Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65
MA 20.61: Poster
Montag, 7. März 2005, 14:00–18:00, Poster TU C
Orbital polarons versus itinerant eg electrons in doped manganites — •Maria Daghofer1, Andrzej Oleś2, and Wolfgang von der Linden1 — 1Institute for Theoretical and Computational Physics, TU Graz, Austria — 2Marian Smoluchowski Institute of Physics, Jagellonian University, Kraków, Poland
We study an effective one-dimensional (1D) orbital t-J model derived for strongly correlated eg electrons in doped manganites. At half doping, an FM chain with alternating orbital order competes with an orbitally polarized AFM chain. Alternating orbitals are supported by an alternating Jahn-Teller potential, while spin AFM is favored by the t2g superexchange. Because the FM and AFM states have very similar energy, small changes in the concerning parameters can have a large impact and can switch the system from one scenario to the other.
At finite doping, the kinetic energy favors both ferromagnetism and orbital polarization. The transition from the undoped chain with alternating spin or orbital order to the polarized chain at high doping is investigated by examining a variety of observables. Upon doping, orbital polarons enter the FM chain with alternating orbital order, and spin polarons are found for the AFM chain. Phase separation into regions of high and low carrier density is only observed for FM chains without Jahn-Teller distortions.
The Jahn-Teller potential is found to hinder the transition to the orbitally polarized state, but at least for small potentials, it does not substantially decrease the kinetic energy once this transition has occurred.