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Journal Articles

Polarization dependence of soft X-ray absorption spectroscopy on the heavy fermion superconductor CeNi$$_{2}$$Ge$$_{2}$$

Fujiwara, Hidenori*; Nakatani, Yasuhiro*; Aratani, Hidekazu*; Kanai-Nakata, Yuina*; Yamagami, Kohei*; Hamamoto, Satoru*; Kiss, Takayuki*; Sekiyama, Akira*; Tanaka, Arata*; Ebihara, Takao*; et al.

New Physics; Sae Mulli, 73(12), p.1062 - 1066, 2023/12

Journal Articles

Impact of the ground-state 4${it f}$ symmetry for anisotropic ${it cf}$ hybridization in the heavy-fermion superconductor CeNi$$_{2}$$Ge$$_{2}$$

Fujiwara, Hidenori*; Nakatani, Yasuhiro*; Aratani, Hidekazu*; Kanai, Yuina*; Yamagami, Kohei*; Hamamoto, Satoru*; Kiss, Takayuki*; Yamasaki, Atsushi*; Higashiya, Atsushi*; Imada, Shin*; et al.

Physical Review B, 108(16), p.165121_1 - 165121_10, 2023/10

Journal Articles

Mn L$$_{2,3}$$-edge EXAFS and magnetic EXAFS studies on the halfmetallic ferromagnet Co$$_{2}$$MnSi

Kogo, Junya*; Fujiwara, Hidenori*; Sekiyama, Akira*; Saito, Yuji; Umetsu, Rie*; Niki, Kaori*

Journal of the Physical Society of Japan, 91(3), p.034702_1 - 034702_12, 2022/03

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

Detecting halfmetallic electronic structures of spintronic materials in a magnetic field

Fujiwara, Hidenori*; Umetsu, Rie*; Kuroda, Fumiaki*; Miyawaki, Jun*; Kashiuchi, Toshiyuki*; Nishimoto, Kohei*; Nagai, Kodai*; Sekiyama, Akira*; Irizawa, Akinori*; Takeda, Yukiharu; et al.

Scientific Reports (Internet), 11(1), p.18654_1 - 18654_9, 2021/09

 Times Cited Count:0 Percentile:0(Multidisciplinary Sciences)

Journal Articles

Insight into Kondo screening in the intermediate-valence compound SmOs$$_4$$Sb$$_{12}$$ uncovered by soft X-ray magnetic circular dichroism

Saito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.

Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10

 Times Cited Count:1 Percentile:6.21(Materials Science, Multidisciplinary)

Journal Articles

Revising the 4${it f}$ symmetry in CeCu$$_{2}$$Ge$$_{2}$$; Soft X-ray absorption and hard X-ray photoemission spectroscopy

Aratani, Hidekazu*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Kawada, Moeki*; Kanai, Yuina*; Yamagami, Kohei*; Fujioka, Shuhei*; Hamamoto, Satoru*; Kuga, Kentaro*; Kiss, Takayuki*; et al.

Physical Review B, 98(12), p.121113_1 - 121113_6, 2018/09

AA2018-0352.pdf:1.16MB

 Times Cited Count:4 Percentile:26.15(Materials Science, Multidisciplinary)

Journal Articles

Evidence for momentum-dependent heavy fermionic electronic structures; Soft X-ray ARPES for the superconductor CeNi$$_{2}$$Ge$$_{2}$$ in the normal state

Nakatani, Yasuhiro*; Aratani, Hidekazu*; Fujiwara, Hidenori*; Mori, Takeo*; Tsuruta, Atsushi*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; et al.

Physical Review B, 97(11), p.115160_1 - 115160_7, 2018/03

AA2018-0003.pdf:1.65MB

 Times Cited Count:3 Percentile:20.97(Materials Science, Multidisciplinary)

Journal Articles

Electronic structure and magnetic properties of the half-metallic ferrimagnet Mn$$_{2}$$VAl probed by soft X-ray spectroscopies

Nagai, Kodai*; Fujiwara, Hidenori*; Aratani, Hidekazu*; Fujioka, Shuhei*; Yomosa, Hiroshi*; Nakatani, Yasuhiro*; Kiss, Takayuki*; Sekiyama, Akira*; Kuroda, Fumiaki*; Fujii, Hitoshi*; et al.

Physical Review B, 97(3), p.035143_1 - 035143_8, 2018/01

AA2017-0644.pdf:1.01MB

 Times Cited Count:21 Percentile:70.56(Materials Science, Multidisciplinary)

We have studied the electronic structure of ferrimagnetic Mn$$_{2}$$VAl single crystals by means of soft X-ray absorption spectroscopy (XAS), X-ray absorption magnetic circular dichroism (XMCD), and resonant soft X-ray inelastic scattering (RIXS). We have successfully observed the XMCD signals for all the constituent elements. The Mn L$$_{2,3}$$ XAS and XMCD spectra are reproduced by spectral simulations based on density-functional theory, indicating the itinerant character of the Mn 3$$d$$ states. On the other hand, the V 3$$d$$ electrons are rather localized since the ionic model can qualitatively explain the V L$$_{2,3}$$ XAS and XMCD spectra. This picture is consistent with local $$dd$$ excitations revealed by the V L$$_{3}$$ RIXS.

Journal Articles

Experimental observation of temperature and magnetic-field evolution of the 4${it f}$ states in CeFe$$_{2}$$ revealed by soft X-ray magnetic circular dichroism

Saito, Yuji; Yasui, Akira*; Fuchimoto, Hiroto*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Imada, Shin*; Narumi, Yasuo*; Kindo, Koichi*; Takahashi, Minoru*; Ebihara, Takao*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07

AA2017-0611.pdf:0.36MB

 Times Cited Count:2 Percentile:17.22(Materials Science, Multidisciplinary)

We revisit the delocalized character of the 4$$f$$ states of CeFe$$_2$$ in the ferromagnetically ordered phase by X-ray magnetic circular dichroism (XMCD) in X-ray absorption spectroscopy (XAS) with improved data quality using single crystals. Surprisingly, the Ce $$M_{4,5}$$ XMCD spectral shape changes significantly as a function of temperature and applied magnetic field, with no concomitant changes in the spectral shape of the Ce $$M_{4,5}$$ XAS as well as the Fe $$L_{2,3}$$ XAS and XMCD. This unusual behavior is characterized by the $$J=7/2$$ states in a 4$$f^1$$ configuration mixed into the $$J=5/2$$ ground state. Such extreme sensitivity of the Ce 4$$f$$ states to the external perturbations can be related to the magnetic instability toward an antiferromagnetic phase in CeFe$$_2$$. Our experimental data presented here provide valuable insights into the underlying physics in strongly-hybridized ferromagnetic Ce compounds.

Journal Articles

Circular dichroism in resonant angle-resolved photoemission spectra of LaNi$$_{2}$$Ge$$_{2}$$

Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Aratani, Hidekazu*; Mori, Takeo*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; Yamagami, Hiroshi*; et al.

Journal of Electron Spectroscopy and Related Phenomena, 220, p.50 - 53, 2017/01

 Times Cited Count:1 Percentile:17.26(Spectroscopy)

We report the soft X-ray angle-resolved photoemission study for LaNi$$_{2}$$Ge$$_{2}$$ to reveal the electronic structures derived from non-4$$f$$ bands of the heavy fermion compound CeNi$$_{2}$$Ge$$_{2}$$. The photoemission spectra recorded at the La M$$_{4,5}$$ absorption edges clearly show the enhancement of the La 5$$d$$ components in the valence band spectra. The circular dichroism of photoemission spectra reveals the band-dependent dichroic response due to the orbital symmetry.

Journal Articles

Electronic structures of ferromagnetic CeAgSb$$_{2}$$; Soft X-ray absorption, magnetic circular dichroism, and angle-resolved photoemission spectroscopies

Saito, Yuji; Fujiwara, Hidenori*; Yamaguchi, Takashi*; Nakatani, Yasuhiro*; Mori, Takeo*; Fuchimoto, Hiroto*; Kiss, Takayuki*; Yasui, Akira*; Miyawaki, Jun*; Imada, Shin*; et al.

Journal of the Physical Society of Japan, 85(11), p.114713_1 - 114713_7, 2016/11

 Times Cited Count:13 Percentile:68.29(Physics, Multidisciplinary)

We report on the electronic structures of ferromagnetic CeAgSb$$_{2}$$ using soft X-ray absorption (XAS), magnetic circular dichroism (XMCD), and angle-resolved photoemission (ARPES) spectroscopies. The Ce $$M_{4,5}$$ XAS spectra show very small satellite structures, reflecting a strongly localized character of the Ce 4${it f}$ electrons. The linear dichroism effects in the Ce $$M_{4,5}$$ XAS spectra demonstrate the ground-state Ce 4${it f}$ symmetry of $$Gamma$$$$_{6}$$, the spatial distribution of which is directed along the ${it c}$-axis. Nevertheless, ARPES spectra at the Ce 3$$d$$-4$$f$$ resonance show the momentum dependence of the intensity ratio between Ce 4$$f^{1}_{5/2}$$ and 4$$f^{1}_{7/2}$$ peaks in a part of the Brillouin zone, suggesting the non negligible momentum-dependent hybridization effect between the Ce 4${it f}$ and the conduction electrons. This is associated with the moderate mass enhancement in CeAgSb$$_{2}$$.

Journal Articles

Three-dimensional electronic structures and the metal-insulator transition in Ruddlesden-Popper iridates

Yamasaki, Atsushi*; Fujiwara, Hidenori*; Tachibana, Shoichi*; Iwasaki, Daisuke*; Higashino, Yuji*; Yoshimi, Chiaki*; Nakagawa, Koya*; Nakatani, Yasuhiro*; Yamagami, Kohei*; Aratani, Hidekazu*; et al.

Physical Review B, 94(11), p.115103_1 - 115103_10, 2016/11

AA2016-0587.pdf:2.55MB

 Times Cited Count:17 Percentile:61.47(Materials Science, Multidisciplinary)

In this study, we systematically investigate three-dimensional(3D) momentum-resolved electronic structures of Ruddlesden-Popper-type iridium oxides Sr$$_{n+1}$$Ir$$_{n}$$O$$_{3n+1}$$ using soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES). Our results provide direct evidence of an insulator-to-metal transition that occurs upon increasing the dimensionality of the IrO$$_{2}$$-plane structure. This transition occurs when the spin-orbit-coupled $$j_{eff}$$ = 1/2 band changes its behavior in the dispersion relation and moves across the Fermi energy. By scanning the photon energy over 350 eV, we reveal the 3D Fermi surface in SrIrO$$_{3}$$ and $$k_{z}$$-dependent oscillations of photoelectron intensity in Sr$$_{3}$$Ir$$_{2}$$O$$_{7}$$. To corroborate the physics deduced using low-energy ARPES studies, we propose to utilize SX-ARPES as a powerful complementary technique, as this method surveys more than one whole Brillouin zone and provides a panoramic view of electronic structures.

Journal Articles

Probing strongly correlated 4$$f$$-orbital symmetry of the ground state in Yb compounds by linear dichroism in core-level photoemission

Mori, Takeo*; Kitayama, Satoshi*; Kanai, Yuina*; Naimen, Sho*; Fujiwara, Hidenori*; Higashiya, Atsushi*; Tamasaku, Kenji*; Tanaka, Arata*; Terashima, Kensei*; Imada, Shin*; et al.

Journal of the Physical Society of Japan, 83(12), p.123702_1 - 123702_5, 2014/12

 Times Cited Count:15 Percentile:68.66(Physics, Multidisciplinary)

We show that the strongly correlated 4$$f$$-orbital symmetry of the ground state is revealed by linear dichroism in core-level photoemission spectra, as we have discovered for YbRh$$_{2}$$Si$$_{2}$$ and YbCu$$_{2}$$Si$$_{2}$$. Theoretical analysis shows us that the linear dichroism reflects the anisotropic charge distributions resulting from a crystalline electric field. We have successfully determined the ground-state 4$$f$$ symmetry for both compounds from the polarization-dependent angle resolved core-level spectra at a temperature well below the first excitation energy. The excited-state symmetry is also probed by temperature dependence of the linear dichroism where the high measurement temperatures are on the order of the crystal-field-splitting energies.

Journal Articles

Direct $$kappa$$-space mapping of the electronic structure in an oxide-oxide interface

Berner, G.*; Sing, M.*; Fujiwara, Hidenori*; Yasui, Akira*; Saito, Yuji; Yamasaki, Atsushi*; Nishitani, Yoshihito*; Sekiyama, Akira*; Pavlenko, N.*; Kopp, T.*; et al.

Physical Review Letters, 110(24), p.247601_1 - 247601_5, 2013/06

 Times Cited Count:128 Percentile:96.59(Physics, Multidisciplinary)

The interface between LaAlO$$_{3}$$ and SrTiO$$_{3}$$ hosts a two-dimensional electron system of itinerant carriers, although both oxides are band insulators. Interface ferromagnetism coexisting with superconductivity has been found and attributed to local moments. Experimentally, it has been established that Ti 3$$d$$ electrons are confined to the interface. Using soft X-ray angle-resolved resonant photoelectron spectroscopy we have directly mapped the interface states in $$kappa$$ space. Our data demonstrate a charge dichotomy. A mobile fraction contributes to Fermi surface sheets, whereas a localized portion at higher binding energies is tentatively attributed to electrons trapped by O vacancies in the SrTiO$$_{3}$$.

Oral presentation

Magnetic circular dichroism in extended X-ray absorption fine structure at the Mn L$$_{2,3}$$ edges on the Heusler alloy Co$$_{2}$$MnSi

Fujiwara, Hidenori*; Kogo, Junya*; Kasahara, Rika*; Nishioka, Takuma*; Fujimoto, Nao*; Nagai, Kodai*; Sekiyama, Akira*; Sumida, Kazuki; Takeda, Yukiharu; Saito, Yuji; et al.

no journal, , 

no abstracts in English

15 (Records 1-15 displayed on this page)
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