Effect of Iridium substitution in Rh17S15

Abstract

We have studied the effect of Iridium doping (IrxRh17−xS15) in the Rhodium sites of the strongly correlated superconductor Rh17S15. Even at low levels of doping (x = 1 and 2) we see a drastic decrease in the upper critical fields as compared to the undoped system. We deduce that there is a reduction in the density of states at Fermi level from reduced susceptibilities and Sommerfeld coefficients in the doped samples. The 'fishtails' which were very prominent in the magnetization data of the undoped crystal are strongly supressed here. The resistivity data of the doped crystals show a remarkably different trend from the undoped crystal in the appearance of a minimum at lower temperatures, the position of which is fairly constant at different fields. Our data supports the notion that Iridium, which is a bigger atom than Rhodium, reduces the strong correlations that existed due to interaction between Rhodium atoms in the undoped system.