  Tailoring and controlling magnetic properties is an important factor for
materials design. Here, we present a case study for Ni-based Heusler compounds
of the type Ni$_2$YZ with Y = Mn, Fe, Co and Z = B, Al, Ga, In, Si, Ge, Sn
based on first principles electronic structure calculations. These compounds
are interesting since the materials properties can be quite easily tuned by
composition and many of them possess a non-cubic ground state being a
prerequisite for a finite magnetocrystalline anisotropy (MAE). We discuss
systematically the influence of doping at the Y and Z sublattice as well of
lattice deformation on the MAE. We show that in case of Ni$_2$CoZ the phase
stability and the MAE can be improved using quaternary systems with elements
from group 13 and 14 on the Z sublattice whereas changing the Y sublattice
occupation by adding Fe does not lead to an increase of the MAE. Furthermore,
we studied the influence of the lattice ratio on the MAE. Showing that small
deviations can lead to a doubling of the MAE as in case of Ni$_2$FeGe. Even
though we demonstrate this for a limited set of systems the findings may carry
over to other related systems.
