Chaotic dynamics of magnetic domain walls in nanowires

TL;DR

This study numerically explores the nonlinear and chaotic dynamics of magnetic domain walls in nanowires with patterned pinning centers, revealing how different geometries and temperature affect chaos and depinning behavior.

Contribution

It provides a detailed phase diagram of domain wall dynamics in nanowires with specific pinning geometries, highlighting the effects of shape, material, and temperature on chaos.

Findings

T-shaped traps induce small chaotic regions in Nickel and larger ones in Permalloy.

Rectangular constrictions create larger chaotic regions with periodic windows.

Temperature increases chaos and facilitates thermal jumps between pinning sites.

Abstract

The nonlinear dynamics of a transverse domain wall (TDW) in Permalloy and Nickel nanostrips with two artificially patterned pinning centers is studied numerically up to rf frequencies. The phase diagram frequency - driving amplitude shows a rich variety of dynamical behaviors depending on the material parameters and the type and shape of pinning centers. We find that T-shaped traps (antinotches) create a classical double well Duffing potential that leads to a small chaotic region in the case of Nickel and a large one for Py. In contrast, the rectangular constrictions (notches) create an exponential potential that leads to larger chaotic regions interspersed with periodic windows for both Py and Ni. The influence of temperature manifests itself by enlarging the chaotic region and activating thermal jumps between the pinning sites while reducing the depinning field at low frequency in the notched strips.