Thermal destruction of spin-polaron bands in the narrow-gap correlated semiconductors FeGa<sub>3</sub>and FeSb<sub>2</sub>

Storchak, Vyacheslav G.; Brewer, J. H.; Lichti, R. L.; Hu, Rongwei; Petrović, C.

doi:10.1088/0953-8984/24/18/185601

Cited by 17 publications

(27 citation statements)

References 42 publications

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“…These states frequently are assigned being responsible for the giant thermopower in Fe based semimetals at low temperatures. 7,11,18,19 Only above ∼70 K, when the in-gap level is completely empty, the nuclear spin-lattice relaxation exhibits a crossover to a phonon mechanism characteristic of quadrupolar nuclei in nonmagnetic systems. The other end member, CoGa 3 , is a band metal.…”

Section: Discussionmentioning

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: Discussionmentioning

confidence: 99%

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

et al. 2014

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“…The doublet in figures 1 and 2 may originate from a coupled m +e spin system in high transverse magnetic field [19,20,22,[26][27][28][29][30][31]: the two lines correspond to two muon spin-flip transitions between states with the electron spin orientation fixed, the splitting between them being determined by the muon-electron hyperfine interaction A [26,27]. The temperature behaviour of lines with one line going up in frequency and the other going down as temperature decreases is often a signature of a muon-electron bound state [20,22].…”

Section: Muon Spin Rotation Studiesmentioning

confidence: 99%

“…Such SP states have been previously invoked to explain μ + SR spectra in strongly correlated insulators [28,38], semiconductors [26,27,31] and metals [29,30]. The latter reference initiated a debate on SP formation in MnSi [39,40].…”

Section: Muon Spin Rotation Studiesmentioning

confidence: 99%

Spin gap in heavy fermion compound UBe₁₃

et al. 2016

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Heavy fermion (HF) compounds are well known for their unique properties, such as narrow bandwidths, loss of coherence in a metal, non-Fermi-liquid behaviour, unconventional superconductivity, huge magnetoresistance etc. While these materials have been known since the 1970s, there is still considerable uncertainty regarding the fundamental mechanisms responsible for some of these features. Here we report transverse-field muon spin rotation (μ + SR) experiments on the canonical HF compound UBe 13 in the temperature range from 0.025 to 300 K and in magnetic fields up to 7 T. The μ + SR spectra exhibit a sharp anomaly at 180 K. We present a simple explanation of the experimental findings identifying this anomaly with a gap in the spin excitation spectrum of f-electrons opening near 180 K. It is consistent with anomalies discovered in heat capacity, NMR and optical conductivity measurements of UBe 13 , as well as with the new resistivity data presented here. The proposed physical picture may explain several long-standing mysteries of UBe 13 (as well as other HF systems).

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“…So far, there is no consensus in either experimental or theoretical studies as to the overall magnetic character of FeGa 3 [31,33,36,[43][44][45]. LSDA+U electronic-structure calculations find the existence of local Fe moments in FeGa 3 , independent of which double-counting scheme is used, with an antiferromagnetic order being lowest in energy [33].…”

Section: Introductionmentioning

confidence: 99%

“…However, a nonmagnetic state is stabilized for U 1.5 eV and even for larger values of U if screening effects are included in the LSDA+U formalism via a Yukawa ansatz [36]. On the experimental side, a recent muon spin rotation study detected spectroscopic features characteristic of electron confinement into spin polarons [44]. Formation of spin polarons requires the existence of Fe moments, whereas a 57 Fe Mössbauer study did not show the presence of an internal magnetic field at the Fe site, indicating a nonmagnetic state of Fe [45].…”

Section: Introductionmentioning

confidence: 99%

Electronic correlations inFeGa3and the effect of hole doping on its magnetic properties

et al. 2014

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We investigate signatures of electronic correlations in the narrow-gap semiconductor FeGa 3 by means of electrical resistivity and thermodynamic measurements performed on single crystals of FeGa 3 , Fe 1−x Mn x Ga 3 , and FeGa 3−y Zn y , complemented by a study of the 4d analog material RuGa 3 . We find that the inclusion of sizable amounts of Mn and Zn dopants into FeGa 3 does not induce an insulator-to-metal transition. Our study indicates that both substitution of Zn onto the Ga site and replacement of Fe by Mn introduces states into the semiconducting gap that remain localized even at highest doping levels. Most importantly, using neutron powder diffraction measurements, we establish that FeGa 3 orders magnetically above room temperature in a complex structure, which is almost unaffected by the doping with Mn and Zn. Using realistic many-body calculations within the framework of dynamical mean field theory (DMFT), we argue that while the iron atoms in FeGa 3 are dominantly in an S = 1 state, there are strong charge and spin fluctuations on short-time scales, which are independent of temperature. Further, the low magnitude of local contributions to the spin susceptibility advocates an itinerant mechanism for the spin response in FeGa 3 . Our joint experimental and theoretical investigations classify FeGa 3 as a correlated band insulator with only small dynamical correlation effects, in which nonlocal exchange interactions are responsible for the spin gap of 0.4 eV and the antiferromagnetic order. We show that hole doping of FeGa 3 leads, within DMFT, to a notable strengthening of many-body renormalizations.

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Thermal destruction of spin-polaron bands in the narrow-gap correlated semiconductors FeGa₃and FeSb₂

Cited by 17 publications

References 42 publications

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Spin gap in heavy fermion compound UBe₁₃

Electronic correlations inFeGa3and the effect of hole doping on its magnetic properties

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Thermal destruction of spin-polaron bands in the narrow-gap correlated semiconductors FeGa3and FeSb2

Cited by 17 publications

References 42 publications

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Spin gap in heavy fermion compound UBe13

Electronic correlations inFeGa3and the effect of hole doping on its magnetic properties

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Product

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Thermal destruction of spin-polaron bands in the narrow-gap correlated semiconductors FeGa₃and FeSb₂

Spin gap in heavy fermion compound UBe₁₃