Spin valve structures with artificial antiferromagnets

An artificial antiferromagnetic (AAF) structure as substitute for the ferromagnetic layer may overcome the limitations of sensitivity and dynamic range of a standard spin valve (SV). The AAF consists of two ferromagnetic films (CoFe or NiFe in this article) antiferromagnetically coupled across a thin nonmagnetic layer (Ru). Improved sensitivities combined with high magnetoresistance (MR) ratios and low coercivities and interlayer coupling fields are obtained in NiFe based AAF SVs. The differences between the observed reversal mechanism of SVs with parallel and crossed easy axes configurations have been studied by Lorentz microscopy and correlated with their different MR and sensitivity characteristics.