Spin-filter spin-valve films with an ultrathin CoFe free layer.

The concept of spin-filter spin-valve (SFSV) films is reviewed. The dependence of the free layer structure on the spin-filter effect was investigated by using model films and two types of free layers were compared, a single CoFe layer and a conventional NiFe/Co free layer. At the same magnetic thickness of the free layer, the SFSV films with a CoFe free layer showed a larger magnetoresistance (MR) ratio than those with a NiFe/Co free layer. This is partly attributed to the thinner CoFe free layer thickness, which is due to the fact that the CoFe free layer has higher B[sub s] than the NiFe/Co free layer. Moreover, SFSV films with a CoFe free layer still showed a larger MR ratio when the free layer thickness was the same. It suggests that other factors contribute to the high MR performance, such as the quality of the interface between a free layer and a high conductance layer. Film performance of MR 9% to 10%, ΔR[sub s] 1.5-2.0 Ω, H[sub c][sup ea]∼3 Oe, and λ[sub s]≤±0.5 ppm was obtained with a single CoFe free layer and synthetic antiferromagnetic pinned structure. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]