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Title: Emerging Magnetism Arising from Self-Damage in (alpha) and (delta)-Pu

Abstract

As a consequence of the unusual nature of plutonium's electronic structure, point- and extended-defects are expected to, and do exhibit extraordinary properties[1]. Low temperature magnetic susceptibility measurements on Pu and fcc-Pu(Ga) show that the magnetic susceptibility increases as a function of time, yet upon annealing the specimen returns to its initial magnetic susceptibility. This excess magnetic susceptibility (EMS) arises from the {alpha}-decay and U recoil damage cascades which produce vacancy and interstitials as point and extended defects. The temperature of the first annealing stage defines a temperature (<35K) below which we are able to characterize the time and temperature evolution of the accumulating damage cascades as being a saturation function. The temperature dependence of the EMS is well described by a time independent, Curie-Weiss curve arising from a volumetric region surrounding each U damage cascade. This saturation picture also leads directly to a determination of the microscopic volume of the specimen that is affected by the frozen-in damage cascade. For our measurements in d-Pu we calculate a diameter of the magnetically affected volume of {approx} 250 {angstrom} per damage cascade. This should be compared with an estimated volume that encloses the damage cascade itself (determined from molecular dynamics) of {approx}100more » {angstrom}. Hence, the ratio of these volumes is {approx}8. The observed anomalous magnetic behavior is likely a consequence of the highly correlated nature of the electrons. Similarities with defects in hole-doped superconductors suggest a general phenomenon in strongly correlated electron systems, of which Pu may be a particularly unusual or special example.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
894789
Report Number(s):
UCRL-JRNL-217247
TRN: US0700316
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Society Symposium Proceedings, vol. 893, N/A, March 1, 2006, pp. 0893-JJ04-03.1-11
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; DEFECTS; ELECTRONIC STRUCTURE; ELECTRONS; INTERSTITIALS; MAGNETIC SUSCEPTIBILITY; MAGNETISM; SATURATION; SUPERCONDUCTORS; TEMPERATURE DEPENDENCE

Citation Formats

McCall, S K, Fluss, M J, Chung, B W, Chapline, G F, Jackson, D D, and McElfresh, M W. Emerging Magnetism Arising from Self-Damage in (alpha) and (delta)-Pu. United States: N. p., 2005. Web.
McCall, S K, Fluss, M J, Chung, B W, Chapline, G F, Jackson, D D, & McElfresh, M W. Emerging Magnetism Arising from Self-Damage in (alpha) and (delta)-Pu. United States.
McCall, S K, Fluss, M J, Chung, B W, Chapline, G F, Jackson, D D, and McElfresh, M W. Wed . "Emerging Magnetism Arising from Self-Damage in (alpha) and (delta)-Pu". United States. doi:. https://www.osti.gov/servlets/purl/894789.
@article{osti_894789,
title = {Emerging Magnetism Arising from Self-Damage in (alpha) and (delta)-Pu},
author = {McCall, S K and Fluss, M J and Chung, B W and Chapline, G F and Jackson, D D and McElfresh, M W},
abstractNote = {As a consequence of the unusual nature of plutonium's electronic structure, point- and extended-defects are expected to, and do exhibit extraordinary properties[1]. Low temperature magnetic susceptibility measurements on Pu and fcc-Pu(Ga) show that the magnetic susceptibility increases as a function of time, yet upon annealing the specimen returns to its initial magnetic susceptibility. This excess magnetic susceptibility (EMS) arises from the {alpha}-decay and U recoil damage cascades which produce vacancy and interstitials as point and extended defects. The temperature of the first annealing stage defines a temperature (<35K) below which we are able to characterize the time and temperature evolution of the accumulating damage cascades as being a saturation function. The temperature dependence of the EMS is well described by a time independent, Curie-Weiss curve arising from a volumetric region surrounding each U damage cascade. This saturation picture also leads directly to a determination of the microscopic volume of the specimen that is affected by the frozen-in damage cascade. For our measurements in d-Pu we calculate a diameter of the magnetically affected volume of {approx} 250 {angstrom} per damage cascade. This should be compared with an estimated volume that encloses the damage cascade itself (determined from molecular dynamics) of {approx}100 {angstrom}. Hence, the ratio of these volumes is {approx}8. The observed anomalous magnetic behavior is likely a consequence of the highly correlated nature of the electrons. Similarities with defects in hole-doped superconductors suggest a general phenomenon in strongly correlated electron systems, of which Pu may be a particularly unusual or special example.},
doi = {},
journal = {Materials Research Society Symposium Proceedings, vol. 893, N/A, March 1, 2006, pp. 0893-JJ04-03.1-11},
number = ,
volume = ,
place = {United States},
year = {Wed Nov 16 00:00:00 EST 2005},
month = {Wed Nov 16 00:00:00 EST 2005}
}
  • We report photoemission results on {alpha}- and {delta}-Pu using a laser plasma light source (LPLS) as well as He light as the exciting radiation. The LPLS is a pseudocontinuum tunable light source with intensities rivaling some second-generation synchrotrons. Both phases of Pu display a narrow, temperature-independent, 5f-related feature at the Fermi energy, which is narrower in {delta}-Pu than in {alpha}-Pu, suggestive of possible heavy-fermion-like behavior. In both {alpha}-Pu and {delta}-Pu the photon-energy dependence of this feature suggests some 6d admixture, albeit somewhat smaller in {delta}-Pu. In this respect it differs qualitatively from Ce and U heavy fermions. (c) 2000 Themore » American Physical Society.« less
  • Extended x-ray absorption fine structure spectroscopy (EXAFS) is used to investigate the local atomic environment and vibrational properties of plutonium and gallium atoms in the {alpha}{prime} and {delta} phases of a mixed phase Pu-Ga alloy. EXAFS results measured at low temperature compare the structure of the mixed phase sample with a single-phase {delta}-Pu sample. EXAFS spectral components attributed to both {alpha}{prime}-Pu and {delta}-Pu were observed in the mixed phase sample. Ga K-edge EXAFS spectra indicate local atomic environments similar to the Pu LIII-edge EXAFS results, which suggests that Ga is substitutional for Pu atoms in both the monoclinic {alpha}{prime}-Pu andmore » the fcc {delta}-Pu structures. In {delta}-Pu, we measure a Ga-Pu bond length contraction of 0.11 Angstroms with respect to the Pu-Pu bond length. The corresponding bond-length contraction around Ga in {alpha}{prime}-Pu is only 0.03 Angstroms. Results from temperature-dependent Pu LIII-edge EXAFS measurements are fit to a correlated Debye model, and a large difference in the Pu-Pu bond Debye temperature is observed for the {alpha}{prime} and {delta} phases: {theta}{sub cD}({alpha}{prime})=159{+-}13 K versus {theta}{sub cD}({delta})=120{+-}3 K. The corresponding analysis for the Ga K EXAFS determines a Ga-Pu bond Debye temperature of {theta}{sub cD}({delta})=188{+-}12 K in the {delta}-Pu phase. These results are related to the observed solubility of Ga in {delta}-Pu, the ''stabilization'' of {delta}-Pu by Ga at room temperature, and the insolubility of Ga in {alpha}{prime}-Pu.« less
  • The retained {delta} phase of a Pu-1.9 at.% Ga alloy is metastable with respect to the martensitic {delta} {yields} {alpha}{prime} transformation that occurs at low temperatures. This transformation has been shown to proceed by means of an isothermal martensitic mode, but the kinetics of the transformation are atypical. The transformation exhibits a 'double-C' in a time-temperature-transformation diagram, wherein there exist two temperatures where a given amount of transformation occurs in a minimum amount of time. The cause of the double-C kinetics remains uncertain, eliciting proposals of multiple mechanisms, multiple paths, or different morphologies as possible origins. Recently, a 'conditioning' treatmentmore » was found to affect the {delta} {yields} {alpha}{prime} transformation, but the underlying mechanism by which the conditioning treatment influences the transformation has not yet been resolved. In this study, microstructural characterization as a function of temperature, time, and conditioning has been employed to illuminate the role of conditioning in the {delta} {yields} {alpha}{prime} transformation. Conditioning is found to enhance transformation in the upper-C and to enable transformation in the lower-C. The data garnered from these experiments suggest that conditioning is intimately linked to nucleation processes and of little consequence to the growth and morphology of the {alpha}{prime} product phase.« less