Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 32: Postersession II: Spinstruct./Phase Trans. (1-10); Spinelectronics (11-15); Thin Films (16 - 36); Particles/Clusters (37-45); Multiferroics (46-54); Spindynamics/Spin Torque (55 - 76); Post Deadlines (77-79)

MA 32.30: Poster

Freitag, 29. Februar 2008, 11:15–14:00, Poster E

Recovery of the metal-insulator transition in electron-doped La_0.7Ce_0.3MnO_3−δ films by photoexcitation — •Andreas Thiessen¹, Elke Beyreuther¹, Stefan Grafström¹, Kathrin Dörr², and Lukas M. Eng¹ — ¹Institut für Angewandte Photophysik, TechnischeUniversität Dresden, D-01062 Dresden — ²Institut für Metallische Werkstoffe, IFW Dresden,Postfach 270116, D-01171 Dresden

The question whether electron-doped mixed-valence manganites, such as La_0.7Ce_0.3MnO₃, can be synthesized as single-phase compounds has been under debate for a decade. Meanwhile it has become clear that electron doping can indeed be achieved in epitaxial thin films [Mitra et al., JAP 89 (2001) 524]. However, as-prepared films often suffer from overoxygenation and concomitant hole doping, which can be overcome by deoxygenation through a post-deposition annealing procedure. Disappointingly, those reduced samples do not exhibit the typical metal-insulator transition (MIT) any longer [Wang et al., PRB 73 (2006) 144403].
In the present work, we show that the MIT of La_0.7Ce_0.3MnO_3−δ films can be recovered by exposition to visible light. Our films turn out to be highly photoconductive: Laser illumination at 514 nm with a power of 400 mW gave rise to a dramatic resistance drop of around seven orders of magnitude at 100 K as compared to the dark state, while illumination had no impact on the conductivity of an as-prepared reference film.