Magnetotransport properties of Gd2(Mo1-xVx)2O7 with pyrochlore structure

Magnetization and magnetoresistance (MR) measurements were performed on pyrochlores Gd2Mo2O7 and Gd-2(Mo0.6V0.4)(2)O-7. It was shown that both compounds are ferromagnets below T-C = 80 K with the same alignment of magnetic moments of 4f and 4d ions. The substitution of Mo ions by V leads to the increase of the resistivity without changes in the magnetic state. Gd(2)Mo(2)O7 exhibits a large negative magnetoresistance ratio, especially in the low-magnetic-field regime, which increases strongly with decreasing temperature. In Gd-2(Mo0.6V0.4)(2)O-7 below T-C the magnetoresistance ratio changes from negative to positive with decreasing temperature. These data indicate that the mechanism of the magnetoresistance effect in the molybdates differs markedly from that for manganites studied in detail with perovskite and pyrochlore structures.