J. Phys. IV France
Volume 114, April 2004
Page(s) 111 - 112

J. Phys. IV France
114 (2004) 111
DOI: 10.1051/jp4:2004114022

Anomalous thermal expansion behavior in (TMTTF) 2PF 6 and (TMTSF) 2PF 6 around 100 K: Indications for a strong spin-phonon interaction?

M. Lang1, J. Müller2, F. Steglich2, A. Brühl1, B. Wolf1 and M. Dressel3

1  Institute of Physics, J.W. Goethe-University Frankfurt, 60054 Frankfurt (M), Germany
2  Max-Planck-Institut for Chemical Physics of Solids, 01187 Dresden, Germany
3  Institute of Physics I, University of Stuttgart, 70550 Stuttgart, Germany

High-resolution measurements of the coefficient of thermal expansion along the b axis, $\alpha_{b}$, on the quasi-1D Spin-Peierls and spin-density-wave systems (TMTTF) 2PF 6 and (TMTSF) 2PF 6, respectively, reveal an anomalous $\alpha $(T) contribution around 100 K. This feature, which is most strongly pronounced in the SP system, is reminiscent of the magnetic contribution observed in low-dimensional spin systems with a strong spin-lattice interaction such as CuGeO 3. Remarkably enough, the position of the $\alpha_{b}$ anomalies for both compounds almost coincide with the temperatures where the thermal conductivity shows a distinct minimum [T. Lorenz et al., Nature 418 (2002) 614]. Our observation indicates a significant role of the spin-lattice interaction for these systems. Key words. Spin - phonon interaction, thermodynamic properties.

© EDP Sciences 2004