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Journal Articles

Synthesis, crystal structure and magnetic properties of Yb$$_{8}$$Ag$$_{18.5}$$Al$$_{47.5}$$, Yb$$_{2}$$Pd$$_{2}$$Cd and Yb$$_{1.35}$$Pd$$_2$$Cd$$_{0.65}$$

Dhar, S.*; Settai, Rikio*; Onuki, Yoshichika; Galatanu, A.*; Haga, Yoshinori; Manfrinetti, P.*; Pani, M.*

Journal of Magnetism and Magnetic Materials, 308(1), p.143 - 152, 2007/01

 Times Cited Count:14 Percentile:55.92(Materials Science, Multidisciplinary)

We report the synthesis of three new Yb-based compounds, Yb$$_8$$Ag$$_{18.5}$$Al$$_{47.5}$$, Yb$$_2$$Pd$$_2$$Cd and Yb$$_{1.35}$$Pd$$_2$$Cd$$_{0.65}$$. The crystal symmetry of these compounds has been determined and the complete structural characterisation carried out by single crystal and powder diffraction techniques. The 4f levels of the Yb ions are appreciably hybridised in Yb$$_8$$Ag$$_{18.5}$$Al$$_{47.5}$$ and to a lesser extent in Yb$$_2$$Pd$$_2$$Cd as inferred from the magnetisation and heat capacity data. Signatures of heavy fermion behaviour are observed in the heat capacity data of Yb$$_2$$Pd$$_2$$Cd in which the heat capacity, $$C/T$$, increases at low temperatures attaining a value of 600 mJ/molK$$^2$$ at 1.8 K. The electrical resistivity of Yb$$_2$$Pd$$_2$$Cd follows a linear variation with temperature, $$T$$, between 1.4 and 5K, thus indicating a possible non-Fermi liquid behaviour. In contrast, Yb ions are trivalent in Yb$$_{1.35}$$Pd$$_2$$Cd$$_{0.65}$$ and order magnetically near 1.4 K.

Journal Articles

Magnetic and Fermi surface properties in ferromagnets NdRh$$_3$$B$$_2$$ and GdRh$$_3$$B$$_2$$

Obiraki, Yoshiko*; Nakashima, Hiroshi*; Galatanu, A.*; Matsuda, Tatsuma; Haga, Yoshinori; Takeuchi, Tetsuya*; Sugiyama, Kiyohiro*; Kindo, Koichi*; Hagiwara, Masayuki*; Settai, Rikio*; et al.

Journal of the Physical Society of Japan, 75(6), p.064702_1 - 064702_8, 2006/06

 Times Cited Count:3 Percentile:27.5(Physics, Multidisciplinary)

We succeeded in growing single crystals of ferromagnets NdRh$$_3$$B$$_2$$ and GdRh$$_3$$B$$_2$$ with the hexagonal structure, and measured the electrical resistivity, specific heat, magnetic susceptibility and magnetization. From these measurements, the Curie temperature $$T_C$$ is determined as $$T_C$$=10.2 K in NdRh$$_3$$B$$_2$$ and TC=93 K in GdRh$$_3$$B$$_2$$. The magnetic moments of about 2.5 $$mu_B$$ in NdRh$$_3$$B$$_2$$ and 7.7 $$mu_B$$ in GdRh$$_3$$B$$_2$$ are oriented in the basal plane. The crystalline electric field scheme is proposed for NdRh$$_3$$B$$_2$$ on the basis of the experimental results of Schottky anomaly in the specific heat and anisotropic susceptibility and magnetization. The Fermi surface in NdRh$$_3$$B$$_2$$ is very similar to that in a non-4 f reference compound LaRh$$_3$$B$$_2$$, possessing the quasi-one dimensional electronic character.

Journal Articles

Crossover of the 5f electrons from itinerant to localized in UPtGa$$_5$$

Onuki, Yoshichika; Ikeda, Shugo; Yamagami, Hiroshi*; Galatanu, A.*; Haga, Yoshinori; Matsuda, Tatsuma; Yamamoto, Etsuji; Settai, Rikio*

Physica B; Condensed Matter, 378-380, p.972 - 973, 2006/05

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

no abstracts in English

Journal Articles

Magnetic behaviour of UB$$_4$$ at high temperatures

Galatanu, A.*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.999 - 1000, 2006/05

 Times Cited Count:4 Percentile:23.8(Physics, Condensed Matter)

UB$$_4$$ is a moderate heavy fermion compound which does not exhibit any magnetic order down to 0.3 K. In this work, the magnetic properties of UB$$_4$$ are investigated in an extended temperature range, 2-800 K, on high-quality single crystals. A cross-over from a low temperature 5f itinerant behaviour to a high temperature 5f localized behaviour is observed, marked by broad peaks in the magnetic susceptibility measured along the main crystallographic axes.

Journal Articles

Magnetic structure and crystal field excitation in heavy fermion superconductor CePt$$_{3}$$Si

Metoki, Naoto; Kaneko, Koji; Matsuda, Tatsuma; Galatanu, A.; Takeuchi, Tetsuya*; Hashimoto, Shin*; Ueda, Taiki*; Settai, Rikio*; Onuki, Yoshichika*; Bernhoeft, N.*

Physica B; Condensed Matter, 359-361, p.383 - 385, 2005/06

 Times Cited Count:1 Percentile:6.58(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Electrical and magnetic properties of a single crystal UCu$$_2$$Si$$_2$$

Matsuda, Tatsuma; Haga, Yoshinori; Ikeda, Shugo; Galatanu, A.; Yamamoto, Etsuji; Shishido, Hiroaki*; Yamada, Mineko*; Yamaura, Junichi*; Hedo, Masato*; Uwatoko, Yoshiya*; et al.

Journal of the Physical Society of Japan, 74(5), p.1552 - 1556, 2005/05

 Times Cited Count:21 Percentile:70.75(Physics, Multidisciplinary)

We have succeeded in growing a high-quality single crystal of UCu$$_2$$Si$$_2$$ with the tetragonal structure by the Sn-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. UCu$$_2$$Si$$_2$$ is found to order antiferromagnetically below $$T_{rm N}$$ = 106 K, and follows a successive ferromagnetic ordering at $$T_{rm C}$$ = 100 K. The magnetic properties are highly anisotropic, reflecting the crystal structure. An easy-axis of magnetization is found to be the [001] direction ($$c$$-axis) both in the antiferromagnetic and ferromagnetic phases, while the [100] direction ($$a$$-axis) corresponds to the hard-axis in magnetization. The magnetization curve in the antiferromagnetic phase indicates a clear metamagnetic transition at a low field of about 1 kOe and changes smoothly into a ferromagnetic magnetization curve below $$T_{rm C}$$ = 100 K. The saturation moment is determined as 1.75$$mu_{rm B}$$/U at 2 K. The electronic specific heat coefficient is also determined as 20 mJ/K$$^2$$$$cdot$$mol.

Journal Articles

High-temperature magnetic investigations on uranium compounds

Galatanu, A.; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yamamoto, Etsuji; Aoki, Dai*; Takeuchi, Tetsuya*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 74(5), p.1582 - 1597, 2005/05

 Times Cited Count:36 Percentile:80.41(Physics, Multidisciplinary)

We investigated the magnetic property of typical uranium compounds by measuring the magnetic susceptibility in an extended temperature range up to about 800 K. The magnetic susceptibility follows the Curie-Weiss law for a localized 5$$f^2$$-electron compound UPd$$_3$$ and a ferromagnetic insulator UFe$$_4$$P$$_{12}$$. In most of the investigated compounds we observed a crossover effect of the 5$$f$$ electrons from a low-temperature itinerant nature to a high-temperature localized one. This is found to be characteristic for ferromagnetic superconductors such as UGe$$_{2}$$ and UIr, and also for antiferromagnets like USb$$_{2}$$ or UNiSb$$_{2}$$. To assess an extension of this characteristic property in the uranium compounds we also investigated typical 5$$f$$-itinerant compounds like UGa$$_{3}$$ and UPtGa$$_5$$. The crossover effect is essentially important in heavy fermion compounds such as UPt$$_3$$, UPd$$_2$$Al$$_3$$ and URu$$_2$$Si$$_2$$. Even in the paramagnetic compound of UB$$_4$$, the magnetic susceptibility is not temperature-independent, but approaches a 5$$f$$-localized tendency at high temperatures. Since the samples were single crystals, we were also able to trace the evolution of the magnetic anisotropy. The high-temperature anisotropic susceptibility data were analyzed on the basis of the crystalline electric field scheme.

Journal Articles

Antiferromagnetic and ferromagnetic phases of UCu$$_2$$Si$$_2$$

Matsuda, Tatsuma; Haga, Yoshinori; Ikeda, Shugo; Galatanu, A.; Onuki, Yoshichika

Physica B; Condensed Matter, 359-361, p.1069 - 1071, 2005/04

 Times Cited Count:3 Percentile:17.86(Physics, Condensed Matter)

We have succeeded in growing a high-quality single crystal of UCu$$_2$$Si$$_2$$ with the tetragonal structure by the Sn-flux method and measured the magnetic susceptibility and magnetization. UCu$$_2$$Si$$_2$$ is confirmed to order antiferromagnetically below $$T_{rm N}$$ = 106 K, and follows a successive ferromagnetic ordering at $$T_{rm C}$$ = 100 K. The magnetic properties are highly anisotropic, reflecting the crystal structure. An easy-axis of magnetization is found to be the [001] direction ($$c$$-axis), while the [100] direction ($$a$$-axis) corresponds to the hard-axis in magnetization. The saturation moment is determined as 1.8$$mu_{rm B}$$/U.

Journal Articles

Single-crystal growth and magnetic properties of a new ternary uranium compound U$$_3$$Ni$$_5$$Al$$_{19}$$

Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Galatanu, A.; Matsumoto, Takuya*; Sugimoto, Toyonari*; Tada, Toshiji*; Noguchi, Satoru*; Onuki, Yoshichika

Physica B; Condensed Matter, 359-361, p.1006 - 1008, 2005/04

 Times Cited Count:2 Percentile:12.3(Physics, Condensed Matter)

A new ternary uranium-based intermetallic compound U$$_3$$Ni$$_5$$Al$$_{19}$$ has been symthesized. It crystallizes in the unique flat orthorhombic structure. Uranium atoms occupy two crystallographic 4$$c$$ and 8$$f$$ sites where local chemical environments are quite similar. The temperature dependence of the magnetic susceptibility $$chi(T)$$ demonstrates peculiar magnetic anisotropy; $$chi(T)$$ along $$b$$- and $$c$$-axes obeys the Curie-Weiss law above 23 K, while $$chi(T)$$ along $$a$$-axis is small and temperature independent. At 23 K, only $$chi_c$$ shows a sharp cusp corresponding to the antiferromagnetic ordering, while $$chi_b$$ remains paramagnetic behavior down to 2 K. These results and crystallographical considerations lead to a conclusion that only uranium atoms at the 8$$c$$ site order antiferromagnetically at $$T_{rm N}$$ = 23 K, while uranium atoms at the $$4c$$ site do not order down to 50 mK.

Journal Articles

Small saturation moment due to the crystalline electric field effect for $$T_h$$ site symmetry in the ferromagnet UFe$$_4$$P$$_{12}$$

Matsuda, Tatsuma; Galatanu, A.; Haga, Yoshinori; Ikeda, Shugo; Yamamoto, Etsuji; Hedo, Masato*; Uwatoko, Yoshiya*; Takeuchi, Tetsuya*; Sugiyama, Kiyohiro*; Kindo, Koichi*; et al.

Journal of the Physical Society of Japan, 73(9), p.2533 - 2538, 2004/09

 Times Cited Count:8 Percentile:49.43(Physics, Multidisciplinary)

Electrical resistivity, specific heat, magnetic susceptibility and high-field magnetization measurements have been performed on the ferromagnet UFe$$_{4}$$P$$_{12}$$ with the cubic crystal structure. The ferromagnetic ordering at $$T_{rm C}$$,=,3.1 K, a small saturation moment of 1.3 $$mu_{rm B}$$/U, together with the temperature dependence of the magnetic susceptibility, are found to be well explained by considering the 5$$f^2$$ crystalline electric field schemes for $$T_{h}$$ site symmetry and the magnetic exchange interaction.

Journal Articles

Single crystal growth and magnetic property of UNiSb$$_2$$

Ikeda, Shugo; Matsuda, Tatsuma; Galatanu, A.; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika

Journal of Magnetism and Magnetic Materials, 272-276(1), p.62 - 63, 2004/05

 Times Cited Count:6 Percentile:35.11(Materials Science, Multidisciplinary)

We have succeeded in growing a single crystal of an antiferromagnet UNiSb$$_2$$ by the self-flux method. The magnetic susceptibility is found to be highly anisotropic, reflecting the quasi-two dimensional tetragonal crystal structure. The magnetic easy-axis is determined as the [001] direction, consistent with the result of the neutron scattering experiments.

Journal Articles

Magnetic structure and the crystal field excitation in heavy-fermion antiferromagnetic superconductor CePt$$_{3}$$Si

Metoki, Naoto; Kaneko, Koji; Matsuda, Tatsuma; Galatanu, A.; Takeuchi, Tetsuya*; Hashimoto, Shin*; Ueda, Taiki*; Settai, Rikio*; Onuki, Yoshichika; Bernhoeft, N.*

Journal of Physics; Condensed Matter, 16(15), p.L207 - L212, 2004/04

 Times Cited Count:88 Percentile:93.78(Physics, Condensed Matter)

no abstracts in English

Journal Articles

High temperature magnetic properties of UIr single crystals

Galatanu, A.; Haga, Yoshinori; Yamamoto, Etsuji; Matsuda, Tatsuma; Ikeda, Shugo; Onuki, Yoshichika

Journal of the Physical Society of Japan, 73(3), p.766 - 767, 2004/03

 Times Cited Count:15 Percentile:64.02(Physics, Multidisciplinary)

High-temperature magnetic susceptibilities of ferromagnetic UIr have been measured up to 800 K. The small saturation moment 0.5 $$mu_{rm B}$$ as well as the large electronic specific heat coefficient suggest itinerant ferromagnetic characteristics of this compound. We have found that the paramagnetic effective moment approarches to the value expected for free uranium ion above room temperature. This result suggests that magnetic moments at high temperature behave like localized moments.

Journal Articles

Single crystal growth and magnetic properties of 5$$f$$-itinerant antiferromagnet UPdGa$$_5$$

Ikeda, Shugo; Metoki, Naoto; Haga, Yoshinori; Kaneko, Koji; Matsuda, Tatsuma; Onuki, Yoshichika; Galatanu, A.

Journal of the Physical Society of Japan, 72(10), p.2622 - 2626, 2003/10

 Times Cited Count:16 Percentile:66.91(Physics, Multidisciplinary)

A single crystal of uranium ternary intermetallic compound UPdGa$$_5$$ was grown by the Ga self-flux method. The magnetic susceptibility showed a weak temperature dependence and small anisotropy, consistent with an itinerant character of 5$$f$$ electrons. We observed a clear drop in the susceptibility and electrical resistivity below the N$'{e}$el temperature $$T_{rm N}$$= 31 K. The magnetic structure was studied by means of a neutron diffraction measurement. We observed an antiferromagnetic peak with the propagation vector $textbf{textit{Q}}$=[0,0,1/2]. The uranium 5$$f$$ moment of 0.33$$mu_{rm B}$$/U parallel to the $$c$$-axis was found to order ferromagnetically in the basal $$c$$-plan and coupled antiferromagnetically along the $$c$$-axis.

Journal Articles

Crystal structure, magnetic ordering, and magnetic excitation in the 4${it f}$-localized ferromagnet CeAgSb$$_{2}$$

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

Physical Review B, 68(2), p.024408_1 - 024408_9, 2003/07

 Times Cited Count:38 Percentile:82.16(Materials Science, Multidisciplinary)

no abstracts in English

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