Issue
EPL
Volume 82, Number 5, June 2008
Article Number 57007
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/82/57007
Published online 27 May 2008
EPL, 82 (2008) 57007
DOI: 10.1209/0295-5075/82/57007

Pressure-induced americium valence fluctuations revealed by electrical resistivity

A. V. Kolomiets1, J.-C. Griveau2, S. Heathman2, A. B. Shick3, F. Wastin2, P. Faure4, V. Klosek4, C. Genestier4, N. Baclet4 and L. Havela1

1  Charles University, Faculty of Mathematics and Physics, Department of Condensed Matter Physics, Ke Karlovu 5, 121 16 Prague 2, Czech Republic, EU
2  European Commission, Joint Research Centre, Institute for Transuranium Elements - Postfach 2340, D-76125 Karlsruhe, Germany, EU
3  Institute of Physics ASCR - Na Slovance 2, 182 21 Prague 8, Czech Republic, EU
4  Commissariat à l'Energie Atomique, CEA - Centre de Valduc - F-21120 Is-sur-Tille, France, EU

havela@mag.mff.cuni.cz

received 6 February 2008; accepted in final form 11 April 2008; published June 2008
published online 27 May 2008

Abstract
Electrical resistivity of americium-plutonium fcc alloys was studied over a series of high-pressure$\hbox{--}$induced structural phase transitions accompanied by a volume collapse. The temperature dependence of resistivity flattens progressively in the high-pressure phases pointing to the presence of random strong scatterers at the Fermi energy. A theoretical analysis shows that this development is not related to the expected simple delocalization of Am 5f states. Instead it points to pressure-induced americium valence fluctuations (5f6-5f7), which provides a new microscopic basis for the understanding of transuranium materials on the verge of localization of the 5f electronic states.

PACS
75.30.Mb - Valence fluctuation, Kondo lattice, and heavy-fermion phenomena.
74.62.Fj - Pressure effects.
74.25.Fy - Transport properties (electric and thermal conductivity, thermoelectric effects, etc.).

© EPLA 2008