A planar ferromagnetic sputter target is provided for use as cathode in the magnetron sputtering of magnetic thin films, wherein the ferromagnetic material has localized regions of differing magnetic permeability. A solid, unitary, planar sputter target is formed from a ferromagnetic material, such as cobalt, nickel, iron or an alloy thereof, and this planar target is subjected to mechanical deformation, heat treatment, and/or thermal-mechanical treatment to create regions within the sputter target having different permeability than adjacent regions. The permeability differences in the ferromagnetic sputter target guides the path of the magnetic flux flow through the target to thereby increase the magnetic leakage flux at the target sputtering surface.