Magnetic properties of the two allotropic phases of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Pu</mml:mi><mml:msub><mml:mi mathvariant="normal">Ga</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Boulet, Pascal; Colineau, E.; Wastin, F.; Javorský, P.; Griveau, J.‐C.; Rébizant, J.; Stewart, G. R.; Bauer, E. D.

doi:10.1103/physrevb.72.064438

Cited by 25 publications

(40 citation statements)

References 30 publications

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“…The (T) for ␦-Pu is more complex, although still dominated by a Pauli term, with the magnetic susceptibility increasing Ͻ10% when cooled from 350 K and from 2 K. There are several features in the (T) plot: a low-temperature Curie tail attributable to the same impurities observed in the ␣-Pu sample and a small peak at Ϸ33 K, likely attributable to second phases of PuGa 3 and PuGa 2 at the level of a few hundred ppm (25,26). If these second phases rise to a concentration of order 0.1%, which could result from incomplete homogenization of the Ga, they would fully account for the gentle slope observed for T Ͼ 40 K. This slope also is consistent with previous observations of Ga-stabilized ␦-Pu (27), which did not extend to sufficiently low temperatures to rule out second phases.…”

Section: Resultsmentioning

confidence: 94%

Emergent magnetic moments produced by self-damage in plutonium

McCall

Fluss

Chung

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Plutonium possesses the most complicated phase diagram in the periodic table, driven by the complexities of overlapping 5f electron orbitals. Despite the importance of the 5f electrons in defining the structure and physical properties, there is no experimental evidence that these electrons localize to form magnetic moments in pure Pu. Instead, a large temperature-independent Pauli susceptibility indicates that they form narrow conduction bands. Radiation damage from the ␣-particle decay of Pu creates numerous defects in the crystal structure, which produce a significant temperature-dependent magnetic susceptibility, (T), in both ␣-Pu and ␦-Pu (stabilized by 4.3 atomic percent Ga). This effect can be removed by thermal annealing above room temperature. By contrast, below 35 K the radiation damage is frozen in place, permitting the evolution in (T) with increasing damage to be studied systematically. This result leads to a two-component model consisting of a Curie-Weiss term and a short-ranged interaction term consistent with disorder-induced local moment models. Thus, it is shown that self-damage creates localized magnetic moments in previously nonmagnetic plutonium.disorder ͉ magnetism ͉ radiation damage A mong the interesting properties of plutonium is a complex phase diagram, which at ambient pressure exhibits six distinct solid-state phases below the melting temperature. These phases are narrowly spaced in energy, with the five lowest-energy phases separated by Ͻ2 mRyd, placing them on a molecularenergy scale as compared with the more typical 10-20 mRyd scale typical of metals such as neighboring Np and Am (1). Although there is no theoretical consensus as to the origin of the low-density fcc ␦-phase of Pu (1-7), there is an understanding that the organization of the spin and orbital moments play a key role in stabilizing this phase. The lack of significant magnetic moments is a central issue among theorists and inspired a recent experimental review (8) painstakingly describing the evidence against the existence of magnetic moments in plutonium. Recent SR ϩ studies for ␣-and ␦-phase Pu further support this absence of magnetic moments, placing the upper bound on frozen moments at 0.001 Bohr magneton ( B ) (9). However, all solid Pu phases possess large magnetic susceptibilities, suggesting they border on becoming magnetic. Consistent with this observation and general predictions of narrow 5f bands in plutonium are large electronic contributions to the specific heat in both ␣-Pu and alloy-stabilized ␦-Pu, qualifying each as a highly correlated electron system (10).Often, local magnetic moments can be induced in nearly magnetic systems by imposing a suitable perturbation. One such method is to increase disorder by introducing a low concentration of impurities via chemical substitution. For example, when very dilute quantities of Fe, Co, or Ni are doped into nonmagnetic Pd, they induce remarkably large magnetic moments by polarizing the surrounding lattice (11,12). Similarly, one-half atomic percent (at. %) Pu do...

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Section: Resultsmentioning

confidence: 94%

Emergent magnetic moments produced by self-damage in plutonium

McCall

Fluss

Chung

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…-Polycristalline samples were synthesized by arc melting and single crystals were grown in Ga flux. The precise operational mode of the synthesis is described in [7]. DC-magnetisation measurements have been performed on a Quantum Design SQUID magnetometer from 2 to 300 K in magnetic fields up to 7 T. Electrical resistivity was measured by a Quantum Design PPMS-9 over the range 1.8 -300 K in magnetic fields up to 9 T. All measurements are performed on encapsulated samples to avoid radioactive contamination.…”

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confidence: 99%

Role of self-irradiation defects on the ageing of ²³⁹ PuCoGa ₅

Jutier¹,

Griveau²,

Beek³

et al. 2007

Europhys. Lett.

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Abstract. -Low temperature accumulation and annealing experiments, in conjunction with electrical resitivity and critical current density measurements, are used to study the ageing of the actinide superconductor PuCoGa5. These measurements reveal that 2-nm sized nonsuperconducting point-like regions are the main damage formed during room temperature ageing; smaller point like defects are irrelevant to transport properties. Defect sizes and densities deduced from experiment agree with Transmission Electron Microscopy observations.

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“…There are several features in the χ(T) plota low temperature Curie tail due to the same impurities observed in the α−Pu sample, and a small peak at ~33K, likely due to second phases of PuGa 3 and PuGa 2 at the level of a few hundred ppm [32,33]. If these second phases rise to a concentration of order 0.1%, which could result from incomplete homogenization of the Ga, they would fully account for the gentle slope observed for T>40K.…”

Section: Plutonium Resultsmentioning

confidence: 99%