Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 25: Invited Talks Michels / Fuchs
MA 25.2: Hauptvortrag
Donnerstag, 29. März 2007, 14:30–15:00, H10
Strain induced ferromagnetic order in undoped LaCoO3 thin films — •Dirk Fuchs1, Christian Pinta1,2, Thorsten Schwarz1,2, Peter Scheiss1, Peter Nagel1, Stefan Schuppler1, Rudolf Schneider1, Michael Merz3, Georg Roth3, and Hilbert von Löhneysen1,2 — 1Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe — 2Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe — 3Institut für Kristallographie, Rheinisch-Westfälische Technische Hochschule Aachen, 52066 Aachen
Despite the well established nonmagnetic low spin (S = 0) ground state of LaCoO3 there are many publications reporting on the existence of either long- or short-range ferromagnetic order. For example, Yan et al.[1] have found a ferromagnetic component with a Tc = 85 K and have suggested a ferromagnetic coupling of surface cobalt atoms. In the presence of the conflicting results the origin of the observed ferromagnetism in LaCoO3 is still a challenging question and motivated this work. In order to scrutinize the proposed surface ferromagnetism by Yan et al. we have carried out experiments on thin films prepared by pulsed laser deposition which inherently show an extremely large surface/volume ratio. In contrast to polycrystalline LaCoO3 films which did not show ferromagnetism down to T = 5 K epitaxial films with the same surface/volume ratio showed clear ferromagnetic order at Tc = 85 K. We discuss this surprising result in terms of ferromagnetic order induced by epitaxial strain.
[1] J. Q. Yan et al., Phys. Rev. B 70, 014402, (2004).