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A magnetoresistive gradiometer to detect perpendicularly recorded transitions has been conceived. It utilizes two parallel magnetoresistive stripes with opposing sense/bias currents. The magnetoresistive elements mutually bias each other with the same polarity bias fields. The fields of a perpendicular transition centered between the two stripes increase the resistance of one stripe while decreasing that of the other, therefore providing maximum output signal using differential detection. The detector provides a Lorenztian-type readback waveform and rejection of common-mode noise. The experimental readback waveform exhibited a pulse width at half maximum of 0.7 μm for a head flying at 0.2 μm above the media surface.

Comparisons of magnetic anisotropy and switching behavior of CoCr-based alloy and Co/Pd multilayer media were made using a vector vibrating sample magnetometer. Magnetic anisotropy energy was determined from angle-dependent measurements of the transverse magnetization, using a simple approximate expression for transverse moment versus applied field and rotation angle. Switching behavior was deduced from hysteresis and angle-dependent energy-loss measurements. The multilayers were found to switch by curling and domain wall motion, while the Co78Cr17Ta5 and Co70Cr15Ta5Pt10 media were found to switch by nearly coherent (Stoner–Wohlfarth) rotation. Plasma oxidation of the multilayers was found to slightly reduce the amount of coupling, but degraded readback amplitude to a contact recording transducer.

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In recent years, efforts in the industry to reduce head/media spacing loss and increase areal recording density, for the most part, have been directed toward reducing the size and mass of air bearing sliders to enable very low flying height. An alternative to this strategy aims at operating ultra low mass heads in continuous sliding contact with the media. This paper, will summarize the progress that has been achieved at Censtor Corp. over the past several years in this latter approach to extending recording density, which is now being implemented in small form factor disk drive designs.