Domain-wall dynamics in translationally noninvariant nanowires: theory and applications

TL;DR

This paper develops a generalized theoretical framework for domain-wall dynamics in nonuniform ferromagnetic nanowires, demonstrating applications to energy-efficient magnetic memory devices with optimized switching protocols.

Contribution

It introduces a universal set of equations for domain-wall motion in noninvariant wires, applicable regardless of specific model details.

Findings

Derived general equations of motion for domain walls in nonuniform wires

Analyzed switching dynamics in an hourglass-shaped nanostrip

Showed potential for $10^5$ times energy efficiency improvement

Abstract

We generalize domain-wall dynamics to the case of translationally noninvariant ferromagnetic nanowires. The obtained equations of motion make the description of the domain-wall propagation more realistic by accounting for the variations along the wire, such as disorder or change in the wire shape. We show that the effective equations of motion are very general and do not depend on the model details. As an example of their use, we consider an hourglass-shaped nanostrip in detail. A transverse domain wall is trapped in the middle and has two stable magnetization directions. We study the switching between the two directions by short current pulses. We obtain the exact time dependence of the current pulses required to switch the magnetization with the minimal Ohmic losses per switching. Furthermore, we find how the Ohmic losses per switching depend on the switching time for the optimal current pulse. As a result, we show that as a magnetic memory this nanodevice can be $10^5$ times more energy efficient than the best modern devices.