Stability and capping of magnetite ultra-thin films

Abstract

Ultrathin films of Fe3O4 have been grown epitaxially on nearly lattice matched MgO(001). The stability of 4 nm thick films in ambient air and under annealing in an oxygen atmosphere at 200 °C has been studied. By magneto optical and Raman measurements, we can confirm the presence of the Fe3O4 phase and the formation of a maghemite top layer passivating the Fe3O4 thin film. In a second step, we are able to demonstrate that this top layer oxidation in ambient air can be prevented by a 2 nm thick magnesium ferrite passivation layer, while a thicker 20 nm MgO layer prevents oxidation even at elevated temperatures.

Impact of Strain and Morphology on Magnetic Properties of Fe3O4/NiO Bilayers Grown on Nb:SrTiO3(001) and MgO(001)

“…Consequently, very thin magnetite films tend to form maghemite at the surface after exposure to ambient air whereas thicker films seem to be more stable, as reported previously by Fleischer el al. [65]. Since in situ XPS and LEED measurements taken after preparation under UHV conditions showed no evidence for maghemite, a capping layer deposited directly after growth could prevent the possible oxidation process in the upper layers.…”

Electronic and magnetic structure of epitaxialFe3O4(001)/NiOheterostructures grown on MgO(001) and Nb-doped<

“…These samples exhibit a lack of Fe (001) that most of the maghemite formation occurs within days under ambient conditions and then slows significantly down in the time-frame of months. 60 As to the samples studied in this work, series S has been grown around 4 month, series SN and MN around 2-3 weeks prior to the XMCD experiments. The HAXPES experiments have been performed quite some time (over one year) after the thin film synthesis.…”

Raman spectroscopy indications of the Verwey transition in epitaxial Fe3O4(111) films on Pt(111) and Ru(0001)

“…In the case of magnetite film on platinum, the broad asymmetric peak at around 665 cm −1 could be fitted with three Lorentzian components, centered around 590, 665 (A 1g ) and 705 cm −1 . Regardless of the applied efforts, the peaks around 590 and 705 cm −1 indicated heterogeneous character of the iron oxide film, most probably related to the presence of maghemite phase (γ-Fe 2 O 3 ) [19] and Fe-OH groups. Initially, the film was in the form of magnetite only, however, exposure to ambient atmosphere and laser light could have promoted partial structural transformation [18].…”