Tuning perpendicular exchange bias in IrMn/[Co/Pt] and IrMn/CoFe/Co/[Pt/Co] systems with ultra thin Pt layers

As-deposited IrMn/[Co/Pt] systems with ultra thin Pt layers (∼5.0 Å) have no perpendicular exchange bias and exhibit in-plane anisotropy. After perpendicular field-annealing, the perpendicular exchange bias is established and can be tuned by the Co thickness. It is found that the perpendicular exchange bias of IrMn/[Co/Pt] systems with ultra thin Pt layers appreciably surpasses that of the ever reported counterparts which contains relatively thick Pt layers. Perpendicular field-annealing also promotes a perpendicular orientation of magnetization, and a well-defined perpendicular anisotropy is obtained for an intermediate Co thickness. By replacing Co layer adjacent to IrMn with Co60Fe40/Co bilayer, the perpendicular exchange bias is drastically enhanced, and extremely tiny Co60Fe40 can yield a perpendicular exchange bias far superior to that of previously reported IrMn/Co60Fe40/[Pt/Co] system with Co60Fe40 layer of 6.0 Å.