J. Phys. IV France 09 (1999) Pr10-27-Pr10-31
Low-temperature thermodynamical properties of Bechgaard salts : (TMTSF)2PF6 versus (TMTSF)2AsF6K. Biljakovic1, 2, J.C. Lasjaunias2 and P. Monceau2
1 Institute of Physics, P.O. Box 304, 10001 Zagreb, Croatia
2 CRTBT-CNRS associé à l'UJF, BP. 166, 38042 Grenoble cedex 9, France
We report on specific heat measurements of (TMTSF)2AsF6 in the temperature range 75 mK to 7 K and compare them with the results obtained for (TMSF)2PF6. In addition to the generic features of density waves ( DW) heat capacities, there are similar discontinuities in the lattice contribution in both systems at 1.9 K and 3.5 K, which we ascribe to transitions between sub-SDW phases. The low-energy excitations (LEE) contribution, dominant at T<0.5K, is strongly reduced in the case of AsF6 as well as the time dependent effects in the specific heat. We discuss the origin of the hyperfine T2 term and give the arguments that it can only be provided by the metastable LEEs. Finally, we relate similarities, but also differences, of the specific properties of mixed CDW/SDW states which has been recently found in structural investigations of both compounds.
© EDP Sciences 1999