Enhanced giant magnetoresistance in Heusler alloy ( Co 2 FeSi

Abstract

We theoretically investigate the spin transport behavior of multilayer (Co2FeSi/Ag)N structure for the application of next-generation read sensor in hard disk drive. To demonstrate the potential of Heusler alloy-based current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) device, we employ the atomistic model coupled with the spin accumulation model including the effect of diffuse interface. The dynamic of magnetization is observed by the atomistic model and the calculation of magnetoresistance (MR) and MR ratio of the magnetic structure can be achieved by the spin accumulation model enabling us investigate the spin transport behavior within the structure. The MR value can be directly calculated from the gradient of spin accumulation and spin current. The effect of injected current density is first investigated. It is found that increasing current density results in high MR ratio. Subsequently, to achieve high performance reader, the number of coupled layers (N) is varied up to 16 to study its effect on the MR ratio. The calculated results indicate that increasing the number of layers N gives rise to the enhancement of the resistance change and MR ratio. At the critical point N=5, further increasing N does not affect the MR ratio, which remains relatively unchanged. Interestingly, the MR ratio is doubled for N>5 compared to N=1. Our results show the possibility to enhance the performance of multilayer CPP-GMR device.