Regensburg 2007 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 20: Poster session
MM 20.38: Poster
Dienstag, 27. März 2007, 14:45–18:00, Poster C
Optical properties of neodymiumhydride from FIR to VUV — •Stefan Weber and Joachim Schoenes — Institut für Physik der Kondensierten Materie, TU Braunschweig
Many rare-earth metals show a metal to insulator transition when they are loaded with hydrogen. The dramatic changes in the optical and electronical properties are accompanied by a transition from an antiferromagnetic metal to a ferromagnetic semiconductor in the particular material system of neodymium.
Thin films of Nd have been grown onto different substrates by molecular beam epitaxy. They need a functional cap layer of Nb and Pd on top in order to allow hydrogen loading and to prevent the samples from corrosion in ambient air.
Temperature dependent transmission and reflection measurements have been performed with a FT-IR-spectrometer in the energy range of 5meV to 1eV. The structures in the spectra can unambiguously be assigned to hydrogen vibrations using the isotope effect which is a shift of the phonon frequencies by a factor of √2 by loading the samples with hydrogen or deuterium, respectively. The measurement of the optical properties of NdHx is supplemented by UV/Vis-spectrometry which determines the optical band gap of the semiconductor. VUV ellipsometry in the energy range up to 10eV has been performed using synchrotron radiation at BESSY II which yields the pseudodielectric function. Simulating the thin film spectra with a multilayer model reveals the optical properties of NdHx.