Magnetotransport in manganites and the role of quantal phases: Theory and experiment

While low-temperature Hall resisitivity rho(xy) of La-2/3(Ca,Pb)(1/3)MnO3 s ingle crystals can be separated into ordinary (OHE) and anomalous (AHE) con tributions, no such decomposition is possible near the Curie temperature T- c. Rather, the rho(xy) data collapse to a single function of the reduced ma gnetization m = M/M-sat, with an extremum at approximate to 0.4m. A new mec hanism for the AHE in the inelastic hopping regime is identified that repro duces the scaling curve. An extension of Holstein's model for the hopping O HE, the mechanism arises from the combined effects of the double-exchange-i nduced quantal phase in triads of Mn ions and spin-orbit interactions.