DFL reader signal sidebump imbalance reduction

Abstract

A dual free layer (DFL) read head or reader oftentimes has a sidebump in a signal amplitude vs. cross-track profile plot. The sidebump is a magnetic signal of the reader in response to the magnetic field of magnetic media with finite thickness. The sidebump magnitude is far below the main magnetic signal of the reader and is offset from the center of the track in the cross-track direction. When two sidebumps are present (one on each side of the center of the track), the sidebump should generally and ideally be symmetrically offset in the cross-track direction else there is a negative impact on reader performance. To obtain offset symmetry, a synthetic antiferromagnetic (SAF) shield may be used, magnetic moments of soft bias layers can be adjusted, and spacing between the free layers of the DFL read head and the layers of the soft bias can also be adjusted.

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