Effect of interface intermixing on the magnetoresistive and the exchange coupling in bottom- And top-spin valves

We investigated the interfacial mixing phenomena associated with magnetoresistance and exchange coupling in a top spin valve (T-SV) and bottom spin valve (B-SV) at IrMn/CoFe and CoFe/IrMn interfaces. The difference in the surface free energies of IrMn and CoFe is the major factor determining the degree to which interfacial mixing occurs, but it depends on the deposition sequence. A B-SV featuring a gradational IrMn/CoFe interface had a small H _ex in the as-deposited state, but showed improved exchange coupling on annealing as a result of limited interdiffusion. By contrast, a T-SV featuring a sharp CoFe/IrMn interface had a high H_ex in the as-deposited state, but suffered a reduction in exchange coupling on annealing, due to a moderate level of interdiffusion.