Understanding of amplitude symmetry and its variation of synthetic spin valve heads for high density recording

Abstract

In synthetic antiferromagnetic spin valve (SAF–SV) recording heads, as SV sensor dimensions approach the nanometer scale and individual layer thickness shrinks to only a few angstroms, it becomes more challenging to achieve a unity amplitude symmetry (LFA–SYM) and a small variation of LFA–SYM. A better understanding of LFA–SYM, good control of its variation, and an effective measurement of SAF–SV canting angles has become more important. In this study, high field transfer curve (HF–Xfer) was measured to determine head magnetic polarity, bias point, and output linearity. Rotational field transfer curve (RF–Xfer) was measured to determine the canting angles of reference layer and pinned layer. Free layer canting angle, its dependence on magnetic field, and the angle between the reference layer and free layer were consequently determined based on HF–Xfer and RF–Xfer data. A good linear correlation between LFA–SYM and free layer canting angle was observed, indicating that the large variation of LFA–SYM was mainly due to a wide range of free layer canting.