Spin fluctuations and ferromagnetic order in two-dimensional itinerant systems with Van Hove singularities

Igoshev, P. A.; Катанин, А. А.; Yamase, Hiroyuki; Irkhin, V. Yu.

doi:10.1016/j.jmmm.2008.11.048

Cited by 13 publications

(8 citation statements)

References 23 publications

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“…3 is much narrower, than that expected in the mean-field approaches, 16,17 which predict incommensurate instability in the most part of the phase diagram. In fact, accurate meanfield investigations 16,18,19 show, that substantial part of incommensurate state in the mean-field approach is unstable toward phase separation into commensurate and incommen- surate regions. The presence of incommensurate phases within the renormalization-group approach was noticed previously for tЈ = 0 in Ref.…”

Section: Resultsmentioning

confidence: 99%

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Quantum critical behavior of antiferromagnetic itinerant systems with van Hove singularities

Катанин

2010

Phys. Rev. B

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The interplay of magnetic and superconducting fluctuations in two-dimensional systems with van Hove singularities in the electronic spectrum is considered within the functional renormalization-group ͑fRG͒ approach. While the fRG flow has to be stopped at a certain minimal temperature T RG min , we study temperature dependence of magnetic and superconducting susceptibilities below T RG min to obtain the crossover temperatures to the regime with strong magnetic and superconducting fluctuations. Near half filling we obtain the largest crossover temperature, corresponding to a regime with strong commensurate magnetic fluctuations, which is replaced by a regime with strong incommensurate fluctuations further away from half filling. With further decreasing density the system undergoes quantum phase transition from incommensurate to paramagnetic phase. Similarly to results of Hertz-Moriya-Millis approach, the temperature dependence of the inverse ͑in-commensurate͒ magnetic susceptibility at the magnetic quantum-critical point is found almost linear in temperature.

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Section: Resultsmentioning

confidence: 99%

“…Application of the method considered in the present paper to ferromagnetic instability and detail comparison of the results of the present approach with the mean-field approach and quasistatic approach of Ref. 18 also has to be performed.…”

Section: Discussionmentioning

confidence: 99%

Quantum critical behavior of antiferromagnetic itinerant systems with van Hove singularities

Катанин

2010

Phys. Rev. B

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“…The determination of the domain of parameters for which this assumption holds is discussed in Appendix 2 (see also [15]). For all the results presented below, this assumption was satisfied.…”

Section: Isothermal Entropy Change Of a Metallic System In Low Fieldsmentioning

confidence: 99%

“…(12) and (13), we used designations and Expanding the right-hand side of Eq. (8) into a series in powers of Δ and up to the lowest order, we obtain (14) where (15) …”

Section: Isothermal Entropy Change Of a Metallic System In Low Fieldsmentioning

confidence: 99%

Investigation of the magnetocaloric effect in correlated metallic systems with Van Hove singularities in the electron spectrum

Igoshev

Kokorina

Некрасов

2017

Phys. Metals Metallogr.

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Abstract⎯In this work, the magnetic contribution to the isothermal entropy change upon switching on a magnetic field has been investigated in correlated metallic ferromagnets within the Hubbard nondegenerate model. The analytical expression for obtained in the mean-field approximation depends substantially on the electronic structure (density of electron states), which presents new ways to increase the absolute value of relative to the known result obtained within the Heisenberg model. The temperature dependence of has been calculated at different values of the Coulomb interaction U and the number of electrons n for the Bethe infinite-dimensional lattice and square lattice with allowance for transfer integrals in the first (t) and the second (t') coordination shells. It has been found that the presence of Van Hove singularities in the electronic spectrum near the Fermi level makes it possible to considerably increase at a fixed magnetic field. The possibility of first-order magnetic phase transitions depending on the model parameters has been analyzed.

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“…The importance of incommensurate magnetic fluctuations at weak and moderate Coulomb interaction was recently emphasized within the quasistatic approach, 9,10) mean-field theory, 11) and a renormalization-group approach. 12) These approaches showed that in a large part of the phase diagram spanned by the electron density n and Coulomb interaction U the ferromagnetic order is replaced by an incommensurate one.…”

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confidence: 99%

Ferromagnetic Instability and Finite-Temperature Properties of Two-Dimensional Electron Systems with van Hove Singularities

2011

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We study a ferromagnetic tendency in the two-dimensional Hubbard model near van Hove filling by using a functional renormalization-group method. We compute temperature dependences of magnetic susceptibilities including incommensurate magnetism. The ferromagnetic tendency is found to occur in a dome-shaped region around van Hove filling with an asymmetric property: incommensurate magnetism is favored near the edge of the dome above van Hove filling whereas a first-order-like transition to the ferromagnetic ground state is ex- The stability of itinerant-electron ferromagnetism is an important problem of correlated d-electron systems. 1, 2) Stoner proposed a simple approach to treat the ferromagnetic instability, introducing an averaged magnetic field of electrons at each lattice site. His theory is, however, insufficient to describe adequately even magnets with small magnetic moments, especially at finite temperatures. The transition temperatures appear too high in comparison with experimental data and the temperature dependence of the magnetic susceptibility is not described correctly. Dzyaloshinskii, Kondratenko 3) and Moriya 4) proposed the spin-fluctuation theory considering a contribution of paramagnons to thermodynamic properties. They improved the Stoner theory, especially for finite temperature properties of weak and nearly ferromagnetic systems.The condition for ferromagnetic order in the ground state is also corrected by their theory.In the regime of strong Coulomb repulsion the stability of ferromagnetism was considered in the pioneering studies by Nagaoka 5) and Roth, 6) which showed the existence of a saturated ferromagnetic region close to half filling and non-saturated ferromagnetism further away from it. The region of the saturated ferromagnetism was investigated in more details within various

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Spin fluctuations and ferromagnetic order in two-dimensional itinerant systems with Van Hove singularities

Cited by 13 publications

References 23 publications

Quantum critical behavior of antiferromagnetic itinerant systems with van Hove singularities

Quantum critical behavior of antiferromagnetic itinerant systems with van Hove singularities

Investigation of the magnetocaloric effect in correlated metallic systems with Van Hove singularities in the electron spectrum

Ferromagnetic Instability and Finite-Temperature Properties of Two-Dimensional Electron Systems with van Hove Singularities

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