  Atmospheric parameters (Teff, log g and log(He/H)) are derived for 42 hot
horizontal branch (HB) stars in the globular cluster NGC 6752. For 19 stars
MgII and FeII lines are detected indicating an iron enrichment by a factor 50
on average with respect to the cluster abundance whereas the magnesium
abundances are consistent with the cluster metallicity. This finding adds to
the growing evidence that radiative levitation plays a significant role in
determining the physical parameters of blue HB stars. Indeed, we find that iron
enrichment can explain part, but not all, of the problem of anomalously low
gravities along the blue HB. Thus the physical parameters of horizontal branch
stars hotter than about 11,500K in NGC 6752, as derived in this paper, are best
explained by a combination of helium mixing and radiative levitation effects.
