  The meteoritical record shows both iron partitioning and tungsten isotopic
partitioning between matrix and chondrules. Tungsten is not abundant enough to
have driven its own isotopic partitioning, but if tungsten were correlated with
iron, then ferromagnetic interactions grains could help explain both
observations. We derive a practical parameterization for the increase in
particle-particle collision rates caused by mutually attracting particle
magnetic dipole moments. While the appropriate magnetic parameters remain
uncertain, we show that ambient magnetic fields in protoplanetary disks are
expected to be strong enough to magnetize iron metal bearing dust grains
sufficiently to drive large increases in their collision rates. Such increased
collision rates between iron metal rich grains could help preserve primordial
iron and W isotopic inhomogeneities; and would help explain why the
meteoritical record shows their partitioning in the solar nebula. The
importance of magnetic interactions for larger grains whose growth is balanced
by fragmentation is less clear, and will require future laboratory or numerical
studies.
