  The linear stability of thin Keplerian discs of weakly ionized polytropic
plasma embedded in a mixed (toroidal-poloidal) axisymmetric magnetic field is
studied. The effects of the central body on the equilibrium state of the discs
are modeled by an axial total current and a dipole magnetic field. Studying the
amplification of high-frequency waves shows that Keplerian discs can be
destabilized due to combined effects of equilibrium density stratification and
poloidal magnetic field. By considering a boundary value problem in the limit
of strong Hall effect, it is shown that whistler waves which are free of direct
influence of compressibility, rotation and gravity, are amplified along their
trajectory while other modes of wave propagation do not change their amplitude.
