Ferromagnetic Doniach diagram for the underscreened Kondo lattice

B. Coqblin; N. B. Perkins; J. R. Iglesias

doi:10.1016/j.physb.2007.10.040

Ferromagnetic Doniach diagram for the underscreened Kondo lattice

B. Coqblin, N. B. Perkins, J. R. Iglesias

Physics and Astronomy (Twin Cities)

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Abstract

A coexistence between the Kondo effect and the ferromagnetic order has been observed in some Uranium compounds such as UTe or UCu_0.9Sb₂, which order ferromagnetically at roughly 100 K and present a Kondo resistivity decrease above it. Recently we have developed the underscreened Kondo lattice (UKL) model, where the competition between the ferromagnetic order and the underscreened Kondo effect is studied by considering a Kondo coupling J_K of localized S_f = 1 spins with a conduction band and an inter-site f-f ferromagnetic exchange interaction J_H. Here we present a diagram for the UKL model, which appears to be significantly different from the Doniach diagram for the Kondo lattice model with localized spins S = frac(1, 2). We obtain that the ferromagnetic order exists for all values of the ratio J_K / J_H, while the Kondo-ferromagnetism coexistence takes place only for sufficiently large values of the ratio J_K / J_H. This new ferromagnetic diagram for the UKL model can, therefore, account for the strong Kondo-ferromagnetism coexistence observed in some Uranium compounds.

Original language	English (US)
Pages (from-to)	826-828
Number of pages	3
Journal	Physica B: Condensed Matter
Volume	403
Issue number	5-9
DOIs	https://doi.org/10.1016/j.physb.2007.10.040
State	Published - Apr 1 2008

Bibliographical note

Funding Information:
B.C. acknowledges the financial support from the European COST P16 and J.R.I. from Brazilian agencies CNPq, CAPES and FAPERGS.

Keywords

Kondo effect
Kondo lattice
Strongly correlated electron systems

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title = "Ferromagnetic Doniach diagram for the underscreened Kondo lattice",

abstract = "A coexistence between the Kondo effect and the ferromagnetic order has been observed in some Uranium compounds such as UTe or UCu0.9Sb2, which order ferromagnetically at roughly 100 K and present a Kondo resistivity decrease above it. Recently we have developed the underscreened Kondo lattice (UKL) model, where the competition between the ferromagnetic order and the underscreened Kondo effect is studied by considering a Kondo coupling JK of localized Sf = 1 spins with a conduction band and an inter-site f-f ferromagnetic exchange interaction JH. Here we present a diagram for the UKL model, which appears to be significantly different from the Doniach diagram for the Kondo lattice model with localized spins S = frac(1, 2). We obtain that the ferromagnetic order exists for all values of the ratio JK / JH, while the Kondo-ferromagnetism coexistence takes place only for sufficiently large values of the ratio JK / JH. This new ferromagnetic diagram for the UKL model can, therefore, account for the strong Kondo-ferromagnetism coexistence observed in some Uranium compounds.",

keywords = "Kondo effect, Kondo lattice, Strongly correlated electron systems",

author = "B. Coqblin and Perkins, {N. B.} and Iglesias, {J. R.}",

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AU - Perkins, N. B.

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N2 - A coexistence between the Kondo effect and the ferromagnetic order has been observed in some Uranium compounds such as UTe or UCu0.9Sb2, which order ferromagnetically at roughly 100 K and present a Kondo resistivity decrease above it. Recently we have developed the underscreened Kondo lattice (UKL) model, where the competition between the ferromagnetic order and the underscreened Kondo effect is studied by considering a Kondo coupling JK of localized Sf = 1 spins with a conduction band and an inter-site f-f ferromagnetic exchange interaction JH. Here we present a diagram for the UKL model, which appears to be significantly different from the Doniach diagram for the Kondo lattice model with localized spins S = frac(1, 2). We obtain that the ferromagnetic order exists for all values of the ratio JK / JH, while the Kondo-ferromagnetism coexistence takes place only for sufficiently large values of the ratio JK / JH. This new ferromagnetic diagram for the UKL model can, therefore, account for the strong Kondo-ferromagnetism coexistence observed in some Uranium compounds.

AB - A coexistence between the Kondo effect and the ferromagnetic order has been observed in some Uranium compounds such as UTe or UCu0.9Sb2, which order ferromagnetically at roughly 100 K and present a Kondo resistivity decrease above it. Recently we have developed the underscreened Kondo lattice (UKL) model, where the competition between the ferromagnetic order and the underscreened Kondo effect is studied by considering a Kondo coupling JK of localized Sf = 1 spins with a conduction band and an inter-site f-f ferromagnetic exchange interaction JH. Here we present a diagram for the UKL model, which appears to be significantly different from the Doniach diagram for the Kondo lattice model with localized spins S = frac(1, 2). We obtain that the ferromagnetic order exists for all values of the ratio JK / JH, while the Kondo-ferromagnetism coexistence takes place only for sufficiently large values of the ratio JK / JH. This new ferromagnetic diagram for the UKL model can, therefore, account for the strong Kondo-ferromagnetism coexistence observed in some Uranium compounds.

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KW - Strongly correlated electron systems

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Ferromagnetic Doniach diagram for the underscreened Kondo lattice

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Keywords

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