  A theory of magnetic impurities in a 2D electron gas quantized by a strong
magnetic field is formulated in terms of Friedel-Anderson theory of resonance
impurity scattering. It is shown that this scattering results in an appearance
of bound Landau states with zero angular moment between the Landau subbands.
The resonance scattering is spin selective, and it results in a strong spin
polarization of Landau states, as well as in a noticeable magnetic field
dependence of the $g$ factor and the crystal field splitting of the impurity
$d$ levels.
