Magnetic oscillations in a two - dimensional network of com - pensated electron and hole orbits

– The Fermi surface of the quasi-two dimensional (2D) organic metal (ET)8Hg4Cl12 (C6H5Br)2 can be regarded as a 2D network of compensated electron and hole orbits coupled by magnetic breakthrough. Simultaneous measurements of the interlayer magnetoresistance and magnetic torque have been performed for various directions of the magnetic field up to 28 T in the temperature range from 0.36 K to 4.2 K. Magnetoresistance and de Haas-van Alphen (dHvA) oscillations spectra exhibit frequency combinations typical of such a network. Even though some of the observed magnetoresistance oscillations cannot be interpreted on the basis of neither conventional Shubnikov-de Haas oscillations nor quantum interference, the temperature and magnetic field (both orientation and magnitude) dependence of all the Fourier components of the dHvA spectra can be consistently accounted for by the dHvA effect on the basis of the Lisfhitz-Kosevich formula. This behaviour is at variance with that currently reported for compounds illustrating the linear chain of coupled orbits model. Frequency combinations observed in magnetic oscillations spectra of multiband quasi twodimensional (2D) metals have been extensively studied both from theoretical and experimental viewpoints [1]. Nevertheless, the physical origin of some of the observed Fourier components, the so called ’forbidden frequencies’, remain still unclear. In addition to quantum interference (QI) that can be invoked in the case of magnetoresistance (MR) data, these frequencies can be attributed to both the oscillation of the chemical potential [2, 3] and the field-dependent magnetic breakthrough (MB)-induced Landau level broadening [4]. However, a quantitative model that involve these two latter contributions is still needed. The Fermi surface (FS) of most of the compounds exhibiting such frequencies corresponds to the linear chain of coupled orbits model. This model was introduced by Pippard in the early sixties in order to compute (∗) E-mail: [email protected]