Quantum renormalizations in anisotropic multisublattice magnets and the modification of magnetic susceptibility under irradiation

Описание

Тип публикации: статья из журнала

Год издания: 2015

Идентификатор DOI: 10.1134/S1063776115110175

Ключевые слова: Anisotropy, Crystal orientation, Hamiltonians, Iron, Irradiation, Ising model, Magnetic susceptibility, Magnetism, Magnets, Metal ions, Quantum electronics, Single crystals, Spectrum analysis, Spin fluctuations, Transfer matrix method, Dispersion equations, Easy-axis anisotropy, Easy-plane anisotropy, Elementary excitations, One-dimensional magnets, Optical irradiation, Statistical ensembles, Transformation techniques, Ions

Аннотация: The dispersion equation of a strongly anisotropic one-dimensional magnet catena-[Fe-II(ClO4)(2){Fe-III(bpca)(2)}]ClO4 containing alternating high-spin (HS) (S = 2) and low-spin (LS) (S = 1/2) iron ions is obtained by the diagram technique for Hubbard operators. The analysis of this equation yields six branches in the excitation speПоказать полностьюctrum of this magnet. It is important that the crystal field for ions with spin S = 2 is described by the Hamiltonian of single-ion easy-plane anisotropy, whose orientation is changed by 90A degrees when passing from one HS iron ion to another. The U(N) transformation technique in the atomic representation is applied to diagonalize a single-ion Hamiltonian with a large number of levels. It is shown that the modulation of the orientation of easy magnetization planes leads to a model of a ferrimagnet with easy-axis anisotropy and to the formation of energy spectrum with a large gap. For HS iron ions, a decrease in the mean value of the spin projection due to quantum fluctuations is calculated. The analysis of the specific features of the spectrum of elementary excitations allows one to establish a correspondence to a generalized Ising model for which the magnetic susceptibility is calculated in a wide range of temperatures by the transfer-matrix method. The introduction of a statistical ensemble that takes into account the presence of chains of different lengths and the presence of iron ions with different spins allows one to describe the experimentally observed modification of the magnetic susceptibility of the magnet under optical irradiation.

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Издание

Журнал: JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS

Выпуск журнала: Vol. 121, Is. 5

Номера страниц: 860-877

ISSN журнала: 10637761

Место издания: NEW YORK

Издатель: MAIK NAUKA/INTERPERIODICA/SPRINGER

Авторы

  • Val'kov V.V. (Kirenskii Institute of Physics,Siberian Branch,Russian Academy of Sciences,Akademgorodok)
  • Shustin M.S. (Siberian Federal University)

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