Thin permalloy film - bulk ferrite composite head for perpendicular magnetic recording

A composite head of thin permalloy film and bulk ferrite has been developed for perpendicular magnetic recording, which is designed to operate from only one side of the recording medium. This head has been fabricated mostly by means of vacuum evaporation, sputtering and photo-lithography. The writing and reading efficiencies have been confirmed to be as good as for a ferrite ring type head, by using Co-Cr films with a soft magnetic layer of amorphous Co-Mo-Zr. Higher bit density is obtained by a thinner pole tip head, though there is a sacrifice of output at lower bit densities. The highest bit density, D50, of 57 kBPI has been attained with a pole tip thickness of 0.3 μm. Computer analysis shows that a decrease of output at lower bit densities with decreasing pole tip thickness is attributed to the magnetic saturation of the pole tip. It is thus concluded that in order to improve head performance, it is necessary to increase the saturation induction of the pole tip material.