Interlayer Exchange Coupling, Spin Pumping and Spin Transport in Metallic Magnetic Single and Bilayer Structures

Abstract

Interlayer exchange coupling in thin films is one of the cornerstones of modern spintronics-based technology. This phenomena has been an active area of research for several decades. Such a large area of research is impossible to cover in a single review, therefore the focus of this paper is a few coupling mechanisms relevant in ultra-thin film structures. The first part of the paper covers static interlayer exchange coupling, providing a brief overview of various coupling mechanism including a new mechanism of non-collinear coupling which is attractive to spintronics applications. The next part discusses proximity polarization coupling which can appear as a dominating coupling mechanisms in Stoner enhanced materials. The final part of the paper reviews spin pumping as a form of dynamic coupling. A description of spin pumping is presented as an extension of static, RKKY coupling into dynamic coupling by allowing for a time-delayed response. This approach makes a natural connection between static and dynamic coupling. We also present a detailed derivation of the conventional derivation of spin pumping in a reparameterized form. This model is only applicable for highly conductive materials but fails for materials with large spin-orbit coupling. In view of this we review several spin pumping studies in Au, Ag, Pd, and Pt which explore the adequacy of this model and its limits.