Berlin 2018 – scientific programme
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MA: Fachverband Magnetismus
MA 52: Poster II
MA 52.56: Poster
Thursday, March 15, 2018, 15:00–18:00, Poster C
Band-gap evolution of thin ferromagnetic europium-oxide films at low temperatures — •Marcel Ney1, Günther Prinz1, Patrick Lömker2, Martina Müller2,3, and Axel Lorke1 — 1Faculty of Physics, Universität Duisburg-Essen, D-47048 Duisburg — 2Peter Grünberg Institut, Forschungszentrum Jülich GmbH, D-52428 Jülich — 3Faculty of Physics, TU Dortmund, D-44227 Dortmund
In spintronic research, materials with magnetic properties, which can be used as spin filters, are of particular interest. We are investigating EuO with a Curie temperature of TC=69K, as one candidate for this application. It is of interest to study how the ferromagnetic phase transition below TC affects the optical band-gap of EuO.
Thin EuO-layers were grown by molecular-beam-epitaxy on YSZ substrates, with different thicknesses. A FTIR-spectrometer, was used to measure the transmission through the EuO thin films to determine the optical band-gap energy.
The EuO-films with thicknesses between 5nm and 30nm were investigated in a range of 293K down to 25K. At room temperature, we observe a dependence of the band-gap on the layer thickness due to the quantum confinement effect. When cooling a 20nm layer below the Curie temperature, we observe a red shift of the optical band-gap of about Ea=0.27± 0.02eV. This energy shift is in good agreement with theoretical and experimental values for EuO exchange splitting effects. For thin films first measurements show a different temperature dependent behavior upon cooling below TC, which indicates that quantum size effects will influence the magnetic ordering of the material.