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Dresden 2009 – scientific programme

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MA: Fachverband Magnetismus

MA 14: Poster Ib: Magnetic Materials (1-14); Micro Magnetism/Computational Mag. (15-17); Surface Magnetism (18-22); Spin Structures/Phase Transitions (23-25)

MA 14.25: Poster

Tuesday, March 24, 2009, 10:15–13:00, P1B

Magnetic correlations in half-doped manganates — •Holger Ulbrich1, Olaf Schumann1, Daniel Senff1, Yvan Sidis2, Klaudia Hradil3, Wolfgang Schmidt4, and Markus Braden11Universität zu Köln, Zülpicher Str. 77, 50937 Köln — 2Laboratoire Léon Brillouin, CE-Saclay — 3FRMII TU-München — 4Institut Laue-Langevin, 38042 Grenoble

The coupled ordering of charge orbital and spin degrees of freedom in the manganates constitutes a key element to understand the mechanism of colossal magneto resistivity, which consists in switching from the antiferromagnetically ordered insulating state into the ferromagnetic metallic phase. Starting with the half doped layered material La0.5Sr1.5MnO4 [1,2] we have analysed the magnon dispersion as well as the temperature dependence of the magnetic correlations in several compounds with a Mn4+:Mn3+ ratio close to half doping. In slightly over-doped La0.4Sr1.6MnO4 we find a coupling of incommensurate ordering of orbitals, charges and Mn3+ spins combined with commensurate ordering of Mn4+ spins. We further discus the magnetic correlations in Pr0.5Ca1.5MnO4 and in Nd0.5Sr0.5MnO3.

[1] D. Senff, F. Krüger, S. Scheidl, M. Benomar, Y. Sidis, F. Demmel, and M. Braden, Phys. Rev. Lett. 96, 257201 (2006) [2] D. Senff, O. Schumann, M. Benomar, M. Kriener, T. Lorenz, Y. Sidis, K. Habicht, P. Link, and M. Braden, Phys. Rev. B 77, 184413 (2008).

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