Exotic Spin Order due to Orbital Fluctuations
W. Brzezickia, J. Dziarmagaa and A.M. Oleśa,b
aMarian Smoluchowski Institute of Physics, Jagiellonian University, W.S. Reymonta 4, PL-30-059 Kraków, Poland
bMax-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
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We investigate the phase diagrams of the spin-orbital d9 Kugel-Khomskii model for increasing system dimensionality: from the square lattice monolayer, via the bilayer to the cubic lattice. In each case we find strong competition between different types of spin and orbital order, with entangled spin-orbital phases at the crossover from antiferromagnetic to ferromagnetic correlations in the intermediate regime of Hund's exchange. These phases have various types of exotic spin order and are stabilized by effective interactions of longer range which follow from enhanced spin-orbital fluctuations. We find that orbital order is in general more robust while spin order melts first under increasing temperature, as observed in several experiments for spin-orbital systems.

DOI: 10.12693/APhysPolA.126.A-40
PACS numbers: 75.10.Jm, 03.65.Ud, 64.70.Tg, 75.25.Dk