Quantum effects in the Hall resistivity of CMR oxides

This forum paper reviews recent work by the author and colleagues on an unforeseen consequence of the constraint that charge carriers follow the local spin texture. As a result of the double-exchange mechanism in the presence of strong Hund's-rule coupling, the constraint produces a universal Berry-phase contribution to the anomalous Hall effect in the vicinity of the ferromagnetic transition. Such effects are apparent in both 3D and layered manganites and are expected in other double-exchange systems.