Abstract
We report a microscopic investigation of the superconducting clathrates Ag6O8AgX (X = NO3 and HF2), which are composed of Ag6O8 polyhedral cages and a guest molecule X inside the cages. Site-selective NMR measurements have revealed that the trigonal planar NO3 molecule in Ag6O 8AgNO3 is confined in the (001) plane in a low-temperature tetragonal phase, while the uniaxial HF2 molecule in Ag 6O8AgHF2 is preferentially directed along the c-axis in a lowtemperature phase. These results point to the fact that the distortion of the cages takes place so as to minimize the entropy of the molecular motions of the guest ions inside the cages as the cage volume contracts thermally upon cooling. Note that the difference in Tc between these compounds may be primarily ascribed to a difference in their Debye frequencies, but neither to anharmonic vibrations of the guest molecules called rattling nor to other possible remaining degrees of freedom in the molecular dynamics.
| Original language | English |
|---|---|
| Article number | 074706 |
| Journal | Journal of the Physical Society of Japan |
| Volume | 80 |
| Issue number | 7 |
| DOIs | |
| Publication status | Published - Jul 2011 |
| Externally published | Yes |
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Keywords
- AgOAgX
- NMR
- Silver oxide clathrate
- Structural transition
- Superconductivity
ASJC Scopus subject areas
- Physics and Astronomy(all)
Cite this
Guest molecular dynamics in superconducting clathrates Ag6O 8AgX (X = NO3 and HF2) : NMR investigation. / Kanetake, Fumiya; Naruwa, Hirofumi; Mukuday, Hidekazu; Kitaoka, Yoshio; Kawashima, Kenji; Ishii, Masaru; Akimitsu, Jun.
In: Journal of the Physical Society of Japan, Vol. 80, No. 7, 074706, 07.2011.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Guest molecular dynamics in superconducting clathrates Ag6O 8AgX (X = NO3 and HF2)
T2 - NMR investigation
AU - Kanetake, Fumiya
AU - Naruwa, Hirofumi
AU - Mukuday, Hidekazu
AU - Kitaoka, Yoshio
AU - Kawashima, Kenji
AU - Ishii, Masaru
AU - Akimitsu, Jun
PY - 2011/7
Y1 - 2011/7
N2 - We report a microscopic investigation of the superconducting clathrates Ag6O8AgX (X = NO3 and HF2), which are composed of Ag6O8 polyhedral cages and a guest molecule X inside the cages. Site-selective NMR measurements have revealed that the trigonal planar NO3 molecule in Ag6O 8AgNO3 is confined in the (001) plane in a low-temperature tetragonal phase, while the uniaxial HF2 molecule in Ag 6O8AgHF2 is preferentially directed along the c-axis in a lowtemperature phase. These results point to the fact that the distortion of the cages takes place so as to minimize the entropy of the molecular motions of the guest ions inside the cages as the cage volume contracts thermally upon cooling. Note that the difference in Tc between these compounds may be primarily ascribed to a difference in their Debye frequencies, but neither to anharmonic vibrations of the guest molecules called rattling nor to other possible remaining degrees of freedom in the molecular dynamics.
AB - We report a microscopic investigation of the superconducting clathrates Ag6O8AgX (X = NO3 and HF2), which are composed of Ag6O8 polyhedral cages and a guest molecule X inside the cages. Site-selective NMR measurements have revealed that the trigonal planar NO3 molecule in Ag6O 8AgNO3 is confined in the (001) plane in a low-temperature tetragonal phase, while the uniaxial HF2 molecule in Ag 6O8AgHF2 is preferentially directed along the c-axis in a lowtemperature phase. These results point to the fact that the distortion of the cages takes place so as to minimize the entropy of the molecular motions of the guest ions inside the cages as the cage volume contracts thermally upon cooling. Note that the difference in Tc between these compounds may be primarily ascribed to a difference in their Debye frequencies, but neither to anharmonic vibrations of the guest molecules called rattling nor to other possible remaining degrees of freedom in the molecular dynamics.
KW - AgOAgX
KW - NMR
KW - Silver oxide clathrate
KW - Structural transition
KW - Superconductivity
UR - http://www.scopus.com/inward/record.url?scp=79960394798&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79960394798&partnerID=8YFLogxK
U2 - 10.1143/JPSJ.80.074706
DO - 10.1143/JPSJ.80.074706
M3 - Article
AN - SCOPUS:79960394798
VL - 80
JO - Journal of the Physical Society of Japan
JF - Journal of the Physical Society of Japan
SN - 0031-9015
IS - 7
M1 - 074706
ER -