Wave form of de Haas-van Alphen oscillations in a two-dimensional metal

The effect of thermodynamical equilibrium transfer of electrons between clo sed (Landau) orbits and magnetic field independent states near the Fermi su rface on the magnetoquantum oscillations in quasi-two-dimensional (2D) meta ls is investigated. The general relationship between magnetization and chem ical potential oscillations in such a model is derived, and a variety of wa ve forms rue obtained in the entire temperature-magnetic field region. It i s shown quite generally that such an electron transfer suppresses the chemi cal potential oscillations, whereas the magnetization amplitude remains unc hanged. A specific model of the relevant band structure in which the field independent (or reservoir) states correspond to quasiplanar energy surfaces is considered in detail. In this model, the chemical potential oscillation s diminish when the bottom of the subband with the quasiplanar energy surfa ces nearly coincides with the Fermi energy, and the corresponding one-dimen sional van Hove singularity dominates the electron transfer. Similarly, the chemical potential may be pinned due to electrons in localized state-a nea r the Fermi energy. In both cases the de Haas-van Alphen oscillations are s hown to have an inverse-sawtooth shape at sufficiently low temperatures. In the more common situation when the Fermi energy is relatively far from any sharp peak of the reservoir density of states, the wave form of the magnet ization oscillations is symmetrized at all temperatures. All shapes of magn etization oscillations observed in the organic quasi-2D metals of the (BEDT -TTF)(2)X type, from the rare sawtooth and inverse-sawtooth to the usual sy mmetrical ones, can be accounted for by this model.