Keepered media/contact head performance or life beyond contact recording

Longitudinal thin-film rigid disk media with an overlying high permeability, low coercivity “keeper” layer is shown to improve inductive head performance beyond the limit of contact recording. Data taken with a Read-Rite tripad pseudo-contact inductive thin-film head shows that the keeper layer improves peak-detector channel margin by 25% and reduces soft error rate by 6 orders of magnitude. The keeper layer improves system signal to noise ratio by 3 dB to 6 dB, and reduces PW-50 from 0.292 μm (11.5 μin) to 0.228 μm (9.0 μin). A fly height study shows that the keeper layer allows an additional 25 nm (1 μin) higher flying height than standard media for equivalent channel margin or soft error rates. A model, treating the keeper layer as a magnetic parametric amplifier is proposed. Calculations show that the keeper layer modulates the inductance of the tripad head by 25 nano-Henrys, or about 5% of the total inductance