A plasma sputtering apparatus according to one embodiment includes a chamber and a reservoir in fluidic communication with the chamber. The reservoir stores a vapor source therein, and is configured to release vapor at a predetermined rate. The vapor released by the reservoir is effective to diminish an etch rate of a first magnetic material, the vapor having a smaller effect on an etch rate of a second magnetic material that is different than the first magnetic material. The apparatus also includes a mount for a substrate and a plasma source.