Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 24

Number of results on page
first rewind previous Page / 2 next fast forward last

Search results

help Sort By:

help Limit search:
first rewind previous Page / 2 next fast forward last
1
Content available remote

Tunneling Spectroscopy Studies of SmB_6 and YbB_{12}

100%
Baťková M., Baťko I., Konovalova E., Shitsevalova N.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
255-258
EN
Reported electron tunneling studies of SmB_6 and YbB_{12} in the temperature region with a strongly temperature activated transport reveal a qualitative change of tunneling regime upon cooling. While the differential conductance curves above 50 K resemble the tunneling between two different metals, the spectra observed at 4.2 K are typical of the tunneling between a metal and a (narrow-gap) valence fluctuating semiconductor.
2
Content available remote

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

76%
Gabáni S., Flachbart K., Bednarčík J., Welter E., Filipov V., Shitsevalova N.
Acta Physica Polonica A
|
2014
|
vol. 126
|
issue 1
338-339
EN
We investigated the valence states of samarium ions in Sm deficient Sm_{1-x}B_{6} (x=0.03, 0.05, 0.08, 0.1 and 0.2) sintered samples, in single crystalline solid solutions Sm_{1-x}La_{x}B_{6} (x=0.16, 0.28, 0.4, 0.55 and 0.7) as well as in a SmB_{6} single crystal by X-ray absorption near edge structure (XANES) between 4.2 and 300 K. It was shown that the mixed valence state v_{Sm} of Sm-ions (v_{Sm} ≈ 2.51 for SmB_{6} at 4.2 K) in deficient 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 v_{Sm} increases with increasing vacancy level, whereas it decreases with increasing La^{3+} substitution. The obtained dependences of Sm-valence in SmB_{6} 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.
3
Content available remote

Phase Diagram of TmB_4 Probed by AC Calorimetry

76%
Kačmarčík J., Pribulová Z., Gabáni S., Samuely P., Siemensmeyer K., Shitsevalova N., Flachbart K.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
903-904
EN
TmB_4 is a frustrated system based on the Shastry-Sutherland lattice that exhibits complex magnetic properties. In this contribution the magnetic field B vs. temperature T phase diagram of TmB_4 has been studied by ultrasensitive AC calorimetry in the temperature range between 2.9 and 12 K and in magnetic fields up to 8 T. Apart from already known phases our measurements have recognized several new phase transitions suggesting that the phase diagram of TmB_4 is even more complex and deserves further studies.
4
Content available remote

Magnetic Phase Diagram of TmB_{4} under High Pressure

76%
Gabáni S., Pristáš G., Takáčová I., Flachbart K., Filipov V., Shitsevalova N., Siemensmeyer K.
Acta Physica Polonica A
|
2014
|
vol. 126
|
issue 1
356-357
EN
TmB_{4} is a Shastry-Sutherland frustrated system which exhibits very complex magnetic properties. In this contribution the phase diagram of magnetic field vs. temperature of TmB_{4} under hydrostatic pressure up to 26.5 kbar is investigated using sensitive ac-resistance measurements. Temperature and magnetic field dependences of resistance at various pressures were carried out in a piston cylinder pressure cell between 1.7 and 14 K and in magnetic fields up to 6 T. The obtained results exhibit shifts of ordering temperatures T_{N} as well as shifts of boundaries between different magnetic phases. The observed pressure dependences of T_{N} can be described by the relation d lnT_{N}/dp=+(0.16÷0.18) %/kbar. The effect of pressure on various interactions between magnetic ions in this compound is discussed.
5
Content available remote

Magnetic Field Enhancement of the Hall Effect in Dilute Magnetic System La_{1 - x}Ce_{x}B_6 (x ≤ 0.1)

76%
Bogach A., Glushkov V., Demishev S., Sluchanko N., Shitsevalova N., Fillipov V., Flachbart K.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
931-932
EN
Magnetic field dependences of the Hall coefficient R_{H} and resistivity have been studied in detail for dilute magnetic compounds La_{1-x}Ce_{x}B_6 (x ≤ 0.1) at temperatures 1.8-300 K. It was established that the regime of weak localization of charge carriers, which was observed in these heavy fermion systems below 30 K destroys gradually in magnetic field up to 8 T. Moreover, in addition to the strong negative magnetoresistance (Δρ/ρ ≈ 80%) a drastic enhancement of the negative Hall coefficient in magnetic field (Δ R_{H}/R_{H} ≈ 50%) has been deduced at liquid helium temperatures. The results of comprehensive analysis contradict the predictions of Kondo-impurity approach for this archetypal strongly correlated electron system in the dilute impurity limit. An alternative interpretation of La_{1-x}Ce_{x}B_6 properties is developed on the basis of spin-polaron approach, Pauli paramagnetism and the density of states renormalization effects at low temperatures.
6
Content available remote

Influence of Pressure on the Electron-Phonon Interaction in Superconductors

76%
Orendáč M., Gabáni S., Pristáš G., Gažo E., Shitsevalova N., Flachbart K.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
1039-1041
EN
The electron-phonon interaction is a very important and ubiquitous process in solids, affecting almost all their physical properties. In metals, where the relaxation processes depend on both electrons and phonons, all thermodynamic and transport properties are dictated by the electron-phonon interaction. A very strong manifestation of the electron-phonon interaction is related with the superconducting state. Here we report the effect of high pressure on the transport electron-phonon interaction, λ_{tr}, in superconducting systems such as YB_6 (T_c ≈ 7.5 K), Pb (T_c ≈7.2 K), Nb bulk or thin film (T_c ≈9.2 K), and in LaB_6 in which superconductivity was not yet observed. The expected pressure effect should correspond to the theoretically predicted negative pressure effect on T_c (except for Nb thin film and LaB_6). To determine the influence of pressure on λ_{tr}, we utilized the Bloch-Grüneisen fit (denoted also as "thermal spectroscopy") of the precise temperature dependence of resistivity measurements in the normal state up to a pressure of 2.8 GPa. Based on this fit the observed negative pressure effect on λ_{tr} values, dλ_{tr}/dp, are as follows: dλ_{tr}/dp ≈-0.045 GPa^{-1} for YB_6, dλ_{tr}/dp ≈-0.13 GPa^{-1} for Pb, dλ_{tr}/dp ≈-0.019 GPa^{-1} or -0.028 GPa^{-1} for Nb bulk or thin film, respectively, and dλ_{tr}/dp ≈-0.003 GPa^{-1} for LaB_6.
7
Content available remote

Magnetocaloric Effect in Geometrically Frustrated Magnetic Compound HoB_{12}

76%
Snyman J., Flachbart K., Gabani S., Reiffers M., Shitsevalova N., Siemensmeyer K., Strydom A.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
873-874
EN
The magnetocaloric effect of frustrated antiferromagnetic HoB_{12} is calculated. The isothermal entropy change Δ S characterising the magnetocaloric effect shows a small positive change upon magnetisation below the transition temperature T_{N}, indicating a small inverse magnetocaloric effect. At T_{N}, Δ S shows clear scaling behaviour with the applied magnetic field. The adiabatic temperature change Δ T shows paramagnetic behaviour above T_{N}, despite strong magnetic correlations that persist in this temperature region. The adiabatic temperature change calculated for HoB_{12} is appreciable.
8
Content available remote

Point-Contact Spectroscopy of Crystalline Electric Field of Heterocontacts PrB_6 and NdB_6 with Pt

76%
Vasil'ová M., Pristáš G., Reiffers M., Flachbart K., Rusz J., Shitsevalova N.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
267-270
EN
Point-contact spectra of single crystals PrB_6 and NdB_6 are presented. We observed maxima connected with crystalline electric field excitations in agreement with previous results for applied voltage V>8 mV. Moreover, we observed maxima at 6 mV (PrB_6) and 3 mV (NdB_6), which are probably connected with phonon modes. Moreover, we observed phonon peak at 10.6 mV in PrB_6. Further measurements in magnetic fields and crystalline electric field calculations are necessary.
9
Content available remote

Anomalous Transport Properties of Carbon-Doped EuB_6

64%
Batkova M., Batko I., Filipov V., Flachbart K., Sechovský V., Shitsevalova N., Šantavá E., Šebek J.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
893-894
EN
In the presented work we report electrical, magnetic and thermal properties of EuB_{6-x}C_{x} single crystals with an estimated value of x ≈ 0.07. Our studies reveal an antiferromagnetic phase transition at T_{N} ≈ 6.7 K. Electrical resistivity at zero magnetic field shows a pronounced resistivity maximum at T_{M} ≈ 7 K, just above the antiferromagnetic phase transition temperature. With increasing applied magnetic field the maximum moves to lower temperature and becomes totally suppressed at the field of 9 T. Observed magnetoresistance is negative in the whole studied temperature range 2-20 K, yielding a ratio of ρ(0 T, 7 K)/ρ(9 T, 7 K) ≈ 2.5. The origin of such magnetoresistance is associated with formation of mixed magnetic structure in the system due to fluctuation of carbon concentration.
10
Content available remote

^{11}B-NMR Study of SmB_6 under Pressure

64%
Pristáš G., Mito T., Kohara T., Gabáni S., Reiffers M., Flachbart K., Takeshita N., Shitsevalova N.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
895-896
EN
We present first experimental results of ^{11}B-NMR of SmB_6 under applied pressure. From measurement of nuclear spin-lattice relaxation time (T_1) we find that with applied pressure the value of activation gap E_{g} is decreasing. This decrease is larger than in case of other experimental techniques. We suppose that the enhancement of 1/T_1 in temperature range 20-100 K with applied pressure reflects not only a suppression of hybridization gap, but also changes in spin correlations.
11
Content available remote

Magnetic Field Influence on the Thermal Conductivity of PrB_6

64%
Priputen P., Reiffers M., Gabáni S., Flachbart K., Šantavá E., Šebek J., Alekseev P., Nefeodova E., Sadikov I., Shitsevalova N.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
383-386
EN
Results of thermal conductivity measurements on single crystalline PrB_6 sample in the temperature range of 2-30 K and in magnetic field up to 14 T are presented. The obtained results are discussed in order to estimate the electron, phonon, and magnetic contributions to thermal conductivity. Taking into account the results of electrical resistivity of this compound the temperature dependence of the reduced Lorentz function is determined.
12
Content available remote

Anomalies of Heat Capacity and Phase Transitions in Tm_{1-x}Yb_{x}B_{12}

64%
Sluchanko N., Azarevich A., Bogach A., Glushkov V., Demishev S., Gavrilkin S., Shitsevalova N., Fillipov V., Gabani S., Flachbart K.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
929-930
EN
In the system Tm_{1 - x}Yb_{x}B_{12} the specific heat has been studied in a wide range of Yb-concentration in the vicinity of the quantum critical point x_{C} ≈ 0.3. The results were obtained on high quality single crystalline samples of Tm_{0.7}Yb_{0.3}B_{12} compound placed near quantum critical point, both for antiferromagnetic metals (x < x_{C}) as well as for paramagnetic insulators (x > x_{C}) within a wide temperature range of 1.9-300 K in magnetic field up to 9 T. The temperature dependence of the magnetic contribution to specific heat for Tm_{0.74}Yb_{0.26}B_{12} shows a logarithmic divergence of the form C_{mag}/T∿-lnT at T<4 K, which may be attributed to the quantum critical regime, and it is suppressed by strong external magnetic field. The Schottky anomaly of the magnetic contribution to specific heat in Tm_{1 - x}Yb_{x}B_{12} has been established and analyzed in detail.
13
Content available remote

Magnetic Structure and Phase Diagram of TmB_4

64%
Gabáni S., Maťaš S., Priputen P., Flachbart K., Siemensmeyer K., Wulf E., Evdokimova A., Shitsevalova N.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
227-230
EN
Magnetic structure of single crystalline TmB_4 has been studied by magnetization, magnetoresistivity, and specific heat measurements. A complex phase diagram with different antiferromagnetic phases was observed below T_{N1}=11.7 K. Besides the plateau at half-saturated magnetization (1/2 M_S), also plateaus at 1/9, 1/8 and 1/7 of M_S were observed as a function of applied magnetic field Bparallel c. From additional neutron scattering experiments on TmB_4, we suppose that these plateaus arise from a stripe structure which appears to be coherent domain boundaries between antiferromagnetic-ordered blocks of 7 or 9 lattice constants. The received results suggest that the frustration among the Tm^{3+} magnetic ions, which maps to a geometrically frustrated Shastry-Sutherland lattice, leads to a strong competition between antiferromagnetic and ferromagnetic order. Thus, stripe structures in intermediate field appear to be the best way to minimize the magnetostatic energy against other magnetic interactions among the Tm ions combined with very strong Ising anisotropy.
14
Content available remote

Angular Dependences of ESR Parameters in Antiferroquadrupolar Phase of CeB₆

64%
Semeno A., Gilmanov M., Sluchanko N., Krasnorussky V., Shitsevalova N., Filipov V., Flachbart K., Demishev S.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
1060-1062
EN
Angular dependences of ESR line parameters (g-factor and linewidth Δ H) were experimentally explored in the antiferroquadrupolar phase of heavy fermion system CeB₆ at T=1.8 K. The data were obtained in two experimental geometries with different mutual directions of the wavevector k and the external magnetic field H at frequency of f=60 GHz. A g-factor anisotropy was found: while g-factors for [110] and [111] directions are close to each other (g ≈1.6), it is considerably higher (g ≈1.75) for [100]. The obtained angular dependence g(Θ) was compared with the theoretically predicted g-factor behavior for the Γp₈ state of Ce³⁺ ion in antiferroquadrupolar phase of CeB₆. It turns out that the experimental g-factor is considerably smaller at all angles than the theoretically calculated limits (2
15
Content available remote

Reentrant Metal-Insulator Transition in Ca_{1-x}Eu_{x}B_{6}

64%
Glushkov V., Anisimov M., Baybakov R., Demishev S., Filippov V., Flachbart K., Kuznetsov A., Shitsevalova N., Sluchanko N.
Acta Physica Polonica A
|
2014
|
vol. 126
|
issue 1
294-295
EN
Resistivity, Hall and Seebeck effects have been studied on single crystals of Ca_{1-x}Eu_{x}B_{6} (0 ≤ x ≤ 1) at temperatures 2-300 K and in magnetic fields up to 8 T. An insulating ground state is found to be limited by narrow range of Eu doping 0.6 ≤ x ≤ 0.8. This region is characterized by an enhanced colossal magnetoresistance (CMR), which reaches values of ρ(0)/ρ(7T) > 10^{6} for x = 0.63 at T < 10 K. Decreasing of Eu content in Ca_{1-x}Eu_{x}B_{6} below x* ≈ 0.6 restores the metallic ground state with moderate resistivity (ρ ~ 1 ÷ 5 mΩ·cm) and CMR amplitude (ρ(0)/ρ(7T) < 7). The second metal-insulator transition (MIT) in Ca_{1-x}Eu_{x}B_{6} is observed beyond the whole conductivity region found earlier in the narrow range of Eu doping (0.7 ≤ x ≤ 0.8). The correlation between the enhanced CMR amplitude, the onset of positive diffusive thermopower and the elevation of anomalous Hall effect, determined for Eu content 0.6 ≤ x ≤ 0.85, favors the idea that a smooth change of band structure is the main factor governing the reentrant MIT in Ca_{1-x}Eu_{x}B_{6}.
16
Content available remote

Charge Transport and Magnetism in Eu_{1-x}Ca_{x}B_6

52%
Glushkov V., Anisimov M., Batko I., Batkova M., Bogach A., Demishev S., Filipov V., Flachbart K., Kuznetsov A., Sannikov I., Shitsevalova N., Sluchanko N.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
891-892
EN
Transport, magnetic and thermal properties of substitutional solid solution Eu_{1 - x}Ca_{x}B_6 single crystals (0 ≤ x ≤ 0.244) have been studied at 1.8 ≤ T ≤ 300 K and in magnetic fields up to 8 T. Calcium doping is shown to result in a metal-insulator transition, which occurs at x_{MIT} ≈ 0.2. In vicinity of metal-insulator transition the effect of colossal magnetoresistance is found to be very sensitive to Ca content, the amplitude varying from Δ = [ ρ (0)- ρ (8T)]/ρ(8T) ≈1.4×10^2 to Δ ≈ 7.5 × 10^3 for 0.14 ≤ x ≤ 0.16. The analysis of magnetic contribution to heat capacity shows that a large amount of magnetic entropy ( ≈ 30%) releases in Eu_{0.845}Ca_{0.155}B_6 when moving from the Curie temperature T_{C} ≈ 5.5 K to the characteristic one T* ≈ 30 K. This observation as well as the large amplitude of low field colossal magnetoresistance effect and the deviation of magnetic susceptibility from the Curie-Weiss law detected for x = 0.155 compound in the interval T_{C} ≤ T ≤ T* seem to be associated with magnetic phase separation induced by Ca doping.
17
Content available remote

Magnetoresistance Anisotropy and Magnetic H-T Phase Diagram of Tm_{0.996}Yb_{0.004}B_{12}

52%
Sluchanko N., Azarevich A., Bogach A., Glushkov V., Demishev S., Gavrilkin S., Gabani S., Flachbart K., Shitsevalova N., Filipov V., Vanacken J., Moshchalkov V., Stankiewicz J.
Acta Physica Polonica A
|
2014
|
vol. 126
|
issue 1
332-333
EN
The antiferromagnetic ground state has been studied by transverse magnetoresistance, heat capacity and magnetization measurements, which were carried out on high quality single crystals of Tm_{0.996}Yb_{0.004}B_{12} dodecaboride in strong magnetic fields at liquid helium temperatures. Both antiferromagnetic-paramagnetic (AF-P) and spin-orientation (AF1-AF2) phase transitions have been observed, and allowed to construct a complicated magnetic H-T phase diagram for this compound. Strong magnetoresistance anisotropy was found both in AF states (ρ(H||[110])/ρ(H||[111])~ 1.2 at H~ 20 kOe) and at the critical field of AF-P transition (H_{N}[100]/H_{N}[111]~ 1.25) in this magnetic metal with a simple fcc crystal structure.
18
Content available remote

Anisotropy of Magnetoresistance in HoB₁₂

52%
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
|
2017
|
vol. 131
|
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).
19
Content available remote

Anisotropy of the Charge Transport in GdB₆

52%
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
|
2017
|
vol. 131
|
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.
20
Content available remote

Superconductivity in Lu_xZr_{1-x}B_{12} Dodecaborides with Cage-Glass Crystal Structure

52%
Sluchanko N., Azarevich A., Bogach A., Gavrilkin S., Glushkov V., Demishev S., Mitsen K., Shitsevalova N., Filippov V., Gabani S., Flachbart K.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
1036-1038
EN
We probed the evolution of the superconducting transition temperature T_c and the normal state parameters of Lu_xZr_{1-x}B_{12} solid solutions employing resistivity, heat capacity and magnetization measurements. In these studies of high-quality single crystals it was found that there are two types of samples with different magnetic characteristics. An unusually strong suppression of superconductivity in Lu_xZr_{1-x}B_{12} with a rate dT_c/dx=0.21 K/at.% of Lu was observed previously on the first "magnetic" set of crystals, and it was argued to be caused by the emergence of static spin polarization in the vicinity of non-magnetic lutetium ions. On the contrary, the second (current) set of "nonmagnetic" crystals demonstrates a conventional T_c(x) dependence with a rate dT_c/dx=0.12 K/at.% of Lu which is typical for BCS-type superconductors doped by nonmagnetic impurities. The reason for this difference is yet unclear. Moreover, the H-T phase diagram of the superconducting state of Lu_xZr_{1-x}B_{12} (0 ≤ x ≤ 1) solid solutions has been deduced from magnetization measurements.
first rewind previous Page / 2 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.