Precise control of crystallography and magnetism in focused-ion-beam transformed iron-nickel thin films

TL;DR

This paper demonstrates precise control over the crystallography and magnetism of Fe-Ni thin films using focused ion beam irradiation, enabling the creation of customizable magnetic nanostructures.

Contribution

It introduces a method to locally transform Fe-Ni films into ferromagnetic bcc structures with controllable magnetic anisotropy via focused ion beam scanning strategies.

Findings

Localized fcc to bcc transformation achieved

Magnetic easy axis orientation controlled by scanning strategy

Residual lattice strain influences magnetic anisotropy

Abstract

Focused ion beam irradiation of metastable Fe$_{78}$Ni$_{22}$ thin films grown on Cu(100) substrates results in the localized transformation of the originally paramagnetic, face-centered-cubic continuous film into ferromagnetic patterns with body-centered-cubic structure. The direction of the magnetic easy axis can be controlled by the focused ion beam scanning strategy, resulting in eight differently oriented crystallographic domains with different magnetic properties. We study the local crystallographic orientations of the transformed areas by electron backscatter diffraction and correlate these results with local magnetometry measurements. The observed magnetic anisotropy can be explained as a result of residual lattice strain after the fcc$\to$bcc transformation. These results extend the understanding of this material system and its transformation and allow for the patterning of high-quality magnetic nanostructures with precisely controlled magnetization landscapes.