Quantum Theory of Giant Magnetoresistance of Spin-Valve Sandwiches

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Abstract
Using Kubo formalism, we develop a quantum-statistical theory of the magneto-resistance properties of spin-valve sandwiches of the form: substrate |F1|Cu|F2|FeMn. F1 and F2 are ferromagnetic transition metals or their alloys, the magnetization of F2 is constrained by exchange anisotropy. The model is based on the coherent interplay between F1 and F2 of spin-dependent scattering phenomena occurring in the bulk of the ferromagnetic layers. We first study the case of F1|Cu|F2 sandwiches with specular reflexion on outer boundaries (which is equivalent to the case of infinite multilayers). Scattering at the substrate |F1 interface is then considered also taking into account the highly resistive FeMn layer. Within these conditions, we obtain good quantitative agreement with experimental data. The results of this quantum-theoretical interpretation are then compared to those obtained by a classical approach based on the Fuchs-Sondheimer theory.