Engineered magnetization and exchange stiffness in direct-write Co-Fe nanoelements

TL;DR

This paper demonstrates a novel method to engineer magnetic properties of CoFe nanodisks using focused electron beam induced deposition and ion irradiation, enabling tunable magnetization and exchange stiffness for advanced spintronic applications.

Contribution

It introduces an in-situ compositional tuning technique for nanomagnets via FEBID and Ga ion irradiation, achieving a wide range of magnetic property control.

Findings

Achieved continuous variation of saturation magnetization from 720 to 1430 emu/cm³.

Demonstrated control over exchange stiffness in nanodisks.

Bridged the magnetic property gap between permalloy and CoFeB.

Abstract

Media with engineered magnetization are essential building blocks in superconductivity, magnetism and magnon spintronics. However, the established thin-film and lithographic techniques insufficiently suit the realization of planar components with on-demand-tailored magnetization in the lateral dimension. Here, we demonstrate the engineering of the magnetic properties of CoFe-based nanodisks fabricated by the mask-less technique of focused electron beam induced deposition (FEBID). The material composition in the nanodisks is tuned \emph{in-situ} via the e-beam waiting time in the FEBID process and their post-growth irradiation with Ga ions. The magnetization $M_s$ and exchange stiffness $A$ of the disks are deduced from perpendicular ferromagnetic resonance measurements. The achieved $M_s$ variation in the broad range from $720$ emu/cm$^3$ to $1430$ emu/cm$^3$ continuously bridges the gap between the $M_s$ values of such widely used magnonic materials as permalloy and CoFeB. The presented approach paves a way towards nanoscale 2D and 3D systems with controllable and space-varied magnetic properties.