Journal of Magnetism and Magnetic Materials 233 (2001) 53–56 The use of resonant X-ray magnetic scattering to examine the magnetic phases in UAs-USe solid solutions M.J. Longfield a,b, *, J. Wilmshurst a,b , L. Bouchenoire a , M.J. Cooper a , D. Mannix c , G.H. Lander c , N. Bernhoeft d , A. Stunault b,e , W.G. Stirling e , J. Pollmann f , D. Haskel f , G. Srajer f a Department of Physics, The University of Warwick, Coventry CV4 7AL, UK b XMaS CRG, Pluo B3, ESRF, BP 220, 38043 Grenoble, France c European Commission, JRC, Institute for Transuranium Elements, Postfach 2340, Karlsruhe, Germany d Department de Recherche Fond. Sur la Matiere Condensee, CEA-Grenoble, 38054, Grenoble, France e Department of Physics, Oliver Lodge Lab., The University of Liverpool, Liverpool L69 7ZE, UK f SRI-CAT, Advanced Photon Source, Argonne, USA Abstract Recent discoveries in the study of magnetism using synchrotron radiation are helping to elucidate the complex magnetism of the actinides. In this article we discuss the use of resonant X-ray magnetic scattering to investigate multi-k structures and the existence of induced magnetic moments in UAs-USe solid solutions. We present magnetic scattering experiments conducted at the ID20 and XMaS beamlines at the ESRF, Grenoble, France, and the ID-1 SRI-CAT beamline at the APS, Argonne, USA. # 2001 Elsevier Science B.V. All rights reserved. Keywords: X-ray scattering; Resonant scattering; Actinide 1. Introduction The uranium monopnictides and monochalco- genides with the fcc structure display a fascinating variety of magnetic structures. The uranium pnic- tides have an antiferromagnetic spin arrangement with 1k,2k and 3k structures upon traversing the series, and all of the uranium chalcogenides are ferromagnets. Although these materials have been characterized by neutron techniques [1] the origin of the multi-k structures is not yet fully under- stood. Recent discoveries in the study of magnet- ism using synchrotron radiation are beginning to elucidate these complex magnetic materials. For example, resonant X-ray magnetic scattering (RXMS) has been used to examine the nature of the couplings leading to the 2k structure [2] of UAs, and has also revealed spin polarization of the As electronic states [2,3]. In this article we report experiments that examine the interplay of the RXMS cross section with multi-k structures and examine resonant scattering at the As and Se K edges of the UAs-USe solid solutions. *Corresponding author. M.J. Longfield. XMaS CRG, Pluo B3, ESRF, 38043 Grenoble, France. Tel.: +33-476-88-25-80; fax: +33-476-88-24-55. E-mail address: matt@esrf.fr (M.J. Longfield). 0304-8853/01/$-see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0304-8853(01)00226-8