Correlation effects in the small gap semiconductor FeGa<sub>3</sub>

Bittar, E. M.; Capan, C.; Seyfarth, Gabriel; Pagliuso, P. G.; Fisk, Z.

doi:10.1088/1742-6596/200/1/012014

Cited by 29 publications

(46 citation statements)

References 14 publications

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“…It has been reported 14 that already a few percent cobalt doping in FeGa 3 drastically changes the properties of the parent compound. Namely, the 5% Co-doped Fe 0.95 Co 0.05 Ca 3 exhibits properties of a bad metal and a Curie-Weiss paramagnet, in contrast to semiconducting and nonmagnetic FeGa 3 .…”

Section: 13mentioning

confidence: 99%

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

et al. 2014

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The evolution of the electronic structure and magnetic properties with Co substitution for Fe in the solid solution Fe1−xCoxGa3 was studied by means of electrical resistivity, magnetization, ab initio band structure calculations, and nuclear spin-lattice relaxation 1/T1 of the 69,71 Ga nuclei. Temperature dependencies of the electrical resistivity reveal that the evolution from the semiconducting to the metallic state in the Fe1−xCoxGa3 system occurs at 0.025 < x < 0.075. The 69,71 (1/T1) was studied as a function of temperature in a wide temperature range of 2−300 K for the concentrations x = 0.0, 0.5, and 1.0. In the parent semiconducting compound FeGa3, the temperature dependence of the 69 (1/T1) exhibits a huge maximum at about T ∼ 6 K indicating the existence of in-gap states. The opposite binary compound, CoGa3, demonstrates a metallic Korringa behavior with 1/T1 ∝ T . In Fe0.5Co0.5Ga3, the relaxation is strongly enhanced due to spin fluctuations and follows 1/T1 ∝ T 1/2 , which is a unique feature of weakly and nearly antiferromagnetic metals. This itinerant antiferromagnetic behavior contrasts with both magnetization measurements, showing localized magnetism with a relatively low effective moment of about 0.7 µB/f.u., and ab initio band structure calculations, where a ferromagnetic state with an ordered moment of 0.5 µB/f.u. is predicted. The results are discussed in terms of the interplay between the localized and itinerant magnetism including in-gap states and spin fluctuations.

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Section: 13mentioning

confidence: 99%

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

et al. 2014

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“…FeGa 3 is a semiconductor with tetragonal structure (space group P 4 2 /mnm) 2 and a narrow band gap of approximately 0.5 eV caused by the hybridization of the 3d Fe and 4p Ga bands [2][3][4]16,24,25 . It is diamagnetic over a broad temperature range and has a small Sommerfeld coefficient (γ =0.03 mJ mol K ) 3,11,16 .…”

Section: Introductionmentioning

confidence: 99%

“…A unit cell contains 4 formula units where each Fe has eight Ga neighbors at two distinct sites Ga1 (0.236 nm, 2 atoms) and Ga2 (0.239 nm, 2 atoms and 0.246 nm, 4 atoms, above the plane containing Fe) 2 . Whereas hole doping by Zn at the Ga site or Mn at the Fe site 14 does not induce an insulating-metal transition and introduces ingap states 16 , electron doping either at the Fe or the Ga site destroys the semiconducting behavior, and remarkably influences other physical properties [11][12][13][14][15][16][17][18][19][20][21][24][25][26] .…”

Section: Introductionmentioning

confidence: 99%

Magnetic order of intermetallicFeGa3−yGeystudied byμSRand<

et al. 2017

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Temperature dependent magnetization, muon spin rotation and 57 Fe Mössbauer spectroscopy experiments performed on crystals of intermetallic 0.14, 0.17, 0.22, 0.27, 0.29, 0.32) are reported. Whereas at y = 0.11 even a sensitive magnetic microprobe such as µSR does not detect magnetism, all other samples display weak ferromagnetism with a magnetic moment of up to 0.22 µB per Fe atom. As a function of doping and of temperature a crossover from short range to long range magnetic order is observed, characterized by a broadly distributed spontaneous internal field. However, the y = 0.14 and y = 0.17 remain in the short range ordered state down to the lowest investigated temperature. The transition from short range to long range order appears to be accompanied by a change of the character of the spin fluctuations, which exhibit spin wave excitations signature in the LRO part of the phase diagram. Mössbauer spectroscopy for y = 0.27 and 0.32 indicates that the internal field lies in the plane perpendicular to the crystallographic c axis. The field distribution and its evolution with doping suggest that the details of the Fe magnetic moment formation and the consequent magnetic state are determined not only by the dopant concentration but also by the way the replacement of the Ga atoms surrounding the Fe is accomplished.

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“…Finally, we make explicit suggestions for improving the thermoelectric performance of FeSi based systems. strongly correlated electrons | Kondo insulator | metal-insulator transitions | electronic structure | material science I ron-based narrow gap semiconductors such as FeSi, FeSb 2 , or FeGa 3 show a pronounced resemblance to heavy fermion Kondo insulators in their charge (1)(2)(3)(4) and spin (4, 5) degrees of freedom. Besides, these systems display a large thermopower (1,3,(6)(7)(8)(9), heralding their potential use in solid-state devices.…”

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confidence: 99%

“…There are two complementary approaches for explaining these unusual properties: On one hand, it has been proposed that lattice degrees of freedom play a crucial role (7,10,11). On the other hand, electron-electron correlation effects have been invoked on the basis of both experimental results (2)(3)(4)8), as well as theoretical model studies (12)(13)(14)(15), advocating, in particular, Hubbard physics (12,14,15), spin fluctuations (13), spin-state transitions (16,17), or a thermally induced mixed valence (18).…”

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confidence: 99%

Signatures of electronic correlations in iron silicide

Tomczak

Haule

Kotliar

2012

Proc. Natl. Acad. Sci. U.S.A.

101

113

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The intermetallic FeSi exhibits an unusual temperature dependence in its electronic and magnetic degrees of freedom, epitomized by the cross-over from a low-temperature nonmagnetic semiconductor to a high-temperature paramagnetic metal with a Curie-Weisslike susceptibility. Many proposals for this unconventional behavior have been advanced, yet a consensus remains elusive. Using realistic many-body calculations, we here reproduce the signatures of the metal-insulator cross-over in various observables: the spectral function, the optical conductivity, the spin susceptibility, and the Seebeck coefficient. Validated by quantitative agreement with experiment, we then address the underlying microscopic picture. We propose a new scenario in which FeSi is a band insulator at low temperatures and is metalized with increasing temperature through correlation induced incoherence. We explain that the emergent incoherence is linked to the unlocking of iron fluctuating moments, which are almost temperature independent at short timescales. Finally, we make explicit suggestions for improving the thermoelectric performance of FeSi based systems. strongly correlated electrons | Kondo insulator | metal-insulator transitions | electronic structure | material science I ron-based narrow gap semiconductors such as FeSi, FeSb 2 , or FeGa 3 show a pronounced resemblance to heavy fermion Kondo insulators in their charge (1-4) and spin (4, 5) degrees of freedom. Besides, these systems display a large thermopower (1,3,(6)(7)(8)(9), heralding their potential use in solid-state devices. There are two complementary approaches for explaining these unusual properties: On one hand, it has been proposed that lattice degrees of freedom play a crucial role (7,10,11). On the other hand, electron-electron correlation effects have been invoked on the basis of both experimental results (2-4, 8), as well as theoretical model studies (12-15), advocating, in particular, Hubbard physics (12,14,15), spin fluctuations (13), spin-state transitions (16, 17), or a thermally induced mixed valence (18).Here, we go beyond modelistic approaches and investigate the effect of correlations on prototypical FeSi from the ab initio perspective. The key issues that we address are (i) can electronic Coulomb correlations alone quantitatively account for the signatures of the temperature induced cross-over in various observables, and (ii) what is the underlying microscopic origin of this behavior? As a realistic many-body approach, we employ the combination of density functional theory (DFT) and dynamical mean-field theory (DMFT), DFT þ DMFT (for a review see, e.g., ref. 19) as implemented in ref. 20. For the calculation of the Seebeck coefficient, we have extended our previous work (9) for DFT computations to include the DMFT self-energy in a full orbital setup. For details, see SI Text.At low temperatures, iron silicide is a semiconductor with a gap Δ ≈ 50-60 meV (2, 5, 21), with the resistivity (1, 6) and the magnetic susceptibility (5) following activation laws. At 150-20...

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Correlation effects in the small gap semiconductor FeGa₃

Cited by 29 publications

References 14 publications

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Magnetic order of intermetallicFeGa3−yGeystudied byμSRand<

Signatures of electronic correlations in iron silicide

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Correlation effects in the small gap semiconductor FeGa3

Cited by 29 publications

References 14 publications

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Magnetic order of intermetallicFeGa3−yGeystudied byμSRand<

Signatures of electronic correlations in iron silicide

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Correlation effects in the small gap semiconductor FeGa₃