Type-II Weyl nodes, flat bands, and evidence for a topological Hall-effect in the new ferromagnet FeCr${}_3$Te${}_6$

The interplay between linearly dispersing or Dirac-like, and flat electronic bands, for instance, in the kagome ferromagnets, has attracted attention due to a possible interplay between topology and electronic correlations. Here, we report the synthesis, structural, electrical, and magnetic properties of a single-crystalline ferromagnetic compound, namely Fe${}_{1\mathrm{/}3}$CrTe${}_2$ or FeCr${}_3$Te${}_6$, which crystallizes in the $P\bar{3}m1$ space group instead of the $I2\mathrm{/}m$ previously reported for FeCr${}_2$Te${}_4$. Electronic band structure calculations reveal type-II Dirac nodes and relatively flat bands near the Fermi level (${\epsilon }_F$). This compound shows onset Curie temperature $T_{\text{c}}\simeq 120$ K, followed by an additional ferromagnetic transition near $T_{\text{c2}}\sim 92.5$ K. Below $T_{\text{c}}$, FeCr${}_3$Te${}_6$ displays a pronounced anomalous Hall effect, as well as sizable coercive fields that exceed ${\mu }_{0}H=1$~T at low $T$s. However, a scaling analysis indicates that the anomalous Hall effect results from a significant intrinsic contribution, as expected from the calculations, but also from the extrinsic mechanism, i.e., scattering. The extrinsic contribution probably results from occupational disorder at the 1b Fe-site within the van der Waals gap of the CrTe${}_2$ host. We also observe evidence for a topological Hall component superimposed onto the overall Hall response, suggesting the presence of chiral spin textures akin to skyrmions in this centrosymmetric system. Their possible presence will require experimental confirmation.