Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl

Refine search results

Journals help

  1. 42 Acta Physica Polonica A

Years help

  1. 1 2018

  2. 2 2017

  3. 2 2015

  4. 1 2014

  5. 3 2013

More...
Authors help

  1. 6 Twardowski A.

  2. 4 Goryca M.

  3. 4 Kossacki P.

  4. 3 Blinowski J.

  5. 3 Gaj J.

More...
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 42

Number of results on page
first rewind previous Page / 3 next fast forward last

Search results

Search:
in the keywords:  71.70.Gm
help Sort By:

help Limit search:
first rewind previous Page / 3 next fast forward last
1
Content available remote

s-p-d-f Exchange Interactions in Mn and Eu Based IV-VI Semimagnetic Semiconductors

100%
Dietl T., Bauer G.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 5
729-732
EN
We evaluated exchange integrals which describe the spin dependent coupling between effective mass electrons and localized spins in the IV-VI semi-magnetic semiconductors taking into account contributions from the direct Coulomb exchange as well as from the hybridization between band states and magnetic shells. The obtained constants compare favorably with the experimental values for both the Mn- and the Eu-based compounds. We also discuss some peculiarities of IV-VI semimagnetic semiconductors, which may render the virtual-crystal approximation invalid.
2
Content available remote

Exchange Integrals in Hg_{0.95}Mn_{0.05}Se Obtained by the Wave Shape Analysis of Shubnikov-de Haas Oscillations

63%
Dybko K., Kossut J.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 4
697-700
EN
The Shubnikov-de Haas oscillations were measured in Hg_{0.95}Mn_{0.05}Se at liquid helium temperatures, in magnetic fields up to 13 tesla. The analysis of the experimental data was performed by means of the wave shape method. The dependence of effective g-factor of the conduction electrons and difference Dingle temperature on magnetic field was determined. Non-zero difference Dingle temperature is a clear evidence of spin dependent scattering in this material. The sp-d exchange constants consistent with extracted spin splitting and difference Dingle temperature, α = -0.39 ± 0.06 eV, β = 0.95 ± 0.07 eV, are in good agreement with the values obtained from magnetooptics.
3
Content available remote

Electronic Structure of Doped La-Mn-O Perovskites

63%
Demeter M., Neumann M., Galakhov V. R., Ovechkina N. A., Kurmaev E. Z., Labachevskaya N. I.
Acta Physica Polonica A
|
2000
|
vol. 98
|
issue 5
587-591
EN
The electronic structure of the doped perovskite manganese oxides La_{1-x}Sr_{x}MnO_{3} and La_{1-x}Ba_{x}MnO_{3} has been investigated by X-ray photoelectron and X-ray emission spectroscopy. By comparing the O K_{α} and Mn L_{α} X-ray emission spectra with the valence band X-ray photoelectron spectra we could localize the Mn 3d and O 2p states into the valence band. Our data are compared with previous band structure calculations. The value of the Mn 3s splitting does not change with Sr-doping in the concentration region from x=0.0 till x=0.3. This shows that the doping holes have mainly oxygen p character. The large value of the splitting indicates that the 3d electrons are in the high-spin state.
4
Content available remote

s,p-d Exchange Constants of ZnFeTe Diluted Magnetic Semiconductor

63%
Mac W., Herbich M., Khoi N. T., Twardowski A., Shapira Y., Demianiuk M.
Acta Physica Polonica A
|
1995
|
vol. 88
|
issue 5
845-848
EN
Reflectance and degree of polarization of reflectance of the free exciton in Zn_{1-x}Fe_{x}Te (x ≈ 0.002) was measured at T = 1.9 K and magnetic field up to 5 T. Combining the exciton splitting with the magnetization data we estimated the exchange constant N_{0}(α-β) = 2.1 eV.
5
Publication available in full text mode
Content available

Distance Dependence of the Mn-Mn Exchange Interaction in IV-VI Semimagnetic Semiconductors

63%
Łusakowski A., Górska M.
|
EN
In the present paper we calculate the exchange interaction between two manganese ions in IV-VI semiconductors with the rocksalt structure. The method of calculations is based on the fourth order perturbation theory with respect to hybridization between band states and localized d orbitals of Mn ions. This hybridization is described by three Harrison integrals: V_{pdσ},V_{pdπ}, and V_{sdσ}. The band states of IV-VI semiconductor are obtained from the semiempirical tight binding model built from s and p orbitals of cations and anions. The resulting exchange term in the Hamiltonian is of the form -Σ_{i,j=xyz}J_{ ij}Ŝ^1_iŜ^2_j, however nondiagonal terms of the exchange integral tensor J_{i≠j} are very small. The dependence of J_{ij} on the Mn-Mn distance is non-monotonic. We also discuss the influence of the local crystal deformations on the exchange integral.
6
Content available remote

Double Exchange in Mixed-Valency Diluted Magnetic Semiconductors

63%
Blinowski J., Kacman P.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 4
731-734
EN
The role of double-exchange, a non-Heisenberg spin-spin interaction between the magnetic ions of identical chemical nature but different charge states, in the mixed-valency diluted magnetic semiconductors is discussed. The mechanism correlates the spins of magnetic ions by virtual hopping of a d-electron from one ion to the other via the p-band states. We calculate the energy spectrum for pairs of magnetic ions within the charged ionic clusters stabilized by the charge-charge correlations, taking into account simultaneously both the double and the superexchange. The ferromagnetic, non-Heisenberg double exchange might compete with the Heisenberg-like, ferrimagnetic superexchange, thus resulting in canted alignments of ionic spins.
7
Content available remote

Surface Studies of Re_{3}Fe_{5}O_{12} Garnets, ReFeO_{3} Orthoferrites and ReVO_{4} Orthovanadates

51%
Sobczak E., Żymierska D., Ebel H.
Acta Physica Polonica A
|
1996
|
vol. 89
|
issue 3
329-333
EN
The X-ray photoelectron spectra for Re_{3}Fe_{5}O_{12} garnets, ReFeO_{3} orthoferrites and ReVO_{4} orthovanadates have been measured by using Mg K_{α} radiation. The O 1s, Re 4d, Fe 2p, and V 2p photoelectron spectra were studied. A very big difference was observed between ReFeO_{3} orthoferrites and ReVO_{4} orthovanadates, mainly the Fe 2p_{3/2} lines were double broader than V 2p_{3/2} ones, and the O 1s line is split by about 1.6 eV for orthoferrites, while this line is single for orthovanadates. The O 1s peak at 531.8 eV with intensity about 70% of the main peak is interpreted as originated from a charge fluctuation between oxygen and iron ions due to superexchange interaction.
8
Content available remote

Anderson-Kondo Lattice Hamiltonian from the Anderson-Lattice Model: A Modified Schrieffer-Wolff Transformation and the Effective Exchange Interactions

51%
Kądzielawa-Major E., Spałek J.
|
|
vol. 126
|
issue 4a
A-100-A-104
EN
We derive the Anderson-Kondo lattice model by applying canonical perturbation expansion for the Anderson-lattice model in direct space. The transformation is carried out up to the fourth order by a modified Schrieffer-Wolff transformation: we separate the part of hybridization term responsible for the high-energy processes (involving the largest in-the-system intraatomic Coulomb interaction between f electrons) and replace it with the virtual processes in higher orders. The higher-order processes lead to three separate exchange interactions. The obtained Hamiltonian contains both the Kondo (f-c) and the superexchange (f-f) interactions, as well as a residual hybridization responsible for the heavy-quasiparticle formation. This effective Hamiltonian can be used to analyze the magnetic or the paired states, as well their coexistence in heavy-fermion systems. The magnitudes of both the Kondo exchange and the superexchange integrals are estimated as a function of bare hybridization magnitude.
9
Content available remote

Semimagnetic Semiconductors

51%
Gaj J.
|
|
vol. 96
|
issue 5
651-664
EN
This paper contains a description and explanation of selected basic phenomena characteristic of bulk semimagnetic semiconductors: giant Faraday rotation and giant Zeeman splitting, mean field approximation and its limitations, ion-ion interaction, its measurements and its influence on magnetic properties, etc. The basic part is followed by a discussion of a personal choice of new perspectives open by the introduction of diluted magnetic semiconductors in semiconductor quantum structures. In particular, the role of magnetic ions in characterization of semiconductor quantum structures and low-dimensional excitonic systems is analyzed. Particular attention is paid to magnetooptical phenomena and magnetooptical experimental methods in large gap II-VI semimagnetic semiconductors.
10
Content available remote

Beyond the Virtual Crystal Approximation in Diluted Magnetic Semiconductors

51%
Tworzydło J.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 2
391-394
EN
We present a new model approach which goes beyond the virtual crystal approximation and the molecular field approximation in the description of the spin splitting of band states in diluted magnetic semiconductors. The theory is formulated within a one-band effective mass approximation and explicitly takes into account a chemical and magnetic disorder caused by substitutional ions. The results confirm the apparent dependence of the p-d exchange integral on x in Cd_{1-x}Mn_{x}S for small concentrations of Mn ions and we predict the asymmetric field and temperature dependence of the spin splitting in this compound.
11
Content available remote

Magnetism in TmCo₂

51%
Šebesta J., Prchal J., Valenta J., Kratochvílová M., Sechovský V.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 2
379-381
EN
Recently a new wave of interest in physics of RCo₂ compounds has been boosted by reports on unusual magnetic short range order configurations in the heavy rare-earth RCo₂ ferrimagnets in paramagnetic state. The newly observed phenomenon called parimagnetism consists in a short-range antiferromagnetic coupling between small ferromagnetic Co clusters and the nearest rare-earth moments. This paper is devoted to results of our experimental investigation of carefully prepared and characterized samples of TmCo₂, a compound on which controversial results can be found in literature. Detailed magnetization, AC susceptibility, specific heat and electrical resistivity measurements revealed two magnetic phase transitions at 4.6 and 3.6 K, respectively. The anomalies connected with the transitions are strongly dependent on magnetic field and hydrostatic pressure. The AC susceptibility anomaly connected with the onset of parimagnetism has been found at T_{f}=35 K. Contrary to other heavy rare-earth RCo₂ counterparts T_{f} of TmCo₂ is entirely pressure independent.
12
Content available remote

Spin Correlations Effect on the Electrical Resistivity in Rare Earth Intermetallics

51%
Szukiel A., Peisert J.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 1
229-233
EN
The magnetic resistance anomaly in the paramagnetic phase of ordered cubic rare earths systems is considered. Within simple model of the free electrons scattering on the localized moments of magnetic ions system in the Born approximation it is shown that the negative temperature coefficient of the resistivity can be attributed to the spin correlations. The condition for the anomaly is formulated, which generalizes the ones known for the crystal field-free systems in the critical region. The conclusions are illustrated by the results of the resistivity calculations for DyAg and their comparison with the experimental data.
13
Content available remote

Ferromagnetism in Cr-Based Diluted Magnetic Semiconductors

51%
Blinowski J., Kacman P., Majewski J.
Acta Physica Polonica A
|
1995
|
vol. 88
|
issue 4
683-686
EN
It has been recently established that in zinc chalcogenides with Cr^{2+} paramagnetic ions the p-d interactions are ferromagnetic. We clarify the origins of this property and make predictions concerning other Cr-based diluted magnetic semiconductors. The observation of the ferromagnetic p-d interaction resuscitated hopes for ferromagnetic d-d exchange interactions in diluted magnetic semiconductors. We have calculated the nearest-neighbor superexchange integrals in Cr-based diluted magnetic semiconductors. No simple correlation between the signs of p-d and d-d interactions has been found. Still, there are extended energy regions where the calculated superexchange is ferromagnetic and the act ual parameters of DMS with Cr^{2+} seem to match these regions.
14
Content available remote

Local Modes of Transition Metal Ions (Mn, Fe, Co) in Mercury Chalcogenides

51%
Szuszkiewicz W., Dybko K., Dynowska E., Witkowska B., Jouanne M., Julien C.
Acta Physica Polonica A
|
1995
|
vol. 88
|
issue 5
937-940
EN
Optical phonons in mercury chalcogenides doped with selected transition metal ions are investigated by infrared reflectivity and Raman scattering measurements performed at helium temperatures. The results obtained for Hg_{1-x}Fe_{x}Se, Ηg_{1-x}Co_{x}Se, Ηg_{1-x}Fe_{x}S and Hg_{1-x}Co_{x}S mixed crystals demonstrate the significant influence of the 3d electron correlation effects and/or sp-d hybridization on the transition metal ion local mode frequency.
15
Content available remote

Point-Contact Spectroscopy of Ce_{1-x}RE_{x}Ni_{5} (RE = Pr, Nd)

51%
Kačmárová T., Reiffers M., Garcia Soldevilla J., Goméz Sal J., Espeso J., Blanco J.
Acta Physica Polonica A
|
2000
|
vol. 97
|
issue 5
795-798
EN
We report on the study of the electron-quasiparticle interaction function in Ce_{1-x}RE_{x} Ni_{5} (RE = Pr, Nd) pseudobinary compounds for x = 0, 0.2, 0.5, 0.8, and 1 measured by means of point-contact spectroscopy. The measured point-contact spectra (d^{2}V/dI^{2} - directly proportional to the electron- quasiparticle interaction function) of the heterocontacts between Ce_{1-x} RE_{x}Ni_{5} and Cu in the ballistic regime are presented.
16
Content available remote

Inelastic Electron Tunneling Spectroscopy of a Mn Dimer

51%
Delgado F., Fernández-Rossier J.
Acta Physica Polonica A
|
2012
|
vol. 122
|
issue 2
304-306
EN
A scanning tunneling microscope can probe the inelastic spin excitations of single magnetic atoms in a surface via spin-flip assisted tunneling. A particular and intriguing case is the Mn dimer case. We show here that the existing theories for inelastic transport spectroscopy do not explain the observed spin transitions when both atoms are equally coupled to the scanning tunneling microscope tip and the substrate, the most likely experimental situation. The hyperfine coupling to the nuclear spins is shown to lead to a finite excitation amplitude, but the physical mechanism leading to the large inelastic signal observed is still unknown. We discuss some other alternatives that break the symmetry of the system and allow for larger excitation probabilities.
17
Content available remote

Influence of Local Potential on Exciton Splitting in Highly Diluted Cd_{1-x}Mn_{x}Te

51%
Kłopotowski L., Herbich M., Mac W., Stachow-Wójcik A., Twardowski A.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 4
837-840
EN
We investigated magnetoreflectance and magnetization of highly diluted bulk Cd_{1-x}Mn_{x}Te crystals 0.2% ≤ x ≤ 10%. The exchange constant in terms of mean field approximation and virtual crystal approximation (the ratio of the heavy hole exciton splitting to mean spin per unit cell) was evaluated and found x-dependent. This deviation from the mean field approximation and virtual crystal approximation prediction is caused by the local potential introduced by Mn ions. We discuss the problem within a Wigner-Seitz approach and within a model of magnetic and chemical disorder based on the alloy theory.
18
Content available remote

Crystal Field Analysis of Cr^{3+} Doped SrAl_{2}O_{4} Spinel

51%
Stanciu M., Ciresan M., Avram N.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 4
544-546
EN
The present work is devoted to the crystal field analysis of trivalent chromium doped in SrAl_{2}O_{4} spinel in the frame of the exchange charge model of crystal field. Using the shell model and pair approximation, we optimize the geometric structure of the crystal. The approach enables the modeling of the crystal field parameters and thus calculates the energy level scheme of Cr^{3+} ions in spinel SrAl_{2}O_{4}. The obtained results are compared with experimental data and discussed.
19
Content available remote

Calorimetric Absorption Spectroscopy of Deep Defects and Quantum Dots

51%
Heitz R., Podlowski L., Böhrer J., Hoffmann A., Broser I., Bimberg D.
Acta Physica Polonica A
|
1995
|
vol. 88
|
issue 4
619-630
EN
In recent years calorimetric absorption spectroscopy has been developed to a powerful tool of semiconductor spectroscopy based on the detection of nonradiative relaxation processes. Calorimetric absorption spectroscopy is an ultrasensitive quantitative absorption technique. Recent investigations of Fe in III-V semiconductors and of InAs/GaAs quantum dots are presented here to illustrate the potential of the method. Sharp absorption lines are observed at the low energy onset of the Fe^{3+/2+} charge transfer band in III-V semiconductors. Calorimetric absorption spectroscopy measurements in the mK range reveal a strong temperature dependence of their absorption strength identifying unambiguously Fe^{3+}(^{6}A_{1}(S)) as a ground state. The excited state is attributed to (Fe^{2+},h). The importance of exchange interaction for the ob­served fine structure is pointed out and binding energies are determined. The quantum yield of the intracenter ^{5}Τ_{2}-^{5}E transition of F^{2+} is determined to be below 50% at 2 K. A correlation between the nonradiative relaxation rate and the isotope splitting of the ^{5}Τ_{2}-^{5}E transition is observed, demonstrat­ing the crucial role of the dynamical Jahn-Teller coupling of the ^{5}Τ_{2} state to local Τ_{2} modes for the multiphonon relaxation process. Quantum dots having a d-function density of states should exhibit no Stokes shift between absorption and emission as observed for one- and two-dimensional systems. Calorimetric absorption spectroscopy demonstrates ground state absorption coinciding in energy with the luminescence for self- organized InAs/GaAs quantum dot structures grown by MBE. Transitions into excited hole states are resolved and a comparison to photoluminescence excitation spectroscopy is presented.
20
Content available remote

Magnetization Dynamics of a (Cd,Mn)Te Quantum Well in Pulsed Magnetic Field

51%
Kobak J., Goryca M., Kossacki P., Golnik A., Karczewski G., Wojtowicz T., Gaj J.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 5
907-908
EN
In this paper we present studies of magnetization relaxation in a (Cd,Mn)Te quantum well containing 3.2% of Mn, after a pulse of magnetic field. The relaxation was found to be very fast, with dominant component faster than 10 ns. Upon application of static magnetic field the relaxation does not slow down, in contrast with the behavior of very diluted quantum wells or bulk material.
first rewind previous Page / 3 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.