Equilibrium Magnetic Properties in Magnetic Nanoscrews

TL;DR

This study uses micromagnetic simulations to explore how geometric parameters like curvature, torsion, and eccentricity influence the magnetic states and coercivity of ferromagnetic nanoscrews, revealing stable bistable configurations and potential for nanomagnetic applications.

Contribution

It introduces a detailed analysis of the impact of 3D geometric features on magnetic properties of nanoscrews, highlighting their bistability and enhanced coercivity.

Findings

Bistable magnetic behavior with vortex-domain-wall propagation.

Identification of four degenerate stable remanent states.

Coercive field increases with eccentricity, insensitive to torsion.

Abstract

We investigate the equilibrium magnetization in ferromagnetic nanoscrews (NSw) using micromagnetic simulations. These systems consist of elongated three-dimensional magnetic membranes with helicoidal geometry, combining curvature, torsion ($\mathrm{w}$), and eccentricity ($\epsilon$) along their length. We focus on the influence of these geometric parameters, together with membrane thickness and inner diameter, on remanent states and coercive fields. Our results, obtained over a broad range of eccentricities and torsions, reveal bistable magnetic behavior, with vortex-domain-wall propagation during magnetization reversal. We identify four degenerate configurations of a remarkably stable mixed remanent state. The coercive field is found to increase with eccentricity for structures with a major axis (larger inner diameter) approximately 30\% larger than the minor axis (smaller inner diameter), while remaining largely insensitive to variations in torsion. These findings are interpreted in terms of geometry-induced modifications of surface magnetostatic charges on the membrane mantle. Overall, our results demonstrate that nanoscrews exhibit robust bistability under systematic geometric deformation, together with enhanced coercivity, highlighting their potential for applications in three-dimensional nanomagnetism.