Spin-valve thermal stability: The effect of different antiferromagnets

This investigation focused on how spin-valve thermal stability is related t o different antiferromagnetic materials: FeMn, IrMn, NiMn, PtMn, and PtPdMn . Measurements of the spin-valve exchange biasing field versus temperature show the following relationship in blocking temperatures: FeMn < IrMn < PtP dMn < PtMn < NiMn. Looking at the blocking temperature distributions, both FeMn and IrMn show sharp peaks, but at low temperatures (similar to 110 deg rees C). In the case of the other materials, the distribution peaks at much higher temperature (> 250 degrees C), but are broader. Pinned angle rotati on and giant magnetoresistance versus temperature measurements give the sam e thermal stability hierarchy, as well as providing information about inter diffusion in these spin-valves. For comparison, synthetic antiferromagnet s pin-valves (based on IrMn and PtMn) were also measured. The synthetic struc tures did not show significantly different blocking temperatures or giant m agnetoresistance temperature dependence than standard spin-valves. However, blocking temperature distribution and pinned layer rotation measurements s howed improved stability for the synthetic structures, which may be attribu ted to the very thin effective pinned layer which results in high exchange biasing fields in these structures. (C) 2000 American Institute of Physics. [S0021-8979(00)73608-5].