Spin-density-wave transition of (formula presented) at high magnetic fields

The transverse magnetoresistance of the Bechgaard salt (formula presented) has been measured for various pressures, with the field up to 24 T parallel to the lowest-conductivity direction (formula presented) A quadratic behavior is observed in the magnetic-field dependence of the spin-density-wave (SDW) transition temperature (formula presented) With increasing pressure, (formula presented) decreases and the coefficient of the quadratic term increases. These results are consistent with the prediction of the mean-field theory based on the nesting of the quasi-one-dimensional Fermi surface. Using a mean-field theory, (formula presented) for the perfect nesting case is estimated as about 16 K. This means that even at ambient pressure where (formula presented) is 12 K, the SDW phase of (formula presented) is substantially suppressed by the two dimensionality of the system.