Negative thermal expansion and antiferromagnetism in the actinide oxypnictide

T. Klimczuk,1,2,* H. C. Walker,3,4 R. Springell,5,6 A. B. Shick,1,7 A. H. Hill,3,† P. Gaczyński,1 K. Gofryk,8 S. A. J. Kimber,3 C. Ritter,9 E. Colineau,1 J.-C. Griveau,1 D. Bouëxière,1 R. Eloirdi,1 R. J. Cava,10 and R. Caciuffo1 1Institute for Transuranium Elements, JRC, European Commission, Postfach 2340, 76125 Karlsruhe, Germany 2Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80-952 Gdansk, Poland 3European Synchrotron Radiation Facility, 6 rue Jules Horowitz, Boı̂te Postale 220, 38043 Grenoble Cedex 9, France 4Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany 5London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom 6Royal Commission for the Exhibition of 1851 Research Fellow, Interface Analysis Centre, University of Bristol, Bristol BS2 8BS, United Kingdom 7Institute of Physics, ASCR, Na Slovance 2, 18221 Prague 8, Czech Republic 8Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA 9Institute Laue-Langevin, 6 rue Jules Horowitz, Boı̂te Postale 156, 38042 Grenoble Cedex 9, France 10Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA (Received 5 April 2012; revised manuscript received 20 April 2012; published 9 May 2012)