Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: CE: Metal-Insulator Transition 1

TT 33.4: Vortrag

Mittwoch, 16. März 2011, 11:15–11:30, HSZ 105

Magnetic order in Pr_1−xCa_1+xMnO₄ with x=2/3 — •H. Ulbrich¹, P. Steffens², O.J. Schumann¹, D. Lamago³, Y. Sidis³, and M. Braden¹ — ¹II. Phys. Institut, Universität zu Köln — ²ILL, Grenoble (France) — ³LLB, Saclay (France)

Stripe and checkerboard ordering of charges in several metal oxide compounds are thought to be linked to exotic behaviour such as high-temperature superconductivity and colossal magnetoresistivity (CMR). The coupling of charges, orbitals and spins (COS) are essential for the understanding of the CMR in the manganites. When the doping level deviates away from half-doping (x>0.5), significant controversies have arisen regarding the COS ordered structure [1,2]. Two different models have been proposed: The Bi-stripe model and the Wigner-crystal model. Investigations in La_0.42Sr_1.58MnO₄ exhibit an incommensurate stripe-like coupling of four order parameters: charges, orbitals and magnetic ordering of Mn³⁺ and Mn⁴⁺ spins [3].In order to decide between the Wigner-crystal model and the Bi-stripe model, we studied Pr_0.33Ca_1.67MnO₄ by elastic and inelastic neutron scattering. Our observations are in agreement with the Wigner-crystal model [4]. First studies of the magnon dispersion around the incommensurable magnetic satellites exhibit an ’hour-glass’ like behaviour similar to the spin dispersion in La_2−xBa_xCuO₄ at low doping [5].
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