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Wyświetlanie 1-15 z 54
Tytuł:
Mechanisms of the Magneto-Optical Activity of Rare-Earth Ions in Rare-Earth Iron Garnet Single Crystals
Autorzy:
Tsidaeva, N.
Abaeva, V.
Magkoev, T.
Powiązania:
https://bibliotekanauki.pl/articles/1490761.pdf
Data publikacji:
2012-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Gg
78.20.Ls
Opis:
The magnetic and magneto-optical properties of the typical representatives of three rare-earth iron garnets (RIG) groups: with heavy rare-earth elements Yb, Er, Dy, Tb; with elements from the middle of lanthanide series Gd, Sm, and with light rare-earth element Nd are presented. In contradistinction to other work on the Faraday rotation, which were done only at 1152 nm (8696 $cm^{-1}$), here we present FR spectra obtained in the energy region 5500-20000 $cm^{-1}$ with high optical resolution. The investigations have been done at temperatures of 5, 82, 130, 295 K using magnetic field up to 25 kOe applied parallel to the [111] crystallographic axis of the crystals. It has been shown that the contribution proportional to the magnetic field and independent of temperature to the mixing of the ground state multiplets exceeds the paramagnetic contribution in YbIG, ErIG, GdIG, SmIG. In Tb and Dy iron garnets contributions from the two mechanisms have opposite signs, and the paramagnetic mechanism gives the greatest contribution to the Faraday rotation. Nevertheless, the contribution of the diamagnetic mechanism, caused by the influence of the exchange field in the iron sublattices on rare-earth ions, is significant, and it is necessary to take it into account. Anomalously large magneto-optical activity is observed in NdYIG. This is the result of contributions of the same sign and approximately equal in magnitude from the paramagnetic and diamagnetic mechanisms.
Źródło:
Acta Physica Polonica A; 2012, 121, 1; 74-77
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Two-Particle Parasitic Effects in Rare-Earth Doped Waveguides
Autorzy:
Jaskorzynska, B.
Powiązania:
https://bibliotekanauki.pl/articles/2008215.pdf
Data publikacji:
1999-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.-k
Opis:
This paper discusses Er-doped optical waveguides implemented in glass materials. The emphasis is put on physical limitations posed by concentration dependent nonlinear effects and on methods for their characterization. Examples of recently demonstrated, best performance integrated active devices are also given.
Źródło:
Acta Physica Polonica A; 1999, 95, 5; 743-747
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
IV-VI Semimagnetic Semiconductors with Rare Earth Ions
Autorzy:
Story, T.
Powiązania:
https://bibliotekanauki.pl/articles/1967997.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Ck
75.30.Et
Opis:
The electronic and magnetic properties as well as the applications of IV-VI semiconductors with rare earth ions of Eu and Yb are briefly discussed. The detailed analysis is presented of the recent experimental investigations of the magnetic and transport properties of IV-VI semimagnetic crystals with Gd. It concerns, in particular, the effect of Fermi level position controlled f-f exchange interaction between Gd ions in Sn$\text{}_{1-x}$Gd$\text{}_{x}$Te.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 663-672
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Valency of Selected Rare-Earth Ions in SnTe Matrix
Autorzy:
Gołacki, Z.
Heinonen, M.
Powiązania:
https://bibliotekanauki.pl/articles/1963378.pdf
Data publikacji:
1997-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.60.-i
Opis:
X-ray photoelectron spectroscopy experiments on SnTe crystals doped by Sm, Eu, and Yb were performed to determine the valency of these ions in the SnTe matrix. The analysis of the X-ray photoelectron spectroscopy valence-band spectra revealed that Eu and Yb are divalent while Sm is trivalent in SnTe. These conclusions were confirmed by studies of the binding energies of core levels (4d-levels of Yb and 3d -levels of Sm and Eu), which are not presented here.
Źródło:
Acta Physica Polonica A; 1997, 91, 4; 779-782
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rare Earth Centres in Mixed Compound Crystals
Autorzy:
Kozanecki, A.
Powiązania:
https://bibliotekanauki.pl/articles/1945470.pdf
Data publikacji:
1996-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.-i
78.55.-m
78.50.Ge
Opis:
A review of the Yb impurity related centres in mixed InP-based crystals has been presented. It is shown that Yb$\text{}^{3+}$ ions can be utilized to probe alloy disorder, both in cationic (GaInP) and anionic (InPAs) alloys. The existence of alloy disorder manifested itself in the photoluminescence spectra reflecting local atomic structure of the Yb centres. The dominant emissions have been ascribed to the Yb-P$\text{}_{4}$Ga$\text{}_{12}$ and Yb-P$\text{}_{4}$-Ga$\text{}_{11}$In complexes in GaInP and to Yb-P$\text{}_{4}$ and Yb-P$\text{}_{3}$As centres in InPAs. The excitation and relaxation mechanisms of the 4f-shell of Yb$\text{}^{3+}$ ions were also investigated. It was found that the temperature quenching of the Yb$\text{}^{3+}$ luminescence was accompanied with the appearance of two thermally activated photoluminescence bands. It is suggested that photoluminescence at an energy of 25 meV below the energy gap is due to recombination of excitons bound at Yb-related centres. Relaxation of the excited 4f-shell of Yb$\text{}^{3+}$ ions proceeds via back transfer of the excitation energy from the 4f-shell to excitons bound at Yb-centres.
Źródło:
Acta Physica Polonica A; 1996, 90, 1; 73-82
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Single-Ion Rare Earth Anisotropy in ThMn$\text{}_{12}$-Type Compounds
Autorzy:
Stefański, P.
Powiązania:
https://bibliotekanauki.pl/articles/1931244.pdf
Data publikacji:
1994-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
75.50.Gg
Opis:
The single-ion rare earth anisotropy was investigated in ThMn$\text{}_{12}$-type compounds. For this purpose the crystal electric field parameter values were studied. In these compounds, described by formula RFe$\text{}_{12-x}$T$\text{}_{x}$, R = rare earth, T = Ti, V, Cr, Mo, W and Si, the T atoms have strong crystallographic site preference changing the local crystal electric field potential which "sees" the rare earth ion. The crystal electric field potentials A$\text{}_{2}^{0}$ were calculated considering this site preference. The summations were performed taking into account the nearest neighborhood of the rare earth ion according to the recent results of band structure calculations. The charges of the surrounding Fe and T atoms were established applying the chemical bond model proposed by Pauling. The absolute value of A$\text{}_{2}^{0}$ decreases when the content of vanadium increases in 8(i) position, which is in agreement with experimental data. Localization of Si atoms in 8(j) and 8(f) causes a decrease in A$\text{}_{2}^{0}$. The $\text{}^{155}$Gd Mössbauer spectroscopy data confirm this fact. Miedema's "macroscopic" atom model of cohesion in alloys was applied for interpretation of the role of T atoms in the isomer shift and volume effects.
Źródło:
Acta Physica Polonica A; 1994, 85, 3; 615-621
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electroluminescence from Rare Earth Activated Materials - New Concepts
Autorzy:
Godlewski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1929609.pdf
Data publikacji:
1993-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.Eq
71.55.Gs
78.50.Ge
Opis:
The recent progress in the field of thin film electroluminescence devices is reviewed. The mechanisms responsible for rare earth excitation in high electric field electroluminescence structures are explained. A new mechanism including rare earth ionization is described. Processes limiting electroluminescence efficiency are also discussed.
Źródło:
Acta Physica Polonica A; 1993, 84, 3; 435-444
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kondo Lattice Models for Rare-Earth and Actinide Systems
Autorzy:
Coqblin, B.
Powiązania:
https://bibliotekanauki.pl/articles/1426694.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
75.10.Nr
75.30.Nr
Opis:
We present here some works on the strong competition between the Kondo effect, magnetic order and eventually spin glass or frustration effect in anomalous rare-earth and actinide systems. First, we develop an underscreened Kondo lattice model with $S_{f}$ = 1 spins for the 5f-electrons and we have recently improved it by deriving, by the Schrieffer-Wolff transformation, a 5f-band with a finite bandwidth. The underscreened Kondo lattice model can account for properties of some uranium and neptunium compounds, like UTe, $Np_2PdGa_3$ or $UCu_2Si_2$ which have a large Curie temperature $T_{c}$ of order 100 K and present also a Kondo behavior. In particular, we can account for the observed maximum of $T_{c}$ under pressure in UTe and the magnetization curves of $NpNiSi_2$ showing the occurrence of the Kondo effect at low temperatures below $T_{c}$. Second, we have studied the properties of disordered cerium alloys like $CeCu_xNi_{1-x}$ or $CeRh_xPd_{1-x}$ by considering the Kondo effect, a ferromagnetic order and a spin glass behavior described by several approaches. The van Hemmen approach gives a good explanation of the properties of cerium alloys and we are describing the magnetic glass clusters which occur in both spin glass and ferromagnetic phases. Third, we present a new description of a frustrated Kondo lattice model, which can account for the behavior under pressure or doping of some ytterbium compounds like $Yb_2Pd_2Sn$ and YbAgGe.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1005-1013
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lattice Location of Rare Earth Ions in Semiconductors and Their Optical Activity
Autorzy:
Kozanecki, A.
Powiązania:
https://bibliotekanauki.pl/articles/1929781.pdf
Data publikacji:
1993-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.80.Ih
78.55.-m
Opis:
Lattice location experiments performed on Yb- and Er-doped III-V semiconducting compounds using Rutherford backscattering and channeling have been reviewed. It has been shown that Yb atoms locate substitutionally in InP and InP-based ternary alloys, while in gallium compounds no substitutional fraction of Yb could be detected. An intense intra-4f-shell luminescence of Yb$\text{}^{3+}$ has been observed in In compounds. The photoluminescence spectra of Yb$\text{}^{3+}$ reflect local alloy disorder in InPAs and GaInP, suggesting that the Yb atoms are tetrahedrally coordinated. No Yb-related emission could be observed in gallium compounds, except a weak Yb$\text{}^{3+}$ photoluminescence in GaP. An evidence has been presented that Er atoms introduced into III-V compounds locate predominantly at interstitial positions. In GaAs they move into tetrahedral lattice sites as a result of thermal annealing at temperatures higher than 600°C. The location of Er atoms at substitutional positions is accompanied with the disappearance of the intra-4f-shell luminescence of Er$\text{}^{3+}$. The reasons of the observed correlation of luminescence properties and positions of Er and Yb atoms in zincblende lattices are discussed.
Źródło:
Acta Physica Polonica A; 1993, 84, 5; 881-888
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Threefold Symmetric Magnetic Two-Ion Coupling in hcp Rare-Earth Metals
Autorzy:
Jensen, J.
Powiązania:
https://bibliotekanauki.pl/articles/1953160.pdf
Data publikacji:
1997-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
75.10.-b
75.25.+z
Opis:
The heavy rare earths crystallize in the hcp structure. Most of the magnetic couplings between two ions in these metals are independent of the two different orientations of the hexagonal layers. However, trigonal anisotropy terms may occur, reflecting that the c-axis is only a threefold axis. In the presence of a trigonal coupling the symmetry is reduced, and the double-zone representation in the c-direction ceases to be valid. The strong interaction between the transverse optical phonons and the acoustic spin waves propagating in the c-direction of Tb detected more than twenty years ago, was the first example of a trigonal coupling found in these systems. A few years ago a careful neutron-diffraction study of the c-axis modulated magnetic structures in Er showed the presence of higher harmonics at positions along the c-axis translated by odd multiple of 2π/c. This indicates distortions of the structures due to trigonal couplings, and the same characteristic phenomenon has now also been observed in Ho. Additionally, mean-field calculations show that a trigonal coupling in Ho is required, in order to explain the increase in the commensurable effects observed for the 8 and 10 layered periodic structures, when a field is applied along the c-axis.
Źródło:
Acta Physica Polonica A; 1997, 91, 1; 89-103
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
L$\text{}_{1}$ Absorption Edge of the 4f Heavy Rare-Earth Metals
Autorzy:
Shrivastava, B. D.
Joshi, S. K.
Powiązania:
https://bibliotekanauki.pl/articles/1920520.pdf
Data publikacji:
1992-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
The wavelengths of the L$\text{}_{1}$ absorption edges of the 4f heavy rare-earth metals ($\text{}^{65}$Tb to $\text{}^{71}$Lu) have been measured using a 40 cm curved crystal spectrograph of the Cauchois-type in the transmission mode. The measured values have been found to fit nicely in the modified Moseley diagrams. The absence of the white lines at the L$\text{}_{1}$ edges of the rare earths in metallic form and its occurrence in their compounds has been discussed.
Źródło:
Acta Physica Polonica A; 1992, 81, 3; 385-392
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gd$\text{}^{3+}$ Spin-Phonon Interactions in Rare-Earth Fluoride Crystals
Autorzy:
Paradowski, M. L.
Misiak, L. E.
Powiązania:
https://bibliotekanauki.pl/articles/2035540.pdf
Data publikacji:
2002-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
76.30.Kg
Opis:
The X-band EPR study of Gd$\text{}^{3+}$-doped LaF$\text{}_{3}$, La$\text{}_{0.9}$Ce$\text{}_{0.1}$F$\text{}_{3}$, La$\text{}_{0.9}$Nd$\text{}_{0.1}$F$\text{}_{ }$3, LiYF$\text{}_{4}$ and LiY$\text{}_{0.9}$Yb$\text{}_{0.1}$F$\text{}_{4}$ single crystals in the temperature range 4.2-295 K was carried out in order to investigate the Gd$\text{}^{3+}$ spin-phonon interactions. Spin-Hamiltonian parameters are analysed in the light of the superposition model and the rotational invariance theory for phonon-induced contributions to spin-Hamiltonian parameters. The 4f$\text{}^{7}$ electron-phonon interactions can be described by the Debye model. It is suggested, from the rotational invariance mechanism for phonon-induced contributions to spin-Hamiltonian parameters, that the rotational contributions are much smaller than those from the strain. Temperature-induced distortions of the crystal field, as well as these distortions caused by the La$\text{}^{3+}$/Nd$\text{}^{3+}$ and Y$\text{}^{3+}$/Yb$\text{}^{3+}$ substitutions, influence significantly the 4f$\text{}^{7}$ electron-phonon interactions. The coupling constant K$\text{}_{2}$ of 4f$\text{}^{7}$ electrons to the whole phonon spectrum of the crystal lattice is stronger in the LaF$\text{}_{3}$, La$\text{}_{0.9}$Ce$\text{}_{0.1}$F$\text{}_{3}$, La$\text{}_{0.9}$Nd$\text{}_{0.1}$F$\text{}_{3}$ with larger temperature-induced distortion of the Gd$\text{}^{3+}$ site symmetry than in LiYF$\text{}_{4}$, LiY$\text{}_{0.9}$Yb$\text{}_{0.1}$F$\text{}_{4}$. Our results are compared with those for Gd$\text{}^{3+}$-doped RbCdF$\text{}_{3}$ and PbF$\text{}_{2}$ single crystals.
Źródło:
Acta Physica Polonica A; 2002, 102, 3; 373-384
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transport and Magnetic Properties of Rare Earth Compounds Epitaxially Grown on Semiconductors
Autorzy:
Chroboczek, Jan
Powiązania:
https://bibliotekanauki.pl/articles/1888050.pdf
Data publikacji:
1991-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.My
68.55.-a
75.50.Pp
Opis:
Growth, crystallographic structure, electrical transport and magnetic properties of cubic Er pnictides and hexagonal Er silicide layers, epitaxially grown on semiconductors, are reviewed. Magnetoresistance anomalies observed at low temperatures are discussed in terms of a model developed for electron-magnetic moment interactions in antiferromagnetic systems.
Źródło:
Acta Physica Polonica A; 1991, 80, 2; 179-192
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Symmetry Induced Half-Metallic Alkaline Earth Ferromagnets
Autorzy:
Adamowicz, L.
Wierzbicki, M.
Powiązania:
https://bibliotekanauki.pl/articles/1810473.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
71.20.Dg
72.25.Ba
75.10.Lp
Opis:
Search for new half-metallic ferromagnetic binary compounds composed of alkaline earth and III (boron) or IV (carbon) elements is reported. Ab initio all-electron density functional theory calculations in the generalised gradient approximation indicate possibility of half-metallic ferromagnetism. This is a new class of theoretically predicted hypothetical materials, without transition metal elements, not as yet discovered experimentally. Ferromagnetism is expected to be induced by suitable crystalline structure with lattice constant above some critical value. The predominant p electrons mechanism seems to be responsible for the formation and interactions of localised magnetic moments on boron or carbon atoms.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 217-219
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetism in Rare-Earth-Transition Metal Systems. Magnetization Reversal and Ultra-High Susceptibility in Sandwiched Thin Films Based on Rare-earth and Cobalt Alloys
Autorzy:
Baczewski, L.T.
Givord, D.
Alameda, J. M.
Dieny, B.
Nozieres, J. P.
Rebouillat, J. P.
Prejean, J. J.
Powiązania:
https://bibliotekanauki.pl/articles/1929319.pdf
Data publikacji:
1993-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.-m
75.30.Gw
75.70.-i
75.70.Fr
Opis:
This paper is composed of two parts: theoretical and experimental. The theoretical part is divided into several sections. The main characteristic properties of 3d (transition metals) and 4f (rare-earth metals) magnetism are explained in the second section. The properties of rare-earth-transition metal compounds are discussed in the third section, particularly with respect to applications. The fourth section is devoted to the rapidly growing field of magnetic thin films. Specifrc properties of ultra-thin films and multilayers are summarized. In the experimental part the original magnetic properties of sandwich films, consisting of a soft amorphous Co-Zr layer placed between two Sm-Co layers with different coercivities, are reported.
Źródło:
Acta Physica Polonica A; 1993, 83, 5; 629-641
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 54

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