Regensburg 2013 – scientific programme

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DS: Fachverband Dünne Schichten

DS 28: Layer Properties: Electrical, Optical, and Mechanical Properties

DS 28.2: Talk

Thursday, March 14, 2013, 09:45–10:00, H8

(Magneto)-optical investigations of NiFe₂O₄ and CoFe₂O₄ epitaxial thin films — •Cameliu Himcinschi¹, Ionela Vrejoiu^2,4, Georgeta Salvan³, Michael Fronk³, Andreas Talkenberger¹, Dietrich Zahn³, and Jens Kortus¹ — ¹TU Bergakademie Freiberg, Institute of Theoretical Physics, D-09596 Freiberg — ²Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle — ³TU Chemnitz, Semiconductor Physics, D-09107 Chemnitz — ⁴Max Planck Institute for Solid State Research, D-70569 Stuttgart

Nickel and cobalt ferrite epitaxial films were deposited on Nb doped SrTiO₃ by pulsed laser deposition. X-Ray diffraction and atomic force microscopy showed that the films have a good crystalline quality and smooth surfaces. A larger number of phonons was observed in the polarization dependent Raman spectra of the ferrite films than expected for the cubic spinel structures. This is explained by short range ordering of the Ni²⁺(or Co²⁺) and Fe³⁺ cations at the octahedral sites inducing a lowering of the symmetry. The dielectric functions for nickel and cobalt ferrites are determined from ellipsometry in the 0.73-5eV photon energy range. The absorption edge was analyzed using a bandgap model and the energies for the indirect and direct optical transitions were calculated. Magneto-optical Kerr effect spectroscopy in combination with spectroscopic ellipsometry allowed the off-diagonal elements of the dielectric tensor to be determined in the energy range from 1.7 eV to 5eV.