  The effects of Hubbard-type on-site interactions on the BHZ model is studied
in this paper for model parameters appropriate for the HgTe/CdTe quantum well.
Within a simple mean field theory we search for plausible magnetic
instabilities in the model and find that the ground state becomes {\em
ferromagnetic} when the interaction strength between electrons in hole orbital
is strong enough. The result can be understood by an approximate mapping of the
Hubbard-BHZ model to the one band Hubbard model. The same mapping suggests that
the magnetic and/or other ordered phases are more likely to occur in large gap
topological insulators whose occupations are close to 1/2 for both electron and
hole orbital.
