  The competition between the magnetic and charge orderings in a model cuprate
is considered in terms of a simplified static 2D spin-pseudospin model. This
model is equivalent to the 2D dilute antiferromagnetic (AFM) Ising model with
charged impurities. The mean-field approximation results are presented for the
system under study and briefly compared to the classical Monte Carlo (MC)
calculations. The numerical simulation shows that the cases of the strong
exchange and the strong charge correlation differ qualitatively. In the case of
a strong exchange, the AMF phase is instable with respect to the phase
separation (PS) into the pseudospin (charge) and magnetic (spin) subsystems
that behave as immiscible quantum liquids. The analytical expression has been
obtained for the PS temperature.
