Anomalous Hall effect in SmN: Influence of orbital magnetism and 4 f -band conduction

We report measurements of the Hall effect in SmN thin films, spanning from ambient temperature to well inside the ferromagnetic state. The carrier concentrations of 0.8 – 4 × 1021 cm−3 show little temperature variation, signaling that at least one electron from the dominant nitrogen-vacancy dopant is unbound. The anomalous Hall effect in the ferromagnetic phase has a sign consistent with the known spin magnetic moment in SmN that is antiparallel to the magnetic field, in turn relating to an orbital dominance of the net magnetization. The AHE magnitude strongly supports a band structure with a heavy-fermion 4 f conduction band lying below the 5 d band.