  Realistic boundaries of finite heat conductivity Realistic boundaries of
finite heat conductivity for thermoconvection in a Rayleigh-B\'enard setup with
magnetized ferrofluids are investigated. A linear stability analysis of the
conductive state is performed with a shooting method. It shows that the
critical wave number is for any magnetic field stronly influenced by the
conductivity of the boundaries. Linear as well as nonlinear coefficients of a
Ginzburg Landau amplitude equation for convection shortly above the onset are
evaluated as functions of the magnetic Rayleigh number, the boundary
conductivities, and the fluid Prandtl number.
