0 O ct 1 99 8 Hall Effect of La 2 / 3 ( Ca , Pb ) 1 / 3 MnO 3 Single Crystals near the Critical Temperature

The Hall resistivity ρ xy of a La 2/3 (Ca,Pb) 1/3 MnO 3 single crystal has been measured as a function of temperature and field. The overall behavior is similar to that observed previously in thin-films. At 5 K, ρ xy is positive and linear in field, indicating that the anomalous contribution R S is negligible. However, the effective carrier density in a free electron model is n ef f = 2.4 holes/Mn, even larger than the 0.85-1.9 holes/Mn reported for thin-films and far larger than the 0.33 holes/Mn expected from the doping level. As temperature increases, a strong, negative contribution to ρ xy appears, that we ascribe to R S. Using detailed magnetization data, we separate the ordinary (∝ B) and anomalous (∝ M) contributions. Below T C , |R S | ∝ ρ xx , indicating that magnetic skew scattering is the dominant mechanism in the metallic ferromagnetic regime. At and above the resistivity-peak temperature, we find that ρ xy /ρ xx M is a constant, independent of temperature and field. This implies that the anomalous Hall coefficient is proportional to the magnetore-sistance. A different explanation based on two fluid model is also presented.