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1
Content available remote

On Biquadratic Interlayer Coupling in Magnetic Multilayers

100%
Barnaś J.
Acta Physica Polonica A
|
1994
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vol. 85
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issue 2
461-464
EN
Intrinsic biquadratic interlayer coupling in magnetic layered structures is analysed theoretically within the spin-polarized free-electron approximation. The corresponding coupling parameter oscillates with the interlayer thickness with the oscillation period equal to half of that for bilinear term. An extrinsic mechanism following from a competition between the intra- and interlayer exchange coupling is also discussed.
2
Content available remote

Transport in Magnetic Layered Structures: Giant Magnetoresistance

100%
Barnaś J.
Acta Physica Polonica A
|
1994
|
vol. 85
|
issue 1
165-177
EN
Basic features of electronic transport in magnetic layered structures consisting of alternating ferromagnetic and nonmagnetic metallic films are analysed theoretically. The considerations are restricted to magnetoresistance originating from the rotation of the film magnetizations from antiparallel to parallel alignment. The influence of spin-dependent potentials on the transport properties is analysed for both current-in-plane and current-perpendicular-to-plane geometries. Quasi-classical and quantum methods are used to calculate the appropriate conductivity. For current-perpendicular-to-plane geometry the periodic spin-dependent effective electron potential plays an important role and can generate giant magnetoresistance also when the electron scattering by impurities and interface roughness is independent of the spin direction, contrary to the case of current-in-plane geometry when a spin-dependent scattering probability is a necessary condition for the giant magnetoresistance to occur.
3
Content available remote

Electrical Control of Magnetic States

100%
Barnaś J.
Acta Physica Polonica A
|
2010
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vol. 118
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issue 2
199-203
EN
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.
4
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Dependence of Bilinear and Biquadratic Interlayer coupling on Thickness of Magnetic Films

100%
Barnaś J.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
257-260
EN
The dependence of bilinear and biquadratic interlayer coupling on the thickness of magnetic films is analysed for a trilayer structure with specular reflection at the outer surfaces. It is shown that the oscillation periods corresponding to the case where the thickness of one of the two magnetic films is constant, while that of the second one is varied, can be different from the oscillation periods in the case where the thicknesses of both magnetic films vary simultaneously. The nonoscillatory component of the coupling parameter is shown to be weakly dependent on the thickness of the magnetic films.
5
Content available remote

Thermoelectric Effects in Spin Valves Based on Layered Magnetic Structures

64%
Kunert H., Barnaś J.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
124-128
EN
General aspects of thermoelectric effects in spin valves consisting of two magnetic layers separated by a nonmagnetic spacing layer are considered, with the main focus on the spin Seebeck effects. The Seebeck and spin Seebeck effects are considered in both current-in-plane and current-perpendicular-to-plane geometries. The corresponding thermopower and spin thermopower in the macroscopic limit of electronic transport are also considered. Physical origin of the spin effects is discussed in detail.
6
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Transmission Through Graphene Junctions with Rashba Spin-Orbit Coupling

64%
Rataj M., Barnaś J.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
481-483
EN
Electronic transport in a graphene junction is considered theoretically. Graphene is assumed to be deposited on a substrate which generates Rashba spin-orbit coupling. However, the Rashba parameters in the two parts of the junction are assumed to be generally different. Additionally, different gate voltages are applied to the two parts, which allow tuning the Fermi level and potential step. We analyze the probabilities of electron transmission through the junction and electrical conductance in the linear response regime.
7
Content available remote

Quantum Transport in Thin-Film Structures

64%
Bułka B., Barnaś J.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
465-468
EN
General quantum-mechanical description of electronic transport in thin-film structures, which is based on the Kubo approach, is presented and applied to a single film with ideal surfaces. The cases of a constant chemical potential and a constant particle number are considered and analysed numerically.
8
Content available remote

Tunneling Magnetoresistance in Planar Ferromagnetic Junctions

64%
Wilczyński M., Barnaś J.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
443-446
EN
Bias dependence of the tunnel magnetoresistance in simple planar ferromagnetic junctions is considered theoretically within the one-band model. The limit of sequential tunnelling in double junctions with a non-magnetic central electrode is studied as well. In this case tunnel magnetoresistance exists only when the spin relaxation time due to spin-flip scattering processes inside the central electrode is sufficiently long.
9
Content available remote

Coherent Transport through Systems of Coupled Quantum Dots

64%
Trocha P., Barnaś J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
473-480
EN
Spin-dependent electronic transport through two coupled single-level quantum dots attached to ferromagnetic leads with parallel and antiparallel magnetizations is analyzed theoretically. The intra-dot Coulomb correlation is taken into account, while the inter-dot Coulomb repulsion is omitted. Conductance and tunnel magnetoresistance associated with magnetization rotation are calculated by the nonequilibrium Green function technique. The relevant Green functions are derived by the equation of motion method in the Hartree-Fock approximation. The dot occupation numbers and the Green functions are calculated self-consistently. The interference effects in electronic transport through quantum dots are analyzed in two different configurations. It is shown that the Fano resonance in conductance can be observed even for vanishing inter-dot hopping parameter t. The interplay of the interference effects and the Coulomb interactions in quantum dots is also analyzed.
10
Content available remote

Effects of Spin Pumping on Spin Waves in Antiferromagnetically Exchange-Coupled Double Layers with Surface Anisotropy

64%
Baláž P., Barnaś J.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2
150-152
EN
Spin wave modes in antiferromagnetically exchange-coupled magnetic double layers are analyzed theoretically. The considered structure is assumed to be covered by a nonmagnetic metallic layer. The spin wave frequencies and spin wave life times are determined from the macroscopic description based on the Landau-Lifshitz-Gilbert equation, which includes the torque due to spin pumping to the cap layer.
11
Content available remote

Spin Hall Effect in a Two-Dimensional Electron Gas with Constant Dresselhaus and Random Rashba Spin-Orbit Interactions

64%
Dyrdał A., Barnaś J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1016-1018
EN
Spin Hall effect in a two-dimensional electron gas with uniform Dresselhaus and random Rashba spin-orbit interactions is considered theoretically. Using Kubo formalism we derive some analytical formula for the spin Hall conductivity. It is shown that the contribution due to randomly fluctuating Rashba field disappears in the limit of strong Dresselhaus coupling.
12
Content available remote

Intrinsic Spin Hall and Spin Nernst Effects in Single-Layer Graphene: Tight-Binding vs. Effective Model

64%
Dyrdał A., Barnaś J.
Acta Physica Polonica A
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2012
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vol. 121
|
issue 5-6
1198-1200
EN
We calculate topological contributions to the spin Hall and spin Nernst effects due to intrinsic spin-orbit interaction in a single-layer graphene. To describe electronic spectrum of the graphene we have assumed the k·p model as well as the full tight-binding Hamiltonian. The corresponding contributions to the spin Hall and spin Nernst effects have been determined using the linear response theory and Green function formalism.
13
Content available remote

Spin and Charge Transport in a Magnetic Tunnel Junction with Magnetic Impurities Embedded in the Tunnel Barrier

64%
Misiorny M., Barnaś J.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2
196-199
EN
Electronic transport in a nanoscopic magnetic tunnel junction with magnetic particles or magnetic impurity atoms/molecules embedded in the barrier is studied theoretically. The impurity Hamiltonian includes magnetic anisotropy of easy axis type with additional perpendicular term. The description takes into account both elastic tunneling processes as well as inelastic processes associated with a flip of electron spin.
14
Content available remote

Oscillations in Magnetoresistance and Interlayer coupling in Magnetic Sandwich Structures

64%
Barnaś J., Bułka B.
Acta Physica Polonica A
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1997
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vol. 91
|
issue 2
253-256
EN
Kubo formalism is used to calculate the magnetoresistance due to magnetization rotation in a structure consisting of two magnetic films separated by a nonmagnetic layer. In the approximation of a uniform relaxation time for each layer, the oscillatory term in magnetoresistance corresponds to the oscillation period which depends on the potential barriers at the interfaces. This period is longer than the oscillation period observed in the coupling parameter.
15
Content available remote

Quasiclassical Theory of Spin-Valve Magnetoresistance: Role of Spin-Flip Scattering

64%
Baksalary O. M., Barnaś J.
Acta Physica Polonica A
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1997
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vol. 91
|
issue 2
261-264
EN
The Boltzmann kinetic equation is used to analyse the in-plane electronic transport in magnetic multilayers. Both diffuse and electron-momentum-conserving spin-flip scattering processes are included. Numerical results show that the momentum-conserving scattering processes reduce the spin-valve magnetoresistance.
16
Content available remote

Thermoelectric Properties of Doped Zigzag Silicene Nanoribbons

52%
Zberecki K., Swirkowicz R., Barnaś J.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 2
505-507
EN
Thermoelectric properties of silicene nanoribbons doped with magnetic impurity atoms are investigated theoretically for both antiparallel and parallel orientations of the edge magnetic moments. Spin density distribution and transport parameters have been determined by ab-initio numerical methods based on the density functional theory. Doping with magnetic atoms considerably modifies the spin density distribution, leading to a ground state with a non-zero magnetic moment. Apart from this, the spin thermopower can be considerably enhanced by the impurity atoms.
17
Content available remote

Phonon-Assisted Kondo Resonance in Spin-Dependent Transport through a Quantum Dot

52%
Świrkowicz R., Wilczyński M., Barnaś J.
Acta Physica Polonica A
|
2009
|
vol. 115
|
issue 1
272-274
EN
Effects of local vibrational modes on electron transport through a quantum dot attached to ferromagnetic electrodes are studied in the Kondo regime by the non-equilibrium Green function formalism based on the equation of motion method. Differential conductance is calculated for parallel and antiparallel configurations of the leads' magnetic moments, and well defined Kondo resonance peaks and their phonon satellites are found. The influence of a compensating magnetic field on the peak positions is also discussed.
18
Content available remote

Spin Torque in Double Planar Tunnel Junctions

52%
Wilczyński M., Świrkowicz R., Barnaś J.
Acta Physica Polonica A
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2009
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vol. 115
|
issue 1
269-271
EN
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.
19
Content available remote

Transport through Single-Wall Carbon Nanotubes Weakly Coupled to External Leads

52%
Weymann I., Krompiewski S., Barnaś J.
Acta Physica Polonica A
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2009
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vol. 115
|
issue 1
296-298
EN
We consider transport properties of single-wall metallic carbon nanotubes weakly coupled to external leads. In particular, we analyze the conductance and shot noise of nanotubes coupled to nonmagnetic leads and show that the shot noise may become super-Poissonian depending on the ground state of the nanotube. In addition, we also show that when the nanotube is coupled to one ferromagnetic and one nonmagnetic lead, it can operate as a gate-controlled spin diode.
20
Content available remote

Current-Pulse-Induced Switching οf Asymmetric Spin Valves

52%
Baláž P., Gmitra M., Barnaś J.
Acta Physica Polonica A
|
2009
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vol. 115
|
issue 1
278-280
EN
Dynamical behavior of an asymmetric spin valve, Co/Cu/Py nanopillar sandwiched between Cu electrodes, subject to a spin-polarized current was investigated in the diffusive transport regime. Using numerical macrospin simulations, the dynamical diagrams of the sensing layer were constructed, and the possibilities of switching from one collinear state to the other were discussed. A simple switching scheme for asymmetric spin valves, based on a sequence of current and magnetic field pulses, was proposed and illustrated on an example.
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