Copper spacer thickness dependence of the exchange bias in IrMn/Cu/Co ultrathin films

The exchange-bias, HEBHEB and coercivity, HCHC of IrMn/Cu(tCu)/CoIrMn/Cu(tCu)/Co films have been investigated as a function of the Cu spacer thickness, tCutCu before and after magnetic annealing. A large increase of HEBHEB and a significant decrease of HCHC with the treatment were observed for the samples with tCu⩽1.0nm. HC(tCu)HC(tCu) and HEB(tCu)HEB(tCu) showed a general trend of rapid decrease for all samples. The phenomenological models used to derive the anisotropy and exchange coupling parameters from the magnetization data indicated that the antiferromagnetic part of the interface is fully spin-compensated for the as-made films and nearly uncompensated for the treated ones. The annealing, despite the HEBHEB and HCHC changes, did not alter the Co anisotropy but only improved the interfacial IrMn spins alignment.