SRPES and XPS analysis of activation and deterioration processes for Ti-Zr-V NEG coating

Kamiya, Junichiro; Abe, Kazuhide; Fujimori, Shinichi; Fukuda, Tatsuo; Kobata, Masaaki; Morohashi, Yuko; Tsuda, Yasutaka; Yamada, Ippei; Yoshigoe, Akitaka

e-Journal of Surface Science and Nanotechnology (Internet), 22(4), p.316 - 326, 2024/08

https://doi.org/10.1380/ejssnt.2024-030

The activation and deterioration mechanisms of the Ti-Zr-V non-evaporable getter (NEG) coating have been investigated. Operando analysis of the surface chemical composition change of the Ti-Zr-V coating was performed by the synchrotron radiation photoelectron spectroscopy (SRPES) during the process of raising the sample temperature to 250C, corresponding to the activation process of NEG coating. The surface oxidation process was also characterized by the SRPES during the injection of O_2 gas into the chamber while keeping the sample temperature at 250C, corresponding to the deterioration process of NEG coating, i.e. surface oxidation and oxygen diffusion to the coating interior. The depth profile of the oxidized sample was measured with X-ray photoelectron spectroscopy. The results shows, in the activation process, the surface Zr gets the oxygen from the oxides of Ti and V at the first stage, resulting in the metallic Ti and V on the surface, and the oxygen of the Zr-oxide and/or Zr sub-oxides diffuse to the interior of the coating in the continuous temperature rise, resulting in the metallic Zr on the surface. It is further suggested that the deterioration of the Ti-Zr-V NEG coating means the Zr and secondary Ti are oxidized deep into the coating, resulting in the restriction of the oxygen migration from the NEG compositions on the surface and consequently the lack of surface metallization.

Role of on-site Coulomb interactions in the half-metallic Weyl ferromagnet candidate thin-film CoFeSi

Sumida, Kazuki; Fujita, Yuichi*; Zhou, W.*; Masuda, Keisuke*; Kawasaki, Ikuto; Fujimori, Shinichi; Kimura, Akio*; Sakuraba, Yuya*

Physical Review B, 108(24), p.L241101_1 - L241101_6, 2023/12

https://doi.org/10.1103/PhysRevB.108.L241101

Impact of the Ce states in the electronic structure of the intermediate-valence superconductor CeIr

Fujimori, Shinichi; Kawasaki, Ikuto; Takeda, Yukiharu; Yamagami, Hiroshi; Sasabe, Norimasa*; Sato, Yoshiki*; Shimizu, Yusei*; Nakamura, Ai*; Maruya, A.*; Homma, Yoshiya*; et al.

Electronic Structure (Internet), 5(4), p.045009_1 - 045009_7, 2023/11

https://doi.org/10.1088/2516-1075/ad0a3d

Quasiparticle state in 4 localized ferromagnet CeRuGe studied by soft X-ray photoemission spectroscopy

Kawasaki, Ikuto; Fujimori, Shinichi; Takeda, Yukiharu; Yamagami, Hiroshi; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 92(6), p.064709_1 - 064709_8, 2023/06

https://doi.org/10.7566/JPSJ.92.064709

Electronic structure of ThPdAl; Impact of the U states on the electronic structure of UPdAl

Fujimori, Shinichi; Takeda, Yukiharu; Yamagami, Hiroshi; Pospil, J.*; Yamamoto, Etsuji; Haga, Yoshinori

Physical Review B, 105(11), p.115128_1 - 115128_6, 2022/03

https://doi.org/10.1103/PhysRevB.105.115128

Electronic structure of the intermediate-valence compound EuNiP studied by soft X-ray photoemission spectroscopy

Kawasaki, Ikuto; Kobata, Masaaki; Fujimori, Shinichi; Takeda, Yukiharu; Yamagami, Hiroshi; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Physical Review B, 104(16), p.165124_1 - 165124_8, 2021/10

https://doi.org/10.1103/PhysRevB.104.165124

Alternation of magnetic anisotropy accompanied by metal-insulator transition in strained ultrathin manganite heterostructures

Kobayashi, Masaki*; Anh, L. D.*; Suzuki, Masahiro*; Kaneta-Takada, Shingo*; Takeda, Yukiharu; Fujimori, Shinichi; Shibata, Goro*; Tanaka, Arata*; Tanaka, Masaaki*; Oya, Shinobu*; et al.

Physical Review Applied (Internet), 15(6), p.064019_1 - 064019_10, 2021/06

https://doi.org/10.1103/PhysRevApplied.15.064019

Soft X-ray irradiation induced metallization of layered TiNCl

Kataoka, Noriyuki*; Tanaka, Masashi*; Hosoda, Wataru*; Taniguchi, Takumi*; Fujimori, Shinichi; Wakita, Takanori*; Muraoka, Yuji*; Yokoya, Takashi*

Journal of Physics; Condensed Matter, 33(3), p.035501_1 - 035501_6, 2021/01

https://doi.org/10.1088/1361-648X/abbbc3

Evolution of Fe 3 impurity band state as the origin of high Curie temperature in the -type ferromagnetic semiconductor (Ga,Fe)Sb

Takeda, Takahito*; Sakamoto, Shoya*; Araki, Kosei*; Fujisawa, Yuita*; Anh, L. D.*; Tu, N. T.*; Takeda, Yukiharu; Fujimori, Shinichi; Fujimori, Atsushi*; Tanaka, Masaaki*; et al.

Physical Review B, 102(24), p.245203_1 - 245203_8, 2020/12

https://doi.org/10.1103/PhysRevB.102.245203

Two-parameter model for optimizing target beam distribution with an octupole magnet

Meigo, Shinichiro; Oi, Motoki; Fujimori, Hiroshi*

Physical Review Accelerators and Beams (Internet), 23(6), p.062802_1 - 062802_24, 2020/06

https://doi.org/10.1103/PhysRevAccelBeams.23.062802

As hadron accelerators for such as the ADS and spallation neutron source achieve increasing beam power, damage to targets is becoming increasingly severe. To mitigate this damage, nonlinear beam optics based on octupole magnets is attractive. Nonlinear optics can decrease the beam-focusing hazard due to failure of the rastering magnet. As a side effect of nonlinear optics, the beam size is known to expand drastically compared with linear optics. Nonlinear effects have been studied via a simplified filament model that ignores beam-divergence spread at the octupole magnet. In this study, a new generalized model is proposed for application to an octupole magnet, regardless of the filament-model approximation. It is found that the transverse distribution obtained by beam tracking can be specified by the introduction of only two parameters, namely the normalized octupole strength of and the of the phase advance. To achieve the two antagonistic requirements of reduction of the beam-peak density and minimization of the beam loss, the transverse distribution is surveyed for a large range of beam position. It is found that a bell-shaped distribution with 1 and 3 can satisfy requirements. This result is applied to beam transport in the spallation neutron source at J-PARC. The calculation result given by the present model shows good agreement with the experimental data, and the peak current density is reduced by 50% compared with the linear-optics case.