Transport and magnetic properties of Tl2Mn2-xRuxO7 diluted system

The magnetic and transport properties of Tl2Mn2-xRuxO7 pyrochlores are anal yzed as a function of the substitution rate (0 less than or equal to x less than or equal to 2). For x less than or equal to 0.2, the system exhibits colossal magnetoresistance (CMR) and ferromagnetic ordering. For higher dop ing rates CMR is completely washed out and the transport properties mimics that of the Tl2Ru2O7 pure compound with a semiconductor-to-metal transition at a temperature that decreases as x increases. The magnetic frustration p rogressively increases signalling the increase of antiferromagnetic interac tions and the geometrical frustration intrinsic to the pyrochlore structure . (C) 1999 American Institute of Physics. [S0021-8979(99)19908-0].