Effect of Top, Bottom, On- and Off-Axis Deposition on the Blocking Temperature Distributions of Exchange Biased Bilayers

In exchange biased spintronic devices such as magnetic random access memories, spin-glass-like regions are randomly spread over ferromagnetic/antiferromagnetic interfaces. They contribute to detrimental distributions of exchange bias properties from memory cell to memory cell. The integrated area of the low-temperature (T) contribution of the blocking temperature (T_B) distribution provides information about the amount of these spin-glass like regions. In this paper, we report on the influence of various growth conditions on the low-T contribution of the T_B distributions for cobalt/iridium-manganese (IrMn) based bilayers. Top, bottom, on- and off- axis depositions were compared. We show that off-axis deposition, i.e., when the target and substrate are off-centred, does not reduce the low-T contribution despite an expected smoother F/AF interface. We observe that bottom deposition, i.e., when IrMn is deposited first, allows reducing AF spin-glass like regions as compared to top deposition. This contributes to improved exchange bias properties.