ORBITAL PARAMAGNETISM IN METALLIC SYSTEMS WITH LARGE ANGULAR MOMENTA

We demonstrate that the field induced spin and orbital moments in paramagnetic metals in general are parallel, since the Zeeman energy overcomes the spin-orbit energy that is in favor of an antiparallel arrangement when the electronic shell is less than half-filled. In the early actinides, however, the spin-orbit energy becomes sufficiently strong to approach the border where the moments can couple antiparallel. This results in peculiar magnetic states for alpha-Pu and some uranium compounds, where the spin moments are antiparallel to the applied field and the magnetic response dominated by the orbital character, and consequently these systems display unusual spin densities and magnetic form factors.