*; Koike, Yoji*; et al.

no journal, , 

(La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ is an attractive material in connection with high-$$T_{rm c}$$ superconductivity because Sr$$_{0.4}$$Ca$$_{13.6}$$Cu$$_{24}$$O$$_{41}$$ becomes a superconductor under high pressure without the CuO$$_2$$ planes. We present RIXS at the Cu $$K$$-edge of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ focusing on the momentum dependence of interband excitation across the Mott gap and the intraband excitation below the gap as a function of hole concentration. The experimental results are consistent with the theoretical predictions.

Oral presentation

Low-temperature synthesis of La$$_2$$CuO$$_4$$ with the T'-structure using molten hydroxides

Imai, Yoshinori; Kato, Masatsune*; Takarabe, Yuichiro*; Noji, Takashi*; Adachi, Tadashi*; Koike, Yoji*

no journal, , 

Lanthanide copper oxides of a general formula $$Ln_2$$CuO$$_4$$ ($$Ln$$: Lanthanide) crystallize in two different structures: the K$$_2$$NiF$$_4$$-type(T-type) and the Nd$$_2$$CuO$$_4$$-type(T'-type). The crystal structure of La$$_2$$CuO$$_4$$ synthesized by the solid-state reaction at elevated temperatures, $$sim$$1000$$^{circ}$$C, is the T-type. Recently, Tsukada et al. have reported that T'-(La,Ln)$$_2$$CuO$$_4$$ films, which were prepared at 600$$^{circ}$$C using the molecular beam epitaxy and then annealed in vacuum, show superconductivity with $$T_csim$$25K. Here, we report that polycrystalline bulk samples of T'-La$$_2$$CuO$$_4$$ have been successfully synthesized by precipitation from the molten NaOH/KOH eutectic mixture at a temperature as low as 350$$^{circ}$$C. The powder X-ray diffraction pattern has revealed the formation of a single phase with the T'-type structure. The lattice parameters are a$$=$$4.02$$mathrm{AA}$$ and c$$=$$12.49$$mathrm{AA}$$. The a-axis length is much larger than that of Pr$$_2$$CuO$$_4$$ (a$$=$$3.96$$mathrm{AA}$$). However, no superconductivity is observed at t$$>$$2K in the magnetic susceptibility and electrical resistivity measurements.

Oral presentation

Resonant inelastic X-ray scattering of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$

Ishii, Kenji; Tsutsui, Kenji*; Toyama, Takami*; Inami, Toshiya; Mizuki, Junichiro; Murakami, Yoichi*; Endo, Yasuo*; Maekawa, Sadamichi*; Kudo, Kazutaka*; Koike, Yoji*; et al.

no journal, , 

(La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ is an attractive material in connection with high-$$T_{rm c}$$ superconductivity because Sr$$_{0.4}$$Ca$$_{13.6}$$Cu$$_{24}$$O$$_{41}$$ becomes a superconductor under high pressure without the CuO$$_2$$ planes. We present RIXS at the Cu $$K$$-edge of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ focusing on the momentum dependence of interband excitation across the Mott gap and the intraband excitation below the gap as a function of hole concentration. The experimental results are consistent with the theoretical predictions.

39 (Records 1-20 displayed on this page)