Reversible Control of Physical Properties via an Oxygen‐Vacancy‐Driven Topotactic Transition in Epitaxial La0.7Sr0.3MnO3−δ Thin Films. Issue 7 (20th December 2018)

• Record Type: Journal Article
• Authors: Cao, Lei; Petracic, Oleg; Zakalek, Paul; Weber, Alexander; Rücker, Ulrich; Schubert, Jürgen; Koutsioubas, Alexandros; Mattauch, Stefan; Brückel, Thomas
• Is Part Of: Advanced materials. Volume 31:Issue 7(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-12-20
• Subjects: brownmillerite -- La0.7Sr0.3MnO3 films -- magnetism -- oxygen vacancy ordering -- polarized neutron reflectometry; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201806183
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: The vacancy distribution of oxygen and its dynamics directly affect the functional response of complex oxides and their potential applications. Dynamic control of the oxygen composition may provide the possibility to deterministically tune the physical properties and establish a comprehensive understanding of the structure–property relationship in such systems. Here, an oxygen‐vacancy‐induced topotactic transition from perovskite to brownmillerite and vice versa in epitaxial La0.7 Sr0.3 MnO3− δ thin films is identified by real‐time X‐ray diffraction. A novel intermediate phase with a noncentered crystal structure is observed for the first time during the topotactic phase conversion which indicates a distinctive transition route. Polarized neutron reflectometry confirms an oxygen‐deficient interfacial layer with drastically reduced nuclear scattering length density, further enabling a quantitative determination of the oxygen stoichiometry (La0.7 Sr0.3 MnO2.65 ) for the intermediate state. Associated physical properties of distinct topotactic phases (i.e., ferromagnetic metal and antiferromagnetic insulator) can be reversibly switched by an oxygen desorption/absorption cycling process. Importantly, a significant lowering of necessary conditions (temperatures below 100 °C and conversion time less than 30 min) for the oxygen reloading process is found. These results demonstrate the potential applications of defect engineering in the design of perovskite‐based functional materials. Abstract : Oxygen vacancy dynamics and ordering in La0.7 Sr0.3 MnO3− δ epitaxial films are identified by real‐time X‐ray diffraction. A novel intermediate phase with a noncentered crystal structure is observed. Huge changes of the physical properties (i.e., ferromagnetic metal and antiferromagnetic insulator) are found just by altering the oxygen content. Reverse switching among distinct topotactic phases is achieved at remarkably reduced temperatures.