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Journal Articles

Fermi surface and magnetic properties of antiferromagnet EuBi$$_3$$

Nakamura, Ai*; Hiranaka, Yuichi*; Hedo, Masato*; Nakama, Takao*; Tatetsu, Yasutomi*; Maehira, Takahiro*; Miura, Yasunao*; Mori, Akinobu*; Tsutsumi, Hiroki*; Hirose, Yusuke*; et al.

Journal of the Physical Society of Japan, 82(12), p.124708_1 - 124708_6, 2013/12

 Times Cited Count:18 Percentile:72.91(Physics, Multidisciplinary)

Journal Articles

NMR study of the semimetallic compound UCoGa$$_5$$

Kambe, Shinsaku; Sakai, Hironori; Kato, Harukazu*; Tokunaga, Yo; Fujimoto, Tatsuya*; Walstedt, R. E.*; Ikeda, Shugo; Maehira, Takahiro*; Haga, Yoshinori; Onuki, Yoshichika

Physical Review B, 76(2), p.024411_1 - 024411_6, 2007/07

 Times Cited Count:6 Percentile:33.03(Materials Science, Multidisciplinary)

We report NMR studies on a single crystal of UCoGa$$_5$$, which has the same tetragonal HoCoGa$$_5$$ (115) structure as the$$d$$-wave high-$$T_c$$ superconductor PuCoGa$$_5$$. The spin-lattice relaxation rate ($$1/T_1$$) in UCoGa$$_5$$ issmall comparing with those of other actinide 115 compounds. This fact is consistent with a semi-metallic nature of UCoGa$$_5$$ suggested by de Haas-van Alphen effect measurements and band calculations. From comparison of $$1/T_1$$ at crystallografically different Ga and Co sites and the static susceptibility, an existence of two bands with rather different characters is revealed.

Journal Articles

Relativistic band-structure calculations for electronic properties of actinide dioxides

Maehira, Takahiro*; Hotta, Takashi

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.754 - 756, 2007/03

 Times Cited Count:16 Percentile:59.64(Materials Science, Multidisciplinary)

Energy band structures of actinide dioxides AnO$$_2$$ (An=Th, U, Np, and Pu) are investigated by a relativistic linear augmented-plane-wave method with the exchange-correlation potential in a local density approximation (LDA). It is found in common that the energy bands in the vicinity of the Fermi level are mainly due to the hybridization between actinide 5f and oxygen 2p electrons. By focusing on the crystalline electric field states, we point out the problem in the application of the LDA to AnO$$_2$$.

Journal Articles

Relativistic band-structure calculation for PrCoIn$$_5$$; A Theoretical approach to Pr-based compound from itinerant picture

Maehira, Takahiro*; Hotta, Takashi

Journal of the Physical Society of Japan, 75(Suppl.), p.262 - 265, 2006/08

We calculate energy band structure and the Fermi surface of PrCoIn$$_5$$ by using a self-consistent relativistic linear augmented-plane-wave method with the exchange and correlation potential in a local density approximation. It is found in common with other rare-earth and actinide compounds with the HoCoGa$$_5$$-type tetragonal crystal structure that the energy bands in the vicinity of the Fermi level are mainly due to the large hybridization between Pr $$4f$$ and In $$5p$$ electrons. The Fermi surface is found to consist of a large quasi-two-dimensional hole sheet. We discuss the comparison of our Fermi surface with experimental results on PrCoIn$$_5$$.

Journal Articles

Electronic structure and the Fermi surface of ThRhIn$$_5$$ in comparison with uranium and transuranium compounds

Maehira, Takahiro*; Hotta, Takashi

Physica B; Condensed Matter, 378-380, p.1027 - 1028, 2006/05

 Times Cited Count:0 Percentile:0(Physics, Condensed Matter)

By using a relativistic linear augmented-plane-wave method, we clarify energy band structure and the Fermi surfaces of recently synthesized thorium compound ThRhIn$$_5$$. We find several cylindrical Fermi surface sheets, which are similar to those of CeTIn$$_5$$ (T=Ir and Co), PuTGa$$_5$$ (T=Co and Rh), and AmCoGa$$_5$$. We discuss such similarity among the compounds including rare-earth or actinide ions with different $$f$$ electron numbers.

Journal Articles

Electronic properties of transuranium compounds with HoCoGa$$_5$$-type tetragonal crystal structure

Maehira, Takahiro*; Hotta, Takashi; Ueda, Kazuo*; Hasegawa, Akira*

New Journal of Physics (Internet), 8(2), p.24_1 - 24_20, 2006/02

 Times Cited Count:16 Percentile:66.17(Physics, Multidisciplinary)

By using a relativistic band-structrue calculation method, we investigate energy band structures and the Fermi surfaces of NpTGa$$_5$$, PuTGa$$_5$$, and AmCoGa$$_5$$ with transition metal atoms T. It is found in common that the energy bands in the vicinity of the Fermi level are mainly due to the large hybridization between $$5f$$ and Ga $$4p$$ electrons. For PuTGa$$_5$$, we observe several cylindrical sheets of Fermi surfaces with large volume for T=Co, Rh, and Ir. It is also found that the Fermi surfaces of NpFeGa$$_5$$, NpCoGa$$_5$$, and NpNiGa$$_5$$ are similar to those of UCoGa$$_5$$, UNiGa$$_5$$, and PuCoGa$$_5$$, respectively, except for small details. For AmCoGa$$_5$$, the Fermi surfaces are found to consist of large cylindrical electron sheets and small closed hole sheets, similar to PuCoGa$$_5$$. The similarity is basically understood by a rigid-band picture.

Journal Articles

Electronic structure and the fermi surface of UTGa$$_{5}$$ (T=Fe, Co, Rh)

Maehira, Takahiro; Higuchi, Masahiko*; Hasegawa, Akira*

Physica B; Condensed Matter, 329-333(1-4), p.574 - 575, 2003/05

 Times Cited Count:20 Percentile:68.29(Physics, Condensed Matter)

The relativistic energy-band calculations have been carried out for $${rm UFeGa_{5}}$$, $${rm UCoGa_{5}}$$ and $${rm URhGa_{5}}$$ under the assumption that 5$$f$$-electrons are itinerant. A hybridization between the U 5$$f$$ state and Ga 4$$p$$ state occurs in the vicinity of the Fermi level. The Fermi surface of $${rm UCoGa_{5}}$$ is quite similar to that of $${rm URhGa_{5}}$$, which are all small in size and closed in topology. $${rm UFeGa_{5}}$$ has the quasi-two-dimensional Fermi surface which looks like a lattice structure.

Journal Articles

Electronic structure and the Fermi surface of PuCoGa$$_5$$ and NpCoGa$$_{5}$$

Maehira, Takahiro; Hotta, Takashi; Ueda, Kazuo; Hasegawa, Akira*

Physical Review Letters, 90(20), p.207007_1 - 207007_4, 2003/05

 Times Cited Count:93 Percentile:92.99(Physics, Multidisciplinary)

By using a relativistic linear augmented-plane-wave method, we clarify energy band structures and Fermi surfaces of recently discovered plutonium-based superconductor PuCoGa$$_5$$. We find several cylindrical sheets of Fermi surfaces with large volume, quite similar to CeMIn$$_5$$ (M=Ir and Co) isostructural with PuCoGa$$_5$$, in spite of different $$f$$-electron numbers between Ce$$^{3+}$$ and Pu$$^{3+}$$ ions. This similarity is simply understood by a concept of electron-hole conversion in a tight binding model constructed based on the $$j$$-$$j$$ coupling scheme. Due to the present results, we provide a possible scenario to explain why a transition temperature is so high as 18.5K in PuCoGa$$_5$$.

Journal Articles

Relativistic band-structure calculations for CeTIn$$_5$$(T=Ir and Co) and analysis of the energy bands by using tight-binding method

Maehira, Takahiro; Hotta, Takashi; Ueda, Kazuo; Hasegawa, Akira*

Journal of the Physical Society of Japan, 72(4), p.854 - 864, 2003/04

 Times Cited Count:73 Percentile:90.69(Physics, Multidisciplinary)

In order to investigate electronic properties of recently discovered heavy fermion superconductors CeTIn$$_5$$ (T=Ir and Co), we employ the relativistic linear augmented-plane-wave (RLAPW) method to clarify the energy band structures and Fermi surfaces of those materials.The obtained energy bands mainly due to the large hybridization between Ce $$4f$$ and In 5$$p$$ states well reproduce the Fermi surfaces consistent with the de Haas-van Alphen experimental results. For the purpose, we construct a tight-binding model for CeTIn$$_5$$ by including $$f$$-$$f$$ and $$p$$-$$p$$ hoppings as well as $$f$$-$$p$$ hybridization, which are expressed by the Slater-Koster integrals, determined by the direct comparison with the band-calculation result. Similarity and difference between CeIrIn$$_5$$ and CeCoIn$$_5$$ are discussed based on the obtained tight-binding model, suggesting a significant importance of the effect of crystalline electric field to understand the difference in electronic properties among CeTIn$$_5$$.

Journal Articles

Fermi surface study in uranium-based intermetallic compounds

Haga, Yoshinori; Yamamoto, Etsuji; Tokiwa, Yoshifumi; Aoki, Dai*; Inada, Yoshihiko*; Settai, Rikio*; Maehira, Takahiro; Yamagami, Hiroshi*; Harima, Hisatomo*; Onuki, Yoshichika

Journal of Nuclear Science and Technology, 39(Suppl.3), p.56 - 62, 2002/11

Fermi surfaces of uranium compounds are investigated by de Haas-van Alphen (dHvA) effect. Band calculations well reproduce the Fermi surfaces of non-magnetic itinerant systems such as USi$$_{3}$$, UC, UAl$$_{3}$$. Fermi surfaces of the heavy fermion compounds, where the strong correlation between carriers are important, are also explained by band calculations, except for their unusually large mass enhancement. We have also observed dHvA oscillations in the superconducting mixed states in heavy fermion superconductors such as URu$$_{2}$$Si$$_{2}$$, UPd$$_{2}$$Al$$_{3}$$ and CeRu$$_{2}$$. A significan field dependence of cyclotron effective mass and scattering life time were observed.

Journal Articles

Spin fluctuation-induced superconductivity controlled by orbital fluctuation

Takimoto, Tetsuya; Hotta, Takashi; Maehira, Takahiro; Ueda, Kazuo*

Journal of Physics; Condensed Matter, 14(21), p.L369 - L375, 2002/06

 Times Cited Count:53 Percentile:87.07(Physics, Condensed Matter)

A microscopic Hamiltonian of the orbitally-degenerated Hubbard model reflecting correct symmetry of $$f$$-orbitals is proposed to discuss superconductivity in $$f$$-electron systems. In the degenerated region, cancellation among spin and orbital fluctuations basically destabilizes singlet superconductivity, while $$d$$-wave superconductivity mediated by spin fluctuations emerges out of the suppression of orbital fluctuations due to the lift of orbital degeneracy. We argue that the present scenario can be applied to recently discovered Ce-based heavy-fermion superconductor.

Journal Articles

Electronic structure and the Fermi surface of UBe$$_{13}$$

Maehira, Takahiro; Higashitani, Atsushi*; Higuchi, Masahiko*; Yasuhara, Hiroshi*; Hasegawa, Akira*

Physica B; Condensed Matter, 312-313(1-4), p.103 - 105, 2002/03

 Times Cited Count:12 Percentile:54.45(Physics, Condensed Matter)

UBe$$_{13}$$ is a typical heavy-fermion superconductor compound. The lowtemperature electronic specific heat coefficient has the anomalous large value, $$gamma_{exp}$$=1.1J/K$$^2$$mol, which is the largest among the heavy fermion uranium compounds. It also becomes the superconductor below T$$_C$$=0.85K. Therefore, UBe$$_{13}$$ is an important material as a strongly correlated electron system, and it is necessary to study from both sides of the theory and the experiment. The measurement suggests that the Fermi surface of UBe$$_{13}$$ may consist of small sheets. The energy band structure and the Fermi surface for UBe$$_{13}$$ are calculated by the relativistic linear APW method.

Journal Articles

Fermi surface of heavy Fermion compounds CeTIn$$_5$$ (T=Rh, Ir, and Co); Band-calculation and tight-binding approach

Maehira, Takahiro; Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*; Higuchi, Masahiko*; Hasegawa, Akira*

Journal of the Physical Society of Japan, Vol.71, Supplement, p.285 - 287, 2002/00

 Times Cited Count:8 Percentile:50.89(Physics, Multidisciplinary)

Recently a new family of Ce-based heavy fermion superconductor $${rm CeTIn_{5}}$$ (T=Rh, Ir, and Co) has been reported. The dHvA effect has been successfully observed in $${rm CeIrIn_{5}}$$ and $${rm CeCoIn_{5}}$$.The angular dependence of dHvA branches is well explained by a quasi-two dimensional Fermi surface(F.S.). In order to clarify band structures of Ce-115 systems such as CeIrIn$$_5$$ and CeCoGa$$_5$$, two-step strategy is here employed. In the first step, the F.S. are derived by using the RLAPW method. In the next step, the band structure near the Fermi level is reanalyzed by using a simple tight-binding model. Namely, hopping amplitudes of $$f$$-electrons between neighboring Ce ions are parameterized to reproduce the F.S. obtained in the band-calculation. By further adding the Coulomb interaction terms into this tight-binding model, a simple many-body Hamiltonian for Ce-compounds can be constructed. This Hamiltonian opens a way to discuss magnetism and superconductivity in $$f$$-electron systems from the microscopic viewpoint.

Journal Articles

De Haas-van Alphen effect and Fermi surface in UC

Yamamoto, Etsuji; Haga, Yoshinori; Maehira, Takahiro*; Inada, Yoshihiko*; Murakawa, Masao*; Onuki, Yoshichika; Hasegawa, Akira*

Journal of Magnetism and Magnetic Materials, 226-230(Part.1), p.51 - 53, 2001/05

no abstracts in English

Journal Articles

Electronic structure and the Fermi surface of UC and UGe$$_{3}$$

Maehira, Takahiro; Higuchi, Masahiko*; Yamamoto, Etsuji; Onuki, Yoshichika; Hasegawa, Akira*

Journal of the Physical Society of Japan, Vol.70, Supplement A, p.43 - 45, 2001/05

no abstracts in English

15 (Records 1-15 displayed on this page)
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