On the exchange biasing through a nonmagnetic spacer layer

We present results on the magnetic coupling between a ferromagnetic (F) thin film and an antiferromagnetic (AF) thin film through a nonmagnetic metallic spacer (S) layer. Multilayered structures have been grown on silicon substrates using dc magnetron sputtering. We have studied the structure AF/S/F for different materials. AF is Ir22Mn78, F is Fe16Co16, and the spacer S is Al, Ag, Au, Si, Pd, Ru, and Ti. In most cases, both the exchange-bias and the coercive fields decrease exponentially with the spacer thickness with a decay length of a few angstroms, depending slightly on the material. Similar decay lengths are observed for the reversed structure F/S/AF. In some specific cases, we observe a nonmonotonic variation of the exchange-bias field with the spacer thickness. For example, the exchange-bias field increases when a thin Ag layer is inserted between the F film and an AF film grown at high sputter pressure.