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Phys. Rev. B 72, 134303 (2005) [7 pages]

Aggregate and single-crystalline elasticity of hcp cobalt at high pressure

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D. Antonangeli1,2, M. Krisch1, G. Fiquet3, J. Badro3,2, D. L. Farber2, A. Bossak1, and S. Merkel4 *
1European Synchrotron Radiation Facility, Boîte Postale 220, F-38043 Grenoble Cedex, France
2Earth Science Division, Energy and Environment Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
3Institut de Minéralogie et de Physique des Milieux Condensés, UMR CNRS 7590, Institut de Physique du Globe de Paris, Université Paris 6, 4 Place Jussieu, 75252 Paris Cedex 05, France
4Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan

Received 1 June 2005; revised 4 August 2005; published 14 October 2005

The longitudinal acoustic phonon dispersion of polycrystalline cobalt was determined by inelastic x-ray scattering up to 99  GPa , throughout the entire stability field of the hcp phase. The obtained aggregate compressional and shear sound velocities are compared with recent single crystal results, impulsive stimulated light scattering and ambient pressure ultrasonic measurements, as well as first principle calculations. We observe a linear evolution of the sound velocities with density up to 75  GPa . In this pressure range, the aggregate elastic properties of the polycrystalline sample are reproduced within 3% by a Voigt-Reuss-Hill average of the single crystal Cij . Above 75  GPa both aggregate velocities show a softening. Our comparative analysis of single-crystalline and polycrystalline results points towards a magnetic origin of the anomaly.


©2005 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevB.72.134303
DOI: 10.1103/PhysRevB.72.134303
PACS: 63.20.−e, 62.50.+p, 62.20.Dc, 61.10.Eq

* Present address: Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720.

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