Effects of reader distortion on nonlinear transition shift measurements

As longitudinal magnetic recording densities continue to grow, researchers face a growing problem of nonlinearity in the recording process. The fifth harmonic nonlinear transition shift (NLTS) has traditionally been used to measure the degree of nonlinearity in the write process. Recently, the effects of nonlinear distortion in the readback process were described and the distortion was attributed largely to saturation of the giant magnetoresistive (GMR) sensor. We describe the effects of reader distortion due to asymmetry on the measured NLTS and explain a quadratic dependence of NLTS on asymmetry that is observed experimentally.