Current perpendicular-to-plane giant magnetoresistance using an L12 Ag3 Mg spacer and Co2 Fe0.4 Mn0.6 Si Heusler alloy electrodes: Spacer thickness and annealing temperature dependence

Spacer thickness tN and annealing temperature Tanneal dependence of current perpendicular-to-plane giant magnetoresistance effects were investigated in junctions using L12Ag3Mg spacer and half-metallic Co2Fe0.4Mn0.6Si (CFMS) Heusler alloy electrodes. tN was changed from 2-12 nm and Tanneal was changed from 450-650°C to promote the chemical ordering of the CFMS electrodes. Concerning the tN dependence, the magnetoresistance (MR) ratio and the change of the areal resistance (ΔRA) exhibited the maximum values at tN=5nm. The reasons for the decrease of the MR ratio for tN<5 nm and for tN>5 nm were possibly due to an unstable antiparallel magnetization configuration and to the increased occurrence of spin scattering inside the Ag3Mg spacer, respectively. The spin-diffusion length of the Ag3Mg spacer was also estimated using the tN dependence of ΔRA and it was found to be of the order of 10-30 nm. Concerning the Tanneal dependence, ΔRA and the MR ratio exhibited the maximum values at 550°C, which was the optimum point in terms of the degrees of order in the CFMS layers and the Ag3Mg layer, and the (001) orientation of the layered structure. The maximum ΔRA and the intrinsic MR ratio in which parasitic resistance contribution was eliminated were 25mΩμm2 and 63%, respectively, at room temperature.