Analytic analysis of a dual magnetoresistive head

Abstract

A recently proposed' dual magnetoresistive (DMR) reproduce head. consisting of two identical, adjacent MR stripes separated by a nonmagnetic spacer and connected electrically in parollel, was shown to have potential in very high density magnetic recording applications. The present work considers the micromagnetics of this coupled layer device, and derives ayproximate analytical expressions for the expected signal output as a function of in-track recording density. The results are found to be in good agreement with numerical computations based on reciprocity. Comparison with analytical results for other MR head configurations is discussed. DMRvsis MethQd The basic geometry of a DMR sensor is shown in Fig. I. Identical MR elements I' and 2 carry equal sense current I /2 along the -2 (easy axis) direction, producing opposite polarity bias fields at t e adjacent h!iR layer, and hence nnfisymrnefric bias magnetiza2ns distLbutions %,(x,y) - -&x,y) (f component excluded). The net magnetization Gl t M,,,, t bM,,, also includes the modulation a(x,y) due to signal field from a recorded medium. Given a local resistivity p1 a = po + Ad1 - (MI ,/M,)*) (M, = saturation magnetization), the net resistance R of the DMR'sensor in the two-dhensional approximation is, to order (Aplp,)',