The dual nature of 5f electrons and the origin of heavy fermions in U compounds

Zwicknagl, Gertrud; Fulde, Peter

doi:10.1088/0953-8984/15/28/302

Cited by 80 publications

(64 citation statements)

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“…Two sharp narrow peaks are due to f 5/2 and f 7/2 states. The remaining one may be interpreted in terms of the dual character of 5f electrons in uranium [7]. (737) The Zn 3d electrons are localised in the energy range from about −0.55 Ry to −0.4 Ry below the Fermi level, as illustrated in Fig.…”

Section: Resultsmentioning

confidence: 99%

Positron Annihilation Study of Defects in the Cage-Type Uranium Compound

Rubaszek

2014

Acta Phys. Pol. A

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The electron and positron properties of the UIr2Zn20 compound of the F d-3m cage-type crystal structure are studied. The characteristics for the perfect crystal are compared with their counterparts in the elements containing Ir and Zn vacancy. The presence of the vacancy hardly inuences the electron charge density around individual atoms. In contrast to electrons, the positron is strongly localized inside the vacancy and the transfer of positron charge is observed. The positron lifetime, τ , appears to be strongly sensitive to the presence and type of the vacancy. Furthermore, this parameter calculated for the perfect crystal is very close to the experimental value for Zn. Here the theoretical values of τ depend on the approach applied to the electron positron (ep) correlations.

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Section: Resultsmentioning

confidence: 99%

Positron Annihilation Study of Defects in the Cage-Type Uranium Compound

Rubaszek

2014

Acta Phys. Pol. A

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“…[15] from the Steglich group have tried to describe (unsuccessfully) these excitations as due to the 5f 2 configuration. Fulde and Zwicknagl [6,7], after this experimental result, have changed their mind coming out then with a theoretical model with the dual nature of f electrons in UPd 2 Al 3 on basis of the 5f 2 configuration. In their theoretical considerations they use only two (of all 9 levels of the lowest 3 H 4 multiplet) lowest singlet-states, Γ 3 and Γ 4 , separated by 7 meV.…”

Section: Upd 2 Almentioning

confidence: 99%

“…The main point of the debate is related to the understanding of the role played by f electrons -they are localized or itinerant, or more exactly how many f electrons are localized or itinerant [2][3][4][5][6][7][8][9][10][11]. The itinerant nature of the U 5f electrons in UGe 2 has been arguing, basing on, apart of photoemission experiments, the relatively small ordered moment in the ferromagnetic phase in comparison to the almost full effective moment seen in the paramagnetic phase, say above 150 K [4,10,11].…”

Section: Introductionmentioning

confidence: 99%

“…In the theoretical band calculations the 5f electrons are considered as itinerant [4][5][6][7][8][9][10][11] whereas surprisingly nice reproduction of many experimental results can be obtained within the crystal-field (CEF) approach [1,2,[12][13][14], i.e. treating well-defined integer number f electrons as localized.…”

Section: Introductionmentioning

confidence: 99%

“…Zwicknagl et al [6,7] came out with a model with a dual nature of f electrons, in which they consider two f electrons as localized and the third f electron to be largely itinerant.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Three Localized f Electrons in UPd₂Al₃and in UGe₂Intermetallics

Radwański

Nalecz

Ropka³

2016

Acta Phys. Pol. A

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We have calculated the strength of the excitations between the crystal-field states which are in agreement with inelastic-neutron-scattering results. This agreement confirms the existence in the heavy-fermion superconductor UPd2Al3 the crystal-field electronic structure being the finger-print of the U 3+ ions with three localized f electrons forming strongly-correlated atomic-like quantum system 5f 3 . The ionic integrity and the low-energy crystal-field electronic structure is preserved in this metallic system in the meV scale as has been postulated in the Quantum Atomistic Solid State theory (QUASST). We provide preliminary results with the U 3+ ion in UGe2 showing the ground-state eigenfunction which reproduces the ordered magnetic-moment value of 1.48 µB. This moment is composed from the dominant orbital contribution (2.6 µB) and the opposite spin moment (1.12 µB).

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Localization‐vs‐Delocalization of 5f Orbitals in Superatom Systems

Jiang

Wang

2018

Advcd Theory and Sims

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A long-standing debate on the system containing the actinide element is the extent of localization and participation of the 5f orbitals in chemical bonding across the actinide series. Here, we illuminate that the 5f orbitals have both dual nature in superatomic bonding for protactinium, uranium, neptunium, and plutonium using density functional theory. Electronic structure analysis reveals that the partial 5f electrons are active and could be preferentially excited to 6d shells to satisfy jelliumic bonding of the 18-electron rule (1S 2 1P 6 1D 10 ). In contrast, the extra 5f electrons are more localized for neptunium and plutonium compared with protactinium and uranium, and present antiferromagnetic and ferromagnetic couplings for the spin arrangements between actinide atoms and confined gold clusters, and largely localized at the actinide atom. This work offers not only a new recipe for breeding magnetic superatoms, but also is very promising for the designing of superconducting materials and heavy-fermion systems.For a long time, substantial attention has been focused on systems containing the actinide (An) elements. [1][2][3][4] One of the main reasons is that the 5f orbitals can exhibit localization like the 4f orbitals in the lanthanide series, or delocalization (participation) like the d orbitals in the transition metals, or both in the chemical bonding. In fact, the competition has resulted in multiple complicated ground states and phases in compounds and alloy systems. [5,6] Currently, although the degree of localization of 5f electrons has been recognized as the dominant factor in determining the magnetic and electronic properties of the materials, [7,8] experimental methods for measuring the occupancy of 5f electron are still very unsuccessful though some exceptions exist. Therefore, an equally important task is to explore simplified superatomic models containing actinide elements to understand the origin of their properties and enhanced stability.Currently, there are a number of electron counting rules in cluster science that can be effectively utilized in the design and synthesis of materials. [9][10][11][12][13] Among them, 18-electron rule, which is a conceptual extension to the octet rule by the insertion of a metal element with d valence electrons into the closed shell s 2 p 6 (eight electrons), has been regarded as cornerstone for understanding and explaining the transition-metal (especially for the gold clusters) structural stability and physicochemical properties. [14,15] For example, the icosahedral W/Mo@Au 12 cluster was confirmed by theoretical [16] and experimental [17] works, which stability can be attributed to and the 18-electron rule and the strong relativistic effects. Furthermore, the study of M@Au n (M: metal atom of VIIA-IA group; n = 8-17) clusters have shown that at n = 14, the gold-covered bimetallic cluster can achieve the highest binding energy per atom and gap between highest occupied molecular orbital and lowest unoccupied molecular orbital. [18] Therefore, as an important al...

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The dual nature of 5f electrons and the origin of heavy fermions in U compounds

Cited by 80 publications

References 20 publications

Positron Annihilation Study of Defects in the Cage-Type Uranium Compound

Positron Annihilation Study of Defects in the Cage-Type Uranium Compound

Three Localized f Electrons in UPd₂Al₃and in UGe₂Intermetallics

Localization‐vs‐Delocalization of 5f Orbitals in Superatom Systems

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The dual nature of 5f electrons and the origin of heavy fermions in U compounds

Cited by 80 publications

References 20 publications

Positron Annihilation Study of Defects in the Cage-Type Uranium Compound

Positron Annihilation Study of Defects in the Cage-Type Uranium Compound

Three Localized f Electrons in UPd2Al3and in UGe2Intermetallics

Localization‐vs‐Delocalization of 5f Orbitals in Superatom Systems

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Three Localized f Electrons in UPd₂Al₃and in UGe₂Intermetallics