HIGH-FIELD PHASE-TRANSITIONS AND FERMI SURFACES IN THE ORGANIC CONDUCTOR ALPHA-(BEDT-TTF)(2)KHG(SCN)(4) - INFLUENCE OF THE MAGNETIC BREAKDOWN ON EVALUATION OF THE EFFECTIVE-MASS AND THE SCATTERING TIME

The change of the de Haas-van Alphen (dHvA) oscillation between the lo w-field spin-density-wave (SDW) phase and the high-held (N greater tha n or equal to 23 T) metallic phase of the organic conductor alpha-(BED T-TTF)(2)KHg(SCN)(4) is explained in terms of a model of the magnetic breakdown (MB) and a reconstructed Fermi surface by SDW. On the recons tructed Fermi surface, the scattering time obtained by fitting the sta ndard Lifshitz-Kosevich formulation to the dHvA oscillations is affect ed by the MB giving the additional field-dependent effect. Furthermore , the evaluation of the effective mass needs to consider the additiona l temperature-dependent factor being due to the MB gap which may chang e intrinsically and/or thermally with temperature. (C) 1998 Elsevier S cience B.V. All rights reserved.