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

TL;DR

This study investigates how ion irradiation affects the structural, chemical, and magnetic properties of Fe-Fe oxide nanocluster films, revealing that initial composition influences irradiation outcomes and magnetic stability.

Contribution

It provides new insights into the effects of ion irradiation on Fe-based nanocluster films, highlighting the role of initial nanostructure and chemistry in their stability.

Findings

Ion irradiation increases particle size in nanocluster films.

Oxide shells are reduced to lower valent Fe species upon irradiation.

Saturation magnetization decreases slightly after irradiation.

Abstract

A cluster deposition method was used to produce films of loosely aggregated nanoclusters (NC) of Fe core-Fe3O4 shell or fully oxidized Fe3O4. Films of these NC on Si(100) or MgO(100)/Fe3O4(100) were irradiated to 10^16 Si2+/cm2 near room temperature using an ion accelerator. Ion irradiation creates structural change in the NC film with corresponding chemical and magnetic changes which depend on the initial oxidation state of the cluster. Films were characterized using magnetometry (hysteresis, first order reversal curves), microscopy (transmission electron, helium ion), and x-ray diffraction. In all cases, the particle sizes increased due to ion irradiation, and when a core of Fe is present, irradiation reduces the oxide shells to lower valent Fe species. These results show that ion irradiated behavior of the nanocluster films depends strongly on the initial nanostructure and chemistry, but in general saturation magnetization decreases slightly.