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Journal Articles

Pressure-induced weak ferromagnetism in uranium dioxide, UO$$_{2}$$

Sakai, Hironori; Kato, Harukazu; Tokunaga, Yo; Kambe, Shinsaku; Walstedt, R. E.; Nakamura, Akio; Tateiwa, Naoyuki*; Kobayashi, Tatsuo*

Journal of Physics; Condensed Matter, 15(28), p.S2035 - S2037, 2003/07

 Times Cited Count:3 Percentile:21.31(Physics, Condensed Matter)

The cubic-fluorite type uranium dioxide UO$$_2$$ is an ionically bounded insulator with localized magnetic moments of U$$^{4+}$$ (5$$f^{2}$$) ions. Under atmospheric pressure, UO$$_2$$ exhibits a first order antiferromagnetic transition at $$T_{rm N}$$=30.8 K accompanied by a small lattice distortion. In order to clarify the interrelation between QQ and exchange interactions in this system, we performed d.c. magnetization measurement under high pressure up to about 1 GPa by a piston-cylinder-type cramped cell. From the d.c. magnetization measurements under high pressure ($$ge$$ 0.1 GPa), it is found that UO$$_2$$ shows a weak-ferromagnetic-like transition at $$sim$$ 30 K, where the transition temperature is almost independent of external pressure up to 1 GPa. The ferromagnetic component per uranium atom is very small ($$sim 0.05 mu_{rm B}$$), although its component is dependent of pressure. This small ferromagnetic component may come from a canted antiferromagnetic ordering.

Journal Articles

Ga nuclear magnetic resonance study of UTGa$$_{5}$$(T=Ni, Pt)

Kato, Harukazu; Sakai, Hironori; Tokunaga, Yo; Tokiwa, Yoshifumi; Ikeda, Shugo; Onuki, Yoshichika; Kambe, Shinsaku; Walstedt, R. E.

Journal of Physics; Condensed Matter, 15(28), p.S2001 - S2005, 2003/07

 Times Cited Count:4 Percentile:26.91(Physics, Condensed Matter)

UPtGa$$_{5}$$ and UNiGa$$_{5}$$ are 5$$f$$-itinerant antiferromagnets with N$'{e}$el temperature $$T_{N}$$ = 26 K (Pt), 86 K (Ni). Remarkably, although the two compounds show almost identical Fermi surface properties in the paramagnetic state, recent neutron scattering experiments reveal that UPtGa$$_{5}$$ and UNiGa$$_{5}$$ are quite different in magnetic structure below $$T_{N}$$. In the microscopic viewpoint, we have carried out $$^{69,71}$$Ga NMR/NQR measurements for the both coumpounds. We have suceeded in separating the temperature independent term and the Curie-like-temperature-dependent term of the Knight shift $$K$$. This should be a good starting point in considering the magnetism of this system.

Journal Articles

Photoemission spectroscopy of the filled skutterudite compound YbFe$$_{4}$$Sb$$_{12}$$

Okane, Tetsuo; Fujimori, Shinichi; Mamiya, Kazutoshi; Okamoto, Jun; Muramatsu, Yasuji; Fujimori, Atsushi; Nagamoto, Yasuyuki*; Koyanagi, Tsuyoshi*

Journal of Physics; Condensed Matter, 15(28), p.S2197 - S2200, 2003/07

 Times Cited Count:5 Percentile:31.4(Physics, Condensed Matter)

The filled skutterudite compounds $$RT_{4}X_{9}$$ ($$R$$ = alkaline earth, rare earth, actinide; $$T$$ = Fe, Ru, Os; $$X$$ = pnictogen: P, As, Sb) exhibit a variety of physical properties such as superconductivity, magnetic ordering, heavy-Fermion behavior, and metal-insulator transition. Among them, YbFe$$_{4}$$Sb$$_{12}$$ shows a heavy-Fermion or intermediate-valence behavior in the magnetic, electrical transport, and thermal properties, which might be associated with a valence instability of Yb atom. In this study, the electronic structure of YbFe$$_{4}$$Sb$$_{12}$$ have been investigated by the high-resolution photoemission spectroscopy, using He discharge lamp and synchrotron radiation as an excitation sources. The bulk and surface components of the Yb$$^{2+}$$ signal is clearly divided in the spectra. The relation of the energy position between them is anomalous compared to that of the conventional mixed-valent Yb compounds.

Journal Articles

Electrical resistivity of single-crystal URhGe$$_2$$ under high pressure

Matsuda, Tatsuma; Ikeda, Shugo; Haga, Yoshinori; Yamamoto, Etsuji; Hedo, Masato*; Uwatoko, Yoshiya*; Onuki, Yoshichika

Journal of Physics; Condensed Matter, 15(28), p.S2019 - S2021, 2003/07

 Times Cited Count:1 Percentile:8.53(Physics, Condensed Matter)

We have done the pressure experiment of a ferromagnet URhGe$$_2$$ with the orthorhombic crystal structure by measuring the electrical resistivity. Two ferromagnetic ordering temperatures $$T_{rm C2}$$=30 K and $$T_{rm C2}$$=25 K indicate a different pressure dependence. $$T_{rm C2}$$ is approximately unchanged, 30 K at ambient pressure and 40 K at 6-8 GPa, while $$T_{rm C1}$$ decreases with increasing pressure and most likely becomes zero at 8 GPa. URhGe$$_2$$ is found to be ferromagnetic even at 8 GPa, and then the $$A$$ and $$rho_0$$ values of the electrical resistivity $$rho=rho_0 + AT^2$$ are unchanged against pressure.

Journal Articles

Crystal and magnetic structure in the itinerant 5$$f$$ antiferromagnet UCr$$_2$$Si$$_2$$

Matsuda, Tatsuma; Metoki, Naoto; Haga, Yoshinori; Ikeda, Shugo; Kaneko, Koji; Yamamoto, Etsuji; Onuki, Yoshichika

Journal of Physics; Condensed Matter, 15(28), p.S2023 - S2027, 2003/07

 Times Cited Count:4 Percentile:26.91(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Magnetic properties of U$$_2$$RhGa$$_8$$ and U$$_2$$FeGa$$_8$$

Ikeda, Shugo; Okubo, Tomoyuki*; Inada, Yoshihiko*; Tokiwa, Yoshifumi; Kaneko, Koji; Matsuda, Tatsuma; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika

Journal of Physics; Condensed Matter, 15(28), p.S2015 - S2018, 2003/07

 Times Cited Count:6 Percentile:35.59(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Magneic order of UGa$$_{3}$$ investigated by means of neutron scattering under uniaxial pressure

Nakamura, Mitsutaka; Matsuda, Tatsuma; Kakurai, Kazuhisa; Lander, G. H.; Kawarazaki, Shuzo*; Onuki, Yoshichika

Journal of Physics; Condensed Matter, 15(28), p.S1997 - S2000, 2003/07

 Times Cited Count:4 Percentile:26.91(Physics, Condensed Matter)

The uranium intermetallic compounds UX$$_{3}$$ demonstrate a wide variety of magnetic properties, which depends on the strength of hybridization effect between the 5$$f$$-electron state of U atom and the $$s$$-,$$p$$-,$$d$$-electronic states of X atom. However, there are many uncertainties in the origin of these phenomena. UX$$_{3}$$ systems crystallizes in high symmetric structure, that is cubic AuCu$$_{3}$$ type. Therefore, the neutron diffraction measurement usually gives no conclusive information on the orientation of the total magnetic moment for UX$$_{3}$$ compounds because of their multi-domain structures. In this study we have succeeded to induce the anisotropic domain structure by applying the uniaxial pressure and prove the total magnetic moment of UGa$$_{3}$$ to be along the [011] axis.

Journal Articles

Crystalline electric field excitations in CeAgSb$$_{2}$$

Araki, Shingo; Metoki, Naoto; Thamizhavel, A.*; Onuki, Yoshichika

Journal of Physics; Condensed Matter, 15(23), p.S2179 - S2182, 2003/07

no abstracts in English

Journal Articles

Higher-order collinear interaction and magnetic excitation in the 5f localized system U$$_{3}$$Pd$$_{20}$$Si$$_{6}$$

Metoki, Naoto; Koike, Yoshihiro; Haga, Yoshinori; Kaneko, Koji; Araki, Shingo; McEwen, K. A.*; Kogi, Masafumi*; Aso, Naofumi*; Lander, G. H.; Komatsubara, Takemi*; et al.

Journal of Physics; Condensed Matter, 15(28), p.S1957 - S1963, 2003/07

 Times Cited Count:2 Percentile:15.13(Physics, Condensed Matter)

no abstracts in English

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