  The downtrack responses of a differential reader to various magnetic patterns
have been investigated micromagnetically. The differential signals can well
discriminate the "0" and "1" readback bits and the waveforms obtained resemble
the counterparts for longitudinal media or for perpendicular media after
differentiation. Pulse shapes are found Gaussian. With decreasing head media
spacing, free layer thickness, and gap length, PW50 roughly linearly decreases
and the maximum signal exponentially increases. These properties, together with
small inter-symbol interference, are essential for future high density magnetic
recording.
