Effects of sputter-deposition-induced and post-deposition thermally activated intermixing on the exchange bias properties of (Pt/Co) ×3 /(Pt)/IrMn films

The effects of sputter-deposition-induced and post-deposition thermally activated layer intermixing on the exchange bias properties of [Pt/Co]x3/Pt(tPt)/IrMn films with out-of-plane anisotropy and deposited under a perpendicular magnetic field are investigated. The consequences of the intermixing on the magnetic properties are correlated with atom probe structural investigations. We observe that Co–Mn and Co–Pt intermixing are already present in the as-deposited state. The intermixing is more pronounced for Pt on Co (~50%) than for Mn on Co (~10%). It is observed that annealing up to 200 °C does not result in noticeable further diffusion of Mn in Co. In contrast, it significantly accentuates the Co–Pt initial intermixing. This enhanced intermixing leads to a 40% reduction in the exchange bias field. We measured that this reduction is not primarily due to changes in effective anisotropy or in saturation magnetization. This is possibly ascribed to a decrease in the mean interfacial moment and exchange stiffness both due to the observed reduction in Co content within the Co sublayers.