DENSITY-OF-STATES-DRIVEN TRANSITION FROM SUPERCONDUCTIVITY TO FERROMAGNETISM IN CE(RU1-XRHX)3B2 - SCENARIO FOR AN EXCHANGE-SPLIT KONDO RESONANCE

We have investigated the interesting alloy system Ce(Ru1-xRhx)3B2, where the physical properties change from superconducting to ferromagnetic as x changes from 0 to 1. We report the results of transport, magnetic, crystallographic, and electron-spectroscopy measurements, and a theoretical analysis of the electron-spectroscopy data using the impurity Anderson Hamiltonian applied to the Ce 4f electrons. Superconductivity exists in the range 0<x<0.38, while ferromagnetism occurs in the range 0.84<x<1. Our studies of superconductivity and ferromagnetism in Ce(Ru1-xRhx)3B2 show that ferromagnetism is associated with nearly trivalent Ce ions. We find that the alloying mechanism controlling the low-energy properties of this system is the transition-metal 4d density of states at the Fermi level, rather than any parameter directly connected to the 4f states, such as its binding energy, Coulomb interaction, or the average hybridization strength between the localized 4f and conduction electrons. We use this result to further elucidate our previously proposed exchange split-Kondo resonance model of the ferromagnetism near x=1. © 1990 The American Physical Society.