Magneto-transport and spin-torque effects in current perpendicular to the plane spin-valves with Co-Fe-Al magnetic layers

The magneto-transport of current-perpendicular to the plane giant magneto-resistive spin valves utilizing (Co$_{x}$Fe$_{100-x})_{100-y}$Al$_{y}$ alloys in the reference and free layers is investigated. (Co$_{50}$Fe$_{50})_{75}$Al$_{25}$ is determined to be the alloy composition that maximizes magneto-resistance. At this composition the magnetization is around 1000 emu/cm$^{3}$, which is high enough to be used as magnetic material in spin-valves with ultra-thin read gaps for high recording densities. An improvement in magneto-resistance from 1.7{\%} for spin-valves utilizing Co$_{50}$Fe$_{50}$ in reference and free layers to 3.3{\%} for spin-valves utilizing (Co$_{50}$Fe$_{50})_{75}$Al$_{25}$ with the same ``magnetic'' thickness in both parts of the reference and the free layers were observed. The spin-diffusion length for (Co$_{50}$Fe$_{50})_{75}$Al$_{25}$ is determined to be approximately 30 {\AA}. Spin-torque measurements show that the spin-torque current density threshold is approximately 7$\cdot $10$^{7}$ A/cm$^{2}$ in CoFeAl spin-valves in comparison to 13$\cdot $10$^{7}$ A/cm$^{2}$ in CoFe spin-valves.