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

Abstract

Focused ion beam irradiation of metastable Fe78Ni22 thin films grown on Cu(001) substrates results in the localized transformation of the originally paramagnetic, face-centered-cubic continuous film into ferromagnetic patterns with body-centered-cubic structure. The focused ion beam scanning strategy can control the magnetic easy axis direction, producing eight crystallographic domains with distinct magnetic orientations. 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 → 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.