Sputtering machines and substrate holders for such systems are described which include one or more magnets apart from the magnets typical of sputtering guns. The added magnets produce a magnetic field bias which is a new means for controlling depositional flux, ionization degree of a sputtered species, and microstructure properties of deposited coatings. An exemplary substrate holder may have a magnet or magnet array near or next to the surface supporting the substrate, and the magnet may assume multiple different magnetic field configurations depending on the desired properties of the resulting magnetic field bias within the reaction chamber.