  Transition-metal compounds represent a fascinating playground for exploring
the intricate relationship between structural distortions, electronic
properties, and magnetic behaviour, holding significant promise for
technological advancements. Among these compounds, YBaCo$_4$O$_{7}$ (Y114) is
attractive due to its manifestation of a ferrimagnetic component at low
temperature intertwined with distortion effect due to the charge
disproportionation on Co ions, exerting profound impact on its magnetic
properties. In this perspective paper, we study the structural and magnetic
intricacies of the Y114 crystal. Traditionally, the investigation of such
materials has relied heavily on computational modelling using
density-functional theory (DFT) with the on-site Coulomb interaction correction
$U$ (DFT+$U$) based on the Hubbard model (sometimes including Hund's exchange
coupling parameter $J$, DFT+$U$+$J$) to unravel their complexities. Herein, we
analysed the spurious effects of magnetic-moment delocalisation and spillover
to non-magnetic ions in the lattice on electronic structure and magnetic
properties of Y114. To overcome this problem we have applied constrained DFT
(cDFT) based on the potential self-consistency approach, and comprehensively
explore the Y114 crystal's characteristics in its ferrimagnetic order. We find
that cDFT yields magnetic moments of Co ions much closer to the experimental
values than LDA+$U$+$J$ with the parameters $U$ and $J$ fitted to reproduce
experimental lattice constants. cDFT allows for an accurate prediction of
magnetic properties using oxidation states of magnetic ions as well-defined
parameters. Through this perspective, we not only enhance our understanding of
the magnetic interactions in Y114 crystal, but also pave the way for future
investigations into magnetic materials.
