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

Abstract

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 ≤ tIrMn ≤ 30 nm. Unexpectedly, AΔR = A(RAP − RP)—the difference in specific resistance between the antiparallel (AP) and parallel (P) magnetic states of the two Py layers—did not decrease with increasing tIrMn, for tIrMn ≥ 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, lsfIrMn, in bulk IrMn, but lsfIrMn is probably short, ≤1 nm. Similar results were found with FeMn.