Effect of magnetostatic coupling between free and reference layers on the thermal stability of synthetic spin valves

A relationship between initial ferromagnetic magnetostatic coupling strengt h (H-F) and a long-term thermal stability of the spin valve (SV) sensors wa s investigated. The thermal degradation in GMR properties of SV stacks is m ore apparent in the stack exhibiting a higher initial H-F, and is expedited for the stacks without capping layers. Initial H-F values appear to be one of the good indicators for the long-term thermal stability of SV stacks si nce they reflect the inter-layer microstructure of SV sensor stacks. The or igin of H-F is also discussed by comparing measured H-F values with estimat ed ones.