Thickness and annealing temperature dependence of perpendicular exchange biasing in [Pd/Co]/FeMn multilayers

The thickness of Pd, Co, FeMn, and buffer (Ta, Pd) layers and annealing temperature dependences on perpendicular exchange biasing field (H_ex) and coercivity field (H_c) in Ta(Pd)/[Pd/Co]_n/FeMn/Ta(Pd) multilayers are investigated. Hysteresis loops with perpendicular magnetization curves were measured using extraordinary Hall effect. Increase in the thickness of buffer Ta layer lead to the enhancement of both H_ex and H_c. The H_ex of 0.1 nm Pd sample increased slightly from 125 Oe to 145 Oe, and vanished at 0.5 nm Pd. As the Co thickness decreases, the H_ex and H_c increased up to 360 Oe and 633 Oe in 0.48 nm and 0.32 nm Co sample, respectively. H_ex increased up to 130 Oe as the FeMn thickness increases to 12 nm, and decreased to 90 Oe at 21 nm FeMn thickness. H_ex is also observed to increase as the annealing temperature increases. At 330 °C, the perpendicular anisotropy disappeared.