Superconductivity and long range magnetic order in the body-centered tetragonal system Er(Rh/sub 1-x/Ru/sub x/)4B4

In the system Er(Rh/sub 1-x/Ru/sub x/)4B4, the compound ErRu4B4 orders magnetically at T/sub m/ = 2.10K; whereas, compounds for 0.05 less than or equal to x less than or equal to 0.40 become superconducting at T/sub c/ approximately greater than 7.50K. The details of these low temperature states are investigated via a series of measurements on 19 samples with 0.05 less than or equal to x less than or equal to 1.00. T/sub c/ is relatively composition independent up to x approx. = 0.40, followed by a sharp drop for x values between 0.40 and 0.50. This critical composition for the destruction of superconductivity, x/sub cr/ approx. = 0.50, is not influenced by the magnetic properties of the rare earth. T/sub m/ is depressed when Rh is substituted for Ru and for this system superconductivity and long range magnetic order are mutually exclusive