Tunneling magnetoresistance in exchange-biased CoFeB/AlO_x/Co/IrMn junctions

摘要

A series of exchange-biased magnetic tunneling junctions (MTJs) were made in an in-plane deposition field (h) = 500Oe. The deposition sequence was Si(100)/Ta(30A)/CoFeB(75A)/ AlO_x(d A)/Co(75 A)/IrMn(90 A)/Ta(100 A), where d was varied from 12 A to 30 A. The MTJ was formed by the cross-strip method with a junction area of 0.0225 mm2. The tunneling magnetoresistance (AR/R) of each MTJ was measured. The high-resolution cross-sectional transmission electron microscopic (HR X-TEM) image shows the very smooth interface and clear microstructure. X-ray diffraction (XRD) demonstrates that the IrMn layer of the MTJ exhibits a (111) texture. From the results (ΔR/R) increases from 17% to 50%, as d increases from 12 A to 30 A. The tnnneling resistance (R_o) of these junctions ranges from 150 Ω to 250 Ω. The exchange-biasing field (H_(ex)) of the MTJ is 50-95 Oe. Finally, the saturation resistance (R_s) was measured as a function of the angle (α) of rotation, where α is the angle between h and the in-plane saturation field (H_s) = 1.1 kOe. The following figure presents the dependence of R_s on α, instead of originally expected independence, the curve actually varies with a period of π.