J. Phys. IV France
Volume 114, April 2004
Page(s) 397 - 399

J. Phys. IV France
114 (2004) 397
DOI: 10.1051/jp4:2004114095

Charge disproportionate state of BEDT-TTF $\beta ''$ - salts

T. Yamamoto1, 1, M. Uruichi1, K. Yakushi1, Jun-Ichi Yamaura2, H. Tajima2 and A. Kawamoto3

1  Institute for Molecular Science, Myodaiji, 444-8585 Okazaki, Japan
2  Institute for Solid State Physics, Kashiwanoha, 277-8185 Kashiwa, Japan
3  Department of Physics, Hokkaido University, 060-0810 Sapporo, Japan

We studied C=C stretching bands of $\beta ''$-(ET) 3(ReO 4)2 and $\beta $-(ET) 4M(CN) 4H 2O (M=Pt, Pd and Ni) at the low temperatures below 300 K in order to verify the inhomogeneous charge distributions. A drastic spectral change was observed for $\beta ''$-(ET) 3(ReO 4)2 at 80 K, below which the system falls into the charge ordered state. On the other hand, a continuous spectral change was observed for $\beta ''$-(ET) 4Ni(CN) 4H 2O and $\beta ''$-(ET) 4Pd(CN) 4H 2O. $\nu $ 2 for M=Ni and Pd exhibited a doublet, suggesting an inhomogeneous charge distributions. $\nu $ 2 for M=Pt did not show a peak splitting, while C=C bands for the deuterium analogue exhibited a behaviour similar to those for M=Ni. Key words. Molecular conductors - organic conductors - ET salts - vibrational spectra - structural analyses - charge ordered state - mean-field calculations-isotope effect.

© EDP Sciences 2004