Growth and electronic and magnetic structure of iron oxide films on Pt(111)

TL;DR

This study investigates the growth, electronic, and magnetic properties of ultrathin iron oxide films on Pt(111), revealing size-dependent magnetic effects and unusual long-range order at room temperature due to structural modifications.

Contribution

It provides new insights into the growth mechanisms and magnetic behavior of ultrathin iron oxide films on platinum surfaces, highlighting effects not observed in bulk materials.

Findings

Superparamagnetic size effects in Fe3O4 below 2 nm

Unusual room temperature magnetic order in FeO films 3-10 monolayers thick

Structural modifications induce magnetic order not present in bulk w"ustite

Abstract

Ultrathin (111)-oriented polar iron oxide films were grown on a Pt(111) single crystal either by the reactive deposition of iron or oxidation of metallic iron monolayers. These films were characterized using low energy electron diffraction, scanning tunneling microscopy and conversion electron Mossbauer spectroscopy. The reactive deposition of Fe led to the island growth of Fe3O4, in which the electronic and magnetic properties of the bulk material were modulated by superparamagnetic size effects for thicknesses below 2 nm, revealing specific surface and interface features. In contrast, the oxide films with FeO stoichiometry, which could be stabilized as thick as 4 nm under special preparation conditions, had electronic and magnetic properties that were very different from their bulk counterpart, w\"ustite. Unusual long range magnetic order appeared at room temperature for thicknesses between three and ten monolayers, the appearance of which requires severe structural modification from the rock-salt structure.