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Journal Articles

Ferromagnetism and giant magnetoresistance in the rare-earth fullerides Eu$$_{6-x}$$Sr$$_x$$C$$_{60}$$

Ishii, Kenji; Fujiwara, Akihiko*; Suematsu, Hiroyoshi*; Kubozono, Yoshihiro*

Physical Review B, 65(13), p.134431_1 - 134431_6, 2002/03

 Times Cited Count:32 Percentile:79.32(Materials Science, Multidisciplinary)

We have studied crystal structure, magnetism and electric transport properties of a europium fulleride Eu$$_6$$C$$_{60}$$ and its Sr-substituted compounds, Eu$$_{6-x}$$Sr$$_x$$C$$_{60}$$. They have a $$bcc$$ structure, which is an isostructure of other $$M_6$$C$$_{60}$$ ($$M$$ represents an alkali atom or an alkaline earth atom). Magnetic measurements revealed that magnetic moment is ascribed to the divalent europium atom with $$S$$ = 7/2 spin, and a ferromagnetic transition was observed at $$T_C$$ = 10 - 14 K. In Eu$$_6$$C$$_{60}$$, we also confirm the ferromagnetic transition by heat capacity measurement. The striking feature in Eu$$_{6-x}$$Sr$$_x$$C$$_{60}$$ is very large negative magnetoresistance at low temperature; the resistivity ratio $$rho$$($$H$$ = 9 T)/$$rho$$($$H$$ = 0 T) reaches almost 10$$^{-3}$$ at 1 K in Eu$$_6$$C$$_{60}$$. Such large magnetoresistance is the manifestation of a strong $$pi$$-$$f$$ interaction between conduction carriers on C$$_{60}$$ and 4$$f$$ electrons of Eu.

Journal Articles

EXAFS study on local structural changes in amorphous Fe-Zr-B alloys

Nakata, Yoshiyuki*; Hara, Naoyuki*; Hirotsu, Yoshihiko*; Emura, Shuichi*; Makino, Akihiro*; Uruga, Tomoya*; Harada, Makoto*; Nishihata, Yasuo; Yoneda, Yasuhiro; Kubozono, Yoshihiro*

Japanese Journal of Applied Physics, 38(Suppl.38-1), p.404 - 407, 1999/06

The EXAFS spectra on Zr K-edge are investigated for as-formed Fe-7at%Zr-3at%B amorphous alloys and annealed ones at 693 K and 773 K for an hour in order to reveal local structural changes due to annealing. The analysis shows that the atomic distances of Fe-Zr and Zr-Zr pairs increase during annealing and approach those in a Fe3Zr or/and Fe2Zr metallic comound. The change in the atomic distances suggests that medium range ordered clusters should be formed during annealing.

Journal Articles

The XAFS beamline BL01B1 at SPring-8

Uruga, Tomoya*; Tanida, Hajime*; Yoneda, Yasuhiro; Takeshita, Kunikazu*; Emura, Shuichi*; Takahashi, Masao*; Harada, Makoto*; Nishihata, Yasuo; Kubozono, Yoshihiro*; Tanaka, Tsunehiro*; et al.

Journal of Synchrotron Radiation, 6(Part3), p.143 - 145, 1999/05

An x-ray absorption fine-structure (XAFS) spectroscopy beamline, BL01B1, was installed at a bending magnet source at SPring-8 and has been open to users since October 1997. It was designed for XAFS experiments covering a wide energy range. Position tables and automatical control programs were established to adjust the x-ray optics and achieve the designed performance of the beamline under each experimental condition. This has enabled conventional XAFS measurements to be made with a good data quality from 4.5 to 110 keV.

Journal Articles

XAFS study on RbC$$_{60}$$

Kubozono, Yoshihiro*; Mimura, Kazue*; Takabayashi, Yasuhiro*; Maeda, Hironobu*; Kashino, Setsuo*; Emura, Shuichi*; Nishihata, Yasuo; Uruga, Tomoya*; Tanaka, Tsunehiro*; Takahashi, Masao*

Journal of Synchrotron Radiation, 6(Part3), p.564 - 566, 1999/05

The Rb K-edge XAFS spectra for the stable phase of RbC60 which is a quasi one-dimensional polymer were measured in the temperature range from 14.6 to 210 K in order to clarify the origin of the metal-insulator transition around 50 K. The distances and mean-square relative displacements between the Rb atom and the neighboring C atoms determined by XAFS exhibited no change around 50 K, implying that the metal-insulator transition originates from the SDW instablity.

Journal Articles

Eu ${it K}$-XAFS of europium dioxymonocyanamide with the convension He$$^+$$ ion yield method

Takahashi, Masao*; Harada, Makoto*; Watanabe, Iwao*; Uruga, Tomoya*; Tanida, Hajime*; Yoneda, Yasuhiro; Emura, Shuichi*; Tanaka, Tsunehiro*; Kimura, Hidekazu*; Kubozono, Yoshihiro*; et al.

Journal of Synchrotron Radiation, 6(3), p.222 - 224, 1999/05

 Times Cited Count:10 Percentile:59.73(Instruments & Instrumentation)

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