Micromagnetics of GMR spin-valve heads

Three-dimensional micromagnetic modeling of shielded giant magnetoresistive heads with a spin-valve sensor is presented. If the pinning field from the exchange layer is not large enough, partial unsaturation of the pinned layer occurs upon excitation from the medium, which may cause down-track output noise. Increasing the pinning strength diminishes the playback instability, however, a larger sensor height is then desirable for the ease of proper biasing, but at the expense of on-track signal level. The free layer magnetization is nominally horizontal, reducing off-track asymmetry compared to heads with smaller sensor height.