Hall effect of a layered manganite La1.2Sr1.8Mn2O7 single crystal

We report the first Hall effect measurements on the layered manganite La1.2 Sr1.8Mn2O7 single crystal, a colossal magnetoresistance material with T-c = 121 K. At low temperatures, the Hall resistivity is a mixture of a positiv e ordinary Hall effect and a negative anomalous Hall effect, similar to tha t of the pseudo-cubic counterpart La(1-x)A(x)MnO(3). However, the carrier c oncentration from the high-field slope turns out to be 0.36 +/- 0.02 holes/ Mn, very close to the nominal doping concentration (0.4 holes/Mn), in contr ast to the large deviation in La(1-x)A(x)MnO(3). We also find that the anom alous Hall effect becomes larger for T < 40 K, where the longitudinal resis tivity shows a minimum. (C) 2000 Elsevier Science B.V. All rights reserved.