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O: Fachverband Oberflächenphysik

O 39: Oxide and Insulator Surfaces: Structure, Epitaxy and Growth II

O 39.2: Vortrag

Dienstag, 21. März 2017, 14:15–14:30, WIL C107

Epitaxy of ultrathin nickel ferrite films on MgO(001) — •Tabea Nordmann, Jari Rodewald, and Joachim Wollschläger — Fachbereich Physik, Universität Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany

Nickel ferrite (NiFe₂O₄) crystallizing in the inverse spinel structure is an interesting material for the use in magnetic devices due to its high magnetic permeability, its high Curie temperature of 865 K and its semiconducting property.
Studies on the growth of nickel ferrite by several deposition techniques have already been performed, but the deposition by reactive molecular beam epitaxy (RMBE) has just been studied rarely.
Hence, in this work ultrathin epitaxial films with different Ni/Fe ratios are deposited on MgO(001) via co-evaporation of nickel and iron in an oxygen atmosphere by using RMBE. The surface structure of the films is characterized by low-energy electron diffraction (LEED), while x-ray photoelectron spectroscopy (XPS) is executed to determine the film composition and the oxidation state of iron. Furthermore, x-ray diffraction (XRD) is performed in order to investigate the crystalline quality and the out-of-plane lattice constant of the films. Last, x-ray reflectivity (XRR) is measured to examine the film thickness.
The surfaces of all films with Ni/(Fe+Ni) contents between 7 % and 60 % are well ordered and the XRD results indicate a single crystalline layer. The XPS results reinforce the formation of nickel ferrite films with Ni contents of about 33 % where iron only exists in the Fe³⁺ oxidation state.