Magnetoresistive sensor having antiferromagnetic layer for exchange bias

Abstract

A magnetoresistive (MR) sensor comprising a sputtered layer of ferromagnetic material and a sputtered layer of antiferromagnetic nickel-manganese (Ni-Mn) to provide an exchange coupled longitudinal bias field in the MR element is described. The antiferromagnetic layer overlays the MR layer and may be patterned to provide the longitudinal bias field only in the end regions of the MR layer. Alternatively, the antiferromagnetic layer can underlay the MR layer with a Zr underlayer to enhance the exchange-coupled field. As initially deposited, the Ni-Mn layer is face-centered-cubic and exhibits little or no exchange-coupled field. After one annealing cycle at a relatively low temperature, the Ni-Mn layer is face-centered-tetragonal and exhibits increased crystallographic ordering and provides sufficient exchange coupling for the MR element to operate. Addition of chromium to the Ni-Mn alloy provides increased corrosion resistance.

Dependencies are inferred from the claim text.