  We present an analysis of photometric, spectroscopic and spectropolarimetric
data of the nearby, cool, magnetic DZ white dwarf PM J08186-3110. High
dispersion spectra show the presence of Zeeman splitted spectral lines due to
the presence of a surface average magnetic field of 92 kG. The strong magnesium
and calcium lines show extended wings shaped by interactions with neutral
helium in a dense, cool helium-rich atmosphere. We found that the abundance of
heavy elements varied between spectra taken ten years apart but we could not
establish a time-scale for these variations; such variations may be linked to
surface abundance variations in the magnetized atmosphere. Finally, we show
that volume limited samples reveal that about 40% of DZ white dwarfs with
effective temperatures below 7000 K are magnetic.
