J. Phys. Soc. Jpn. 81 (2012) 023703 (4 pages) |Previous Article| |Next Article| |Table of Contents|
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Superconductivity in the Einstein Solid AxV2Al20 (A= Al and Ga)
Atsushi Onosaka,
Yoshihiko Okamoto,
Jun-ichi Yamaura, and
Zenji Hiroi
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
(Received November 6, 2011; Accepted November 28, 2011; Published January 5, 2012)
A cage compound of the form AxV2Al20 (Al10V), which was called an Einstein solid by Caplin and coworkers 40 years ago, is revisited to investigate the low-energy, local vibrations of the A atoms and their effects on the electronic and superconducting properties of the compound. Polycrystalline samples with A= Al, Ga, Y, and La are studied through resistivity and heat capacity measurements. Weak-coupling BCS superconductivity is observed below Tc = 1.49, 1.66, and 0.69 K for Ax= Al0.3, Ga0.2, and Y, respectively, but not above 0.4 K for Ax= La. Low-energy modes are detected only for A= Al and Ga, which are approximately described by the Einstein model with Einstein temperatures of 24 and 8 K, respectively. A weak but significant coupling between the low-energy modes, which are almost identical to those called rattling in a recent study, and conduction electrons manifests itself as anomalous enhancement in resistivity at low temperatures approximately corresponding to the Einstein temperatures.
©2012 The Physical Society of Japan
URL:
http://jpsj.ipap.jp/link?JPSJ/81/023703/
DOI: 10.1143/JPSJ.81.023703
- A. D. Caplin, G. Grüner, and J. B. Dunlop:
Phys. Rev. Lett. 30 (1973) 1138[APS].
- A. D. Caplin and L. K. Nicholson:
J. Phys. F 8 (1978) 51[IoP STACKS].
- G. J. Legg and P. C. Lanchester:
J. Phys. F 8 (1978) 2125[IoP STACKS].
- G. S. Nolas, J. L. Cohn, G. A. Slack, and S. B. Schujman:
Appl. Phys. Lett. 73 (1998) 178[AIP Scitation].
- V. Keppens, D. Mandrus, B. C. Sales, B. C. Chakoumakos, P. Dai, R. Coldea, M. B. Maple, D. A. Gajewski, E. J. Freeman, and S. Bennington:
Nature 395 (1998) 876[CrossRef].
- Y. Nagao, J. Yamaura, H. Ogusu, Y. Okamoto, and Z. Hiroi:
J. Phys. Soc. Jpn. 78 (2009) 064702[JPSJ].
- Z. Hiroi, S. Yonezawa, Y. Nagao, and J. Yamaura:
Phys. Rev. B 76 (2007) 014523[APS].
- Z. Hiroi, J. Yamaura, and K. Hattori: to be published in J. Phys. Soc. Jpn.
- O. N. Carlson, D. J. Kenney, and H. A. Wilhelm: Trans. Am. Soc. Met. 47 (1955) 520.
- R. P. Elliott: Constitution of Binary Alloys (McGraw-Hill, New York, 1965) First Supplement, p. 62.
- P. J. Brown: Acta Crystallogr. 10 (1957) 133.
- A. E. Ray and J. F. Smith: Acta Crystallogr. 10 (1957) 604.
- S. Niemann and W. Jeitschko:
J. Solid State Chem. 114 (1995) 337[CrossRef].
- T. Claeson and J. Ivarsson: Commun. Phys. 2 (1977) 53.
- J. H. J. M. Ribot, J. Bass, H. van Kempen, R. J. M. van Vucht, and P. Wyder:
Phys. Rev. B 23 (1981) 532[APS].