The dependence of specularity behavior and thermal stability on capping layer thickness in spin valves

Abstract

We investigated the dependence of capping layer thickness and composition on Mn diffusion and specular reflection behavior in top spin valves. The capping layer materials used included an amorphous ZrAl alloy that was oxidized completely when its thickness was 2nm, improving both the thermal stability and magnetoresistance ratio of the spin valves (SVs). Mn diffusion into the active sensing layer was inhibited markedly when the 2-nm-thick capping layer was present, as this oxide layer provides an oxygen potential gradient along which Mn diffuses preferentially. The thermal stability of a ZrAl-based SV proved greater than that of a traditional Ta-based SV owing to its interdiffusion-resistive microstructure, which provides both a smoother surface and a fine and dense microstructure that lacks crystallinity.