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1
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Exciton Binding Energy in Extremely Shallow Quantum Wells

100%
Kossut J., Furdyna J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
528-532
EN
The usual approach to the problem of excitons in semiconductor quan­tum wells is to assume that both the electron or the hole are primarily localized in the potential well regions defined by the band offsets, i.e., that the quantum wells are deep. We re-examine the problem of the exciton in the presence of a very shallow square well potential due to the (small) conduc­tion and valence band offsets in a semiconducting heterostructure. We show that the combined effects of the shallow well and the Coulomb interaction between the electron and the hole are equivalent to an effective potential acting on the center-of-mass of a three-dimensional exciton. We calculate the shape of such a potential and show it to be satisfactorily approximated by the potential of a parabolic well.
2
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Feature Article - Semiconductor Superlattices with Small Band Offsets

81%
Yang G., Lewandowski L., Furdyna J., Ram-Mohan L.
Acta Physica Polonica A
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1998
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vol. 93
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issue 4
567-600
EN
Optical transitions in small band offset superlattices are studied within the framework of the nearly free electron approximation, in which the weak superlattice potential is treated as a perturbation. Interband selection rules are derived for transitions involving conduction and valence band states at the superlattice Brillouin zone center and the zone edge. It is found that a number of new transitions can occur in such small-offset superlattices due to wave function mixing of different subband states. The effect of the effective mass on the optical transitions is also discussed. The theory is used to explain the results observed in magneto-optical absorption experiment in ZnSe/Zn_{1-x}Mn_{x}Se small-offset superlattices. Furthermore, the nearly free electron formulation is found to be in excellent agreement with rigorous multi-band numerical calculation on superlattices involving small band offsets.
3
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Application of Photomemory Effect in Cd_{1-x}Mn_{x}Te_{1-y}Se_{y}:In for Direct Measurements of Magnetization of Bound Magnetic Polarons

81%
Wojtowicz T., Koleśnik S., Miotkowski I., Furdyna J.
Acta Physica Polonica A
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1992
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vol. 82
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issue 4
637-640
EN
The first direct measurement of the magnetization of donor bound magnetic polarons in diluted magnetic semiconductors is reported. The experiment has been performed taking advantage of photomemory effect found in n-type Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} crystals doped with In. Good agreement between experimental results and theory of bound magnetic polarons is observed.
4
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Magnetic Phase Diagram of Zinc-Blende Cd_{1-x}Mn_{x}Se

81%
Sawicki M., Furdyna J., Luo H.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
923-926
EN
The paper reports first magnetic measurements performed on MBE grown epilayers of zinc-blende Cd_{1-x}Mn_{x}Se. For all samples studied in the concentration range 0.24 < x < 0.63 we find at low temperatures a history-dependent magnetic response, suggesting a transition to a spin-glass-like state. The central result of the paper is the presentation of a new, complete magnetic phase diagram for this material.
5
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Static and Dynamic Spin Organization in Magnetic Semiconductor Nanostructures

71%
Samarth N., Luo H., Furdyna J., Giebultowicz T., Awschalom D.
Acta Physica Polonica A
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1992
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vol. 82
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issue 4
573-584
EN
We describe experiments which study static and dynamic aspects of Mn spin organization in magnetic semiconductor superlattices and quantum wells. Neutron diffraction studies of ZnSe/MnSe and ZnTe/MnSe superlattices show how static Mn spin organization in these antiferromagnetic layers may be modified by strain and lowered dimensionality. We also use a novel form of femtosecond magnetic spectroscopy to examine magnetic polaron dynamics in diluted magnetic semiconductor quantum wells, and show how the organization of Mn spins by a spin-polarized carrier population may be directly viewed in the time domain.
6
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Asymmetric Magnetization Reversal in the Exchange-Biased MnO/(Ga,Mn)As Heterostructure Studied by Ferromagnetic Resonance

71%
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.
7
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Ferromagnetic Resonance Study of Exchange Coupled (Ga,Mn)As/GaAs/(Ga,Mn)As Heterostructures

62%
Dziatkowski K., Ge Z., Liu X., Furdyna J., Clerjaud B., Twardowski A.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
227-232
EN
Ferromagnetic resonance study of the exchange coupled (Ga,Mn)As/ GaAs/(Ga,Mn)As heterostructures is reported. The measurements were performed on the series of samples with varying thicknesses d_{GaAs} of nonmagnetic GaAs spacer, established d_{GaAs}-dependent extent of weak and strong interlayer exchange coupling, judging on the observation of one or two ferromagnetic resonance modes.
8
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Exchange Coupling in Magnetic Semiconductor Multilayers and Superlattices

62%
Furdyna J., Leiner J., Liu X., Dobrowolska M., Lee S., Chung J., Kirby B.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
973-980
EN
The study of ferromagnetic semiconductors continues to be of great interest because of their potential for spintronic devices. While there has been much progress in our understanding of ferromagnetic semiconductor materials - particularly of the canonical III-V system Ga_{1-x}Mn_xAs - many issues still remain unresolved. One of these is the nature of interlayer exchange coupling in GaMnAs-based multilayers, an issue that is important from the point of view of possible spintronic applications. In this connection, it is important to establish under what conditions the interlayer exchange coupling between successive GaMnAs layers is antiferromagnetic or ferromagnetic, since manipulation of such interlayer exchange coupling can then be directly applied to achieve giant magnetoresistance and other devices based on this material. In this review we will describe magneto-transport, magnetization, and neutron reflectometry experiments applied to two types of GaMnAs-based multilayer structures - superlattices and tri-layers - consisting of GaMnAs layers separated by non-magnetic GaAs spacers. These measurements serve to identify conditions under which AFM coupling will occur in such GaMnAs/GaAs multilayer systems, thus providing us the information which can be used for manipulating magnetization (and thus also giant magnetoresistance) in structures based on the ferromagnetic semiconductor GaMnAs.
9
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Far-Infrared Magneto-Optical Studies of HgTe-CdTe Superlattices in the Semimetallic Regime

62%
Wojtowicz T., Dobrowolska M., Furdyna J., Meyer J., Bartoli F., Hoffman C., Ram-Mohan L.
Acta Physica Polonica A
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1991
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vol. 80
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issue 2
245-254
EN
We review recent magneto-optical investigations performed on HgTe-CdTe semimetallic superlattices. Far infrared magnetotransmission data obtained as a function of temperature, photon energy, and sense of circular polarization are compared with the predictions of a comprehensive new theory which fully incorporates the complexities of type-III superlattice band structure. It is found that the theory accounts for nearly all of the many unusual features which have been observed experimentally. These include the occurrence of two cyclotron resonances due to holes; the coexistence of electron and hole cyclotron resonances in the low temperature limit; the observation of three distinct CRA minima; a step-like change in the temperature dependence of the electron cyclotron mass; and a dramatic increase of the CRI absorption peak intensity with increasing magnetic field.
10
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Influence of Growth Break before Capping on Photoluminescence Dynamics of CdSe/ZnSe Self-Assembled Quantum Dots

62%
Nowak S., Suffczyński J., Goryca M., Kossacki P., Gaj J., Lee S., Furdyna J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1267-1271
EN
Influence of growth breaks before capping of CdSe self-assembled quantum dot layers on photoluminescence dynamics was examined in three samples. Short (5s) break resulted only in a small blue shift, caused probably by partial strain relaxation and/or Zn interdiffusion. Long (20 min) break induced a strong broadening and red shift of the spectra, combined with a dramatic slow down of the photoluminescence decays. The main result of the long break was identified as introduction of defects (impurities), which generate local electric fields and act as traps of photogenerated carriers.
11
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Persistent Spin Resonance of Donor Electrons and Hopping Magnetoconductivity in Cd_{1-x}Mn_{x}Te_{1-y}Se_{y}

62%
Wojtowicz T., Semaltianos N., Kłosowski P., Dobrowolska M., Furdyna J., Miotkowski I.
Acta Physica Polonica A
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1991
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vol. 80
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issue 2
287-290
EN
The first observation of electric dipole spin resonance of donor electrons in Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} in far-infrared magnetotransmission is reported. Modification of the donor wave function due to non-diagonal exchange interaction with localized magnetic moments and to magnetic fluctuations are believed to allow this resonance. Hopping magnetoconductivity studied in the same crystals shows a behavior typical for wide gap diluted magnetic semiconductors.
12
Content available remote

Photoluminescence of Donor-Doped ZnSe Films Grown by Molecular Beam Epitaxy

62%
Karczewski G., Hu B., Yin A., Luo H., Dobrowolska M., Furdyna J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
245-248
EN
We studied the effect of the donor doping of ZnSe films on their photoluminescence properties. The samples were doped during the molecular beam epitaxy growth, either with gallium or with chlorine. As the dopant concen­tration dose increases, the intensity of the band-edge emission first saturates, and then quenches in favor of the deep-level photoluminescence band. The main effect of donor doping on photoluminescence is a strong increase in intensity of the donor-bound exciton line, referred to as I_{2}. For Ga-doped films deep-band emission is much stronger, and the I_{2}-line is slightly weaker than for Cl-doped films with comparable doping level. The results confirm the superiority of chlorine over gallium as an n-type dopant in ZnSe. We dis­cuss the photoluminescence results and relate them to deep level transient spectroscopy data obtained on the same samples.
13
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Magnons in Cubic MBE-Grown A_{1-x}Mn_{x}Te Layers (A = Cd, Zn, Mg)

52%
Szuszkiewicz W., Hennion B., Jouanne M., Morhange J., Dynowska E., Janik E., Wojtowicz T., Zieliński M., Furdyna J.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
583-587
EN
One-magnon excitations in MBE-grown A_{1-x}Mn_{x}Te layers (where A = Cd, Zn, Mg and x>0.7) were investigated by means of the Raman scattering measurements at low temperatures (≈20 K). The composition dependence of the anisotropy energy - as extracted from these measurements - is discussed. Further, the elastic neutron scattering measurements were performed in layers of cubic MnTe, which constitute the end point material of the ternary alloys series. Abundance of variously oriented antiferromagnetic domains in MnTe layers as a function of temperature was studied. We confirm occurrence of a pronounced magnetostriction effect.
14
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Transport and Magnetic Properties of Low Temperature Annealed Ga_{1-x}Mn_xAs

52%
Kuryliszyn I., Wojtowicz T., Liu X., Furdyna J., Dobrowolski W., Broto J., Goiran M., Portugall O., Rakoto H., Raquet B.
|
|
issue 4-5
659-665
EN
We present the results of low temperature annealing studies of Ga_{1-x}Mn_xAs epilayers grown by low temperature molecular beam epitaxy in a wide range of Mn concentrations (0.01
15
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Magnetic Properties of Epitaxial Fe/(Ga,Mn)As Hybrids

42%
Kalbarczyk K., Dziatkowski K., Szczytko J., Gosk J., Tokarczyk M., Kowalski G., Twardowski A., Bednarski W., Ostrowski A., Waplak S., Martinek J., Liu X., Furdyna J.
Acta Physica Polonica A
|
2013
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vol. 124
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issue 5
873-876
EN
Thin-film structures composed of two kinds of ferromagnetic material - metallic Fe and semiconducting (Ga,Mn)As - were investigated by means of SQUID magnetometry and ferromagnetic resonance spectroscopy. Dependence of remnant magnetic moment on temperature showed unexpected anisotropic features when recorded along two orthogonal in-plane directions. For one of these orientations, the change in sign of the slope of m(T) curve at the Curie point of (Ga,Mn)As was observed, while for the other, an analogous m(T) curve retained monotonic character. Based on the comparison with ferromagnetic resonance data, the apparent non-monotonicity was attributed to the temperature-induced change of balance between the external magnetic field and uniaxial magnetic anisotropy in the plane of Fe layer.
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