Vanishing RKKY interactions in Ce-based cage compounds

Abstract

Abstract We report the results of thermodynamic measurements in external magnetic field of the cubic Ce-based cage compounds CeT 2Cd20 (T = Ni,Pd). Our analysis of the heat-capacity data shows that the Γ7 doublet is the ground state multiplet of the Ce3+ ions. Consequently, for the Γ7 doublet it can be theoretically shown that the Ruderman–Kittel–Kasuya–Yosida interaction between the localized Ce moments mediated by the conduction electrons, must vanish at temperatures much lower than the energy separating the ground state doublet from the first excited Γ8 quartet. Our findings provide an insight as to why no long range order has been observed in these compounds down to temperatures in the milliKelvin range.