Film structure dependence of the magnetoresistive properties in current perpendicular to plane spin valves and its relation with current in plane magnetoresistive properties

The magnetoresistive properties of current perpendicular to plane (CPP) spin valves (SV) were investigated for various film structures. CPP-SV elements were fabricated by photolithography and ion-beam etching. As an unexpected result, resistivity change-area product (dRA) improved up to 60% with increasing the PtMn layer thickness from 20 to 40 nm in the bottom synthetic spin valve structure, even though the PtMn layer cannot contribute to the spin dependent scattering. For the free layers, dRA improved with increasing the free layer thickness, although a saturation magnetization (M-s) and free layer thickness were restricted for the head application. Aiming at the enhancement of the spin dependent scattering on the interface, CoFe/NiFe multilayer is adopted as the free layer. Although NiFe improves dR, dRA was not improved with increasing the number of interfaces between CoFe and NiFe when total thickness is kept constant. It also becomes clear that NiFe is the appropriate material in terms of the bulk scattering point of view, although the combination with CoFe at the interface with the Cu spacer is required to avoid intermixing. Dual synthetic spin valve showed better properties, and a dRA of 3.0 mOmega mum(2) was obtained. Since the fabrication of CPP elements requires a time-consuming process, it is desirable to predict the CPP properties in the CIP mode. Although the simple comparison between dR in the CPP mode and conductance change (dG) in the CIP mode through experimental results was attempted, it was recognized that further considerable arrangements were necessary. (C) 2002 American Institute of Physics.