High density recording with keepered media and planar heads

Modeling and experimental results are presented for keepered longitudinal recording media and planar (undershoot-reduced) thin film recording heads with low flying heights for areal densities >1 Gb/in.2. The keeper layer is magnetically coupled to the medium magnetic transitions, reducing the transition demagnetization and narrowing the transition length by about 10% in the media after recording. The reproduced bias field and the transition fields combine in the keeper to produce a partially saturated region, thereby modifying the fields from the medium transitions at the head during playback. We present experimental data on the write and read process for keepered media. Boundary element model results are presented which explain the amplitude gain and pulse asymmetries observed experimentally. Use of a keepered medium allows areal density improvements >20% through higher bits per inch.