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Journal Articles

Nanoscale spatial analysis of clay minerals containing cesium by synchrotron radiation photoemission electron microscopy

Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Kogure, Toshihiro*; Okochi, Takuo*; Yasui, Akira*; et al.

Applied Physics Letters, 112(2), p.021603_1 - 021603_5, 2018/01

 Times Cited Count:6 Percentile:24.09(Physics, Applied)

A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, Fe) without charging issues. We found that Cs atoms were likely to be adsorbed evenly over the entire particle. Spatially-resolved X-ray absorption spectra (XAS) of the Cs M$$_{4,5}$$-edge region showed Cs to be present in a monocation state (Cs$$^{+}$$). Further pinpoint XAS measurements were also performed at the Fe L$$_{2,3}$$-edge to determine the chemical valence of the Fe atoms. Our results demonstrate the utility of SR-PEEM as a tool for spatially-resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.

Journal Articles

Electronic structures of ferromagnetic superconductors UGe$$_{2}$$ and UCoGe studied by angle-resolved photoelectron spectroscopy

Fujimori, Shinichi; Okochi, Takuo*; kawasaki, Ikuto*; Yasui, Akira*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; et al.

Physical Review B, 91(17), p.174503_1 - 174503_9, 2015/05

 Times Cited Count:23 Percentile:70.95(Materials Science, Multidisciplinary)

The electronic structures of the ferromagnetic superconductors UGe$$_2$$ and UCoGe in the paramagnetic phase were studied by angle-resolved photoelectron spectroscopy using soft X-rays ($$h nu$$ = 400-500 eV). The quasi-particle bands with large contributions from U 5$$f$$ states were observed in the vicinity of EF, suggesting that the U 5$$f$$ electrons of these compounds have an itinerant character. Their overall band structures were explained by the band-structure calculations treating all the U 5$$f$$ electrons as being itinerant. Meanwhile, the states in the vicinity of EF show considerable deviations from the results of band-structure calculations, suggesting that the shapes of Fermi surface of these compounds are qualitatively different from the calculations, possibly caused by electron correlation effect in the complicated band structures of the low-symmetry crystals. Strong hybridization between U 5$$f$$ and $$mathrm{Co} 3d$$ states in UCoGe were found by the $$mathrm{Co}$$ 2p-3d resonant photoemission experiment, suggesting that $$mathrm{Co} 3d$$ states have finite contributions to the magnetic, transport, and superconducting properties.

Journal Articles

Magnetic patterning of FeRh thin films by energetic light ion microbeam irradiation

Koide, Tetsuya*; Sato, Takahiro; Koka, Masashi; Saito, Yuichi; Kamiya, Tomihiro; Okochi, Takuo*; Kotsugi, Masato*; Kinoshita, Toyohiko*; Nakamura, Tetsuya*; Iwase, Akihiro*; et al.

Japanese Journal of Applied Physics, 53(5S1), p.05FC06_1 - 05FC06_4, 2014/05

 Times Cited Count:10 Percentile:43.65(Physics, Applied)

We previously reported that the magnetic state of FeRh can be controlled by irradiation with ion beams. In this paper, we evaluate possibility of magnetic patterning on FeRh thin films using energetic light ion microbeam irradiation with various shapes and dimensions. Proton microbeam irradiation with 2 MeV was performed at JAEA-Takasaki to produce micron-sized magnetic patterns. XMCD-PEEM observation was performed at SPring8 to confirm the synthesized magnetic patterns. As a result, the XMCD-PEEM images of the various micrometer sized patters in FeRh film were observed using 2 MeV H ion beam. The observed bright regions are considered to have ferromagnetic spin orders, in contrast that the gray areas have anti-ferromagnetic spin order. Since the brightness of the PEEM images is strongly correlated with the magnetization of the samples, we reveal that the magnetic state in local regions of the FeRh thin films can be controlled by changing the ion fluences.

Journal Articles

Itinerant nature of U 5$$f$$ states in uranium mononitride revealed by angle-resolved photoelectron spectroscopy

Fujimori, Shinichi; Okochi, Takuo*; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika

Physical Review B, 86(23), p.235108_1 - 235108_8, 2012/12

 Times Cited Count:31 Percentile:77.15(Materials Science, Multidisciplinary)

The electronic structure of the antiferromagnet uranium nitride (UN) has been studied by angle resolved photoelectron spectroscopy using soft X-rays. The band structure as well as the Fermi surfaces in the paramagnetic phase are well explained by the band-structure calculation treating all the U 5$$f$$ electrons as being itinerant, suggesting that itinerant description of the U 5$$f$$ states is appropriate for this compound. On the other hand, changes in the spectral function due to the antiferromagnetic transition were very small. The shapes of the Fermi surfaces in a paramagnetic phase are highly three-dimensional, and the nesting of Fermi surfaces is unlikely as the origin of the magnetic ordering.

Journal Articles

Epitaxy of graphene on 3C-SiC(111) thin films on microfabricated Si(111) substrates

Ide, Takayuki*; Kawai, Yusuke*; Handa, Hiroyuki*; Fukidome, Hirokazu*; Kotsugi, Masato*; Okochi, Takuo*; Enta, Yoshiharu*; Kinoshita, Toyohiko*; Yoshigoe, Akitaka; Teraoka, Yuden; et al.

Japanese Journal of Applied Physics, 51(6), p.06FD02_1 - 06FD02_4, 2012/06

 Times Cited Count:7 Percentile:31.78(Physics, Applied)

Journal Articles

Electronic configuration of Mn ions in the $$pi$$-$$d$$ molecular ferromagnetic $$beta$$-Mn phthalocyanine studied by soft X-ray magnetic circular dichroism

Kataoka, Takashi*; Sakamoto, Yuta*; Yamazaki, Yo*; Singh, V. R.*; Fujimori, Atsushi*; Takeda, Yukiharu; Okochi, Takuo*; Fujimori, Shinichi; Okane, Tetsuo; Saito, Yuji; et al.

Solid State Communications, 152(9), p.806 - 809, 2012/05

 Times Cited Count:19 Percentile:62.16(Physics, Condensed Matter)

no abstracts in English

Journal Articles

MFM and PEEM observation of micrometre-sized magnetic dot arrays fabricated by ion-microbeam irradiation in FeRh thin films

Aiko, Kazuma*; Toki, Atsushi*; Matsui, Toshiyuki*; Iwase, Akihiro*; Sato, Takahiro; Takano, Katsuyoshi*; Koka, Masashi; Saito, Yuichi; Kamiya, Tomihiro; Okochi, Takuo*; et al.

Journal of Synchrotron Radiation, 19(2), p.223 - 226, 2012/03

 Times Cited Count:6 Percentile:33.81(Instruments & Instrumentation)

Journal Articles

Electronic structure of heavy fermion uranium compounds studied by core-level photoelectron spectroscopy

Fujimori, Shinichi; Okochi, Takuo*; Kawasaki, Ikuto; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; et al.

Journal of the Physical Society of Japan, 81(1), p.014703_1 - 014703_9, 2012/01

 Times Cited Count:36 Percentile:82.74(Physics, Multidisciplinary)

High-energy-resolution core-level and valence-band photoelectron spectroscopic studies were performed for the heavy Fermion uranium compounds UGe$$_2$$, UCoGe, URhGe, URu$$_2$$Si$$_2$$, UNi$$_2$$Al$$_3$$, UPd$$_2$$Al$$_3$$, and UPt$$_3$$ as well as typical localized and itinerant uranium compounds to understand the relationship between the uranium valence state and their core-level spectral line shapes. The core-level spectra of UGe$$_2$$, UCoGe, URhGe, URu$$_2$$Si$$_2$$, and UNi$$_2$$Al$$_3$$ are rather similar to those of itinerant compounds, suggesting that U 5$$f$$ electrons in these compounds are well hybridized with ligand states. On the other hand, the core-level spectra of UPd$$_2$$Al$$_3$$ and UPt$$_3$$ show considerably different spectral line shapes from those of the itinerant compounds, suggesting that U 5$$f$$ electrons in UPd$$_2$$Al$$_3$$ and UPt$$_3$$ are less hybridized with ligand states, leading to the correlated nature of U 5$$f$$ electrons in these compounds.

Journal Articles

Controls over structural and electronic properties of epitaxial graphene on silicon using surface termination of 3C-SiC(111)/Si

Fukidome, Hirokazu*; Abe, Shunsuke*; Takahashi, Ryota*; Imaizumi, Kei*; Inomata, Shuya*; Handa, Hiroyuki*; Saito, Eiji*; Enta, Yoshiharu*; Yoshigoe, Akitaka; Teraoka, Yuden; et al.

Applied Physics Express, 4(11), p.115104_1 - 115104_3, 2011/11

 Times Cited Count:35 Percentile:79.76(Physics, Applied)

Journal Articles

Control of epitaxy of graphene by crystallographic orientation of a Si substrate toward device applications

Fukidome, Hirokazu*; Takahashi, Ryota*; Abe, Shunsuke*; Imaizumi, Kei*; Handa, Hiroyuki*; Kang, H. C.*; Karasawa, Hiromi*; Suemitsu, Tetsuya*; Otsuji, Taiichi*; Enta, Yoshiharu*; et al.

Journal of Materials Chemistry, 21(43), p.17242 - 17248, 2011/11

 Times Cited Count:28 Percentile:65.11(Chemistry, Physical)

Journal Articles

Conduction-band electronic states of YbInCu$$_4$$ studied by photoemission and soft X-ray absorption spectroscopies

Utsumi, Yuki*; Sato, Hitoshi*; Kurihara, Hidenao*; Maso, Hiroyuki*; Hiraoka, Koichi*; Kojima, Kenichi*; Tobimatsu, Komei*; Okochi, Takuo*; Fujimori, Shinichi; Takeda, Yukiharu; et al.

Physical Review B, 84(11), p.115143_1 - 115143_7, 2011/09

 Times Cited Count:9 Percentile:40.54(Materials Science, Multidisciplinary)

We have studied conduction-band (CB) electronic states of a typical valence-transition compound YbInCu$$_4$$ by means of temperature-dependent hard X-ray photoemission spectroscopy (HX-PES), soft X-ray absorption spectroscopy (XAS), and soft X-ray photoemission spectroscopy (SX-PES) of the valence band. We have described the valence transition in YbInCu$$_4$$ in terms of the charge transfer from the CB to Yb 4$$f$$ states.

Journal Articles

Resonant angle-resolved photoelectron spectroscopy of substitutional solid solutions of CeRu$$_2$$Si$$_2$$

Okane, Tetsuo; Kawasaki, Ikuto; Yasui, Akira; Okochi, Takuo*; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji*; et al.

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA060_1 - SA060_3, 2011/07

 Times Cited Count:1 Percentile:11.64(Physics, Multidisciplinary)

Journal Articles

Band structures of CeRu$$_2$$(Si$$_{1-x}$$Ge$$_{x}$$)$$_2$$ studied by resonant soft X-ray ARPES

Okane, Tetsuo; Okochi, Takuo*; Takeda, Yukiharu; Fujimori, Shinichi; Yasui, Akira; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji*; Sugi, Motoki*; et al.

Physica Status Solidi (B), 247(3), p.397 - 399, 2010/03

Journal Articles

Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nanoparticles

Kataoka, Takashi*; Kobayashi, Masaki*; Sakamoto, Yuta*; Song, G. S.*; Fujimori, Atsushi*; Chang, F.-H.*; Lin, H.-J.*; Huang, D. J.*; Chen, C. T.*; Okochi, Takuo*; et al.

Journal of Applied Physics, 107(3), p.033718_1 - 033718_7, 2010/02


 Times Cited Count:50 Percentile:85.71(Physics, Applied)

Journal Articles

Electronic states of magnetic refrigerator materials Mn$$_{0.9}$$Fe$$_{1.1}$$P$$_{0.55}$$As$$_{0.45}$$ using soft X-ray magnetic circular dichroism

Takeda, Yukiharu; Okane, Tetsuo; Okochi, Takuo*; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Yabuta, Hisato*; Takabatake, Toshiro*

Journal of Physics; Conference Series, 200, p.012199_1 - 012199_4, 2010/02

 Times Cited Count:2 Percentile:65.77

no abstracts in English

Journal Articles

Bulk 5$$f$$ electronic states of the uranium monochalcogenide US as seen via soft X-ray photoemission

Takeda, Yukiharu; Okane, Tetsuo; Okochi, Takuo*; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi*; Ochiai, Akira*

Physical Review B, 80(16), p.161101_1 - 161101_4, 2009/10

 Times Cited Count:8 Percentile:37.58(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Element and orbital-specific observation of two-step magnetic transition in NpNiGa$$_5$$; X-ray magnetic circular dichroism study

Okane, Tetsuo; Okochi, Takuo*; Inami, Toshiya; Takeda, Yukiharu; Fujimori, Shinichi; Kawamura, Naomi*; Suzuki, Motohiro*; Tsutsui, Satoshi*; Yamagami, Hiroshi; Fujimori, Atsushi; et al.

Physical Review B, 80(10), p.104419_1 - 104419_7, 2009/09

 Times Cited Count:6 Percentile:30.24(Materials Science, Multidisciplinary)

Journal Articles

Observation of itinerant Ce 4$$f$$ electronic states in CeIrSi$$_3$$ studied by angle-resolved Ce 3$$drightarrow 4f$$ resonance photoemission spectroscopy

Okochi, Takuo*; Toshimitsu, Takafumi*; Yamagami, Hiroshi; Fujimori, Shinichi; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Miyauchi, Yuichiro*; et al.

Journal of the Physical Society of Japan, 78(8), p.084802_1 - 084802_6, 2009/08

 Times Cited Count:9 Percentile:52.87(Physics, Multidisciplinary)

We have applied angle-resolved Ce 3$$d{rightarrow}$$4$$f$$ resonance photoemission spectroscopy to the non-centrosymmetric pressure-induced superconductor CeIrSi$$_3$$ and obtained the 4$$f$$ band-structure and Fermi surfaces. We have found that the Ce 4$$f$$ states are located mainly near the Fermi level and that the photoemission intensity derived from the dispersive conduction bands across the Fermi level shows considerable resonant enhancement. In addition, the band structure and Fermi surfaces of CeIrSi$$_3$$ are different from those of the non-$$f$$ reference compound, LaIrSi$$_3$$ and the difference is well explained by the band structure calculated within the local density approximation (LDA). These results strongly suggest that the Ce 4$$f$$ electrons in CeIrSi$$_3$$ are well hybridized with conduction bands and form itinerant electronic states.

Journal Articles

Nature of magnetic coupling between Mn ions in as-grown Ga$$_{1-x}$$Mn$$_{x}$$As studied by X-ray magnetic circular dichroism

Takeda, Yukiharu; Kobayashi, Masaki*; Okane, Tetsuo; Okochi, Takuo*; Okamoto, Jun*; Saito, Yuji; Kobayashi, Keisuke*; Yamagami, Hiroshi; Fujimori, Atsushi*; Tanaka, Arata*; et al.

Hoshako, 22(4), p.202 - 209, 2009/07

no abstracts in English

Journal Articles

Experimental observation of bulk band dispersions in the oxide semiconductor ZnO using soft X-ray angle-resolved photoemission spectroscopy

Kobayashi, Masaki*; Song, G.-S.*; Kataoka, Takashi*; Sakamoto, Yuta*; Fujimori, Atsushi; Okochi, Takuo*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Yamagami, Hiroshi; et al.

Journal of Applied Physics, 105(12), p.122403_1 - 122403_4, 2009/06


 Times Cited Count:11 Percentile:43.37(Physics, Applied)

67 (Records 1-20 displayed on this page)