Dyson-Maleev theory of an X X Z ferrimagnetic spin chain with single-ion anisotropy

We use the mean-field approximation of Dyson-Maleev representation to study an XXZ Heisenberg ferrimagnetic spin chain with single-ion anisotropy. By solving the self-consistent equations with different anisotropies, λ and D respectively, the energy spectrums, internal energy, static susceptibility and specific heat are calculated. Especially, the quantum phase transition of the magnetization plateau induced by single-ion anisotropy D is obtained in the model of the ferrimagnetic spin chain by using Dyson-Maleev mean-field theory.