Thermomigration-induced magnetic degradation of current perpendicular to the plane giant magnetoresistance spin-valve read sensors operating at high current density

Abstract

The theoretically analyzed physical mechanism of thermomigration (TM)-induced magnetic degradation that occurred in the current perpendicular to the plane (CPP) Ir20Mn80 exchange biased giant magnetoresistance spin-valve (EBGMR SV) read sensors is presented. The device size was changed from 60×60 to 140×140 nm2 at the fixed aspect ratio of 1(L):1(W), and the operating current density was varied from J=1×108 A/cm2 to J=5×108 A/cm2 in a current control mode. It was numerically confirmed that the Mn atomic interdiffusion through the Ir20Mn80/Co80Fe20 interface due to the thermally induced mass transport and the “Villari magnetic reversal” of the CoFe pinned layer due to the thermally induced stress are mainly responsible for the serious degradation of exchange bias and magnetoresistance. Furthermore, the TM-induced magnetic degradation of CPP EBGMR SV read sensors was found to become severe by increasing the operating current density. However, interestingly, this undesirable magnetic degradation was dramatically diminished by reducing the read sensors below 100(L)×100(W) nm2.