Quantum Mechanics of Spin Transfer in Ferromagnetic Multilayers

TL;DR

This paper presents a quantum mechanical analysis of spin transfer in ferromagnetic multilayers, revealing novel phenomena like spin transmission resonance and magnetoelectric spin echo, and uncovering new mechanisms for zero spin transfer and negative spin torque.

Contribution

It introduces a quantum approach to spin transfer, identifying new effects such as STR and MESE, and explains counter-intuitive spin torque behavior in multilayer systems.

Findings

Identification of spin transmission resonance (STR) and magnetoelectric spin echo (MESE) phenomena.

Discovery of new channels for zero spin transfer in multilayers.

Observation of negative spin torque acting initially on the second magnetic moment.

Abstract

We use a quantum mechanical treatment of a ballistic spin current to describe novel aspects of spin transfer to a ferromagnetic multilayer. We demonstrate quantum phenomena from spin transmission resonance (STR) to magnetoelectric spin echo (MESE), depending on the coupling between the magnetic moments in the ferromagnetic thin films. Our calculation reveals new channels through which the zero spin transfer occurs in multilayers: the STR and MESE. We also illustrate that counter-intuitively, a negative spin torque can act initially on the second moment in a bilayer system.