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

The dispersion equation of a strongly anisotropic one-dimensional magnet catena-[Fe{sup II}(ClO{sub 4}){sub 2}(Fe{sup III}(bpca){sub 2})]ClO{sub 4} 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 spectrum 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 90° 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 amore » 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.« less
Authors:
;  [1]
  1. Russian Academy of Sciences, Akademgorodok, Kirenskii Institute of Physics, Siberian Branch (Russian Federation)
Publication Date:
OSTI Identifier:
22471996
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 121; Journal Issue: 5; Other Information: Copyright (c) 2015 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHLORATES; CRYSTAL FIELD; DIAGRAMS; ENERGY SPECTRA; EXCITATION; FERRIMAGNETIC MATERIALS; FLUCTUATIONS; HAMILTONIANS; IRON COMPOUNDS; IRON IONS; IRRADIATION; ISING MODEL; MAGNETIC SUSCEPTIBILITY; MAGNETIZATION; MAGNETS; ORGANIC COMPOUNDS; RENORMALIZATION; SPIN; TRANSFER MATRIX METHOD