Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 65: Poster Wednesday: Surface Structure, Epitaxy and Growth
O 65.7: Poster
Mittwoch, 3. April 2019, 17:45–20:00, Poster B1
Strain induced enhanced magnetization of ultrathin epitaxial NiFe2O4 films on SrTiO3(001) — •Jari Rodewald, Tabea Nordmann, and Joachim Wollschläger — Fachbereich Physik, Universität Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany
Ultrathin epitaxial ferrite films as NiFe2O4 are in the focus of spintronics owing to their semiconducting and ferrimagnetic properties. Thus, they are well-suited to be used as spin filters due to spin dependent tunneling barrier. Here, the homogeneity of the films is essential to form tunneling barriers. Furthermore, the cation ordering on the different sublattices of the inverse spinel structure determines the magnetic properties of the ferrite films which is crucial for the performance as a spin filter. Therefore, the formation of ferrite films has to be carefully controlled if high quality devices are aimed for.
Hence, in this work ultrathin NiFe2O4 films of different thicknesses are prepared via reactive molecular beam epitaxy (RMBE) on SrTiO3(001). Chemical composition and structural ordering at the surface are examined by x-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED), respectively. In order to investigate structural strain and ordering effects in the films, synchrotron radiation based grazing incidence x-ray diffraction (SR-GIXRD) experiments are performed. Magnetic properties are characterized via superconducting quantum interference device (SQUID) magnetometry, revealing unexpectedly high magnetic moments exceeding bulk values of up to four times for ultrathin films below 13 nm film thickness.