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Wyświetlanie 1-15 z 43
Tytuł:
Bulk and Epitaxial $Co_2MnSi$ Systems with Antisite Disorder: Ab Initio Calculations
Autorzy:
Carva, K.
Turek, I.
Powiązania:
https://bibliotekanauki.pl/articles/1813602.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.-b
72.10.Fk
Opis:
The intermetallic compound $Co_2MnSi$ is halfmetallic, but the structure of real samples is often affected by antisite disorder. The influence of disorder on transport properties is examined by ab initio calculations and is found to be more significant in thin $Co_2MnSi$ slabs sandwiched by metallic leads than in the bulk compound.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 183-186
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Electric Field οn the Optical Spin Polarization of Electrons in a Diluted Magnetic Semiconductor
Autorzy:
Gorley, P.
Mysliuk, O.
Dugaev, V.
Horley, P.
Barnaś, J.
Powiązania:
https://bibliotekanauki.pl/articles/1791345.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.Fe
72.25.Rb
72.25.-b
Opis:
In this paper we present the results of theoretical calculations for spin polarization η of band electrons in diluted magnetic semiconductor subjected to a polarized light wave and a carrier-warming electric field E. It was shown that the maximum value of $η_{max}$ can be reached at a certain $E_{max}$ corresponding to the peak of the carrier drift velocity v(E). For the higher doping impurity concentration, the values of $η_{max}$ become lower due to the equivalent decrease of electron temperature.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 909-910
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Torque in Double Planar Tunnel Junctions
Autorzy:
Wilczyński, M.
Świrkowicz, R.
Barnaś, J.
Powiązania:
https://bibliotekanauki.pl/articles/1810520.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Gk
72.25.-b
Opis:
Transport in a double planar tunnel junction with ferromagnetic electrodes is analyzed theoretically in the zero-temperature limit. The in-plane and out-of-plane components of the spin torque exerted on magnetic moment of the central layer are determined as a function of the angle θ between magnetic moments of one of the external electrodes and of the central layer. Two configurations of the magnetic moments of external electrodes are considered, i.e. parallel and antiparallel ones. It is found that both torque components depend strongly on the thickness of the central layer, especially in junctions with a relatively thin central layer, where enhancement of the torque or a change of its sign can be observed for specific layer thicknesses. In junctions with thick central layer and in the limit of small bias voltage applied to the junction, the in-plane torque is generally smaller in the parallel configuration than in the antiparallel one. The opposite relation is observed for the normal torque.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 269-271
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamical Aspects of Magnetic Switching in a Single Molecule-Based Spin Valve
Autorzy:
Płomińska, A.
Misiorny, M.
Weymann, I.
Powiązania:
https://bibliotekanauki.pl/articles/1030425.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.-b
75.50.Xx
Opis:
The dynamics of the current-induced magnetic switching process is theoretically studied in a spin-valve device containing a single magnetic molecule of spin S=1. The analysis is performed by using the real-time diagrammatic technique in the sequential electron tunneling regime. In particular, we show that the magnetic moment of a molecule can be reversed also in the presence of intrinsic spin relaxation processes. Moreover, we discuss how the process of magnetic switching depends on a transport bias voltage as well as on some key parameters of the device.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 555-557
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic and Magnetotransport Properties οf Magnetite/Co-Ferrite/Magnetite Trilayers
Autorzy:
Chen, Y.
Ziese, M.
Powiązania:
https://bibliotekanauki.pl/articles/1810529.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.-b
72.25.Mk
75.70.-i
Opis:
The magnetic and magnetotransport properties of $Fe_3O_4$/$CoFe_2O_4$/$Fe_3O_4$ trilayers were investigated. The magnetization measurements indicate significant Co diffusion into the bottom magnetite layer. At lower temperatures the magnetoresistance measurements show two clearly separated maxima due to contributions from magnetically hard and soft layers. A tunneling effect was not observed. Comparison of full and minor resistance hysteresis loops did not reveal any significant exchange coupling between the layers, presumably due to diffuse interfaces.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 284-286
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Polarized Transport through Quantum Dots: Coulomb Blockade and Kondo Effect
Autorzy:
Barnaś, J.
Świrkowicz, R.
Wilczyński, M.
Weymann, I.
Martinek, J.
Dugaev, V.
Powiązania:
https://bibliotekanauki.pl/articles/2036886.pdf
Data publikacji:
2003-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.-b
73.23.Hk
72.15.Qm
Opis:
Spin related effects in electronic transport through quantum dots, coupled via tunneling barriers to two metallic leads, are discussed from the point of view of fundamental physics and possible applications in spin electronics. The effects follow either from long spin relaxation time in the dots or from spin dependent tunneling through the barriers when the external leads are ferromagnetic. In the former case large nonequilibrium spin fluctuations in the dot can be induced by flowing current. These fluctuations modify transport characteristics, particularly the shape of the Coulomb steps. In the latter case electric current depends on magnetic configuration of the system, and tunnel magnetoresistance effect due to magnetization rotation can occur. Transport properties in the weak coupling regime are described perturbatively in the first (sequential) and second (cotunneling) orders. In the strong coupling regime, on the other hand, the equation of motion for nonequilibrium Green functions is used to calculate electric current at low temperatures, where the Kondo peak in conductance is formed in the zero bias regime. In symmetrical systems the Kondo peak is split in the parallel magnetic configuration, whereas no splitting occurs for the antiparallel alignment. Theoretical results are discussed in view of available experimental data.
Źródło:
Acta Physica Polonica A; 2003, 104, 2; 165-177
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tunneling Charge Transport in Graphene-Based Superconductor Junctions
Autorzy:
Wojciechowski, R.
Kowalewski, L.
Nogala, M.
Powiązania:
https://bibliotekanauki.pl/articles/1427098.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.45.+c
72.80.Vp
72.25.-b
Opis:
We study the spin polarized electron and hole tunneling transport through a graphene-based ferromagnet$(GF_1)$-insulator$(GI_1)$-superconductor$(G_{S})$-insulator$(GI_2)$-ferromagnet$(GF_2)$ junction. Proximity induced spin polarization and superconductivity in a graphene sheet are assumed to be created by superconducting and ferromagnetic electrodes placed on the top of the graphene. Using a four-dimensional version of the Dirac-Bogoliubov-de Gennes equation with appropriate boundary conditions we investigate the tunneling processes through the junctions. In particular, we present calculations of the amplitudes of normal and Andreev reflections as a function of the energy of the incident electron for a wide range of the model parameters, such as the strength and orientation of the exchange field, the barrier strength, and the distance between the two ferromagnetic layers. The tunneling transport processes in the graphene-based double junction GF/GI/$G_{S}$/GI/GF are compared with those in non-graphene-based junctions.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1092-1094
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Transport in Magnetic Quantum Point Contacts
Autorzy:
Pietsch, T.
Egle, S.
Espy, C.
Strigl, F.
Scheer, E.
Powiązania:
https://bibliotekanauki.pl/articles/1490057.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.23.-b
72.25.-b
73.63.-b
Opis:
In recent years, the fabrication of novel building blocks for quantum computation- and spintronics devices gained significant attention. The ultimate goal in terms of miniaturization is the creation of single-atom functional elements. Practically, quantum point contacts are frequently used as model systems to study the fundamental electronic transport properties of such mesoscopic systems. A quantum point contact is characterised by a narrow constriction coupling two larger electron reservoirs. In the absence of a magnetic field, the conductance of these quantum point contacts is quantised in multiples of $2 e^2//h$, the so-called conductance quantum $(G_0)$. However, in the presence of magnetic fields the increased spin-degeneracy often gives rise to a deviation from the idealized behaviour and therefore leads to a change in the characteristic conductance of the quantum point contact. Herein, we illustrate the complex magnetotransport characteristics in quantum point contacts and magnetic heterojunctions. The theoretical framework and experimental concepts are discussed briefly together with the experimental results as well as potential applications.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 401-409
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Studies of Quantum Interference in Electronic Transport through Carbon Nanotubes
Autorzy:
Babiaczyk, W. I.
Bułka, B. R.
Powiązania:
https://bibliotekanauki.pl/articles/2035583.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.-b
73.23.-b
73.63.Fg
Opis:
We performed studies of coherent electronic transport through a single walled carbon nanotube. In the calculations multiple scattering on the contacts and interference processes were taken into account. Conductance is a composition of contributions from different channels. We studied also spin-dependent transport in the system with ferromagnetic electrodes. The magnetoresistance is large and shows large oscillations, it can be even negative in some cases.
Źródło:
Acta Physica Polonica A; 2002, 102, 4-5; 597-602
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature Dependence of Spin Hall Effect in k-Cubed Rashba Model
Autorzy:
Krzyżewska, A.
Dyrdał, A.
Berakdar, J.
Powiązania:
https://bibliotekanauki.pl/articles/1030432.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.70.Tj
72.25.-b
72.25.Mk
73.40.-c
Opis:
Within the Matsubara Green function formalism and linear response theory we considered theoretically the temperature dependences of the spin Hall effect for a two-dimensional gas with an isotropic k-cubed form of the Rashba interaction. We utilize a standard model for treating spin-orbit phenomena in p-doped semiconductor heterostructures and also for an electron gas formed at perovskite oxides interfaces.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 558-560
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Magnetic Zigzag Edges in Graphene-like Nanoribbons on the Thermoelectric Power Factor
Autorzy:
Krompiewski, S.
Cuniberti, G.
Powiązania:
https://bibliotekanauki.pl/articles/1030504.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.63.Kv
72.25.-b
73.50.Lw
Opis:
This study shows that magnetic edge states of graphene-like nanoribbons enhance effectively the thermoelectric performance. This is due to the antiparallel alignment of magnetic moments on opposite zigzag edges and the confinement effect, which jointly lead to the appearance of a gap in the electronic energy spectrum. Consequently, the Seebeck coefficient as well as the thermoelectric power factor get strongly enhanced (with respect to other alignment cases) at room temperature and energies not far away from the charge neutrality point. Moreover the corresponding figure of merit (ZT) is also improved as a result of the reduced electronic thermal conductance.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 535-537
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Current-Induced Magnetic Dynamics in Asymmetric Ferromagnetic Single-Electron Devices
Autorzy:
Kowalik, M.
Powiązania:
https://bibliotekanauki.pl/articles/1810537.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.-b
73.23.Hk
85.75.-d
Opis:
The theoretical calculations of possible dynamics for a localized magnetic moment of the central electrode in ferromagnetic single-electron devices are presented. The spin-transfer torque from spin current absorbed by the central electrode is calculated. Thereafter, an in-plane component of spin torque is regarded during the integration of the Landau-Lifshitz-Gilbert equation and the time evolution of the localized magnetic moment of the central electrode is obtained. The necessary conditions for switching of the magnetic moment are discussed.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 290-292
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrical Control of Magnetic States
Autorzy:
Barnaś, J.
Powiązania:
https://bibliotekanauki.pl/articles/1536525.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.60.Ch
75.70.Cn
72.25.-b
Opis:
Charge and spin transport in artificial magnetic structures, like nanopillar spin valves, planar tunnel junctions, and mesoscopic double-barrier junctions (single-electron transistors) are briefly surveyed, with particular emphasis on magnetoresistance effects and current-induced magnetic switching and spin dynamics. The methods of spin current generation are also discussed, particularly the method based on spin Hall effect.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 199-203
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin-Dependent Transient Effects in Electron Transport in the Quantum Dot System
Autorzy:
Parafiniuk, P.
Taranko, R.
Powiązania:
https://bibliotekanauki.pl/articles/1791296.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.-b
73.63.Kv
85.75.-d
Opis:
We study the effects of the Coulomb interaction U between the electrons of opposite spins localized in the quantum dot on the time-dependent electron transport through the quantum dot coupled with two non-magnetic leads. We calculate the transient spin-dependent current generated by a pulsed bias voltage applied across the quantum dot system via the equation of motion method for appropriate correlation functions. The influence of the Coulomb interaction on the quantum coherent oscillations and beats of the current, spin current and current polarization ratio is studied. Our results indicate that the coherent beats in both the total and spin currents observed in the case of vanishing Coulomb interaction are strongly suppressed by non-zero Coulomb interaction. We also show that in the case of the pulsed bias almost fully polarized current occurs in some time windows for non-vanishing Coulomb interaction contrary to almost pure charge or spin current at vanishing U.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 844-846
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin-Dependent Transport through a Single-Wall Carbon Nanotube Quantum Dot with an S=1 Molecule
Autorzy:
Płomińska, A.
Weymann, I.
Powiązania:
https://bibliotekanauki.pl/articles/1386697.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.-b
75.50.Xx
85.75.-d
Opis:
Transport properties of an S=1 molecule attached to a single-wall carbon nanotube quantum dot, which is coupled to two external ferromagnetic leads, are analyzed in the sequential tunneling regime. The magnetizations of the leads are assumed to form either a parallel or an antiparallel magnetic configuration. The calculations are performed by using the real-time diagrammatic technique in the lowest order perturbation theory with respect to the tunnel coupling. It is shown that the presence of the molecule strongly affects the bias voltage dependence of the current and differential conductance in both magnetic configurations, as well as the resulting tunnel magnetoresistance. Negative (greatly enhanced) tunnel magnetoresistance is found in the case of antiferromagnetic (ferromagnetic) coupling between the nanotube and molecule.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 475-477
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 43

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