Effect of short-duration annealing on the exchange bias in IrMn/Co films

The present study discusses on modification of the exchange-bias parameters due to magnetic annealing during 15 min of sputtered IrMn/Co and IrMn/Cu(0.25 nm)/Co films. The annealing temperature Tann has been systematically varied in the presence of sufficiently strong magnetic fields to ensure saturation of the ferromagnetic layers. Broad maxima at Tann∼200 deg. C have been observed in the in-plane exchange-bias field Heb versus Tann variations for both series of samples. Numerical simulations have been employed in order to fit the magnetization curves in both easy and hard axis configurations from which the magnetic anisotropy parameters were extracted. This work indicates that, in the films studied, an improvement in the bulk IrMn crystallinity and/or grain growth, which may lessen the number of uncompensated spins at the last-grown IrMn sublattice, seems to be a plausible candidate to account, in part, for the observed decrease of Heb after rapid anneal for Tann between 200 and 300 deg. C. This mechanism might be considered as an alternative and/or adding to the commonly observed IrMn and Co interdiffusion. - Highlights: → We studied modifications of the exchange bias (EB) parameters due to rapid anneal of IrMn/Co films. → Broad maxima were observed in the EB field versus annealing temperature dependencies at ∼200oC. → The EB field decreases after rapid anneal using temperatures between 200 and 300 deg. C. → An improvement in the IrMn crystallinity or grain growth could account, in part, for this decrease. → This mechanism for the EB decrease might be considered as adding to that of IrMn/Co interdiffusion.