Kationen-Ordnung in ferri/ferromagnetischen perowskitischen Dünnfilmen

Abstract

A major obstacle to the applicability of oxide perovskites in electrical or spintronic applications is the size of the specific temperatures at which the physical phenomena such as ferromagnetism or high-temperature superconductivity can be observed. The physical properties of the perovskites show a dependence on the ordering of the various metal ions in multicomponent systems. The dependence results from the influence of the metal ions on the electron configuration and elastic tension within the material. One speaks in this context of the control of the filling and the width of electronic bands in the material by the choice of metal ions. The objective of this work was the preparation and characterization of artificially A-site ordered narrowband and broadband manganite thin films as well as B-site ordered ferro/ferrimagnetic double perovskite thin films. For the preparation of the thin films, the unconventional, vacuum-free, metallorganic aerosol deposition (MAD) was used. It was shown that various artificial or natural cation ordered perovskites can be grown with the MAD technology. The layer by layer A-site ordering results in manganites with modified electronic and magnetic properties, due to the modulation of the lattice strain and the electron occupation in the eg-band of manganese ions. In narrowband CMR manganites the PS and thus the CMR was effected by the ordering. For broadband CMR manganites a way was illustrated, which can lead to transition temperatures TC > 370K. In fully ordered ferromagnetic double perovskites, the influence and the presence of anti-phase boundaries was argued. The introduction of an active valence control enabled the preparation of half-metallic ferrimagnetic double perovskite thin films with the MAD technology.