Dyson-Maleev theory of ferrimagnetic spin chain with bond alternation in longitudinal magnetic field.

By using the method of Dyson–Maleev mean-field theory, we study the effect of bond alternation and longitudinal magnetic field in the model of ferrimagnetic spin chain. Based on the numerical results of self-consistent equations, properties of the excited spectrums, magnon internal energy, static susceptibility, magnetization plateau and specific heat are obtained with different bond alternation parameters δ and external magnetic field B. This method provides qualitative consistent results to describe the phase from ferrimagnetic state to bond altered state. • The transition from ferrimagnetic to dimer state can be described by Dyson-Maleev theory. • The quantum magnetization plateau of mixed spin chain can be tuned by bond alternation parameter. • The result of Dyson-Maleev theory is qualitatively consistent with other numerical method. [ABSTRACT FROM AUTHOR]