  The development of skyrmionic devices requires a suitable tuning of material
parameters in order to stabilize skyrmions and control their density. It has
been demonstrated recently that different skyrmion types can be simultaneously
stabilized at room temperature in heterostructures involving ferromagnets,
ferrimagnets and heavy metals, offering a new platform of coding binary
information in the type of skyrmion instead of the presence/absence of
skyrmions. Here, we tune the energy landscape of the two skyrmion types in such
heterostructures by engineering the geometrical and material parameters of the
individual layers. We find that a fine adjustment of the ferromagnetic layer
thickness and thus its magnetic anisotropy, allows the trilayer system to
support either one of the skyrmion types or the coexistence of both and with
varying densities.
