We merge advanced ab initio schemes (standard density functional theory,
hybrid functionals and the GW approximation) with model Hamiltonian approaches
(tight-binding and Heisenberg Hamiltonian) to study the evolution of the
electronic, magnetic and dielectric properties of the manganite family RMnO3 (R
= La, Pr, Nd, Sm, Eu and Gd). The link between first principles and
tight-binding is established by downfolding the physically relevant subset of
3d bands with e_g character by means of maximally localized Wannier functions
(MLWFs) using the VASP2WANNIER90 interface. The MLWFs are then used to
construct a tight-binding Hamiltonian. The dispersion of the TB e_g bands at
all levels are found to match closely the MLWFs. We provide a complete set of
TB parameters which can serve as guidance for the interpretation of future
studies based on many-body Hamiltonian approaches. In particular, we find that
the Hund's rule coupling strength, the Jahn-Teller coupling strength, and the
Hubbard interaction parameter U remain nearly constant for all the members of
the RMnO3 series, whereas the nearest neighbor hopping amplitudes show a
monotonic attenuation as expected from the trend of the tolerance factor.
Magnetic exchange interactions, computed by mapping a large set of hybrid
functional total energies onto an Heisenberg Hamiltonian, clarify the origin of
the A-type magnetic ordering observed in the early rare-earth manganite series
as arising from a net negative out-of-plane interaction energy. The obtained
exchange parameters are used to estimate the Neel temperature by means of Monte
Carlo simulations. The resulting data capture well the monotonic decrease of
the ordering temperature down the R series, in agreement with experiments.Comment: 13 pages, 9 figures, 3 table