Eur. Phys. J. B 21, 547-552 (2001)
https://doi.org/10.1007/s100510170165

On the evolution of the ground state in the system U_xLa_1-xS: Polarized neutron diffraction and X-ray magnetic circular dichroism study

¹ Département de Recherche Fondamentale sur la Matière Condensée, Commissariat à l'Énergie Atomique-Grenoble, 38054 Grenoble, France
² European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe, Germany
³ Institut Laue Langevin, 38043 Grenoble, France
⁴ European Synchrotron Radiation Facility, 38043 Grenoble, France
⁵ Laboratorium für Festkörperphysik, Eidgenössische Technische Hochschule-Zürich, 8093 Zürich, Switzerland

Corresponding author: ^a bombardi@ill.fr

Received: 31 January 2001
Published online: 15 June 2001

Abstract

In the U_xLaS system there is an abrupt loss of the long-range ferromagnetic ordering found in pure US at a critical concentration , which is far above the percolation limit. As the magnetic ground state in such a system can be strongly affected by small variations of the 5f localization, we have investigated a set of samples with different x by polarized neutron diffraction and X-ray magnetic circular dichroism (XMCD). The neutron results are consistent with early measurements performed on pure US. Even at the lowest U content (x=0.15, below x_c) the shape of the induced form factor (f(Q)) is comparable with that found for x=1 and is well reproduced by either a U⁴⁺ or a U³⁺ state. The ratio between the orbital and the effective spin moments in the XMCD measurements confirms this result, but the evolution of the shape at the M₅ edge suggests an abrupt change in the distribution of the electrons (holes) in the 5f density of states around x_c.