A complementary experimental study of epitaxial La0.67Sr0.33MnO3 to identify morphological and chemical disorder

TL;DR

This study investigates the surface and bulk properties of epitaxial La0.67Sr0.33MnO3 thin films, revealing chemical and morphological disorder that influences their electronic and magnetic behavior, using combined X-ray and microscopy techniques.

Contribution

It provides a detailed experimental analysis distinguishing surface and bulk characteristics of La0.67Sr0.33MnO3 films, highlighting the role of non-stoichiometry and electronic phase separation.

Findings

Surface non-stoichiometry in Sr and La detected

Oxygen vacancies accumulate at the surface

Electronic phase separation affects resistivity and magnetic states

Abstract

Gaining insight into the characteristics of epitaxial complex oxide films is essential to control the behavior of devices and catalytic processes. It is known that substrate induced strain, doping, and layer growth can affect the electronic and magnetic properties of the film's bulk. In this study, we demonstrate a clear distinction between the bulk and surface of thin films of La0.67Sr0.33MnO3 in terms of chemical composition, electronic disorder, and surface morphology. We employed a combined experimental approach of X-ray based characterization methods and scanning probe microscopy. X-ray diffraction and resonant X-ray reflectivity revealed surface non-stochiometry in the strontium and lanthanum, as well as an accumulation of oxygen vacancies. Scanning tunneling microscopy showed a staggered growth surface morphology accompanied by an electronic phase separation (EPS) related to this non-stochiometry. The EPS is likely responsible for the temperature-dependent resistivity transition and is a cause of a proposed mixed-phase ferromagnetic and paramagnetic state near room temperature in these thin films.