Effects of the single-ion-type anisotropy on the spin-1 Haldane system with a [formula omitted] impurity

Abstract

The effects of the single-ion-type anisotropy, including both of the so-called D-term and E-term, on the spin-1 Haldane system with a spin- 1 2 impurity is studied by means of an analytical method in terms of spin- 1 2 degrees of freedom at the sites neighboring the impurity spin. The equivalence between a phenomenological Hamiltonian of three coupled spin- 1 2 spins representing the spin- 1 2 degrees of freedom and a more realistic Hamiltonian is examined. It is shown that, when the coupling between the impurity and host spins is sufficiently weak, the two Hamiltonians give the equivalent energy versus magnetic-field diagram. We determine the correspondence between the interaction constants in the phenomenological Hamiltonian and those in the realistic Hamiltonian.