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1
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Influence of Epitaxial Strain on Magnetic Anisotropy in (Ga,Mn)As

100%
Juszyński P., Wasik D., Gryglas-Borysiewicz M., Przybytek J., Szczytko J., Twardowski A., Sadowski J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1004-1006
EN
Two (Ga,Mn)As samples having different magnetic anisotropy (one with in-plane easy axis and another one with out-of-plane easy axis) were studied by means of magnetotransport experiments. Anisotropy field B_{A} was determined for both samples as a function of temperature. For the sample having in-plane easy axis, an inversion of the direction of planar Hall effect hysteresis was observed upon increase of temperature. This result was simulated using the Stoner-Wohlfarth model.
2
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Approximation of Electrical and Magneto Transport Properties of LSMO Thin Films

80%
Štrbík V., Reiffers M., Chromik Š., Španková M.
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vol. 126
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issue 1
210-211
EN
We have used a three term polynomial expression to approximate electrical and magneto transport properties of epitaxial La_{0.67}Sr_{0.33}MnO_{3} (LSMO) thin films in wide temperature range (2-350 K) and in magnetic field up to 9 T. The first term is determined by a low temperature (T<20 K) residual resistivity ρ_{0} and this term is magnetic field independent. The second term describes the electron-electron scattering in LSMO, it shows ~ T^{2} dependence of resistivity up to temperature about 160 K and depends only weakly on magnetic field. The third term, proportional to ~ T^{4.5} dependence, describes a significant increase of resistivity in temperature range 160-350 K and due to its sensitivity to applied magnetic field it is possible to approximate temperature dependence of magnetorestivity below 350 K.
3
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Hydrodynamic Memory in the Motion of Charged Brownian Particles across the Magnetic Field

80%
Tóthová J., Lisý V.
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issue 5
1051-1053
EN
An exact solution of the Langevin equation is given for a charged Brownian particle driven in an incompressible fluid by the magnetic field, taking into account the hydrodynamic aftereffect. The stochastic integro-differential Langevin equation is converted to a deterministic equation for the particle mean square displacement. We have found the mean square displacement and other time correlation functions describing the particle motion. For the motion along the field the known results from the theory of the hydrodynamic motion of a free Brownian particle are recovered. The correlation functions across the field contain at long times the familiar Einstein terms and additional algebraic tails. The longest-lived tail in the mean square displacement is proportional to t^{1/2}. At short times the motion is ballistic and independent of the magnetic field.
4
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Effect of Magnetic Field on the Fluctuations of Charged Oscillators in Viscoelastic Fluids

80%
Lisý V., Tóthová J.
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vol. 126
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issue 1
413-414
EN
In the present work the generalized Langevin equation is solved for the motion of a charged Brownian oscillator in a magnetic field, when the thermal random force is exponentially correlated in the time. This model is consistent with the assumption that the medium has weakly viscoelastic properties. The velocity autocorrelation function, time-dependent diffusion coefficient and mean square displacement of the particle have been calculated. Our solutions generalize the previous results from the literature and are obtained in a way applicable to other problems of the Brownian motion with memory.
5
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Tunnel Magnetoresistance in Carbon Nanotube Quantum Dot

80%
Krychowski D., Lipiński S.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
545-548
EN
The out-of-equilibrium transport properties of carbon nanotube quantum dot in the Kondo regime are studied by means of the non-equilibrium Green function. The equation of motion method is used. The influence of the polarization of electrodes and orbital level splitting, as well as left-right asymmetry, on the spin polarizations of differential conductance are discussed. For zero bias voltage and orbitally degenerate states the SU(4) symmetry of Kondo state is preserved for antiparallel configuration of polarizations of electrodes, whereas it is broken for parallel. In the former case a suppression of linear conductance with increasing polarization is observed. In the latter the behaviour is nonmonotonic due to splitting of the Kondo peak and bringing closer one of the peaks to the Fermi level with increasing polarization. This gives rise to giant tunnel linear magnetoresistance for large polarization.
6
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Thermodynamic and Magnetotransport Properties of High Quality Na_{0.77}CoO_{2} Single Crystals

80%
Baran A., Zorkovská A., Kajňaková M., Lin C., Feher A.
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vol. 126
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issue 1
360-361
EN
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.
7
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Ageing Phenomena in La-Sr Manganites with Divalent Substituents for Manganese

80%
Merkulov D., Badelin A., Estemirova S., Karpasyuk V.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
529-531
EN
Variations of electromagnetic and structural characteristics of La_{1-c+x}Sr_{c-x}Mn_{1-x}Me_{x}O_{3+γ} manganites (Me = Zn, Ni) during storage time up to 36000 hours at room temperature and after frequentative thermal cycling in the 300-573 K range were investigated. Changes of magnetization of all samples were within the error of measurement. In most cases Curie point (T_{C}) showed irregular variations within the range of 20%, while zinc-substituted manganites with relatively high values of "c" exhibited some trend of T_{C} rise. The resistance of all samples increased during storage period. The cell volume of single-phase manganites decreased over time, that may indicates an increase in oxygen content. However, the sample with the highest Ni content (x=0.125) at c=0.19 suffered phase transition "rhombohedral-orthorhombic structures", which cannot be explained by the oxygen absorption. Probably, this effect was due to the rearrangement of the ions and vacancies between crystal sublattices of manganite.
8
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Effect of Granule Shape on the Giant Magnetoresistance for Ferromagnetic Metal-Metal Granular Films

80%
Wang C., Zhang P., Zhang Y., Rong Y.
Acta Physica Polonica A
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2007
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vol. 112
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issue 6
1231-1238
EN
In order to investigate the effect of granule shape on the giant magnetoresistance, assuming that granular films consist of ellipsoidal ferromagnetic granules embedded in a nonmagnetic metal matrix and the ellipsoidal granules have different demagnetizing factors in three directions, we combined two-current model with the effective medium theory to investigate the effect of granule shape on the giant magnetoresistance. The results revealed that the giant magnetoresistance in granular films depended strongly on the granule shape and was between those for current perpendicular to the plane of the layers and current in the plane of the layers in magnetic multilayers.
9
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Magnetotransport Properties of CaTi_xRu_{1-x}O_3 (x=0, 0.07)

80%
Zorkovská A., Baran A., Feher A., Šebek J., Šantavá E., Bradarić I.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
351-354
EN
Electrical resistance, transversal magnetoresistance and the Hall effect were studied on polycrystalline CaTi_xRu_{1-x}O_3 (x=0, 0.07) samples using a conventional Quantum Design PPMS-9 equipment in the temperature range 2-300 K and magnetic field up to 9 T. Substantial differences were found between the two samples: (i) opposite to the metallic character of CaRuO_3, the substituted sample has insulating-like electrical resistance;(ii) the magnetoresistance of the substituted sample changes the sign from negative to positive values with increasing temperature. The magnetoresistance of CaRuO_3 is negative, the sign reversal is induced by magnetic field and only at temperatures below 15 K, such a behaviour is predicted for clustered systems;(iii) the Hall voltage in pure CaRuO_3 also changes sign from negative to positive values above 35 K. This temperature coincides with the observed magnetic transition temperature, indicating that the magnetic state and the carrier character interrelate.
10
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Content available

Fabrication and Magnetotransport Properties of Carbon Films with Embedded Metal Nanoclusters

80%
Ksenevich V., Bashmakov I., Melnikov A., Wieck A.
Acta Physica Polonica A
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2005
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vol. 107
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issue 2
356-360
EN
2-dimensional arrays of Co- and Pd-clusters embedded in carbon films were fabricated by means of heat-treatment method of carboxylated cellulose films after the exchange of COOH-group protons by Co- and Pd-cations. The sizes of metal clusters within range 10 nm-1μm were obtained in dependence on the heat-treatment temperature. The dependencies of the resistance on temperature and magnetic field for the samples annealed at T=700ºC and 900ºC were measured. The R(T) dependencies both for carbon films with Co- and Pd-clusters can be fitted by expression R=R_0 exp(T_0/T)^{1/n} inherent for variable-range hopping. In the whole range of investigated magnetic field and temperature magnetoresistance was negative and can be related to quantum interference in the variable range hopping transport along neighboring alternative paths.
11
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Inverse Spin Hall Effect by Spin-Pumping in Co_2Cr_{0.4}Fe_{0.6}Al/Pt Structures

80%
Gościańska I., Dubowik J.
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issue 5
851-853
EN
Inverse spin Hall effect consists in conversion of spin currents into electric currents and has recently been observed using spin-pumping operated by ferromagnetic resonance in permalloy/Pt(Cr) thin film structures. We prepared several Co_2Cr_{0.4}Fe_{0.6}Al/Pt thin film structures to observe for the first time inverse spin Hall effect in bilayer structures comprising ferromagnetic half-metallic Heusler alloy. In but a few Co_2Cr_{0.4}Fe_{0.6}Al/Pt samples we succeeded in observing inverse spin Hall effect voltage of few microvolts by spin pumping resulting from ferromagnetic resonance. This confirms that spin polarized current can be transferred into Pt layer. Inverse spin Hall effect was 2-3 times larger than that detected in permalloy/Pt bilayer under the same conditions.
12
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Single Domain Wall Contribution to the Impedance of Amorphous Ferromagnetic Wire

70%
Ziman J., Šuhajová V., Kladivová M.
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vol. 126
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issue 1
82-83
EN
An experiment, measuring the changes of impedance in a magnetic wire, caused by the presence of a single domain wall was proposed. The results obtained from a magnetic wire with small helical anisotropy show that for lower frequencies (up to about 1 MHz), the presence of wall causes an increase in impedance, very probably due to the wall displacement. As frequency increases, the influence of the wall presence on the magnetic state causes the impedance to decrease in adjacent domains. For frequencies close to 10 MHz this effect overcomes the effect of wall displacement.
13
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Model of Anisotropic Electrical Resistivity in Rough Thin Films

70%
Szumiata T., Gzik-Szumiata M.
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issue 5
859-860
EN
In this work a new model of electrical resistivity is proposed in order to study the relationship between surface roughness geometry and thin films resistivity. The model is based on the numerical dynamic averaging of electron mean free path over whole simulated structure of rough film. For current-in-plane configuration the resistivity increases with decreasing film thickness faster than for current-perpendicular-to-plane one. Our simulations showed that big roughness depth and fine in-plane spatial period of roughness are crucial factors increasing the resistivity of ultrathin metallic layers.
14
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Mechanisms of Substituting Quadrivalent Ions Influence on the Properties of La-Sr Manganites

70%
Merkulov D., Badelin A., Estemirova S., Karpasyuk V.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
248-250
EN
Regularities of the influence of quadrivalent ions and oxygen concentrations on the structural characteristics, saturation magnetization, Curie point, temperature dependence of electrical conductance of ceramic manganites La_{1-c-x}Sr_{c+x}Mn_{1-x}Me^{4+x}O_{3+γ} (Me = Ti, Ge; 0.17 ≤ c ≤ 0.35; 0.025 ≤ x ≤ 0.125) were established. The relation between experimental data on lattice parameters, electromagnetic properties and crystal chemistry characteristics (nonstoichiometry index, concentrations of ions residing at different charge states) was determined using the modified model of effective cation-anion distances. The data obtained provide some evidence that in Ti-containing manganites when Sr concentration is more than 0.375, single-charged oxygen ions can arise after reductive annealing.
15
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Angular Magnetoresistance of a Possible Kondo Insulator CeOs₄Sb₁₂ Measured at Ultra-Low Temperatures

61%
Bochenek Ł., Cichorek T.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
600-603
EN
Angular magnetoresistance of the filled skutterudite compound CeOs₄Sb₁₂ has been investigated along the [110] direction. Distinct differences between the angular magnetoresistance data at T = 0.55 K and 4.2 K coincide with a developing of spin-density waves at T ≈ 1.7 K in B = 5 T. Magnetoresistance experiments have been performed on a self-made assembly utilizing a commercial piezoelectric rotator.
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