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.
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