Dfl reader signal sidebump imbalance reduction

Abstract

A dual free layer (DFL) read head 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. 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. The sidebump presence indicates that the magnetic signal of the reader is a little out of phase. When a pair of sidebumps is present, the sidebump should be symmetrically offset in the cross-track direction else there is a negative impact on reader performance. To obtain offset symmetry, a synthetic antiferromagnetic 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.