Thomas Joseph Beaulieu

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. >

Track density limitation for dual-layer perpendicular recording in a rigid disk environment

The authors report on the linear and track density capability of a 10- mu m-wide, 31-turn inductive probe head flying at 130 to 160 nm over a dual-layer CoCrTa/NiFe disk. On-track recording results show that excellent writability is accompanied by reduced readback resolution. Off-track capability is evaluated in the presence of previously written information at a data rate of 3 Mbytes/s for a linear density of 1181 b/mm using a

The contribution of the magnetic medium to phase shift and resolution in magnetic recording

Phase shift in a 16-bit 3200 flux-change-per-inch (fci) coded pattern was studied. The pattern was written on thick particulate γ-Fe 2 O 3 tapes, and statistical data were accumulated with a measurement accuracy of about one tenth of one percent. All tapes were unoriented, with remanent moments ranging from 5 to 70 EMU/cm3, coercivities between 200 and 360 Oe, and coating thicknesses between 160 and 700 μin. The position of a peak in time (its phase information) affects recording resolution. To date, most definitions of recording resolution have concerned the properties of isolated pulses such as the half pulsewidth. It is clear that the isolated pulsewidth conveys no information on the timing of the pulse. Resolution, in the context of isolated pulses, is expected to increase as the ratio H_{c}/I_{r} increases. Our results show that phase shift is not minimized, in general, for the medium with maximum H_{c}/I_{r} . In addition, asymmetric phase shifts in a coded pattern were observed, and these cannot be explained by time-independent linear superposition of fundamental pulses. It is suggested that such phase shift studies are a necessary addition to isolated pulsewidth studies if recording resolution and reliability are to be better understood.