ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Using plasma-assisted molecular beam epitaxy, films of iron oxide cubic spinel phases have been prepared on single crystal MgO (100). Preparation was by deposition of Fe from an elemental e− gun in a reactive oxygen plasma (primarily O+) from an ECR source. Sample stoichiometry during synthesis was controlled by variation of growth parameters, including substrate temperature, oxygen flux, plasma power, and deposition rate. We present the results of structural and magnetic studies of these materials using electron and x-ray diffraction, as well as SQUID magnetometry. Lattice spacing, saturation magnetization, and magnetic anisotropy all provide strong evidence that the variation of growth parameters does indeed produce a range of "cubic'' defect spinel structures ranging from Fe3O4 to one approximating γ-Fe2O3. Both structural and magnetic probes indicate that strong ordering changes occur in these systems as they are cooled through the ∼119 K Verwey transition. The behavior of the Verwey transition as a function of growth parameters indicates that Fe vacancies in these defect spinels have a profound effect on the structural distortion related to the Verwey transition. Epitaxial strain due to lattice mismatch further contributes to structural distortion, and thus to the Verwey transition. The relative contributions of these stoichiometric variations and epitaxial strain on the Verwey transition will be discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.355482
