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Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

https://doi.org/10.1038/s41550-020-01271-2
 Times Cited Count：43 Percentile：96.93(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

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

https://doi.org/10.1103/PhysRevB.100.064413
 Times Cited Count：1 Percentile：4.76(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

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

https://doi.org/10.1126/science.aav7432
 Times Cited Count：259 Percentile：99.73(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

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

https://doi.org/10.1103/PhysRevB.99.094417
 Times Cited Count：6 Percentile：32.87(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

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

https://doi.org/10.1103/PhysRevLett.121.237001
 Times Cited Count：8 Percentile：54.37(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

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

https://doi.org/10.15669/pnst.5.104

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

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

https://doi.org/10.1103/PhysRevB.98.014430
 Times Cited Count：16 Percentile：61.77(Materials Science, 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

https://doi.org/10.7566/JPSJ.87.024706
 Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)

Journal Articles

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

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

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

https://doi.org/10.1103/PhysRevB.97.064423
 Times Cited Count：11 Percentile：49.2(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

https://doi.org/10.1016/j.ssc.2017.09.001
 Times Cited Count：0 Percentile：0(Physics, Condensed Matter)

Journal Articles

Electronic structure of ThRu$$_2$$Si$$_2$$ studied by angle-resolved photoelectron spectroscopy; Elucidating the contribution of U 5$$f$$ states in URu$$_{2}$$Si$$_{2}$$

Fujimori, Shinichi; Kobata, Masaaki; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Matsumoto, Yuji*; Yamamoto, Etsuji; Tateiwa, Naoyuki; et al.

Physical Review B, 96(12), p.125117_1 - 125117_9, 2017/09

https://doi.org/10.1103/PhysRevB.96.125117
 Times Cited Count：10 Percentile：45.87(Materials Science, Multidisciplinary)

Journal Articles

Itinerant ferromagnetism in actinide $$5f$$-electron systems; Phenomenological analysis with spin fluctuation theory

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

Physical Review B, 96(3), p.035125_1 - 035125_15, 2017/07

https://doi.org/10.1103/PhysRevB.96.035125
 Times Cited Count：24 Percentile：72.72(Materials Science, Multidisciplinary)

We have carried out an analysis of magnetic data in 69 uranium, 7 neptunium and 4 plutonium ferromagnets with the spin fluctuation theory developed by Takahashi (Y. Takahashi, J. Phys. Soc. Jpn. ${bf 55}$, 3553 (1986)). The basic and spin fluctuation parameters of the actinide ferromagnets are determined and the applicability of the spin fluctuation theory to actinide $$5f$$ system has been discussed. Itinerant ferromagnets of the $$3d$$ transition metals and their intermetallics follow a generalized Rhodes-Wohlfarth relation $${p_{rm eff}}/{p_{rm s}}{,}{propto}{,}({T_{rm C}}/{T_0})^{-3/2}$$. Here, $$p_{rm s}$$, $$p_{rm eff}$$, $$T_{rm C}$$, and $$T_0$$ are the spontaneous and effective magnetic moments, the Curie temperature and the width of spin fluctuation spectrum in energy space, respectively. The same relation is satisfied for $${T_{rm C}}/{T_0}< 1.0$$ in the most of the actinide ferromagnets.

Journal Articles

Magnetoresistance and Hall effect of antiferromagnetic uranium compound URhIn$$_5$$

Haga, Yoshinori; Matsumoto, Yuji*; Pospisil, J.; Tateiwa, Naoyuki; Yamamoto, Etsuji; Yamamura, Tomoo*; Fisk, Z.*

Journal of Physics; Conference Series, 807(1), p.012015_1 - 012015_4, 2017/04

https://doi.org/10.1088/1742-6596/807/1/012015
 Times Cited Count：1 Percentile：34.26(Physics, Condensed Matter)

Journal Articles

Effect of pressure on magnetism of UIrGe

Pospisil, J.; Gochi, Jun*; Haga, Yoshinori; Honda, Fuminori*; Uwatoko, Yoshiya*; Tateiwa, Naoyuki; Kambe, Shinsaku; Nagasaki, Shoko*; Homma, Yoshiya*; Yamamoto, Etsuji

Journal of the Physical Society of Japan, 86(4), p.044709_1 - 044709_6, 2017/04

https://doi.org/10.7566/JPSJ.86.044709
 Times Cited Count：9 Percentile：56.98(Physics, Multidisciplinary)

Journal Articles

Switching of magnetic ground states across the UIr$$_{1-x}$$Rh$$_x$$Ge alloy system

Pospisil, J.; Haga, Yoshinori; Kambe, Shinsaku; Tokunaga, Yo; Tateiwa, Naoyuki; Aoki, Dai*; Honda, Fuminori*; Nakamura, Ai*; Homma, Yoshiya*; Yamamoto, Etsuji; et al.

Physical Review B, 95(15), p.155138_1 - 155138_15, 2017/04

https://doi.org/10.1103/PhysRevB.95.155138
 Times Cited Count：14 Percentile：56.08(Materials Science, Multidisciplinary)

Journal Articles

Fermi surface of ThRu$$_{2}$$Si$$_{2}$$ as a reference to the strongly correlated isostructural metals investigated by quantum oscillations

Matsumoto, Yuji*; Haga, Yoshinori; Tateiwa, Naoyuki; Aoki, Haruyoshi*; Kimura, Noriaki*; Yamamura, Tomoo*; Yamamoto, Etsuji; Matsuda, Tatsuma*; Fisk, Z.*; Yamagami, Hiroshi*

Journal of the Physical Society of Japan, 85(10), p.104709_1 - 104709_7, 2016/10

https://doi.org/10.7566/JPSJ.85.104709
 Times Cited Count：2 Percentile：20.23(Physics, Multidisciplinary)

Journal Articles

Properties and collapse of the ferromagnetism in UCo$$_{1-x}$$Ru$$_{x}$$Al studied in single crystals

Pospisil, J.; Opletal, P.*; Vali$v{s}$ka, M.*; Tokunaga, Yo; Stunault, A.*; Haga, Yoshinori; Tateiwa, Naoyuki; Gillon, B.*; Honda, Fuminori*; Yamamura, Tomoo*; et al.

Journal of the Physical Society of Japan, 85(3), p.034710_1 - 034710_10, 2016/03

https://doi.org/10.7566/JPSJ.85.034710
 Times Cited Count：9 Percentile：55.48(Physics, Multidisciplinary)

Journal Articles

Enhancement of the cyclotron effective mass in U$$_{0.03}$$Th$$_{0.97}$$Ru$$_2$$Si$$_2$$

Haga, Yoshinori; Matsumoto, Yuji*; Tateiwa, Naoyuki; Yamamoto, Etsuji; Kimura, Noriaki*; Yamamura, Tomoo*; Fisk, Z.

Journal of Physics; Conference Series, 592(1), p.012036_1 - 012036_5, 2015/03

https://doi.org/10.1088/1742-6596/592/1/012036
 Times Cited Count：2 Percentile：60.99(Physics, Atomic, Molecular & Chemical)

Journal Articles

Single crystal growth and characterization of URu$$_2$$Si$$_2$$

Haga, Yoshinori; Matsuda, Tatsuma*; Tateiwa, Naoyuki; Yamamoto, Etsuji; Onuki, Yoshichika; Fisk, Z.

Philosophical Magazine, 94(32-33), p.3672 - 3680, 2014/11

https://doi.org/10.1080/14786435.2014.974711
 Times Cited Count：5 Percentile：27.24(Materials Science, Multidisciplinary)

Journal Articles

Electronic states in antiferromagnetic compound URhIn$$_5$$ investigated by de Haas-van Alphen effect and high pressure resistivity measurements

Matsumoto, Yuji; Haga, Yoshinori; Tateiwa, Naoyuki; Yamamoto, Etsuji; Kimura, Noriaki*; Aoki, Haruyoshi*; Fisk, Z.

JPS Conference Proceedings (Internet), 3, p.011097_1 - 011097_5, 2014/06

163 (Records 1-20 displayed on this page)