Topographically controlled anisotropy in sandwich video heads

The performance of sandwich heads for high-density video recording can be improved if the soft magnetic layer is given a special profile. This is achieved by sputter deposition of amorphous Co films on substrate tiles that have a grooved surface profile. On the basis of a consideration of the relevant energy terms the critical groove dimensions are estimated. The effect of surface topography on the relative permeability is verified from test structures on strips and ring-shaped substrates. Sandwich heads, manufactured with a groove pattern distributed radially around the coil chamber, perform 3-4 dB better than conventional heads. This demonstrates the feasibility of topographic anisotropy control.