Three-dimensional bulk Fermi surfaces and Weyl crossings of CoMnGa thin films underneath a protection layer

Kono, Takashi*; Kakoki, Masaaki*; Yoshikawa, Tomoki*; Wang, X.*; Sumida, Kazuki; Muro, Takayuki*; Goto, Kazuki*; Sakuraba, Yuya*; Umetsu, Rie*; Kimura, Akio*

Physical Review B, 104(19), p.195112_1 - 195112_8, 2021/11

https://doi.org/10.1103/PhysRevB.104.195112

Angle-resolved photoelectron spectroscopy utilizing soft X-ray synchrotron radiation was applied to Heusler-type CoMnGa thin films that have a 1-nm Al capping layer. The bulk Fermi surfaces and band structures varied along the out-of-plane momentum, stemming from the three-dimensional crystal structure, in the absence of any in situ surface treatment. In addition, there were characteristic intersecting bands (Weyl cones), with crossing points near the Fermi level, which were consistent with computed results. The Weyl cones are of bulk origin and are responsible for the high anomalous Nernst and the anomalous Hall coefficients. A close comparison of the experimental band structures in CoMnGe and CoMnGa indicated that the rigid band picture is valid in both alloys and that fine carrier tuning is possible by replacing Ga with Ge to improve the anomalous conductivity.

Element-specific density of states of CoMnGe revealed by resonant photoelectron spectroscopy

Kono, Takashi*; Kakoki, Masaaki*; Yoshikawa, Tomoki*; Wang, X.*; Sumida, Kazuki*; Miyamoto, Koji*; Muro, Takayuki*; Takeda, Yukiharu; Saito, Yuji; Goto, Kazuki*; et al.

Physical Review B, 100(16), p.165120_1 - 165120_6, 2019/10

https://doi.org/10.1103/PhysRevB.100.165120

Interaction of rare earth elements and components of the Horonobe deep groundwater

Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Kubota, Takumi*; Kimuro, Shingo*; Amano, Yuki; Miyakawa, Kazuya; Iwatsuki, Teruki; Mizuno, Takashi; Sasaki, Takayuki*; et al.

Chemosphere, 168, p.798 - 806, 2017/02

https://doi.org/10.1016/j.chemosphere.2016.10.133

For better understanding of the migration behavior of minor actinides (MA) in deep groundwater, the interaction of doped rare earth elements (REEs) and components in Horonobe deep groundwater was studied. Appx. 10 ppb of rare earth elements, i.e., Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb were doped to the sample groundwater collected from a packed sections in borehole drilled from 140 m depth experiment drift of Horonobe underground research laboratory (URL), Hokkaido, Japan. Then, that groundwater was sequentially filtrated by 0.2 micron pore filter, 10 kDa, 3 kDa and 1 kDa of nominal molecular weight limit (NMWL) ultrafilters by keeping inert condition. After that, the filtrate solutions were analyzed by ICP-MS to determine the concentrations of retained REEs at each filtration steps, while the used filters were analyzed by the neutron activation analysis (NAA) and TOF-SIMS element mapping to know the amount and chemical speciation of trapped fraction of the REEs on each filter. A remarkable relation between the retention ratios of REEs in the filtrate solutions and the ionic radius was observed, i.e., smaller rare earth element solves more in liquid phase under the Horonobe groundwater condition. NAA and TOF-SIMS analyses revealed that certain portions of REEs were trapped by 0.2 micron pore filters as rare earth phosphates which corresponded with the predicted predominant species by a chemical equilibrium calculation for the Horonobe groundwater condition, while small portions of colloidal REEs were trapped by 10 kDa and 3 kDa NMWL ultrafilters. The result suggested that phosphate anion plays an important role in the chemical behavior of REEs in saline (seawater based) groundwater, which could be referred for the prediction of migration behavior of trivalent actinide released from the repository of radioactive waste in far future.

Characteristic oxygen -edge circular dichroism spectra of amino acid films by improved measurement technique

Izumi, Yudai*; Tanabe, Maiko*; Imazu, Akiko*; Mimoto, Aki*; Tanaka, Masahito*; Agui, Akane; Muro, Takayuki*; Nakagawa, Kazumichi*

Journal of Chemical Physics, 138(7), p.074305_1 - 074305_10, 2013/02

https://doi.org/10.1063/1.4790599

no abstracts in English

Electronic structure of lithium amide

Kamakura, Nozomu; Takeda, Yukiharu; Saito, Yuji; Yamagami, Hiroshi; Tsubota, Masami*; Paik, B.*; Ichikawa, Takayuki*; Kojima, Yoshitsugu*; Muro, Takayuki*; Kato, Yukako*; et al.

Physical Review B, 83(3), p.033103_1 - 033103_4, 2011/01

https://doi.org/10.1103/PhysRevB.83.033103

The electronic structure of lithium amide, which is lightweight complex hydride expected as a high-capacity hydrogen storage material, is investigated by N 1 soft X-ray emission spectroscopy (XES) and absorption spectroscopy (XAS). The overall feature of the electronic structure of lithium amide by the XES and XAS is consistent with the band calculation, while the strongly hybridized state with H 1 is located at higher binding energy than the band calculation.

Measurement and comparison of absolute value of soft X-ray natural circular dichroism of serine and alanine

Izumi, Yudai*; Imazu, Akiko*; Mimoto, Aki*; Tanaka, Masafumi*; Nakagawa, Kazumichi*; Tanaka, Masahito*; Agui, Akane; Muro, Takayuki*

Journal of Physics; Conference Series, 190, p.012209_1 - 012209_4, 2009/11

https://doi.org/10.1088/1742-6596/190/1/012209

Soft X-ray natural circular dichroism spectra of serine and alaninethin films, were measured in absolute value with the focus at the oxygen 1s to transition of COO. The soft X-ray natural circular dichroism spectra intensity of L-Ala was about ten times as large as that of L-Ser. Those differences would reflect the chiral environment of the core hole oxygen atoms of COO.

Soft-X-ray high-resolution photoemission study on the valence transitions in YbInCu

Sato, Hitoshi*; Yoshikawa, Kunta*; Hiraoka, Koichi*; Arita, Masashi*; Fujimoto, Koji*; Kojima, Kenichi*; Muro, Takayuki*; Saito, Yuji; Sekiyama, Akira*; Suga, Shigemasa*; et al.

Physical Review B, 69(16), p.165101_1 - 165101_6, 2004/04

https://doi.org/10.1103/PhysRevB.69.165101

no abstracts in English

Prominent quasiparticle peak in the photoemission spectrum of the metallic phase of VO

Mo, S.-K.*; Denlinger, J. D.*; Kim, H.-D.*; Park, J.-H.*; Allen, J. W.*; Sekiyama, Akira*; Yamasaki, Atsushi*; Kadono, Koji*; Suga, Shigemasa*; Saito, Yuji; et al.

Physical Review Letters, 90(18), p.186403_1 - 186403_4, 2003/05

A2003-0178.pdf:0.18MB

https://doi.org/10.1103/PhysRevLett.90.186403

no abstracts in English

Bulk-sensitive photoemission spectroscopy of FeMoO double perovskites (=Sr, Ba)

Kang, J.-S.*; Kim, J. H.*; Sekiyama, Akira*; Kasai, Shuichi*; Suga, Shigemasa*; Han, S. W.*; Kim, K. H.*; Muro, Takayuki*; Saito, Yuji; Hwang, C.*; et al.

Physical Review B, 66(11), p.113105_1 - 113105_4, 2002/09

https://doi.org/10.1103/PhysRevB.66.113105

The electronic structures of SrFeMoO (SFMO) and BaFeMoO (BFMO) double perovskites have been investigated using Fe 2p-3d resonant photoemission spectroscopy (PES) and the Cooper minimum in the Mo 4d photoionization cross section. The states close to the Fermi level are found to have a strongly mixed Mo–Fe t character, indicating that the Fe valence is far from pure 3+. The Fe 2p x-ray absorption spectroscopy spectra reveal the mixed-valent Fe –Fe configurations, and a larger Fe component for BFMO than for SFMO, suggesting an operative double exchange interaction. The valence-band PES spectra reveal good agreement with the local-spin-density-approximation (LSDA+U) calculation.

Orbital angular momentum and interpretation of core-absorption magnetic circular dichroism on the band picture in Co-based Heusler alloys CoSn (=Ti, Zr, and Nb)

Yamasaki, Atsushi*; Imada, Shin*; Arai, Ryuji*; Utsunomiya, Hiroshi*; Suga, Shigemasa*; Muro, Takayuki*; Saito, Yuji; Kanomata, Takeshi*; Ishida, Shoji*

Physical Review B, 65(10), p.104410_1 - 104410_6, 2002/03

https://doi.org/10.1103/PhysRevB.65.104410

The magnetic circular dichroism (MCD) of core-level absorption [x-ray absorption spectroscopy (XAS)] spectra in the soft x-ray region has been measured for the ferromagnetic Heusler alloys CoTiSn, CoZrSn, and CoNbSn. The many-peak structures which are clearly observed in the Co 2p-3d XAS-MCD spectra cannot be well explained by atomic multiplet calculations but are better explained by the Co 3d unoccupied states predicted by linear muffin-tin orbital atomic sphere approximation band structure calculations. The MCD spectra show an obvious contribution of the orbital angular momentum component to the magnetic moment in these alloys. The ratio between the orbital angular momentum and spin derived from the MCD spectra varies by more than a factor of 2 within these alloys. The mechanism of this variation is discussed in comparison with the band structure calculations.