SLOW QUANTUM OSCILLATIONS IN THE SEMIMETALLIC SPIN-DENSITY-WAVE STATE OF TETRAMETHYLTETRASELENAFULVALINIUM NITRATE (TMTSF)(2)NO3

We have observed a clear series of fine structures superposed on the angular dependence of the transverse magnetoresistance in the semimetallic spin-density-wave state of the organic conductor (TMTSF)2NO3. They appear at the positions defined by the strength of the field component parallel to the least-conduction direction (B cos θconst). An observed asymmetry in the magnitude is due to the striking angular dependence of the oscillations amplitude. The frequency of the oscillations (BS=63 T) is close to the frequency of the field-induced spin-density-wave transitions found in the other Bechgaard salts. This oscillatory phenomenon is considered to result from the orbit quantization inside the closed parts of the Fermi surface which are due to the 2kF anion ordering together with the imperfect spin-density-wave nesting. © 1994 The American Physical Society.