A High-Pressure Structure in Curium Linked to Magnetism
S. Heathman,1*
R. G. Haire,2
T. Le Bihan,3
A. Lindbaum,4
M. Idiri,1
P. Normile,1
S. Li,5,6
R. Ahuja,5,6
B. Johansson,5,6
G. H. Lander1
Curium lies at the center of the actinide series and has a half-filled
shell with seven 5
f electrons spatially residing inside its
radon core. As a function of pressure, curium exhibits five
different crystallographic phases up to 100 gigapascals, of
which all but one are also found in the preceding element, americium.
We describe here a structure in curium, Cm III, with monoclinic
symmetry, space group
C2/c, found at intermediate pressures
(between 37 and 56 gigapascals). Ab initio electronic structure
calculations agree with the observed sequence of structures
and establish that it is the spin polarization of curium's 5
f electrons that stabilizes Cm III. The results reveal that curium
is one of a few elements that has a lattice structure stabilized
by magnetism.
2 Oak Ridge National Laboratory (ORNL), Chemical Sciences Division, Office Box 2008, MS-6375, Oak Ridge, TN 37831, USA.
3 European Synchrotron Radiation Facility (ESRF), Boîte Postale 220, F-38043 Grenoble, France.
4 Vienna University of Technology, Institute for Solid State Physics, Wiedner Hauptstrasse 8-10/138, A-1040, Vienna, Austria.
5 Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden.
6 Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, SE-100 44 Stockholm.
Present address: Commissariat à l'Energie Atomique Valduc, Departement de Recherches sur les Matériaux Nucléaires, Service Etudes de Métallurgie Physique, Laboratoire Etudes des Constantes Physiques, F-21120 Is-sur-Tille, France.
* To whom correspondence should be addressed. E-mail: heathman{at}itu.fzk.de
