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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Flat and conical incommensurate magnetic structures in the two-subsystem partially frustrated Heisenberg ferrimagnet
Место публикации : J. Magn. Magn. Mater.: Elsevier, 2016. - Vol. 398. - P.121-126. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2015.09.046
Примечания : Cited References: 21
Предметные рубрики: Spin-wave spectrum
Phase 10 K
Copper metaborate
Classical-theory
State
Ключевые слова (''Своб.индексиров.''): incommensurate magnetic structures--phase transitions--ferrimagnets
Аннотация: The phase transitions into flat and conical incommensurate magnetic structures are considered for a ferrimagnet with the dominant nonfrustrated exchange between the spins in one crystallographic position, competing exchanges between the spins in another position and frustrated exchange between the spins in different positions. The appearance conditions and the temperatures of the second order phase transitions are analytically obtained in the mean field approximation. The first order phase transition between these states is studied and the phase diagrams of temperature vs frustrated exchanges are calculated by the numerical minimization of free energy.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Phase diagram of the helical structure of a two-subsystem frustrated antiferromagnet
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2009. - Vol. 108, Is. 1. - P72-82. - ISSN 1063-7761, DOI 10.1134/S1063776109010105
Примечания : Cited References: 25
Предметные рубрики: GROUND SPIN-STATE
PYROCHLORE ANTIFERROMAGNET
TRIANGULAR-LATTICE
CLASSICAL-THEORY
MODEL
TRANSITION
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--antiferromagnetism--free energy--magnetic devices--magnetic fields--magnetic structure--phase diagrams--vectors--antiferromagnet--antiferromagnetic--antiferromagnetic sublattices--comparative analysis--critical fields--external fields--field boundaries--first derivatives--first-order transitions--helical orderings--helical phase--helical structures--higher temperatures--incommensurate magnetic structures--isotropic exchanges--magnetic subsystems--magnetization jumps--mean-field approximations--minimum free energies--numerical minimizations--spatial displacements--temperature dependences--thermodynamic potentials--variational equations--wave vectors--phase transitions
Аннотация: The expansion of the thermodynamic potential for the two-subsystem antiferromagnet with frustrated intersubsystem isotropic exchange is obtained. It is demonstrated that this expansion contains the first derivatives with respect to the antiferromagnetic vectors of the subsystems, i.e., the Lifshitz invariant. The equation for the temperature-field boundary of the helical phase for the two-subsystem frustrated antiferromagnet is derived by linearizing the variational equations for the minimum free energy within the mean-field approximation. Relationships are obtained for the critical field at T = 0, the angle of canting of moments of the antiferromagnetic sublattices, and the temperature of spontaneous appearance of helical ordering in the absence of an external field. It is revealed that there is a second higher temperature of formation of the helical magnetic structure induced by the magnetic field with the wave vector of the helix nonmonotonically depending on the external field. The phase boundary of the helical phase and the temperature dependence of the orientation of moments of the magnetic subsystem with weak exchange interaction are determined using numerical minimization of the free energy. It is shown that the transition to the commensurate phase is a first-order transition with a small magnetization jump. A comparative analysis of models with different spatial displacements of ions in the subsystems along the direction of the vector of the helical structure is performed. A criterion is proposed for the choice of the direction of the vector of the incommensurate magnetic structure.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Incommensurate structures in a two-subsystem partially frustrated ferrimagnet
Место публикации : JETP Letters. - 2012. - Vol. 95, Is. 4. - P.188-192. - ISSN 0021-3640, DOI 10.1134/S0021364012040066
Примечания : Cited References: 23. - This work was supported by the Russian Foundation for Basic Research (project no. 10-02-00765).
Предметные рубрики: CLASSICAL-THEORY
MAGNETIC-FIELD
ANTIFERROMAGNET
CUB2O4
STATE
Аннотация: A new incommensurate magnetic structure with a locally triangular orientation of spins has been proposed for a two-subsystem magnet with frustrated intersystem exchange and competition between exchanges in one of the subsystems. When the temperature is lowered, this structure appears from the antiferromagnetic state after a first-order phase transition. It transfers to the Yafet-Kittel triangular structure when the threshold conditions for the exchange interactions are fulfilled. An increase in the length of the frustrated exchange bonds leads to the appearance of an incommensurate phase with the local antiferromagnetic orientation of the sublattices in each subsystem between the commensurate antiferromagnetic and Yafet-Kittel phases.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Symmetrical conical incommensurate structures of a frustrated isotropic Heisenberg ferrimagnet
Место публикации : JETP Letters. - 2015. - Vol. 102, Is. 2. - P.100-104. - ISSN 0021, DOI 10.1134/S0021364015140076. - ISSN 10906487(eISSN)
Примечания : Cited References:16
Предметные рубрики: CLASSICAL-THEORY
SPIN
MULTIFERROICS
Аннотация: The conditions of the appearance of conical incommensurate structures have been studied analytically for a ferrimagnet with the geometrically frustrated exchange between spins in different magnetic positions (subsystems) and the competition between exchanges in one of the subsystems. The phase transition temperatures to the conical states have been determined. The types of phase transitions have been determined by the numerical minimization of the free energy and (temperature-exchange parameters) phase diagrams have been obtained.
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