A perpendicular magnetic write head in which unintended erasure of information at the time of non-writing can be suppressed while keeping the capability of writing is provided. The shielding assembly reduces process by-products from accumulating on the inner surfaces. A plasma torch passes through the cavity and is axially aligned with a magnetic field maximum of the applied microwave electromagnetic field. The feedback control of the roller surfaces provides a more uniform casting surface and a more consistent output from the casting surface.