Magnetic properties of SmB6 and Sm1−xLaxB6 solid solutions

Gabáni, S.; Flachbart, К.; Pavlı́k, V.; Herrmannsdörfer, T.; Konovalova, E.S.; Paderno, Yu. B.; Briančin, Jaroslav; Trpčevská, Jarmila

doi:10.1007/s10582-002-0054-8

Cited by 20 publications

(20 citation statements)

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“…2) shows that the IV state of Sm ions is maintained in Sm 1−x B 6 samples up to 20 % of concentration x of vacancies and the valence increases with increasing x. These results are in good qualitative agreement with susceptibility and Xray measurements [4,7] and exact numerical calculation of the spinless FKM in two dimensions [10]. This theoretical study of Sm 1−x B 6 has shown that the valence transition of Sm ions is maintained up to 25% of vacancy concentration x and that the average f -orbital occupancy, n f = 3 − v, decreases with x.…”

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confidence: 74%

Investigation of Mixed Valence State of Sm_{1-x}B_{6} and Sm_{1-x}La_{x}B_{6} by XANES

et al. 2014

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We investigated the valence states of samarium ions in Sm decient Sm1−xB6 (x = 0.03, 0.05, 0.08, 0.1 and 0.2) sintered samples, in single crystalline solid solutions Sm1−xLaxB6 (x = 0.16, 0.28, 0.4, 0.55 and 0.7) as well as in a SmB6 single crystal by X-ray absorption near edge structure (XANES) between 4.2 and 300 K. It was shown that the mixed valence state vSm of Sm-ions (vSm ≈ 2.51 for SmB6 at 4.2 K) in decient samples is changed but maintained up to a concentration of 20% of vacancies and up to a concentration of 70% in samples doped with trivalent La-ions, and that in both cases it increases with temperature. On the other hand, the value of vSm increases with increasing vacancy level, whereas it decreases with increasing La 3+ substitution. The obtained dependences of Sm-valence in SmB6 on vacancy as well as on La 3+ ion concentration are in good agreement with susceptibility measurements and exact numerical calculation of the spinless Falicov-Kimball model in two dimensions.

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Section: Resultssupporting

confidence: 74%

Investigation of Mixed Valence State of Sm_{1-x}B_{6} and Sm_{1-x}La_{x}B_{6} by XANES

et al. 2014

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“…Experimentally, we investigated the near-gap region of SmB 6 by photoemission spectroscopy (PES). There are fascinating low- T properties observed in SmB 6 44 – 57 , which we do not consider in the present study. Note that, as the energy resolution of the PES setup is limited, PES results have not detected all degenerate f bands predicted in first-principle calculations 7 , 8 , 17 , 27 in the energy range of 20 meV below the chemical potential 22 , 58 – 63 .…”

Section: Introductionmentioning

confidence: 77%

Matching DMFT calculations with photoemission spectra of heavy fermion insulators: universal properties of the near-gap spectra of SmB6

Min

Goth

Lutz

et al. 2017

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Paramagnetic heavy fermion insulators consist of fully occupied quasiparticle bands inherent to Fermi liquid theory. The gap emergence below a characteristic temperature is the ultimate sign of coherence for a many-body system, which in addition can induce a non-trivial band topology. Here, we demonstrate a simple and efficient method to compare a model study and an experimental result for heavy fermion insulators. The temperature dependence of the gap formation in both local moment and mixed valence regimes is captured within the dynamical mean field (DMFT) approximation to the periodic Anderson model (PAM). Using the topological coherence temperature as the scaling factor and choosing the input parameter set within the mixed valence regime, we can unambiguously link the theoretical energy scales to the experimental ones. As a particularly important result, we find improved consistency between the scaled DMFT density of states and the photoemission near-gap spectra of samarium hexaboride (SmB6).

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“…Below T ∼ 15 K there is a Curie-like upturn in χ mol (T ), which is generally attributed to paramagnetic impurities. 29,30 In the Fe-doped sample the low-T upturn in χ mol is enhanced and begins at a slightly higher temperature. Figure 2(a) shows the temperature dependence of the electrical sheet resistance.…”

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Quantum spin fluctuations in the bulk insulating state of pure and Fe-doped SmB6

et al. 2017

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The intermediate-valence compound SmB6 is a well-known Kondo insulator, in which hybridization of itinerant 5d electrons with localized 4f electrons leads to a transition from metallic to insulating behavior at low temperatures. Recent studies suggest that SmB6 is a topological insulator, with topological metallic surface states emerging from a fully insulating hybridized bulk band structure. Here we locally probe the bulk magnetic properties of pure and 0.5 % Fe-doped SmB6 by muon spin rotation/relaxation (µSR) methods. Below 6 K the Fe impurity induces simultaneous changes in the bulk local magnetism and the electrical conductivity. In the low-T insulating bulk state we observe a temperature-independent dynamic relaxation rate indicative of low-lying magnetic excitations driven primarily by quantum fluctuations.Topological insulators are exotic quantum states of matter characterized by an electrically insulating bulk and topologically-protected metallic surface states. Due to an interplay of strong correlations and strong spinorbit coupling of the 4f electrons, SmB 6 is predicted to develop a non-trivial Z 2 topological insulating state. 1 Angle-resolved photoemission 2 and point-contact spectroscopy 3 measurements show that the crossover from the bulk high-T metallic state to the low-T Kondo insulating phase occurs gradually over a fairly wide temperature range (30 K < T < 110 K). Transport measurements show that surface electrical conduction occurs below T ∼ 5 to 6 K with a resistance that saturates at lower temperature. 4-6 The low-T conduction arises from twodimensional states 7 that occur in the hybridization gap exclusively at the surface, 3,4,8 as expected for metallic surface states of topological origin. 9 Yet the ground state of SmB 6 is still unclear, in part because not all bulk properties at low T are that of a conventional band-gapped insulator. Despite the loss of bulk electrical conduction, quantum oscillations consistent with a bulk Fermi surface have been observed, 10 and the low-temperature specific heat exhibits a significant bulk residual T -linear term typical of a metallic state. 11 Recently, it has been argued that there is some residual bulk electrical conductivity in SmB 6 below 4 K. 12 There also exists significant bulk acconduction arising from low-energy states in the Kondo gap. 13Nuclear magnetic resonance (NMR) Knight shift and spin-lattice relaxation rate (1/T 1 ) measurements, 14 bulk magnetic susceptibility, 15 Raman spectroscopy, 16,17 and inelastic neutron scattering (INS) 18,19 studies of SmB 6 reveal the emergence of bulk in-gap bound states of a different origin below T ∼ 20-30 K. The sharp dispersive magnetic excitations observed at 14 meV within the hybridization gap by INS have been attributed to a bulk collective spin exciton resonance mode due to residual antiferromagnetic (AFM) quasiparticle interactions. 20,21 These bound magnetic quasiparticle states are robust due to the protection provided by the hybridization gap, and there is evidence that the spin excitons co...

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Magnetic properties of SmB6 and Sm1−xLaxB6 solid solutions

Cited by 20 publications

References 5 publications

Investigation of Mixed Valence State of Sm_{1-x}B_{6} and Sm_{1-x}La_{x}B_{6} by XANES

Investigation of Mixed Valence State of Sm_{1-x}B_{6} and Sm_{1-x}La_{x}B_{6} by XANES

Matching DMFT calculations with photoemission spectra of heavy fermion insulators: universal properties of the near-gap spectra of SmB6

Quantum spin fluctuations in the bulk insulating state of pure and Fe-doped SmB6

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