Interplay of superconductivity and charge density wave ordering in pseudoternary alloy compounds: Lu2Ir3(Si1-xGex)5, Lu2(Ir1-xRhx)3Si5, and (Lu1-xScx)Ir3Si5

We explore the interplay and competition between superconductivity (SC) and the charge density wave (CDW) ordering transition on pseudoternary alloys (Lu1-xScx)(2)Ir3Si5, Lu-2(Ir1-xRhx)(3)Si-5, and Lu2Ir3(Si1-xGex)(5) via magnetization, thermal and transport measurements. We track the evolution of the superconducting transition temperature T-SC and the CDW ordering transition temperature T-CDW as a function of doping concentration x to present a temperature-concentration phase diagram for each of the series of compounds. We find that as we increase x, T-CDW and T-SC show a nonmonotonic behavior in Lu2Ir3(Si1-xGex)(5). Here, we observe that both CDW and SC survive till 20% of the Ge substitution. In Lu-2(Ir1-xRhx)(3)Si-5, as Rh concentration increases, T-CDW varies rapidly from 207 to 284 K, whereas the T-SC changes gradually from 5.5 to 2.5 K. In addition, the Sc substitution at the Lu site of Lu2Ir3Si5 displays a slight change in CDW transition temperature, without affecting the SC ordering temperature too much. Our study reveals that the CDW anomalies are broadened and smeared out, probably by substitutional disorder effects. The heat capacity data in the vicinity of the CDW transition for all the substituted alloys are analyzed using a model of critical fluctuations in addition to a mean-field contribution and a smooth lattice background. The critical exponent changes appreciably with increasing disorder, which suggests that the first-order CDW transition in the parent compound Lu2Ir3Si5 changes to a second-order transition via doping.