Two-dimensional Fermi surface for the organic conductor κ-(BETS)2FeBr4

Magnetoresistance measurements have been performed for the organic conductor kappa-(BETS)(2) FeBr4 to investigate the Fermi surface. Three fundamental Shubnikov-de Haas oscillations (alpha, beta and gamma) were observed. The cross-sectional areas corresponding to the cc and P oscillations are about 20% and 100% in the first Brillouin zone, respectively. The oscillations can be assigned to the closed orbit and the magnetic breakdown orbit. The effective masses of the conduction electrons are determined to be 5.2m(0), for alpha and 7.9m(0) for beta. The heavy masses are probably due to the antiferromagnetic fluctuation effect of the Fe spins. The origin of the oscillation gamma with very low frequency is not explained by the band calculation. (C) 2001 Elsevier Science B.V. All rights reserved.