Search results

1

Phonon Drag and Magnetic Anomalies of Thermopower in RB_{12} (R = Ho, Er, Tm, Lu)

100%

Glushkov V., Demishev S., Ignatov M., Khayrullin E., Sluchanko N., Shitsevalov N., Levchenko A., Filipov V., Flachbart K., Siemensmeyer K.

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EN

High precision measurements of the Seebeck coefficient S(T) were carried out on the single crystals of RB_{12} (R = Ho, Er, Tm, Lu) at temperatures 2-300 K. It was shown that the effects of phonon drag result from vibrations of rare earth ions (ħω_E≈10-33 meV) in the rigid framework structure of the B_{12} clusters and determine the main contribution to thermopower at intermediate temperatures (30-300 K). The correlated behavior of transport parameters favors the appreciable enhancement of spin fluctuations in the sequence of magnetic compounds (HoB_{12}-TmB_{12}) when approaching to the valence instability state in YbB_{12}. The giant increase in S(T) detected in the vicinity of the Néel temperature T_N for HoB_{12}, ErB_{12}, and TmB_{12} seems to result from the density of states renormalization caused by antiferromagnetic ordering.

2

Bulk and Local Magnetic Susceptibility of ErB_{12}

81%

Bogach A., Bogomolov L., Glushkov V., Demishev S., Sluchanko D., Sluchanko N., Shitsevalova N., Levchenko A., Filipov V., Flachbart K., Siemensmeyer K.

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EN

High precision measurements of magnetoresistance Δρ/ρ = f(T,H) and magnetization M(T,H) were carried out on single crystals of rare-earth dodecaboride ErB_{12} at temperatures in the interval 1.8-30 K in magnetic fields up to 70 kOe. The high accuracy of the experiments allowed us to perform numerical differentiation and analyze quantitatively the behavior of the derivative d(Δρ/ρ)/dH = f(T,H) and of the magnetic susceptibility χ(T,H) = dM/dH in paramagnetic and magnetically ordered (antiferromagnetic, T_N ≈ 6.7 K and T_M ≈ 5.85 K) phases of ErB_{12}. It was shown that negative magnetoresistance anomalies observed in present study in paramagnetic state of ErB_{12} may be consistently interpreted in the framework of a simple relation between resistivity and magnetization -Δρ/ρ ~ M^2.

3

Defect Mode in LaB_{6}

81%

Anisimov M., Bogach A., Glushkov V., Demishev S., Samarin N., Gavrilkin S., Mitsen K., Shitsevalova N., Levchenko A., Filippov V., Gabani S., Flachbart K., Sluchanko N.

Acta Physica Polonica A

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2014

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vol. 126

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issue 1

350-351

EN

The specific heat of high quality La^{N}B_{6} (N=10, 11, natural) single crystals is investigated in a wide range of temperatures 2 - 300 K. The obtained data allow to estimate correctly (i) the electronic γ· T term of specific heat (γ ≈ 2.4 mJ/(mol·K^{2})), (ii) the contribution from quasilocal vibrating mode of La^{3+} ions (Θ_{E} ≈ 150 - 152 K), (iii) the Debye-type term from rigid boron cages (Θ_{D} ≈ 1160± 40 K). Our data also suggest an additional defect-mode component (iv) which may be attributed to a contribution of 1.5% boron vacancies in LaB_{6}. The obtained results may be interpreted in terms of formation of two level systems, which appear when La^{3+} ions are displaced from their centrosymmetric positions in the cavities of rigid boron cages, apart from randomly distributed boron vacancies in the LaB_{6} matrix.

4

Hall Effect in GdB_{6}

81%

Anisimov M., Bogach A., Glushkov V., Demishev S., Samarin N., Shitsevalova N., Levchenko A., Filippov V., Kuznetsov A., Flachbart K., Sluchanko N.

Acta Physica Polonica A

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2014

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vol. 126

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issue 1

348-349

EN

The Hall effect of GdB_{6} has been studied on high quality single crystals in the temperature range 2-150 K and in magnetic field of 1 T. The obtained data allow to detect anomalies in the antiferromagnetic (AF) phase including (i) a drastic enhancement of negative Hall coefficient below T_{N1} ≈ 15.5 K and (ii) the appearance of an anomalous Hall effect at T_{N2} ≈ 4.7 K. Possible scenarios of the AF ground state formation are discussed.

5

Anisotropy of Magnetoresistance in HoB₁₂

81%

Khoroshilov A., Krasnorussky V., Bogach A., Glushkov V., Demishev S., Levchenko A., Shitsevalova N., Filipov V., Gabáni S., Flachbart K., Anisimov M., Siemensmeyer K., Sluchanko N.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

976-978

EN

We present results of precision measurements of magnetoresistance of isotopically pure Ho¹¹B₁₂ at low temperatures 2÷10 K in magnetic field up to 80 kOe of different orientation to the crystal axes. The data obtained revealed strong anisotropy of magnetoresistance and allowed us to reconstruct magnetic H-T phase diagrams for main crystallographic directions H || [001], [110], and [111]. Analysis of magnetoresistance derivatives allowed to conclude in favor of two main magnetoresistance contributions. Among of them the negative quadratic component is attributed to charge carriers scattering on a magnetic clusters of Ho³⁺ ions (4f component) and positive linear one may be explained in terms of scattering on a spin density waves (5d component).

6

Anisotropy of the Charge Transport in GdB₆

81%

Anisimov M., Glushkov V., Bogach A., Demishev S., Samarin N., Samarin A., Shitsevalova N., Levchenko A., Filipov V., Gábani S., Flachbart K., Sluchanko N.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

973-975

EN

The anisotropy of charge transport was investigated in the antiferromagnetic II state of GdB₆ from precise measurements of transverse magnetoresistance. Based on the data obtained we detected a complicated behavior of magnetoresistance curves which are characterized by the appearance of considerable hysteresis on the field and angular dependences below T_{N2}. Moreover it was shown that the system GdB₆ is sensitive to cooling-warming prehistory. The data analysis allowed to reconstruct magnetic H-T phase diagram of GdB₆ along main crystallographic directions (H||⟨001⟩,⟨110⟩,⟨111⟩) and to propose additional phase transition inside AF II phase at H₁ ≈ 0.5 T.

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6 Acta Physica Polonica A

2 2017

2 2014

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6 Demishev S.

6 Flachbart K.

6 Glushkov V.

6 Levchenko A.

6 Sluchanko N.

5 Bogach A.

5 Shitsevalova N.

4 Anisimov M.

4 Filipov V.

3 Samarin N.

3 Siemensmeyer K.

2 Filippov V.

1 Bogomolov L.

1 Gabani S.

1 Gabáni S.

1 Gavrilkin S.

1 Gábani S.

1 Ignatov M.

1 Khayrullin E.

1 Khoroshilov A.

1 Krasnorussky V.

1 Kuznetsov A.

1 Mitsen K.

1 Samarin A.

1 Shitsevalov N.

1 Sluchanko D.

Phonon Drag and Magnetic Anomalies of Thermopower in RB_{12} (R = Ho, Er, Tm, Lu)

Bulk and Local Magnetic Susceptibility of ErB_{12}

Defect Mode in LaB_{6}

Hall Effect in GdB_{6}

Anisotropy of Magnetoresistance in HoB₁₂

Anisotropy of the Charge Transport in GdB₆