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1.


    Valkov, V. V.
    Application of indefinite metric for transition to bose description of Su(3) hamiltonians - excitation spectrum of spin nematics / V. V. Valkov, T. A. Valkova // Zhurnal Eksperimentalnoi Teor. Fiz. - 1991. - Vol. 99, Is. 6. - P. 1881-1897. - Cited References: 37 . - ISSN 0044-4510
РУБ Physics, Multidisciplinary
Рубрики:
BIQUADRATIC EXCHANGE
   PHASE-TRANSITIONS

   DIAGRAM TECHNIQUE

   MAGNETISM

   FIELD

   STATE

Аннотация: A procedure is developed for a correct transition to the Bose representation for quantum SU(3) Hamiltonians. The analysis is carried out for a spin nematic by applying the indefinite metric formalism and pseudo-Hubbard operators. An important aspect of the theory is that the finiteness of the number of physical states is taken into account. This is attained by introducing and consistently taking into account the metric operator for which purpose a simple expression in terms of Bose operators is suggested. It is shown that in this approach the quantum Bose analog of the Hamiltonian is an Hermitian operator. This circumstance removes a number of principle contradictions which appeared previously on application of the Bose analog of the Hamiltonian derived by virtually identifying the Hubbard and pseudo-Hubbard operators and ignoring the finiteness of the number of physical states. The integral equations defining the chief characteristics of the system are obtained and solved analytically for the spin-nematic state of a magnet with S = 1 and by taking into account anharmonic effects. This permits one to write down in nonlinear theory explicit expressions for the two branches of the quantum excitation spectrum. The character of the renormalization of the spectrum parameters due to the presence of zero-point quantum oscillations is studied. The renormalization of the critical field on transition of the system from the spin nematic state is calculated analytically.

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Доп.точки доступа:
Valkova, T. A.; Вальков, Валерий Владимирович
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2.


    GEKHT, R. S.
    MAGNETIC-STRUCTURES AND PROPERTIES OF STATES IN STRONGLY FRUSTRATED HEISENBERG ANTIFERROMAGNETS / R. S. GEKHT // Zhurnal Eksperimentalnoi Teor. Fiz. - 1992. - Vol. 102, Is. 6. - P. 1968-1982. - Cited References: 23 . - ISSN 0044-4510
РУБ Physics, Multidisciplinary
Рубрики:
PHASE-TRANSITIONS
   SPIN

   LATTICE

   MODELS

   LONG

Аннотация: The magnetic structures and properties of states in frustrated Heisenberg antiferromagnets are analyzed. It is shown that frustrations induced due to additional spins in the system lead to a large variety of phase with the commensurable and uncommensurable periods and also to arising nonperiodical phases. The energy spectrum of states is studied. It is found that in the large region of the frustration parameter variation the modulated phase (0, Q) is unstable. The phase diagram of states is found and the region of local degeneration for some structures is indicated.

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3.


    GEKHT, R. S.
    ON MAGNETIC STATES IN STRONGLY FRUSTRATED 2-DIMENSIONAL ANTIFERROMAGNETICS / R. S. GEKHT, V. V. GRISHIN // Fiz. Tverd. Tela. - 1992. - Vol. 34, Is. 11. - P. 3557-3559. - Cited References: 5 . - ISSN 0367-3294
РУБ Physics, Condensed Matter
Рубрики:
PHASE-TRANSITIONS
   LATTICE


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Держатели документа:
LV KIRENSKII INST PHYS,KRASNOYARSK,RUSSIA
ИФ СО РАН

Доп.точки доступа:
GRISHIN, V. V.
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4.


    GEKHT, R. S.
    LOW-TEMPERATURE PROPERTIES OF QUASI-2-DIMENSIONAL FRUSTRATED ANTI-FERROMAGNETICS / R. S. GEKHT, V. I. PONOMAREV // Fiz. Tverd. Tela. - 1994. - Vol. 36, Is. 11. - P. 3394-3397. - Cited References: 8 . - ISSN 0367-3294
РУБ Physics, Condensed Matter
Рубрики:
PHASE-TRANSITIONS
   MAGNETIC STATES

   ANTIFERROMAGNETS


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Доп.точки доступа:
PONOMAREV, V. I.
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5.


   
    Study of molecular mobility in ABF6-center-dot-6H2O crystal family / E. P. Zeer, O. V. Falaleev, Y. N. Ivanov, E. A. Petrakovskaya // Fiz. Tverd. Tela. - 1994. - Vol. 36, Is. 8. - P. 2210-2220. - Cited References: 21 . - ISSN 0367-3294
РУБ Physics, Condensed Matter
Рубрики:
PHASE-TRANSITIONS
   NMR

   SYSTEM


WOS

Доп.точки доступа:
Zeer, E. P.; Зеер, Эвальд Петрович; Falaleev, O. V.; Фалалеев, Олег Владимирович; Ivanov, Y. N.; Иванов, Юрий Николаевич; Petrakovskaya, E. A.; Петраковская, Элеонора Анатольевна
}
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6.


    Gekht, R. S.
    Helicoidal magnetic structure in frustrated antiferromagnetics / R. S. Gekht, A. M. Epikhin, V. I. Ponomarev // Fiz. Tverd. Tela. - 1995. - Vol. 37, Is. 6. - P. 1891-1893. - Cited References: 6 . - ISSN 0367-3294
РУБ Physics, Condensed Matter
Рубрики:
QUANTUM FLUCTUATIONS
   PHASE-TRANSITIONS


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Доп.точки доступа:
Epikhin, A. M.; Ponomarev, V. I.
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7.


   
    Chemical exchange in NH4HSeO4 single crystals studied by two-dimensional H-2 nuclear magnetic resonance / Y. N. Ivanov [et al.] // J. Phys.: Condens. Matter. - 1999. - Vol. 11, Is. 18. - P. 3751-3760, DOI 10.1088/0953-8984/11/18/310. - Cited References: 16 . - ISSN 0953-8984
РУБ Physics, Condensed Matter
Рубрики:
PHASE-TRANSITIONS
   CONDUCTIVITY PROCESSES

   AMMONIUM

Кл.слова (ненормированные):
Hydrogen bonds -- Nuclear magnetic resonance -- Single crystals -- Thermal effects -- Ammonium hydrogen selenate -- Ammonium compounds
Аннотация: Processes of chemical exchange of deuterons in partially deuterated ammonium hydrogen selenate, NH4HSeO4 (AHSe), crystals are investigated by means of H-2 nuclear magnetic resonance (NMR) experiments over a wide temperature range. The temperature dependencies of the quadrupole line splittings in the one-dimensional spectra of AHSe above 350 K revealed lineshape changes which are characteristic for chemical exchange processes. A detailed study of these exchange processes in AHSe is achieved by means of two-dimensional H-2 NMR experiments. In the temperature range investigated, a chemical exchange occurs only between those deuteron (proton) sites which are involved in hydrogen bonds (alpha- and beta-positions). It was established that the rates of exchange between all types of hydrogen-bound deuteron are approximately the same. Exchange between these positions and the deuterons in the ND4 groups could not be detected. On the basis of our findings, we finally discuss a model for the microscopic mechanism of hydrogen transport in AHSe.

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Держатели документа:
LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
Univ Leipzig, Fak Phys & Geowissensch, D-04103 Leipzig, Germany
ИФ СО РАН
L V Kirensky Institute of Physics, Russian Academy of Science, Siberian Branch, 660036 Krasnoyarsk, Russian Federation
Universitat Leipzig, Fakultat fur Physik und Geowissenschaften, Linnestra?e 5, D-04103 Leipzig, Germany

Доп.точки доступа:
Ivanov, Y. N.; Иванов, Юрий Николаевич; Totz, J.; Michel, D.; Klotzsche, G.; Sukhovsky, A. A.; Суховский, Андрей Андреевич; Aleksandrova, I. P.; Александрова, Инга Петровна
}
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8.


    Ovchinnikov, S. G.
    Application of synchrotron radiation to the study of magnetic materials / S. G. Ovchinnikov // Uspekhi Fiz. Nauk. - 1999. - Vol. 169, Is. 8. - P. 869-887. - Cited References: 93 . - ISSN 0042-1294
РУБ Physics, Multidisciplinary
Рубрики:
X-RAY-SCATTERING
   RESONANCE EXCHANGE SCATTERING

   RARE-EARTH-METALS

   CIRCULAR-DICHROISM

   VALENCE STATES

   CO/PD(111) MULTILAYERS

   ABSORPTION-SPECTRA

   PHASE-TRANSITIONS

   SPIN POLARIZATION

   EDGE STRUCTURE

Аннотация: The recent results of the studies of magnetic materials using synchrotron irradiation are reviewed. The influence of magnetic effects on X-ray scattering is studied for linearly and circularly polarized photons, and effects of magnetic circular dichroism on the spectra of X-ray absorption and photoelectron emission are discussed. It is shown that X-ray magnetooptics techniques provide fine details of crystal and magnetic structures and also make it possible to separate the spin and orbital contributions to the total moment; to obtain element- and position-sensitive information on the magnetic properties of the material; to visualize domains and domain walls; and to probe magnetization reversal dynamics. A comparison of magnetic neutron and X-ray methods is given.

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Scopus
Держатели документа:
Russian Acad Sci, Siberian Div, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
ИФ СО РАН
L.V. Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation

Доп.точки доступа:
Овчинников, Сергей Геннадьевич
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9.


   
    Thermodynamic properties of (NH4)(2)KGaF6 elpasolite / I. N. Flerov [et al.] // Phys. Solid State. - 2001. - Vol. 43, Is. 12. - P. 2301-2306, DOI 10.1134/1.1427960. - Cited References: 19 . - ISSN 1063-7834
РУБ Physics, Condensed Matter
Рубрики:
NUCLEAR MAGNETIC-RESONANCE
   PHASE-TRANSITIONS

   CRYOLITE (NH4)(3)SCF6

   MOTIONS

   F-19

   H-1

Аннотация: The heat capacity of (NH4)(2)KGaF6 elpasolite is measured in the temperature range from 80 to 350 K. A sequence of three phase transitions at T-1 = 288.5 K, T-2 = 250 K, and T-3 = 244.5 K is revealed, and the thermodynamic characteristics of these transitions are determined. The influence of hydrostatic pressure on the phase transition temperature is investigated. The results obtained are discussed within the model of orientational ordering of NH4+ and GaF63- ionic groups. (C) 2001 MAIK "Nauka/Interperiodica".

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Gorev, M. V.; Горев, Михаил Васильевич; Afanas'ev, M. L.; Ushakova, T. V.
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10.


   
    Low-temperature specific heat of the Rb2KScF6 elpasolite / I. N. Flerov [et al.] // Phys. Solid State. - 2003. - Vol. 45, Is. 1. - P. 167-170, DOI 10.1134/1.1537430. - Cited References: 9 . - ISSN 1063-7834
РУБ Physics, Condensed Matter
Рубрики:
PHASE-TRANSITIONS
   CRYOLITE (NH4)(3)SCF6

   DISTORTED PHASES

   SYMMETRY

Аннотация: The specific heat of single-crystal Rb2KScF6 is measured using ac calorimetry in the range 4-280 K. The results are discussed in the context of a group-theoretical analysis of possible distortions of the elpasolite structure and of experimental data obtained earlier with an adiabatic calorimeter in a narrower temperature region. (C) 2003 MAIK "Nauka/Interperiodica".

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Держатели документа:
Russian Acad Sci, Siberian Div, Kirenskii Inst Phys, Krasnoyarsk 660036, Russia
Univ Zaragoza, CSIC, Inst Sci Mat Aragon, E-50009 Zaragoza, Spain
ИФ СО РАН
Kirenskii Inst. of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk 660036, Russian Federation
Inst. de Sciencia de Mat. de Aragon, CSIC, Universidad de Zaragoza, Zaragoza 50009, Spain

Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Burriel, R.; Gorev, M. V.; Горев, Михаил Васильевич; Isla, P.; Voronov, V. N.; Воронов, Владимир Николаевич
}
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