Site-diluted antiferromagnet in a uniform field

We study a site-diluted Ising antiferromagnet in a square lattice, in an external uniform field (DAFF). We use a real space renormalization group technique to obtain the phase diagram as a function of temperature (T), concentration of magnetic ions (p) and magnetic field (H). At zero temperature the phase diagram, in the H × T plane, has a steplike structure separating the disordered from the ordered antiferromagnetic phase. We also discuss the connection between this problem and that of a ferromagnet in a random field.