Stabilization of the oxygen concentration in La$_{0.3}$Sr$_{0.7}$CoO$_{3-{\delta}}$ thin films by LaAlO$_3$ capping layer

TL;DR

This study demonstrates that a thin LaAlO$_3$ capping layer effectively stabilizes oxygen concentration in La$_{0.3}$Sr$_{0.7}$CoO$_{3-{eta}}$ thin films, preserving their magnetic properties under various conditions.

Contribution

The paper introduces the use of a LaAlO$_3$ capping layer to prevent oxygen vacancy formation in La$_{0.3}$Sr$_{0.7}$CoO$_{3-{eta}}$ thin films, enhancing their stability.

Findings

LaAlO$_3$ capping layer preserves oxygen content at room temperature.

Capping layer significantly slows oxygen vacancy formation at high temperatures.

Uncapped films show a decrease in Curie temperature after annealing and storage.

Abstract

We have grown La$_{0.3}$Sr$_{0.7}$CoO$_{3-{\delta}}$ thin films by pulsed laser deposition on (LaAlO$_3$)$_{0.3}$(Sr$_2$TaAlO$_3$)$_{0.7}$ substrates with and without a protective LaAlO$_3$ capping layer and investigated their structural and magnetic properties. We have observed that, in the uncapped films, the Curie temperature strongly decreased after annealing in helium atmosphere, and it significantly decreased even in samples stored for several weeks at room temperature. The decrease of the Currie temperature is caused by an increase of the concentration of oxygen vacancies, {\delta}. However, we show that already a 3 nm thin LaAlO$_3$ capping layer can essentially conserve {\delta} at room temperature, and it considerably slows down the formation of oxygen vacancies at elevated temperatures.