Pulse shape, resolution, and signal-to-noise ratio in perpendicular recording

The paper theoretically examines playback characteristics of a giant magnetoresistive (GMR) head for perpendicular recorded magnetization transitions with a soft underlayer. The magnetic scalar potential, calculated numerically by the finite-element method, is fitted to a simple formula involving geometry-dependent parameters. The reciprocity principle leads to the shape of the single pulse signal. For high permeability of the underlayer the pulse has an error function-type dependence on distance. Within this approximation, the paper derives simple formulas for the pulsewidth [T.sub.50], [D.sub.50], and transition-noise-limited signal-to-noise ratio. Index Terms--Magnetic scalar potential, perpendicular recording, resolution, single pulsewidth, SNR.