Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 19: Magnetic Half-metals and Oxides II
MA 19.2: Vortrag
Mittwoch, 24. März 2010, 15:30–15:45, H22
Optically induced electron conduction in Ce-doped lanthanum manganite films — •Andreas Thiessen1, Elke Beyreuther1, Stefan Grafström1, Kathrin Dörr2, and Lukas M. Eng1 — 1Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden — 2Institut für Metallische Werkstoffe, IFW Dresden, D-01171 Dresden
The question whether electron-doped mixed-valence manganites, such as La0.7Ce0.3MnO3, can be synthesized as single-phase compounds has been under debate for more than a decade. By now there is some agreement that it is possible to prepare high-quality single-phase material through epitaxial thin-film growth [1], but as-prepared films often suffer from overoxygenation and concomitant hole doping instead of the nominal and desired electron doping. Deoxygenation through post-deposition annealing in vacuum seems to solve this problem [2]. However, oxygen-reduced samples are insulating and do not exhibit a phase transition from a paramagnetic insulating to a ferromagnetic metallic phase any longer [3].
In the present work, we show that photoexcitation renders such thin films conductive and recovers the phase transition [3]. Possible mechanisms behind the pronounced photoconductivity effect are presented, especially the role of the SrTiO3 substrate. Several indications that strongly point towards an electron-doped nature of the illuminated films are discussed. [1] Mitra et al., J. Appl. Phys. 89, 524 (2001). [2] Beyreuther et al., Phys. Rev. B 73, 155425 (2006). [3] Beyreuther et al., Phys. Rev. B 80, 075106 (2009).