= Solution
In <current-perpendicular-to-plane magnetoresistance>, the resistance difference between parallel and antiparallel ferromagnetic layers relies on spin-dependent transmission and retention of spin information. Here, an electron traversing the stack must pass a <platinum> layer between the two Co films. Strong <spin-orbit coupling> and associated <spin relaxation> in Pt, together with <spin-memory loss> at interfaces, can reduce the polarization reaching the second Co layer and weaken <giant magnetoresistance>. This is more relevant to the stated perpendicular current than an in-plane shunting explanation.
\b[First, redesign the spacer path so a low-spin-relaxation conductor such as Cu directly separates the two ferromagnets], while retaining perpendicular anisotropy through other interfaces or a different layer sequence. Minimize unnecessary Pt traversal and improve interface sharpness. Merely thinning the Cu layer is not sufficient if it reintroduces magnetic coupling or leaves the Pt spin-relaxation bottleneck unchanged.
\b[Second, replace the metallic spin-transport section with a suitable thin insulating tunnel barrier], for example an engineered MgO-based <magnetic tunnel junction>, and choose compatible magnetic electrodes. Spin-selective tunnelling can give a much larger resistance contrast, but pinholes, disorder and a poorly matched barrier defeat it. Retaining distinct switching fields and a stable antiparallel configuration remains essential in either design.
Back to article page
