  Capturing the non-collinear magnetic ground state of the spinel vanadates
AV$_2$O$_4$ (A= Mn, Fe and Co) remains an outstanding challenge for
state-of-the-art ab-initio methods. We demonstrate that both the non-collinear
spin texture, as well as the magnitude of local moments, are captured by a
single value of the on-site Hubbard $U$ of 2.7~eV in conjunction with the local
spin density approximation (LSDA+$U$), provided the source term (i.e., magnetic
monopole term) is removed from the exchange-correlation magnetic field ${\bf
B}_{XC}$. We further demonstrate that the magnetic monopole structure in ${\bf
B}_{XC}$ is highly sensitive to the value of $U$, to the extent that the
interplay between on-site localization and local moment magnitude is
qualitatively different depending on whether the source term is removed or not.
This suggests that in treating strongly correlated magnetic materials within
the LSDA+$U$ formalism, subtraction of the unphysical magnetic monopole term
from the exchange-correlation magnetic field is essential to correctly treat
the magnetic ground state.
