FORUM DPMC – Electronic properties of SmNiO3 and NdNiO3 thin films; Evidence of inequivalent nickel sites in Rare-Earth nickelates using spectroscopic by Sara Catalano, Julien Ruppen

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Date(s) - 03/06/2014
13 h 00 min - 15 h 00 min

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Auditoire Stückelberg, 24 quai Ernest-Ansermet

This seminar will be presented by Sara Catalano and Julien Ruppen from the group prof. Triscone and the group of prof.Van der Marel

1. Perovskite nickelates (R-NiO3, R=Rare Earth) exhibit a textbook example of Metal to Insulator transition, involving a strong interplay of charge, magnetic and structural degrees of freedom. The synthesis of bulk materials being limited to polycrystalline samples, epitaxial thin films of extreme quality optimally reproduce the fundamental physics of nickelates and also allow for the emerging of novel quantum properties as the nickelate layer is confined by reducing its thickness or by embedding it in properly designed heterostructures. In the present talk, the electronic phases displayed by high quality NdNiO3 and SmNiO3 thin films will be described, focusing on the impact of the applied epitaxial constraints on these systems. Further, recent Resonant Inelastic X-ray Scattering (RIXS) measurements on NdNiO3 films will be presented, their analysis revealing key information on the electronic ground state configuration of the nickelates.

2. We used spectroscopic ellipsometry to investigate the phase diagram of nickelate thin layers in the range 0.5 meV to 5eV. The Neodymium Nickelate (NNO) is compared to Samarium Nickelate (SNO) which has two distincts transitions in the bulk. Optical conductivity shows for both compounds signs of valence mixture when entering the insulating phase as well as a subtle spectral weight redistribution when spins order.

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