EFFECT OF COMPOSITION ON THE ANDERSON HYBRIDIZATION IN TERNARY CUBIC ALLOYS OF CE

The cubic compounds of Ce with Zn, Ag and Cd are considered to behave as Kondo lattices depending on applied pressure or alloying. In particular their magnetic behaviour is ascribed to the possible competition between the RKKY interaction and the Kondo effect. We calculate the hybridisation width Δ of the Anderson model for the two ternary cubic compounds CeCd1−x Ag x , CeCd1−x Zn x . This quantity determines, along with the positionE f and correlationU of the Cef-state, the antiferromagnetic coupling constantJ s-f of the Kondo Hamiltonian. We start fromab initio electronic calculations performed with the FLAPW method in the LSDA and carry out an LCAO parametrisation of the band structure for the pure binary compounds. A virtual-crystal approximation is used to obtain the LCAO parameters of the ternary alloys. We check the accuracy of this approximation on CeCd0.5Zn0.5 by a self-consistent FLAPW calculation on the supercell Ce2CdZn, finding that it is satisfactory for the present purposes. We find that Δ, in the whole concentration range, is affected quantitatively much more by substitution of Cd by Ag than by Zn—isovalent to Cd—, although the latter one induces a larger volume reduction. Moreover, the Δ behaviour in CeCd1−x Zn x contrasts with the expected volume dependence. This shows that electronic effects may be more effective than electronic pressure alone (volume effects) in determining the Kondo properties of substitutional systems