Effective magnetic Hamiltonians from ﬁrst principles

Drchal, V.; Kudrnovský, J.; Turek, I.

doi:10.1051/epjconf/20134011001

Cited by 12 publications

(8 citation statements)

References 10 publications

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“…As a consequence, subsequent Monte Carlo simulations based on this Hamiltonian account in particular for longitudinal fluctuations of the spin moments. A similar approach has been used by Drchal et al [58,59], leading to good agreement with the results of Ruban et al However, the scheme used in these calculations does not supply in a straightforward manner the necessary input for temperature-dependent transport calculations. This is different from the work of Staunton et al [60], who performed self-consistent relativistic DLM calculations without the restriction to a collinear spin configuration.…”

Section: Csupporting

confidence: 54%

Calculating linear-response functions for finite temperatures on the basis of the alloy analogy model

et al. 2015

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A scheme is presented that is based on the alloy analogy model and allows one to account for thermal lattice vibrations as well as spin fluctuations when calculating response quantities in solids. Various models to deal with spin fluctuations are discussed concerning their impact on the resulting temperature-dependent magnetic moment, longitudinal conductivity, and Gilbert damping parameter. It is demonstrated that, by using the Monte Carlo (MC) spin configuration as input, the alloy analogy model is capable of reproducing the results of MC simulations on the average magnetic moment within all spin fluctuation models under discussion. On the other hand, the response quantities are much more sensitive to the spin fluctuation model. Separate calculations accounting for the thermal effect due to either lattice vibrations or spin fluctuations show that they give comparable contributions to the electrical conductivity and Gilbert damping. However, comparison to results accounting for both thermal effects demonstrates violation of Matthiessen's rule, showing the nonadditive effect of lattice vibrations and spin fluctuations. The results obtained for bcc Fe and fcc Ni are compared with the experimental data, showing rather good agreement for the temperature-dependent electrical conductivity and the Gilbert damping parameter.

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Section: Csupporting

confidence: 54%

Calculating linear-response functions for finite temperatures on the basis of the alloy analogy model

et al. 2015

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“…One can understand this result as a stabilizing effect of the magnetic entropy. A similar effect exists also at ambient conditions, e.g., for fcc Ni in paramagnetic region 14 . In particular, the issue here was an estimate of the size of fluctuating local Nimoment just above T c , i.e., in the paramagnetic state.…”

Section: Introductionmentioning

confidence: 54%

Transport properties of iron at Earth's core conditions: The effect of spin disorder

et al. 2017

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The electronic and thermal transport properties of the Earth's core are crucial for many geophysical models such as the geodynamo model of the Earth's magnetic field and of its reversals. Here we show, by considering bcc-iron and iron-rich iron-silicon alloy as a representative of the Earth's core composition and applying the first-principles modeling that the spin disorder at the Earth's core conditions not considered previously provides an essential contribution, of order 20 µΩ cm, to the electrical resistivity. This value is comparable in magnitude with the electron-phonon and with the recently estimated electron-electron scattering contributions. The origin of the spin-disorder resistivity (SDR) consists in the existence of fluctuating local moments that are stabilized at high temperatures by the magnetic entropy even at pressures at which the ground state of iron is non-magnetic. We find that electron-phonon and SDR contributions are not additive at high temperatures. We thus observe a large violation of the Matthiessen rule, not common in conventional metallic alloys at ambient conditions. PACS numbers: 72.25. Ba,75.20.Hr,91.35.Cb,91.35.Lj

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“…This theoretical approach gives reliable results for three-dimensional materials with large coordination number, and is able to access the magnetic as well as the non-ordered phase above T C . The latter is described by DFT+DMFT as non-vanishing local magnetic moments with strong quantum fluctuations, which is crucial for the physics of correlated itinerant magnets 20 21 22 23 . Our DFT+DMFT spectra are consistent with previous calculations of similar kind 10 24 25 26 and agree reasonably well with angular-resolved photoemission data (see Supplementary Note 5 and Supplementary Figs 2–5 ).…”

Section: Resultsmentioning

confidence: 99%

Local magnetic moments in iron and nickel at ambient and Earth’s core conditions

et al. 2017

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Some Bravais lattices have a particular geometry that can slow down the motion of Bloch electrons by pre-localization due to the band-structure properties. Another known source of electronic localization in solids is the Coulomb repulsion in partially filled d or f orbitals, which leads to the formation of local magnetic moments. The combination of these two effects is usually considered of little relevance to strongly correlated materials. Here we show that it represents, instead, the underlying physical mechanism in two of the most important ferromagnets: nickel and iron. In nickel, the van Hove singularity has an unexpected impact on the magnetism. As a result, the electron–electron scattering rate is linear in temperature, in violation of the conventional Landau theory of metals. This is true even at Earth’s core pressures, at which iron is instead a good Fermi liquid. The importance of nickel in models of geomagnetism may have therefore to be reconsidered.

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Effective magnetic Hamiltonians from ﬁrst principles

Cited by 12 publications

References 10 publications

Calculating linear-response functions for finite temperatures on the basis of the alloy analogy model

Calculating linear-response functions for finite temperatures on the basis of the alloy analogy model

Transport properties of iron at Earth's core conditions: The effect of spin disorder

Local magnetic moments in iron and nickel at ambient and Earth’s core conditions

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