MAGNETOTRANSPORT PROPERTIES OF GD-2(MO1-XVX)(2)O-7 WITH PYROCHLORE STRUCTURE

Magnetization and magnetoresistance (MR) measurements were performed o n pyrochlores Gd2Mo2O7 and Gd-2(Mo0.6V0.4)(2)O-7. It was shown that bo th 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 mag netic state. Gd(2)Mo(2)O7 exhibits a large negative magnetoresistance ratio, especially in the low-magnetic-field regime, which increases st rongly with decreasing temperature. In Gd-2(Mo0.6V0.4)(2)O-7 below T-C the magnetoresistance ratio changes from negative to positive with de creasing temperature. These data indicate that the mechanism of the ma gnetoresistance effect in the molybdates differs markedly from that fo r manganites studied in detail with perovskite and pyrochlore structur es.