Local control of magnetic damping in ferromagnetic/non-magnetic bilayers by interfacial intermixing induced by focused ion-beam irradiation

Abstract

The influence of interfacial intermixing on the picosecond magnetization dynamics of ferromagnetic/non-magnetic thin-film bilayers was studied. Low-dose focused-ion-beam irradiation was used to induce intermixing across the interface between a 10 nm Ni81Fe19 layer and a 2–3 nm capping layer of either Au or Cr. Time-resolved magneto-optical Kerr effect was used to study magnetization dynamics as a function of ion-beam dose. With an Au cap, the damping of the un-irradiated bilayer was comparable with native Ni81Fe19 and increased with increasing ion dose. In contrast, for Ni81Fe19/Cr the damping was higher than that for native Ni81Fe19, but the damping decreased with increasing dose. We gratefully acknowledge financial support from Department of Science and Technology, Government of India, and the British Council for the DST-UKIERI joint project, Grant No. DST/INT/UK/P-44/2012. D.A. also acknowledges EPSRC funding (EP/G010897/1 and Durham Strategic Partnership Award) and UK CRG XMaS beam-line at ESRF.