  Ferromagnetic topological semimetals due to their band topology co-existing
with intrinsic magnetization exerted important influences on early study of
topological fermions. However, they have not been observed in experiments up to
now. In this work, we propose that rutile CrO$_{2}$, a widely used
half-metallic ferromagnetic material in magnetic recording taps, exhibits
unexpected ferromagnetic topological features. Using first-principles
calculations and symmetry analysis, we reveal that rutile CrO$_2$ hosts the
triple nodal points in the absence of spin orbital coupling (SOC). By taking
into account of SOC, each triple nodal point splits into two Weyl points, which
are located on the magnetic axis with four-fold rotational symmetry. Notably,
the Fermi arcs and accompanying quasiparticle interference patterns are clearly
visible, which facilitate experimental observations. In addition, we find that
another experimentally synthesized CrO$_{2}$ in CaCl$_2$ structure, also hosts
the topologically nontrivial ferromagnetic phase. Our findings substantially
advance the experimental realization of ferromagnetic topological semimetals.
More importantly, room-temperature time-reversal-breaking Weyl fermions in
CrO$_{2}$ may result in promising applications related to the topological
phenomena in industry.
