Effect of oxygen vacancies on structural, electrical and magnetic properties of La0.67Sr0.33CoO3 thin films. (5th January 2016)

• Record Type: Journal Article
• Authors: Liu, Bin; Liu, Guiju; Feng, Honglei; Wang, Chao; Yang, Huaiwen; Wang, Yiqian
• Is Part Of: Materials & design. Volume 89(2016)
• Page Start: 715
• Page End: 720
• Publication Date: 2016-01-05
• Subjects: La0.67Sr0.33CoO3 thin film -- Modulated structure -- Anisotropic chemical expansion -- Metal–insulator transition; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2015.10.034
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: The microstructure and chemical expansion of annealed and unannealed La0.67 Sr0.33 CoO3 (LSCO) thin films were investigated using high-resolution transmission electron microscopy (HRTEM). In both annealed and unannealed LSCO thin films, the modulated structure in La/Sr planes (A-sites) was discovered, which is ascribed to the cation ordering. However, the oxygen vacancy ordering induced modulated structure in Co–O planes (B-sites) only appeared in the vacuum-annealed LSCO thin films. In addition, the anisotropic chemical expansion was only observed in the vacuum-annealed LSCO films and the anisotropic elongation is associated with the modulated structures in the Co–O planes. What's more, the electrical and magnetic properties of the LSCO thin films were studied before and after annealing in the vacuum. The ferromagnetic-metallic LSCO thin films turned into a non-magnetic insulator after the annealing in vacuum, which is attributed to appearance of the oxygen vacancy ordering in the vacuum-annealed LSCO films. Graphical abstract: Typical HRTEM image (a) and simulated image (b) of the unannealed epitaxial LSCO film. The inset in (a) shows intensity profiles for the corresponding lines. The simulation conditions are Δ f = − 60.0 nm and t = 29.9 nm. Typical HRTEM image (c) and simulated image (d) of the vacuum-annealed epitaxial LSCO film. The inset in (c) shows intensity profiles for the corresponding lines; The simulation conditions are Δ f = − 73.0 nm and t = 16.8 nm. Highlights: In the vacuum-annealed LSCO film, the modulated structures in both A-sites and B-sites were observed. We found that the anisotropic chemical expansion was derived from the oxygen vacancies ordering. The LSCO thin films turned into a non-magnetic insulator after the annealing in vacuum.