  We study the competition between long-range and short-range interactions
among holes within the spin density wave picture of layered transition metal
oxides. We focus on the problem of charge ordering and the charge phase
diagram. We show that the main interactions are the long-range Coulomb
interaction and a dipolar short-range interaction generated by the short-range
antiferromagnetic fluctuations. We find four different phases depending on the
strength of the dipolar interaction and the density of holes: Wigner crystal,
diagonal stripes, horizontal-vertical stripes (loops) and a glassy-clumped
phase. We discuss the effect of temperature, disorder and lattice effects on
these phases.
