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  1. 55 Acta Physica Polonica A

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  4. 8 2015

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  1. 10 Dubowik J.

  2. 7 Krawiecki A.

  3. 6 Gościańska I.

  4. 5 Dosoudil R.

  5. 5 Ušáková M.

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1
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Ferromagnetic Resonance in Very Fine Co Particles forming Granular Co-Cu Films

100%
Dubowik J., Kudryavtsev Y. V.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
249-252
EN
Ferromagnetic resonance was investigated in heterogeneous Co-Cu thin films consisting of randomly oriented fine Co particles embedded in Cu matrix. The experimental spectra are modelled using dynamic susceptibility approach assuming a broad distribution in particle sizes and dipolar interactions between particles.
2
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High-Quality Ni-Fe/Cu Multilayer Films with Antiferromagnetic Coupling

100%
Stobiecki F., Dubowik J., Luciński T., Szymański B., Rohrmann H., Röll K., Schmidt M.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
277-280
EN
We report structural and magnetic properties of Ni_{83}Fe_{17}/Cu multilayer films with various buffer layer and sublayer thicknesses of copper d_{Cu} and Permalloy d_{Py} deposited by face-to-face sputtering. The following features prove a good quality of our films: a well-layered structure, complete antiferromagnetic coupling with a low coupling strength (2×10^{-5} J/m^{2} for d_{Cu}=1 nm and 10^{-6} J/m^{^2} for d_{Cu}=2.1 nm) and a low coercive field which make them attractive for possible applications as giant magnetoresistance sensors.
3
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Probing the Phase Separation in the Doped Manganites by the Magnetic Resonance Methods

100%
Volkov N., Petrakovskii G., Sablina K., Patrin K.
Acta Physica Polonica A
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2004
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vol. 105
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issue 1-2
69-80
EN
Here we present magnetic resonance study which confirms an existence of a phase separation picture in Eu_{0.7}Pb_{0.3}MnO_3 single crystals. The measurements were performed with a standard technique and with using unconventional schemes of the magnetic resonance method. The inhomogeneous paramagnetic-ferromagnetic state, which is sensitive to a magnetic field, takes place in 0.65T_c-1.15T_c temperature range, where the colossal magnetoresistance effect is observed. The behavior of spectra suggests that a scenario of the phase separation is realized and the mixed state is not related to a simple chemical inhomogeneity. The changes of the conductivity induced by the microwave resonance absorption are observed in a vicinity of T_c, too. The changes are not related to a trivial heating of the sample by a microwave radiation. We propose a mechanism connected with the change of equilibrium concentrations of the coexisting phases, this change takes place when the system is under magnetic resonance conditions. To analyze the experimental data we applied the effective-medium approximation for two-component system. Also we attracted the simplest phenomenological model qualitatively reproducing the essential features of the behavior of the two-phase system.
4
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Quasi-Two-Dimensional Ferromagnetism in Cr₂Te₃ and Cr₅Te₈ Crystals

100%
Bester M., Stefaniuk I., Kuzma M.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
433-435
EN
The crystal structure of CrTe suggests two-dimensional magnetism in the plane perpendicular to the c axis. It is consistent with the temperature dependence of the g factor and EPR lines width observed. In the present paper we investigate the CrTe alloy which has been prepared by melting of the powdered Cr₂Te₃ in evacuated quartz ampoule at the temperature 1600 K. ESR spectra were recorded using X-band (9.4 GHz) spectrometer provided with gas nitrogen cryostat. The shape of the EPR line depends strongly on the temperature. In the vicinity of the room temperature the lines become very wide and weak or disappear completely. At lower temperatures the shape of the lines approaches the Dyson function. The asymmetry of lines is attributed to the strong exchange interactions as well as to the semimetal electrical conductivity. Above the room temperature the shape of spectra is characteristic for the paramagnetic phase. Results were addressed based on the model of critical spin fluctuations in two-dimensional Heisenberg magnet proposed by Eremin et al.
5
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Low Concentration Effect of Fe_3O_4 and Fe_3C Magnetic Nanoparticles in Non-Magnetic Matrix on the FMR Spectra

100%
Bodziony T., Guskos N., Roslaniec Z., Narkiewicz U., Kwiatkowska M., Maryniak M.
Acta Physica Polonica A
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2005
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vol. 108
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issue 2
297-302
EN
PTMO-block-PET polymer filled with a low concentration (0.1 wt.%) of binary magnetic system: magnetite (Fe_3O_4) and iron carbide (Fe_3C) with carbon (C) was prepared. Characterization of the sample was done by using X-ray diffraction and scanning electron microscopy methods. Temperature dependence of the FMR spectra was carried out in the 10-300 K temperature range. The extraordinary temperature dependence behaviour of FMR spectra was recorded. The FMR spectra were fitted by two Lorentzian lines originating from magnetite and iron carbide. The anomalous behaviour of FMR spectra below 100 K could be explained by the skin effect or by the freezing of the matrix benzene rings at about 115 K. The temperature dependence of the g parameter below 75.5 K (opposite shift of the resonance field to usually observed) was interpreted as a result of strong antiferromagnetic interaction of some portion of agglomerates.
6
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Surface Magnetic Anisotropy of Epitaxial La_{0.7}Mn_{1.3}O_{2.84} Thin Films

100%
Aleshkevych P., Baran M., Dyakonov V., Szymczak R., Szymczak H., Baberschke K., Lindner J., Lenz K.
Acta Physica Polonica A
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2006
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vol. 110
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issue 1
57-70
EN
A spin-wave resonance technique was used to collect information on elementary magnon excitations in high quality epitaxial La_{0.7}Mn_{1.3}O_{2.84} films prepared by dc-magnetron sputtering. It was found that besides bulk spin-wave modes, the spin-wave resonance spectrum includes also the surface spin waves. The value of spin-wave stiffness constant D=156 meV·Å^2 was found. The values of the surface magnetic anisotropy on both surfaces and their angular dependence were determined. The experimentally found spin-wave resonance spectra were explained based on the surface-inhomogeneity model. The effect of surface anisotropy on the spin-wave excitation conditions in epitaxial La_{0.7}Mn_{1.3}O_{2.84} films was investigated. Spin-wave resonance data give an indirect evidence of periodic charge-ordered stripes formation.
7
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FMR Evidence of Stable Ferromagnetic Correlations at Zigzag Edge States in Graphene

100%
Augustyniak-Jabłokow M., Maćkowiak M., Tadyszak K., Strzelczyk R.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
537-539
EN
We studied magnetic properties of a composite of paraffin and graphene flakes. Magnetic properties of this composite were investigated by ferromagnetic resonance/electron spin resonance technique. The ferromagnetic resonance signal from graphene suspension in paraffin is broad and shifted from magnetic field corresponding to g ≈ 2 to the low magnetic field. The temperature dependence of the spectra shows that magnetic ordering in the studied system is sensitive to thermal fluctuations. These features are expected for the 1D ferromagnetism and the obtained results are analyzed in the frame of the theoretical predictions concerning magnetic correlations at graphene edges. Therefore, based on our investigation we can conclude the existence of the magnetic edges in graphene and presence of the ferromagnetic correlations between edge spins.
8
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On the Interpretation of the Angular Dependence of the Main FMR/SWR Line in Ferromagnetic Thin Films

100%
Puszkarski H., Kasperski M.
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EN
The reported measurements of the angular dependence of ferromagnetic resonance spectra and their theoretical interpretation lead to the observation that a discrepancy occurs between the theory and the experiment in certain ranges of the configuration angle. This disagreement cannot be eliminated within the Smit-Beljers model commonly used in the literature for the description of ferromagnetic resonance in thin films since the main ferromagnetic resonance line observed in thin films is not necessarily associated with the excitation of a uniform mode, as the Smit-Beljers model does assume for bulk samples. Instead, we associate this line with the excitation of a surface mode or the thin-film principal nonuniform mode. By taking into account the occurrence of a surface spin-pinning anisotropy, this assumption allows to obtain an agreement between the theoretical description of the ferromagnetic resonance and the experimental data in the whole range of angular configuration of the external field. As an example, on the basis of this modified ferromagnetic resonance model, we make some observations on the angular resonant dependence in uniaxial thin films.
9
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Magnetic Properties of Semiconductor-Antiferromagnet Superlattices

80%
Wilamowski Z., Buczko R., Jantsch W., Ludwig M., Springholz G.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
973-976
EN
Magnetic resonance investigations of ultra-thin antiferromagnetic EuTe layers show a specific behaviour in the quasi-2D antiferromagnetic ordering: (i) an anisotropy of the critical broadening, (ii) a substantial increase in the Néel temperature and (iii) an anisotropic shift of the resonance frequency which diverges at the Néel point. The results show that exchange coupling is stronger in quasi-2D than in 3D antiferromagnetic samples and that correlation of spin chains aligned in the perpendicular direction occurs already well above the Néel point.
10
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Brillouin Light Scattering Investigations οf Magnetic and Elastic Properties in MBE Grown Trilayer Mo/Co/Au Systems

80%
Gieniusz R., Błachowicz T., Maziewski A., Petroutchik A., Baczewski L., Wawro A., Hamrle J., Serga O., Hillebrands B.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
213-216
EN
The magnetic and elastic properties of epitaxially grown Mo/Co/Au trilayer systems were investigated by the Brillouin light scattering and a ferromagnetic resonance. Using both experimental methods the perpendicular uniaxial anisotropy and the effective in-plane twofold anisotropy contributions were determined as the function of the cobalt thicknesses. Acoustic phonons analysis shows that the elastic constants are decreased with increasing cobalt layer thicknesses.
11
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Theory of Nonlinear Ferromagnetic Resonance in the Samples with Magnetostatic and Exchange Boundary Conditions Imposed

80%
Krawiecki A., Sukiennicki A.
Acta Physica Polonica A
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1993
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vol. 83
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issue 4
505-515
EN
General theory of nonlinear ferromagnetic resonance is presented for samples with the usual magnetostatic and exchange boundary conditions imposed at the sample surface. In such samples the Suhl instabilities and other nonlinear effects occur due to nonlinear interactions of magnetostatic or dipole-exchange modes. All relevant types of interactions are included in the Hamiltonian: with the pumping field, three- and four-mode ones. Analytic calculation of the Suhl thresholds in the three possible types of instabilities in perpendicular and parallel pumping is performed for the sample in the shape of a thin slab.
12
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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.
13
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Temperature Dependence of Magnetization Damping in Heusler Alloy Films

80%
Dubowik J., Załęski M., Głowiński H., Gościańska I.
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issue 5
848-850
EN
The Gilbert damping for Co_2CrAl (Co_2Cr_{0.3}Fe_{0.7}Al) and Ni_2MnSn Heusler alloy films was investigated as a function of temperature. The best films reveals the Gilbert damping nearly independent of temperature. Magnetic relaxation in Co_2CrAl is strongly influenced by magnetic inhomogeneities due to phase separation. The best Ni_2MnSn epitaxial films have comparable Gilbert damping α of 6× 10^{-3} as half-metallic Co_2Cr_{0.3}Fe_{0.7}Al films with α = 3 × 10^{-3}.
14
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Manipulation of Exchange Coupling in Py/Co/Cr Multilayer Thin Films

80%
Aköz M., Parlak U., Şahin Y., Tavşan D., Tarcan E., Öztürk O., Tokdemir Öztürk S., Erkovan M.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
992-994
EN
The main issue addressed in present study is exchange coupling modification between ferromagnetic layers through non-magnetic spacer layers using extra ultra-thin ferromagnetic layers (Co). In order to achieve this goal, we prepared Cr(50 Å) / Py(20 Å) / Co(5 Å) / Cr(7, 10, 13 Å) / Co(5 Å) / Py (30 Å) / Cr(50Å) / Si using magnetron sputtering at UHV conditions and characterized by Ferromagnetic Resonance (FMR) technique. As the present study results were compared to our previous study on (Py/Cr), the exchange coupling energy was increased ten times with the cobalt thin layer
15
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EMR Study of Electronic and Magnetic Ordering in Doped CaMn_{1-x,y}M_{x,y}O_3 (M = Ru, Mo) Perovskites

80%
Shames A., Auslender M., Rozenberg E., Gorodetsky G., Martin C., Maignan A.
Acta Physica Polonica A
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2005
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vol. 108
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issue 2
235-242
EN
X-band electron magnetic resonance measurements of polycrystalline CaMn_{1-x,y}M_{x,y}O_3 (M = Ru, 0≤x≤0.5; M = Mo, 0≤y≤0.14) samples were performed at 120 K≤ T≤540 K. The observed anomalies of electron magnetic resonance parameters correlate pretty well with the temperatures of antiferro-, ferromagnetic-like, and orbital/charge-ordering transitions in these systems and specify phase diagrams obtained by other techniques. However, a strong difference between resonant properties of Ru- and Mo-doped series is observed in both paramagnetic and magnetically ordered states. To describe such a difference, the energy bands diagrams, which comprise the deep impurity t_{2g}-like states + e_g-like conductive band for CaMn_{1-x}Ru_xO_3 and shallow impurity states + conductive band, both having e_g-like symmetry, for CaMn_{1-y}Mo_yO_3, are proposed. Specific electrons' contribution to the electron magnetic resonance line width explains concentration and temperature dependences of this parameter in the paramagnetic state in considered systems.
16
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Influence of the Grain Size on Polaron Transport in Nanostructured La_{2/3}Ca_{1/3}MnO_3 Evidenced by EPR

80%
Raita O., Grecu M., Filip X., Toloman D., Giurgiu L., Idziak S., Hoffmann S.
Acta Physica Polonica A
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2005
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vol. 108
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issue 1
113-118
EN
We report an electron paramagnetic resonance investigation of the grain size effects on the polaron transport in the paramagnetic regime of nanosized La_{2/3} Ca_{1/3}MnO_3 manganites. The temperature dependences of the EPR integral intensity were analyzed in terms of spin-spin exchange interaction and small polaron hopping scenarios. The polaron activation energy decreases with the reduction of the grain size. A discussion is given concerning the factors which could explain the observed change.
17
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Asymmetric Magnetization Reversal in the Exchange-Biased MnO/(Ga,Mn)As Heterostructure Studied by Ferromagnetic Resonance

80%
Dziatkowski K., Ge Z., Liu X., Furdyna J., Twardowski A.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
319-324
EN
We report ferromagnetic resonance study of the magnetization reversal in the exchange-coupled MnO/(Ga,Mn)As system. The low-field parts of ferromagnetic resonance spectra measured along [1/10] and [100] directions of (Ga,Mn)As were combined into hysteresis loops, which under field-cooling conditions similarly to SQUID loops are shifted toward negative magnetic fields. The magnetization reversal process revealed by the loops occurred remarkably asymmetric for both sample configurations.
18
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On-Off Intermittency in Randomly Driven Parallel Pumping

80%
Krawiecki A.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
465-468
EN
A model of parallel pumping with many interacting parametric spin-wave pairs is investigated numerically. On-off intermittency is obtained in the time series of absorption when the rf field amplitude is varied randomly in time, slowly in comparison with the rf field frequency, and when its mean value exceeds slightly the parallel pumping instability threshold. If the interactions between parametrically and thermally excited spin waves are neglected, only one parametric spin-wave pair is strongly excited and exhibits intermittent behaviour. In the opposite case a packet of parametric spin waves with frequencies close to half the pumping frequency may be excited. This modifies quantitatively, but not qualitatively the intermittency characteristics in the presence of thermal noise.
19
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Ultrafast Coherent Control of Spin Precession Motion by Terahertz Magnetic Pulses

80%
Nakajima M., Yamaguchi K., Suemoto T.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2
343-346
EN
We demonstrated coherent control of spin precession motion due to the ferromagnetic resonance induced by magnetic field component of ultrashort terahertz pulses. The amplitude of the precession can be controlled by the pulse separation time of the double pulse excitation technique. We succeeded in observing the energy transfer between spin and photon systems, and the energy of the spin system is returned to the second terahertz pulses instantaneously when the precession amplitude is cancelled.
20
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Ferromagnetic Resonance in Metallic Thin Films and Thin-Film Tubes

80%
Dubowik J., Gościańska I.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
179-182
EN
A model describing ferromagnetic resonance in thin-film magnetic metallic tubes is proposed and compared with the experimental ferromagnetic resonance spectra of the thin-film Ni.
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