Underlayer-induced readback signal modulation in double-layer perpendicular media

The effects of sputtering double-layer CoCr/Permalloy flexible disks using an in-line magnetron sputtering system which simulates a possible configuration for high volume production of this media were investigated. It was found that angle-of-incidence effects due to the in-line nature of the process and the magnetic field from the magnetron sputtering cathode can both result in an anisotropic Permalloy underlayer. Modifying the angles-of-incidence of the sputtered atoms was found to be one way of controlling the anisotropy and signal modulation. Dependence of the read-back signal on the anisotropic permeability and thickness of the underlayer is reported.