Annealing effect on exchange bias in Ni/sub 81/Fe/sub 19//Cr/sub 50/Mn/sub 50/ bilayers

The effect of annealing on the exchange bias in Ni/sub 81/Fe/sub 19//Cr/sub 50/Mn/sub 50/ bilayers was investigated. A large increase of the exchange field and coercivity was observed in the samples annealed at temperatures higher than 310/spl deg/C. The annealing causes the Mn atoms in the Cr/sub 50/Mn/sub 50/ layer to diffuse into the Ni/sub 81/Fe/sub 19/ layer and form an antiferromagnetic NiFeMn phase, which coats on the Ni/sub 81/Fe/sub 19/ grain surface and contributes to the improvement of exchange bias. An increase of interface roughness due to the Mn diffusion also results in the exchange bias enhancement. The enhanced exchange field and coercivity were explained by the reversible and irreversible motions of NiFeMn moments of the inhomogeneous grains.