Synthesis, Structure, and Transport Properties of Novel Fullerides A<sub>3</sub>C<sub>70</sub> (A = Ba and Sm)

Chen, X. H.; H., D.; Sun, Zijun; Takenobu, Taishi; Liu, and Z. S.; Iwasa, Yoshihiro

doi:10.1021/ja993881m

Cited by 14 publications

(8 citation statements)

References 24 publications

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“…Eu 3 - δ C 70 displays an antiferromagnetic interaction at high temperature and shows a magnetic transition below 5 K accompanied by the appearance of a small spontaneous moment. It is isostructural with Sm 2.78 C 70 , adopting a pseudo-monoclinic structure derived by deformation of the well-known fcc A 3 C 60 fulleride structures . In Sm 2.78 C 70 , there are C 70 dimers bridged by Sm ions .…”

Section: Introductionmentioning

confidence: 96%

Synthesis, Structure, and Magnetic Properties of the Fullerene-Based Ferromagnets Eu₃C₇₀ and Eu₉C₇₀

Takenobu

Margadonna

et al. 2003

J. Am. Chem. Soc.

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Intercalation of C(70) with europium affords two kinds of magnetic compounds, a canted antiferromagnet Eu(x)C(70) (x approximately 3) and a ferromagnet Eu(x)C(70) (x approximately 9) with transition temperatures (T(C)) of 5 and 38 K, respectively. The Curie constants in the paramagnetic phase and the saturation moment in the ferromagnetic phase are both understood by the full moment of Eu(2+) for both systems. The structure of Eu(3)(-)(delta)C(70) (delta approximately 0.27) is pseudo-monoclinic, derived by a simple deformation of the parent face-centered cubic (fcc) structure. Eu(9)(-)(delta)C(70) (delta approximately 0.2) forms an fcc structure, in which cuboctahedral clustering of Eu(2+) ions is observed in the enhanced size octahedral holes. The observed T(C) of the Eu(9)(-)(delta)C(70) ferromagnet is comparable to or larger than those of simple binary Eu-based ferromagnets, such as Eu chalcogenides or carbides, despite the low atomic ratio of Eu in the chemical formulas. This can be understood by the short Eu(2+)-Eu(2+) distances and high coordination numbers permitted by the multiple occupation by Eu(2+) ions of the expanded octahedral interstitial sites in higher fullerene-based solids.

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Section: Introductionmentioning

confidence: 96%

Synthesis, Structure, and Magnetic Properties of the Fullerene-Based Ferromagnets Eu₃C₇₀ and Eu₉C₇₀

Takenobu

Margadonna

et al. 2003

J. Am. Chem. Soc.

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“…[3][4][5] The gap between the highest occupied molecular orbital ͑HOMO͒ and the lowest unoccupied molecular orbital ͑LUMO͒ is reduced 3,5 and, in addition, the coupling between vibrational and electronic states is weaker. [6][7][8][9] Therefore, no evidence of superconductivity has been reported so far for C 70 salts. Metallic behavior is, in principle, expected for A 1 C 70 and A 4 C 70 salts ͑where A indicates an alkali metal͒ owing to the half filling of the LUMO derived bands in these intercalated C 70 compounds.…”

Section: Introductionmentioning

confidence: 99%

C 70 adsorbed on Cu(111): Metallic character and molecular orientation

Goldoni¹,

Cepek

Larciprete

et al. 2002

The Journal of Chemical Physics

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In situ x-ray photoelectron spectroscopic and density-functional studies of Si atoms adsorbed on a C 60 filmWe investigated the interaction of C 70 with the Cu͑111͒ surface using x-ray photoelectron spectroscopy and x-ray absorption spectroscopy. The data point to a net charge transfer from the Cu substrate to the C 70 molecules directly bonded to the Cu atoms, providing a metallic character for a single layer of C 70 ͑monolayer͒ adsorbed on this surface. A strong dependence of the x-ray absorption spectra from the light polarization is also observed. By comparing these experimental data with density-functional calculations of the contribution to the x-ray absorption spectral line shape of the five inequivalent carbon atoms in the C 70 cage, we observed that the molecules are mainly oriented with the C 5 V axis perpendicular to the Cu surface.

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“…9 Sm 3 C 70 is an fcc C 70 6phase. 10 Given the observation of superconductivity in C 70 field-effect transistors 11 at a doping level of four electrons per molecule, corresponding to a half-filled (LUMO + 1) band, the synthesis of nonsuperconducting C 70 3-salts would indicate the strong connection between the half-filled band and superconductivity in fulleride systems.…”

Section: Introductionmentioning

confidence: 99%

Close-Packed C₇₀^3- Phases − Synthesis, Structure, and Electronic Properties

et al. 2002

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The high symmetry and resulting electronic degeneracy of the C(60)(3)(-) anion is viewed as the key molecular feature in the high superconducting transition temperatures of fulleride and oxidized fullerene systems. The experimental evaluation of this hypothesis requires the synthesis of face-centered cubic (fcc) trivalent fulleride anion salts derived from higher fullerenes such as C(70), which have thus far proved elusive with only stable A(1)C(70), A(4)C(70), and A(6)C(70) phases known. In this paper, we report the synthesis of fcc A(3)C(70) phases stabilized by size-matching the tetrahedral site with the sodium cation. The structures are strongly dependent on the cooling protocol due to the existence of metastable partially or completely orientationally disordered phases. EPR data indicate that the phases are metallic but not superconducting. The densities of states at the Fermi level appear too low to give superconductivity at above 5 K, consistent with recent observations that four electrons per C(70) anion are required for superconductivity. Size-matching on both the octahedral and tetrahedral sites is required for A(3)C(70) stability - K(2)CsC(70) is only stable at elevated temperature and Na(2)C(70) is unstable, the composition corresponding to C(70) and a sodium-rich trigonal phase.

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Synthesis, Structure, and Transport Properties of Novel Fullerides A₃C₇₀ (A = Ba and Sm)

Cited by 14 publications

References 24 publications

Synthesis, Structure, and Magnetic Properties of the Fullerene-Based Ferromagnets Eu₃C₇₀ and Eu₉C₇₀

Synthesis, Structure, and Magnetic Properties of the Fullerene-Based Ferromagnets Eu₃C₇₀ and Eu₉C₇₀

C 70 adsorbed on Cu(111): Metallic character and molecular orientation

Close-Packed C₇₀^3- Phases − Synthesis, Structure, and Electronic Properties

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Synthesis, Structure, and Transport Properties of Novel Fullerides A3C70 (A = Ba and Sm)

Cited by 14 publications

References 24 publications

Synthesis, Structure, and Magnetic Properties of the Fullerene-Based Ferromagnets Eu3C70 and Eu9C70

Synthesis, Structure, and Magnetic Properties of the Fullerene-Based Ferromagnets Eu3C70 and Eu9C70

C 70 adsorbed on Cu(111): Metallic character and molecular orientation

Close-Packed C703- Phases − Synthesis, Structure, and Electronic Properties

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Synthesis, Structure, and Transport Properties of Novel Fullerides A₃C₇₀ (A = Ba and Sm)

Synthesis, Structure, and Magnetic Properties of the Fullerene-Based Ferromagnets Eu₃C₇₀ and Eu₉C₇₀

Synthesis, Structure, and Magnetic Properties of the Fullerene-Based Ferromagnets Eu₃C₇₀ and Eu₉C₇₀

Close-Packed C₇₀^3- Phases − Synthesis, Structure, and Electronic Properties