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1
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Influence of Hydrostatic Pressure on the Zero-Field Splitting in NiSnCl_6·6H_2O

100%
Krupska A., Krupski M.
Acta Physica Polonica A
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2003
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vol. 103
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issue 5
453-458
EN
The dependence of the crystal-field splitting parameter D in NiSnCl_6·6H_2O on hydrostatic pressure was determined by the electron paramagnetic resonance method, for the pressures up to 500 MPa. The derivative (∂D/∂p)_T as well as the temperatures and pressures at which the D-parameter reaches zero, were determined. The molecular mechanism responsible for the temperature and pressure changes of the D-parameter is similar to that one observed in the isomorphic NiSiF_6·6H_2O.
2
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Pressure Dependence of Elastic Constants in Zinc-Blende III-N and Their Influence on the Light Emission in Nitride Heterostructures

100%
Łepkowski S., Majewski J.
Acta Physica Polonica A
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2004
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vol. 105
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issue 6
559-566
EN
We studied the nonlinear elasticity effects for the case of III-N compounds. Particularly, we determined the pressure dependences of elastic constants, in zinc-blende InN, GaN, and AlN by performing ab initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory. We found significant and almost linear increase in C_{11}, C_{12} with pressure for considered nitrides compounds. Much weaker dependence on pressure was observed for C_{44}. We also discussed pressure dependences of two-dimensional Poisson's ratio and elastic anisotropy coefficient. Finally, we showed that the pressure dependence of elastic constants results in significant reduction of the pressure coefficient of the energy emission in cubic InGaN/GaN quantum wells and essentially improves the agreement between experimental and theoretical values.
3
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The Pressure Dependence of Transition Metal-Related Levels in GaAs

100%
Babiński A., Baj M., Hennel A.
Acta Physica Polonica A
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1991
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vol. 79
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issue 2-3
323-327
EN
The hydrostatic pressure coefficients of V^{3+/2+} acceptor level in bulk GaAs and of the 0.48 eV trap (related to Ni^{2+/1+} double acceptor level) in VPE GaAs were measured by means of the DLTS technique. The obtained values are 94 meV/GPa and 196 meV/GPa relative to the bottom of the conduction band. For Ni^{2+/1+} level the strong pressure dependence of the capture cross-section activation energy (60 meV/GPa) was also observed.
4
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Dielectric Study of Pressure Induced fcc-sc Phase Transition in Fullerene C_{60}

80%
Trybuła Z., Krupski M.
Acta Physica Polonica A
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2000
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vol. 98
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issue 4
389-392
EN
Phase transition in polycrystalline fullerene C_{60} from fcc phase to a simple cubic phase sc induced by hydrostatic pressure up to 0.5GPa was studied by dielectric method. Pressure coefficient dT_{c}/dp=144±8 K/GPa was determined. This value is consistent with pressure coefficients obtained with other experimental techniques.
5
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Nonlinear Elasticity in Wurtzite GaN/AlN Planar Superlattices and Quantum Dots

80%
Łepkowski S., Majewski J., Jurczak G.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
749-754
EN
The elastic stiffness tensors for wurtzite GaN and AlN show a significant hydrostatic pressure dependence, which is the evidence of nonlinear elasticity of these compounds. We have examined how pressure dependence of elastic constants for wurtzite nitrides influences elastic and piezoelectric properties of GaN/AlN planar superlattices and quantum dots. Particularly, we show that built-in hydrostatic pressure, present in both quantum wells of the GaN/AlN superlattices and GaN/AlN quantum dots, increases significantly by 0.3-0.7 GPa when nonlinear elasticity is used. Consequently, the compressive volumetric strain in quantum wells and quantum dots decreases in comparison to the case of the linear elastic theory. However, the z-component of the built-in electric field in the quantum wells and quantum dots increases considerably when nonlinear elasticity is taken into account. Both effects, i.e., a decrease in the compressive volumetric strain as well as an increase in the built-in electric field, decrease the band-to-band transition energies in the quantum wells and quantum dots.
6
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Density Functional Studies of Nonlinear Elastic Properties for Zinc-Blende Nitrides

80%
Łopuszyński M., Majewski J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
443-447
EN
In this paper we present a method of calculating third-order elastic constants C_{ijk} and its application to zinc-blende nitrides AlN, GaN, and InN. Our approach is based on accurate ab initio calculations of both energy and stress as a function of applied strain. Ab initio computations are performed within density functional theory framework. To assess the reliability of the presented method, we compare our theoretical findings for GaAs with experimental results for C_{ijk} available for this material.
7
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Absorption and Photoluminescence of ZnSe/Zn_{x}Cd_{1-x}Se Superlattices and Quantum Wells under Hydrostatic Pressure

80%
Griebl E., Kerner W., Haserer B., Reisinger T., Hahn B., Gebhardt W.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
1017-1021
EN
We present absorption measurements of a pseudomorphic Zn_{0.75}Cd_{0.25}Se/ZnSe superlattice and a Zn_{0.91}Cd_{0.09} Se/ZnSe single quantum well under high hydrostatic pressure applied by a diamond anvil cell. Excitonic transitions as 1s-heavy hole and 1s-light hole between the first bound states or minibands as well as transitions in the buffer material are visible. Transition energies are well understood by calculations of the band structure near Γ. The observed energy distance between photoluminescence and hh-absorption signal gives information on exciton localization. Whereas this distance is nearly pressure independent in the buffer, there is a significant increase at pressures P > 5 GPa for quantum structures.
8
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Phase Transformations in Binary Alloys under High Pressure

80%
Degtyareva V.
Acta Physica Polonica A
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2002
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vol. 101
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issue 5
675-688
EN
High-pressure studies of binary alloy systems display some specific features connected with composition referring as a variable parameter. In a two-component system under pressure there are observed transformations, which do not occur in a one-component system. In particular, there is a formation of a single phase from a mixture of two phases or a decomposition of a uniform phase into two phases of different compositions. Alloys of In and Sn with neighbouring elements give us examples of these kinds of transformations. Studies on binary alloys with application of pressure provide experimental evidences that the alloy composition or electron concentration is one of the main factor for structural phase stability following from Hume-Rothery rule.
9
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High-Pressure Diffraction Study of Ga_{1-x}Al_{x}As

80%
Paszkowicz W., Dynowska E., Żytkiewicz Z. R., Dobosz D., Otto J. W.
Acta Physica Polonica A
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1997
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vol. 91
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issue 5
993-996
EN
The Ga_{1-x}Al_{x}As sample of x=0.5 was prepared from a high quality single crystal grown by electroepitaxy on GaAs. The high-pressure diffraction experiments were performed using a diamond anvil cell and a germanium solid state detector. The zinc-blende phase is stable up to about 17.5 GPa on uploading. A high-pressure phase manifests itself at about 17 GPa, a complete phase change occurs at 18.7 GPa. On downloading, the zinc-blende phase reappears at about 10 GPa. The powder pattern of the high-pressure phase shows some similarities with the GaAs high pressure phases.
10
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Experimental Evidence for the Spatial Correlation of Charged EL2(+) Defects and Acceptors in Semi-insulating GaAs

80%
Sadowski M. L., Grynberg M.
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EN
The far-infrared photoconductivity due to shallow donors was measured in semi-insulating GaAs for different states of the EL2 defect - normal, metastable, and during the transition - with and without hydrostatic pres­sure. The results show that the intra-donor transition line broadening ob­served previously after transferring the EL2 to the metastable configuration cannot be due to lattice distortion effects, and can only be explained in terms of a spatial correlation of charged EL2(+) and acceptor A(-) states, which form electric dipoles.
11
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High Pressure - High Temperature Diffraction Study of MnTe Using Synchrotron Radiation

80%
Paszkowicz W., Dynowska E., Peun T.
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EN
High pressure - high temperature experiments for MnTe of NiAs type were performed using a synchrotron radiation as X-ray source and a cubic anvil X-ray diffraction press to produce nonambient sample environment. In the investigated range of pressure (0-67.5 kbar) on uploading and with following temperature rise from 296 to 1273 K (at 67.5 kbar), the structure type of MnTe is conserved. An earlier reported nonlinear behaviour of lattice-parameter c_{0} is not found in the present study. Possible reasons of this discrepancy are discussed. The value of bulk modulus and its pressure derivative were calculated from the pressure-volume dependence by fitting the Birch-Murnaghan equation.
12
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Analytical Model for Explosive-Driven Ultracompact Shock-Wave Ferromagnetic Generators

80%
Talantsev E., Shkuratov S., Baird J., Altgilbers L.
Acta Physica Polonica A
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2009
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vol. 115
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issue 6
1028-1030
EN
An analytical model of the operation of recently invented ultracompact explosive-driven shock-wave ferromagnetic generators that utilize longitudinal (shock wave propagates along the magnetization vector) and transverse (shock wave propagates across the magnetization vector) shock wave demagnetization of Nd_{2}Fe_{14}B hard ferromagnets, and an analytical technique for calculation of amplitudes of the current pulse produced by the generators were developed. The model utilizes the magnitude of the energy product, (BH)_{max}, and the magnetostatic energy of the hard ferromagnetic element of the ferromagnetic generator as parameters for determining ferromagnetic generator pulse generation, and it does not consider the magnitude of remnant magnetization, B_{r}, of the ferromagnetic material. The developed technique for calculation of the current pulse amplitude produced by the ferromagnetic generator provides comprehensive and accurate results. Amplitudes of calculated ferromagnetic generator output currents are in good agreement with experimentally obtained data.
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