High Field Studies for BEDT-TTF Molecule Based Organic Conductors(Transport and Fermiology)

Recent progress in our studies for high-field magnetotransport properties in a quasi two-dimensional organic superconductor κ-(BEDT-TTF)_2Cu(NCS)_2 and an antiferromagnetic metal α-(BEDT-TTF)_2KHg(SCN)_4 is reviewed. The magnetic breakdown effect is observed above 20T in the former salt. The energy gap can be estimated to be (54±10)K by the wave form simulation of the Shubnikov-de Haas oscillations. The temperature and field dependence of the Hall coefficient are discussed on the basis of the Fermi surface topology. The magnetic phase diagram of α-(BEDT-TTF)_2KHg(SCN)_4 is obtained from the anomalous behavior of the magnetoresistance. The magnetoresistance, the magnetization, the Fermi surface and the splitting wave form of the magnetic quantum oscillations are presented