Библиотека института физики им. Л.В. Киренского СО РАН

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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Greben'kova Yu.E., Sokolov A. E., Edel'man I. S., Andreev N. V., Chichkov V. I.
Заглавие : Linear and circular magnetic dichroism in thin films of lanthanum manganite
Коллективы : Euro-Asian Symposium "Trends in MAGnetism": Nanomagnetism
Место публикации : V Euro-Asian simposium "Trend in MAGnetism": Nanomagnetism: abstracts. - Vladivostok: FEFU, 2013. - P.324. - ISBN 978-5-7444-3124-2
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Turchin P. P., Sorokin B. P., Burkov S. I.
Заглавие : Non-linear electromechanical properties and propagation of acoustic waves under the action of external static fields in the piezoelectric La3Ga5SiO14
Коллективы : Красноярский государственный университет
Место публикации : Russ. Ultrason./ изд. орг. . - 1997. - Vol. 27, Is. 3. - P.193-196. - ISSN 0048-8828
Ключевые слова (''Своб.индексиров.''): acoustic wave transmission--anisotropy--data reduction--electric field effects--electrostriction--lanthanum compounds--piezoelectric materials--external static fields--nonlinear electromechanical properties (nemp)--single crystals
Аннотация: A full set of parameters has been obtained for the linear and non-linear electrostriction properties of an La3Ga5SiO14 single crystal. The data have been used for an analysis of the anisotropy of the anharmonic effects and special features of the influence of a constant electric field on the propagation of acoustic waves in this crystal.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Sorokin B. P., Turchin P. P., Burkov S. I., Glushkov D. A., Aleksandrov K. S.
Заглавие : Influence of static electric field, mechanical pressure and temperature on the propagation of acoustic waves in La3Ga5SiO14 piezoelectric single crystals
Коллективы : International frequency control symposium
Место публикации : Proc Annu IEEE Int Freq Control Symp. - 1996. - P.161-169. - ISBN 01616404
Ключевые слова (''Своб.индексиров.''): acoustic wave transmission--anisotropy--electric field effects--lanthanum compounds--piezoelectric materials--pressure effects--thermal effects--piezoelectric single crystals--single crystals
Аннотация: On the fundamental of our original experimental results the full set of tensorial components of linear and nonlinear electromechanical properties and temperature coefficients of material properties for La3Ga5SiO14 piezoelectric crystals have been obtained. These data were used for the analysis of influence of static electrical field and of uniaxial homogeneous mechanical pressure on the propagation anisotropy of acoustic waves superposed by the temperature variations.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Aleksandrov K. S., Sorokin B. P., Turchin P. P., Burkov S. I., Glushkov D. A., Karpovich A. A.
Заглавие : Effects of static electric field and of mechanical pressure on surface acoustic waves propagation in La3Ga5SiO14 piezoelectric single crystals
Коллективы : IEEE International Ultrasonics Symposium
Место публикации : Proc IEEE Ultrason Symp. - 1995. - Vol. 1. - P.409-412. - ISBN 1051-0117
Ключевые слова (''Своб.индексиров.''): electric field effects--electrostriction--lanthanum compounds--piezoelectric materials--piezoelectricity--pressure effects--quartz--single crystals--tensors--bulk acoustic wave--dielectric permeability--electromechanical bond coefficients--lanthanum gallium silicide--mechanical pressure--nonlinear electromechanical properties--nonlinear piezoelectric effect--piezoquartz--static electric field--tensorial components--ultrasonic propagation
Аннотация: The complete set of tensorial components of linear and nonlinear electromechanical properties for La3Ga5SiO14 piezoelectric crystals have been obtained. These data were used for the analysis of influence of static electrical field and of uniaxial homogeneous mechanical pressure on the propagation of surface acoustic waves.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Balaev D. A., Semenov S. V., Popkov S. I., Dubrovskiy A. A., Sapronova N. V., Volkov N. V.
Заглавие : Relaxation of low-temperature magnetoresistance and magnetization of polycrystalline (La0.5Eu0.5)(0.7)Pb0.3MnO3
Разночтения заглавия :авие SCOPUS: Relaxation of low-temperature magnetoresistance and magnetization of polycrystalline (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3
Место публикации : J. Phys. D. - 2011. - Vol. 44, Is. 25. - Ст.255001. - ISSN 0022-3727, DOI 10.1088/0022-3727/44/25/255001
Примечания : Cited References: 34. - This work was partially supported by the Lavrentyev Competition of the Young Scientist's Projects of the Siberian Branch of the Russian Academy of Sciences, Project No 12. The authors are grateful to A D Balaev and V M Sosnin for useful discussions on the results.
Предметные рубрики: INSULATOR-METAL TRANSITION
GRANULAR FILMS
NANOPARTICLES
PR0.7CA0.3MNO3
PERCOLATION
MANGANITES
Ключевые слова (''Своб.индексиров.''): antiferromagnetic boundaries--characteristic value--ferromagnetic domains--ferromagnetic metal--lanthanum manganites--logarithmic law--low temperatures--magneto-resistive effect--polycrystalline--relative orientation--relaxation of magnetization--temperature fluctuation--time evolutions--time interval--tunnel magnetoresistance--antiferromagnetism--electric resistance--europium--ferromagnetic materials--ferromagnetism--grain boundaries--grain size and shape--lanthanum compounds--lead--magnetic domains--magnetic moments--magnetoelectronics--magnetoresistance--manganese oxide--magnetization
Аннотация: Hysteresis and relaxation of magnetoresistance and magnetization of substituted (La0.5Eu0.5)(0.7)Pb0.3MnO3 lanthanum manganite in a low-temperature region ( 40 K) are investigated. It is shown that at these temperature features of the magnetoresistive effect are determined mainly by spin-dependent tunnelling of carriers via insulating grain boundaries. As was demonstrated previously, the grain boundaries may be antiferromagnetically ordered. Therefore, relaxation of magnetization and resistance is determined by the processes of relative orientation of the magnetic moments of ferromagnetic domains neighbouring the antiferromagnetic boundary of ferromagnetic domains under the action of temperature fluctuations. It is shown that relaxation follows the logarithmic law within the time interval t similar to 10(2)-3x10(3) s. A comparison between time evolutions of the magnetic moment and resistance shows that magnetoresistance and magnetization are related as delta R
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Pchelkina Z. V.
Заглавие : Electronic Structure of p-Type La1-xMx2+MnO3 Manganites in the Ferromagnetic and Paramagnetic Phases in the LDA plus GTB Approach
Разночтения заглавия :авие SCOPUS: Electronic structure of p-Type La 1-x M x 2+ MnO 3 manganites in the ferromagnetic and paramagnetic phases in the LDA + GTB approach
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 112, Is. 5. - P860-876. - ISSN 1063-7761, DOI 10.1134/S1063776111030101
Примечания : Cited References: 47. - This study was supported financially by integration project no. 40 of the Ural and Siberian Branches of the Russian Academy of Sciences, the program "Strong Electron Correlations" of the Russian Academy of Sciences, and the Russian Foundation for Basic Research (project no. 10-02-00251-a).
Предметные рубрики: DOUBLE-EXCHANGE
COLOSSAL MAGNETORESISTANCE
THIN-FILMS
PHYSICS
LA1-XSRXMNO3
RESISTIVITY
SEPARATION
TRANSPORT
MODEL
Ключевые слова (''Своб.индексиров.''): complex structure--cubic materials--ferromagnetic phase--half metals--jahn teller effect--metal properties--metal types--orbitals--p-type--paramagnetic phase--paramagnetic phasis--quasi particles--spectral intensity--spin projections--strong electron correlations--barium--density functional theory--electron correlations--electron density measurement--electronic properties--electronic structure--fermi level--ferromagnetic materials--ferromagnetism--manganese oxide--manganites--paramagnetic materials--paramagnetism--valence bands--lanthanum
Аннотация: The band structure, spectral intensity, and position of the Fermi level in doped p-type La1-xMx2+ MnO3 manganites (M = Sr, Ca, Ba) is analyzed using the LDA + GBT method for calculating the electronic structure of systems with strong electron correlations, taking into account antiferro-orbital ordering and using the Kugel-Khomskii ideas and real spin S = 2. The results of the ferromagnetic phase reproduce the state of a spin half-metal with 100% spin polarization at T = 0, when the spectrum is of the metal type for a quasiparticle with one spin projection and of the dielectric type for the other. It is found that the valence band becomes approximately three times narrower upon a transition to the paramagnetic phase. For the paramagnetic phase, metal properties are observed because the Fermi level is located in the valence band for any nonzero x. The dielectrization effect at the Curie temperature is possible and must be accompanied by filling of d(x) orbitals upon doping. The effect itself is associated with strong electron correlations, and a complex structure of the top of the valence band is due to the Jahn-Teller effect in cubic materials. DOI: 10.1134/S1063776111030101
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Semenov S. V., Popkov S. I., Balaev D. A., Bykov A. A., Dubrovskiy A. A., Petrov M. I., Volkov N. V.
Заглавие : Magnetoresistance of substituted lanthanum manganites La0.7Ca0.3MnO3 upon nonequilibrium overheating of carriers
Разночтения заглавия :авие SCOPUS: Magnetoresistance of substituted lanthanum manganites La 0.7Ca 0.3MnO 3 upon nonequilibrium overheating of carriers
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2011. - Vol. 109, Is. 8. - Ст.83711. - ISSN 0021-8979, DOI 10.1063/1.3573666
Примечания : Cited References: 15. - This study was partially supported by the Russian Foundation for Basic Research, project no. 08-02-00259a, and the Lavrent'ev's Competition of Young Scientists of the Siberian Branch of the RAS, project no. 12.
Ключевые слова (''Своб.индексиров.''): field dependence--lanthanum manganites--low thermal conductivity--manganite materials--negative differential resistivity--non equilibrium--non-linearity--nonequilibrium heating--polycrystalline--positive magnetoresistance--transport currents--electric resistance--electron gas--heating--lanthanum--lanthanum alloys--magnetic fields--magnetoelectronics--magnetoresistance--manganese oxide--manganites--thermal conductivity--current voltage characteristics
Аннотация: Current-voltage characteristics of the polycrystalline substituted lanthanum manganite La0.7Ca0.3MnO3 were experimentally studied at T - 77.4 K in magnetic fields up to 13 kOe. In these characteristics, a portion of negative differential resistivity was observed above a certain threshold value of critical current density j caused, in our opinion, by nonequilibrium heating of the electron gas due to low thermal conductivity of the manganite material. Because of the nonlinearity of the current-voltage characteristics, the field dependences of resistivity rho( H) appear extremely sensitive to the value of a transport current. In this case, the rho( H) dependences reveal both ordinary negative and positive magnetoresistance. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3573666]
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Popkov S. I., Semenov S. V., Balaev D. A., Dubrovskiy A. A., Sablina K. A., Sapronova N. V., Volkov N. V.
Заглавие : Low-temperature resistance and magnetoresistance hysteresis in polycrystalline (La0.5Eu0.5)(0.7)Pb0.3MnO3
Разночтения заглавия :авие SCOPUS: Low-temperature resistance and magnetoresistance hysteresis in polycrystalline (La0.5Eu0.5)0.7Pb 0.3MnO3
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2011. - Vol. 109, Is. 5. - Ст.53711. - ISSN 0021-8979, DOI 10.1063/1.3559303
Примечания : Cited References: 20. - This study was partially supported by the Russian Foundation for Basic Research, Project No. 08-02-00259a and the Lavrentyev Competition of the Young Scientists' Projects of the Siberian Branch of the Russian Academy of Sciences, Project No. 12.
Предметные рубрики: RESISTIVITY MINIMUM
MANGANITES
FILMS
Ключевые слова (''Своб.индексиров.''): antiferromagnets--electrical resistances--ferromagnets--field dependence--inter-grain--lanthanum manganites--low temperatures--low-temperature resistance--polycrystalline--temperature dependence--tunnel contacts--antiferromagnetic materials--europium--ferromagnetic materials--ferromagnetism--hysteresis--lead--magnetic field effects--magnetoelectronics--magnetoresistance--magnets--manganese oxide--paramagnetism--superconducting materials--electric resistance
Аннотация: The behavior of temperature dependences of electrical resistance and magnetoresistance of polycrystalline substituted lanthanum manganite (La0.5Eu0.5)(0.7)Pb0.3MnO3 at low temperatures was thoroughly studied. A broad hysteresis was found in the field dependences of electrical resistance in the low-temperature region. Above 40 K, no hysteresis feature was observed. The temperature T = 40 K corresponds to the temperature of minimum electrical resistance and the temperature T-N to the antiferromagnet-paramagnet phase transition of the material of the intergrain boundaries. In this work we propose a model which explains the observed features of the rho(T) and rho(H) curves at temperatures below T-N by the formation of a network of ferromagnet-antiferromagnet-ferromagnet tunnel contacts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3559303]
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Popkov S. I., Balaev D. A., Semenov S. V., Bykov A. A., Dubrovskiy A. A., Sapronova N. V., Volkov N. V.
Заглавие : Non-linear current-voltage characteristics of (La0.5Eu0.5)(0.7)Pb0.3MnO3 single crystals: Possible manifestation of the internal heating of charge carriers
Коллективы :
Разночтения заглавия :авие SCOPUS: Non-linear currentvoltage characteristics of (La0.5Eu 0.5)0.7Pb0.3MnO3 single crystals: Possible manifestation of the internal heating of chargecarriers
Место публикации : Physica B: ELSEVIER SCIENCE BV, 2010. - Vol. 405, Is. 24. - P4961-4965. - ISSN 0921-4526, DOI 10.1016/j.physb.2010.09.043
Примечания : Cited References: 19. - The authors are grateful to A.N. Lavrov for useful discussions on the results. This study was partially supported by the Russian Foundation for Basic Research, Project no. 08-02-00259a and the Lavrent'ev Young Scientists' Competition of the Siberian Branch of the Russian Academy of Sciences. Project no. 12.
Предметные рубрики: INSULATOR-METAL TRANSITION
PR0.7CA0.3MNO3
MANGANITES
Ключевые слова (''Своб.индексиров.''): manganites--negative differential resistance--cvc--cvc--manganites--negative differential resistance--applied electric field--charge ordering--current switching--cvc--dielectric regions--experimental data--internal heating--lanthanum manganites--metal-dielectric transition--negative differential resistances--non equilibrium--non-linear--sample heating--temperature evolution--transport currents--electric fields--electron gas--europium--heating--lanthanum--lead--manganites--negative resistance--phase separation--single crystals--thermal conductivity--manganese oxide
Аннотация: Temperature evolution of the current-voltage characteristics (CVCs) of a single-crystal lanthanum manganite (La0.5Eu0.5)(0.7)Pb0.3MnO3 is investigated in a wide (up to 1 A) range of instrumental currents. Effects of a transport current and an applied electric field on the resistance of the material are studied in view of possible implementation of the charge ordering break in dielectric regions occurring due to phase separation in manganites. A negative differential resistance portion observed in the CVCs suggests the presence of a current switching effect. Below the temperature of the metal-dielectric transition in (La0.5Eu0.5)(0.7)Pb0.3MnO3, the hysteresis is observed in the CVC. The detailed analysis of the internal sample heating on the basis of experimental data on thermal conductivity showed, however, that these CVC features can be explained within the concept of non-equilibrium heating of electron gas. (C) 2010 Elsevier B.V. All rights reserved.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gokhfeld D. M., Balaev D. A., Shaykhutdinov K. A., Popkov S. I., Petrov M. I.
Заглавие : Current-voltage characteristics of break junctions of high-T-c superconductors
Разночтения заглавия :авие SCOPUS: Current-voltage characteristics of break junctions of high-Tc superconductors
Место публикации : Physica C. - 2007. - Vol. 467, Is. 1-2. - P.80-84. - ISSN 0921-4534, DOI 10.1016/j.physc.2007.09.001
Примечания : Cited References: 19
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
ANDREEV REFLECTION
POLYCRYSTALLINE HTSC
WEAK LINKS
COMPOSITES
Ключевые слова (''Своб.индексиров.''): network of weak links--andreev reflection--hysteretic peculiarity--andreev reflection--hysteretic peculiarity--network of weak links--lanthanum compounds--mathematical models--polycrystalline materials--superconducting materials--andreev reflection--break junctions--hysteretic peculiarity--network of weak links--current voltage characteristics
Аннотация: The current-voltage (I-V) characteristics of break junctions of polycrystalline La1.85Sr0.15CuO4, Y0.75Lu0.25Ba2Cu3O7-delta, Bi1.8Pb0.3Sr1.9Ca2Cu3Ox and composite YBa2Cu3O7-delta + Ag are investigated. The experimental I-V curves exhibit the specific peculiarities of superconductor/normal-metal/superconductor junctions. The relation between an I-V characteristic of network of weak links and I-V dependencies of typical weak links is suggested to describe the experimental data. The I-V curves of typical weak links are calculated by the Kummel-Gunsenheimer-Nicolsky model considering the multiple Andreev reflections. (c) 2007 Elsevier B.V. All rights reserved.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Orlov Yu. S.
Заглавие : Covalence-induced stabilization of an intermediate-spin state and the magnetic susceptibility of LaCoO3
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 104, Is. 3. - P436-444. - ISSN 1063-7761, DOI 10.1134/S1063776107030090
Примечания : Cited References: 24. - This work was supported by the program of the Division of Physical Sciences of the Russian Academy of Sciences “Strong Electronic Correlations,” the integration project SORAN-URORAN (grant no. 74), and the Krasnoyarsk krai Science Foundation
Предметные рубрики: TRANSITION
Ключевые слова (''Своб.индексиров.''): band structure--electron transitions--ground state--hamiltonians--magnetic susceptibility--magnetic variables measurement--spin dynamics--covalence induced stabilization--diagnoalization--orbital degeneracy--spin states--lanthanum compounds
Аннотация: The energies of terms with spins S = 0, 1, 2 have been found using exact diagonalization of the multielectron Hamlitonian of a multiband pd model for the CoO6 cluster. Co (e(g) orbital)-O hops, which form the covalent sigma bond, are shown to decrease the energy of the state (IS) with an intermediate spin (S = 1) as compared to the energy of the state (LS) with a low spin (S = 0). An analogue of the Tanabe-Sugano diagram that takes into account the covalence of the CoO6 cluster is constructed. The state with S = 1 is shown to be a ground state at certain model parameters. An increase in temperature is established to decrease the crystal field and, thus, favors the transition of the ground state from LS to IS at T = 100 K and the transition of the IS ground state to a state (HS) with a high spin (S = 2) at T = 550 K. The magnetic susceptibility of LaCoO3 is calculated with allowance for the LS, IS, and HS states and for the fact that the HS state exhibits threefold orbital degeneracy of the t(2g) shell, which results in an effective orbital moment L = 1 and the importance of spin-orbit interaction. The behavior of this magnetic susceptibility agrees well with the experimental chi(T) dependence of LaCoO3.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Piskunova N. I.
Заглавие : Influence of the four-spin exchange interaction on the magnetic properties of manganites
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2005. - Vol. 17, Is. 37. - P.5881-5888. - ISSN 0953-8984, DOI 10.1088/0953-8984/17/37/023
Примечания : Cited References: 18
Предметные рубрики: METAL-INSULATOR-TRANSITION
PHASE
SUSCEPTIBILITY
LA1-XSRXMNO3
FERROMAGNET
TRANSPORT
Ключевые слова (''Своб.индексиров.''): computer simulation--ion exchange--lanthanum compounds--magnetic properties--monte carlo methods--phase diagrams--phase transitions--four-spin exchange interaction--magnetic phase diagram--manganites--metal-dielectric transition--manganese compounds
Аннотация: It is shown that non-Heisenberg exchange interaction should be taken into account to reproduce the magnetic phase diagram of La(1-x)A(x)MnO(3) (A = Ca, Sr) using only effective exchange parameters and spins. The formation of the four-spin exchange arises from carrier hopping and coincides with the critical concentration metal-dielectric transition. The two- and four-spin exchange parameters are determined by Monte Carlo simulations.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Borisov A. A., Gavrichkov V. A., Korshunov M. M.
Заглавие : Prediction of the in-gap states above the top of the valence band in undoped insulating cuprates due to the spin-polaron effect
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2004. - Vol. 16, Is. 8. - PL93-L100. - ISSN 0953-8984, DOI 10.1088/0953-8984/16/8/L04
Примечания : Cited References: 25
Предметные рубрики: ELECTRONIC-STRUCTURE
LA2-XSRXCUO4
MODEL
ANTIFERROMAGNETISM
SPECTRA
OXIDES
Ключевые слова (''Своб.индексиров.''): quasiparticle band structure--spin-polaron effect--antiferromagnetic materials--approximation theory--doping (additives)--electronic structure--hamiltonians--insulation--magnetic fields--strontium compounds--thermal effects--lanthanum compounds
Аннотация: In the framework of the generalized tight binding method we have calculated the quasiparticle band structure and the spectral functions of the undoped cuprates such as La2CuO4, Sr2CUO2Cl2 etc. Due to spin fluctuations the in-gap state appears above the top of the valence band in the undoped antiferromagnetic insulator similar to in-gap states induced by hole doping. In the ARPES experiments the in-gap states can be detected as weak low energy satellites.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kliava J., Edelman I. S., Potseluyko A. M., Petrakovskaja E. A., Berger R., Bruckental I., Yeshurun Y., Malakhovskii A. V., Zarubina Y. V.
Заглавие : Magnetic and optical properties and electron paramagnetic resonance of gadolinium-containing oxide glasses
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2003. - Vol. 15, Is. 40. - P6671-6681. - ISSN 0953-8984, DOI 10.1088/0953-8984/15/40/005
Примечания : Cited References: 30
Предметные рубрики: ABSORPTION-SPECTRA
FARADAY-ROTATION
SPIN-RESONANCE
IONS
GD3+
SPECTROSCOPY
BEHAVIOR
GD-3
Ключевые слова (''Своб.индексиров.''): doping (additives)--electronic structure--glass--lanthanum compounds--light absorption--magnetic susceptibility--oxides--paramagnetic resonance--positive ions--rate constants--substitution reactions--absorption band--gadolinium containing oxide glasses--positive weiss constants--gadolinium compounds
Аннотация: Magnetic susceptibility, electron paramagnetic resonance (EPR) and optical absorption have been studied in a glass system 20La(2)O(3)-22Al(2)O(3)-23B(2)O(3)-35(SiO2 + GeO2) with a part of La2O3 substituted by Gd2O3 in different concentrations. Positive Weiss constants have been found in more heavily doped glasses and ascribed to clustering of Gd3+ ions. Computer simulations of the EPR spectra show that the short-range ordering in the environment of the Gd3+ ions is well preserved. The relative distribution widths of the ligand coordinates are less than 2%. In the more heavily doped glasses the EPR spectra are superpositions of signals arising from isolated ions and ferromagnetic clusters. The increase of Gd3+ concentration is shown to change substantially the strong optical absorption edge while only small changes of f-f absorption band characteristics are observed. This difference is associated with the different effect of the Gd ion clustering on the mechanisms of the strong absorption in the ultraviolet region and the f-f absorption.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Petrakovskii G. A., Vasil'ev V. N., Sablina K. A.
Заглавие : Two-phase paramagnetic-ferromagnetic state of La0.7Pb0.3MnO3 single-crystal lanthanum manganite
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2002. - Vol. 44, Is. 7. - P1350-1354. - ISSN 1063-7834, DOI 10.1134/1.1494635
Примечания : Cited References: 17
Предметные рубрики: COLOSSAL MAGNETORESISTANCE
MAGNETIC-RESONANCE
DOPED MANGANITES
LA1-XCAXMNO3
SEPARATION
TRANSITION
RELAXATION
EPR
Аннотация: Two phases, paramagnetic and ferromagnetic, were shown by the magnetic resonance method to coexist below the temperature T-C in La0.7Pb0.3MnO3 single crystals exhibiting colossal magnetoresistance. The magnetic resonance spectra were studied in the frequency range 10-78 GHz. The specific features in the behavior of the spectral parameters were observed to be the strongest at the temperatures corresponding to the maximum magnetoresistance in the crystals. The concentration ratios of the paramagnetic and ferromagnetic phases in the samples were found to be sensitive to variations in temperature and external magnetic field. This behavior suggests realization of the electronic phase separation mechanism in the system under study. (C) 2002 MAIK "Nauka/Interperiodica".
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrakovskii G. A., Volkov N. V., Vasil'ev V. N., Sablina K. A.
Заглавие : Magnetic resonance spectrum of a two-phase state in single crystals of La0.7Pb0.3MnO3 lanthanum manganite
Место публикации : JETP Letters. - 2000. - Vol. 71, Is. 4. - P.144-147. - ISSN 0021-3640, DOI 10.1134/1.568300
Примечания : Cited References: 10
Предметные рубрики: FERROMAGNETIC-RESONANCE
LA1-XCAXMNO3
SEPARATION
Аннотация: Two absorption lines are observed over a wide temperature range below T-c in the magnetic resonance spectrum of an La0.7Pb0.3MnO3 single crystal. These lines correspond to two magnetic phases in the sample. The frequency-field dependence of spectra obtained in the range of microwave radiation frequencies 10-77 GHz allows these phases to be interpreted as ferromagnetic and paramagnetic phases. The phase volume ratio depends on the temperature and the magnitude of the external magnetic field. Features in the temperature behavior of parameters of the magnetic absorption line are observed in the region of the highest magnetic resistance of the sample. The results are interpreted within the mechanism of electronic phase separation. (C) 2000 MAIK "Nauka/Interperiodica".
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G., Yakimov L. E.
Заглавие : The role of orbital ordering in the formation of electron structure in undoped LaMnO3 manganites in the regime of strong electron correlations
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 102, Is. 6. - P972-985. - ISSN 1063-7761, DOI 10.1134/S1063776106060112
Примечания : Cited References: 25
Предметные рубрики: COLOSSAL MAGNETORESISTIVE OXIDES
DOUBLE EXCHANGE
BAND
MODEL
Ключевые слова (''Своб.индексиров.''): computational methods--correlation methods--doping (additives)--electrons--ferromagnetic materials--lanthanum compounds--paramagnetic materials--intraatomic electron correlations--mott hubbard correlation gap--orbital ordering--paramagnetic phases--electronic structure
Аннотация: The electron structure of undoped LaMnO3 and slightly doped La1-xSrxMnO3 manganites has been calculated within the framework of a generalized tight binding method with explicit allowance for strong intra-atomic electron correlations. According to the results of these calculations, the ground state in orbitally disordered undoped LaMnO3 ferromagnets would be metallic despite the Mott-Hubbard correlation gap in the spectrum of quasiparticles. Owing to the orbital ordering, the insulating state is stabilized in both antiferromagnetic and paramagnetic phases. In-gap states of a polaron nature with a spectral weight proportional to the dopant concentration have been found near the top of the valence band in La1-xSrxMnO3. As the doping level increases, a metal state appears in the ferromagnetic phase, which has a metallic character for one spin subband and an insulating character for the other subband (representing the so-called half-metallic state).
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : OVCHINNIKOV S.G.
Заглавие : THE INFLUENCE OF THE ANTIFERROMAGNETISM ON THE ELECTRONIC-STRUCTURE OF LA2CUO4
Разночтения заглавия :авие SCOPUS: The influence of the antiferromagnetism on the electronic structure of La2CuO4
Место публикации : J. Supercond.: PLENUM PUBL CORP, 1995. - Vol. 8: University-of-Miami Workshop on High-Temperature Superconductivity - Physical Properties and Mechanisms (JAN 05-11, 1995, CORAL GABLES, FL), Is. 5. - P675-676. - ISSN 0896-1107, DOI 10.1007/BF00727473
Примечания : Cited References: 15
Предметные рубрики: OXIDES
MODEL
Ключевые слова (''Своб.индексиров.''): electron correlations--electron structure--spin fluctuations--electron correlations--electron structure--spin fluctuations--antiferromagnetism--band structure--calculations--correlation theory--electrons--lanthanum compounds--paramagnetism--perturbation techniques--antiferromagnetic phase--electron correlations--intercluster interactions--spin fluctuations--electronic structure
Аннотация: The quasiparticle approach for electronic structure calculations considering strong electron correlations is given. The exact diagonalization of a multiband Hubbard Hamiltonian for a small cluster is combined with perturbation theory for intercluster hopping. The band structure of paramagnetic and antiferromagnetic La2CuO4 are discussed.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Petrakovsky G. A.
Заглавие : Quasi-particle spectrum in copper oxides
Разночтения заглавия :авие SCOPUS: Quasiparticle spectrum in copper oxides
Место публикации : J. Supercond. - 1991. - Vol. 4, Is. 6. - P.437-448. - ISSN 0896-1107, DOI 10.1007/BF00635862
Примечания : Cited References: 0
Ключевые слова (''Своб.индексиров.''): electron correlations--electron energy structure--copper oxide--photoemission data--copper oxide--electron correlations--electron energy structure--photoemission data--ceramic materials--lanthanum compounds--fermi liquid--lanthanum strontium copper oxides--oxide superconductors--quasi particles--high temperature superconductors
Аннотация: The results of electronic structure calculations of the CuO2 layer, performed by the generalized tight-binding method, are presented. The strong electron correlations on both the Cu and O ions are included explicitly. The resulting quasiparticle band structure contains an insulator gap for undoped compounds like La2CuO4. The valence band consists of a large number of narrow Hubbard quasiparticle bands. The dispersion law of quasiparticles at the top of the valence band has a minimum at the GAMMA-point, indicating the existence of the multivalley Fermi surface in the doped La2-xSrxCuO4. The origin of the Fermi liquid behavior in the narrow quasiparticle bands is discussed.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Lee C. G., Kim P. D., Eremin E. V., Patrin G. S.
Заглавие : Optically driven conductivity and magnetoresistance in a manganite-based tunnel structure
Коллективы : Russian Foundation for Basic Research [08-02-00259-a, 08-02-00397-a]; Division of Physical Sciences of the RAS; [2.4.2]
Место публикации : J. Phys. D. - 2009. - Vol. 42, Is. 20. - Ст.205009. - ISSN 0022-3727, DOI 10.1088/0022-3727/42/20/205009
Примечания : Cited References: 13. - This study was supported by the Russian Foundation for Basic Research (Projects Nos 08-02-00259-a and 08-02-00397-a) and the Division of Physical Sciences of the RAS, Programme 'Spin-dependent Effects in Solids and Spintronics' (Project No 2.4.2 of the Siberian Branch of the RAS).
Предметные рубрики: JUNCTIONS
Ключевые слова (''Своб.индексиров.''): conducting layers--current-in-plane geometry--dielectric layer--electron hole pairs--interband absorption--magnetic tunnel junction--magnetic tunnels--multilayer structures--optical radiations--photoinduced change--potential barriers--radiation power density--threshold characters--tunnel structures--electric resistance--lanthanum--light--magnetic field effects--magnetoelectronics--magnetoresistance--manganese compounds--oxide minerals--photovoltaic effects--semiconductor junctions--transport properties--vehicular tunnels--wind tunnels--tunnel junctions
Аннотация: In the multilayer structure, La(0.7)Sr(0.3)MnO(3)/depleted manganite layer/MnSi, the photovoltaic effect has been discovered. The depleted manganite layer in the structure is dielectric and serves as a potential barrier between the ferromagnetic conducting La(0.7)Sr(0.3)MnO(3) and MnSi layers by the formation of a magnetic tunnel junction. The photoinduced changes in the transport properties of the magnetic tunnel structure have been observed in the current-in-plane geometry. The changes are reversible and saturate at radiation power densities over 30 mW cm(-2). The photovoltaic effect has a threshold character: it reveals only at h nu 1.17 eV. Most likely, the effect of optical radiation is related to the formation of electron-hole pairs due to interband absorption of light in the dielectric layer. A photocurrent through the tunnel junctions separating the conducting layers causes a redistribution of the current channels between the conducting layers, which influences the conductivity and the magnetoresistance of the structure.
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