  The orbital magnetic moment is usually associated with the relativistic
spin-orbit interaction, but recently it has been shown that noncollinear
magnetic structures can also be its driving force. This is important not only
for magnetic skyrmions, but also for other noncollinear structures, either
bulk-like or at the nanoscale, with consequences regarding their experimental
detection. In this work we present a minimal model that contains the effects of
both the relativistic spin-orbit interaction and of magnetic noncollinearity on
the orbital magnetism. A hierarchy of models is discussed in a step-by-step
fashion, highlighting the role of time-reversal symmetry breaking for
translational and spin and orbital angular motions. Couplings of spin-orbit and
orbit-orbit type are identified as arising from the magnetic noncollinearity.
We recover the atomic contribution to the orbital magnetic moment, and a
nonlocal one due to the presence of circulating bound currents, exploring
different balances between the kinetic energy, the spin exchange interaction,
and the relativistic spin-orbit interaction. The connection to the scalar spin
chirality is examined. The orbital magnetism driven by magnetic noncollinearity
is mostly unexplored, and the presented model contributes to laying its
groundwork.
