Dresden 2009 – wissenschaftliches Programm

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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

Dienstag, 24. März 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 Braden¹ — ¹Universität 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).