39K NMR study of phase transitions and electronic properties in K3C60

Alloul, H.; Holczer, K.; Yoshinari, Y.; Klein, O.

doi:10.1016/0921-4534(94)92475-9

Cited by 22 publications

(31 citation statements)

References 4 publications

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“…Albeit that all Na 2 AC 60 materials display the T-TЈ splitting, in the following we restrict our detailed NMR investigations to Na 2 CsC 60 because of the absence of the complicating polymer phase and because the narrower lines allow a better resolution. 23 Na NMR spectra of Na 2 AC 60 compounds in 7.5 T magnetic field at two temperatures, 400 K ͑spectra on the left͒ and 80 K ͑spectra on the right͒. ͑a͒ and ͑b͒ Na 2 CsC 60 ; ͑c͒ and ͑d͒ Na 2 KC 60 ; ͑e͒ and ͑f͒ Na 2 RbC 60 .…”

Section: Resultsmentioning

confidence: 99%

“…In these experiments the ␣ nuclei were the T, and the TЈ nuclei were the ␤ nuclei, and vice versa. 31 Since both the ␣ and ␤ nuclei are 23 Na and the splitting in frequency is small, it was difficult to achieve good selective excitation of the two lines. For such an excitation we used low-amplitude radio-frequency pulses with typical /2 length of 150 s. The interpulse delay was 5 ms, much longer than the / 2 length.…”

Section: Resultsmentioning

confidence: 99%

“…In this section we show that all our NMR results are compatible with this picture. 23 Na spectrum. For a quantitative analysis of the influence of fullerene rotational dynamics on the 23 Na spectrum we have performed a line shape simulation.…”

Section: Sodium Site Exchange Due To Reorientations Of Neighboring C mentioning

confidence: 99%

See 2 more Smart Citations

Influence of local fullerene orientation on the electronic properties ofNa2AC60(A=
Matus
¹
,
Alloul
²
,
Kriza
³

et al. 2006
Phys. Rev. B
11
2
14
1
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We have investigated sodium containing fullerene superconductors Na 2 AC 60 , A = Cs, Rb, and K, by 23 Na nuclear magnetic resonance ͑NMR͒ spectroscopy at 7.5 T in the temperature range of 10 to 400 K. Despite the structural differences from the Rb 3 C 60 class of fullerene superconductors, in these compounds the NMR line of the tetrahedrally coordinated alkali nuclei also splits into two lines ͑T and TЈ͒ at low temperature. In Na 2 CsC 60 the splitting occurs at 170 K; in the quenched cubic phase of Na 2 RbC 60 and Na 2 KC 60 we observe split lines at 80 K. By detailed investigations of the spectrum, spin-spin, and spin-lattice relaxations as well as spin-echo double resonance in Na 2 CsC 60 we show that these two different tetrahedral sites are mixed on a microscopic scale. The T and TЈ sites differ in the orientation of first-neighbor C 60 molecules. We present evidence that the orientations of neighboring molecules are uncorrelated. Thermally activated molecular reorientations cause an exchange between the T and TЈ sites and motional narrowing at high temperature. We infer the same activation energy 3300 K in the temperature range 125 to 300 K. The spin-lattice relaxation rate is the same for T and TЈ down to 125 K but different below. Both the spin-lattice relaxation rate and Knight shift are strongly temperature dependent in the whole range investigated. We interpret this temperature variation by the effect of phonon excitations involving the rigid librational motion of the C 60 molecules. By extending the understanding of the structure and molecular dynamics of C 60 superconductors, these results may help in clarifying the effects of the structure on the superconducting properties.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Influence of local fullerene orientation on the electronic properties ofNa2AC60(A=
Matus
¹
,
Alloul
²
,
Kriza
³

et al. 2006
Phys. Rev. B
11
2
14
1
View full text Add to dashboard Cite

show abstract

“…The science of fullerenes continues to be an exciting field, generating many articles with promising new applications every year. A search of the literature reveals that a lot of work has been carried out on synthesis, characterization of fullerenes, and doped fullerenes with alkali metals like potassium and rubidium ternary compounds, [4,5] poly fulleride ions in A C 60 [6] (A is potassium, rubidium, or cesium), and fullerene doped with organic cations like morpholine and acridizine [7]. The literature survey also reveals that 13 C NMR spectroscopic studies of fullerene and poly-ethylene oxide complexes, [8] magnetic resonance of solid fullerene and their compounds with alkali metals [9], superconductivity and nuclear magnetic resonance investigation of KTl 1.5 doped C 60 [10] have been carried out in past years.…”

Section: Introductionmentioning

confidence: 99%

<sup>13</sup>C NMR and Raman Studies of Fullerene-Based Poly (Acrylamides)

Porwal¹,

Diwedi²,

Kamal³

2012

IJOC

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A new classification of the different types of fullerene-containing polymers is presented according to their different properties and applications they exhibit in a variety of fields.13 C NMR and Raman studies of a series of polymeric samples of fullerene-grafted poly (acrylamide), which were prepared by systematic variation of concentration of fullerene and acrylamide, are described.13 C NMR spectral analysis of the polymeric samples showed a peak for fullerene at 143 δppm and for poly (acrylamide) between 170 and 180 δppm and Raman spectral analysis of the polymeric samples gave the Raman band for fullerene between 1470 cm −1 and poly (acrylamide) at 2800 cm. The Tg value, obtained from DSC results, showed a high glass transition temperature at 100.94˚C revealing the presence of fullerene in the polymeric matrix. TGA analysis shows that polymer is thermally stable up to 340˚C.

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“…We have performed 39 K-NMR measurements on the sample used for the 13 C NMR, 16 to study the influence of the slowing down of the rotational motion and of the phase transition on the alkali sites. Figure 5 shows the 39 K FT spectra taken from the FID signal.…”

Section: K Nmrmentioning

confidence: 99%

Molecular motion and phase transition inK3C60and
Yoshinari
¹
,
Alloul
²
,
Brouet
³

et al. 1996
Phys. Rev. B
Self Cite
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0
13
0
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Nuclear magnetic resonance ͑NMR͒ has been performed to study the molecular dynamics of the C 60 molecule in K 3 C 60 and Rb 3 C 60 . It is shown that the hypothesis of a uniaxial rotational motion around an axis fixed in the crystal can satisfactorily explain the observed 13 C NMR results. A resonance line is detected in the 39 K and 87 Rb NMR spectra below a temperature T* of 200 and 380 K in K 3 C 60 and Rb 3 C 60 , respectively. In particular, this T* in K 3 C 60 coincides with the temperature at which we observed a phase transition. This provides some clue about the origin of the phase transition. The discrepancy between the observed and calculated 13 C line shapes at low temperature suggests that the freezing of the molecular motion and a structural change at the phase transition induce a significant modification of the electron density on the C 60 molecule and likely on the conduction band electronic state. ͓S0163-1829͑96͒06734-3͔

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39K NMR study of phase transitions and electronic properties in K3C60

Cited by 22 publications

References 4 publications

Influence of local fullerene orientation on the electronic properties ofNa2AC60(A=
Matus
¹
,
Alloul
²
,
Kriza
³

et al. 2006
Phys. Rev. B
11
2
14
1
View full text Add to dashboard Cite

Influence of local fullerene orientation on the electronic properties ofNa2AC60(A=
Matus
¹
,
Alloul
²
,
Kriza
³

et al. 2006
Phys. Rev. B
11
2
14
1
View full text Add to dashboard Cite

<sup>13</sup>C NMR and Raman Studies of Fullerene-Based Poly (Acrylamides)

Molecular motion and phase transition inK3C60and
Yoshinari
¹
,
Alloul
²
,
Brouet
³

et al. 1996
Phys. Rev. B
Self Cite
25
0
13
0
View full text Add to dashboard Cite

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39K NMR study of phase transitions and electronic properties in K3C60

Cited by 22 publications

References 4 publications

Influence of local fullerene orientation on the electronic properties ofNa2AC60(A=Matus1, Alloul2, Kriza3 et al. 2006Phys. Rev. B112141View full textAdd to dashboardCite

Influence of local fullerene orientation on the electronic properties ofNa2AC60(A=Matus1, Alloul2, Kriza3 et al. 2006Phys. Rev. B112141View full textAdd to dashboardCite

&lt;sup&gt;13&lt;/sup&gt;C NMR and Raman Studies of Fullerene-Based Poly (Acrylamides)

Molecular motion and phase transition inK3C60andYoshinari1, Alloul2, Brouet3 et al. 1996Phys. Rev. BSelf Cite250130View full textAdd to dashboardCite

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Influence of local fullerene orientation on the electronic properties ofNa2AC60(A=
Matus
¹
,
Alloul
²
,
Kriza
³

et al. 2006
Phys. Rev. B
11
2
14
1
View full text Add to dashboard Cite

Influence of local fullerene orientation on the electronic properties ofNa2AC60(A=
Matus
¹
,
Alloul
²
,
Kriza
³

et al. 2006
Phys. Rev. B
11
2
14
1
View full text Add to dashboard Cite

<sup>13</sup>C NMR and Raman Studies of Fullerene-Based Poly (Acrylamides)

Molecular motion and phase transition inK3C60and
Yoshinari
¹
,
Alloul
²
,
Brouet
³

et al. 1996
Phys. Rev. B
Self Cite
25
0
13
0
View full text Add to dashboard Cite