  The evolution of chiral spin structures is studied in ferrimagnet
Ta/Ir/Fe/GdFeCo/Pt multilayers as a function of temperature using scanning
electron microscopy with polarization analysis (SEMPA). The GdFeCo ferrimagnet
exhibits pure right-hand N\'eel-type domain wall (DW) spin textures over a
large temperature range. This indicates the presence of a negative
Dzyaloshinskii-Moriya interaction (DMI) that can originate from both the top
Fe/Pt and the Co/Pt interfaces. From measurements of the DW width, as well as
complementary magnetic characterization, the exchange stiffness as a function
of temperature is ascertained. The exchange stiffness is surprisingly mostly
constant, which is explained by theoretical predictions. Beyond single
skyrmions, we find by direct imaging a pure N\'eel-type skyrmionium, which due
to the absence of a skyrmion Hall angle is a promising topological spin
structure to enable high impact potential applications in the next generation
of spintronic devices.
