Electronic Structure of La_0.7Sr_0.3MnO₃ Thin Films Grown by Pulsed Laser Deposition

The emergent properties that may arise at interfaces in heterostructures of dissimilar materials are of great interest in the pursuit of novel quantum materials for spintronics applications. One such example is the combination of a topological insulator and a magnetically ordered material, in which the magnetic order serves to break the time reversal symmetry of the topological insulator, creating a gap in the topological surface state. As components in such a system we consider thin films of the topological insulator Bi₂Te₃ and the ferromagnetic oxide La_0.7Sr_0.3MnO₃.<br/>As a step towards understanding the electronic structure of such a heterostructure, we must first understand the electronic structure of its constituents. Here, we consider epitaxial thin films of La_0.7Sr_0.3MnO₃ grown by pulsed laser deposition on (111)-oriented SrTiO₃ substrates. We first develop an in-vacuum methodology for surface preparation of the films by annealing in an oxygen atmosphere, enabling us to measure the electronic structure of films that have been exposed to air. The methodology is accompanied by X-ray photoelectron spectroscopy to study the surface stoichiometry, and low energy electron diffraction to study the surface crystallinity. The electronic band structure of the films is probed by soft X-ray angle-resolved photoemission spectroscopy using a synchrotron light source. Finally, the experimental results are compared to band structures obtained from density functional theory calculations.