Role of non-collinear magnetization: from ferromagnetic nano wires to quantum rings

TL;DR

This paper explores how nonuniform magnetization affects electron interactions and domain wall dynamics in ferromagnetic nanowires and extends the analysis to complex magnetization states in quantum rings.

Contribution

It introduces a model for current-induced exchange coupling between domain walls and discusses modifications needed for quantum ring magnetization states.

Findings

Current in nanowires induces exchange coupling between domain walls.

Interaction depends on walls' orientations and separation.

Magnetization states in quantum rings are more complex than in nanowires.

Abstract

We consider interaction effects related to a nonuniform magnetization in ferromagnetic nanowires and their possible generalization to nanorings. First we show that the electric current in a ferromagnetic nanowire with more than one domain wall induces an exchange coupling between the walls mediated by the spin-dependent interference of scattered carriers. This interaction reveals a complex behavior as a function of mutual orientations and separation of the domain walls, thus affecting the domain wall dynamics. Then we consider how the theory should be modified in the case of a magnetized quantum ring. In this case the situation is more complicated because the vortex and onion magnetization states in the ring are not truly ferromagnetic.