Eur. Phys. J. B 9, 605-611 (1999)
https://doi.org/10.1007/s100510050804

Collapse of the magnetic ordering and structural anomalies in the U_xLa_1-xS system: neutron diffraction and specific heat measurements

¹ Département de Recherche Fondamentale sur la Matière Condensée, SPSMS, CEA/Grenoble, 38054 Grenoble Cedex 9, France
² European Commission, JRC, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe, Germany
³ Laboratorium für Festkörperphysik, ETH-Zürich, 8093 Zürich, Switzerland

Corresponding author: ^a bombardi@drfmc.ceng.cea.fr

Received: 18 September 1998
Published online: 15 June 1999

Abstract

We report specific heat and neutron diffraction measurements of seven samples in the solid solution system U_xLa1-xS. All samples have the simple fcc NaCl crystal structure. Both specific heat and neutron diffraction confirm the suggestion from the earlier magnetic measurements that the ferromagnetism disappears abruptly at x_c 0.57. Near x_c there is a doubling of γ the electronic contribution to the specific heat, as compared to the value of 23 mJ mol^-1K^-2 in pure US. Around x_c the widths of the nuclear Bragg peaks show a considerable broadening, as well as anomalies in the mean lattice parameter, as compared to those expected from Vegard's law. A preliminary analysis suggests this broadening may be due to a loss of long range lattice order near x_c. However, these changes are independent of temperature, so that further experiments are necessary before they can be associated with the changes in magnetic behavior at x_c.