Low-temperature Hall effect in substituted Sr₂RuO₄

We report the results of a study of the Hall effect and magnetoresistance in single crystals of Sr2RuO4 in which Sr2+ has been substituted by La3+ (Sr2-yLayRuO4) or Ru4+ by Ti4+ (Sr2Ru1-xTixO4). For undoped Sr2RuO4, the purity is so high that the strong-field Hall coefficient can be measured for fields above 4 T. The conventional weak-field Hall coefficient as a function of doping shows a sharp jump and sign change at ysimilar to0.01 that is unrelated to either a sharp change in Fermi-surface topography or a magnetic instability. The implications of these results are discussed