Reversal of coupling in intermetallic compounds containing two rare earth elements

The reversal in coupling (from antiferromagnetic to ferromagnetic order with increasing x) in Eu_xLa_1−xAl₂ ternaries is successfully analyzed in terms of the RKKY formalism. The Fermi wavevector k required to account for the behavior of these ternaries is k = 0.94 k₀, which is in close agreement with the k-value previously obtained for GdAl₂ and GdAl₂-based ternaries from NMR work. The similarity of behavior of Gd_0.1La_0.9Al₂ and Eu_0.1La_0.9Al₂ and their observed Curie temperatures can also be understood using the same theoretical framework and approximately the same k-values.