Nonlinear response in magnetostrictive sensors significantly affects the spin-stand parametric measurements used to characterize writer and reader performance of recording heads. A simple production level test defined as the nonlinear distortion (NLD) ratio was used to quantify the degree of reader nonlinearity. A positive NLD value represents the presence of reader distortion while a value of zero represents no distortion. On a large population of heads tested, the median NLD value was 0.25, which is equivalent to an amplitude loss of 10 for an isolated pulse due to reader saturation. A detailed analysis of the measured data on nonlinear transition shift, partial erasure, and PW50 of these production heads show that greater than 50 of the measured variance is due to readback nonlinear distortion rather than true performance variation of the device.
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