Field-induced magnetism in itinerant<i>f</i>-electron systems: U, Pu, and Ce

Abstract

We demonstrate, by means of first-principles calculations, that in the field-induced magnetic state of \ensuremath{\alpha}-cerium and \ensuremath{\alpha}-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 \ensuremath{\alpha}-uranium in very good agreement with experiment. The calculated form factor of \ensuremath{\alpha}-cerium, when assuming that the f electron is itinerant, is very different from the localized ${\mathrm{Ce}}^{3+}$ form factor, and we propose that a measurement of the magnetic form factor of \ensuremath{\alpha}-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.