Ordering Phenomena in Rare-Earth Nickelate Heterostructures

This thesis presents an experimental study of ordering phenomena in rare-earth nickelate-based heterostructures by means of inelastic Raman light scattering and elastic resonant x-ray scattering (RXS). Further, it demonstrates that the amplitude ratio of magnetic moments at neighboring nickel sites can be accurately determined by RXS in combination with a correlated double cluster model, and controlled experimentally through structural pinning of the oxygen positions in the crystal lattice. The two key outcomes of the thesis are: (a) demonstrating full control over the charge/bond and spin order parameters in specifically designed praseodymium nickelate heterostructures and observation of a novel spin density wave phase in absence of the charge/bond order parameter, which confirms theoretical predictions of a spin density wave phase driven by spatial confinement of the conduction electrons; and (b) assessing the thickness-induced crossover between collinear and non-collinear spin structures in neodymium nickelate slabs, which is correctly predicted by drawing on density functional theory.

Nominated as an outstanding PhD thesis by the Max Planck Institute for Solid State Research, Stuttgart, Germany Offers a detailed description of the Raman measurement procedure to extract the phonon signal of exceptionally thin films of nickelate Adopts and uses the Raman measurement procedure to measure other thin transition metal oxide films and similar material systems Provides an extensive introduction to the basics of magnetic resonant elastic x-ray scattering and its applicability to determining complex magnetic structures in various material systems Includes supplementary material: sn.pub/extras

Contenu
Introduction: Transition Metal Oxides and their Heterostructures.- The Rare-earth Nickelates.- Experimental Techniques.- Tunable Order Parameters in Nickelate Heterostructures.- Complex Magnetic Order in Nickelate Slabs.