Large magnetoresistance in Heusler alloy-based current perpendicular to plane giant magnetoresistance sensors

Increasing the data storage in next-generation hard disk drives requires a reduction in the physical dimensions of read sensors. Tunneling magnetoresistance heads yield high magnetoresistance (MR) ratio but with a high resistance-area product (RA) that is suboptimal for devices. Giant magnetoresistance (GMR) head using different materials is an alternative way to improve reader performance with high MR ratio and low RA. In this paper, we theoretically study the effect of material properties and the layer thickness on RA and MR ratio in a trilayer system via an atomistic model combined with the spin transport model. The GMR stack can be constructed by the atomistic model and the RA and MR ratio can be directly calculated by considering the spin accumulation and spin current from the spin transport model. It is found that the spin valve using the Co2FeAl Heusler alloy electrode with high spin polarization exhibits a high MR ratio and RA of 64 m Omega mu m(2) which is better than the spin valves using conventional ferromagnets such as Co, NiFe and CoFe. Moreover, we consider the thickness dependence of the change of RA (Delta RA). Increasing the free layer thickness yields the increase in Delta RA and MR ratio because of the enhancement of the bulk spin scattering. Additionally, the results show that the Delta RA depends on the spin diffusion length of the nonmagnetic materials (lambda(sdl,NM)). The Delta RA increases from 3 up to 10 m Omega mu m(2) when lambda(sdl,NM) increases from 35 to 1200 nm. This investigation shows the possibility for read head design of HDDs with areal density beyond 2 Tb in(-2).

Automated summary

This paper explores the use of GMR heads to improve reader performance by studying the effect of material properties and layer thickness on RA and MR ratio. It is found that using a Co2FeAl Heusler alloy electrode in the spin valve leads to better performance compared to conventional ferromagnetic materials. Additionally, the study considers the thickness dependence of Delta RA and its relationship with the spin diffusion length of nonmagnetic materials.