A magnetoresistive gradiometer for detection of perpendicularly recorded magnetic transitions

Abstract

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.