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Journal Articles

The $$f$$-electron state of the heavy fermion superconductor NpPd$$_5$$Al$$_2$$ and the isostructural family

Metoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagihala, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.

JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03

Rare earths (4$$f$$) and actinides (5$$f$$) provide variety of interesting states realized with competing interactions between the increasing number of $$f$$ electrons. Since crystal field splitting of many-body $$f$$ electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the $$f$$ electron states of heavy electron compounds NpPd$$_5$$Al$$_2$$ and actinide and rare earth based iso-structural family.

Journal Articles

Structural characterization and magnetic behavior of uranium compound U$$_2$$Pt$$_6$$Al$$_{15}$$

Haga, Yoshinori; Sugai, Takashi*; Matsumoto, Yuji*; Yamamoto, Etsuji

JPS Conference Proceedings (Internet), 29, p.013003_1 - 013003_5, 2020/02

Journal Articles

Novel universality class for the ferromagnetic transition in the low carrier concentration systems UTeS and USeS exhibiting large negative magnetoresistance

Tateiwa, Naoyuki; Haga, Yoshinori; Sakai, Hironori; Yamamoto, Etsuji

Physical Review B, 100(6), p.064413_1 - 064413_7, 2019/08

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

We report the novel critical behavior of magnetization in low carrier concentration systems UTeS and USeS that exhibit the large negative magnetoresistance around the ferromagnetic transition temperatures $$T_{rm C}$$ $$sim$$ 85 and 23 K, respectively. We determine the critical exponents, $$beta$$ for the spontaneous magnetization $$M_{rm s}$$, $$gamma$$ for the magnetic susceptibility $$chi$$, and $$delta$$ for the magnetization isotherm at $$T_{rm C}$$ with several analytical methods. The ferromagnetic states in UTeS and USeS have strong uniaxial magnetic anisotropy. However, the critical exponents in the two compounds are different from those in the three-dimensional Ising system. Similar exponents have been reported for the uranium ferromagnetic superconductors UGe$$_2$$ and URhGe. An important finding is that the novel critical phenomenon appears regardless of the charge carrier density or the degree of the itinerancy of the $$5f$$ electrons.

Journal Articles

Evidence for weak spin-orbit interaction experienced by Cooper pairs in the spin-triplet superconductor UPt$$_3$$; $$^{195}$$Pt-NMR study

Aoyama, Taisuke*; Kotegawa, Hisashi*; Kimura, Noriaki*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika*; To, Hideki*

Journal of the Physical Society of Japan, 88(6), p.064706_1 - 064706_7, 2019/06

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Electronic structure in heavy fermion compound UPd$$_2$$Al$$_3$$ through directional Compton profile measurement

Koizumi, Akihisa*; Kubo, Yasunori*; Yamamoto, Etsuji; Haga, Yoshinori; Sakurai, Yoshiharu*

Journal of the Physical Society of Japan, 88(3), p.034714_1 - 034714_6, 2019/03

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Novel critical behavior of magnetization in URhSi; Similarities to the uranium ferromagnetic superconductors UGe$$_2$$ and URhGe

Tateiwa, Naoyuki; Haga, Yoshinori; Yamamoto, Etsuji

Physical Review B, 99(9), p.094417_1 - 094417_12, 2019/03

 Times Cited Count:4 Percentile:27.63(Materials Science, Multidisciplinary)

We study the critical behavior of dc magnetization in the uranium ferromagnet URhSi around the ferromagnetic phase transition at $$T_{rm C}{,}{sim}{,}$$10 K. The critical exponent $$beta$$ for the spontaneous magnetization below $$T_{rm C}$$, $$gamma$$ for the magnetic susceptibility, and $$delta$$ for the magnetic isotherm at $$T_{rm C}$$ have been determined as $$beta$$ = 0.300 $$pm$$ 0.002, $$gamma$$ = 1.00 $$pm$$ 0.02, and $$delta$$ = 4.32 $$pm$$ 0.04 by the scaling analysis and the critical isotherm analysis. Magnetization has strong uniaxial magnetic anisotropy in the ferromagnetic state of URhSi. However, the universality class of the critical phenomenon does not belong to the 3D Ising system ($$beta$$ = 0.325, $$gamma$$ = 1.241, and $$delta$$ = 4.82). The obtained exponents in URhSi are similar to those in uranium ferromagnetic superconductors UGe$$_2$$ and URhGe. We discuss the static and dynamical magnetic properties of URhSi in comparison with those in UGe$$_2$$, URhGe and UCoGe.

Journal Articles

Manifestation of electron correlation effect in 5$$f$$ states of uranium compounds revealed by 4$$d$$-5$$f$$ resonant photoelectron spectroscopy

Fujimori, Shinichi; Kobata, Masaaki; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*

Physical Review B, 99(3), p.035109_1 - 035109_5, 2019/01

 Times Cited Count:2 Percentile:50.59(Materials Science, Multidisciplinary)

Journal Articles

Strong correlation between ferromagnetic superconductivity and pressure-enhanced ferromagnetic fluctuations in UGe$$_2$$

Tateiwa, Naoyuki; Haga, Yoshinori; Yamamoto, Etsuji

Physical Review Letters, 121(23), p.237001_1 - 237001_6, 2018/12

 Times Cited Count:4 Percentile:39.6(Physics, Multidisciplinary)

We have measured magnetization at high pressure in the uranium ferromagnetic superconductor UGe$$_2$$ and analyzed the magnetic data using Takahashi's spin fluctuation theory. There is a peak in the pressure dependence of the width of the spin fluctuation spectrum in the energy space $$T_0$$ at $$P_x$$, the phase boundary of FM1 and FM2 where the superconducting transition temperature $$T_{rm sc}$$ is highest. This suggests a clear correlation between the superconductivity and pressure-enhanced magnetic fluctuations developed at $$P_x$$. The pressure effect on $${T_{rm Curie}}/{T_0}$$, where $${T_{rm Curie}}$$ is the Curie temperature, suggests that the less itinerant ferromagnetic state FM2 is changed to a more itinerant one FM1 across $$P_x$$. Peculiar features in relations between $$T_0$$ and $$T_{rm sc}$$ in uranium ferromagnetic superconductors UGe$$_2$$, URhGe and UCoGe are discussed in comparison with those in high-$$T_c$$ cuprate and heavy fermion superconductors.

Journal Articles

Localized 5$$f^2$$ states in UPd$$_5$$Al$$_2$$ and valence crossover in the Vicinity of Heavy-Fermion superconductivity

Metoki, Naoto; Haga, Yoshinori; Yamamoto, Etsuji; Matsuda, Masaaki*

Journal of the Physical Society of Japan, 87(11), p.114712_1 - 114712_9, 2018/11

 Times Cited Count:2 Percentile:59.22(Physics, Multidisciplinary)

The localized 5$$f$$ states with 5$$f^2$$ ($$^3H_4$$) configuration of U$$^{4+}$$ ion have been revealed in UPd$$_5$$Al$$_2$$. We found that the low-lying states are the same as PrPd$$_5$$Al$$_2$$ flat orbitals with large $$J_z$$ are stabilized by a two-dimensional CEF potential in the unique crystal structure. The present study involves the valence crossover from tetravalent to trivalent in a series of AnPd$$_5$$Al$$_2$$, demonstrated by lattice and/or transport anomaly as well as many body effects in the vicinity of the boundary. The valence instability plays important role for the unusual heavy fermion superconductivity in NpPd$$_5$$Al$$_2$$.

Journal Articles

Phenomenological approach to study the degree of the itinerancy of the 5$$f$$ electrons in actinide ferromagnets with spin fluctuation theory

Tateiwa, Naoyuki; Posp$'i$$v{s}$il, J.*; Haga, Yoshinori; Sakai, Hironori; Matsuda, Tatsuma*; Yamamoto, Etsuji

Progress in Nuclear Science and Technology (Internet), 5, p.104 - 107, 2018/11

Uranium ferromagnetic superconductors UGe$$_2$$, URhGe and UCoGe have attracted much attention from both theoretical and experimental sides since the same 5$$f$$ electrons underlie carry both the ferromagnetism and superconductivity. Recently, we have analysed 69 uranium, 7 neptunium, and 4 plutonium ferromagnets with spin fluctuation theory originally developed for researches on itinerant ferromagnets in the 3$$d$$ transition metals and their intermetallics. The applicability of the spin fluctuation theory to the actinide 5$$f$$ system has been confirmed and the itinerant character of the 5f electrons is suggested in the actinide ferromagnets. In this conference, two results will be shown. One is the results of the analyses on 80 actinide ferromagnets and the other is the pressure dependence of the spin fluctuation parameters in UGe$$_2$$.

Journal Articles

Electronic structure of URu$$_2$$Si$$_2$$ studied by photoelectron spectroscopy (INVITED)

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

Progress in Nuclear Science and Technology (Internet), 5, p.82 - 85, 2018/11

Journal Articles

Magnetization study on the Ising ferromagnet URhGe with high-precision angle-resolved magnetic field near the hard axis

Nakamura, Shota*; Sakakibara, Toshiro*; Shimizu, Yusei*; Kittaka, Shunichiro*; Kono, Yohei*; Haga, Yoshinori; Pospisil, J.; Yamamoto, Etsuji

Progress in Nuclear Science and Technology (Internet), 5, p.123 - 127, 2018/11

Journal Articles

Anomalous Hall effect in a triangular-lattice antiferromagnet UNi$$_4$$B

Oyamada, Akira*; Inohara, Takao*; Yamamoto, Etsuji; Haga, Yoshinori

Progress in Nuclear Science and Technology (Internet), 5, p.128 - 131, 2018/11

Journal Articles

Soft X-ray magnetic circular dichroism study on UGe$$_{2}$$

Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Yamagami, Hiroshi; Yamamoto, Etsuji; Haga, Yoshinori

Progress in Nuclear Science and Technology (Internet), 5, p.171 - 174, 2018/11

Journal Articles

Magnetic field induced phenomena in UIrGe in fields applied along the $$b$$ axis

Posp$'i$$v{s}$il, J.*; Haga, Yoshinori; Kohama, Yoshimitsu*; Miyake, Atsushi*; Kambe, Shinsaku; Tateiwa, Naoyuki; Vali$v{s}$ka, M.*; Proschek, P.*; Prokle$v{s}$ka, J.*; Sechovsk$'y$, V.*; et al.

Physical Review B, 98(1), p.014430_1 - 014430_7, 2018/07

 Times Cited Count:9 Percentile:25.72(Materials Science, Multidisciplinary)

Journal Articles

Element-specific observation of the ferromagnetic ordering process in UCoAl via soft X-ray magnetic circular dichroism

Takeda, Yukiharu; Saito, Yuji; Okane, Tetsuo; Yamagami, Hiroshi; Matsuda, Tatsuma*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika*

Physical Review B, 97(18), p.184414_1 - 184414_7, 2018/05

AA2018-0316.pdf:0.62MB

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

Journal Articles

Anisotropic magnetic fluctuations in ferromagnetic superconductor UGe$$_2$$; $$^{73}$$Ge-NQR study at ambient pressure

Noma, Yuichiro*; Kotegawa, Hisashi*; Kubo, Tetsuro*; To, Hideki*; Harima, Hisatomo*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*; Ito, Kohei*; Haller, E. E.*; et al.

Journal of the Physical Society of Japan, 87(3), p.033704_1 - 033704_5, 2018/03

 Times Cited Count:3 Percentile:47.83(Physics, Multidisciplinary)

Journal Articles

Crystallographic, magnetic, thermal, and electric transport properties in UPtIn single crystal

Matsumoto, Yuji*; Haga, Yoshinori; Tateiwa, Naoyuki; Yamamoto, Etsuji; Fisk, Z.*

Journal of the Physical Society of Japan, 87(2), p.024706_1 - 024706_4, 2018/02

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Critical behavior of magnetization in URhAl; Quasi-two-dimensional Ising system with long-range interactions

Tateiwa, Naoyuki; Pospisil, J.*; Haga, Yoshinori; Yamamoto, Etsuji

Physical Review B, 97(6), p.064423_1 - 064423_10, 2018/02

 Times Cited Count:3 Percentile:73.51(Materials Science, Multidisciplinary)

The critical behavior of dc magnetization in the uranium ferromagnet URhAl with the hexagonal ZrNiAl-type crystal structure has been studied around the ferromagnetic transition temperature $$T_{rm C}$$. The critical exponent $$beta$$ for the temperature dependence of the spontaneous magnetization below $$T_{rm C}$$, $$gamma$$ for the magnetic susceptibility, and $$delta$$ for the magnetic isotherm at $$T_{rm C}$$ have been obtained. We have determined the critical exponents as $$beta$$ = 0.287 $$pm$$ 0.005, $$gamma$$ = 1.47 $$pm$$ 0.02, and $$delta$$ = 6.08 $$pm$$ 0.04 by the scaling analysis and the critical isotherm analysis. These critical exponents satisfy the Widom scaling law $${delta}{,}={,}1+{,}{gamma}/{beta}$$. The determined exponents can be explained with the results of the renormalization group approach for a two-dimensional Ising system coupled with long-range interactions.

Journal Articles

ScPd$$_2$$Al$$_3$$; New polymorphic phase in Al-Pd-Sc system

Pospisil, J.; Haga, Yoshinori; Nakajima, Kunihisa; Ishikawa, Norito; C$'i$sa$v{r}$ov$'a$, I.*; Tateiwa, Naoyuki; Yamamoto, Etsuji; Yamamura, Tomoo*

Solid State Communications, 268, p.12 - 14, 2017/12

 Times Cited Count:0 Percentile:100(Physics, Condensed Matter)

452 (Records 1-20 displayed on this page)