Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties

摘要

A cluster deposition method was used to produce films of loosely aggregatednanoclusters (NC) of Fe core-Fe3O4 shell or fully oxidized Fe3O4. Films ofthese NC on Si(100) or MgO(100)/Fe3O4(100) were irradiated to 10^16 Si2+/cm2near room temperature using an ion accelerator. Ion irradiation createsstructural change in the NC film with corresponding chemical and magneticchanges which depend on the initial oxidation state of the cluster. Films werecharacterized using magnetometry (hysteresis, first order reversal curves),microscopy (transmission electron, helium ion), and x-ray diffraction. In allcases, the particle sizes increased due to ion irradiation, and when a core ofFe is present, irradiation reduces the oxide shells to lower valent Fe species.These results show that ion irradiated behavior of the nanocluster filmsdepends strongly on the initial nanostructure and chemistry, but in generalsaturation magnetization decreases slightly.