HR: 16:00h
AN: MR34A-01    [Abstracts]
TI: Aggregate and Single-Crystalline Elasticity of hcp Cobalt
AU: * Antonangeli, D
EM: antonangeli3@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 United States
AU: Krisch, M
EM: krisch@esrf.fr
AF: European Synchrotron Radiation Facility, Polygone Scientifique Louis Néel, 6 rue Jules Horowitz, Grenoble, 38000 France
AU: Fiquet, G
EM: fiquet@lmcp.jussieu.fr
AF: Institut de Minéralogie et de Physique des Milieux Condensés, UMR CNRS 7590, Institut de Physique du Globe de Paris, Université Paris 6 , 4 Place Jussieu, Paris, 75252 France
AU: Badro, J
EM: james.badro@lmcp.jussieu.fr
AF: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 United States
AU: Badro, J
EM: james.badro@lmcp.jussieu.fr
AF: Institut de Minéralogie et de Physique des Milieux Condensés, UMR CNRS 7590, Institut de Physique du Globe de Paris, Université Paris 6 , 4 Place Jussieu, Paris, 75252 France
AU: Farber, D L
EM: farber2@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 United States
AB: The capability to produce detailed models of the internal structure of the Earth and other planets critically hinges on our knowledge of the pressure dependence of sound velocities and elastic moduli. Here we present data on the complete elastic tensor of hcp cobalt under hydrostatic compression to 39 GPa, derived by Inelastic X-Ray Scattering (IXS). These results are complemented by an IXS study on polycrystalline cobalt throughout the stability range of the hcp phase, to 99 GPa. Interestingly, the single crystal elastic anisotropy is only very weakly reflected in the effective anisotropy of the aggregate. A Voigt-Reuss-Hill average of the single crystal moduli reproduces the results on powder within 3%, up to 75 GPa. Above this pressure, we observe an anomalous softening in the density evolution of the aggregate velocities. This type of comparative analysis between single crystal and polycrystal is essential for characterizing the bulk properties of textured samples and provides a basis for the rigorous testing of the orientational averaging schemes currently employed to link the single crystal elastic moduli with the aggregate sound velocities. We note that only through the combined approach of experiment and theory (ab initio calculations) we can progress in both refining first principle methods and in getting more insights into the physics of the investigated system. In the specific case of Co, we inferred a magnetic transition to be the physical origin for the high pressure elastic anomaly. Finally, our study points out the importance of coupling between the electronic and magnetic degrees of freedom to elastic properties at high pressure. We suggest that these effects likely play an important role in elasticity of deep planetary interiors.
DE: 3909 Elasticity and anelasticity
DE: 3924 High-pressure behavior
DE: 5102 Acoustic properties
DE: 5109 Magnetic and electrical properties (0925)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005