Autor: Feher, A. - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Magnetocaloric Effect in NiCl₂(bipy) at Low Temperatures
Autorzy:: Ráczová, K.
Čižmár, E.
Feher, A.
Tematy:: 75.30.Sg
75.30.Gw
75.10.Pq; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1032298.pdf Link otwiera się w nowym oknie
Opis:: Magnetothermal properties of the compound NiCl₂(bipy), where bipy = 4,4'-bipyridine, were studied. The single-ion anisotropy of Ni(II) ions was estimated and its influence on magnetocaloric effect in NiCl₂(bipy) was investigated. Above the metamagnetic transition a maximum in the isothermal change of the magnetic entropy is reached near 11 K at field change from 0T to 7T with peak value -ΔS = 6J K¯¹ kg¯¹. The temperature dependence of ΔS above 7K agrees with the assumed easy-axis type of single-ion anisotropy. The inverse magnetocaloric effect, typical for ordered antiferromagnets, was observed in the ordered state of NiCl₂(bipy) only for isothermal magnetization in small fields up to 2T.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Superconductivity of Niobium Thin Films in the BiOCl/Nb Heterostructures
Autorzy:: Lotnyk, D.
Komanický, V.
Bunda, V.
Feher, A.
Tematy:: 74.25.F-
68.35.bg
74.45.+c; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1032733.pdf Link otwiera się w nowym oknie
Opis:: In the current paper, electrical transport properties of 25 nm thick Nb films sputtered on the photosensitive semiconductor BiOCl were investigated in the temperature range 7.5 K ≤ T ≤8.5 K. The influence of green (532 nm) and red (640 nm) laser excitations on resistive superconducting transitions of the niobium thin films on a silicon glass and BiOCl single crystal substrates were studied. The temperature dependences of the resistivity for Nb are in good agreement with the McMillan model which indicates the strong influence of the inverse proximity effect induced by the interface. The increased influence of the BiOCl/Nb interface under laser excitation corresponds to the raising of the ratio of the density of normal to superconductivity carriers in the Tıghtarrow0 limit and this observation is in agreement with the photoconductivity study of BiOCl single crystals.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: EPR Spectra of the Genuine-Organic and Metal-Organic TCNQ-Based Anion Radical Salts
Autorzy:: Botko, M.
Čižmár, E.
Kajňaková, M.
Feher, A.
Tematy:: 75.50.Xx
76.30.-v; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1368637.pdf Link otwiera się w nowym oknie
Opis:: We have measured the electron paramagnetic resonance spectra of genuine-organic anion-radical salts $[Me-2,6-di-Me-Py](TCNQ)_{2}$, $[Me-3,5-di-Me-Py](TCNQ)_{2}$, $[N-Me-OH-Me-Py](TCNQ)_{2}$, $[N-Et-OH-Me-Py](TCNQ)_{2}$, and metal-organic anion-radical salt $[Mn-phen_{3}](TCNQ)_{2}$·$H_{2}O$ in the temperature range from 2 K to 300 K in the X-band frequency range. A comparison study of the shape of spectra, g-factors and linewidths with respect to the composition and crystal structure of studied compounds is presented. While the genuine-organic anion-radical salts display a typical EPR response originating from TCNQ pairs, the spectra of metal-organic anion-radical salt are dominated by the contribution of transition metal.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Thermodynamic and Magnetotransport Properties of High Quality $Na_{0.77}CoO_{2}$ Single Crystals
Autorzy:: Baran, A.
Zorkovská, A.
Kajňaková, M.
Lin, C.
Feher, A.
Tematy:: 75.20.Hr
75.40.Cx
75.47.-m; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1371577.pdf Link otwiera się w nowym oknie
Opis:: Heat capacity and electrical resistivity of high-quality $Na_{0.77}CoO_{2}$ single crystals was systematically studied as a function of temperature and magnetic field. Anomalies at 20 K have been observed both in the heat capacity and the electrical resistivity. The broad bump in the heat capacity indicates a smeared magnetic phase transition. Magnetic fields up to 9 T, oriented perpendicularly to the ab plane, reduce the temperature of this anomaly in accordance with the assumption of A-type antiferromagnetic ordering. The low temperature upturn observed in resistivity below 20 K for slow cooling is also suppressed by the magnetic field. This anomaly is probably the consequence of the interplay of several different mechanisms, including the Kondo effect, electron-electron interactions, and electron-phonon scattering.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Effect of Layered Structure on the Lattice Heat Capacity of the Rare Earth Molybdates
Autorzy:: Feher, A.
Stefányi, P.
Orendáčová, A.
Anders, E.
Zvyagin, A.
Tematy:: 65.40.-f
63.20.-e; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1887811.pdf Link otwiera się w nowym oknie
Opis:: Temperature dependence of the heat capacity of layered rare earth molybdates was measured in the temperature range from 0.4 K to 23 K. It is shown that the temperature dependence of the lattice heat capacity can be described by the "T", where n ≠ 3. It is shown that differently from KDy(MoO$\text{}_{4}$)$\text{}_{2}$ and CsDyEu(MoO$\text{}_{4}$)$\text{}_{2}$ for CsDy(MoO$\text{}_{4}$)$\text{}_{2}$ and CsGd(MoO$\text{}_{4}$)$\text{}_{2}$ we obtained the temperature term with n < 3, which can be connected with the 2D behaviour, manifested also in the so-called membrane effect.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Slow Magnetic Relaxation in the Highly Anisotropic Layered Crystal CsNd(MoO₄)₂
Autorzy:: Tkáč, V.
Orendáčová, A.
Tarasenko, R.
Orendáč, M.
Feher, A.
Tematy:: 76.60.Es
76.30.Kg
75.30.Gw
75.40.Gb; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1030440.pdf Link otwiera się w nowym oknie
Opis:: The present work is devoted to the magnetic relaxation study of the single crystal CsNd(MoO₄)₂ a layered rare-earth dimolybdate. AC susceptibility measurements performed in magnetic fields up to B=5 T applied along the easy and hard axis with frequency f ≈1 kHz revealed rather complex field-induced slow magnetic relaxation. Two relaxation regimes in different magnetic field intervals connected with magnetic interactions and possible single-ion relaxation mechanism were observed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Experimental Study of Magnetic Properties of Alumina Ceramics
Autorzy:: Tarasenko, R.
Orendáčová, A.
Orendáč, M.
Kajňaková, M.
Feher, A.
Tematy:: 75.20.-g
75.60.Ej
75.40.-s; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1535536.pdf Link otwiera się w nowym oknie
Opis:: Magnetic properties of alumina ceramics were studied within a program focused at design of microcalorimeters and experimental setup for specific heat and magnetocaloric measurements. The investigations were concentrated on the determination of amount of magnetic impurities that can significantly influence results of physical measurements at low temperatures. Our experimental studies of heat capacity, susceptibility and magnetization clearly indicate that alumina ceramics contains magnetic impurities, primarily ions with spin 5/2. The average concentration of magnetic ions was estimated, n ≈ 2000 ppm. More details of analysis of experimental data are discussed in the paper.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Magnetocaloric Study of S=1/2 Low-Dimensional Heisenberg Antiferromagnet $[Cu\text{(phen)}(H_2O)_2]SO_4$
Autorzy:: Sedláková, L.
Orendáč, M.
Kajňaková, M.
Orendáčová, A.
Feher, A.
Tematy:: 75.30.Sg
75.50.Ee; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1813815.pdf Link otwiera się w nowym oknie
Opis:: We present the experimental study of magnetocaloric effect on powder sample $[Cu\text{(phen)}(H_2O)_2]SO_4$ (phen = phenantroline = $C_{12}H_8N_2$) in the temperature range from nominally 0.2 K to 4 K and in magnetic fields up to 2 T. The values of total entropy were extracted from the experimental data obtained by adiabatic demagnetization. The comparison was performed with the temperature dependence of the entropy for S=1/2 paramagnet calculated at selected magnetic fields. The deviations observed below 0.6 T were attributed to internal field mediated by exchange coupling. In addition, the temperature response observed in $[Cu\text{(phen)}(H_2O)_2]SO_4$ revealed very short relaxation time below 1 K. The comparison of the behavior observed at the end of the demagnetization in $[Cu\text{(phen)}(H_2O)_2]SO_4$ and other systems suggests that the magnetocaloric effect can serve as an alternative tool for studying slow magnetic relaxation.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Physical Properties of "HTSC/Photosemiconductor" Micro- and Nanoplates Based Junctions
Autorzy:: Bunda, V.
Bunda, S.
Vashchuk, F.
Feher, A.
Kováč, J.
Tematy:: 85.25.Hv
74.45.+c
74.25.F-
74.55.+v; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1535401.pdf Link otwiera się w nowym oknie
Opis:: In this paper we report the formation process and electrophysical properties of 'high temperature superconductor $(YBa_2Cu_3O_{7 - x})$/photosemiconductor (BiOCl:Ti)' micro- and nanoplates based junction. The energy band model of ≪HTSC-semiconductor≫ junction is proposed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Experimental Studies of S=1 Heisenberg Planar Antiferromagnetic Chain Ni(C$\text{}_{11}$H$\text{}_{10}$N$\text{}_{2}$O)$\text{}_{2}$Ni(CN)$\text{}_{4}$
Autorzy:: Čizmár, E.
Černák, J.
Orendáč, M.
Herrmannsdörfer, T.
Feher, A.
Tematy:: 75.40.Cx
71.20.Be
75.50.Ee; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2013230.pdf Link otwiera się w nowym oknie
Opis:: In this paper we discuss the results of experimental studies of specific heat and magnetic susceptibility of chain compound Ni(C$\text{}_{11}$H$\text{}_{10}$N$\text{}_{2}$O)$\text{}_{2}$Ni(CN)$\text{}_{4}$. We have observed a Schottky type anomaly at T=2.2 K in a temperature dependence of specific heat and the compound was identified as a S=1 Heisenberg antiferromagnetic chain with the subcritical exchange coupling D/k$\text{}_{B}$=5 K, D/|J|=5.2 and the strong in-plane anisotropy E/k$\text{}_{B}$=2.8 K. It has been found that the in-plane anisotropy affects the region of validity of a diluted exciton model [1] and a strong coupling model [2] for S=1 Heisenberg chains with the strong planar anisotropy. The analysis suggests that the in-plane anisotropy should be considered in any attempt to find a compound potentially located in the boundary of Haldane and "large-D" phases.
Dostawca treści:: Biblioteka Nauki

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