Effect of different compositions of CoFeB spin polarizer on magnetoresistance and switching property of Co/Pd multilayers with perpendicular magnetic anisotropy

The effect of magnetization of the spin-polarizing layer (SPL) on the magnetoresistance (MR) is investigated by using different compositions of Co _xFe _80-xB ₂₀ (x 60, 40, and 20) as spin polarizers in Co/Pd multilayers-based pseudo-spin-valves with perpendicular magnetic anisotropy (PMA). In the case of as-deposited films, the giant magnetoresistance (GMR) was found to decrease with increase of CoFeB thickness from 5 Å to 10 Å. However, after post-annealing at 250°C, 10 Å samples showed a peak of GMR in all compositions. Further increase in annealing temperature causes a reduction in GMR, which was found to be larger in samples with a lower saturation magnetization (M _s). As a function of SPL thickness, the GMR decreases in the case of as-deposited samples. However, post-annealed samples show a larger MR in case of thicker SPL. In the case of thick CoFeB SPL, the magnetization of the soft layer appears to be canted out of the plane. Among the three compositions investigated, the Co ₆₀Fe ₂₀B ₂₀ polarizer shows a stronger PMA due to its lower M _s, leading to the weaker demagnetization.