  Competition between the ferromagnetic double-exchange interaction and the
super-exchange antiferromagnetic interaction is theoretically studied in the
presence of geometrical frustration. As increasing the super-exchange
interaction, the ferromagnetic metal becomes unstable, and is taken over by a
cooperative paramagnetic metal, in sharp contrast with a discontinuous
transition to the antiferromagnetic insulator in the absence of frustration. In
the critical region, the system exhibits a peculiar temperature-independent
behavior with highly incoherent transport, suggesting a large residual entropy
at low temperatures. We discuss the relevance of the results to the
pressure-induced behaviors in Mo pyrochlore oxides [S. Iguchi et al., Phys.
Rev. Lett. 102, 136407 (2009)].
