Spin valves exchange biased by IrMn/PtMn laminated antiferromagnets

This investigation has examined the use of the laminated antiferromagnet Pt Mn/IrMn to exchange bias spin valves in an attempt to combine the high exch ange field and blocking temperature of PtMn with the good pinning profile o f IrMn. The effect of varying the IrMn thickness was examined for top and b ottom spin values exchange biased by CoFe20 Angstrom/IrMn/PtMn. For top spi n valves, H-ex rapidly decreases as IrMn thickness is increased, with the e xchange pinning virtually disappearing by 20 Angstrom. As the thickness con tinues to increase the pinning reappears, and by 40 Angstrom of IrMn an exc hange field of 500 Oe and coercivity of 100 Oe are observed. This exchange field is slightly higher than that observed for CoFe/IrMn40 spin valves (40 0 Oe as deposited, 470 Oe after annealing). For bottom spin valves the same trends are observed, although the pinning never completely disappears. Als o, the exchange field of 600 Oe is lower than that obtained for IrMn (670 O e), presumably due to the rougher interface of the PtMn underlayer. For bot h top and bottom spin valves the laminated antiferromagnet showed improveme nt in thermal stability compared to as deposited and annealed IrMn spin val ves. (C) 2000 American Institute of Physics. [S0021-8979(00)60208-6].