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1
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Surface True and Leaky Waves in Subsonic and Supersonic Regions. Explicit Solution of a Simple Model

100%
Trzupek D., Zieliński P.
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issue 4
570-573
EN
A simple model of a surface of a 2D continuum is shown to exhibit subsonic and supersonic surface resonances (leaky waves, pseudosurface waves), i.e. finite-lived excitations, along with usual surface waves (true subsonic surface waves). The physical meaning, controversial in the existing literature, of the surface leaky waves in both regions is discussed by a thought experiment in which a stimulus adjusted to the resonance parameters is applied to the surface. The infinite displacement-stimulus ratio in the long-time limit then is shown to be in power in all the cases of surface states and a finite amplitude of the leaky waves is demonstrated despite an apparent divergence suggested by their algebraic form.
2
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Hardening of (Pb,Cd)Te Crystal Lattice with an Increasing CdTe Content in the Solid Solution

100%
Kuna R., Adamiak S., Petit S., Baroni P., Gas K., Minikayev R., Szczerbakow A., Łażewski J., Szuszkiewicz W.
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EN
Single crystals of the (Pb,Cd)Te solid solution with CdTe content up to 9% were grown by self-selecting vapour growth method and investigated by powder X-ray diffraction, inelastic neutron scattering, and nanoindentation measurements. The analysis of the linear part of the LA phonon dispersion, determined by the inelastic neutron scattering demonstrated an increase of the sound velocity (thus the hardening of the crystal lattice) with an increase of CdTe content in the solid solution. An important increase of microhardness value for (Pb,Cd)Te was directly confirmed by results of nanoindentation measurements performed for a few samples with various chemical composition.
3
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Stress Induced Phononic Properties and Surface Waves in 2D Model of Auxetic Crystal

80%
Trzupek D., Twaróg D., Zieliński P.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
576-578
EN
Elastic stiffness parameters are determined in a 2D model system of rigid rods interacting by harmonic force constants. Any positive ("normal" crystal) or negative (auxetic crystal) Poisson ratio can be obtained in this model as a function of the external stress. Conditions for opening an absolute stop band (phononic crystal) and for various kinds of surface waves are obtained.
4
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Surface Dynamics and Phononic Properties of 2D Field Tunable Auxetic Crystal

80%
Twaróg D., Trzupek D., Zieliński P.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
579-582
EN
The lattice in-plane dynamics is studied as a function of external field in a model of auxetic crystal consisting of rigid polar rods and of elastic springs. The phase speed of the transverse acoustic wave propagating parallel to the polar rods is shown to be higher than the speed of the longitudinal wave at strong fields. An absolute stop band for the lattice waves opens in the whole Brillouin zone with increasing field. The surface waves and resonances at a surface parallel to the rods are studied. Infinitely narrow resonances called exceptional surface waves are found within bulk bands at certain specific values of the parameters characterizing the surface. Generally, the surface layer should be significantly heavier and stiffer than the substrate for the phenomenon to occur.
5
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Synthesis and Characterization of Mn-Doped BiFeO_3 Nanoparticles

80%
Fukumura H., Matsui S., Tonari N., Nakamura T., Hasuike N., Nishio K., Isshiki T., Harima H., Kisoda K.
Acta Physica Polonica A
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2009
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vol. 116
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issue 1
47-50
EN
BiFeO_3 is a multiferroic material showing antiferromagnetic ordering and ferroelectric behavior simultaneously. Here, Mn-doped BiFeO_3 nanoparticles were synthesized up to 10% of Mn composition by a sol-gel process. The samples showed high crystallinity with no secondary phase up to 2% of Mn doping. A phonon peak at 1250 cm^{-1} in undoped BiFeO_3 showed anomalous intensity enhancement in the magnetically ordered phase below T_N = 643 K due to a spin-phonon coupling. This behavior was less pronounced in the Mn-doped samples, suggesting a suppression of magnetic ordering between Fe^{3+} spins by Mn doping.
6
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Optical Characterization of Graphene and Highly Oriented Pyrolytic Graphite

80%
Kostić R., Mirić M., Radić T., Radović M., Gajić R., Popović Z.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
718-721
EN
We present a symmetry analysis of allowed infrared and Raman modes in graphene and highly oriented pyrolytic graphite. Surface structure for highly oriented pyrolytic graphite is examined using atomic force microscopy. As experimental tools, we used infrared spectroscopic ellipsometry in order to investigate the pseudodielectric function of highly oriented pyrolytic graphite in the mid-infrared range (500-7000 cm^{-1}) and Raman spectroscopy to investigate the influence of layers number decrease. As a result, we propose a method for an experimental verification of graphene.
7
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Micro-Raman Study of BiFeO_3 Thin Films Fabricated by Chemical Solution Deposition Using Different Bi/Fe Ratio Precursors

80%
Nakamura T., Fukumura H., Hasuike N., Harima H., Nakamura Y., Kisoda K., Nakashima S., Okuyama M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 1
72-74
EN
BiFeO_3 thin films were grown by chemical solution deposition using precursors with different elemental ratios, Bi/Fe = 1.1/1.0, 1.0/1.0 and 1.0/1.1. All the samples consisted of two easily distinguishable components of crystalline and amorphous phases. We have found that the electric properties of BiFeO_3 thin films are closely connected to the crystallinity of the films.
8
Content available remote

Inelastic X-Ray Scattering Studies of Phonon Dispersion in PbTe and (Pb,Cd)Te Solid Solution

80%
Kuna R., Minikayev R., Trzyna M., Gas K., Bosak A., Szczerbakow A., Petit S., Łażewski J., Szuszkiewicz W.
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EN
PbTe and its solid solution (Pb,Cd)Te containing 2% of CdTe and PbTe grown by self-selecting vapour growth technique were investigated by inelastic X-ray scattering using synchrotron radiation. The ID28 beamline at ESRF with the incident photon energy of 17794 eV and the energy resolution of 3 meV was applied for that purpose. The measurements were performed at room temperature along [001]-type high symmetry direction in the Brillouin zone. In spite of a very low energy of phonon branches they can be determined by inelastic X-ray scattering with a high accuracy. The transversal acoustic phonon dispersion obtained by inelastic X-ray scattering corresponds well to those resulting from inelastic neutron scattering measurements and ab initio calculations. Apart from expected structures corresponding to the bulk phonons an additional scattering related to the crystal surface properties was observed in the inelastic X-ray scattering spectra. The analysis performed with the use of secondary ion mass spectroscopy technique demonstrated a presence of a thin oxide layer at sample surfaces.
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