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Wyświetlanie 1-15 z 31
Tytuł:
Magnetocaloric Effect in $NdNi_4Si$ Compound
Autorzy:
Falkowski, M.
Toliński, T.
Kowalczyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/1429061.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Sg
75.30.Kz
75.47.Np
75.40.-s
Opis:
On the basis of the thermodynamic approach, we report the magnetocaloric properties of the ternary ferromagnetic $NdNi_4Si$ compound with magnetic phase transition temperature $T_{C}$ at 8 K. The saturated magnetic moment in H = 9 T is equal to 1.5 $μ_{B}$/f.u. at 4.2 K and the compound crystallizes in the hexagonal $CaCu_5$-type structure (space group P6/mmm). The magnetocaloric effect was calculated in terms of the isothermal magnetic entropy change Δ $S_{M}$ as well as the adiabatic temperature change Δ $T_{ad}$ using the specific heat data and magnetization measurements. Within the second order phase transition significant values of these parameters have been observed.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1290-1292
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Specific Heat of $YbNi_4Si$ Compound
Autorzy:
Falkowski, M.
Kowalczyk, A.
Toliński, T.
Powiązania:
https://bibliotekanauki.pl/articles/1813487.pdf
Data publikacji:
2008-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.80.Pv
65.40.Ba
75.20.Hr
Opis:
The specific heat of $YbNi_4Si$ has been analyzed considering the electronic contribution and the lattice contributions in frames of the Debye model. Based on the specific heat measurements, the electronic specific heat coefficient γ = 25 mJ $mol^{-1} K^{-2}$ and the Debye temperature $θ_D$ = 320 K were derived. This small value shows that $YbNi_4Si$ cannot be classified as a heavy fermion system. These studies are completed by magnetic susceptibility, X-ray photoemission spectroscopy, and electrical resistivity.
Źródło:
Acta Physica Polonica A; 2008, 113, 2; 641-644
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Negative Magnetisation and Absence of Superconductivity in RFe$\text{}_{4}$Al$\text{}_{8}$ (R=Lu, Yb) Compounds
Autorzy:
Andrzejewski, B.
Kowalczyk, A.
Toliński, T.
Powiązania:
https://bibliotekanauki.pl/articles/2046747.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Dd
75.50.-y
75.50.Ee
51.60.+a
74.70.-b
Opis:
We report researches for superconductivity and the effect of negative magnetisation in the RFe$\text{}_{4}$Al$\text{}_{8}$ (R = Lu, Yb) compounds by means of magnetic measurements and microwave absorption. Contrary to the earlier reports we do not confirm the existence of any traces of superconductivity in these compounds. Instead of the superconductivity and the Meissner effect, the YbFe$\text{}_{4}$Al$\text{}_{8}$ compound exhibits the effect of negative magnetisation, whereas the LuFe$\text{}_{4}$Al$\text{}_{8}$ compound shows an exact antiferromagnetic behaviour.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 561-564
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermoelectric Properties of $CeCu_4Ag$ Compound
Autorzy:
Kowalczyk, A.
Toliński, T.
Falkowski, M.
Timko, M.
Powiązania:
https://bibliotekanauki.pl/articles/1534756.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.80.-g
72.15.Cz
72.20.Pa
Opis:
The magnetic and electronic properties including electrical resistivity, thermal conductivity and thermopower are discussed for the heavy fermion $CeCu_4Ag$ compound. The electrical resistivity shows a Kondo-like logarithmic increase up to a maximum at T = 75 K. Thermopower is positive over the whole temperature range and below $T_\text{max}$ = 25 K falls rapidly. The measured thermal conductivity of the $CeCu_4Ag$ compound increases with increasing temperature.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 936-937
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stimulated and Laser Emission in CdZnTe/CdMnTe Double Quantum Well Heterostructures
Autorzy:
Kowalczyk, L.
Karczewski, G.
Wojtowicz, T.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933829.pdf
Data publikacji:
1995-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.45.+h
71.55.Gs
Opis:
Stimulated emission by optical excitation has been investigated in CdZnTe/CdMnTe quantum well heterostructures. Laser action has been achieved at 4.2 K and at 77 K with relatively low threshold values of the excitation intensity. Photοluminescence excitation spectra of the stimulated emission were obtained indicating that the optical gain involves exciton-exciton inelastic scattering.
Źródło:
Acta Physica Polonica A; 1995, 88, 4; 787-790
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Laser Induced Fluorescence of Indium Vapour
Autorzy:
Weyh, T.
Kopystyńska, A.
Kowalczyk, P.
Radzewicz, C.
Powiązania:
https://bibliotekanauki.pl/articles/1891958.pdf
Data publikacji:
1991-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.20.Kf
34.50.Fa
Opis:
Indium vapour was illuminated with laser light in the wavelength range 350-372 nm and at 410.3 nm. A few fluorescence bands of In$\text{}_{2}$ as well as a strong background emission of indium-quartz compounds were observed. An evidence of energy transfer processes in indium vapour was found.
Źródło:
Acta Physica Polonica A; 1991, 80, 6; 801-804
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of misfit strain in (Ga,Mn)(Bi,As) epitaxial layers on their magnetic and magneto-transport properties
Autorzy:
Levchenko, K.
Andrearczyk, T.
Domagała, J.
Sadowski, J.
Kowalczyk, L.
Szot, M.
Figielski, T.
Wosiński, T.
Powiązania:
https://bibliotekanauki.pl/articles/1160667.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
61.05.cp
78.20.Ls
73.50.Jt
75.30.Gw
Opis:
Effect of misfit strain in the layers of (Ga,Mn)(Bi,As) quaternary diluted magnetic semiconductor, epitaxially grown on either GaAs substrate or (In,Ga)As buffer, on their magnetic and magneto-transport properties has been investigated. High-resolution X-ray diffraction, applied to characterize the structural quality and misfit strain in the layers, proved that the layers were fully strained to the GaAs substrate or (In,Ga)As buffer under compressive or tensile strain, respectively. Ferromagnetic Curie temperature and magneto-crystalline anisotropy of the layers have been examined by using magneto-optical Kerr effect magnetometry and low-temperature magneto-transport measurements. Post-growth annealing treatment of the layers has been shown to enhance the hole concentration and the Curie temperature in the layers.
Źródło:
Acta Physica Polonica A; 2016, 129, 1a; A-90-A-93
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Valence Band and Core Levels of $Ce_5Ni_2Si_3$ Crystal Studied by X-ray Photoemission Spectroscopy
Autorzy:
Toliński, T.
Kowalczyk, A.
Chełkowska, G.
Mihalik, M.
Timko, M.
Powiązania:
https://bibliotekanauki.pl/articles/1813673.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Eh
82.80.Pv
Opis:
The crystal of $Ce_5Ni_2Si_3$ was prepared by the Czochralski method. The X-ray photoemission spectroscopy was measured for the valence band and the core levels. Based on the Ce(3d) doublet and its satellites a small value of the hybridization parameter of the f-states with the conduction electrons Δ=4 meV and the f-occupancy $n_f$ close to 1 were found. X-ray photoemission spectroscopy shows that the region between 0 and 3 eV is predominated by the Ni(3d) and Ce(4f) peaks. Some features of the multiplet structure of the Ce(4f) states are also visible close to the Fermi level.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 327-330
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-Ray Magnetic Circular Dichroism Studies on $CeNi_4B$
Autorzy:
Toliński, T.
Cezar, J.
Wende, H.
Kowalczyk, A.
Baberschke, K.
Powiązania:
https://bibliotekanauki.pl/articles/1810402.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Lp
75.20.Hr
78.70.Dm
79.60.-i
78.20.Ls
Opis:
The $CeNi_4B$ compound is a mixed-valence system. It is a paramagnet with $μ_\text{eff}$= 0.52 $μ_{B}$/f.u. and the paramagnetic Curie temperature θ= -10.7 K. In the present research we complete our previous magnetic susceptibility and X-ray photoemission measurements with new studies by the X-ray magnetic circular dichroism method. The observation of the Ce $M_{4,5}$ edges carried out with X-ray magnetic circular dichroism confirms the mixed-valence state deduced previously from X-ray photoemission spectroscopy. Moreover, we report on the measurements of the Ni $L_{2,3}$ edges, which enable verification of the Ni contribution to the magnetism of this compound.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 129-131
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties and Magnetocaloric Effect of $DyNi_{4}Si$
Autorzy:
Synoradzki, K.
Kowalski, W.
Falkowski, M.
Toliński, T.
Kowalczyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/1367640.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Lp
75.30.Sg
75.40.Cx
81.20.Ev
Opis:
The magnetic properties and magnetocaloric effect (MCE) in $DyNi_{4}Si$ have been studied by the magnetization and specific heat measurements. The saturation magnetic moment in $μ_{0}H$=9 T is equal to 7.9 $μ_{B}$/f.u at 4.2 K. A significant MCE has been observed around the second order phase transition at $T_{C}$=11 K. The maximum magnetic entropy change is -Δ $S_{M}$=14.5 J $kg^{-1}K^{-1}$ for the magnetic field change of 9 T.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 162-163
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heat Capacity of Heavy Fermion Compound $CeCu_4Ga$ in High Magnetic Fields
Autorzy:
Kowalczyk, A.
Toliński, T.
Reiffers, M.
Zapotoková, M.
Falkowski, M.
Gažo, E.
Powiązania:
https://bibliotekanauki.pl/articles/1810399.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.40.Ba
71.20.Eh
71.27.+a
Opis:
The heat capacity in the applied magnetic field up to 9 T, susceptibility and magnetization of polycrystalline $CeCu_{4}Ga$ are presented. Magnetic ordering was not observed down to 2 K. For temperature T < 200 K a Curie-Weiss behavior is observable giving an effective magnetic moment $μ_\text{eff}$ =2.53 $μ_{B}$/f.u. The experimental value of $μ_\text{eff}$ is close to the calculated one for a free $Ce^{3+}$ ion ($μ_\text{eff}$ = 2.54 $μ_{B}$/f.u.), thus indicating the presence of well localized magnetic moments carried by the stable $Ce^{3+}$ ions. At low temperatures the electronic heat capacity coefficient value depends strongly on the temperature range used for the extrapolation and applied magnetic field. We observe a typical heavy fermion behavior with γ value of about 380 mJ $\text{mol}^{-1} K^{-2}$ obtained from extrapolation to T = 0 K of the temperature range above 7 K. However, extrapolation of the lowest temperatures range yields the γ value of 3.3 J $\text{mol}^{-1} K^{-2}$.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 123-125
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heat Capacity Studies of $NdNi_4Si$ Compound
Autorzy:
Falkowski, M.
Reiffers, M.
Zapotoková, M.
Kowalczyk, A.
Toliński, T.
Gažo, E.
Powiązania:
https://bibliotekanauki.pl/articles/1810401.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.40.De
65.40.gd
71.20.Eh
71.70.-d
Opis:
The study of the heat capacity of the intermetallic compound $NdNi_{4}Si$ including the effect of the magnetic field is reported. This compound crystallizes in the hexagonal $CaCu_5$-type structure, space group P6/mmm. $NdNi_{4}Si$ is ferromagnetic with $T_C$ = 8 K and the saturation magnetic moment of 1.5 $μ_{B}$/f.u. at 4.2 K (in H = 9 T). The heat capacity was analyzed considering the electronic contribution, the Schottky anomaly, and the lattice contributions in the frames of the Debye model. The scheme of the energy levels created by the crystal electric field split is determined from the Schottky contribution to the specific heat. $NdNi_{4}Si$ was characterized by the electronic heat capacity coefficient γ = 85 mJ/(mol $K^2$) and the Debye temperature $Θp_D$ = 325 K.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 126-128
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetization Studies of Antiferromagnetic Interlayer Coupling in EuS-SrS Semiconductor Multilayers
Autorzy:
Samburskaya, T.
Sipatov, A.
Volobuev, V.
Dziawa, P.
Knoff, W.
Kowalczyk, L.
Szot, M.
Story, T.
Powiązania:
https://bibliotekanauki.pl/articles/1400494.pdf
Data publikacji:
2013-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Ck
75.30.Et
Opis:
Temperature and magnetic field dependence of magnetization of EuS-SrS multilayers grown epitaxially on KCl (001) substrate is experimentally studied by superconducting magnetometry technique. In these lattice-matched semiconductor heterostructures EuS layers are ferromagnetic quantum wells whereas SrS layers are nonmagnetic spacer barriers. The multilayers composed of EuS layers with thickness 3.5-5 nm and SrS layers (thickness 0.5-10 nm) exhibit ferromagnetic transition at 17 K. In the multilayers with ultrathin SrS spacers (0.5-1 nm) a nonmonotonic temperature dependence of magnetization as well as a characteristic switching in magnetic hysteresis loops is observed. These experimental findings are explained considering antiferromagnetic interlayer coupling between ferromagnetic EuS layers via nonmagnetic SrS spacers. The strength of this coupling is determined based on model magnetization calculations.
Źródło:
Acta Physica Polonica A; 2013, 124, 1; 133-136
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low Temperature Properties of the $Ce_{1-x}La_{x}NiAl_4$
Autorzy:
Toliński, T.
Kowalczyk, A.
Reiffers, M.
Šebek, J.
Šantavá, E.
Curlik, I.
Ilkovič, S.
Powiązania:
https://bibliotekanauki.pl/articles/1534742.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
65.40.Ba
75.30.Mb
Opis:
Measurements of the heat capacity in ultralow temperatures (down to 350 mK) have been carried out for $Ce_{1-x}La_{x}NiAl_4$. The paramagnetic behavior above about 30 K can be well described by the Curie-Weiss magnetic susceptibility. The undoped CeNiAl_4 compound is a known heavy fermion system with a large electronic specific heat coefficient (γ = 0.5 J $mol^{-1} K^{-2}$) and the Kondo temperature in the range 30-80 K. In the case of the $Ce_{0.8}La_{0.2}NiAl_4$ and $Ce_{0.6}La_{0.4}NiAl_4$ compounds a peak in C/T appears below 2 K, which is strongly damped by the magnetic field. It is probably connected with the Kondo and/or magnetic interactions and the electronic specific heat coefficient is 0.19 J $mol^{-1} K^{-2}$ (0.43 J $mol^{-1} K^{-2}$) for x = 0.2 (x = 0.4) at T → 0. The value determined above the peak, at temperature for which the magnetic field starts to decrease γ ( ≈ 3 K), is about 0.5 J $mol^{-1} K^{-2}$ and the effect of the magnetic field can be well analyzed in frames of the single-ion Kondo model.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 933-935
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy Change Calculations for Pure Gd and a Ni-Mn-Cu-Ga Heusler Alloy: Constant Field vs. Constant Temperature Experiment
Autorzy:
Ferenc, J.
Kowalczyk, M.
Wróblewski, R.
Cieślak, G.
Sielicki, K.
Leonowicz, M.
Kulik, T.
Powiązania:
https://bibliotekanauki.pl/articles/1402338.pdf
Data publikacji:
2015-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Sg
65.40.gd
Opis:
The magnetocaloric effect may be assessed indirectly by expressing it as the change in magnetic entropy in varying magnetic field, H, as the function of temperature, T. Magnetization, M=f(T,H), may be experimentally acquired from a series of isothermal measurements with variable field, or from a series of constant field measurements with variable temperature. The accuracy of magnetic entropy calculation depends on the number of series in these experiments. The aim of this work is to determine how little data is sufficient to obtain accurate results of magnetic entropy change calculations, on the basis of real, magnetocaloric materials. Pure gadolinium and a Ni-Mn-Cu-Ga Heusler alloy were studied. For both materials, the magnetic entropy change and relative cooling power were calculated from both experiments, with the decreasing number of experimental data. For both materials, the constant field experiment with only 6 field values provided only a 5% error of calculations, as compared to the experiment with 100 field values. The Arrott plots were also drawn for constant field mode with 6 field values, easily indicating the order of transition. Comparison of the calculation results suggests that the constant field mode magnetization measurement may be more accurate and faster than isothermal mode.
Źródło:
Acta Physica Polonica A; 2015, 128, 1; 111-115
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 31

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