Magnetism of actinide compounds

Santini, P.; Lemański, R.; Erdös, Paul

doi:10.1080/000187399243419

Cited by 154 publications

(123 citation statements)

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“…Although PuO 2 is known to be an insulator [36], its ground state was reported experimentally to be an antiferromagnetic phase [37]. For PuO 2 , at U = 0, the ground state was a ferromagnetic metal, which is different from experimental results.…”

Section: Variation Of U With Calculation Methods and Parameterscontrasting

confidence: 55%

The DFT+U: Approaches, Accuracy, and Applications

Tolba¹,

Gameel²,

Ali³

et al. 2018

Density Functional Calculations - Recent Progresses of Theory and Application

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This chapter introduces the Hubbard model and its applicability as a corrective tool for accurate modeling of the electronic properties of various classes of systems. The attainment of a correct description of electronic structure is critical for predicting further electronic-related properties, including intermolecular interactions and formation energies. The chapter begins with an introduction to the formulation of density functional theory (DFT) functionals, while addressing the origin of bandgap problem with correlated materials. Then, the corrective approaches proposed to solve the DFT bandgap problem are reviewed, while comparing them in terms of accuracy and computational cost. The Hubbard model will then offer a simple approach to correctly describe the behavior of highly correlated materials, known as the Mott insulators. Based on Hubbard model, DFT+U scheme is built, which is computationally convenient for accurate calculations of electronic structures. Later in this chapter, the computational and semiempirical methods of optimizing the value of the Coulomb interaction potential (U) are discussed, while evaluating the conditions under which it can be most predictive. The chapter focuses on highlighting the use of U to correct the description of the physical properties, by reviewing the results of case studies presented in literature for various classes of materials.

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Section: Variation Of U With Calculation Methods and Parameterscontrasting

confidence: 55%

The DFT+U: Approaches, Accuracy, and Applications

Tolba¹,

Gameel²,

Ali³

et al. 2018

Density Functional Calculations - Recent Progresses of Theory and Application

View full text Add to dashboard Cite

show abstract

“…First, both the spin-orbit and the crystal-field interaction are very strong, on the order of magnitude of 1 eV. 12 Second, the interatomic exchange tends to be very low, severely limiting the finite-temperature anisotropy. The relative strengths of the crystal-field and spin-orbit couplings may be estimated from the orbital moment, whose magnitude scales as /A.…”

Section: D 4f and 5d Magnetsmentioning

confidence: 99%

“…The result of that progress have been uniaxial rare-earth transition-metal magnets exhibiting impressive overall hard-magnetic properties. The first decades of the 20th century saw the development of uniaxial 3d-based magnets, such as BaFe 12 O 19 , where K 1 ϭ0.33 MJ/m 3 . The first 1:5 permanent magnets, developed in the late 1960s, were YCo 5 magnets, 1 whose anisotropy is due to the extraordinarily strong easy-axis contribution of the Co atoms in the 1:5 structure.…”

Section: Introductionmentioning

confidence: 99%

Exchange-controlled magnetic anisotropy

Skomski

2002

Journal of Applied Physics

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The magnetocrystalline anisotropy of 5 f transition-metal atoms ͑actinides͒ is investigated. A simple model Hamiltonian reproduces the observed huge low-temperature anisotropy of cubic actinide compounds such as US and predicts the temperature dependence of the anisotropy. The dominance of the spin-orbit and crystal-field interactions means that the magnitude of the anisotropy is limited only by interatomic exchange. One consequence is that cubic and uniaxial 4 f magnets have similar magnitudes of the anisotropy and similar temperatures dependencies.

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“…In the localized regime, the hybridization can be considered as a perturbation and the corresponding perturbation theory tells us that the magnetic properties are dominated by the RKKY interaction. When the system approaches the mixed valence regime, there are at least two different possibilities: a) A paramagnetic Fermi liquid, where the absence of magnetic ordering is just a consequence of the Pauli exclusion principle (only a small fraction of the f -moment is screened by the conduction electrons) [7]; and b) A partially polarized FM metal (see also [5,6]) The existence of this second scenario as a possible solution of the PAM provides a natural explanation for a number of U (US, USe, UTe [21], URu 2−x M x Si 2 with M = Re, Tc and Mn [22] [12]) materials which exhibit the coexistence of ferromagnetism and Kondo behavior.…”

Section: B) Virtual States Lowest Energymentioning

confidence: 99%

Ferromagnetism in the strong hybridization regime of the periodic Anderson model

2003

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We determine exactly the ground state of the one-dimensional periodic Anderson model (PAM) in the strong hybridization regime. In this regime, the low energy sector of the PAM maps into an effective Hamiltonian that has a ferromagnetic ground state for any electron density between half and three quarters filling. This rigorous result proves the existence of a new magnetic state that was excluded in the previous analysis of the mixed valence systems.Rigorous results, numerical and analytic, have greatly aided the study of strongly correlated electrons systems. Unfortunately, few such results exist. The numerical renormalization group and Bethe ansatz solutions of the single impurity Anderson and Kondo models are perhaps the best examples of a solid numerical approach and exact solution of simple models that changed and solidified the thinking in what was a highly controversial and puzzling problem area. Another important result was the rigorous connection between the two models established by Schrieffer and Wolff [1]. Their work showed that the low lying energy spectrum of the Anderson model in the strong coupling and weak hybridization limit (U/t ≫ 1 and V ≪ |E F −ǫ f |) can be mapped into the Kondo model in the weak coupling regime (J/t ≪ 1).For dense systems, the natural extensions of the impurity models are the periodic Anderson (PAM) and Kondo lattice (KLM) models. For these, numerical renormalization group and Bethe Ansatz solutions are lacking even in one-dimension. In addition, very few rigorous results are available for the PAM [2,3]. What remains true however is the connection between the strong and weak coupling limits via a natural extension of the Schrieffer-Wolff transformation.There are two basic questions one can ask about these lattice models: what is their relevance to real materials and in what other parameter regimes might their physics be connected? In several well known papers, Doniach [4], at least implicitly, made several assumptions about the answers to both questions and proposed the now standard picture of the magnetic properties of f-electron materials that portrays a competition between the RKKY magnetic interaction which is obtained from a fourth order expansion in the hybridization and the Kondo exchange.The reasoning behind this intuitively appealing picture is something like the following: From the Schrieffer-Wolff perturbation theory, the Kondo exchange coupling is related to the parameters in the PAM via J ≈ |V | 2 /|E F − ǫ f |. In the PAM, a mixed valence regime corresponds to positioning the f-electron orbitals in the conduction band near the Fermi energy, i.e., |E F − ǫ f | ≈ 0. In this regime, the Schrieffer-Wolff result suggests the Kondo exchange is strong and thus can lead to a complete compensation of the f-moments by one or more of the conduction band electrons. Implied in this line of reasoning there are two important assumptions [4]: I) The strong coupling limit of the KLM is connected to the mixed valence regime (for weak hybridzation |V | ≪ |t|) of the PAM, and II)...

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Magnetism of actinide compounds

Cited by 154 publications

References 0 publications

The DFT+U: Approaches, Accuracy, and Applications

The DFT+U: Approaches, Accuracy, and Applications

Exchange-controlled magnetic anisotropy

Ferromagnetism in the strong hybridization regime of the periodic Anderson model

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