Electronic and magnetic properties of hexagonal rare-earth-Zn-Mg compounds and their relation to the properties of icosahedral alloys

The electronic and magnetic structure of hexagonal rare-earth-zinc-magnesium compounds closely related to the icosahedral phases has been investigated by local density approximation (LDA) and LDA+U calculations. It is shown that both non-magnetic Y-Zn-Mg and antiferromagnetic Gd-Zn-Mg are stabilized by a Hume-Rothery-like electronic mechanism, the formation of a deep structure-induced pseudogap at the Fermi level being effected by an intra-atomic s→d promotion of the rare-earth sites and a strong s, p-d hybridization. The antiferromagnetism of Gd-Zn-Mg is of a layered type; the exchange coupling is an indirect Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the localized 4f moments via the delocalized conduction electrons. The significance of the present results for the electronic and magnetic properties of the icosahedral alloys is discussed. (author)