  We study the ferromagnetism in the compound (Zn,Mn)O within the
Haldane-Anderson impurity model by using the quantum Monte Carlo technique and
the tight-binding approximation for determining the host band-structure and the
impurity-host hybridization. This computational approach allows us to determine
how the host crystal structure influences the impurity bound state, which plays
an important role in the development of the ferromagnetic (FM) correlations
between the impurities. We find that the FM correlations are strongly
influenced by the crystal structure. In particular, in p-type (Zn,Mn)O, we
observe the development of FM correlations with an extended range at low
temperatures for wurtzite and zincblende crystal structures. However, for the
rocksalt structure no FM correlations are observed between the impurities. In
addition, in n-type ZnO with magnetic impurities, the impurity bound state and
FM correlations are not found.
