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A Contribution of Thermoelectric Properties of the Quaternary Chalcogenide Compound Tl_2GaInSe_4 Crystal

100%
Al Orainy R.
Acta Physica Polonica A
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2013
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vol. 124
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issue 4
728-731
EN
Thermoelectric transport measurements were made on single crystal samples of Tl_2GaInSe_4. The crystal was prepared by a special design based on the Bridgman technique. Measurements of thermoelectric power were carried out in a special high vacuum-tight calorimeter when the direction of temperature gradient is perpendicular to the cleavage plane. The measurements covered a temperature range extending from 300 to 725 K. The results indicate P-type conductivity for our investigated samples. At room temperature the value of thermoelectric power was 735 μV/deg. The electron to hole mobility ratio was found to be 1.35. The effective mass of holes at room temperature was evaluated as 4.635×10^{-29} kg, while for electron was equal to 8.468×10^{-31} kg. The relaxation time of majority and minority carriers was estimated as τ_p=2.968×10^{-10} s and τ_n=7.326×10^{-12} s, respectively. Also, the diffusion coefficient of holes and electrons at room temperature was calculated and found to be 265.132 cm^2/s and 358.139 cm^2/s, respectively. The diffusion length of holes and electrons are found to be L_p=2.805×10^{-4} cm and L_n=5.122×10^{-5} cm. In addition to these pronounced parameters, the efficiency of thermoelectric element (figure of merit) was evaluated which leads to better applications in many fields.
2
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Preparation and Switching Behavior Characterization οf Some Quaternary Thallium Chalcogenide Compounds

100%
Al Orainy R., Nagat A.
Acta Physica Polonica A
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2013
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vol. 123
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issue 1
121-125
EN
Investigation of the switching phenomenon on TlGaSSe single crystal revealed that it is typical for a memory switch. The switching process takes place with both polarities on the crystal and have symmetrical shapes. Current-voltage characteristics (CVC) of symmetrical Ag/TlGaSSe/Ag structures exhibit two distinct regions, high resistance "OFF" state and low resistance "ON" state having negative differential resistance. In addition, TlGaSSe is a quarternary semiconductor exhibiting S-type I-V characteristics. The experimental results indicate that the phenomenon in our sample is very sensitive to temperature; light intensity and sample thickness. The switching parameters were checked under the influence of different factors of the ambient condition. The present investigation is the first one on switching phenomenon of TlGaSSe.
3
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Superconductivity and Ferromagnetism in La_{0.67}Sr_{0.33}MnO₃/YBa₂Cu₃O₇ Nanosized Heterostructures

51%
Lochmajer H., Matusiak M., Urbanik G., Przyslupski P., Rogacki K.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
588-592
EN
In this work we present recent experimental studies of heterostructures composed of ferromagnetic La_{0.67}Sr_{0.33}MnO₃ (LSMO) and superconducting YBa₂Cu₃O₇ (YBCO) multilayers grown by dc sputtering method. The transport and magnetic properties of the large set of heterostructures were investigated in a wide temperature range from 2 to 400 K and in fields up to 12.5 T. The resistivity and the upper critical field were measured for samples with the plane active dimensions 1.5× 5 mm². The Nernst effect was studied in the mixed state revealing the characteristic temperature dependence of the Nernst signal which was correlated with variation of the upper critical field. We have observed an influence of the magnetic LSMO layer on the superconducting properties of the adjacent YBCO layer which consists in a substantial reduction of the superconducting critical temperature and a small lowering of the upper critical field.
4
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Applicable Damage of High-T_{ rm c} YbaCuO Superconducting Tapes by Current and Laser Pulses

51%
Kiprijanovič O., Ašmontas S., Anisimovas F., Gradauskas J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
256-258
EN
Damage and irreversible damage of YBaCuO tapes with high density current after switching from superconducting to normal state are investigated. Quasi-homogeneous current distribution across the tape in superconducting state can cause perfect tape damage or irreversible damage when current is slightly above critical value. The model of the tape heating during the optically initiated switching from superconducting to normal state is proposed. Analysis of causes inducing damage shows necessity to consider 0.5T_{m} damage criterion because of strong current influence on the damage processes. Possible damage mechanisms are described and crack tips motion simultaneously with switching from superconducting to normal state is considered. Application of optically illuminated YBaCuO tapes with nanosecond duration current pulses on the base of the described mechanisms is proposed.
5
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Phonon Contribution in Thermodynamics and Transport Properties of Ultrathin Ceramic Films

45%
Jaćimovski S., Šetrajčić J., Jaćimovski M., Stojanović V.
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vol. 126
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issue 3
811-820
EN
The dispersion law, density states of phonons, thermodynamics properties and thermal conductivity was analyzed in this paper. It has been shown that at low temperatures, thermal conductivity of thin film is considerably lower that of bulk-structure. It turned out that phonons in thin film require activation energy for exciting. This leads to extremely low specific heat and specific conductivity at low temperatures. Consequences of quoted facts were discussed in detail and their influence on kinetic and thermodynamic properties of thin films is estimated.
6
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Coexistence of Ferromagnetism and Superconductivity in Rapidly Quenched Ni_2NbSn Heusler Alloy

38%
Kanuch P., Ryba T., Gamcová J., Kanuchova M., Durisin M., Saksl K., Vargova Z., Varga R.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1057-1059
EN
We present the study on production and structural, electric and magnetic properties of superconductive Ni₂NbSn Heusler alloy. The sample has been produced by melt-spinning method using tangential speed of copper wheel 20 m/s. Polycrystalline structure has been obtained showing single phase with B2 disorder with lattice constant a=6.1654 Å. Resistance measurement shows superconductive behavior with critical temperature close to 5 K. Magnetic measurements also exhibit diamagnetic contribution from superconductive phase. Additionally, the ferromagnetic state has been observed below 20 K, which points to the coexistence of magnetic and superconducting state.
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