MAGNETIC PHASE-DIAGRAM OF THE ORGANIC CONDUCTOR ALPHA-(BEDT-TTF)2KHG(SCN)4

The magnetic field-vs.-temperature phase diagram of the organic conductor-alpha-(BEDT-TTF)2KHg(SCN)4 is presented. There appears around T(A)=10K at H=0 a second-order phase transition from a normal metallic state to another metallic state associated with an antiferromagnetic-like magnetic order. When the magnetic fields are applied normal to the conducting plane, T(A) shifts to lower temperatures, and pes to zero at H(A)(T=0)=23T. The inside region of the phase boundary encompassed by T(A) and H(A) is divided into two states by H(B)(=7T around 1K); the reversible and irreversible states of both the magnetoresistance and magnetization for H<H(B)(T) and H>H(B)(T), respectively. The third characteristic field H(C)(T)(=10T at 1K) defined as the magnetic field where the magnetoresistance takes a maximum is located slightly above H(B)(T). Discussions are made on this phase diagram.