Magnetic field response of the spin density wave in α-(BEDT-TTF)2KHg(SCN)4

Magnetic phase diagram and metal - spin-density-wave (SDW) transition in an organic conductor α-(BEDT-TTF)2KHg(SCN)4 are revisited from a view point of magnetic torque measurements. The metal - SDW transition temperature determined by magnetic torque measurements shifts from about 8K at H = 0 T to higher temperatures with increasing magnetic field, and tends to be saturated. This transition line is different from that determined by the so-called kink structure of the magnetoresistance so far. Inside the SDW phase, an additional phase boundary exists at the temperature independent field of 23 T, where the effective mass and Dingle temperature determined by de Haas - van Alphen oscillations change their values.