Magnetic field dependence of the SDW phase in (TMTSF)2PF6 under pressure

The transverse magnetoresistance has been measured in (TMTSF)2PF6 under pressure, with the field parallel to the c∗ axis. At 0.85 GPa, the spin-density-wave (SDW) transition temperature TSDW increases quadratically with the applied magnetic field, and a saturation behavior is observed in high magnetic fields. These results are consistent with the mean field theory. From these behaviors, TSDW for the perfect nesting case, Fermi velocity and imperfect nesting parameter at 0.85 GPa are estimated as TSDW0=14.5 K, vF=8.55×104 m/s and ε0/Δ0=0.996 using the mean field theory, respectively. The SDW phase diagram of (TMTSF)2X can be described by taking into account the reduction of the coupling constant by the pressure.