Enhanced In-stack Longitudinal Biasing for CPP CPP-GMR Heads

Abstract

We investigated enhanced in-stack longitudinal biasing, which was newly designed to strengthen longitudinal biasing by investing the antiferromagnetic exchange coupling, H_{int, LBL}, in a spacer between a free and a ferromagnetic layer of the in-stack biasing layers. Micromagnetic simulation showed that H_{int, LBL} diminishes hysteresis and improves the linearity of a transfer curve through cooperation with a magnetostatic coupling effect at the sensor edges. We found that CPP-GMR sensors with various H_{int, LBL} values and magnetostatic coupling effects were formed by adjusting the thickness of the spacer and the ferromagnetic layer. Transfer curve measurements for fabricated head devices using such CPP-GMR sensors revealed that H_{int, LBL} played an importance role in diminishing hysteresis in transfer curves, and that higher output was obtained at moderate H_{int, LBL} values. Consequently, the enhanced in-stack longitudinal biasing was demonstrated to have both higher stability and higher output.