Study on anomalous Hall resistivity of Nd ₂Mo _2-xTi _xO ₇

Hall resistivity ρ _H has been studied for single crystals of Nd ₂Mo ₂O ₇, which has the ferromagnetic and chiral ordered state. Effects of Ti-doping on ρ _H have also been studied down to 3 K under the magnetic field (H) up to 7 T. The T- and H-regions of the measurements have been extended for non-doped samples to 50 mK and 15 T. respectively. From the results, it has been confirmed that two components of the anomalous Hall resistivity exist. One is proportional to the net magnetization of Mo atoms, M _Mo. It changes its sign with the doping. The other is proportional to the net magnetization of Nd atoms, M _Nd and does not exhibit the sign change. The Hall resistivity has a finite and almost T-independent value at very low temperatures. These results on the behavior of ρH are discussed by considering the existing theories including the one recently proposed by a mechanism related to the spin chiral order.