Field-induced magnetism in itinerant f-electron systems: U, Pu, and Ce

We demonstrate, by means of first-principles calculations, that in the field-induced magnetic state of α-cerium and α-uranium the spin and orbital moments are coupled parallel rather than antiparallel as expected from Hund's third rule. This behavior gives a magnetic form factor for α-uranium in very good agreement with experiment. The calculated form factor of α-cerium, when assuming that the f electron is itinerant, is very different from the localized Ce3+ form factor, and we propose that a measurement of the magnetic form factor of α-Ce can indicate whether the f state is localized or itinerant. The field-induced magnetism of plutonium is shown to be almost exclusively of orbital character and the induced spin density of plutonium is highly anomalous