Abstract
In this paper, we report careful transport and magnetic measurements on single crystals of deuterated {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br. By cooling the sample at different rates, it is found that cooling through 80K has a dramatic effect on the normal state metal-insulator transition and the superconducting transition temperatures. In-plane resistivity depends strongly on the cooling rate for temperatures below 80K, above which all resistivity curves cooled at different rates converge. By comparing it with the nondeuterated salt and the quasi-1D Bechgaard salt, we speculate that 80K corresponds to a structural phase transition in the anion chain. Fast cooling through 80K will freeze the high temperature magnetic phase to low temperatures and the presence of local magnetic moments suppresses the superconducting T{sub c}. {copyright} {ital 1998} {ital The American Physical Society}
