Theoretical aspects of the magnetism in the ferromagneticAFe2systems (A=U, Np, Pu, and Am)

We report on spin-polarized energy-band calculations for the cubic Laves-phase systems ${\mathrm{UFe}}_2$, ${\mathrm{NpFe}}_2$, ${\mathrm{PuFe}}_2$, and ${\mathrm{AmFe}}_2$. The calculations were performed with the local-density approximation for the exchange and correlation potential together with a term that shifts the one-electron eigenvalues and takes into account the different interelectronic repulsions for electrons with different 5f magnetic quantum numbers. The spin-orbit interaction was also included in the band Hamiltonian. Thus the parameter-free calculations incorporate Hund’s first, second, and third rules. The magnetism in the first three compounds was found to be dominated by a large orbital contribution coupled antiparallel to the spin moment. In the calculations for ${\mathrm{AmFe}}_2$, the 5f electrons were treated as core electrons. The magnetism was here found to behave very much like the magnetism of similar rare-earth Laves-phase compounds.