Domain wall propagation in Permalloy nanowires with a thickness gradient

TL;DR

This study investigates how a thickness gradient in Permalloy nanowires influences domain wall nucleation and propagation, revealing a metastability regime and domain wall type transformations through experiments and simulations.

Contribution

It introduces the effect of a thickness gradient on domain wall behavior in Permalloy nanowires, combining experimental fabrication, hysteresis measurements, and micromagnetic simulations.

Findings

Identification of a metastability regime in nanowires.

Observation of domain wall type transformation.

Comparison of experimental results with micromagnetic simulations.

Abstract

The domain wall nucleation and motion processes in Permalloy nanowires with a thickness gradient along the nanowire axis have been studied. Nanowires with widths, w = 250 nm to 3 um and a base thickness of t = 10 nm were fabricated by electron-beam lithography. The magnetization hysteresis loops measured on individual nanowires are compared to corresponding nanowires without a thickness gradient. The Hc vs. t/w curves of wires with and without a thickness gradient are discussed and compared to micromagnetic simulations. We find a metastability regime at values of w, where a transformation from transverse to vortex domain wall type is expected.