Improved reciprocity calculation method for sensitivity profile of GMR heads

For most situations GMR heads can be treated as a linear response sensor, and for such linear systems calculation of the read sensitivity profile by using reciprocity is quite a useful tool. The read sensitivity profile can be calculated as the field due to an imaginary coil wound on the GMR film, which in turn may be replaced by imaginary magnetization. In most applications, the magnetization is arbitrarily given, and usually the entire GMR free layer is given imaginary magnetization, which is uniform over the whole film plane. However, the imaginary magnetization should be a function of the location on the GMR film. This paper proposes a more accurate method of calculation using reciprocity, using an imaginary magnetization obtained by a micromagnetics model.