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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pparshin A. S., Chistyakov N. S.
Заглавие : Spin-wave resonance in thin monocrystalline iron-manganese ferrite films
Место публикации : Phys. Status Solidi B. - 1982. - Vol. 112, Is. 2. - P.K89-K92. - ISSN 0370-1972, DOI 10.1002/pssb.2221120249
Примечания : Cited References: 7
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Parshin A. S., Chistyakov N. S.
Заглавие : Effect of a magnetization inhomogeneity on spin-wave resonance-spectra of monocrystalline films of iron-manganese spinel
Место публикации : Izv. Vysshikh Uchebnykh Zavedenii Fizika. - 1983. - Vol. 26, Is. 11. - P.26-29. - ISSN 0021-3411; \b Russian Physics Journal; \b Известия высших учебных заведений. Физика
Примечания : Cited References: 10
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popov E. A., Kotlyarskii M. M., Edelman I. S.
Заглавие : Temperature and field dependence of exciton-magnon absorption of NaMnCl//3.
Место публикации : Physica Status Solidi B - Basic Research. - 1985. - Vol. 132, Is. 2. - P.465-470. - ISSN 0370-1972
Ключевые слова (''Своб.индексиров.''): band structure--light - absorption--sodium compounds - optical properties--exciton-magnon absorption--sodium manganese chloride--magnetic materials
Аннотация: The behaviour of the optical absorption bands of NaMnCl//3 is experimentally studied in the region of the **6A//1//g to **4A//1//g, **4E//g(**4G) transition of the Mn**2** plus ion in the temperature range 1. 8 to 20 K and in magnetic fields up to 20 T. Exciton and its 'hot' magnon sidebands are observed in the spectrum. The anomalous temperature dependence of the exciton-magnon bands intensity is explained by participation of magnons with wave vector K does not equal 0 in absorption. The low energy exciton-magnon band is supposed to be due to simultaneous creation of an exciton and annihilation of three thermally created magnons.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ivanova N. B., Ovchinnikov S. G., Balaev A. D., Aminov T. G., Shabunina G. G., Chernov V. K., Petukhov M. V.
Заглавие : Comparison of negative magnetoresistance mechanisms in manganese perovskites and chromium spinels
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1999. - Vol. 41, Is. 10. - P1652-1655. - ISSN 1063-7834, DOI 10.1134/1.1131064
Примечания : Cited References: 17
Предметные рубрики: ANISOTROPIC MAGNETORESISTANCE
TRANSPORT-PROPERTIES
THIN-FILMS
ALLOYS
Аннотация: A transition of the field dependence of the electrical resistivity from a square law (similar to H-2) above T-c to a linear function (similar to H) below T-c is observed in the degenerate ferromagnetic semiconductor HgCr2Se4(n). Together with the large negative magnetoresistance, these magnetoelectric effects correspond to effects observed in the perovskite-type oxides La1-xCaxMnOdelta. Inasmuch as the undoped semiconductor HgCr2Se4 is a ferromagnet with approximately the same critical temperature as the doped semiconductor and in view of the total lack of data on the Jahn-Teller effect in this compound, we infer that our results cast doubt on existing hypotheses (polaron and binary exchange) regarding the origin of the giant magnetoresistance in La1-xCaxMnOdelta. Impurity sd scattering is discussed as a possible magnetoresistance mechanism for both compounds. (C) 1999 American Institute of Physics. [S1063-7834(99)01710-4].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : An impurity resistivity of doped manganese perovskites
Место публикации : Physica B: ELSEVIER SCIENCE BV, 1999. - Vol. 259-61: International Conference on Strongly Correlated Electron Systems (SCES 98) (JUL 15-18, 1998, PARIS, FRANCE). - P828-830. - ISSN 0921-4526, DOI 10.1016/S0921-4526(98)00875-8
Примечания : Cited References: 4
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): manganese perovskites--mobility--linear and quadratic magnetoresistance
Аннотация: We present a two-time of relaxation approach at an analysis of a magnetoresistance in ferromagnetic manganese perovskites La(1-x)(Ca,Sr)(x)MnO. To explain a change in the low-held response from predominantly quadratic dR/dH\(H--0) = 0 for T T(c) to linear dR/dH\(H--0) for T T(c) as noted in the measurements in thin films La(0.7)Ca(0.3)MnO(3) we calculated held and temperature dependences of a impurity contribution to a carrier mobility in a framework of the 2p(O)- and 3d(Mn)-scattering model elaborated for manganese perovskites. We obtained the field-dependent impurity contribution to the overall scattering of carriers that show a transition in the low-field (H) dependence of R from quadratic above T(c) to linear below consistent with an experiment. The calculated negative magnetoresistance ratio is sharply peaked at a temperature-near T(c) or below. (C) 1999 Elsevier Science B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Loseva G. V., Ovchinnikov S. G., Balaev A. D., Kiselev N. I.
Заглавие : Metal-dielectric transitions, magnetism, and electronic structure in a system of manganese-doped vanadium sulfides
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2000. - Vol. 42, Is. 3. - P539-543. - ISSN 1063-7834, DOI 10.1134/1.1131245
Примечания : Cited References: 12
Предметные рубрики: TRANSPORT
Аннотация: The effect of the manganese doping of vanadium monosulfide in a system of the V1-xMnxS (0 x less than or equal to 0.3) solid solutions on their structure and thermal, electrical, and magnetic properties has been investigated. The metal-dielectric transitions are revealed in the studied ranges of concentrations and temperatures. These transitions are accompanied by a change in the magnetic properties. It is demonstrated that the correlation in changes of the electrical and magnetic properties of the sulfides under investigation is characteristic of the metal-dielectric transitions in strongly correlated systems. (C) 2000 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrakovskii G. A., Ryabinkina L. I., Abramova G. M., Velikanov D. A., Bovina A. F.
Заглавие : Antiferromagnet-ferromagnet transition in alpha-MnxS manganese sulfides
Разночтения заглавия :авие SCOPUS: Antiferromagnet-ferromagnet transition in α-MnxS manganese sulfides; авие SCOPUS: Antiferromagnet-ferromagnet transition in ?-MnxS manganese sulfides
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2001. - Vol. 43, Is. 3. - P493-495. - ISSN 1063-7834, DOI 10.1134/1.1356126; Phys. Solid State. - 2001. - Vol. 43, Is. 3. - P493-495. - Вариант Sopus
Примечания : Cited References: 7
Аннотация: Off-stoichiometric manganese monosulfides alpha -MnxS (1 less than or equal to x less than or equal to 1.25) are synthesized, and their crystal structure and magnetic properties are studied in the 4.2- to 300-K range. The compounds have a NaCl fcc lattice. Increasing the manganese ion concentration x in the antiferromagnetic semiconductors alpha -MnxS is found to result in concentration- (x(c) similar to 1.05) and temperature-driven (T-c similar to 50 K) magnetic transitions from the antiferromagnetic to ferromagnetic state, with the cubic structure remaining unchanged. (C) 2001 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Petrakovskii G. A., Ryabinkina L. I., Abramova G. M., Kiselev N. I., Romanova O. B.
Заглавие : Influence of magnetic ordering on the resistivity anisotropy of alpha-MnS single crystal
Разночтения заглавия :авие SCOPUS: Influence of magnetic ordering on the resistivity anisotropy of α-MnS single crystal; авие SCOPUS: Influence of magnetic ordering on the resistivity anisotropy of ?-MnS single crystal
Место публикации : Solid State Commun.: PERGAMON-ELSEVIER SCIENCE LTD, 2004. - Vol. 129, Is. 3. - P195-197. - ISSN 0038-1098, DOI 10.1016/j.ssc.2003.09.028; Solid State Commun. - 2004. - Vol. 129, Is. 3. - P195-197. - Вариант Sopus
Примечания : Cited References: 7
Ключевые слова (''Своб.индексиров.''): anisotropy of resistivity--optical gap--d. anisotropy of resistivity--d. optical gap--antiferromagnetism--band structure--bandwidth--diffractometers--electron transitions--fermi level--hamiltonians--light absorption--magnetic anisotropy--magnetization--single crystals--spectroscopic analysis--x ray diffraction analysis--coulomb repulsion--resistivity anisotropy--semiconducting manganese compounds--d. anisotropy of resistivity--d. optical gap--antiferromagnetism--band structure--bandwidth--diffractometers--electron transitions--fermi level--hamiltonians--light absorption--magnetic anisotropy--magnetization--single crystals--spectroscopic analysis--x ray diffraction analysis--coulomb repulsion--resistivity anisotropy--semiconducting manganese compounds
Аннотация: The resistivity and the optical absorbtion spectra of single crystal alpha-MnS are studied in the temperature range 80-300 K along two directions [100] and [111]. Strong anisotropy of the resistivity, and the shift of absorbtion spectra band edge below T 160 K are explained in terms of model involving delocalized holes in 3d-band manganese ions interacting with localized spins by using the sd-model. (C) 2003 Elsevier Ltd. All rights reserved.
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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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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasilyeva I. G., Dovlitova L. S., Zaikovskii V. I., Malakhov V. V., Edel'man I. S., Stepanov A. S., Aleksandrov K. S.
Заглавие : Actual composition and structure of manganese ferrite nanoparticles dispersed in the borate glass matrix
Место публикации : Doklady Chemistry. - 2005. - Vol. 401, Is. 1-3. - P.47-50. - ISSN 0012-5008, DOI 10.1007/s10631-005-0029-y
Ключевые слова (''Своб.индексиров.''): boric acid--ferrite--glass--manganese derivative--analytic method--article--chemical composition--chemical structure--nanoparticle--stoichiometry--structure analysis--transmission electron microscopy--x ray analysis
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasil'eva I. G., Dovlitova L. S., Zajkovskij V. I., Malakhov V. V., Edel'man I. S., Stepanov A. S., Aleksandrov K. S.
Заглавие : Real composition and structure of manganese ferrite nanoparticles dispersed in the K-Al-B-O glasses
Место публикации : Dokl. Akad. Nauk. - 2005. - Vol. 401, Is. 3. - P.349-352. - ISSN 0869-5652
Ключевые слова (''Своб.индексиров.''): aluminum--boron compounds--ferrite--manganese--nanostructured materials--particles (particulate matter)--structure (composition)--borate glasses--exchange interaction--glass
Аннотация: For the first time the problem of determining real composition and structure of manganese ferrite nanoparticles dispersed borate glasses is solved using differentiating dissolution and high-resolution X-ray electron microscopy techniques. For the first time the nanosize effect of aluminum incorporation in manganese ferrite composition is experimentally shown, thus directly confirming the hypothesis of Al participation in exchange interaction between paramagnetic Fe and Mn ions as diamagnetic diluter.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Ryabinkina L. I., Abramova G. M., Romanova O. B., Vorotynov A. M., Velikanov D. A., Kiselev N. I., Balaev A. D.
Заглавие : Conductivity, weak ferromagnetism, and charge instability in an alpha-MnS single crystal
Разночтения заглавия :авие SCOPUS: Conductivity, weak ferromagnetism, and charge instability in an α-MnS single crystal; авие SCOPUS: Conductivity, weak ferromagnetism, and charge instability in an ?-MnS single crystal
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2005. - Vol. 71, Is. 12. - Ст.125204. - ISSN 1098-0121, DOI 10.1103/PhysRevB.71.125204; Phys. Rev. B Condens. Matter Mater. Phys. - 2005. - Vol. 71, Is. 12. - Ст.125204. - Вариант Sopus
Примечания : Cited References: 11
Предметные рубрики: MANGANITES
Ключевые слова (''Своб.индексиров.''): ferromagnetic material--manganese derivative--absorption spectroscopy--article--calculation--conductance--crystal--electron spin resonance--hybridization--magnetic field--magnetism--measurement--molecular interaction--temperature dependence--temperature measurement--ferromagnetic material--manganese derivative--absorption spectroscopy--article--calculation--conductance--crystal--electron spin resonance--hybridization--magnetic field--magnetism--measurement--molecular interaction--temperature dependence--temperature measurement
Аннотация: The temperature dependence of resistivity, magnetization, and electron-spin resonance of the α-MnS single crystal were measured in temperature range of 5 K T 550 K. Magnetization hysteresis in an applied magnetic field up to 0.7 T at T
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrovsky A. S., Gudim I. A., Krylov A. S., Temerov V. L.
Заглавие : Luminescence of yttrium aluminum borate single crystals doped with manganese
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 9. - P1695-1699. - ISSN 1063-7834, DOI 10.1134/S1063783407090156
Примечания : Cited References: 10
Аннотация: The optical absorption and luminescence spectra of single crystals of yttrium aluminum borate YAl3(BO3)(4) doped with manganese ions are measured. It is established that the optical absorption spectra of yttrium aluminum borate single crystals doped with manganese ions are determined primarily by the contribution from the Mn4+ ions. The luminescence spectra of the YAl3(BO3)(4) single crystals doped with manganese exhibit narrow lines attributed to the Mn4+ ions and an extended multiband structure which is associated primarily with the contribution from the Mn2+ ions.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulina N. V., Petrakovskaya E. A., Fedorov A. S., Churilov G. N.
Заглавие : Synthesis and study of manganese-containing endohedral fullerenes
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 3. - P599-602. - ISSN 1063-7834, DOI 10.1134/S1063783407030377
Примечания : Cited References: 15
Предметные рубрики: PLASMA
STATE
C-60
Аннотация: Fullerenes containing manganese and iron atoms are synthesized in a high-frequency carbon-helium plasma at atmospheric pressure. The electron paramagnetic resonance (EPR) spectrum of the synthesized compound contains not only lines attributed to iron atoms but also the lines of a manganese ion pair with an additional hyperfine structure. The latter lines are assigned to the endohedral complex Mn-2@C-n (n 70). The possible existence of these structures is evaluated from quantum-chemical calculations of the optimum geometry of the endohedral fullerene Mn-2@C-84 with C-2V symmetry. It is found that the manganese atoms are spaced similar to 2.72 angstrom apart at the center of the molecule.
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15.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Volkov N. V., Sablina K. A., Bayukov O. A., Eremin E. V., Velikanov D. A., Bovina A. F., Petrakovskii G. A., Boni P.
Заглавие : Mixed-valence manganese oxide Pb3Mn7O15: structure, magnetic and dielectric properties
Коллективы : "Актуальные проблемы физики твердого тела", Международная научная конференция, Национальная академия наук Беларуси, Научно-практический центр НАН Беларуси по материаловедению, Белорусский республиканский фонд фундаментальных исследований
Место публикации : Актуальные проблемы физики твердого тела (ФТТ-2007): сб. докл. Междунар. науч. конф., 23-26 октября 2009 г., Минск : [в 3-х т.]. - 2007. - Т. 3. - P.301-302
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16.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Volkov N. V., Petrakovskiy G. A., Sablina K. A., Bayukov O. A., Eremin E. V., Velikanov D. A., Balaev A. D., Vasiliev A. D., Bovina A. F., Böni P., Clementyev E.
Заглавие : Mixed-valence manganese oxide Pb3Mn7O15: structure, magnetic and dielectric properties
Коллективы : "New Layered 3d-Materials for Spintronics", Workshop INTAS - Siberian Branch of the Russian Academy of Sciences Scientific Cooperation on the Research Project, Институт физики им. Л.В. Киренского Сибирского отделения РАН, ETH Zurich and Paul Scherrer Institute, Condensed Matter Research with Neutron and Muons Department, Institute of Physics of Polish Academy of Sciences, Институт неорганической химии им. А.В.Николаева СО РАН
Место публикации : Workshop INTAS - Siberian Branch of the Russian Academy of Sciences Scientific Cooperation on the Research Project "New Layered 3d-Materials for Spintronics": (books of abstrats) : March 20-23, 2007 Krasnoyarsk, Russia/ Институт физики им. Л.В. Киренского СО РАН. - Красноярск, 2007. - P.7
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17.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Volkov N. V., Petrakovskii G. A., Sablina K. A., Bayukov O. A., Eremin E. V., Velikanov D. A., Balaev A. D., Vasiliev A. D., Bovina A. F., Böni P., Clementyev E.
Заглавие : Mixed-valence manganese oxide Pb3Mn7O15: structure, magnetic and dielectric properties
Коллективы : "New Layered 3d-Materials for Spintronics", Workshop INTAS - Siberian Branch of the Russian Academy of Sciences Scientific Cooperation on the Research Project
Место публикации : Workshop INTAS - Sib. Branch of the RAS Sci. Cooperation on the Res. Project “New Layered 3d-Materials for Spintronics”/ chairman G. A. Petrakovskii. - 2007. - P.7
Аннотация: INTAS (The International Association for the Promotion of Cooperation with Scientists from the New Independent States of the Former Soviet Union) — международная ассоциация по содействию сотрудничеству с учёными новых независимых государств бывшего Советского Союза. Некоммерческая организация, финансировалась главным образом из бюджета Европейского Союза. Являлась крупнейшим фондом, поддерживающим научное сотрудничество между учёными стран бывшего СССР и Европейского Союза с 1993 г. Программы INTAS охватывали широкий круг научно-исследовательских проблем. 22 сентября 2006 года было принято решение о прекращении осуществления программы на основании рекомендации Европейской Комиссии. С 1 апреля 2007 года прекратилось распределение новых грантов.
Материалы семинара,
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Sablina K. A., Bayukov O. A., Eremin E. V., Petrakovskii G. A., Velikanov D. A., Balaev A. D., Bovina A. F., Boni P., Clementyev E.
Заглавие : Magnetic properties of the mixed-valence manganese oxide Pb(3)Mn(7)O(15)
Разночтения заглавия :авие SCOPUS: Magnetic properties of the mixed-valence manganese oxide Pb 3Mn7O15
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2008. - Vol. 20, Is. 5. - Ст.55217. - ISSN 0953-8984, DOI 10.1088/0953-8984/20/5/055217
Примечания : Cited References: 16
Предметные рубрики: CRYSTAL-STRUCTURE
PHASE-SEPARATION
Ключевые слова (''Своб.индексиров.''): crystal structure--magnetization--manganese compounds--phase interfaces--x ray diffraction--manganese oxide--space groups--temperature range--single crystals
Аннотация: A Pb(3)Mn(7)O(15) single crystal has been grown by the flux method and studied using x-ray diffraction and magnetization measurements. The crystal is hexagonal (P6(3)/mcm space group, Z = 4) and exhibits a pronounced layered nature. Along the [001] direction (c axis), the structure consists of layers of edge-sharing MnO(6) octahedra. Pairs of Mn atoms occupy the octahedral sites located between layers forming 'bridges' along the c axis, which link neighboring Mn layers. The magnetic properties of the crystal have been investigated using ac and dc magnetization measurements in the temperature range 2-900 K at magnetic fields up to 90 kOe. The experimental data obtained suggest that in the temperature region under study several different magnetic phases can be distinguished. Down to similar to 250 K, the crystal is in the paramagnetic state. Below this temperature, short-range antiferromagnetic ordering apparently starts forming within Mn layers, although a transition to long-range magnetic order occurs at 70 K. The magnetization data obtained leads us to conclude that this state is canted antiferromagnetic with moments lying in the basal plane of the crystal. In addition, below 20 K the crystal undergoes one more magnetic transition that corresponds to spin reorientation.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Sablina K. A., Eremin E. V., Boni P., Shah V. R., Flerov I. N., Kartashev A., Rasch JCE, Boehm M., Schefer J.
Заглавие : Heat capacity of a mixed-valence manganese oxide Pb(3)Mn(7)O(15)
Коллективы :
Разночтения заглавия :авие SCOPUS: Heat capacity of a mixed-valence manganese oxide Pb3Mn 7O15
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2008. - Vol. 20, Is. 44. - Ст.445214. - ISSN 0953-8984, DOI 10.1088/0953-8984/20/44/445214
Примечания : Cited References: 11. - This study was supported by the INTAS (project No 061000013-9002), the Division of Physical Sciences of RAS, program `Spin-dependent Effects in Solids and Spintronics' (project No. 2.4.2 of SB RAS), the President of the Russian Federation, grant for Support of Leading Scientific Schools (project No. NSh-1011.2008.2), KRSF-RFBR `Enisey2007', project No. 07-02-96801-a, and the Siberian Branch of RAS, Integration project No. 3.7.
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--crystallography--entropy--lead alloys--magnetic materials--magnetism--manganese--manganese compounds--powders--single crystals--specific heat--spin dynamics--antiferromagnetic orders--charge localizations--entropy losses--excess heat capacities--experimental datums--heat capacities--magnetic contributions--magnetic orders--magnetic states--magnetic subsystems--magnetic transitions--manganese oxides--nonmagnetic--spin systems--temperature curves--temperature dependences--temperature intervals--temperature ranges--manganese alloys
Аннотация: We present the results of a heat capacity study of Pb(3)Mn(7)O(15) single crystals with approximately equal concentrations of Mn(3+) and Mn(4+) ions. In the temperature interval between 210 and 260 K, an excess heat capacity of nonmagnetic origin, most likely associated with the process of charge localization, has been observed. Also, three pronounced anomalies corresponding to the changes in a magnetic subsystem of the crystal have been observed in the temperature dependence of the heat capacity. A broad hump near 150 K is related to the formation of a short-range magnetic order. This process of short-range ordering is rather prominent, considering the appreciable value of the entropy loss accompanying the change in the magnetic state. A clear lambda-shaped peak at 70 K marks the onset of a long-range antiferromagnetic order. Another anomalous contribution to the heat capacity of magnetic origin has been revealed at temperatures below 20 K. This contribution is associated with a magnetic transition of an unknown nature, which is also clearly evident in magnetization versus temperature curves. The total magnetic contribution to the entropy deduced from the actual experimental data over the entire temperature range is much smaller than is expected for a completely ordered Mn spin system in the crystal. We suggest several possible reasons that may account for this `missing' entropy.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kliava J., Edelman I. S., Ivanova O. S., Ivantsov R. D., Bayukov O. A., Petrakovskaja E. A., Zaikovskiy V., Bruckental I., Yeshurun Y., Stepanov S.
Заглавие : Formation and evolution of magnetic nanoparticles in borate glass simultaneously doped with Fe and Mn oxides
Коллективы :
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2008. - Vol. 104, Is. 10. - Ст.103917. - ISSN 0021-8979, DOI 10.1063/1.3021289
Примечания : Cited References: 37. - A financial support from the Russian Foundation for Basic Research (RFBR)-CNRS (Grant No. 07-02-92174) is highly appreciated. R. Ivantsov is grateful to the Russian Science Support Foundation. Y. Yeshurun acknowledges the support of the Israel Scienc Foundation (ISF).
Предметные рубрики: COBALT FERRITE PARTICLES
SUPERPARAMAGNETIC RESONANCE
GAMMA-FE2O3 NANOPARTICLES
MATRIX
SIZE
SYSTEMS
Ключевые слова (''Своб.индексиров.''): aluminium compounds--borate glasses--coercive force--faraday effect--heat treatment--iron compounds--magnetic hysteresis--magnetic particles--magnetic susceptibility--manganese compounds--mossbauer effect--nanoparticles--paramagnetic materials--potassium compounds--remanence--superparamagnetism--transmission electron microscopy--x-ray chemical analysis--atomic spectroscopy--auger electron spectroscopy--crystal structure--electric relays--electronic medical equipment--ferrite--ferrites--glass--heat treatment--hysteresis--hysteresis loops--magnetic properties--magnetic resonance measurement--magnetic susceptibility--magnetism--manganese--manganese compounds--molybdenum--nanoparticles--optical properties--ozone water treatment--polydispersity--superparamagnetism--borate glasses--concentration ratios--electron magnetic resonances--emr spectrums--experimental techniques--faraday rotations--glass compositions--glass matrixes--glass preparations--magnetic measurements--magnetic nano particles--magnetic orders--magnetically ordered systems--magneto-optical properties--manganese ferrites--mean diameters--mn oxides--phase states--polydisperse nanoparticles--remnant magnetizations--ssbauer spectroscopies--superparamagnetic--superparamagnetic states--thermal treatments--variable temperatures--magnetic materials
Аннотация: Evolution of the phase state of paramagnetic additions at various stages of synthesis and subsequent thermal treatment of glasses of the system Al(2)O(3)-K(2)O-B(2)O(3) simultaneously doped with Fe(2)O(3) and MnO is studied by means of a combination of experimental techniques: Faraday rotation (FR), electron magnetic resonance (EMR), transmission electron microscopy (TEM), Mossbauer spectroscopy, and magnetic measurements. Both FR and EMR show that magnetically ordered clusters occur already at the first stage of the glass preparation. In particular, for the ratio of the Fe and Mn oxides in the charge close to 3:2, fine magnetic nanoparticles are formed with characteristics similar to those of manganese ferrite. By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of these nanoparticles is confirmed and their mean diameter is estimated as approximately 3.2 nm. In the thermally treated glasses larger magnetic nanoparticles are formed, giving rise to FR spectra, characteristic of magnetically ordered systems, and the EMR spectra different from those in as-prepared glasses but also showing superparamagnetic narrowing. The Mossbauer spectroscopy corroborates the manganese ferrite structure of the nanoparticles and indicates their coexistence in the ferrimagnetic and superparamagnetic states. The TEM shows the presence of polydisperse nanoparticles on the background of the glass matrix, and electron diffraction of a selected region containing larger particles indicates a crystal structure close to that of MnFe(2)O(4). Energy-dispersive atomic x-ray spectra confirm that the major part of Fe and Mn introduced to the glass composition is gathered in the particles, with the concentration ratio close to 2:1, characteristic of bulk MnFe(2)O(4). Magnetic hysteresis loops of samples subjected to an additional thermal treatment demonstrate a strong increase in the coercive force, remnant magnetization, and high-field magnetic susceptibility with temperature decrease. The consistent results obtained using various techniques demonstrate that the formation of nanoparticles with characteristics close to those of MnFe(2)O(4) confers to these glasses magnetic and magneto-optical properties typical of substances possessing magnetic order.
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