Magnetic properties of plutonium monoarsenide (original) (raw)

Conditions for magnetism in Pu systems

Journal of Magnetism and Magnetic Materials, 2007

Weakly paramagnetic character of d-Pu is preserved when Pu is doped by Am, which expands the crystal lattice. Specific-heat data show that the g-coefficient does not increase. Such behaviour can be understood on the basis of LSDA+U calculations, which yield invariably non-magnetic Pu state due to the proximity to the 5f 6 state. We suggest that a general condition for Pu magnetism is some degree of a hybridization with states of other elements in alloys and compounds, which allows for the reduction of the 5f count. r

69Ga NMR and magnetic susceptibility in δ-phase of Pu1−xGax (x=0.05, x=0.08) alloys

Journal of Nuclear Materials, 2009

Ga nuclear magnetic resonance spectra, line shifts ( 69 K) and nuclear spin-lattice relaxation rate 69 T À1 1 have been measured in the 20 years aged Pu 0.95 Ga 0.05 and in fresh prepared Pu 0.92 Ga 0.08 alloys, stabilized d-phase, at magnetic field of 9.4 T in the temperature range (10-500) K. The line shift and 69 T À1 1 are determined correspondingly by the static and fluctuating-in-time parts of the local magnetic field that originates in transferred hyperfine coupling the Ga nuclear spin with the nearest f-electron environment of more magnetic Pu.

Magnetic properties of ferromagnetic Pu2Pt3Si5

Journal of Alloys and Compounds, 2013

The structural, magnetic, and thermodynamic properties of new plutonium based compound, Pu 2 Pt 3 Si 5, are reported. Single crystals produced by a Sn-flux technique have been analyzed showing a ferromagnetic behavior at 58 K. Pu 2 Pt 3 Si 5 crystallizes in the U 2 Co 3 Si 5type orthorhombic Iabm structure (72) with atomic parameters a= 9.9226(2) Å, b= 11.4436(2) Å and c= 6.0148(1) Å. The effective ( eff~ 0.74  B) and saturated ( sat~ 0.32  B /Pu) moments as well as the linear Sommerfeld coefficient ( e~ 2 mJ.mol-1 .K-2 /Pu) could point towards 5f localization in this material.

Nature of non-magnetic strongly-correlated state in δ-plutonium

Europhysics Letters (EPL), 2006

The solid-state properties of most of elements are now well understood on the basis of quantum physics -with few exceptions, notably the element number 94, plutonium. For Pu, difficulties have been known for many years, hence the large number of studies, especially theoretical, of this mysterious element. Plutonium has six crystalline phases at ambient pressure, some of which are separated by unusual phase transitions (with large discontinuities in volume), exhibit negative thermal expansion coefficients, or form exotic low-symmetry structures 1,2 . The main challenge to explain these anomalous properties is that the characteristic ingredient of actinides, the 5f electronic states, are in the cross-over regime between the localized and delocalized (itinerant) behaviour in Pu 3,4 . The early part of the actinide series with the 5f states being itinerant, i.e. part of the metallic bond, culminates with Pu; starting with Am (Z = 95), the 5f states are localized, non-bonding, and resemble the 4f states in lanthanides. Both itinerant and localized regimes are well covered by existing theories, but they cannot be simply interpolated due to the importance of many-body electron correlations 5,6 . The fundamental problem for Pu is that theories of strongly correlated systems exhibit local magnetic moments (ordered or disordered), whereas experimental data in Pu demonstrate unambiguously their absence 7 . Standard band-structure calculations predict strong magnetism for different phases of Pu 8,4 , and local moments appear as a crucial ingredient for an adequate description of equilibrium lattice constants and bulk moduli 9,10 . Here we demonstrate the solution to this problem by including dynamical correlation effects; the spin-orbital fluctuations involving f 5 and f 6 configurations suppress the magnetism of plutonium, and result in a many-electron resonance near the Fermi level, in an agreement with high-resolution photoelectron spectra.

Theoretical confirmation of Ga-stabilized anti-ferromagnetism in plutonium metal

Journal of Nuclear Materials, 2014

The density-functional-theory model for plutonium metal is shown to be consistent with recent magnetic measurements that suggest anti-ferromagnetism in Pu-Ga alloys at low temperatures. The theoretical model predicts a stabilization of the face-centered-cubic (fcc, δ) form of plutonium in an anti-ferromagnetic configuration when alloyed with gallium. The ordered magnetic phase occurs because Ga removes the mechanical instability that exists for unalloyed δ-Pu. The cause of the Ga-induced stabilization is a combination of a lowering of the band (kinetic) and electrostatic (Coulomb) energies for the cubic relative to the tetragonal phase.

Density-functional investigation of magnetism in δ-Pu

Physical Review B, 2002

We present density-functional results of ␦-Pu obtained from three electronic-structure methods. These methods have their individual strengths and are used in combination to investigate the magnetic and crystal stability of ␦-Pu. An all-electron, full potential linear muffin-tin orbitals ͑FPLMTO͒ method, that includes corrections for spin-orbit coupling and orbital-polarization effects, predicts ␦-Pu to be an antiferromagnet at zero temperature with a volume and a bulk modulus in very good agreement with experiment. The site-projected magnetic moment is smaller than expected (ϳ1.5 B ) due to large cancellation of spin and orbital moments. These calculations also predict a mechanical instability of antiferromagnetic ͑AF͒ ␦-Pu. In addition, techniques based on the Korringa-Kohn-Rostoker ͑KKR͒ method within a Green's-function formalism and a projector augmented wave ͑PAW͒ method predict the same behavior of ␦-Pu. In order to study disordered magnetism in ␦-Pu, the KKR Green's-function technique was used in conjunction with the disordered local-moment model, whereas for the FPLMTO and PAW methods this was accomplished within the special quasirandom structure model. While AF ␦-Pu remains mechanically unstable at lower temperatures, paramagnetic ␦-Pu is stabilized at higher temperatures where disordered magnetic moments are present and responsible for the crystal structure, the low density, and the low bulk modulus of this phase.

Radiation Damage Effects on the Magnetic Properties of Pu(1-x)Amx (x=0.224)

MRS Proceedings

Pu(Am) is stable in the fcc δ-phase from a few atomic percent to nearly 80 atomic percent Am, expanding the average interatomic separation as the alloy concentration of Am increases. Both Pu and Am spontaneously decay by α-emission creating self-damage in the lattice in the form of vacancy-interstitial pairs and their aggregates. At sufficiently low temperatures, the damage is frozen in place, but can be removed by thermal annealing at sufficiently high temperatures, effectively resetting the system to an undamaged condition. The magnetic susceptibility and magnetization are observed to increase systematically as a function of accumulated damage in the fcc δ-Pu(1-x)Am(x) (x=0.224). Some results of these observations are reported here.