Electron Correlation in Ferromagnetism. II. Hybridization of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>s</mml:mi></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>d</mml:mi></mml:math>Bands

Kishore, R.; Joshi, S. K.

doi:10.1103/physrevb.2.1411

Cited by 48 publications

(12 citation statements)

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“…It can be shown in the following way: if one generalizes Hamiltonian (1) by taking into account the interatomic exchange interaction in the mean-field approximation one obtains incorrect equations for magnetization and Curie temperature in the noted approximations. In particular, for the Curie temperature one obtains (in this connection see [32,33]) the expression…”

Section: Introductionmentioning

confidence: 99%

Ground State Ferromagnetism in a Generalized Hubbard Model With Strong Correlations

Didukh¹,

Kramar²

2003

Condens. Matter Phys.

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The present paper considers the ground state ferromagnetic ordering in a generalized Hubbard model with correlated hopping and interatomic exchange interaction in the case of strong correlations at non-integer band filling. The quasi-particle energy spectrum is obtained by means of a generalized mean-field approximation. The ground state energy of the system and the condition of ferromagnetic state realization are calculated. The dependences of magnetization on energy parameters and band-filling are obtained.

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Section: Introductionmentioning

confidence: 99%

Ground State Ferromagnetism in a Generalized Hubbard Model With Strong Correlations

Didukh¹,

Kramar²

2003

Condens. Matter Phys.

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“…In order to simplify this calculation, we use the homothetic band approximation 29 to treat the two subbands of the model. In this approximation, the dispersion relation of the wide subband is adopted as a model ( k c ϭ k ), and the other one, corresponding to the narrow subband, is taken as k f ϭ␣ k , where ␣ is a parameter smaller than 1.…”

Section: ͑4͒mentioning

confidence: 99%

Impurity effect on the metal-insulator transition in Kondo insulators

Oliveira

2000

Phys. Rev. B

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In this paper we study the effect of transition impurities on the metal-insulator transition in Kondo insulators. We use a two-subband model Hamiltonian in which a strongly correlated electron narrow subband is coupled to a wide conduction-electron subband. In the model, the disorder is treated by using the off-diagonal coherent potential approximation with a simple parametrization of the electron energy hopping. We obtain a criterion for the opening of the hybridization energy gap as a function of impurity concentration. In the particular case of CeRh 1Ϫx Pd x Sb, the insulator-metal transition occurs at critical Pd concentration of 10%, in agreement with experimental data. I. INTRODUCTIONKondo insulators, extensively studied in the literature, present a wide range of interesting physical properties. 1-23 In these materials, the variation of external pressure, external magnetic field, temperature, and doping can destroy the energy gap and produce an insulator-metal transition. [15][16][17][18][19][20][21] The origin of the energy gap, which is usually associated with the mixing of conduction electrons with local spins, and many aspects of the metal-insulator transition in Kondo insulators were covered in several theoretical works based on the Anderson lattice Hamiltonian, the Kondo lattice Hamiltonian, and the picture of the two-subband model. 7,14,22 Despite the great achievements of those models, many other interesting characteristics of Kondo insulators still remain open for discussion. For instance, the existence of a gapless phase in anisotropic Kondo insulators and the effects of impurities on its physical properties are not yet fully understood. Recent theoretical works 22,23 based on the periodic Anderson model discussed the effects of impurities such as La, entering substitutionally in the Ce site of Ce-based Kondo insulators. In those works it was argued that there is a formation of an impurity band in the hybridization gap when the metal-insulator transition develops. In the case of Kondo insulators doped with a transition element, such as CeRh 1Ϫx Pd x Sb, CeNi 1Ϫx Pd x Sn, and CeNi 1Ϫx Cu x Sn, the complexity of the electronic structure makes a theoretical description of the problem a difficult task, and sometimes it is necessary to develop alternative models to gain some insight into the physical process involved.Motivated by these discussions, in this paper we examine the effect of transition impurities on the formation of the energy gap, and its influence on the metal-insulator phase transition in Kondo insulators. To this end we use a twosubband model, in which a strongly correlated electrons narrow subband is coupled to a wide conduction-electron subband via a constant hybridization term. In our model, impurities entering into the system directly affect the wide subband and indirectly affect the narrow one through the hybridization between them. The impurities introduce both diagonal and off-diagonal disorder in the Hamiltonian. The diagonal disorder modifies the local energy of the conduction ...

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“…6 The case of Sml-xLaxS alloys is slightly different because the lattice parameter of LaS (5.85 ~) lies between that of the divalent (5.97 ~) and trivalent (5.26 ~) SmS. 15, when a pressure of 2-4 kbar is applied. 15, when a pressure of 2-4 kbar is applied.…”

Section: Introductionmentioning

confidence: 99%

A theoretical study of the valence transition in Sm1 ? x M x S alloys

Aveline

Iglesias

1979

J Low Temp Phys

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We present a theoretical model to explain the valence transitions of Sm in Sml-xMxS alloys, where M is a transition metal (e.g., Y or La). The f-level of Sm is described as a zero-width band with a finite Coulomb repulsion U, hybridized with the d band of the alloy, which is treated in the coherent potential approximation (CPA). The results show a change of the number of 4f electrons as a function of the concentration, which explains the valence transition observed in these alloys. 433

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Electron Correlation in Ferromagnetism. II. Hybridization ofsanddBands

Cited by 48 publications

References 16 publications

Ground State Ferromagnetism in a Generalized Hubbard Model With Strong Correlations

Ground State Ferromagnetism in a Generalized Hubbard Model With Strong Correlations

Impurity effect on the metal-insulator transition in Kondo insulators

A theoretical study of the valence transition in Sm1 ? x M x S alloys

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