| Issue |
J. Phys. IV France
Volume 114, April 2004
|
|
|---|---|---|
| Page(s) | 57 - 60 | |
| DOI | https://doi.org/10.1051/jp4:2004114010 | |
J. Phys. IV France 114 (2004) 57
DOI: 10.1051/jp4:2004114010
Magnetic and optical studies of spin and charge ordering in (TMTTF) 2AsF 6
M. Dumm1, 1, B. Salameh1, M. Abaker1, L.K. Montgomery2 and M. Dressel11 Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany
2 Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
Abstract
We studied the magnetic and electronic properties of the
insulating charge-transfer salt (TMTTF)
2AsF
6 by electron spin
resonance (ESR), SQUID magnetometer and optical conductivity measurements.
For the first time, the lattice dynamics was investigated in the vicinity of
the charge order transition. We found a splitting of the
electron-molecular-vibration coupled totally symmetric intramolecular
a
mode below the charge-order transition at 100 K. From
this result a charge disproportionation on the TMTTF molecular stacks of
about 2:1 can be estimated. The spin degrees of freedom were investigated by
ESR and SQUID. At high temperatures (TMTTF)
2AsF
6 behaves like a
antiferromagnetic
S=1/2 Heisenberg chain. Below 13 K, we observed an
exponential decrease of the spin susceptibility indicating the phase
transition into the spin-Peierls ground state.
Key words. charge-transfer salts - charge order - spin order -
optical properties - magnetic properties.
© EDP Sciences 2004