An improved system for concentrating magnetic flux of a multi-pole magnetic structure at the surface of a ferromagnetic target uses pole pieces having a magnet-to-pole piece interface with a first area and a pole piece-to-target interface with a second area substantially smaller than the first area, where the target can be a ferromagnetic material or a complementary pole pieces. The multi-pole magnetic structure can be a coded magnetic structure or an alternating polarity structure comprising two polarity directions, or can be a hybrid structure comprising more than two polarity directions. A magnetic structure can be made up of discrete magnets or can be a printed magnetic structure.