Orbital magnetism in the itinerant ferromagnet NpOs2

The electronic structure of NpOs2 has been calculated. The neptunium magnetic moments of the compound are shown to be dominated by a large orbital contribution that actually exceeds the spin part. To calculate the orbital contribution to the magnetism spin-orbit coupling has been included in the band Hamiltonian together with a shift of the single-electron eigenvalues, which takes Hund's second rule into account. It is found that this treatment gives a good description of the magnetic properties, whereas standard methods for calculating magnetic properties fail