Enhanced giant magnetoresistance in Heusler alloy (Co2FeSi/Ag)N multilayers for read sensor applications

We theoretically investigate the spin transport behavior of multilayer [Co2FeSi/Ag]N structure for the application of next-generation read sensors in hard disk drive. To demonstrate the potential of the Heusler alloy-based current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) device, we employ an atomistic model coupled with a spin accumulation model including the effect of a diffuse interface. The dynamics of magnetization is observed in 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 to 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 the current density results in a high MR ratio. Subsequently, to achieve a 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 demonstrate the possibility of enhancing the performance of multilayer CPP-GMR devices.