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Self-consistent energy band calculations for LuFe2 are reported. LuFe2 is found to order magnetically according to the Stoner criterion and the calculated moment is 2.85 mu B/formula unit in agreement with experiment. Spin-orbit coupling was included in the calculation and the spin and induced orbital contributions to the moment at the Fe site also found to be in agreement with experiment. The total moment is calculated to include a contribution of -0.41 mu B at the Lu site, which as yet has not been observed. The mechanism responsible for the ferrimagnetic alignment of the 3d and 5d spin densities is investigated in detail, and the Lu-5d moment related to 3d-5d hybridisation.

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Using first-principles theory, we have calculated the energy of Gd as a function of spin direction, theta, between the c and a axes and found good agreement with experiment for both the total magnetic anisotropy energy and its angular dependence. The calculated low temperature direction of the magnetic moment lies at an angle of 20 degrees to the c axis. The calculated magnetic anisotropy energy of Gd metal is due to a unique mechanism involving a contribution of 7.5 microeV from the classical dipole-dipole interaction between spins plus a contribution of 16 microeV due to the spin-orbit interaction of the conduction electrons. The 4f spin polarizes the conduction electrons via exchange interaction, which transfers the magnetic anisotropy of the conduction electrons to the 4f spin.

It is calculated that spin-orbit coupling induces a predominant orbital magnetic moment (~ 1.5JU B ) antiparallel to the spin moment (1.0JU B ) in the spin-polarized energy bands of UN. The shape of the magnetic form factor, pressure dependence of the moment, and presence of large magnetic anisotropy then become compatible with itinerant-electron theory.PACS numbers: 75.10.Lp, 75.50.EeThe first actinide metal with an ordered groundstate moment is curium, and the elemental actinide metals provide no examples of itinerantelectron magnetism, ordering and /-electron localization occurring almost simultaneously in the middle of the series. 1 The cohesive and magnetic properties of compounds of the light actinides remain puzzling. 2 The dependence of their lattice parameters upon / occupation number is quite different from that of the corresponding rare-earth compounds, and suggests that the / electrons participate in the chemical bond. 3 Most studies of the magnetism of these compounds treat the / electrons as localized or moderately delocalized* 4 There is, however, a relationship between the existence of an ordered moment and the magnitude of the lattice parameter 5 which suggests that the / electrons are itinerant in those compounds with small lattice parameters -in particular, UC and UN.We have therefore made linear-muffin-tinorbital (LMTO) energy-band calculations in the atomic-sphere approximation 6 (ASA) for UC and UN, with self-consistent charge densities constructed in the local-spin-density approximation 7 ' 8 (LSDA), and use of the modified Pauli equation 6 from which spin-orbit splitting is omitted. The lattice parameters and bulk moduli were evaluated from the calculated zero-temperature equations of state 9 ( Table I). The calculated partial /-electronic pressure at the equilibrium lattice parameter is about -40 GPa in either compound -comparable to the / pressure in uranium metal 1 but containing about equal contributions from metallic /-/ bonding and hybridization (hopping) between uranium / and anion p states. TABLE I. Measured and calculated properties of UC and UN.