Hydrogenic control, reversible metal-insulator transition, room temperature ferromagnetism, La0.67Sr0.33MnO3, perovskite
Dynamic tuning of ion concentrations to create new functionalities in magnetoresistive La0.67Sr0.33MnO3 (LSMO) has attracted much attention. However, oxygen-vacancy-driven processes require extremely high temperatures (> 500oC) and take several days. Here, we found that by simply annealing platinum-dotted LSMO films in hydrogen and argon at the relatively low temperatures of 150–200oC for several minutes, we could achieve reversible changes in the resistivity over three orders of magnitude, with tailored ferromagnetic mag-netization. While oxygen-driven processes are usually accompanied by topotactic transitions between perovskite and brownmillerite, our reversible transition occurs in a perovskite. We suggest that this transition occurs due to electron-doping-induced modulation of double exchange interactions and/or lattice expansion, along with increases in the hydrogen concen-tration. Our findings offer high reproducibility, long-time stability, and linear multilevel ap-peal for ionotronic (ionic + electronic) applications.
Table Of Contents
Ⅰ. Introduction 1.1 Ionotronics: ionic control over materials’ functionalities 1 1.2 Lack of materials for ionic reversible control of both electrical and magnetic properties 1
Ⅱ. Experimental Methods 2.1 Deposition of La0.67Sr0.33MnO3 (LSMO) epitaxial films 4 2.2 Adsorption and desorption of hydrogen ions 4 2.3 Characterization of physical properties 5 2.4 Characterization of oxidation state 5 2.5 Characterization of structural properties 6
Ⅲ. Results and Discussion 3.1 Reversible metal-insulator transition by annealing ferromagnetic LSMO in hydrogen or argon at 200oC 7 3.2 Potential applications for ionotronic devices 12 3.3 Evidence of hydrogenic control 17 3.4 Hydrogen-driven electron doping 20 3.5 Hydrogen-driven reversible modulation of lattice volume in a perov-skite 21 3.6 Mechanism of hydrogen-driven metal-insulator transition in ferro-magnetic LSMO 24 3.7 Nanoscale observation of crystal structure in hydrogenated LSMO 25