  Coexisting phases of magnetic skyrmions and antiskyrmions have proposed to
exhibit a variety of fascinating properties, owing to interactions between
them. The recent discovery of the coexisting phase in a Heusler material could
offer a platform for skyrmion-antiskyrmion-based spintronics. Here we report
Lorentz electron microscopy experiments and micromagnetic simulations in a
similar Heusler material, Mn$_{1.3}$Pt$_{1.0}$Pd$_{0.1}$Sn. Around $B_c \sim$
420$\,$mT, we find a stochastic reversible transformation and a room
temperature coexisting phase of elliptical skyrmions and square-shaped
antiskyrmions. The closeness of the energy competition is sensitive to the
exchange stiffness constants and sample thickness. Furthermore, we reveal
isotropic long-range repulsive interaction between the skyrmions and
antiskyrmions regardless of their shapes and the skyrmion helicities, in stark
contrast to conventional thought of angle- and helicity-dependent short-range
pairwise interactions. The observed interaction possibly results from the
topological protection against the intrusion of magnetic flux density coming
from skyrmions (antiskyrmions) into antiskyrmions (skyrmions). Our results
provide new insight into interacting skyrmions and antiskyrmions and a guide
for developing skyrmion-antiskyrmion-based spintronics.
