Raman scattering in ZrB12 cage glass

Sluchanko, N. E.; Azarevich, A. N.; Anisimov, M. A.; Bogach, A. V.; Gavrilkin, S. Yu.; Ġlushkov, V. V.; Demishev, S. V.; Максимов, А. А.; Tartakovskii, I. I.; Filatov, E. V.; Филиппов, В. Б.; Lyashchenko, A. B.

doi:10.1134/s0021364016110126

Cited by 6 publications

(3 citation statements)

References 20 publications

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“…In the connection of the present study, it is necessary to mention the rich borides, where the possibility of the glass behavior caused by the displacement of RE ions from their position in the lattice is discussed in literature. The signs of SG behavior were found in PrB 6 62 , 63 and the presence of the “cage-glass” state was claimed taking place in dodecaborides LuB 12 and ZrB 12 64 , 65 . However, as for magnetic and nonmagnetic RE ions the origin of the assumed glass effects is inherent defects in the boron lattice which induce the ions shift.…”

Section: Resultsmentioning

confidence: 93%

Role of spin-glass behavior in the formation of exotic magnetic states in GdB6

Semeno

Anisimov

Bogach

et al. 2020

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Randomness and frustration are believed to be two crucial criteria for the formation of spin glass state. However, the spin freezing occurs in some well-ordered crystals below the related temperature Tf due to the instability of each spin state, which induces the variation of either magnetic moment value or exchange energy. Here we explore the new mechanism of the in-site originated disorder in antiferromagnets Gd0.73La0.27B6 and GdB6, which is caused by the random mutual shifts of Gd3+ spins from the centrally symmetrical positions in the regular cubic lattice. The universal scaling of ESR linewidth temperature dependencies to the power law ΔH(T) ~ ((T − TD)/TD)α with α = − 1.1 ± 0.05 in the paramagnetic phase of both compounds demonstrates the identity of the origin of magnetic randomness. In Gd0.73La0.27B6 the resulting random spin configurations freeze at Tf ≈ 10.5 K where the maximum of magnetization is observed. Below Tf the splitting of ZFC and FC magnetization curves takes place as well as the magnetic state depends on the antecedent sample history. In the case of GdB6 the coherent displacement of Gd ions compete with these random shifts forming an antiferromagnetic (AFM) phase at TN = 15.5 K, which prevails over the spin freezing at Tf ≈ 13 K, expected from the ESR data. The observation of the hysteresis of the ESR spectrum in the AFM phase suggests that its properties may be determined by the competition of two types of AFM orders, which results in formation of stable magnetic domains with nonequivalent positions of AFM Gd pairs at T < 10 K.

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Section: Resultsmentioning

confidence: 93%

Role of spin-glass behavior in the formation of exotic magnetic states in GdB6

Semeno

Anisimov

Bogach

et al. 2020

Sci Rep

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“…1). In Raman spectra of Lu N B 12 [47] and Zr N B 12 [79] with a different isotopic composition of boron (N = 10, 11, nat; nat corresponds to the natural content of boron isotopes: 18.83% 10 B and 81.17% 11 B) it was shown that the Raman response exhibits a boson peak at liquid nitrogen temperatures, and such a feature in the lowfrequency range was discussed as a fingerprint of systems with strong structural disorder. To explain the properties of LuB 12 authors of [47] have proposed a model of cage-glass formation with a phase transition at T* ~ 50 -70 K, and it was found that the barrier height of the doublewell potential E 2 (Fig.…”

Section: IVmentioning

confidence: 99%

“…meV [65]. According to [28], [36], [65], [79] a low frequency peak in the Eliashberg function was observed in ZrB 12 near  0 ~ 100 cm -1 (~12 meV) and it is located well below the Einstein mode at  E ~ 140 cm -1 (~17.5 meV) [29]. The value  e-ph ≈ 0.58 was deduced from the detailed analysis of heat capacity made in [33] where three Einstein modes ħ Е1 /k B  200 К and ħ Е2,3 /k B  450 К were found to mediate the electron-phonon interaction in ZrB 12 resulting to pre-exponent <ħ ln >/k B ≈ 368 K. Note again, that the isotropic single-band models do not discuss the difference between the estimated values  e-ph ≈ 0.58-0.68 and the much smaller constant  e-ph ~ 0.4 detected from the Sommerfeld coefficient (Fig.…”

Section: Scenarios Of Superconductivitymentioning

confidence: 99%

Inhomogeneous superconductivity in LuxZr1−xB12 dodecaborides with dynamic charge stripes

et al. 2021

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We have studied the normal and superconductive state characteristics (resistivity, Hall coefficient, heat capacity and magnetization) of model strongly correlated electronic systems Lu x Zr 1-x B 12 with cooperative Jahn-Teller instability of the boron rigid cage and with dynamic charge stripes. It was found that these metals are s-wave dirty limit superconductors with a small mean free path of charge carriers l = 5 -140 Å and with a Cooper pair size changing nonmonotonously in the range 450 -4000 Å. The parent ZrB 12 and LuB 12 borides are type-I superconductors, and Zr to Lu substitution induces a type-I -type-II phase transition providing a variation of the Ginzburg-Landau-Maki parameter in the limits 0.65   1,2  6. We argue in favor of the two-band scenario of superconductivity in Lu x Zr 1-x B 12 with gap values Δ 1 ~ 14 K and Δ 2 ~ 6 -8 K, with pairing corresponding to strong coupling limit ( e-ph ~ 1) in the upper band, and to weak coupling ( e-ph ~ 0.1 -0.4) in the lower one. A pseudogap Δ ps-gap ~ 60 -110 K is observed in Lu x Zr 1-x B 12 above T c . We discuss also the possibility of anisotropic single-band superconductivity with stripe-induced both pair-breaking and anisotropy, and analyze the origin of unique enhanced surface superconductivity detected in these model compounds.

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Lattice instability and enhancement of superconductivity in YB6

et al. 2017

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The superconducting and normal state characteristics of yttrium hexaboride (YB6) have been investigated for the single crystals with a transition temperatures Tc ranging between 6 K and 7.6 K. The extracted set of microscopic parameters [the coherence length ξ(0) ∼ 320÷340Å, the penetration depth λ(0) ∼ 1100÷1600Å and the mean free path of charge carriers l = 31÷58Å, the Ginzburg-Landau-Maki parameters κ1,2(0) ∼ 3.3÷4.8 and the superconducting gap ∆(0) ∼ 10.3÷14.8 K] confirms the type II superconductivity in "dirty limit" (ξ≫l ) with a medium to strong electron-phonon interaction (the electron-phonon interaction constant λ e-ph = 0.93÷0.96) and s-type pairing of charge carriers in this compound [2∆(0)/kB Tc ≈ 4]. The comparative analysis of charge transport (resistivity, Hall and Seebeck coefficients) and thermodynamic (heat capacity, magnetization) properties in the normal state in YB6 allowed to detect a transition into the cageglass state at T * ∼ 50 K with a static disorder in the arrangement of the Y 3+ ions. We argue that the significant Tc variations in the YB6 single crystals are determined by two main factors: (i ) the superconductivity enhancement is related with the increase of the number of isolated vacancies, both at yttrium and boron sites, which leads to the development of an instability in the hexaboride lattice; (ii ) the Tc depression is additionally stimulated by the spin polarization of conduction electrons emerged and enhanced by the magnetic field in the vicinity of defect complexes in the YB6 matrix.

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Raman scattering in ZrB12 cage glass

Cited by 6 publications

References 20 publications

Role of spin-glass behavior in the formation of exotic magnetic states in GdB6

Role of spin-glass behavior in the formation of exotic magnetic states in GdB6

Inhomogeneous superconductivity in LuxZr1−xB12 dodecaborides with dynamic charge stripes

Lattice instability and enhancement of superconductivity in YB6

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