Transport and magnetic properties of Y2-xBixRu2O7

Transport and magnetic properties of the pyrochlore ruthenates Y2-xBixRu2O7 have been studied. In Y2Ru2O7, the specific heat shows a large jump at a t emperature T = T-G, where the transition to the spin-glass state with decre asing T is observed, in contrast with ordinary behavior found in typical sp in-glass compounds. The transition temperature To decreases with increasing x and goes to zero at x = x(c) in the region of the insulator-metal phase boundary. The electronic specific heat coefficient gamma is enhanced signif icantly with decreasing x from 2.0, indicating an increase of the effective d-electron mass, and exhibits a pronounced peak at x(c). Near the metal-in sulator phase boundary, the Hall coefficient shows a T-dependent behavior a nd the Hall angle obeys a T-2 law above T-G, which is often found in the hi gh-T-c cuprates. (C) 2000 Elsevier Science B.V. All rights reserved.