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Vibrational and electronic entropy of β-cerium and γ-cerium measured by inelastic neutron scattering

Manley, Michael E. and McQueeney, Robert J. and Fultz, Brent and Osborn, Raymond and Kwei, George H. and Bogdanoff, Peter D. (2002) Vibrational and electronic entropy of β-cerium and γ-cerium measured by inelastic neutron scattering. Physical Review B, 65 (14). Art. No. 144111. ISSN 0163-1829. http://resolver.caltech.edu/CaltechAUTHORS:MANprb02a

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Abstract

Time-of-flight (TOF) inelastic neutron-scattering spectra were measured on β-cerium (double hcp) and γ-cerium (fcc) near the phase-transition temperature. Phonon densities of states (DOS) and crystal-field levels were extracted from the TOF spectra. A softening of the phonon DOS occurs in the transition from β- to γ-cerium, accounting for an increase in vibrational entropy of ΔSvibγ-β=(0.09±0.05)kB/atom. The entropy calculated from the crystal-field levels and a fit to calorimetry data from the literature were significantly larger in β-cerium than in γ-cerium below room temperature, but the difference was found to be negligible at the experimental phase-transition temperature. A contribution to the specific heat from Kondo spin fluctuations was consistent with the quasielastic magnetic scattering, but the difference between phases was negligible. To be consistent with the latent heat of the β-γ transition, the increase in vibrational entropy at the phase transition may be accompanied by a decrease in electronic entropy not associated with the crystal-field splitting or spin fluctuations. At least three sources of entropy need to be considered for the β-γ transition in cerium.


Item Type:Article
Additional Information:©2002 The American Physical Society. Received 26 October 2001; published 1 April 2002. The authors would like to thank Professor K.A. Gschneidner for lending us the calorimetry data. This work was supported by the U.S. Department of Energy under Contract No. W-7405-ENG-36 with the University of California and Grant No. DE-FG03-96ER45572 with the California Institute of Technology. This work has benefited from the use of the IPNS at Argonne National Laboratory. This facility is funded by the U.S. Department of Energy, under Contract No. W-31-109-ENG-38.
Subject Keywords:PHONON DENSITIES; DISORDERED NI3AL; STATES; PRESSURE; ALLOYS; MODEL; HEAT; CE
Record Number:CaltechAUTHORS:MANprb02a
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:MANprb02a
Alternative URL:http://dx.doi.org/10.1103/PhysRevB.65.144111
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8570
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:21 Aug 2007
Last Modified:26 Dec 2012 09:40

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