Unconventional anomalous Hall, Nernst and thermal Hall responses in Fe₃GeTe₂

Here, we evaluate the anomalous Hall, Nernst and thermal responses of the layered ferromagnet Fe₃GeTe₂ as a function of the temperature and field orientation. The Hall conductivity s_xy^A increases and saturates to large values upon cooling, buy the anomalous Nernst S_xy^A is observed to change its sign below T = 50 K. This is surprising given that both quantities result from the texture of the Berry curvature near the Fermi level, with the change in the sign in S_xy^A suggesting a possible topological transition. In support of this assertion, the anomalous thermal Hall k_xy^A is seen to display an anomaly around T = 50 K, albeit its ratio with respect to s_xy^A indicates that the Wiedemann Franz law is satisfied by this compound. Surprisingly, one observes anomalous transport quantities also for electrical currents and thermal gradients applied along the magnetic field. Furthermore, for this field orientation the anomalous quantities do not follow the magnetization.