Stabilization of the oxygen concentration in La0.3Sr0.7CoO3−δ thin films by 3 nm thin LaAlO3 capping layer

Abstract

We prepared La0.3Sr0.7CoO3−δ thin films by pulsed laser deposition on (LaAlO3)0.3(Sr2TaAlO6)0.7 substrates with and without a protective LaAlO3 capping layer and investigated their structural and magnetic properties. We 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, δ. However, we show that already a 3 nm thin LaAlO3 capping layer can essentially conserve δ at room temperature, and it considerably slows down the formation of oxygen vacancies at elevated temperatures.