Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 34: Correlated Electrons: Spin Systems and Itinerant Magnets

TT 34.9: Vortrag

Freitag, 31. März 2006, 12:15–12:30, HSZ 301

Spin-Orbital Model for Layered Manganites — •Maria Daghofer¹ and Andrzej Oleś^1,2 — ¹Max Planck Institute for Solid State Research, Stuttgart, Germany — ²Jagellonian University Kraków, Poland

We present a spin-orbital t-J model for undoped and doped manganites at T=0 and at finite temperature. The model fully takes into account onsite Coulomb repulsion of these strongly correlated materials. We investigate it by use of Exact Diagonalization and Monte Carlo techniques.

With inclusion of a crystal field term, we obtain a realistic model for La_1−xSr_1+xMnO₄, showing a gradual change from predominantly out-of-plane (3z²−r²) to more in-plane (x²−y²) orbital occupation both with doping and with rising temperature. At higher doping, we obtain the CE-AF phase for x=0.5 as well as the C-AF phase observed in Nd_1−xSr_1+xMnO₄ at x>0.75.

For undoped bilayer clusters, we obtain for realistic parameter values the A-AF phase observed in three-dimensional compounds, with orbital correlations in accordance with experiment. At high doping, the model predicts the C-AF and G-phases as they are found in strongly doped La_2−2xSr_1+2xMn₂O₇.