Effects of uniform magnetic fields on shielded MR sensors

Standard thin-film techniques were used to construct the shielded magnetoresistive (MR) sensors with soft-adjacent-layer biasing. The authors show the three shield designs included in these tests: a tall and asymmetric shield pair with magnetic leads, a tall and asymmetric shield without the magnetic leads, and a short and symmetric structure. The authors discuss the effects of an externally applied magnetic field which can change the biasing of a magnetoresistive sensor. Under large-signal conditions, this produces preferential saturation of one polarity of the readback signal and changes the amount of waveform distortion. In a shielding MR sensor for hard disk applications, the sensitivity to external fields is affected by the shapes of the shields: tall shields are more sensitive to axial fields; asymmetrically shaped shields can increase the sensitivity to radial fields by converting them to axial fields at the sensor. Moderate fields can sometimes induce small, systematic changes into the small-signal spatial sensitivity