Methods and apparatus for generating a magnetic field external to a physical vapor deposition (PVD) chamber to improve etch or deposition uniformity on a substrate disposed inside of the PVD chamber are provided herein. In some embodiments, a process chamber, includes a chamber body defining an interior volume therein; a pedestal disposed in the interior volume for supporting a substrate; a coil disposed in the interior volume above the pedestal; and an external magnet assembly, comprising: a housing coupled to the chamber body; and a plurality of magnets disposed external to the chamber body coupled to the housing and arranged asymmetrically about the chamber body.