We examine magnon and orbiton behavior in localized 02 antibonding molecular π~* orbitals using aneffective Kugel-Khomskii Hamiltonian derived from a two-band Hubbard model with hopping parameterstaken from ab initio density-functional calculations. The considerable difference between intraband and inter-band hoppings leads to a strong coupling between the spin-wave dispersion and the orbital ground state,providing a straightforward way of experimentally determining the orbital ground state from the measuredmagnon dispersion. The near degeneracy of different orbital ordered states leads to stacking defects whichfurther modulate spin-fluctuation spectra. Proliferation of orbital domains disrupts long-range magnetic order,thus causing a significant reduction in the observed Neel temperature.
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