HIGH-FIELD MAGNETORESISTANCE OF THE BECHGAARD SALT (TMTSF)(2)ASF6 - FAST OSCILLATIONS AND SPIN-DENSITY-WAVE TRANSITION

We report a detailed study of the transverse magnetoresistance of the Bechgaard salt (TMTSF)(2)AsF6, at ambient pressure, in fields up to 37 T, in the temperature range 1.8-30 K. Fast oscillations (FO's), alrea dy evidenced by our group two years ago, have been studied versus the tilt angle of B with respect to the least conducting (c,b') plane at 4.2 K. Only one series, having a fundamental frequency of 208 T for B parallel to c, has been observed in a temperature range which seems l imited to the spin-density-wave (SDW) state domain (T<11 K). As with o ther Bechgaard salts, the oscillation amplitude exhibits a low-tempera ture maximum located here around 3 K. We have also studied the behavio r of the mean magnetoresistance which exhibits, in addition to a local maximum near 3 K, a second one at the metal-SDW transition temperatur e T-SDW A shift of this later towards higher values has been observed when the field is increased. A comparison with other TMTSF salts exhib iting the FO phenomenon is presented.