Synthesis and Characterization of multiferroic epitaxial Perovskite Oxide thin Film Heterostructures - Implications of [111] epitaxy of STO, BTO and LSMO

Abstract

A surge of research on perovskite oxide heterostructures has been excited by the invention of deposition techniques, such as pulsed laser deposition and the need for novel solutions in order to sustain Moores rate for computing technology. The substitution of lanthanum by a certain amount of strontium in lanthanum manganite has shown to transform the antiferromagnetic mixed valence perovskite manganite into a high temperature ferromagnet with properties requisite for spintronic applications. The material properties may be influenced by heteroepitaxial interfaces, which leaves room for optimization. Little information is accessible he heteroepitaxial combination of lanthanum strontium manganite with barium titanate and strontium titanate along crystallographic \hkl[111] directions.

The scope of this project comprises an optimization of the deposition of barium titanate on strontium titanate substrates on \hkl(111) planes, heteroepitaxy of barium titanate and lanthanum strontium manganite on the same type of substrates, magnetic measurements performed on these heterostructures and an attempt to improve this behavior by subsequent annealing in oxygen ambiance. An indication of range of temperature for optimal deposition of barium titanate is observed. Optimal parameters are taken from mosaic spread through x-ray analysis and surface smoothness through atomic force microscopy. The manganite heteroepitaxy is successfully performed resulting in four unique structures with divergent magnetic behavior and ferromagnetic responses at room temperature and above. The post-deposition anneal does not show significant improvement for ferromagnetic behavior.