A thermopower study of the SDW state of quasi one-dimensional conductor (TMTSF)2AsF6

The thermoelectric power of (TMTSF)(2)AsF6 was measured along the a-axis. A thermal hysteresis was found in the SDW state. Effects of magnetic fields were investigated for the field direction parallel to the a-, b'- and c-axes, where b' is defined as being perpendicular to both the a- and c*-axes. There was no magnetic hysteresis nor magnetic field influence on the thermal hysteresis up to 11.3 T. Suggestion is made about random pinning of SDW or structural changes accompanying SDW transition or both being the origin of this phenomenon. The thermopower displays a dramatic change of behaviour at T-1 = 2 K showing a possible subphase of SDW below T-1. Magnetic field reveals two different stales in the region 2-12 K divided by T-2 = 4.5 K with different temperature dependence of the thermopower. This suggests the presence of another two subphases of SDW. (C) 1998 Elsevier Science Ltd. All rights reserved.