Dresden 2011 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 63: Poster II (Surface Magnetism/ Magnetic Imaging/ Topological Insulators/ Spin Structures and Magnetic Phase Transitions/ Graphene/ Magnetic Thin Films/ Magnetic Semiconductors/ Magnetic Half-metals and Oxides/ Spin-dependent Transport/ Spin Excitations and Spin Torque/ Spin Injection and Spin Currents in Heterostructures/ Spintronics/ Magnetic Storage and Applications)

MA 63.63: Poster

Freitag, 18. März 2011, 11:00–14:00, P2

Optical tuning of manganese valence and conductivity 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 preparation of epitaxial La_0.7Ce_0.3MnO₃ (LCeMO) films by pulsed-laser deposition is very challenging [1] – especially the oxygen partial pressure during deposition plays a crucial role to suppress the presence of a CeO₂ secondary phase [2]. As-prepared films typically suffer from overoxygenation and concomitant hole doping instead of the nominal and desired electron-doping. Post-deposition annealing however, using a reducing atmosphere seems to solve this problem [3]. These samples though are insulating and do not exhibit a phase transition from a paramagnetic insulating to a ferromagnetic metallic phase any more [4,5].

Here, we show the possibility to drive the Mn valence towards 2+ by photoexcitation, which renders LCeMO thin films conductive and recovers their phase transition [5]. Possible mechanisms behind the photoconductivity effect are presented, especially the role of the SrTiO₃ substrate and the influence of interface defect states.

[1] C. Mitra et al., J. Appl. Phys. 89, 524 (2001). [2] R. Werner et al., Phys. Rev. B 79, 054416 (2009). [3] E. Beyreuther et al., Phys. Rev. B 73, 155425 (2006). [4] D. J. Wang et al., Phys. Rev. B 73, 144403 (2006). [5] E. Beyreuther et al., Phys. Rev. B 80, 075106 (2009).