A study of spin-flipping in sputtered IrMn using Py-based exchange-biased spin-valves

To study spin-flipping within the antiferromagnet IrMn, we extended prior current-perpendicular-to-plane giant magnetoresistance studies of Permalloy (Py)-based exchange-biased-spin-valves containing IrMn inserts to thicker IrMn layers-5 nm≤ t IrMn ≤30 nm. Unexpectedly, A Δ R = A ( R AP − R P )-the difference in specific resistance between the antiparallel (AP) and parallel (P) magnetic states of the two Py layers-did not decrease with increasing t IrMn , for t IrMn ≥5 nm, but rather became constant to within our measuring uncertainty. This constant looks to be due mostly to a new, small magnetoresistance in thin Py layers. The constant complicates isolating the spin-diffusion length, l sf IrMn , in bulk IrMn, but l sf IrMn is probably short, ≤1 nm. Similar results were found with FeMn.