Recording performance of an inductive-write, wide-shielded MR readback head with a dual layer perpendicular disk

The authors report on vertical recording with a dual-shielded MR (magnetoresistive) element and a piggyback inductive write head designed for longitudinal recording. Readback from the dual-layer rigid disk is characterized by a step-function isolated pulse. The authors evaluate the performance of this system as seen by a channel that consists of peak-detect circuitry preceded by an electronic differentiator. The head-disk-filter system is compared to a system composed of the same head and a low-noise longitudinal thin-film disk. Results include isolated pulse amplitude and shape, media noise, and overwrite. Also included are error-rate results showing the off-track capability. It is shown that, when using the same head, vertical appears marginally better at best. Including the differentiator, vertical shows a slightly improved resolution. This equalization, however, brings the signal-to-noise to similar levels between both technologies. Vertical has superior writability, with a 30-dB overwrite advantage on a thicker, higher-coercivity disk. However, the 50-dB overwrite of longitudinal is more than sufficient. Neither technology should have an advantage in off-track capability, this being determined by the independence of the read and write heads. Due to its unique off-track pickup, vertical recording has more constraints in head design. Ultimately, the advantage, if any, of MR on vertical will be found by developed heads specifically for this purpose and detection schemes that work more efficiently with a step-function pulse