  The spin configuration induced by single holes and hole pairs doped into
stoichiometric, antiferromagnetic cuprates is considered. Unrestricted
Hartree-Fock calculations for the three-band Hubbard model are employed to
study spin-polaron and vortex-like (meron) solutions. Meron solutions for a
single hole are found to be metastable with higher energy than spin polarons.
We observe that the meron solution shifts from site-centered to bond-centered
as the interaction is increased. Meron-antimeron solutions for hole pairs are
found to be unstable. The results are in agreement with earlier findings for
the one-band Hubbard model. However, we find that the Hubbard interaction of
the one-band model has to be chosen similar to the one of the three-band model
to obtain comparable results, not of the order of the charge-transfer gap, as
previously expected.
