Magnetic interactions in combination with nontrivial
band structures
can give rise to several exotic physical properties such as a large
anomalous Hall effect, the anomalous Nernst effect, and the topological
Hall effect (THE). Antiferromagnetic (AFM) materials exhibit the THE
due to the presence of nontrivial spin structures. EuCuAs crystallizes
in a hexagonal structure with an AFM ground state (Néel temperature
∼ 16 K). In this work, we observe a large topological Hall
resistivity of ∼7.4 μΩ-cm at 13 K which is significantly
higher than the giant topological Hall effect of Gd2PdSi3(∼3 μΩ-cm). Neutron diffraction experiments
reveal that the spins form a transverse conical structure during the
metamagnetic transition, resulting in the large THE. In addition,
by controlling the magnetic ordering structure of EuCuAs with an external
magnetic field, several fascinating topological states such as Dirac
and Weyl semimetals have been revealed. These results suggest the
possibility of spintronic devices based on antiferromagnets with tailored
noncoplanar spin configurations.