A negative transition width in perpendicular recording?

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Abstract
In perpendicular recording, the measured density response curve corrected with gap, spacing, and thickness losses may show a positive slope. This corresponds to an unphysical negative transition width in an arctangent transition. Analysis has been done to understand this phenomenon. We found that for a perpendicular media with Hc much less than 4πMs, an isolated transition is partially demagnetized in the tail region and consists of more high frequency component than an arctangent transition. By linear superposition, the high frequency readback amplitude can be boosted by this enhanced high frequency spectrum in the isolated pulse. The readback resolution of a thick perpendicular media in fact is equivalent to an infinitesimally thin longitudinal media with extremely narrow transition width. However, the readback amplitude is higher due to the thicker magnetic layer. As to a perpendicular media with Hc greater than 4πMs, the so‐called ‘‘negative transition width’’ does not occur and the resolution of the readback signal becomes relatively poor.