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probed by muon spin rotationOishi, Kazuki; Heffner, R. H.; Ito, Takashi; Higemoto, Wataru; Morris, G. D.*; Bauer, E. D.*; Graf, M. J.*; Zhu, J.-X.*; Morales, L. A.*; Sarrao, J. L.*; et al.
Physica B; Condensed Matter, 403(5-9), p.1013 - 1014, 2008/04
Times Cited Count：0 Percentile：0(Physics, Condensed Matter)PuCoGa has attracted much interest because it is the first Pu-based superconductor, having an order of magnitude higher transition temperature 
K than the isostructural heavy fermion superconductor CeCoIn (
K). The mechanism of the superconductivity in PuCoGa is still under investigation, though recent experiments and theory suggest a magnetic origin. A unique aspect of this compound is the self-irradiation damage because Pu (
Pu, 
= 24,000 years) creates lattice defects which scatter electrons and, hence, break superconducting pairs. In order to elucidate the magnitude and temperature dependence of the magnetic penetration depth 
, we have performed 
SR measurements in the same PuCoGa single crystals after 25 and 400 days of aging. We found that 
decreased from 18.5K to 15K for the aged sample, yet a quasi-linear temperature dependence was found for the low-temperature 
in both the fresh and aged sample, consistent with 
-wave pairing symmetry. The magnitude of the muon spin relaxation rate 
in the aged sample, 
, where 
and 
are the superfluid density and the effective mass, respectively, is reduced by about 70% compared to fresh sample. This indicates that the scattering from self-irradiation induced defects is not in the limit of the conventional Abrikosov-Gor'kov pair-breaking theory, but rather in the limit of short coherence length (about 2nm in PuCoGa) superconductivity.
-Pu metal using muon spin relaxationHeffner, R. H.; Oishi, Kazuki; Fluss, M. J.*; Morris, G. D.*; MacLaughlin, D. E.*; Shu, L.*; Chung, B. W.*; McCall, S. K.*; Bauer, E. D.*; Sarrao, J. L.*; et al.
Journal of Alloys and Compounds, 444-445, p.80 - 83, 2007/10
Times Cited Count：8 Percentile：48.54(Chemistry, Physical)We summarize the results of muon spin relaxation (SR) measurements carried out in
- and -Pu and in the superconducting state ofPuCoGa. In Pu metal, interest has centered on whether or not magnetic order exists in the hightemperature fcc phase,The Pu metal studies were designed to search for evidence of magnetic ordering, andhave set the most stringent limits to date for the ordered moment. In PuCoGa the temperature dependence of themagnetic penetration depth (T) was investigated in a fresh sample and again in the same sampleafter 400 days of aging. We find (T)
T for T 
Tc/2, indicating a line of nodes in thesuperconducting order parameter. Remarkably, the temperature dependence of (T) is littlechanged even after significant radiation damage.
Oishi, Kazuki; Heffner, R. H.; Morris, G. D.*; Bauer, E. D.*; Graf, M. J.*; Zhu, J.-X.*; Morales, L. A.*; Sarrao, J. L.*; Fluss, M. J.*; MacLaughlin, D. E.*; et al.
Physical Review B, 76(6), p.064504_1 - 064504_10, 2007/08
Times Cited Count：13 Percentile：51.77(Materials Science, Multidisciplinary) probed by muon spin rotationOishi, Kazuki; Heffner, R. H.; Morris, G. D.*; Fluss, M. J.*; Bauer, E. D.*; Morales, L. A.*; Sarrao, J. L.*; MacLaughlin, D. E.*; Shu, L.*; Ito, Takashi; et al.
Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.566 - 568, 2007/03
no abstracts in English
SR studies of Pu metal and the Pu-based superconductor PuCoGaHeffner, R. H.; Bauer, E. D.*; Chung, B.*; Fluss, M. J.*; Higemoto, Wataru; Ito, Takashi; MacLaughlin, D. E.*; Morales, L. A.*; Morris, G. D.*; Oishi, Kazuki; et al.
Journal of the Physical Society of Japan, 75(Suppl.), p.14 - 19, 2006/08
no abstracts in English
-Pu and Ga-stabilized -PuHeffner, R. H.; Morris, G. D.*; Fluss, M. J.*; Chung, B.*; MacLaughlin, D. E.*; Shu, L.*; Anderson, J. E.*
Physica B; Condensed Matter, 374-375, p.163 - 166, 2006/03
Times Cited Count：8 Percentile：38.44(Physics, Condensed Matter)The SR measurements in pulutonium metals are reported for the first time. The ground-state properties of Pu metal is not understood clearly. We found the upper limits of the ordered moment in -Pu and -stabilized Pu is 
at 
4K.
SR studies of the superconducting order parameter in PuCoGaMorris, G. D.*; Heffner, R. H.; Bauer, E. D.*; Morales, L. A.*; Sarrao, J. L.*; Fluss, M. J.*; MacLaughlin, D. E.*; Shu, L.*; Anderson, J. E.*
Physica B; Condensed Matter, 374-375, p.180 - 183, 2006/03
Times Cited Count：15 Percentile：56.29(Physics, Condensed Matter)Heffner, R. H.; Morris, G. D.*; Fluss, M. J.*; Chung, B.*; McCall, S.*; MacLaughlin, D. E.*; Shu, L.*; Oishi, Kazuki; Bauer, E. D.*; Sarrao, J. L.*; et al.
Physical Review B, 73(9), p.094453_1 - 094453_5, 2006/03
Times Cited Count：33 Percentile：77.14(Materials Science, Multidisciplinary)no abstracts in English
probed by muon spin rotationOishi, Kazuki; Heffner, R. H.; Higemoto, Wataru; Ito, Takashi; Morris, G. D.*; Bauer, E. D.*; Morales, L. A.*; Sarrao, J. L.*; Fluss, M. J.*; MacLaughlin, D. E.*; et al.
no journal, ,
The discovery of the first Pu-based superconductor PuCoGa
(
= 18.5 K) demonstrates the rich and complex nature of Pu-based materials. The mechanism of the superconductivity in PuCoGa is still under investigation, though recent experiments and theory suggest a magnetic origin. For example, the electronic structure of this material was investigated theoretically, and spin-fluctuation mediated superconductivity was suggested. NMR results also suggest that the superconducting order parameter of this Pu-based superconductor has d-wave symmetry. We note that Pu is a radioactive nucleus (Pu, = 24000 years), thus PuCoGa suffers self-induced radiation damage. Previous SR results performed at 600 Oe in a 25-day old single crystalline sample show a linear temperature dependence for the muon spin relaxation rate (
, : magnetic penetration depth) for 
0.5, suggesting d-wave pairing symmetry. We have performed SR experimentes on the same sample after 400 days of aging in order to obtain more detailed information on the order parameter, i.e., T-dependence of at several magnetic fields, as well as the effects of aging. We found that Tc decreased from 18.5 K to 15 K for the 25-day and 400-day samples, respectively, yet the linear temperature dependence remains, consistent with a line of nodes (and suggesting d-wave pairing symmetry). These results indicate that the temperature dependence of does not depend on accumulated radiation damage over the span of time measured.
SR measurements on the superconducting penetration depth in aged PuCoGaHeffner, R. H.; Oishi, Kazuki; Higemoto, Wataru; Ito, Takashi; Morris, G. D.*; Fluss, M. J.*; MacLaughlin, D. E.*; Shu, L.*; Bauer, E. D.*; Sarrao, J. L.*
no journal, ,
The superconductor PuCoGa possesses a relatively high critical temperature (T
= 18.5 K), a moderate mass enhancement (Sommerfeld coefficient 
80 mJ/mol-K
and exhibits behavior consistent with spin-fluctuation-induced d-wave superconductivity. It is also radioactive, with its dominant radioisotope Pu having a half-life of 2.4 
10
yrs. We report 
SR measurements of the temperature and field dependence of the magnetic field penetration depth 
(T,H) in a 400 day-old sample of PuCoGa (T = 15 K), and compare these results to data obtained on the same sample approximately one year earlier. In 600 Oe applied field both measurements show a linear low-temperature behavior for (T) - (0) = bT for T/T
0.5 with the same coefficient b. The magnitude of (0) in the aged sample has increased by a factor of about 1.8. The results are discussed in terms of the effects of radiation damage on the postulated d-wave superconducting order parameter.
Heffner, R. H.; Oishi, Kazuki; Higemoto, Wataru; Ito, Takashi; Morris, G. D.*; Bauer, E. D.*; Graf, M. J.*; Sarrao, J. L.*; Fluss, M. J.*; MacLaughlin, D. E.*; et al.
no journal, ,
no abstracts in English
