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/ R. S. Gekht, I. N. Bondarenko // J. Exp. Theor. Phys. - 2005. - Vol. 101, Is. 5. - P. 868-880, DOI 10.1134/1.2149066. - Cited References: 43 . - ISSN 1063-7761РУБ Physics, Multidisciplinary

Аннотация: The possibility of implementing a quantum-spin-liquid-type state in a two-layer triangular spin-1/2 antiferromagnet at T = 0 is investigated. The ratio of intra- to interlayer exchange constants (j) is found under which a transition from the classical state with 120 degrees triangular order to a quantum state with zero magnetization per site occurs; in this case, the spins of adjacent layers form singlets that are separated from triplet excitations by an energy gap. Compared with an analogous system with the square lattice, the range of j in which the classical ordered state is realized turns out to be an order of magnitude smaller due to the effects of frustration; in this case, the behavior of thermodynamic quantities is analogous, on the whole, to that in two-layer square lattices; a difference manifests itself in the behavior of the gap in the spectrum of quasiparticles in an external magnetic field h. For small fields h, a j-h phase diagram is constructed that determines the domains in which the 120 degrees and the singlet phases exist. It is established that, in the neighborhood of the second-order phase transition, the contribution, to the thermodynamic quantities, of longitudinal spin fluctuations, which are disregarded in the spin-wave description, is comparable to the contribution of transverse fluctuations. (c) 2005 Pleiades Publishing, Inc.

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

Доп.точки доступа:
Bondarenko, I. N.

/ R. S. Gekht, I. N. Bondarenko // J. Exp. Theor. Phys. - 1998. - Vol. 86, Is. 6. - P. 1209-1215, DOI 10.1134/1.558592. - Cited References: 23 . - ISSN 1063-7761РУБ Physics, Multidisciplinary

Аннотация: We study the process of magnetic ordering in planar antiferromagnetic systems with a Kagome lattice. It is found that if the interaction between next-nearest-neighbor spins is taken into account, the heat capacity of such systems has a singularity at a finite temperature T. On the basis of a scaling analysis of finite-size systems we study the behavior of thermodynamic quantities in the neighborhood of a phase transition. We find that the phase transition at the critical point is due to discrete- and continuous-symmetry breaking, in which the long-range chiral order and the power-law translational spin order emerge simultaneously. Finally, we calculate the temperatures of the transition to different (with three and nine spins per unit cell) ordered states. (C) 1998 American Institute of Physics.

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
ИФ СО РАН

Доп.точки доступа:
Bondarenko, I. N.

/ I. N. Bondarenko, R. S. Gekht, V. I. Ponomarev // Phys. Lett. A. - 1996. - Vol. 222, Is. 4. - P. 269-274, DOI 10.1016/0375-9601(96)00635-4. - Cited References: 22 . - ISSN 0375-9601РУБ Physics, Multidisciplinary

Аннотация: Magnetic states and phase transitions of the layered triangular antiferromagnets in an applied field are studied. It is shown that in compounds like VBr2 and VCl2 quantum effects change the ground state structure and cause successive phase transitions as the magnetic field increases. Coplanar structures of different spin configuration are realized far from the saturation field and a noncoplanar structure of umbrella-type configuration is realized near this field. The ground-state phase diagram is constructed, and a finite region of fields where the collinear phase is also possible is indicated.

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Держатели документа:
Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russian Federation

Доп.точки доступа:
Gekht, R. S.; Ponomarev, V. I.