Ion-beam induced fcc-bcc transition in ultrathin Fe films for ferromagnetic patterning

Abstract

Ar + ion irradiation is used to induce a structural change from fcc to bcc in a 1.5nm thick Fe film epitaxially grown on a Cu(100) crystal. Scanning tunneling microscopy and low-energy electron diffraction show the nucleation of bcc nanocrystals, which grow with increasing ion dose. As a consequence of the structural change, the irradiated iron film becomes strongly ferromagnetic at room temperature. We present a model for the process of the transformation and demonstrate writing a magnetic pattern at the 100nm scale by ion-beam projection lithography.