Structure and properties of a fullerideSm6C60

Abstract

A novel fulleride Sm 6 C 60 has been synthesized using high temperature solid state reaction. The Rietveld refinement on high resolution synchrotron Xray powder diffraction data shows that Sm 6 C 60 is isostructural with bodycentered cubic A 6 C 60 (A=K, Ba). Raman spectrum of Sm 6 C 60 is similar to that of Ba 6 C 60 , and the frequencies of two A g modes in Sm 6 C 60 are nearly the same as that of Ba 6 C 60 , suggesting that Sm is divalent and hybridization between C 60 molecules and the Sm atom could exist in Sm 6 C 60 . Resistivity measurement shows a weak T-linear behavior above 180 K, the transport at low temperature is mainly dominated by granular-metal theory.PACS numbers: 71.20. Tx, 67.57.Hi Alkali intercalation into the C 60 host lattice is a successful technique for synthesizing new fullerides.1 Hereafter, an extensive research has been concentrated on the intercalation of a wide variety of atoms or molecules in the C 60 solids. Intercalation of alkali metals in the C 60 solids yields various structural compounds A x C 60 (x=1, 3, 4, 6) with different physical property.2-6 Among these, the superconducting compounds, A 3 C 60 , has attracted considerable interest.3 In this system, the fcc lattice parameter and band filling are tunable by changing the intercalants, T c goes up with increasing lattice parameter, 7 while it rapidly decreases when the nominal valence ( n ) shifts from the half-filling n=3 of t 1u band. 8The study was then extended to the alkali-earth series of AE x C 60 , 9-12 the electrons are introduced by intercalation of alkali-earth metals into the next lowest unoccupied molecular orbital with t 1g symmetry. The superconducting compounds with various structures and critical temperatures were prepared (Ca 5 C 60 , Ba 4 C 60 , Sr 4 C 60 ).9,13 Such tolerance for the C 60 molecular valence in t 1g superconductors makes a striking contrast with the strict constraint for the valence state in the case of t 1u superconductors.The rare-earth metals were also intercalated into the C 60 solids, but only one phase RE 2.75 C 60 (RE=Yb, Sm) was discovered so far.14,15 In this system, the basic structure of 1

Ferromagnetism and giant magnetoresistance in the rare-earth fulleridesEu6−xSrxIshii1, Fujiwara2, Suematsu3 et al. 2002Phys. Rev. B271330View full textAdd to dashboardCite

“…The wavelength of x-ray is 0.8057Å for x = 0, 3, 5, and 0.8011Å for x = 6. They all can be understood by a bcc structure which is an isostructure of other M 6 C 60 in alkali 12 , alkaline earth 13 and rare earth (Sm) 14 fullerides. The Rietveld refinements based on the space group Im3 were performed with use of the RI-ETAN program 15,16 .…”

Toward a microscopic description of Kondo dimers on metallic surfaces

“…They have identified sharp resonances at the Fermi surface [1,6,7,8,9], characteristic of the Kondo effect, a paradigmatic quantum many-body state which originates from the screening of the impurity spin by the conduction electrons. Systematic experimental studies of more complex structures with two or more magnetic atoms have been recently initiated and strong magnetic exchange interactions between the impurities have been identified [2,3] and estimated [4,5]. Despite all these important experimental successes and the interest in more complex magnetic nanostructures, our present understanding is mainly phenomenological.…”

Pressure-induced structural phase transition in fullerides doped with rare-earth metals

“…The diffraction patterns at 1.5 GPa showed a two-phase behavior both in Sm 3 C 70 and Eu 3 C 70 . In this case, the twophase refinements converged smoothly, resulting in the two sets of lattice parameters aϭ14.610(5) Å, bϭ9.905(4) Å, cϭ10.734(5) Å, ␤ϭ96.078(7)°and aϭ14.504 (5)…”

“…Despite the peak broadening, the indexing process of the diffraction profiles at high pressure was successfully made on a monoclinic cell. The cell parameters extracted by the Le Bail fit at 1.8 GPa were aϭ14.467 (5)°for Sm 3 C 70 and Eu 3 C 70 , respectively. These cell parameters are very similar to those at ambient pressure, indicating that the highpressure structure is essentially similar to that at ambient pressure.…”