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Journal Articles

Suppression of time-reversal symmetry breaking superconductivity in Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$ and Pr$$_{1-y}$$La$$_y$$Os$$_4$$Sb$$_{12}$$

Shu, L.*; Higemoto, Wataru; Aoki, Yuji*; Hillier, A. D.*; Oishi, Kazuki*; Ishida, Kenji*; Kadono, Ryosuke*; Koda, Akihiro*; Bernal, O. O.*; MacLaughlin, D. E.*; et al.

Physical Review B, 83(10), p.100504_1 - 100504_4, 2011/03

 Times Cited Count:28 Percentile:75.21(Materials Science, Multidisciplinary)

Zero-field muon spin relaxation experiments have been carried out in the Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$ and Pr$$_{1-y}$$La$$_y$$Os$$_4$$Sb$$_{12}$$ alloy systems to investigate broken time-reversal symmetry (TRS) in the superconducting state, signaled by the onset of a spontaneous static local magnetic field B$$_s$$. In both alloy series B$$_s$$ initially decreases linearly with solute concentration. Ru doping is considerably more efficient than La doping, with a 50% faster initial decrease. The data suggest that broken TRS is suppressed for Ru concentration $$xgeq$$0.6 but persists for essentially all La concentrations. Our data support a crystal-field excitonic cooper pairing mechanism for TRS-breaking superconductivity.

Journal Articles

Novel features in filled skutterudites containing rare-earth elements with a plural number of 4f-electrons

Sato, Hideyuki*; Aoki, Yuji*; Kikuchi, Daisuke*; Sugawara, Hitoshi*; Higemoto, Wataru; Oishi, Kazuki; Ito, Takashi; Heffner, R. H.; Saha, S. R.*; Koda, Akihiro*; et al.

Physica B; Condensed Matter, 404(5-7), p.749 - 753, 2009/04

 Times Cited Count:4 Percentile:22.79(Physics, Condensed Matter)

Wide varieties of strongly correlated electron phenomena are performed on the stage of a filled skutterudite structure. Especially when one of the players contains a plural number of 4f electrons, the orbital degrees of freedom play a major role as a new type of nonmagnetic and/or weak-magnetic phenomena. Several examples found in Pr- and Sm-based filled skutterudites are introduced in relation to muon spin relaxation experiments.

Journal Articles

Influence of self-irradiation on the magnitude of the superfluid density in PuCoGa$$_5$$ probed by muon spin rotation

Oishi, 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$$_5$$ has attracted much interest because it is the first Pu-based superconductor, having an order of magnitude higher transition temperature $$T_{rm c}=18.5$$K than the isostructural heavy fermion superconductor CeCoIn$$_5$$ ($$T_{rm c}=2.3$$K). The mechanism of the superconductivity in PuCoGa$$_5$$ 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 ($$^{239}$$Pu, $$T^{1/2}$$ = 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 $$lambda$$, we have performed $$mu$$SR measurements in the same PuCoGa$$_5$$ single crystals after 25 and 400 days of aging. We found that $$T_{rm c}$$ decreased from 18.5K to 15K for the aged sample, yet a quasi-linear temperature dependence was found for the low-temperature $$lambda(T)$$ in both the fresh and aged sample, consistent with $$d$$-wave pairing symmetry. The magnitude of the muon spin relaxation rate $$sigma$$ in the aged sample, $$sigmapropto 1/lambda^2proptorho_s/m^*$$, where $$rho_s$$ and $$m^*$$ 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$$_5$$) superconductivity.

Journal Articles

$$mu$$SR study of the effects of Ce dilution on the development of the heavy-fermion state in (Ce,La)$$_2$$IrIn$$_8$$

Oishi, Kazuki; Heffner, R. H.; Ito, Takashi; Higemoto, Wataru; Morris, G. D.*; Hur, N.*; Bauer, E. D.*; Sarrao, J. L.*; Thompson, J. D.*; MacLaughlin, D. E.*; et al.

Journal of Physics and Chemistry of Solids, 68(11), p.2068 - 2071, 2007/11

 Times Cited Count:2 Percentile:13.7(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

The Search for magnetic order in $$delta$$-Pu metal using muon spin relaxation

Heffner, 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:51.29(Chemistry, Physical)

We summarize the results of muon spin relaxation ($$mu$$SR) measurements carried out in$$alpha$$- and $$delta$$-Pu and in the superconducting state ofPuCoGa$$_5$$. In Pu metal, interest has centered on whether or not magnetic order exists in the hightemperature fcc $$delta$$ 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$$_5$$ the temperature dependence of themagnetic penetration depth $$lambda$$(T) was investigated in a fresh sample and again in the same sampleafter 400 days of aging. We find $$lambda$$(T)$$propto$$ T for T $$<$$ Tc/2, indicating a line of nodes in thesuperconducting order parameter. Remarkably, the temperature dependence of $$lambda$$(T) is littlechanged even after significant radiation damage.

Journal Articles

Muon spin rotation measurements of the superfluid density in fresh and aged superconducting PuCoGa$$_5$$

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:53.86(Materials Science, Multidisciplinary)

Journal Articles

Muon spin relaxation and hyperfine-enhanced $$^{141}$$Pr nuclear spin dynamics in Pr(Os,Ru)$$_4$$Sb$$_{12}$$ and (Pr,La)Os$$_4$$Sb$$_{12}$$

Shu, L.*; MacLaughlin, D. E.*; Aoki, Yuji*; Tsunashima, Yoshino*; Yonezawa, Yuki*; Sanada, Shotaro*; Kikuchi, Daisuke*; Sato, Hideyuki*; Heffner, R. H.; Higemoto, Wataru; et al.

Physical Review B, 76(1), p.014527_1 - 014527_8, 2007/07

 Times Cited Count:20 Percentile:65.43(Materials Science, Multidisciplinary)

Journal Articles

The Unconventional superconductivity of skutterudite PrOs$$_4$$Sb$$_{12}$$; Time-reversal symmetry breaking and adjacent field-induced quadrupole ordering

Aoki, Yuji*; Tayama, Takashi*; Sakakibara, Toshiro*; Kuwahara, Keitaro*; Iwasa, Kazuaki*; Kogi, Masafumi*; Higemoto, Wataru; MacLaughlin, D. E.*; Sugawara, Hitoshi*; Sato, Hideyuki*

Journal of the Physical Society of Japan, 76(5), p.051006_1 - 051006_13, 2007/05

 Times Cited Count:60 Percentile:59.09(Physics, Multidisciplinary)

This review presents a summary and evaluation of the experimental properties of unconventional superconductivity in PrOs$$_4$$Sb$$_{12}$$. After a brief introduction of filled skutterudites, we argue that the normal-state properties of PrOs$$_4$$Sb$$_{12}$$ are quite different from ordinary heavy-fermion superconductors.

Journal Articles

Magnetic penetration depth and self-induced irradiation effects in superconducting PuCoGa$$_5$$ probed by muon spin rotation

Oishi, 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

Journal Articles

Two-fluid model of heavy fermion formation and $$mu$$SR knight shift measurements in UBe$$_{13}$$

Heffner, R. H.; MacLaughlin, D. E.*; Sonier, J. E.*; Fundley, M. F.*; Thompson, J. D.*

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e6 - e8, 2007/03

Recently phenomenological picture of the formation of the heavy femion state was put forward in terms of a two-component susceptibility, one component corresponding to non-interacting local moments and second, low-temperature component associated with onset of heavy fermation state (so-called "two-fluid" model). This phenomenology can be studied by measuring the local susceptibility via $$mu$$SR Knight shift measurements. Normally, the Knight shift is proposional to the bulk susceptibility. The onset of second component appears as a deviation in the linear relation. Previously we discovered a non-linear relation in U$$_{1-x}$$Th$$_{x}$$Be$$_{13}$$, which was interpreted in terms of a temperature-dependent hyperfine field. Here we reexamine these data in terms of the two-fluid model. Our analysis shows that these date are consistent with the scaling law proposed. The $$mu$$SR data are discussed in terms of related changes in the resistivity and the NMR relaxation rates in these systems.

Journal Articles

Time reversal symmetry breaking in superconducting (Pr,La)Os$$_4$$Sb$$_{12}$$ and Pr(Os,Ru)$$_4$$Sb$$_{12}$$

Shu, L.*; Higemoto, Wataru; Aoki, Yuji*; Frederick, N. A.*; Yuhasz, W. M.*; Heffner, R. H.; Oishi, Kazuki; Ishida, Kenji*; Kadono, Ryosuke*; Koda, Akihiro*; et al.

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.551 - 553, 2006/11

Journal Articles

$$mu$$SR studies of Pu metal and the Pu-based superconductor PuCoGa$$_5$$

Heffner, 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

Journal Articles

New limits on the ordered moments in $$alpha$$-Pu and Ga-stabilized $$delta$$-Pu

Heffner, 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:40.24(Physics, Condensed Matter)

The $$mu$$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 $$alpha$$-Pu and $$delta$$-stabilized Pu is $$<10^{-3}mu_B$$ at $$sim$$4K.

Journal Articles

$$mu$$SR studies of the superconducting order parameter in PuCoGa$$_5$$

Morris, 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:58.07(Physics, Condensed Matter)

Journal Articles

Evolution of the heavy fermion state in Ce$$_2$$IrIn$$_8$$

Heffner, R. H.; Morris, G. D.*; Bauer, E. D.*; Sarrao, J. L.*; Thompson, J. D.*; MacLaughlin, D. E.*; Shu, L.*

Physica B; Condensed Matter, 375-375, p.184 - 187, 2006/03

 Times Cited Count:6 Percentile:32.73(Physics, Condensed Matter)

Journal Articles

Critical slowing down in the geometrically frustrated pyrochlore antiferromagnet Gd$$_2$$Ti$$_2$$O$$_7$$

MacLaughlin, D. E.*; Rose, M. S.*; Anderson, J. E.*; Shu, L.*; Heffner, R. H.; Kimura, Tsuyoshi*; Morris, G. D.*; Bernal, O. O.*

Physica B; Condensed Matter, 374-375, p.142 - 144, 2006/03

 Times Cited Count:3 Percentile:18.82(Physics, Condensed Matter)

Longitudinal-field muon spin relaxation experiments have been carried out in the paramagnetic state of single-crystal Gd$$_2$$Ti$$_2$$O$$_7$$ just above the phase transition. At high applied fields the relaxation time is proportional to field. At low fields the relaxation rate increases markedly as the freezing temperature is approached. This behavior is consistent with the very long autocorrelation function cutoff time.

Journal Articles

Susceptibility inhomogeneity and non-Fermi liquid behavior in UCu$$_{5-x}$$Pt$$_x$$

MacLaughlin, D. E.*; Rose, M. S.*; Bernal, O. O.*; Heffner, R. H.; Nieuwenhuys, G. J.*; Chau, R.*; Maple, M. B.*

Physica B; Condensed Matter, 374-375, p.174 - 176, 2006/03

 Times Cited Count:0 Percentile:0(Physics, Condensed Matter)

Transverse-field $$mu$$SR shifts and relaxation rates have been measured in the non-Fermi liquid alloy system UCu$$_{5-x}$$Pt$$_x$$. At low temperatures the fractional spread in Knight shifts is 2 for x=1, but is only half this value for x=1.5 and 2.5. In a disorder-driven scenario where the NFL behavior is due to a broadly distributed characteristic energy E, our results indicate that $$delta$$E/E$$_{av}sim(delta$$K/K)$$_{Trightarrow 0}$$ is similar for UCu$$_{5-x}$$Pd$$_x$$. Our results correlate with the observed suppression of other NFL anomaliess.

Journal Articles

Effect of annealing on glassy dynamics and non-Fermi liquid behavior in UCu$$_4$$Pd

MacLaughlin, D. E.*; Rose, M. S.*; Anderson, J. E.*; Bernal, O. O.*; Heffner, R. H.; Nieuwenhuys, G. J.*; Baumbach, R. E.*; Butch, N. P.*; Maple, M. B.*

Physica B; Condensed Matter, 374-375, p.177 - 179, 2006/03

 Times Cited Count:1 Percentile:7.01(Physics, Condensed Matter)

Longitudinal-field $$mu$$SR experiments have been performed in unannealed and annealed samples of the heavy-fermion compound UCu$$_4$$Pd to study the effect of disorder on non-Fermi liquid behavior in this material. The observed scaling exponent independent of annealing. Annealed samples exhibited a reduction of the relaxation rate at low temperatures, indicating that annealing shifts fluctuation noise power to higher frequencies. There was no tendency of the inhomogeneous spread in rates to decrease with annealing. The correlation with residual resistivity previously observed for a number of NFL heavy-electron materials is also found in the present work.

Journal Articles

Limits for ordered magnetism in Pu from muon spin rotation spectroscopy

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:78.73(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Spin freezing and non-glassy dynamics in Ce$$_{0.2}$$La$$_{0.8}$$RhIn$$_5$$

MacLaughlin, D. E.*; Shu, L.*; Anderson, J. E.*; Heffner, R. H.; Morris, G. D.*; Bernal, O. O.*; Kim, J. S.*; Stewart, G. R.*

Physica B; Condensed Matter, 378-380, p.144 - 145, 2006/02

 Times Cited Count:0 Percentile:0(Physics, Condensed Matter)

28 (Records 1-20 displayed on this page)