Controlled enhancement or suppression of exchange biasing using impurityδlayers

The effects of inserting impurity δ layers of various elements into a Co∕IrMn exchange biased bilayer, both at the interface and at given points within the IrMn layer a distance from the interface, have been investigated. Depending on the chemical species of impurity, and its position, we found that the exchange biasing can be either strongly enhanced or suppressed. We show that biasing is enhanced with a dusting of certain magnetic impurities, present either at the interface or sufficiently far away from the Co∕IrMn interface. This illustrates that the final spin structure at the Co∕IrMn interface is not only governed by interface structure and/or roughness, but is also mediated by local exchange or anisotropy variations within the bulk of the IrMn.