  We present an analysis of the X-ray spectra of a sample of 37 observations of
26 Seyfert galaxies observed by XMM-Newton in order to characterize their iron
K emission. All objects show evidence for iron line emission in the 6-7 keV
band. A narrow core at 6.4 keV is seen almost universally in the spectra, and
we model this using a neutral Compton reflection component, assumed to be
associated with distant, optically thick material such as the molecular torus.
Once this, and absorption by a zone of ionized gas in the line-of-sight is
accounted for, less than half of the sample observations show an acceptable
fit. Approximately 2/3 of the sample shows evidence for further, broadened
emission in the iron K-band. When modeled with a Gaussian, the inferred energy
is close to that expected for neutral iron, with a slight redshift, with an
average velocity width of ~0.1c. The mean parameters are consistent with
previous ASCA results and support the idea that the broad components can be
associated with the accretion disk. Before proceeding to that conclusion, we
test an alternative model comprising a blend of 3-4 narrow, unshifted emission
lines (including the 6.4 keV core), together with 1-2 zones of highly ionized
gas in the line-of-sight. Around 1/3 of the objects are not adequately fit by
this model, and in general better fits are obtained with a relativistic disk
line model, which has fewer free parameters. Nonetheless we find that
absorption by ionized gas affects the spectrum above 2.5 keV in approximately
half the sample. There is evidence for multiple ionized zones in at least 3
objects, but in all those cases a blurred reflector is required in addition to
the complex absorption. (truncated)
