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Tytuł:
Ultrafast Magnetization Dynamics in Epitaxial Ni-Mn-Sn Heusler Alloy Film
Autorzy:
Bonda, A.
Uba, S.
Załęski, K.
Dubowik, J.
Uba, L.
Powiązania:
https://bibliotekanauki.pl/articles/1030478.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.78.Jp
75.50.-y
78.47.J-
75.30.-m
06.60.Jn
75.40.Gb
Opis:
The work is devoted to studies of ultrafast magnetization dynamics induced by femtosecond laser pulses in ferromagnetic Ni-Mn-Sn shape memory Heusler alloy. We studied epitaxial thin Ni_{54.3}Mn_{31.9}Sn_{13.8} film deposited on (001) MgO substrate. Spin precession in an external magnetic field was triggered and detected by the time-resolved magneto-optical Kerr effect (TRMOKE) using pump-probe technique in dual color scheme experiment. Measurements were performed as a function of magnetic field H and pulse power P. The measured TRMOKE signal is composed of oscillatory and background components, both decaying exponentially in a nanosecond time scale. The precession frequency was determined and found to be varying in the range of 1-10 GHz with H up to 3 kOe and decreasing linearly with P. The dependence of Gilbert damping parameter α on H was determined and discussed.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 501-504
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructure characterization of Nafion® HP JP as a proton exchange membrane for fuel cell: Positron annihilation study
Autorzy:
Mohamed, Hamdy
Abdel-Hady, E.
Abdel-Hamed, M.
Said, M.
Powiązania:
https://bibliotekanauki.pl/articles/1057926.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
82.47.Nj
72.80.Le
36.10.Dr
88.30.J-
88.30.pf
Opis:
Free volume size V_{f} and proton conductivity σ of a novel polymer electrolyte membrane were investigated as a function of temperature and relative humidity up to 140°C and 80%, respectively. The free volume size V_{f} for Nafion® HP JP reflect the α-transition temperature at about 98°C. In addition the free volume size V_{f} for Nafion® HP JP is smaller than that for Nafion® NRE212 membrane which leads to lower methanol permeability of the former membrane. The proton conductivity σ for Nafion® HP JP decreases with increase of temperature up to transition temperature due to free and bound water loss, then it starts to increase due to dynamic segmental motion. It increases for Nafion® HP JP with the increase of the relative humidity. A good correlation between V_{f} and σ was successfully established for both membranes which indicates that σ is governed by the free volume. In conclusion, Nafion® HP JP is a suitable membrane for a proton exchange membrane fuel cell application.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1543-1547
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Magnetite Nanopowders Prepared by Co-Precipitation Method
Autorzy:
Durak, K.
Wiertel, M.
Surowiec, Z.
Miaskowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1033944.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Wx
47.65.Cb
78.70.Bj
61.72.J-
61.72.Mm
68.37.Hk
Opis:
Nanosized iron oxide powders are materials considered with regard to its application in medical therapy called hyperthermia. Magnetite nanopowders with crystallite size varying from 6.6 to 11.8 nm have been prepared by the co-precipitation method. In this study a change of a crystallite size is driven mainly by varying of initial pH of water ammonia solution in which a process of magnetite precipitation runs. Crystallographic structures and phase composition obtained samples and the size of magnetite nanoparticles were determined by X-ray diffraction method. Positron lifetime spectroscopy has been used to assess defectiveness of microstructure. Experimental positron annihilation spectra were successfully resolved into three lifetime components. It appears that from point of view of microstructure the defects concentrations in studied nanopowder samples are very high which causes a saturation of positron trapping.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1593-1597
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Proton conductivity and free volume properties in per-fluorinated sulfonic acid/PTFE copolymer for fuel cell
Autorzy:
Mohamed, H.
Abdel-Hady, E.
Abdel-Hamed, M.
Powiązania:
https://bibliotekanauki.pl/articles/1057956.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
82.47.Nj
72.80.Le
36.10.Dr
88.30.J-
88.30.pf
Opis:
The proton conductivity mechanism in per-fluorinated sulfonic acid/PTFE copolymer Fumapem® membranes for polymer electrolyte membranes has been investigated. Three samples of Fumapem® F-950, F-1050 and F-14100 membranes with different ion exchange capacity 1.05, 0.95, and 0.71 meq/g, respectively, were used in this study after drying. The o-Ps hole volume size (V_{FV,Ps}) was quantified using the positron annihilation lifetime technique while the proton conductivities (σ ) were measured using LCR Bridge as function of temperature. It was found that as the ion exchange capacity increases, the proton conductivity increases and the free volume expands. Temperature dependences of proton conductivity and the o-Ps hole volume size (V_{FV,Ps}) reflect the glass transition temperature of the membrane. A good linear correlation between the reciprocal of the o-Ps hole volume size (1/V_{FV,Ps}) and log(σ)+Δ E_a/2.303k_{B}T, (where ΔE_a is the activation energy, T is the absolute temperature and k_{B} is the Boltzmann constant) at different temperatures indicate that the ionic motion in dry Fumapem® is governed by the free volume. A linear relationship between the critical hole size γ V*_{i} and the ion exchange capacity was also achieved.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1509-1514
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Role of Oxygen Coordination on the Ultrafast Demagnetization in Ferrite Nanoparticles
Autorzy:
Terrier, E.
Liu, Y.
Begin, S.
Pichon, B.
Bigot, J.
Halte, V.
Powiązania:
https://bibliotekanauki.pl/articles/1385573.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.47.J-
78.20.Ls
75.30.Et
75.75.Fk
Opis:
In this work, we have studied the ultrafast dynamics of charges and spins in assemblies of magnetite (Fe₃O₄) and maghemite (γ - Fe₂O₃) nanoparticles. We demonstrate that using time-resolved magneto-optics one is able to disentangle those very similar iron oxide structures. The Fe₃O₄ nanoparticles are elaborated by hydrothermal decomposition and deposited by drop on a glass substrate. γ - Fe₂O₃ nanoparticles assemblies have been obtained by annealing the Fe₃O₄ nanoparticles. Comparing time resolved transmission and Faraday rotation, our measurements show that in case of Fe₃O₄ the demagnetization occurs after the thermalization of the charges, as expected from previous works on ultrafast quenching of magnetization in ferromagnetic nanostructures. On the contrary, in the case of maghemite nanoparticles, an acceleration of the demagnetizing occurs, leading to a simultaneous charges and spins dynamics. We attribute this behavior to the rearrangement of vacancies and annealing of crystal defects in maghemite.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 345-346
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Carrier Dynamics and Dynamic Band-Bending in Type-II ZnTe/ZnSe Quantum Dots
Autorzy:
Syperek, M.
Misiewicz, J.
Chan, C.
Dumcenco, D.
Huang, Y.
Chou, W.
Powiązania:
https://bibliotekanauki.pl/articles/1399095.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
78.55.Et
78.47.J-
Opis:
Carrier dynamics and dynamic band-bending in self-assembled ZnTe/ZnSe quantum dots have been studied by means of time-resolved photoluminescence experiment at low temperatures. The experiment reveals clearly type-II character of the confinement potential in the dot manifested in: (i) long photoluminescence decay time constant of 28-35 ns, and (ii) temporal shift of the quantum dot peak emission towards low energy following the laser pulse excitation. The magnitude of the spectral shift Δ E depends on the dot size and the power density of excitation pulse. For the dots under study and given experimental conditions Δ E ≈ 28 ÷ 42 meV.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 821-823
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bond-Selective Excitation and Following Displacement of Ge Atoms in $GeTe//Sb_{2}Te_{3}$ Superlattice
Autorzy:
Makino, K.
Tominaga, J.
Kolobov, A.
Fons, P.
Hase, M.
Powiązania:
https://bibliotekanauki.pl/articles/1489973.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.47.J-
63.22.Np
63.20.kd
63.20.kk
Opis:
Phase change random access memory devices made from chalcogenides compounds, such as $Ge_{2}Sb_{2}Te_{5}$, have attracted much attention because of their high-speed read-write and low power consumption capabilities. The phase change in $Ge_{2}Sb_{2}Te_{5}$ is thought to be characterized by the displacement of Ge atoms, accompanying relaxation of surrounding Sb and Te atoms. Here we examine a new approach, that is the manipulation of Ge-Te bonds using linearly-polarized femtosecond near-infrared optical pulses. As a result, p-polarized pump pulses are found to be more effective in inducing the precursor of phase change, probably due to the atomic arrangements along the unique axis of the superlattice structure.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 336-339
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Femtosecond Reflection Spectroscopy in $La_{1.5}Sr_{0.5}CoO_4$
Autorzy:
Egawa, T.
Okimoto, Y.
Fukaya, R.
Onda, K.
Ishikawa, T.
Koshihara, S.
Isayama, A.
Sasagawa, T.
Powiązania:
https://bibliotekanauki.pl/articles/1489953.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.47.J-
78.47.jg
Opis:
Ultrafast optical response has been investigated using fs laser system on a perovskite-type cobalt oxide, $La_{1.5}Sr_{0.5}CoO_4$. After the photoirradiation at room temperature, the time profile of relative change of reflectance (Δ R/R) shows a sudden change within the pulse duration ( ≈ 150 fs) and decays with a lifetime of ≈ 330 fs. The sign of Δ R/R after the photoexcitation is positive in the mid-infrared region (at 0.50 eV) while negative in the visible energy region (at 2.0 eV), implying photoinduced change of the electronic structure after the photoexcitation.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 307-309
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Novel Excitation-Density Dependence in Strongly Spin-Charge Coupled System
Autorzy:
Ohara, J.
Kanamori, Y.
Ishihara, S.
Powiązania:
https://bibliotekanauki.pl/articles/1490003.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.10.-w
78.47.J-
78.20.Bh
Opis:
Photoinduced spin-charge dynamics in strongly correlated electron systems is studied based on an extended double-exchange model. Solving a time-dependent Schrödinger equation with the Lanczos method, we trace the process of photoinduced melting of an antiferromagnetic charge order and analyze the excitation-density dependence on that. In the case of low density photoexcitation, both charge and spin orders are melted by photocarrier doping. This is interpreted with a conventional double-exchange mechanism. In the case of high density photoexcitation, however, the charge order is melted. The antiferromagnetic spin order is transiently weakened but after turnoff of the photoirradiation it recovers. This phenomenon strikingly differs from the weak photoexcitation case.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 355-358
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Search for the Photo-Induced Hidden Phase in Inorganic and Organic Systems
Autorzy:
Koshihara, S.
Onda, K.
Okimoto, Y.
Ishikawa, T.
Powiązania:
https://bibliotekanauki.pl/articles/1489970.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.47.J-
63.20.kd
71.30.+h
71.45.Lr
Opis:
We review the dynamical behavior of strongly electron-lattice (orbital) coupled system induced by photo-excitation of fs laser pulse. By virtue of the femtosecond (fs) spectroscopy and picosecond (ps) time-resolved X-ray diffraction measurements, we demonstrate that the photo-irradiation creates new ordered state so called as "hidden phase" which can never be realized under thermo-equilibrium condition. This exotic phase commonly plays the key role for realizing the gigantic photo-induced changes in optical properties of inorganic and organic electron-lattice strongly coupled systems.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 328-331
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Time-Resolved Pump-Probe Diffraction Experiment at SOLEIL Synchrotron: Photoinduced Spin Transition in the Molecular Crystal [TPA Fe(III) TCC] $PF_6$
Autorzy:
Laulhé, C.
Ravy, S.
Fertey, P.
Elkaim, E.
Legrand, F.
Féret, P.
Hollander, Ph.
Hustache, S.
Bordessoule, M.
Ricaud, J.
Collet, E.
Lorenc, M.
Buron-Le Cointe, M.
Cailleau, H.
Tissot, A.
Boillot, M.
Powiązania:
https://bibliotekanauki.pl/articles/1489972.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.50.Ks
61.05.cp
31.70.Ks
78.47.J-
Opis:
We present the first time-resolved pump-probe experiment performed at synchrotron SOLEIL at the CRISTAL diffraction beamline. The time-resolved setup will be used in the near future for sub-ns time resolution experiments. We studied spin state switching in a [TPA Fe(III) TCC] $PF_6$ single crystal as induced by a ≈6 ns laser pulse (1064 nm), by measuring the 3D diffraction volume of the 002 Bragg reflection as a function of time after excitation. The intensity profiles (rocking curves) are found to evolve at two characteristic timescales, namely hundreds of ns and few μs, exhibiting subtle profile changes and peak broadenings. Consistently with previous studies, we interpret these features as due to structural inhomogeneities related to laser-induced deformation wave propagation and heat diffusion, which both start from the absorbing sites.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 332-335
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrafast Magneto-Optical and Magnetization-Induced Second Harmonic Generation Techniques for Studies of Magnetic Nanostructures
Autorzy:
Bonda, A.
Uba, S.
Uba, L.
Powiązania:
https://bibliotekanauki.pl/articles/1428579.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
06.60.Jn
78.47.J-
42.65.Re
75.50.-y
Opis:
The work concerns application of titanium-sapphire femtosecond laser oscillator with 82 MHz repetition rate at 800 nm in measurements of ultrafast magneto-optical and magnetization-induced second harmonic generation effects. Time-resolved magneto-optical Kerr effect pump-probe method was used in investigation of ultrafast precession of magnetization in Fe/Au multilayers. Magnetization precession frequency, obtained as a function of magnetic field applied, allows determining saturation magnetization and damping factor. The magnetization-induced second harmonic generation effect has been used for study of garnet films. This method allows to determine crystallographic symmetry and hysteresis loops in an external magnetic field at 2 ω laser induced frequency. The simultaneous measurements of linear and second order magneto-optical effects enable to investigate magnetic interfaces in the studied structures.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1225-1227
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of Ultrafast Photodetectors Based on $N^+GaAs$ and LT GaAs
Autorzy:
Białous, M.
Mogilinski, R.
Wierzbicki, M.
Świtkowski, K.
Pura, B.
Powiązania:
https://bibliotekanauki.pl/articles/1505355.pdf
Data publikacji:
2011-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.-e
78.47.J-
78.70.Ck
Opis:
We present investigation of a photodetector based on nitrogen-ion-implanted GaAs. Device photoresponse signal shows 1.15 ps FWHM (400 GHz, 3 dB bandwidth) with the voltage amplitude ≈ 1 mV, measured using a constructed electro-optic sampling setup with 80 fs width, 795 nm wavelength and laser pulses repetition rate of 80 MHz. Changes in the shape of electrical signal for different beam powers excitation and voltage biases have been demonstrated, compared with LT GaAs photodetector based on the same finger geometry. Using technique of X-ray diffraction and diffuse scattering analyses we have observed the decrease of lattice constant, radius of nanoclusters after implantation, respectively, and linear density dislocations increased over twice.
Źródło:
Acta Physica Polonica A; 2011, 119, 3; 382-386
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic Roughening and Material Optical Properties Influence on Van der Waals/Casimir Forces
Autorzy:
van Zwol, P.
Palasantzas, G.
Powiązania:
https://bibliotekanauki.pl/articles/1539079.pdf
Data publikacji:
2010-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.55.Jk
68.37.Ps
85.85.+j
78.68.+m
68.55.-a
47.55.nb
Opis:
Atomic force microscopy measurements and force theory calculations using the Lifshitz theory show that van der Waals/Casimir dispersive forces have a strong dependence on surface roughness and material optical properties. It is found that at separations below 100 nm the roughness effect is manifested through a strong deviation from the normal scaling of the force with separation distance. Moreover, knowledge of precise optical properties of metals is shown to be very important for accurate force predictions rather than referring to idealized defect free material models. Finally, we compare the van der Waals/Casimir forces to capillary adhesive forces in order to illustrate their significance in stiction problems.
Źródło:
Acta Physica Polonica A; 2010, 117, 2; 379-383
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Light-Induced Precession of Magnetization in Ferromagnetic Semiconductor (Ga,Mn)As
Autorzy:
Tesařová, N.
Němec, P.
Rozkotová, E.
Trojánek, F.
Malý, P.
Powiązania:
https://bibliotekanauki.pl/articles/1535535.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.78.-n
78.47.J-
78.47.D-
Opis:
Precession of magnetization induced by laser pulses in (Ga,Mn)As was studied by the pump-and-probe technique. We concentrated on various experimental aspects that can be used to identify a part of the measured magneto-optical signals that provides information about the dynamics of magnetization. We also revealed that that it takes about 80 ps before the quasi-equilibrium precession of magnetization is initiated by the impact of laser pulse.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 1065-1066
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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