  We prove a spontaneous magnetization of the oxygen-terminated ZnO (0001)
surface by utilizing a multi-code, SIESTA and KKR, first-principles approach,
involving both LSDA+U and selfinteraction corrections (SIC) to treat electron
correlation effects. Critical temperatures are estimated from Monte Carlo
simulations, showing that at and above 300 K the surface is thermodynamically
stable and ferromagnetic. The observed half-metallicity and long-range magnetic
order originate from the presence of p-holes in the valence band of the oxide.
The mechanism is universal in ionic oxides and points to a new route for the
design of ferromagnetic low dimensional systems.
