Polarization of U 5f states in uranium multilayers

X-ray magnetic circular dichroism (XMCD) measurements were performed at the U M(4,5) edges for U/Fe, U/Co, U/Ni, and U/Gd multilayers. In the case of the U/Fe system, a significant polarization of the U 5f electrons was found, but not for U/Co or U/Ni multilayers. We ascribe this to a hybridization of U 5f and Fe 3d states, which overlap in energy near the Fermi level. In the U/Gd system, the XMCD signals were small and yielded magnetic moments of order 0.02 mu(B). The spatial extent of the U 5f polarization is different from that of the U/Fe system and is oscillatory, extending into the center of the U layers.