Thin-film processing electromagnet with modified core for producing low-skew magnetic orientation

An electromagnet having one or more coils wrapped around a plate-shaped core produces a uniaxial magnetic field in the vicinity of a substrate surface for orienting a magnetic film deposited onto the substrate surface. Variations in the magnetic mass of the plate-shaped core or in the magnetic permeability of the core mass are made to reduce angular skew and to improve uniformity of the uniaxial magnetic field. The variations generally involve a reduction in magnetic mass or permeability near a center of the core with respect to a periphery of the core. Cavities of various sizes and shapes but having symmetry with a magnetic axis can be formed in the core for this purpose.