Giant supermagnonic Bloch point velocities by jet propulsion effect in cylindrical ferromagnetic nanowires

TL;DR

This paper demonstrates that cylindrical ferromagnetic nanowires can achieve Bloch point domain wall velocities exceeding the magnonic limit, due to a jet propulsion effect caused by the conical shape of the domain wall.

Contribution

It reveals that the magnonic velocity limit can be surpassed in cylindrical nanowires with high magnetization, introducing a jet propulsion mechanism for high-speed domain wall motion.

Findings

Bloch point velocities up to 14 km/s, surpassing the magnonic limit.

The conical shape of the domain wall causes elongation and acceleration.

Jet propulsion effect significantly enhances domain wall velocities.

Abstract

Achieving high velocities of magnetic domain walls is a crucial factor for their use as information carriers in modern nanoelectronic applications. In nanomagnetism and spintronics, these velocities are often limited either by internal domain wall instabilities, known as the Walker breakdown phenomenon, or by spin wave emission, known as the magnonic regime. In the rigid domain wall model, the maximum magnon velocity acts as an effective "speed of light", providing a relativistic analogy for the domain wall speed limitation. Cylindrical magnetic nanowires are an example of systems with the absence of the Walker breakdown phenomenon. Here we demonstrate that in cylindrical nanowires with high magnetization such as Iron, also the magnonic limit could be outstandingly surpassed. Our numerical modelling shows the Bloch point domain wall velocities as high as 14 km/s, well above the magnonic limit estimated in the interval 1.7-2.0 km/s. The key ingredient is the conical shape of the domain wall which elongates and breaks during the dynamics, leading to domain wall acceleration due to the jet propulsion effect. This effect will be very important for three-dimensional spintronic networks based on cylindrical magnetic nanowires.